Skin function depends on a meticulously regulated dynamic interaction of distinct skin compartments such as the epidermis and dermis. Adaptive responses at the molecular and cellular level are essential for these interactions - and if dysregulated - drive skin aging and other pathologies. After defining the role of redox homeodynamics in physiology and aging pathology, we focus on the redox distress-dependent aging of dermal fibroblasts including their progenitors. We here discuss the prime role of senescent fibroblasts in the control of their own endogenous niche and stem cell niches for epidermal stem cells, hair follicle stem cells, adipocyte precursors and muscle stem cells. We here review that redox imbalance induced reduction in Insulin-like Growth Factor-1 drives skin aging by the depletion of stem cell pools. This IGF-1 reduction is mediated via the redox-sensitive transcription factor JunB and also by the redox-dependent changes in sphingolipid-metabolism, among others. In addition, we will discuss the changes in the extracellular matrix of the skin affecting cellular senescence and the skin integrity and function in aging. The aim is a deeper understanding of the two main redox-dependent hubs such as JunB-induced depletion of IGF-1, and the sphingolipid-mediated remodeling of the cell membrane with its impact on IGF-1, fibroblast heterogeneity, function, senescence and plasticity in skin aging.

Originally known for its function in the cell cycle, the anaphase-promoting complex/cyclosome (APC/C) also plays a crucial role in regulating differentiation and maintaining cell identity. However, the mechanisms by which APC/C mediates developmental processes are not fully understood. In this study, we show that APC/C and its activator FZR-1 regulate the chromatin regulators MES-4 and MES-3. These proteins are part of histone methylation complexes essential for maintaining germline stem cell (GSC) identity in the germ line of Caenorhabditis elegans. APC/CFZR-1 facilitates the degradation of MES-4 and MES-3 when GSCs transition toward differentiating into oocytes. The activity of APC/CFZR-1 is restricted by the Notch signaling pathway provided by the distal tip cell, which is responsible for maintaining the stemness of the GSC pool. This negative regulation enables the accumulation of MES-3 and MES-4 in GSCs, offering an additional component by which niche activity modulates the C. elegans germ line.

Cellular communication is a cornerstone of metazoan development, orchestrating cell behavior, differentiation, and tissue formation. Morphogens, key signaling molecules for patterning tissue architecture, are traditionally thought to act through diffusion or endocytosis but struggle to explain precise long-range gradient formation in complex tissues. The discovery of cytonemes, specialized actin-based membrane extensions, has introduced a novel mechanism for direct intercellular signaling. Their dynamic structure allows for long-range signaling, ensuring specificity and accuracy in morphogen delivery, which is essential for proper tissue patterning and cell differentiation. In this review, we summarize the latest advances of cytoneme research across different model organisms by focusing on the regulatory mechanisms and functional roles in stem cells and developmental disorders. We establish cytonemes as fundamental mediators of intercellular communication and emphasize their pivotal roles in developmental biology and potential implications in regenerative medicine and cancer therapy.

Hematopoietic stem and progenitor cells (HSPCs) can migrate and reside within the bone marrow in distinct microenvironments or niches. The niches organize around specific stromal cells, such as endothelial cells at the capillary or sinusoid walls, and osteoblasts along the bone matrix. Within each niche, a specific combination of external cues, including secreted and diffusible factors, cell-matrix, and cell-cell interactions, controls HSPCs behavior and fate. Deciphering the interplay between HSPCs and stromal cells of the niches is challenging: in vivo, it is hindered by the opacity of the bone matrix; in vitro, classical co-culture models only poorly recapitulate essential features of the physiological niches. The difficulty is moreover amplified by the exceptional migration capacity of HSPCs.In this chapter, we present a method to overcome these limitations by producing arrays of microwells designed to mimic bone marrow niches in a functional manner. These "microniches" promote a long-term interaction between the HSPC and a stromal cell of interest. We describe their microfabrication based on a maskless photolithography method allowing the production of arrays of microwells with reproducible volume and geometry, and the iterative improvement of the geometric design of the wells. We describe the loading and culture of stromal cells with HSPCs. We discuss the potentiality of microwells, in basic and applied research, as a platform to investigate molecular mechanisms involved in direct cell-cell interactions and local effects of diffusible factors, for any adherent and non-adherent cells of interest.

Cellular motion is a key feature of tissue morphogenesis and is often driven by migration. However, migration need not explain cell motion in contexts where there is little free space or no obvious substrate, such as those found during organogenesis of mesenchymal organs including the embryonic skull. Through ex vivo imaging, biophysical modeling, and perturbation experiments, we find that mechanical feedback between cell fate and stiffness drives bone expansion and controls bone size in vivo. This mechanical feedback system is sufficient to propagate a wave of differentiation that establishes a collagen gradient which we find sufficient to describe patterns of osteoblast motion. Our work provides a mechanism for coordinated motion that may not rely upon cell migration but on emergent properties of the mesenchymal collective. Identification of such alternative mechanisms of mechanochemical coupling between differentiation and morphogenesis will help in understanding how directed cellular motility arises in complex environments with inhomogeneous material properties.

Skin is the largest organ of the human body and undergoes both intrinsic (chronological) and extrinsic aging. While intrinsic skin aging is driven by genetic and epigenetic factors, extrinsic aging is mediated by external threats such as UV irradiation or fine particular matters, the sum of which is referred to as exposome. The clinical manifestations and biochemical changes are different between intrinsic and extrinsic skin aging, albeit overlapping features exist, eg, increased generation of reactive oxygen species, extracellular matrix degradation, telomere shortening, increased lipid peroxidation, or DNA damage. As skin is a prominent target for many hormones, the molecular and biochemical processes underlying intrinsic and extrinsic skin aging are under tight control of classical neuroendocrine axes. However, skin is also an endocrine organ itself, including the hair follicle, a fully functional neuroendocrine "miniorgan." Here we review pivotal hormones controlling human skin aging focusing on IGF-1, a key fibroblast-derived orchestrator of skin aging, of GH, estrogens, retinoids, and melatonin. The emerging roles of additional endocrine players, ie, α-melanocyte-stimulating hormone, a central player of the hypothalamic-pituitary-adrenal axis; members of the hypothalamic-pituitary-thyroid axis; oxytocin, endocannabinoids, and peroxisome proliferator-activated receptor modulators, are also reviewed. Until now, only a limited number of these hormones, mainly topical retinoids and estrogens, have found their way into clinical practice as anti-skin aging compounds. Further research into the biological properties of endocrine players or its derivatives may offer the development of novel senotherapeutics for the treatment and prevention of skin aging.

Androgenetic alopecia (AGA) is the most common cause of hair loss globally, affecting millions of people, particularly men. Current treatments include FDA-approved drugs and devices, but many patients experience side effects or suboptimal results. The niostem device is a new, wearable device that delivers low-level electrical stimulation to promote hair growth. This pilot study aims to evaluate the efficacy and safety of the niostem device in male AGA patients.

A total of 21 male patients with AGA used the niostem device daily for 30 min over 6 months. Participants had not used any anti-hair loss products within the 6 months preceding the start of the study. Hair density, thickness, and terminal hair counts were assessed at baseline, 3 months, and 6 months using trichoscopic measurements. Patient-reported outcomes were recorded, and adverse events were monitored.

The niostem device resulted in significant increases in hair count, with a 12% increase in total hair density at 3 months and a 19.3% increase at 6 months. Hair thickness also increased by 8.8% in 6 months. Terminal hair density improved significantly over time, with visible hair growth observed in the participants. No adverse events were reported.

The niostem device demonstrated a significant increase in hair density and hair thickness in male AGA patients, with no adverse effects. Further large-scale studies are warranted.

Sphingolipids serve as building blocks of membranes to ensure subcellular compartmentalization and facilitate intercellular communication. How cell type-specific lipid compositions are achieved and what is their functional significance in tissue morphogenesis and maintenance has remained unclear. Here, we identify a stem cell-specific role for ceramide synthase 4 (CerS4) in orchestrating fate decisions in skin epidermis. Deletion of CerS4 prevents the proper development of the adult hair follicle bulge stem cell (HFSC) compartment due to altered differentiation trajectories. Mechanistically, HFSC differentiation defects arise from an imbalance of key ceramides and their derivate sphingolipids, resulting in hyperactivation of noncanonical Wnt signaling. This impaired HFSC compartment establishment leads to disruption of hair follicle architecture and skin barrier function, ultimately triggering a T helper cell 2-dominated immune infiltration resembling human atopic dermatitis. This work uncovers a fundamental role for a cell state-specific sphingolipid profile in stem cell homeostasis and in maintaining an intact skin barrier.

Breast cancer stem cells are a promising therapeutic target in cancer. We explored breast cancer stem cell diversity and establish a methodology for selectively culturing breast cancer stem cells. We collected breast cancer tissues from surgical samples of treatment-naïve patients with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer. Following isolation, cells were subjected to spheroid culture on non-adherent plates. Of the 57 cases, successful culture was achieved in 48 cases, among which the average ratio of CD44+/CD24- breast cancer cells increased from 13.8% in primary tumors to 61.6% in spheroids. A modest number of spheroid cells successfully engrafted in mice and subsequently re-differentiated within the murine environment, confirming their stemness. ER expression in spheroid cells exhibited negative conversion in 52.1% of cases. The proportion of Twist-, Snail-, and Vimentin-positive cells increased from 43.8%, 12.9%, and 7.7-75.0%, 58.1%, and 37.7%, respectively. ER-positive, HER2-negative breast cancer stem cells were classified into two groups using DNA microarrays. Gene Ontology analysis unveiled higher expression of immune response-related genes in one group and protein binding-associated genes in the other. We demonstrated stable and selective culture of breast cancer stem cells from patient-derived breast cancer tissue using spheroid cultures.

Controlled signaling activity is vital for normal tissue homeostasis and oncogenic signaling activation facilitates tumorigenesis. Here we use single-cell transcriptomics to investigate the effects of pro-proliferative signaling on epithelial homeostasis using the Drosophila follicle cell lineage. Notably, EGFR-Ras overactivation induces cell cycle defects by activating the transcription factors Pointed and E2f1 and impedes differentiation. Hh signaling simultaneously promotes an undifferentiated state and induces differentiation via activation of EMT-associated transcription factors zfh1 and Mef2. As a result, overactivation of Hh signaling generates a transcriptional hybrid state comparable to epithelial-mesenchymal-transition. Co-overactivation of Hh signaling with EGFR-Ras signaling blocks differentiation and induces key characteristics of tumor cells including a loss of tissue architecture caused by reduced expression of cell adhesion molecules, sustained proliferation and an evasion of cell cycle checkpoints. These findings provide new insight into how non-interacting signaling pathways converge at the transcriptional level to prevent malignant cell behavior.

This paper evaluates recent work purporting to show that the "agency" of organisms is an important phenomenon for evolutionary biology to study. Biological agency is understood as the capacity for goal-directed, self-determining activity-a capacity that is present in all organisms irrespective of their complexity and whether or not they have a nervous system. Proponents of the "agency perspective" on biological systems have claimed that agency is not explainable by physiological or developmental mechanisms, or by adaptation via natural selection. We show that this idea is theoretically unsound and unsupported by current biology. There is no empirical evidence that the agency perspective has the potential to advance experimental research in the life sciences. Instead, the phenomena that the agency perspective purports to make sense of are better explained using the well-established idea that complex multiscale feedback mechanisms evolve through natural selection.

Stem cell-based therapies are emerging as significant approaches in tissue engineering and regenerative medicine, applicable to both fundamental scientific research and clinical practice. Despite remarkable results in clinical studies, challenges such as poor standardization of graft tissues, limited sources, and reduced functionality have hindered the effectiveness of these therapies. In this review, we summarize the engineering approaches involved in fabricating stem cell assisted patches and the substantial strategies for designing stem cell-laden engineered patches (SCP) to complement the existing stem cell-based therapies. We then outline the potential applications of SCP in advancing tissue regeneration and regenerative medicine. By combining living stem cells with engineered patches, SCP can enhance the functions of both components, particularly for tissue engineering applications. Finally, we addressed current challenges, such as ethical considerations, high costs, and regulatory hurdles and proposed future research directions to overcome these barriers.

Organoids are three-dimensional models of microscopic organisms created through the self-organization of various types of stem cells. They are widely unitized in personalized medicine due to their capacity to replicate the structure and functionality of native organs. Meanwhile, nanotechnology has been integrated into diagnostic and therapeutic tools to manage an array of medical conditions, given its unique characteristics of nanoscale. Nanomaterials have demonstrated potential in developing innovative and effective organoids. With a focus on studying the interaction of nanomaterials and organoid technology in personalized medicine, this Review examines the role of nanomaterials in regulating the fate of stem cells to construct different types of organoids. It also explores the potential of nanotechnology to create 3D microenvironments for organoids. Finally, perspectives and challenges of applying nanotechnology for organoids development toward the translation of personalized medicine are discussed.

The field of tissue engineering has witnessed significant advancements with the advent of hydrogel nanocomposites (HNC), emerging as a highly promising platform for regenerative medicine. HNCs provide a versatile platform that significantly enhances the differentiation of stem cells into specific cell lineages, making them highly suitable for tissue engineering applications. By incorporating nanoparticles, the mechanical properties of hydrogels, such as elasticity, porosity, and stiffness, are improved, addressing common challenges such as short-term stability, cytotoxicity, and scalability. These nanocomposites also exhibit enhanced biocompatibility and bioavailability, which are crucial to their effectiveness in clinical applications. Furthermore, HNCs are responsive to various triggers, allowing for precise control over their chemical properties, which is beneficial in creating 3D microenvironments, promoting wound healing, and enabling controlled drug delivery systems. This review provides a comprehensive overview of the production methods of HNCs and the factors influencing their physicochemical and biological properties, particularly in relation to stem cell differentiation and tissue repair. Additionally, it discusses the challenges in developing HNCs and highlights their potential to transform the field of regenerative medicine through improved mechanotransduction and controlled release systems.

Intricate microenvironment signals orchestrate to affect cell behavior and fate during tissue morphogenesis. However, the underlying mechanisms on how specific local niche signals influence cell behavior and fate are not fully understood, owing to the lack of in vitro platform able to precisely, quantitatively, spatially, and independently manipulate individual niche signals. Here, microarrays of protein-based 3D single cell micro-niche (3D-SCμN), with precisely engineered biophysical and biochemical niche signals, are micro-printed by a multiphoton microfabrication and micropatterning technology. Mouse embryonic stem cell (mESC) is used as the model cell to study how local niche signals affect stem cell behavior and fate. By precisely engineering the internal microstructures of the 3D SCμNs, we demonstrate that the cell division direction can be controlled by the biophysical niche signals, in a cell shape-independent manner. After confining the cell division direction to a dominating axis, single mESCs are exposed to asymmetric biochemical niche signals, specifically, cell-cell adhesion molecule on one side and extracellular matrix on the other side. We demonstrate that, symmetry-breaking (asymmetric) niche signals successfully trigger cell polarity formation and bias the orientation of asymmetric cell division, the mitosis process resulting in two daughter cells with differential fates, in mESCs.

Stem cells perceive and respond to biochemical and physical signals to maintain homeostasis. Yet, it remains unclear how stem cells sense mechanical signals from their niche in vivo. In this work, we investigated the roles of PIEZO mechanosensitive channels in the intestinal stem cell (ISC) niche. We used mouse genetics and single-cell RNA sequencing analysis to assess the requirement for PIEZO channels in ISC maintenance. In vivo measurement of basement membrane stiffness showed that ISCs reside in a more rigid microenvironment at the bottom of the crypt. Three-dimensional and two-dimensional organoid systems combined with bioengineered substrates and a stretching device revealed that PIEZO channels sense extracellular mechanical stimuli to modulate ISC function. This study delineates the mechanistic cascade of PIEZO activation that coordinates ISC fate decision and maintenance.

Osteoarthritis (OA) is a prevalent musculoskeletal disease affecting middle-aged and elderly individuals, with knee pain as a common complaint. Standard therapy approaches generally attempt to alleviate pain and inflammation, using various pharmacological and non-pharmacological options. However, the efficacy of these therapies in long-term tissue repair remains debated. As an alternative, regenerative medicine offers a promising strategy, with decreased adverse event rates and increasing evidence of safety and efficacy. This review will outline current advances in regenerative medicine for knee OA, emphasizing outpatient clinic-based therapies that use orthobiological and non-biological products. Different strategies based on orthobiologics are discussed as potential regenerative options for the management of knee OA. Cell-free therapies including platelet-rich plasma, autologous anti-inflammatories, exosomes, human placenta extract, and mitochondrial transplantation are discussed, focusing on their potential for cartilage regeneration. Additionally, cell-based therapies with regenerative properties including bone marrow aspirate concentrate, adipose stromal vascular fraction, microfat, nanofat, stem cell therapy, and genetically modified cells as part of orthobiologics, are being investigated. Also, this study is looking into non-biological approaches such as using gold-induced cytokines, extracorporeal shockwave therapy, and ozone therapy. The mechanisms of action, effectiveness, and clinical applications of each therapy are being explored, providing insights into their role in the management of knee OA.

A tendon's ordered extracellular matrix (ECM) is essential for transmitting force but is also highly prone to injury. How tendon cells embedded within and surrounding this dense ECM orchestrate healing is not well understood. Here, we identify a specialized quiescent Scx+/Axin2+ population in mouse and human tendons that initiates healing and is a major functional contributor to repair. Axin2+ cells express stem cell markers, expand in vitro, and have multilineage differentiation potential. Following tendon injury, Axin2+-descendants infiltrate the injury site, proliferate, and differentiate into tenocytes. Transplantation assays of Axin2-labeled cells into injured tendons reveal their dual capacity to significantly proliferate and differentiate yet retain their Axin2+ identity. Specific loss of Wnt secretion in Axin2+ or Scx+ cells disrupts their ability to respond to injury, severely compromising healing. Our work highlights an unusual paradigm, wherein specialized Axin2+/Scx+ cells rely on self-regulation to maintain their identity as key organizers of tissue healing.

The transition of stem cells from a quiescent state to an active state is a finely tuned process that requires the dismantling of the quiescence program and the establishment of a cell cycle-promoting transcriptional landscape. Whether epigenetic processes control stem cell states to promote the regeneration of adult tissues remains elusive. In this study, we show that a repressive histone modification, H2AK119ub, is dynamic between quiescent and active hair follicle stem cells (HFSCs) in the adult murine skin. Ablation of H2AK119ub in HFSCs leads to impaired quiescence leading to premature activation and an eventual exhaustion of HFSC pool. Transcriptional and chromatin studies revealed that H2AK119ub directly represses a proliferation promoting transcriptional program in the HFSCs to preserve quiescence. Lastly, we identify that the inhibitory FGF signaling produced by the hair follicle niche keratinocytes maintains H2AK119ub in quiescent HFSCs. Together, these findings reveal that a repressive histone mark, H2AK119ub, is under the dynamic regulation of inhibitory niche signaling to prevent the untimely establishment of an activated state to preserve SC function and longevity.

Osteoarthritis (OA) induced microenvironmental alterations are a common and unavoidable phenomenon that greatly exacerbate the pathologic process of OA. Imbalances in the synthesis and degradation of cartilage extracellular matrix (ECM) have been reported to be associated with an adverse microenvironment. Stem cell therapy is a promising treatment for OA, and mesenchymal stem cells (MSCs) are the main cell sources for this therapy. With multispectral differentiation and immunomodulation, MSCs can effectively regulate the microenvironment of articular cartilage, ameliorate inflammation, promote regeneration of damaged cartilage, and ultimately alleviate OA symptoms. However, the efficacy of MSCs in the treatment of OA is greatly influenced by articular cavity microenvironments. This article reviews the five microenvironments of OA articular cavity, including inflammatory microenvironment, senescence microenvironment, hypoxic microenvironment, high glucose microenvironment and high lipid environment, focus on the positive and negative effects of OA microenvironments on the fate of MSCs. In this regard, we emphasize the mechanisms of the current use of MSCs in OA treatment, as well as its limitations and challenges.

Diabetes mellitus is induced by quantitative and qualitative decline in pancreatic β cells. Although its radical therapy has not yet been established, β cell regeneration is a promising option. We investigate here two mouse models of β cell regeneration induced after ∼80% reduction in β cell number: Cre/loxP-mediated β cell ablation and partial pancreatectomy. Cre/loxP-mediated, mosaic-pattern of β cell ablation by diphtheria toxin (DT) prompted rapid β cell replenishment through repeated proliferation of rare, highly proliferative DT receptor-negative β cells along with increase in Hes1, Neurog3, Ascl1, and Aldh1a3 (immature/dedifferentiated β cell markers) and decrease in Mafa (a mature β cell marker) in the islets. In contrast, pancreatectomy also prompted active proliferation, but with no change in these immature/dedifferentiated or mature β cell markers. Our findings demonstrate that the mode of β cell regeneration differs between Cre/loxP-mediated β cell ablation and surgical β cell reduction, and the former involves β cell dedifferentiation followed by active repetitive cell proliferation of a small population of β cells.

Spermatogonial stem cells (SSCs) play a crucial role in the male reproductive system, responsible for maintaining continuous spermatogenesis. The microenvironment or niche of SSCs is a key factor in regulating their self-renewal, differentiation and spermatogenesis. This microenvironment consists of multiple cell types, extracellular matrix, growth factors, hormones and other molecular signals that interact to form a complex regulatory network. This review aims to provide an overview of the main components of the SSCs microenvironment, explore how they regulate the fate decisions of SSCs, and discuss the potential impact of microenvironmental abnormalities on male reproductive health.

Ageing and fertility are intertwined. Germline loss extends the lifespan in various organisms, termed gonadal longevity. However, the original longevity signal from the somatic gonad remains poorly understood. Here, we focused on the interaction between germline stem cells (GSCs) and their niche, the distal tip cells (DTCs), to explore the barely known longevity signal from the somatic gonad in C. elegans. We found that removing germline disrupts the cell adhesions between GSC and DTC, causing a significant transcriptomic change in DTC through hmp-2/β-catenin and two GATA transcription factors, elt-3 and pqm-1 in this niche cell. Inhibiting elt-3 and pqm-1 in DTC suppresses gonadal longevity. Moreover, we further identified the TGF-β ligand, tig-2, as the cytokine from DTC upon the loss of germline, which evokes the downstream gonadal longevity signalling throughout the body. Our findings thus reveal the source of the longevity signalling in response to germline removal, highlighting the stem cell niche as a critical signalling hub in ageing.

Renal development is a complex process in which two major processes, tubular branching and nephron development, regulate each other reciprocally. Our previous findings have indicated that collagen XVIII (ColXVIII), an extracellular matrix protein, affects the renal branching morphogenesis. We investigate here the role of ColXVIII in nephron formation and the behavior of nephron progenitor cells (NPCs) using isoform-specific ColXVIII knockout mice. The results show that the short ColXVIII isoform predominates in the early epithelialized nephron structures whereas the two longer isoforms are expressed only in the later phases of glomerular formation. Meanwhile, electron microscopy showed that the ColXVIII mutant embryonic kidneys have ultrastructural defects at least from embryonic day 16.5 onwards. Similar structural defects had previously been observed in adult ColXVIII-deficient mice, indicating a congenital origin. The lack of ColXVIII led to a reduced NPC population in which changes in NPC proliferation and maintenance and in macrophage influx were perceived to play a role. The changes in NPC behavior in turn led to notably reduced overall nephron formation. In conclusion, the results show that ColXVIII has multiple roles in renal development, both in ureteric branching and in NPC behavior.

Endometrial stem/progenitor cells are a type of stem cells with the ability to self-renew and differentiate into multiple cell types. They exist in the endometrium and form niches with their neighbor cells and extracellular matrix. The interaction between endometrial stem/progenitor cells and niches plays an important role in maintaining, repairing, and regenerating the endometrial structure and function. This review will discuss the characteristics and functions of endometrial stem/progenitor cells and their niches, the mechanisms of their interaction, and their roles in endometrial regeneration and diseases. Finally, the prospects for their applications will also be explored.

Stem cells possess the ability to differentiate into different lineages and the ability to self-renew, thus representing an excellent tool for regenerative medicine. They can be isolated from different tissues, including the adipose tissue. Adipose tissue and human adipose-derived stem cells (hADSCs) are privileged candidates for regenerative medicine procedures or other plastic reconstructive surgeries. The cellular environment is able to influence the fate of stem cells residing in the tissue. In a previous study, we exposed hADSCs to an exhausted medium of a breast cancer cell line (MCF-7) recovered at different days (4, 7, and 10 days). In the same paper, we inferred that the medium was able to influence the behaviour of stem cells. Considering these results, in the present study, we evaluated the expression of the major genes related to adipogenic and osteogenic differentiation. To confirm the gene expression data, oil red and alizarin red colorimetric assays were performed. Lastly, we evaluated the expression of miRNAs influencing the differentiation process and the proliferation rate, maintaining a proliferative state. The data obtained confirmed that cells exposed to the medium maintained a stem and proliferative state that could lead to a risky proliferative phenotype.

Regeneration is a multifaceted biological phenomenon that necessitates the intricate orchestration of apoptosis, stem cells, and immune responses, culminating in the regulation of apoptosis-induced compensatory proliferation (AICP). The AICP context of research is observed in many animal models like in Hydra, Xenopus, newt, Drosophila, and mouse but so far not reported in earthworm. The earthworm Perionyx excavatus is used in the present study to understand the relationship between AICP-related protein expression and regeneration success in different conditions (normal regeneration and abnormal multiple bud formation). Initially, the worms are amputated into five equal portions and it is revealed that regeneration in P. excavatus is clitellum independent and it gives more preference for anterior regeneration (regrowth of head portion) than for posterior regeneration (regrowth of tail portion). The posterior segments of the worm possess enormous regeneration ability but this is lacking in anterior segments. Alkaline phosphate, a stem cell marker, shows strong signals throughout all the posterior segments but it decreases in the initial 1st to 15th anterior segments which lack the regeneration ability. While regenerating normally, it was suggested that the worm follow AICP principles. This is because there was increased expression of apoptosis signals throughout the regeneration process along with constant expression of stem cell proliferation response together with cellular proliferation. In amputated posterior segments maintained in vitro, the apoptosis signals were extensively detected on the 1st day. However, on the 4th and 6th days, caspase-3 and H2AX expression are significantly suppressed, which may eventually alter the Wnt3a and histone H3 patterns that impair the AICP and result in multiple bud formation. Our results suggest that AICP-related protein expression pattern is crucial for initiating proper regeneration.

Bone marrow-derived mesenchymal stem cells (BMSCs) have been recognized as new candidates for the treatment of serious endometrial injuries. However, owing to the local microenvironment of damaged endometrium, transplantation of BMSCs yielded disappointing results. In this study, Pectin-Pluronic® F-127 hydrogel as scaffolds were fabricated to provide three-dimensional architecture for the attachment, growth, and migration of BMSCs. E2 was encapsulated into the W/O/W microspheres to construct pectin-based E2-loaded microcapsules (E2 MPs), which has the potential to serve as a long-term reliable source of E2 for endometrial regeneration. Then, the BMSCs/E2 MPs/scaffolds system was injected into the uterine cavity of mouse endometrial injury model for treatment. At 4 weeks after transplantation, the system increased proliferative abilities of uterine endometrial cells, facilitated microvasculature regeneration, and restored the ability of endometrium to receive an embryo, suggesting that the BMSCs/E2 MPs/scaffolds system is a promising treatment option for endometrial regeneration. Furthermore, the mechanism of E2 in promoting the repair of endometrial injury was also investigated. Exosomes are critical paracrine mediators that act as biochemical cues to direct stem cell differentiation. In this study, it was found that the expression of endometrial epithelial cell (EEC) markers was upregulated in BMSCs treated by exosomes secreted from endometrial stromal cells (ESCs-Exos). Exosomes derived from E2-stimulated ESCs further promoted the expression level of EECs markers in BMSCs, suggesting exosomes released from ESCs by E2 stimulation could enhance the differentiation efficiency of BMSCs. Therefore, exosomes derived from ESCs play paracrine roles in endometrial regeneration stimulated by E2 and provide optimal estrogenic response.

Stem cell therapy offers a promising avenue for advanced liver disease cases as an alternative to liver transplantation. Clinical studies are underway to explore the potential of stem cells from various sources in treating different liver diseases. However, due to the variability among current studies, further validation is needed to ensure the safety and effectiveness of stem cell therapy. To establish a strong foundation for optimal stem cell therapy applications, selection of suitable stem cell sources, standardization of transplantation protocols, and patient criteria are vital. This review comprehensively examines existing literature on stem cell sources, transplantation methods, and patient selection. Additionally, we discuss novel strategies, including stem cell preconditioning, cell-free therapy, genetic modification of stem cells, and the use of liver organoids, addressing the limitations of current stem cell therapies. Nevertheless, these innovative approaches require further validation.

In patients with severe acute respiratory distress syndrome (ARDS) associated with sepsis, lung recovery is considerably delayed, and mortality is much high. More insight into the process of lung regeneration in ARDS patients is needed. Exosomes are important cargos for intercellular communication by serving as autocrine and/or paracrine. Cutting-edge exomics (exosomal proteomics) makes it possible to study the mechanisms of re-alveolarization in ARDS lungs.

This study aimed to identify potential regenerative niches by characterizing differentially expressed proteins in the exosomes of bronchioalveolar lavage (BAL) in ARDS patients.

We purified exosomes from BAL samples collected from ARDS patients by NIH-supported ALTA and SPIROMICS trials. The abundance of exosomal proteins/peptides was quantified using liquid chromatography-mass spectrometry (LC-MS). Differentially expressed exosomal proteins between healthy controls and ARDS patients were profiled for functional annotations, cell origins, signaling pathways, networks, and clinical correlations.

Our results show that more exosomal proteins were identified in the lungs of late-stage ARDS patients. Immune cells and lung epithelial stem cells were major contributors to BAL exosomes in addition to those from other organs. We enriched a wide range of functions, stem cell signals, growth factors, and immune niches in both mild and severe patients. The differentially expressed proteins that we identified were associated with key clinical variables. The severity-associated differences in protein-protein interaction, RNA crosstalk, and epigenetic network were observed between mild and severe groups. Moreover, alveolar type 2 epithelial cells could serve as both exosome donors and recipients via autocrine and paracrine mechanisms.

This study identifies novel exosomal proteins associated with diverse functions, signaling pathways, and cell origins in ARDS lavage samples. These differentiated proteins may serve as regenerative niches for re-alveolarization in injured lungs.

Regulation of stem cells requires coordination of the cells that make up the stem cell niche. Here, we describe a mechanism that allows communication between niche cells to coordinate their activity and shape the signaling environment surrounding resident stem cells. Using the Drosophila hematopoietic organ, the lymph gland, we show that cells of the hematopoietic niche, the posterior signaling center (PSC), communicate using gap junctions (GJs) and form a signaling network. This network allows PSC cells to exchange Ca2+ signals repetitively which regulate the hematopoietic niche. Disruption of Ca2+ signaling in the PSC or the GJ-mediated network connecting niche cells causes dysregulation of the PSC and blood progenitor differentiation. Analysis of PSC-derived cell signaling shows that the Hedgehog pathway acts downstream of GJ-mediated Ca2+ signaling to modulate the niche microenvironment. These data show that GJ-mediated communication between hematopoietic niche cells maintains their homeostasis and consequently controls blood progenitor behavior.

Neural stem cells (NSCs) reside in a defined cellular microenvironment, the niche, which supports the generation and integration of newborn neurons. The mechanisms building a sophisticated niche structure around NSCs and their functional relevance for neurogenesis are yet to be understood. In the Drosophila larval brain, the cortex glia (CG) encase individual NSC lineages in membranous chambers, organising the stem cell population and newborn neurons into a stereotypic structure. We first found that CG wrap around lineage-related cells regardless of their identity, showing that lineage information builds CG architecture. We then discovered that a mechanism of temporally controlled differential adhesion using conserved complexes supports the individual encasing of NSC lineages. An intralineage adhesion through homophilic Neuroglian interactions provides strong binding between cells of a same lineage, while a weaker interaction through Neurexin-IV and Wrapper exists between NSC lineages and CG. Loss of Neuroglian results in NSC lineages clumped together and in an altered CG network, while loss of Neurexin-IV/Wrapper generates larger yet defined CG chamber grouping several lineages together. Axonal projections of newborn neurons are also altered in these conditions. Further, we link the loss of these 2 adhesion complexes specifically during development to locomotor hyperactivity in the resulting adults. Altogether, our findings identify a belt of adhesions building a neurogenic niche at the scale of individual stem cell and provide the proof of concept that niche properties during development shape adult behaviour.

The capacity of a tissue to continuously alter its phenotype lies at the heart of how an animal is able to quickly adapt to changes in environmental stimuli. Within tissues, differentiated cells are rigid and play a limited role in adapting to new environments; however, differentiated cells are replenished by stem cells that are defined by their phenotypic plasticity. Here we demonstrate that a Wnt-responsive stem cell niche in the junctional epithelium is responsible for the capability of this tissue to quickly adapt to changes in the physical consistency of a diet. Mechanical input from chewing is required to both establish and maintain this niche. Since the junctional epithelium directly attaches to the tooth surface via hemidesmosomes, a soft diet requires minimal mastication, and consequently, lower distortional strains are produced in the tissue. This reduced strain state is accompanied by reduced mitotic activity in both stem cells and their progeny, leading to tissue atrophy. The atrophied junctional epithelium exhibits suboptimal barrier functions, allowing the ingression of bacteria into the underlying connective tissues, which in turn trigger inflammation and mild alveolar bone loss. These data link the mechanics of chewing to the biology of tooth-supporting tissues, revealing how a stem cell niche is responsible for the remarkable adaptability of the junctional epithelium to different diets.

Notch signaling regulates stem cells across animal phylogeny. C. elegans Notch signaling activates transcription of two genes, lst-1 and sygl-1, that encode potent regulators of germline stem cells. The LST-1 protein regulates stem cells in two distinct ways: It promotes self-renewal posttranscriptionally and also restricts self-renewal by a poorly understood mechanism. Its self-renewal promoting activity resides in its N-terminal region, while its self-renewal restricting activity resides in its C-terminal region and requires the Zn finger. Here, we report that LST-1 limits self-renewal by down-regulating Notch-dependent transcription. We detect LST-1 in the nucleus, in addition to its previously known cytoplasmic localization. LST-1 lowers nascent transcript levels at both lst-1 and sygl-1 loci but not at let-858, a Notch-independent locus. LST-1 also lowers levels of two key components of the Notch activation complex, the LAG-1 DNA binding protein and Notch intracellular domain (NICD). Genetically, an LST-1 Zn finger mutant increases Notch signaling strength in both gain- and loss-of-function GLP-1/Notch receptor mutants. Biochemically, LST-1 co-immunoprecipitates with LAG-1 from nematode extracts, suggesting a direct effect. LST-1 is thus a bifunctional regulator that coordinates posttranscriptional and transcriptional mechanisms in a single protein. This LST-1 bifunctionality relies on its bipartite protein architecture and is bolstered by generation of two LST-1 isoforms, one specialized for Notch downregulation. A conserved theme from worms to human is the coupling of PUF-mediated RNA repression together with Notch feedback in the same protein.

Biological rhythms are involved in almost all types of biological processes, not only physiological processes but also morphogenesis. Currently, how periodic morphological patterns of tissues/organs in multicellular organisms form is not fully understood. Here, using mouse zigzag hair, which has 3 bends, we found that a change in the combination of hair progenitors and their micro-niche and subsequent bend formation occur every three days. Chimeric loss-of-function and gain-of-function of Ptn and Aff3, which are upregulated immediately before bend formation, resulted in defects in the downward movement of the micro-niche and the rhythm of bend formation in an in vivo hair reconstitution assay. Our study demonstrates the periodic change in the combination between progenitors and micro-niche, which is vital for the unique infradian rhythm.

Recent studies have demonstrated that stem cells have attracted much attention due to their special abilities of proliferation, differentiation and self-renewal, and are of great significance in regenerative medicine and anti-aging research. Hence, finding natural medicines that intervene the fate specification of stem cells has become a priority. Ginsenosides, the key components of natural botanical ginseng, have been extensively studied for versatile effects, such as regulating stem cells function and resisting aging. This review aims to summarize recent progression regarding the impact of ginsenosides on the behavior of adult stem cells, particularly from the perspective of proliferation, differentiation and self-renewal.

The accurate identification and isolation of ovarian stem cells from mammalian ovaries remain a major challenge because of the lack of specific surface markers and suitable in vitro culture systems. Optimized culture conditions for in vitro expansion of ovarian stem cells would allow for identifying requirements of these stem cells for proliferation and differentiation that would pave the way to uncover role of ovarian stem cells in ovarian pathophysiology. Here, we used three-dimensional (3D) aggregate culture system for enrichment of ovarian stem cells and named them aggregate-derived stem cells (ASCs). We hypothesized that mimicking the ovarian microenvironment in vitro by using an aggregate model of the ovary would provide a suitable niche for the isolation of ovarian stem cells from adult mouse and human ovaries and wanted to find out the main cellular pathway governing the proliferation of these stem cells.

We showed that ovarian aggregates take an example from ovary microenvironment in terms of expression of ovarian markers, hormone secretion and supporting the viability of the cells. We found that aggregates-derived stem cells proliferate in vitro as long-term while remained expression of germline markers. These ovarian stem cells differentiated to oocyte like cells in vitro spontaneously. Transplantation of these stem cells in to chemotherapy mouse ovary could restore ovarian structure. RNA-sequencing analysis revealed that interleukin6 is upregulated pathway in ovarian aggregate-derived stem cells. Our data showed that JAK/Stat3 signaling pathway which is activated downstream of IL6 is critical for ovarian stem cells proliferation.

We developed a platform that is highly reproducible for in vitro propagation of ovarian stem cells. Our study provides a primary insight into cellular pathway governing the proliferation of ovarian stem cells.

Adult stem cells (ASCs) reside throughout the body and support various tissue. Owing to their self-renewal capacity and differentiation potential, ASCs have the potential to be used in regenerative medicine. Their survival, quiescence, and activation are influenced by specific signals within their microenvironment or niche. In better words, the stem cell function is significantly influenced by various extrinsic signals derived from the niche. The stem cell niche is a complex and dynamic network surrounding stem cells that plays a crucial role in maintaining stemness. Studies on stem cell niche have suggested that aged niche contributes to the decline in stem cell function. Notably, functional loss of stem cells is highly associated with aging and age-related disorders. The stem cell niche is comprised of complex interactions between multiple cell types. Over the years, essential aspects of the stem cell niche have been revealed, including cell-cell contact, extracellular matrix interaction, soluble signaling factors, and biochemical and biophysical signals. Any alteration in the stem cell niche causes cell damage and affects the regenerative properties of the stem cells. A pristine stem cell niche might be essential for the proper functioning of stem cells and the maintenance of tissue homeostasis. In this regard, niche-targeted interventions may alleviate problems associated with aging in stem cell behavior. The purpose of this perspective is to discuss recent findings in the field of stem cell aging, heterogeneity of stem cell niches, and impact of age-related changes on stem cell behavior. We further focused on how the niche affects stem cells in homeostasis, aging, and the progression of malignant diseases. Finally, we detail the therapeutic strategies for tissue repair, with a particular emphasis on aging.

The specialized cell types of the mucociliary epithelium (MCE) lining the respiratory tract enable continuous airway clearing, with its defects leading to chronic respiratory diseases. The molecular mechanisms driving cell fate acquisition and temporal specialization during mucociliary epithelial development remain largely unknown. Here, we profile the developing Xenopus MCE from pluripotent to mature stages by single-cell transcriptomics, identifying multipotent early epithelial progenitors that execute multilineage cues before specializing into late-stage ionocytes and goblet and basal cells. Combining in silico lineage inference, in situ hybridization, and single-cell multiplexed RNA imaging, we capture the initial bifurcation into early epithelial and multiciliated progenitors and chart cell type emergence and fate progression into specialized cell types. Comparative analysis of nine airway atlases reveals an evolutionary conserved transcriptional module in ciliated cells, whereas secretory and basal types execute distinct function-specific programs across vertebrates. We uncover a continuous nonhierarchical model of MCE development alongside a data resource for understanding respiratory biology.