Current status of nanofat in the management of knee osteoarthritis: A systematic review

Table 1 Summary of the studies included in systematic review

Ref.	Year	Study type	Samples	Outcomes analyzed	Results	Conclusion
Cicione et al[28]	2023	Preclinical in vitro	Lipoaspirate from 18 patients	Tissue processing, immunohistochemical analysis, RNA extraction, gene expression analysis	Increased amount of stroma and a reduction of adipocytes in micro-fragmented adipose tissue and nanofat adipose tissue, with the latter displaying the highest content of collagen type I, CD31, CD34 and proliferating cell nuclear antigen with increasing expression of NANOG, Sox2, OCT3/4, COL1A1 and IL-6 without significant differences in terms of IL-1β and inducible nitric oxide synthetase	Micro-fragmented adipose tissue and nanofat adipose tissue techniques allowed the rapid isolation of ASC-rich grafts with a high anabolic and proliferative potential. However, neoadjuvant therapy showed the highest levels of extracellular matrix content, replicating cells, and stemness gene expression
Quintero Sierra et al[9]	2023	Preclinical in vitro	Nanofat-derived SVF. Non-ASC collagenase-derived ASC. Nanofat-derived-ASC enzymatic digestion of nanofat-SVF	Morphological analysis, cellular yield, proliferation capacity, clonogenic capacity, immunophenotyping, differentiation assay, immunostaining	Hy-Tissue Nanofat is a new, simple system that reduces the time of adipose tissue processing drastically and guarantees the survival of regenerative units	Hy-Tissue Nanofat as a rapid, standardized, and efficient system able to produce an emulsion fat rich in viable, proliferative, and multipotent ASCs, suggesting a potential use in regenerative medicine and tissue engineering when translated into clinical practice
Cohen et al[16]	2019	Preclinical in vitro	10 patients	Cell counts, cell viabilities, cell cultures, and cell images were taken with a florescent microscope	The LipocubeNano shown to trap more fibrous tissue, with higher cellcounts with equal viability compared to Tulip’s NanoTransfer system	Nanofat from LipocubeNano has a higher regenerative cell count and more SVF cells than the other common mechanical method of nanofat processing
Ge et al[23]	2023	Preclinical in vivo	50 male Sprague-Dawley rats	Paw withdrawal latency, thermal withdrawal latency histopathological and immunohistochemical examination, wound healing, and transwell assays were performed to assess effects of nanofat lysate on chondrocytes. RNA-seq, qPCR and Western blot assays were conducted to clarify the mechanism of nanofat lysate	Nanofat lysate significantly improved the proliferation, wound healing, and migration of chondrocytes. It significantly restored the tumor necrosis factor-alpha-altered anabolic markers (Sox9, collagen type II and aggrecan) and catabolic markers (IL-6 and matrix metalloproteinase 13) through transforming growth factor-beta-Smad2/3 signalling pathway	Nanofat lysate from nanofat and demonstrated its therapeutic efficacy of relieving joint pain and cartilage degradation against OA in rats as well as chondroprotective activity of improving cell viability, wound healing, cell migration, and the anabolism/catabolism balance against inflammatory stress in chondrocytes
Chen et al[8]	2021	Preclinical in vivo	40 male Sprague-Dawley rats	Pain behaviour evaluation. Histopathological analysis. Immunohistochemical analysis. Transferase dUTP nick end labelling assay	Nanofat promoted the cell viability of chondrocytes, induced wound healing of IL-1β-treated chondrocytes, reversed the abnormal gene expression of IL-1β-treated chondrocytes	Nanofat exerted anti-OA efficacy by ameliorating joint pain symptoms and preventing cartilage degradation of OA rats through paracrine-based actions on anabolic, catabolic, and hypertrophic molecules of chondrocytes
Zheng et al[20]	2019	Preclinical in vivo	Male BALB/c-nu nude mice	Estimation of mechanism by which fat extract impacts graft survival, the proangiogenic, anti-apoptotic and pro-proliferative activities of fat extract in grafts in vivo and in cultured human vascular endothelial cells, adipose-derived stem cells and fat tissue in vitro	A higher fat integrity, more viable adipocytes, more CD31-positive blood vessels, fewer apoptotic cells and more Ki67-positive proliferating cells were observed in the nanofat-treated and fat extract-treated groups. Fat extract showed proangiogenic effects on HUVECs, anti-apoptotic effects on fat tissue cultured under hypoxic conditions and an ability to promote ADSCs proliferation and maintain their multiple differentiation capacity	Fat extract could improve fat graft survival via proangiogenic, anti-apoptotic and pro-proliferative effects on ADSCs. Fat extract plus nanofat-assisted fat grafting is a new strategy that could potentially be used in clinical applications
Han et al[31]	2022	Preclinical in vitro and in vivo	Sprague-Dawley rats	Cartilage-targeted retention efficiency, lubrication performance, friction coefficient, gene expression analysis	The microspheres effectively enhanced the cartilage-targeted retention efficiency of nanofat, which also resulted in remarkable lubrication performance, with the friction coefficient being reduced by approximately 80%, which was maintained over time. The three-dimensiona penetrating structure of the microspheres stimulated cytokine secretion by the NF-derived stem cells, upregulating the expression of anabolism-related genes and downregulating catabolism, and the expression of inflammation-related and pain-related genes	The multifunctional platform with nanofat immobilization and super-lubrication, which showed great potential for the minimally invasive treatment of osteoarthritis
Smyshlyaev et al[35]	2022	Clinical	70 patients	Physical examination MRI. Adverse events	Decrease in swelling of the surrounding soft tissues with restoration of normal anatomical outlines of the knee joint. Increase in the circumference of the thigh at the level of the lower third. The absence of hyperthermia in the knee joint area. Reduction of pain on palpation of the patella and condyles of the femur and tibia. Increase range of movements. Disappearance of enthesopathies of collateral ligaments and pain in the hamstring muscle tendons. Decrease in the amount of free intra-articular fluid. No serious adverse events noted	Treatment of OA with nanofat is the most effective technique, despite the relatively high cost of obtaining the final cell product
Chen et al[8]	2021	Clinical	18 patients	Visual analog scale, Western Ontario and McMaster Universities Osteoarthritis Index, MRI	Intra-articular nanofat injections alleviated symptoms and pain in OA patients	The study verified the clinical efficacy and safety of nanofat

ADSCs: Adipose-derived stem cells; ASC: Adherent spleen cells; IL: Interleukin; MRI: Magnetic resonance imaging; OA: Osteoarthritis; Sox: Sex determining region Y-box; SVF: Stromal vascular fraction.