|
1
|
Liu H, Zhu X, Cao X, Chi A, Dai J, Wang Z, Deng C, Zhang M. IL-1β-primed mesenchymal stromal cells exert enhanced therapeutic effects to alleviate Chronic Prostatitis/Chronic Pelvic Pain Syndrome through systemic immunity. Stem Cell Res Ther 2021; 12:514. [PMID: 34563249 PMCID: PMC8466748 DOI: 10.1186/s13287-021-02579-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 09/04/2021] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) seriously affects patient health. Despite the elusiveness of innate therapeutic effects, mesenchymal stromal cells (MSCs) hold great promise for inflammation-related diseases. Recent evidence indicates that disease-specific inflammatory cytokines could enhance the therapeutic effects of MSCs. METHODS By establishing a CP/CPPS mouse model and pretreating MSCs with the cytokine interleukin-1β (IL-1β), we studied the IL-1β-primed MSC immunoregulatory ability and targeted migration ability in vitro and in CP/CPPS mice. RESULTS IL-1β levels significantly increased in the prostate tissue and serum of experimental autoimmune prostatitis (EAP) mice. Pretreatment with IL-1β enhanced the immunomodulatory potential and targeted migration of MSCs in vitro. Furthermore, intravenous infusion of IL-1β-primed MSCs dampened inflammation in prostate tissues and alleviated hyperalgesia in EAP mice. The infused MSCs inhibited monocyte infiltration and promoted regulatory T lymphocyte formation in prostate tissue, thus remodeling the local environment. Surprisingly, IL-1β-primed MSCs exhibited improved accumulation in the spleen but not in prostate tissue. Accordingly, infused MSCs reshaped systemic immunity by reducing the proportion of Ly6ChighCD11b+ monocytes and boosting the proportion of CD4+Foxp3+ regulatory T lymphocytes in the spleen and lung. Inflammatory chemokine (C-C motif) ligand 2 (CCL2) decreased through the downregulation of the NF-κB and JNK/MAPK pathways by inflammatory resolution via MSCs infusion to alleviate pain. CONCLUSION In summary, IL-1β-primed MSCs restored systemic immunologic homeostasis to alleviate CP/CPPS by modulating systemic immunity. These findings provide a novel strategy to boost the therapeutic effects of MSC-based therapy for CP/CPPS and reveal the essential role of systematic immunity in the treatment of CP/CPPS with MSC infusion.
Collapse
Affiliation(s)
- Hanchao Liu
- Department of Andrology, The First Affiliated Hospital of Sun Yat-Sen University, No. 58 Zhongshan Second Road, Guangzhou, China
| | - Xinning Zhu
- Reproductive Medicine Research Center, The Sixth Affiliated Hospital of Sun Yat-Sen University, Guangzhou, China
| | - Xiaohui Cao
- Hubei Key Laboratory for Kidney Disease Pathogenesis and Intervention, School of Medicine, Hubei Polytechnic University, 16 North Guilin Road, Huangshi, 435003, Hubei, China
| | - Ani Chi
- Department of Andrology, The First Affiliated Hospital of Sun Yat-Sen University, No. 58 Zhongshan Second Road, Guangzhou, China
| | - Jian Dai
- Department of Andrology, The First Affiliated Hospital of Sun Yat-Sen University, No. 58 Zhongshan Second Road, Guangzhou, China.,Guangdong Provincial Key Laboratory of Orthopaedics and Traumatology, The First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 51008, China
| | - Zhenqing Wang
- Department of Andrology, The First Affiliated Hospital of Sun Yat-Sen University, No. 58 Zhongshan Second Road, Guangzhou, China
| | - Chunhua Deng
- Department of Andrology, The First Affiliated Hospital of Sun Yat-Sen University, No. 58 Zhongshan Second Road, Guangzhou, China.
| | - Min Zhang
- Department of Andrology, The First Affiliated Hospital of Sun Yat-Sen University, No. 58 Zhongshan Second Road, Guangzhou, China.
| |
Collapse
|
|
2
|
Yi K, Hatayama N, Hirai S, Qu N, Hayashi S, Kawata S, Nagahori K, Naito M, Itoh M. Development of heterotopic transplantation of the testis with the epididymis to evaluate an aspect of testicular immunology in rats. PLoS One 2017; 12:e0177067. [PMID: 28475594 PMCID: PMC5419600 DOI: 10.1371/journal.pone.0177067] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 04/22/2017] [Indexed: 01/08/2023] Open
Abstract
Transplantation of testicular cells and tissues has been studied for the investigation of immunology of the testis, which is an immunologically privileged organ. However, reports of transplant of the testis at organ level have been extremely limited because of technical difficulties of the orthotopic testis transplantation (OTT) in experimental animals. In the present study, we developed a new and simple model of the heterotopic testis transplantation (HTT), which is donor testis transplantation into the cervical region of recipients, in a syngeneic model in rats [donor Lewis (LEW) graft to LEW recipient]. The duration of HTT was significantly shorter and success rate higher than that of OTT. To histologically evaluate HTT, the local immune responses were compared among the syngeneic model, an acute rejection allogeneic model [donor Augustus Copenhagen Irish (ACI) graft to LEW recipient] and a chronic rejection allogeneic model (donor F344 graft to LEW recipient) at postoperative day 3. We found that allogeneic ACI grafts resulted in mild and not severe orchitic lesions, whereas immune responses of allogeneic F344 grafts seemed intact and were not significantly different from those of syngeneic LEW grafts. These results suggest that our new operative procedure will be useful in future for the investigation of the testicular immunology.
Collapse
Affiliation(s)
- Kai Yi
- Department of Anatomy, Tokyo Medical University, Tokyo, Japan
| | - Naoyuki Hatayama
- Department of Anatomy, Tokyo Medical University, Tokyo, Japan
- Department of Anatomy, Aichi Medical University, Aichi, Japan
- * E-mail: ,
| | - Shuichi Hirai
- Department of Anatomy, Aichi Medical University, Aichi, Japan
| | - Ning Qu
- Department of Anatomy, Tokyo Medical University, Tokyo, Japan
| | - Shogo Hayashi
- Department of Anatomy, Tokyo Medical University, Tokyo, Japan
| | - Shinichi Kawata
- Department of Anatomy, Tokyo Medical University, Tokyo, Japan
| | - Kenta Nagahori
- Department of Anatomy, Tokyo Medical University, Tokyo, Japan
| | - Munekazu Naito
- Department of Anatomy, Aichi Medical University, Aichi, Japan
| | - Masahiro Itoh
- Department of Anatomy, Tokyo Medical University, Tokyo, Japan
| |
Collapse
|
|
3
|
Quinn M, McMillin M, Galindo C, Frampton G, Pae HY, DeMorrow S. Bile acids permeabilize the blood brain barrier after bile duct ligation in rats via Rac1-dependent mechanisms. Dig Liver Dis 2014; 46:527-34. [PMID: 24629820 PMCID: PMC4065628 DOI: 10.1016/j.dld.2014.01.159] [Citation(s) in RCA: 181] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 01/10/2014] [Accepted: 01/28/2014] [Indexed: 02/08/2023]
Abstract
BACKGROUND The blood brain barrier tightly regulates the passage of molecules into the brain and becomes leaky following obstructive cholestasis. The aim of this study was to determine if increased serum bile acids observed during cholestasis permeabilize the blood brain barrier. METHODS Rats underwent bile duct ligation or deoxycholic or chenodeoxycholic acid injections and blood brain barrier permeability assessed. In vitro, the permeability of rat brain microvessel endothelial cell monolayers, the expression and phosphorylation of occludin, ZO-1 and ZO-2 as well as the activity of Rac1 was assessed after treatment with plasma from cholestatic rats, or bile acid treatment, in the presence of a Rac1 inhibitor. RESULTS Blood brain barrier permeability was increased in vivo and in vitro following bile duct ligation or treatment with bile acids. Associated with the bile acid-stimulated increase in endothelial cell monolayer permeability was elevated Rac1 activity and increased phosphorylation of occludin. Pretreatment of endothelial cell monolayers with a Rac1 inhibitor prevented the effects of bile acid treatment on occludin phosphorylation and monolayer permeability. CONCLUSIONS These data suggest that increased circulating serum bile acids may contribute to the increased permeability of the blood brain barrier seen during obstructive cholestasis via disruption of tight junctions.
Collapse
Affiliation(s)
- Matthew Quinn
- Department of Internal Medicine, Texas A&M Health Science Center College of Medicine, Temple, Texas, USA
| | - Matthew McMillin
- Department of Internal Medicine, Texas A&M Health Science Center College of Medicine, Temple, Texas, USA
| | - Cheryl Galindo
- Department of Internal Medicine, Texas A&M Health Science Center College of Medicine, Temple, Texas, USA
| | - Gabriel Frampton
- Department of Internal Medicine, Texas A&M Health Science Center College of Medicine, Temple, Texas, USA
| | - Hae Yong Pae
- Department of Internal Medicine, Texas A&M Health Science Center College of Medicine, Temple, Texas, USA
| | - Sharon DeMorrow
- Department of Internal Medicine, Texas A&M Health Science Center College of Medicine, Temple, Texas, USA,Digestive Disease Research Center, Scott & White Hospital, Temple, Texas, USA,Central Texas Veterans Health Care System, Temple, Texas, USA
| |
Collapse
|
|
4
|
Sertoli cells--immunological sentinels of spermatogenesis. Semin Cell Dev Biol 2014; 30:36-44. [PMID: 24603046 DOI: 10.1016/j.semcdb.2014.02.011] [Citation(s) in RCA: 183] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 02/13/2014] [Accepted: 02/24/2014] [Indexed: 12/22/2022]
Abstract
Testicular germ cells, which appear after the establishment of central tolerance, express novel cell surface and intracellular proteins that can be recognized as 'foreign antigens' by the host's immune system. However, normally these germ cells do not evoke an auto-reactive immune response. The focus of this manuscript is to review the evidence that the blood-testis-barrier (BTB)/Sertoli cell (SC) barrier along with the SCs ability to modulate the immune response is vital for protecting auto-antigenic germ cells. In normal testis, the BTB/SC barrier protects the majority of the auto-antigenic germ cells by limiting access by the immune system and sequestering these 'new antigens'. SCs also modulate testis immune cells (induce regulatory immune cells) by expressing several immunoregulatory factors, thereby creating a local tolerogenic environment optimal for survival of nonsequesetred auto-antigenic germ cells. Collectively, the fortress created by the BTB/SC barrier along with modulation of the immune response is pivotal for completion of spermatogenesis and species survival.
Collapse
|
|
5
|
Pelz J, Härtig W, Weise C, Hobohm C, Schneider D, Krueger M, Kacza J, Michalski D. Endothelial barrier antigen-immunoreactivity is conversely associated with blood-brain barrier dysfunction after embolic stroke in rats. Eur J Histochem 2013; 57:e38. [PMID: 24441191 PMCID: PMC3896040 DOI: 10.4081/ejh.2013.e38] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2013] [Revised: 11/21/2013] [Accepted: 10/18/2013] [Indexed: 12/12/2022] Open
Abstract
While the concept of the Neurovascular Unit (NVU) is increasingly recognized for exploring mechanisms of tissue damage in ischemic stroke, immunohistochemical analyses are of interest to specifically visualize constituents like the endothelium. Changes in immunoreactivity have also been discussed to reflect functional aspects, e.g., the integrity of the blood-brain barrier (BBB). This study aimed to characterize the endothelial barrier antigen (EBA) as addressed by the antibody SMI-71 in a rat model of embolic stroke, considering FITC-albumin as BBB leakage marker and serum levels of BBB-associated matrix metalloproteinases (MMPs) to explore its functional significance. Five and 25 h after ischemia onset, regions with decreased BBB integrity exhibited a reduction in number and area of EBA-immunopositive vessels, while the stained area per vessel was not affected. Surprisingly, EBA content of remaining vessels tended to be increased in areas of BBB dysfunction. Analyses addressing this interrelation resulted in a significant and inverse correlation between the vessels' EBA content and degree of BBB permeability. In conclusion, these data provide evidence for a functional relationship between EBA-immunoreactivity and BBB dysfunction in experimental ischemic stroke. Further studies are required to explore the underlying mechanisms of altered EBA-immunoreactivity, which might help to identify novel neuroprotective strategies.
Collapse
|
|
6
|
Liu Y, Yi S, Zhang J, Fang Z, Zhou F, Jia W, Liu Z, Ye G. Effect of Microbubble-enhanced Ultrasound on Prostate Permeability: A Potential Therapeutic Method for Prostate Disease. Urology 2013; 81:921.e1-7. [DOI: 10.1016/j.urology.2012.12.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 12/05/2012] [Accepted: 12/12/2012] [Indexed: 10/27/2022]
|
|
7
|
Setchell BP. Blood-testis barrier, junctional and transport proteins and spermatogenesis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 636:212-33. [PMID: 19856170 DOI: 10.1007/978-0-387-09597-4_12] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Brian P Setchell
- Department of Anatomical Sciences, University of Adelaide, Adelaide, Australia.
| |
Collapse
|
|
8
|
Kalinin S, Feinstein DL, Xu HL, Huesa G, Pelligrino DA, Galea E. Degeneration of noradrenergic fibres from the locus coeruleus causes tight-junction disorganisation in the rat brain. Eur J Neurosci 2006; 24:3393-400. [PMID: 17229089 DOI: 10.1111/j.1460-9568.2006.05223.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although functional studies demonstrate that noradrenaline controls the permeability of the blood-brain barrier, it has never been determined whether this neurotransmitter regulates the tight junction (TJ) assembly that confers the barrier property to brain microvessels. We thus tested in rats the effect of pharmacological depletion of noradrenaline with the noradrenergic toxin DSP4 (5 mg/kg) on the expression of the TJ proteins zonula occludens-1 (ZO1) and occludin. The effectiveness of the lesion was confirmed by tyrosine hydroxylase immunoreactivity, which showed noradrenergic fibre reduction accompanied by debris and swollen fibres in DSP4-treated brains. Noradrenergic fibre degeneration caused: (i) gliosis; (ii) disappearance of TJ proteins in vascular cell-to-cell contacts (49.9 and 38.3% reductions for occludin and ZO1, respectively); (iii) a 49.2% decrease in total ZO1 protein, measured by Western blot analysis, parallel to a 39.5% decrease in ZO1 mRNA, measured by real-time PCR; and (iv) a relative increase in the beta occludin isoform (62.9%), with no change in total occludin protein or mRNA. The expression of endothelial brain antigen, a marker of a functionally competent brain endothelium, was also reduced. We conclude that damage to the ascending fibres from the locus coeruleus caused TJ disruption and gliosis, a sign of inflammation. These results imply that the locus coeruleus degeneration reported in Alzheimer's and Parkinson's diseases may contribute to these disorders by causing blood-brain barrier dysfunction. Whether the vascular damage is the result of impaired noradrenergic transmission or secondary to the inflammatory reaction remains to be determined.
Collapse
Affiliation(s)
- Sergey Kalinin
- Department of Anaesthesiology, University of Illinois at Chicago, Illinois, USA
| | | | | | | | | | | |
Collapse
|
|
9
|
N Ghabriel M, J Lu J, Tadros R, Hermanis G. A narrow time-window for access to the brain by exogenous protein after immunological targeting of a blood-brain barrier antigen. J Comp Pathol 2004; 131:52-60. [PMID: 15144799 DOI: 10.1016/j.jcpa.2004.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2003] [Accepted: 01/13/2004] [Indexed: 10/26/2022]
Abstract
The endothelial barrier antigen (EBA) is a membrane protein expressed by endothelial cells of the rat blood-brain barrier (BBB). A previous short-term non-recovery study demonstrated that immunological targeting of EBA by intravenous administration of a monoclonal antibody (anti-EBA) led to acute opening of the BBB to exogenous and endogenous tracers. The aims of the present study were to determine whether opening of the BBB was reversible and compatible with survival, and whether a "therapeutic window" existed. A single intravenous injection of one of three doses (high, medium and low) of anti-EBA was used. Animals were allowed to survive for periods ranging from 17 min to 4 days. The tracer horseradish peroxidase (HRP) was administered intravenously 10 min before perfusion fixation, and its distribution was assessed in Vibratome sections of the brain and spinal cord. Leakage of HRP into the central nervous system was dose- and time-dependent. The medium dose produced incipient HRP leakage at 17 min and widespread pronounced leakage at 30 min. Progressive reduction in HRP permeability occurred from 45 min to 2 h, with barrier restoration by 3 h. At all subsequent time intervals (6 h-4 days) the BBB remained impermeable to HRP. The low and high doses produced less and greater HRP leakage, respectively, but restoration of the barrier still occurred at 3 h. The high dose, however, produced a number of deaths. Animals treated with an isotype control antibody showed no HRP leakage at comparable time intervals. The results indicated that (1) this model was compatible with survival, (2) opening of the BBB was monophasic and transient, occurring during a narrow "time-window", and (3) the barrier, once reconstituted, maintained its integrity.
Collapse
Affiliation(s)
- M N Ghabriel
- Department of Anatomical Sciences, University of Adelaide, The Medical School, Frome Road, Adelaide 5005, Australia
| | | | | | | |
Collapse
|
|
10
|
Schinazi RF, Hurwitz SJ, Liberman I, Glazkova Y, Mourier NS, Olson J, Keane T. Tissue disposition of 5-o-carboranyluracil--a novel agent for the boron neutron capture therapy of prostate cancer. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2004; 23:291-306. [PMID: 15043155 DOI: 10.1081/ncn-120027836] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The carboranyl nucleotides beta-D-5-o-carboranyl-2'-deoxyuridine (D-CDU), 1-(beta-L-arabinosyl)-5-o-carboranyluracil (D-ribo-CU) and the nucleotide base 5-o-carboranyluracil (CU), were developed as sensitizers for boron neutron capture therapy (BNCT). A structure activity study was initiated to determine the agent most suitable for targeting prostate tumors. Cellular accumulation studies were performed using LNCaP human prostate tumor cells, and the respective tumor disposition profiles were investigated in male nude mice bearing LNCaP and 9479 human prostate tumor xenografts in their flanks. D-CDU achieved high cellular concentrations in LNCaP cells and up to 2.5% of the total cellular compound was recovered in the 5'-monophosphorylated form. In vivo concentrations of D-CDU were similar in LNCaP and 9479 tumor xenografts. Studies in 9479 xenografted bearing mice indicated that increasing the number of hydroxyl groups in the sugar moeity of the carboranyl nucleosides corresponded with an increased rate and extent of renal elimination, shorter serum half-lives and an increased tissue specificity. Tumor/normal prostate ratios were greatest with the nucleoside base CU. These studies indicate that similar nucleoside analogues and bases may have different tissue affinities and retention properties, which should be considered when selecting agents for sensitizing specific tumors for eventual BNCT treatment. CU was found to be the most suitable compound for further development to treat prostate cancer.
Collapse
|
|
11
|
Castilla-Cortazar I, Diez N, Garcia-Fernandez M, Puche JE, Diez-Caballero F, Quiroga J, Diaz-Sanchez M, Castilla A, Casares AD, Varela-Nieto I, Prieto J, Gonzalez-Baron S. Hematotesticular barrier is altered from early stages of liver cirrhosis: Effect of insulin-like growth factor 1. World J Gastroenterol 2004; 10:2529-34. [PMID: 15300898 PMCID: PMC4572155 DOI: 10.3748/wjg.v10.i17.2529] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
AIM: The pathogenesis of hypogonadism in liver cirrhosis is not well understood. Previous results from our laboratory showed that IGF-1 deficiency might play a pathogenetic role in hypogonadism of cirrhosis. The administration of IGF-1 for a short period of time reverted the testicular atrophy associated with advanced experimental cirrhosis. The aim of this study was to establish the historical progression of the described alterations in the testes, explore testicular morphology, histopathology, cellular proliferation, integrity of testicular barrier and hypophyso-gonadal axis in rats with no ascitic cirrhosis.
METHODS: Male Wistar rats with histologically-proven cirrhosis induced with carbon tetrachloride (CCl4) for 11 wk, were allocated into two groups (n = 12, each) to receive recombinant IGF-1 (2 μg/100 g.d, sc) for two weeks or vehicle. Healthy rats receiving vehicle were used as control group (n = 12).
RESULTS: Compared to controls, rats with compensated cirrhosis showed a normal testicular size and weight and very few histopathological testicular abnormalities. However, these animals showed a significant diminution of cellular proliferation and a reduction of testicular transferrin expression. In addition, pituitary-gonadal axis was altered, with significant higher levels of FSH (P < 0.001 vs controls) and increased levels of LH in untreated cirrhotic animals. Interestingly, IGF-1 treatment normalized testicular transferrin expression and cellular proliferation and reduced serum levels of LH (P = ns vs controls, and P < 0.01 vs untreated cirrhotic group).
CONCLUSION: The testicular barrier is altered from an early stage of cirrhosis, shown by a reduction of transferrin expression in Sertoli cells, a diminished cellular proliferation and an altered gonadal axis. The treatment with IGF-1 could be also useful in this initial stage of testicular disorder associated with compensated cirrhosis.
Collapse
Affiliation(s)
- Inma Castilla-Cortazar
- Department of Human Physiology, School of Medicine, University of Navarra, Pamplona, Spain.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
|
12
|
Abstract
Various barriers in the testis may prevent hormones from readily reaching the cells they are supposed to stimulate, especially the hydrophilic hormones from the pituitary. For example, LH must pass through or between the endothelial cells lining the blood vessels to reach the surface of the Leydig cells, and FSH has the additional barrier of the peritubular myoid cells before it reaches the Sertoli cells. The specialised junctions between pairs of Sertoli cells would severely restrict the passage of peptides from blood to the luminal fluid and therefore to the cells inside this barrier, such as the later spermatocytes and spermatids. There is evidence in the literature that radioactively labelled LH does not pass readily into the testis from the blood, and the concentration of native LH in the interstitial extracellular fluid surrounding the Leydig cells in rats is only about one-fifth of that in blood plasma. Furthermore, after injection with LHRH, there are large rises in LH in the blood within 15 min, at which time the Leydig cells have already responded by increasing their content of testosterone, but with no significant change in the concentration of LH in the interstitial extracellular fluid. Either the Leydig cells respond to very small changes in LH, or the testicular endothelial cells in some way mediate the response of the Leydig cells to LH, for which there is now some evidence from co-cultures of endothelial and Leydig cells. The lipophilic steroid hormones, such as testosterone, which are produced by the Leydig cells, have actions within the seminiferous tubules in the testis but also in other parts of the body. They should pass more readily through cells than the hydrophilic peptides; however, the concentration of testosterone in the fluid inside the seminiferous tubules is less than in the interstitial extracellular fluid in the testis, especially after stimulation by LH released after injection of LHRH and despite the presence inside the tubules of high concentrations of an androgen-binding protein. The concentration of testosterone in testicular venous blood does not rise to the same extent as that in the interstitial extracellular fluid, suggesting that there may also be some restriction to movement of the steroid across the endothelium. There is a very poor correlation between the concentrations of testosterone in fluids from the various compartments of the testis and in peripheral blood plasma. Determination of the testosterone concentration in the whole testis is also probably of little predictive value, because the high concentrations of lipid in the Leydig cells would tend to concentrate testosterone there, and hormones inside these cells are unlikely to have any direct effect on other cells in the testis. The best predictor of testosterone concentrations around cells in the testis is the level of testosterone in testicular venous blood, the collection of which for testosterone analysis is a reasonably simple procedure in experimental animals and should be substituted for tissue sampling. There seems to be no simple way of determining the concentrations of peptide hormones in the vicinity of the testicular cells.
Collapse
|