Local regulation of spermatogenesis: a living cell approach

Impact of latent toxoplasmosis on the fertility indices of male rats

Infertility is a prevalent condition affecting approximately 70 million people worldwide and male factor contributes to about fifty percent of the issues. Studies on infectious agents as a possible cause of infertility has become prominent in the past decade. Toxoplasma gondii has emerged as a prime candidate as it has been found in the reproductive organs and semen of males of many animal species and humans. The aim of this study is to assess the effect of latent toxoplasmosis on experimental rat fertility. Ninety Toxoplasma infected rat were used as the experimental group besides, thirty control naïve ones. Both groups were observed clinically. Weekly assessment of fertility indices starting from the 7th week post infection till the 12th week were done by recording rat body weight, weight of testes, semen analysis and histo-morphometric analysis of the testes. Toxoplasma infected rats exhibited significant gradual loss of body weight and the absolute weight of the testes. The sperm characteristic parameters including percentage of motile sperm, percentage of viable sperm and sperm concentration in Toxoplasma infected rats showed highly significant decrease throughout the observation period in comparison to the control group with recording highly significant increase in the percentage of abnormal sperm forms. Pathological insults in tests of the infected rat group were denoted. Our findings demonstrated that Toxoplasma gondii is accused for affecting male rat main reproductive parameters and is implicated in the male reproductive disorders.

Perspectives of germ cell development in vitro in mammals

Pluripotent stem cells, such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are able to differentiate into all cell lineages of the embryo proper, including germ cells. This pluripotent property has a huge impact on the fields of regenerative medicine, developmental biology and reproductive engineering. Establishing the germ cell lineage from ESCs/iPSCs is the key biological subject, since it would contribute not only to dissection of the biological processes of germ cell development but also to production of unlimited numbers of functional gametes in vitro. Toward this goal, we recently established a culture system that induces functional mouse primordial germ cells (PGCs), precursors of all germ cells, from mouse ESCs/iPSCs. The successful in vitro production of PGCs arose from the study of pluripotent cell state, the signals inducing PGCs and the technology of transplantation. However, there are many obstacles to be overcome for the robust generation of mature gametes or for application of the culture system to other species, including humans and livestock. In this review, we discuss the requirements for a culture system to generate the germ cell lineage from ESCs/iPSCs.

Experimental diabetes-induced testicular damage in prepubertal rats

BACKGROUND

There has been a marked increase in the prevalence of childhood and/or adolescent diabetes worldwide. Testicular dysfunction in adult-onset diabetes is well established, whereas the impact of early onset diabetes on the functional development of the testis remains elusive. In the present study we investigated early oxidative impairments and progressive histological changes in streptozotocin (STZ)-induced diabetic prepubertal rat testis.

METHODS

Testes were sampled from prepubertal rats injected with a single bolus of STZ (90 mg/kg, i.p.) on Days 1, 3, 5, 7 and 14 after STZ injection for quantitation of testicular oxidative stress parameters in isolated subcellular fractions and mitochondrial and microsomal functional efficiency, as well as at weekly intervals over a period of 8 weeks for histological and flow cytometry analyses.

RESULTS

Prepubertal diabetic rats were severely hyperglycemic with reduced testes size. At the subcellular level, a progressive increase in oxidative stress parameters was discernible in the cytosolic and microsomal compartments from Day 1 after STZ, together with decreased antioxidant defenses. Surprisingly, tissue ascorbate and free catalytic iron levels were notably increased in diabetic rat testis. Mitochondrial dysfunction was manifested from Day 5, as evidenced by a reduction in electron transport activity. Histologically, tissue sections showed distorted seminiferous tubules and extensive cell vacuolization with progressive disappearance of spermatids in the lumen by Week 7 after STZ injection, observations that were consistent with flow cytometry data.

CONCLUSIONS

Herein we provide evidence that the onset of diabetes brings about oxidative changes at the subcellular level that cumulatively affect the functional growth of testes.

Glial cell line-derived neurotrophic factor (GDNF) induced migration of spermatogonial cells in vitro via MEK and NF-kB pathways

Glial cell line-derived neurotrophic factor (GDNF) regulates spermatogonial stem cell (SSC) maintenance. In the present study, we examined the levels and the cellular origin of GDNF in mouse testes during age-development, and the capacity of GDNF to induce migration of enriched GFR-α1 positive cells in vitro. The involvement of MAP kinase (MEK) and NF-kB signal pathways were examined. Our results show high levels of GDNF in testicular tissue of one-week-old mice which significantly decreased with age when examined by ELISA, real time PCR (qPCR) and immunofluorescence staining (IF) analysis. GDNF receptor (GFR-α1) expression was similar to GDNF when examined by qPCR analysis. Only Sertoli cell cultures (SCs) from one-week-old mice produced GDNF compared to SCs from older mice. However, peritubular cells from all the examined ages did not produce GDNF. The addition of recombinant GDNF (rGDNF) or supernatant from SCs from one-week-old mice to GFR-α1 positive cells induced their migration in vitro. This effect was significantly reduced by the addition of inhibitors to MEK (PD98059, U0126), NF-kB (PDTC) and IkB protease inhibitor (TPCK). Our results show for the first time the capacity of rGDNF and supernatant from SCs to induce migration of enriched GFR-α1 positive cells, and the possible involvement of MEK, NF-kB and IkB in this process. This study may suggest a novel role for GDNF in the regulation SSC niches and spermatogenesis.

Vascular endothelial growth factor regulates germ cell survival during establishment of spermatogenesis in the bovine testis

Vascular endothelial growth factor-A (VEGFA) is a hypoxia-inducible peptide essential for angiogenesis and targets nonvascular cells in a variety of tissues and cell types. The objective of the current study was to determine the function of VEGF during testis development in bulls. We used an explant tissue culture and treatment approach to test the hypothesis that VEGFA-164 could regulate the biological activity of bovine germ cells. We demonstrate that VEGFA, KDR, and FLT1 proteins are expressed in germ and somatic cells in the bovine testis. Treatment of bovine testis tissue with VEGFA in vitro resulted in significantly more germ cells following 5 days of culture when compared with controls. Quantitative real-time RT-PCR analysis determined that VEGF treatment stimulated an intracellular response that prevents germ cell death in bovine testis tissue explants, as indicated by increased expression of BCL2 relative to BAX and decreased expression of BNIP3 at 3, 6, and 24 h during culture. Blocking VEGF activity in vitro using antisera against KDR and VEGF significantly reduced the number of germ cells in VEGF-treated testis tissue to control levels at 120 h. Testis grafting provided in vivo evidence that bovine testis tissue treated with VEGFA for 5 days in culture contained significantly more differentiating germ cells compared with controls. These findings support the conclusion that VEGF supports germ cell survival and sperm production in bulls.

Endocrine regulation of the establishment of spermatogenesis in pigs

Somatic and germ cell maturation precedes the start of spermatogenesis and is coordinated, so efficient spermatogenesis will occur in the adults. The present study was conducted to evaluate endocrine regulation of germ and somatic cell homeostasis in the neonatal boar testis associated with the establishment of spermatogenesis. Testis tissue obtained from 3-, 5-, 7- and 14-day-old piglets were ectopically xenografted onto castrated, immunodeficient nude mice. Grafts were removed 22 weeks later and evaluated for growth and the establishment of spermatogenesis. Recipient mouse testosterone biosynthesis and follicle-stimulating hormone (FSH) concentrations were also assayed. Testis tissue graft growth was significantly greater in testis grafts from 3-day donor tissue when compared to all other ages; 5-, 7- and 14-day-old donor tissue weights were not significantly different at removal. Follicle-stimulating hormone concentrations in recipient mice supporting testis grafts from 5-, 7- and 14-day-old donor tissues did not differ and were similar to normal physiological levels in age-matched, intact nude mice. Serum FSH levels were significantly lower in recipient mice supporting testis grafts from 3-day-old donor tissue. Radioimmunoassay and biological assay indicated no differences in testosterone production by testis tissue grafts of varying donor age. Porcine testis tissue obtained from 3-, 5-, 7- and 14-day-old neonatal boars were all capable of producing round and elongate spermatids after 22 weeks of grafting, but testis grafts from 14-day-old donors had a significantly greater (eightfold) percentage of seminiferous tubules with spermatids compared to all other donor ages (p < 0.05). Cryopreservation did not affect the ability of testis tissue grafts to grow, produce testosterone or establish spermatogenesis when compared to controls (p < 0.05). Collectively, these data demonstrate intrinsic differences in the biological activity of germ and somatic cell populations during neonatal boar testis development associated with the establishment of spermatogenesis.

Reduced sperm yield from testicular biopsies of vasectomized men is due to increased apoptosis

OBJECTIVE

To compare sperm yields, apoptotic indices, and sperm DNA fragmentation from vasectomized men and fertile men undergoing vasectomy.

DESIGN

Testicular biopsies from vasectomized (n = 26) and fertile men (n = 46), were milked to calculate sperm/gram and also formalin-fixed to determine the numbers of developing sperm and incidence and intensities of testicular FasL, Fas, Bax, and Bcl-2. Testicular sperm DNA fragmentation was assessed using the alkaline Comet assay.

SETTING

An ART unit.

PATIENT(S)

Twenty-six men attending for intracytoplasmic sperm injection (ICSI) and 46 men attending for vasectomies.

MAIN OUTCOME MEASURE(S)

Spermatocyte, spermatid and sperm yields, Fas, FasL, and Bax staining.

RESULT(S)

Sperm yields from men vasectomized >5 years previously were markedly reduced compared to fertile men. Increased intensities of FasL and Bax staining were observed in the seminiferous tubules of vasectomy men. FasL positivity (percentage) also increased in Sertoli cells, and both FasL and Fas positivity (percentage) increased in primary spermatocytes and round spermatids of vasectomized men. Sperm DNA fragmentation, an end point marker of apoptosis, increased significantly in vasectomized men compared to fertile men.

CONCLUSION(S)

Reduced sperm yields after vasectomy are associated with increased apoptosis through the Fas-FasL and Bax pathways. Sperm after vasectomy displayed increased DNA fragmentation.

Transforming growth factor beta-1 decreases the yield of the second meiotic division of rat pachytene spermatocytes in vitro

BACKGROUND

TGF beta and its receptors are present in both germ cells and somatic cells of the male gonad. However, knock-out strategies for studying spermatogenesis regulation by TGF beta have been disappointing since TGF beta-or TGF beta receptor-null mice do not survive longer than a few weeks.

METHODS

In the present study, we addressed the role of TGF beta-1 on the completion of meiosis by rat pachytene spermatocytes (PS) cocultured with Sertoli cells. Identification and counting of meiotic cells were performed by cytology and cytometry.

RESULTS

Under our culture conditions, some PS differentiated into round spermatids (RS). When TGF beta-1 was added to the culture medium, neither the number of PS or of secondary spermatocytes nor the half-life of RS was modified by the factor. By contrast, the number of RS and the amount of TP1 mRNA were lower in TGF beta-1-treated cultures than in control cultures. Very few metaphase I cells were ever observed both in control and TGF beta-1-treated wells. Higher numbers of metaphase II were present and their number was enhanced by TGF beta-1 treatment. A TGF beta-like bioactivity was detected in control culture media, the concentration of which increased with the time of culture.

CONCLUSION

These results indicate that TGF beta-1 did not change greatly, if any, the yield of the first meiotic division but likely enhanced a bottleneck at the level of metaphase II. Taken together, our results suggest strongly that TGF beta participates in an auto/paracrine pathway of regulation of the meiotic differentiation of rat spermatocytes.

Disrupted expression of intermediate filaments in the testis of rhesus monkey after experimental cryptorchidism

Cytoskeletons in Sertoli cell play an important role in process of spermatogenesis. The expression and distribution of the intermediate filaments, vimentin, keratin and desmin, were studied in the Sertoli cells of the cryptorchid testis of rhesus monkey. Vimentin was localized in the perinuclear region of Sertoli cells of the normal testis. An intense increase in vimentin immunoreactivity was observed with appearance of disorganized staining in the Sertoli cells of the cryptorchid testes. Cytokeratin 18, a marker of immature Sertoli cells, re-expressed in the cells of the adult cryptorchid testes. Desmin was also observed in the Sertoli cells in addition to the peritubular myoid cells on 30 days after the cryptorchid operation. These data suggest that Sertoli cells in primate can be affected by the heat stress. The altered changes in intermediate filaments could be possible to induce the Sertoli cell functional changes that would partially contribute to the germ cell apoptosis leading to azoospermia or oligozoospermia.

Serum reproductive hormone levels and sperm production in male adult rats after treatment with arresting, a fraction obtained from seminiferous tubules conditioned medium

This study used seminiferous tubule (ST) segments from adult rats to condition culture medium that had been concentrated, size fractioned and administered 10-84 days to adult rats by subcutaneous or intratesticular injection and the effects on testes weight, testosterone, luteinizing hormone (LH) and FSH levels and (homogenization-resistant) epididymal sperm count were determined. The conditioned medium obtained 2 days after culture of ST was fractionated in a 30-100 kDa component. The fraction was injected subcutaneously or intratesticularly. This factor(s), named arresting, decreases sperm count in the epididymis from 13 days to 84 days of treatment without changes in serum LH or testosterone levels. The results of the present study suggest that arresting acts on spermiogenesis/spermiation and/or the entry of sperm into the epididymis from the efferent ductules.