Abstract
BackgroundTGF 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.MethodsIn 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.ResultsUnder 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.ConclusionThese 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.
Highlights
TGF beta and its receptors are present in both germ cells and somatic cells of the male gonad
Effects of TGFβ1 on the number and viability of total germ cells and somatic cells When about 3.105 purified pachytene spermatocytes (PS) were cocultured with about 3.105 Sertoli cells, both the number of total cells and their viability decreased slightly during the culture period, as expected [24]
On day 7, the percentages of cells, compared with day 1, were 79 ± 8 and 79 ± 10% (m ± SEM, n = 7) for controls and treated cells; the viabilities were 71 ± 4 and 69 ± 3%, respectively. Every day they were studied, the percentages of germinal cells and of somatic cells were similar in control and TGFβ1-treated cultures but the percentage of germ cells decreased during the culture, whereas that of somatic cells increased 1.3 fold
Summary
TGF beta and its receptors are present in both germ cells and somatic cells of the male gonad. 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. Use of culture systems associating spermatogenic cells and testicular somatic cells might be a valuable alternative to study the possible involvement of intratesticular factors such as the TGFβs on some step(s) of spermatogenesis. The kinetic of the meiotic process is similar in vivo and during the first week of culture [24,26,29] and round spermatids developed in vitro can produce normal offspring [30] Such culture systems have allowed to study some cellular aspects of the meiotic process [31] or of its regulation [32]. In the present work, we addressed the role of TGFβ1 on the completion of meiosis by rat pachytene spermatocytes cultured together with Sertoli cells
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