Recombinant Human Insulin-Like Growth Factor I Stimulates All Stages of 11-Ketotestosterone-Induced Spermatogenesis in the Japanese Eel, Anguilla japonica, In Vitro1

Abstract

In this study, we examined the in vitro effects of insulin-like growth factor I (IGF-I) in the presence or absence of 11-ketotestosterone (11-KT: the spermatogenesis-inducing hormone) on the proliferation of Japanese eel (Anguilla japonica) testicular germ cells. Initially, a short-term culture (15 days) of testicular tissue with only type A and early type B spermatogonia (preproliferated spermatogonia) was carried out in Leibovitz-15 growth medium supplemented with different concentrations of recombinant human IGF (rhIGF)-I or -II in the presence or absence of 10 ng/ml of 11-KT. Late type B spermatogonia (proliferated spermatogonia) were observed in treatments of 100 ng/ml of both rhIGF-I and -II in combination with 11-KT, indicating the onset and progression of spermatogenesis. In all tested rhIGF-I concentrations (except 0.1 ng/ml) supplemented with 11-KT, late type B spermatogonia were detected in at least one individual. Then, we proceeded with an in vitro 45-day culture of testicular tissue with 100 ng/ml of rhIGF-I in the presence or absence of 10 ng/ml of 11-KT to test the long-term effects of rhIGF-I on the spermatogenetic cycle. The presence of all types of germ cells, including spermatozoa, in the testis cultured with the admixture of the two hormones indicated that the germ cells underwent complete spermatogenesis whereas no germ cell proliferation was observed when the rhIGF-I was applied alone. These results suggest that IGF-I in the presence of 11-KT plays an essential role in the onset, progress, and regulation of spermatogenesis in the testis of the Japanese eel.

Ethinylestradiol differentially interferes with IGF-I in liver and extrahepatic sites during development of male and female bony fish

“…In Japanese eel cultured testes, IGF-I stimulated spermatogenesis induced by 11-ketosterone (Nader et al 1999). In rainbow trout, testicular IGF-I increased after GH treatment (Le Gac et al 1996, Biga et al 2004 and both GH and IGF-I stimulated the incorporation of thymidine into spermatogonia and primary spermatocytes (Loir 1999).…”

Evolutionary ecology of endocrine‐mediated life‐history variation in the garter snake Thamnophis elegans

“…Whether most males reproduce every year and how their reproductive effort varies with age/body size is unknown. We do know, however, that IGF-1 stimulates spermatogenesis, and that testis size tends to increase with body size in many ectotherms (Baker et al 1996, Shine et al 1998, Nader et al 1999, Skinner and Watt 2007. Such an increase in IGF-1 with size suggests that males may also exhibit size-specific changes in reproductive investment.…”

Spermatogenesis in testis primary cell cultures of the tilapia (Oreochromis niloticus)

“…evidence from other authors (Loir and Le Gac, 1994;Nader et al, 1999) suggest that 11-KT is necessary for the induction of spermatogenesis, whereas IGF is necessary for the continuation of the process.…”

“…Of interest, the arrest can be relieved by IGF or hCG. IGF is known to induce DNA synthesis in a broad array of cell types (Pestell et al, 1999) and plays an essential supporting role in allowing germ cells to proceed through spermatogenesis (Nader et al, 1999). IGF may be produced by different cell types, and the action may be endocrine (produced in the liver and transported by the blood stream), paracrine (somatic cells to germ cells), or autocrine (germ cells to germ cells).…”