Changes in Gene Expression in Somatic Cells of Rat Testes Resulting from Hormonal Modulation and Radiation-Induced Germ Cell Depletion1

Abstract

Although gonadotropins and androgen are required for normal spermatogenesis and both testosterone and follicle-stimulating hormone (FSH) are responsible for the inhibition of spermatogonial differentiation that occurs in irradiated rats, it has been difficult to identify the specific genes involved. To study specific hormonally regulated changes in somatic cell gene expression in the testis that may be involved in these processes, without the complication of changing populations of germ cells, we used irradiated LBNF(1) rats, the testes of which contain almost exclusively somatic cells except for a few type A spermatogonia. Three different groups of these rats were treated with various combinations of gonadotropin-releasing hormone antagonist, an androgen receptor antagonist (flutamide), testosterone, and FSH, and we compared the gene expression levels 2 wk later to those of irradiated-only rats by microarray analysis. By dividing the gene expression patterns into three major patterns and 11 subpatterns, we successfully distinguished, in a single study, the genes that were specifically regulated by testosterone, by luteinizing hormone (LH), and by FSH from the large number of genes that were not hormonally regulated in the testis. We found that hormones produced more dramatic upregulation than downregulation of gene expression: Testosterone had the strongest upregulatory effect, LH had a modest but appreciable upregulatory effect, and FSH had a minor upregulatory effect. We also separately identified the somatic cell genes that were chronically upregulated by irradiation. Thus, the present study identified gene expression changes that may be responsible for hormonal action on somatic cells to support normal spermatogenesis and the hormone-mediated block in spermatogonial development after irradiation.

Spermatogonial behavior in rats during radiation-induced arrest and recovery after hormone suppression

“…Qualitatively, the level of KITL fluorescence in Sertoli cells appeared at least as high after irradiation as before, and quantitative results demonstrated no significant changes in KITL protein concentrations after hormone suppression of the irradiated rats. This is not inconsistent with previous in vivo observations using more precise microarray analyses of about a twofold increase in Kitl mRNA with irradiation, a 1.4-fold increase with testosterone suppression, but no effect of FSH (Zhou et al 2010). In another in vivo model, after induction of a block in A spermatogonial differentiation with a chemical hexanedione, there was a decrease in the proportion of Kitl mRNA in the membrane-bound form relative to the soluble form, indicating that KITL may be less able to stimulate spermatogonial differentiation (Blanchard et al 1998).…”

“…Thus, the concentrations of GDNF, which should inhibit differentiation, do not appear to be a primary cause of the block in spermatogonial differentiation in irradiated rats or its reversal with hormone suppression. Furthermore, analysis of the mRNAs for the GDNF co-receptors on spermatogonia shows that Gfra1 mRNA decreases after irradiation and Ret increases after hormone suppression (Zhou et al 2010), confirming that changes in the GDNF signaling system cannot be involved in the induction or reversal of the spermatogonial differentiation block.…”

“…Acyline, a GNRH-ant (obtained from National Institutes of Health-National Institute of Child Health and Human Development, Bethesda, Maryland, USA), was freshly prepared in sterile water before each use and a dose of 1.5 mg/kg was injected s.c. weekly for 6 weeks. Furthermore, to reduce action of residual intratesticular testosterone levels, these irradiated rats received four s.c. silastic implants (20 cm total length) containing flutamide (Sigma-Aldrich; Porter et al 2009, Zhou et al 2010. Additionally, to evaluate the effects of absence and Leydig cell factors, the Leydig cells were destroyed after a single i.p.…”

“…Gene expression profiles in the irradiated rats and irradiated rats with hormone suppression have also been analyzed (Zhou et al 2010(Zhou et al , 2011. In this study, we have extended the characterization of the kinetics and molecular events of spermatogonial differentiation in rats during spermatogenic recovery after testis irradiation and hormone suppression with a GNRH antagonist (GNRH-ant), using morphological (light and transmission electron microscopy) and stereological approaches and molecular markers (e.g., KIT).…”

Histomorphological Processes in the Testicular Tissue at Ionizing Radiation Exposure (Literature Review)

“…Нaми нaйдeнa paбoтa, в кoтopoй гoвopитcя o тoм, чтo cocтoяниe, нepeдкo вoзникaющee у пaциeнтoв пocлe химиoтepaпии, мoжeт пpoвoциpoвaть paзвитиe в ткaни ceмeнникoв oкиcлитeльнoгo cтpecca co cнижeниeм гopмoнaльнoй и peпpoдуктивнoй функции тecтикул [24,36]. Peзультaты иccлeдoвaний пoдтвepждaют ocoбoe знaчeниe эффeктoв paдиaции в oтнoшeнии cтepoидoгeнeзa в клeткaх Лeйдигa, являющихcя глaвным иcтoчникoм тecтocтepoнa [14], a тaкжe в oтнoшeнии мeхaнизмoв взaимoдeйcтвия лютeинизиpующeгo гopмoнa c peцeптopaми [41,50]. Aнaлиз литepaтуpы пoкaзaл, чтo дeфицит этoгo гopмoнa в пocлeдующeм oтpицaтeльнo cкaзывaeтcя нa пpoдукции мужcких пoлoвых гopмoнoв [35].…”