Enhanced Expression of Tyrosine Kinase Receptor A in Germ Cells of Rat Testis with Acute Experimental Testicular Torsion

Morpho-Functional Features of the Gonads of Danio rerio: the Role of Brain-Derived Neurotrophic Factor

Zebrafish, a suitable and widely used teleost fish model in basic biomedical research, displays morphophysiological features of adult gonads that share some commonalities with those of mammalian species. In mammals, gametogenesis is regulated, among several factors, by brain-derived neurotrophic factor (BDNF). This neurotrophin has a well-established role in the developing and adult nervous system, as well as gonads development and functions in vertebrate species. We hypothesize that BDNF has a role also in the gonadal functions of zebrafish. At this purpose, we investigated BDNF and its receptors p75 and TrkB in the ovary and testis of adult zebrafish, kept under laboratory conditions. Our results display (1) the expression of BDNF mRNA and pro-BDNF protein outside of the nervous system, specifically in the ovary and testis; (2) the presence of pro-BDNF in primary oocytes and follicular layer, and p75 in follicular cells; (3) the localization of pro-BDNF in type B spermatogonia, and Sertoli cells in testis. Altogether, these data lead us to consider that BDNF is involved in the gonadal function of adult zebrafish, and mainly in the adult ovary. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 301:140-147, 2018. © 2017 Wiley Periodicals, Inc.

The potential roles of neurotrophins in male reproduction

Neurotrophins are a family of polypeptide growth factors that are required for the proliferation, differentiation, survival, and death of neuronal cells. A growing body of evidence suggests that they may have broader physiological roles in various non-neuronal tissues. The testicles are complex non-neuronal organs in which diverse cell types interact to achieve correct spermatogenesis. Both neurotrophins and their receptors have been detected in various cell types from mammalian testes, suggesting that neurotrophins may regulate or mediate intercellular communication within this organ. This review summarizes the existing data on the cellular distribution and possible biological roles of neurotrophins in the testes. The data reported in the literature indicate that neurotrophins affect somatic cell growth and spermatogenesis and imply that they play a role in regulating testicular development and male reproduction.

Expression of CD44 adhesion molecule in rat testis with ischemia/reperfusion injury

The expression pattern of CD44 was studied in the rat testis following ischemia/reperfusion (I/R) injury to elucidate the possible role of the CD44 adhesion molecule in acute experimental testicular torsion. Western blot analysis showed that CD44 expression began to increase significantly 24 hr after reperfusion, compared with the normal control; the increased expression persisted until 96 hr after I/R. Immunohistochemistry showed that, in the normal testis, CD44 was constitutively expressed mainly in ED2-positive resident macrophages in the interstitial space. After I/R, the majority of inflammatory cells in the interstitial space surrounding the damaged tubules were ED1-positive macrophages that were CD44-positive. These findings suggest that the significant increase in CD44 expression that occurs during the delayed phase after reperfusion originates from infiltrating macrophages possibly in anticipation of the migration and adhesion of additional macrophages into the affected testis.

Effects of increased nerve growth factor plasma levels on the expression of TrkA and p75 in rat testicles

In addition to their well-known roles within the nervous system, the neurotrophins and their receptors regulate some functions in the reproductive system. In this study we used combined morphological and immunohistochemical techniques to investigate the presence and cellular localization in the rat testicle of the two receptors of nerve growth factor (NGF), i.e. TrkA and p75(NTR). Furthermore, to evaluate whether increased plasma levels of NGF affect the ageing process, 4-methylcathechol (4-MC), an inductor of NGF synthesis, was administered. Both TrkA and p75(NTR) were expressed in rat testicles, but the pattern and intensity of immunoreaction were marginally different between them. In adult rats TrkA was expressed in spermatozoa and spermatids, and p75 was expressed in spermatogonia. In newborn rats TrkA immunoreactivity was found in the Leydig cells, whereas p75 was detected in a cellular layer that surrounds the seminiferous tubules. In adult treated animals the immunoreaction for TrkA and p75(NTR) was also localized in the spermatocytes, whereas in newborn treated rats no changes in the pattern of immunoreaction was observed. The present findings suggest a role of the NGF/TrkA/p75 system in the physiology of reproduction, but the practical relevance of this remains to be established.