Background: Vitamin D3 has been well characterized as an essential regulator of bone and mineral homeostasis. Recent evidence has showed that acting through vitamin D receptor (VDR), vitamin D can produce a wide array of favorable biological effects on reproductive health. According to very recent report, VDR and vitamin D metabolizing enzymes are constitutively expressed in human male reproductive tract indicating eminent role of this hormone in spermatogenesis and maturation of human sperm. No evidence, however, is available to what extent VDR is expressed in testis tissue of abnormal spermatogenesis.
Methods: Study population included non-obstructive azospermic men referred to infertility clinic. After testis biopsy for assisted reproduction, a small portion of tissue was examined for VDR expression by semi-quantitative nested RT PCR and immunohistochemiostry. Quantitative measurement of VDR protein in immunostained tissues was performed using ImageJ image analysis software. In order to investigate potential systemic difference, VDR-specific message was also screened in peripheral blood mononuclear cells (PBMC) of the subjects by conventional RT PCR method.
Results: According to histopathology evaluation, patients were categorized in to the four groups, namely, sertoli cell only, hypospermatogenesis, maturation arrest and immature testis. VDR-specific message was equally expressed by PBMC of all groups. At the tissue level, however, VDR expression was differentially regulated at different study population. Immunohistochemical analysis revealed that there are considerable differences of VDR expression in groups under investigation in terms of immunolocalization, total expression and expression scoring as judged by image analysis. Interestingly, different cell population in patients of various category exhibited unequal or even contrasting immunostaining pattern.
Conclusion: To our best knowledge, this the first report on VDR gene and protein profiling in testicular tissue of azospermic males. Based on the results of this project, we propose that vitamin D system homeostasis is differentially regulated in disorders of spermatogenesis pointing to possible involvement of this system on the process of sperm maturation.