Expression and role of leptin under hypoxic conditions in human testis: organotypic in vitro culture experiment and clinical study on patients with varicocele.

Abstract

We investigated the expression and the exact role of leptin under hypoxic conditions in the human testis. Five testes from patients treated with orchiectomy for prostate cancer were used to construct an in vitro hypoxic culture system for human testicular tissue. Immunohistochemistry was performed to analyze leptin protein expression. Leptin, leptin receptor and HIF-1α mRNA were examined by quantitative reverse transcriptase-polymerase chain reaction. Serum and seminal plasma leptin, gonadal hormones and semen parameters were evaluated in 10 healthy donors and 42 infertile patients with varicocele before and after surgery. The viability of in vitro cultured testicular tissue was well maintained within 48 hours based on the results of morphological analysis, cell number and cell specific mRNAs. Immunohistochemistry demonstrated that leptin was mainly expressed in seminiferous tubules. Interestingly the optical density of leptin, leptin mRNA and HIF-1α mRNA was significantly increased under hypoxia. Leptin mRNA and HIF-1α mRNA correlated positively (Rs = 0.843, p <0.01). In the clinical study the concentration of seminal plasma leptin before varicocelectomy was markedly higher in patients (mean ± SD 3.01 ± 1.23 ng/l, p <0.01). It was highest in the grade 3 group (mean 3.95 ± 1.37 ng/l, p <0.01) and significantly decreased in the 6-month postoperative group (2.35 ± 0.78, p <0.05). Furthermore, negative correlations were observed between seminal plasma leptin and the sperm concentration (Rs = -0.187, p <0.05), and progressive motility (Rs = -0.234, p <0.05). Leptin expression was induced under hypoxia in the human testis, probably via the HIF-1α related response pathway. Seminal plasma leptin closely correlated with varicocele related spermatogenesis dysfunction. It might effectively reflect the testicular hypoxic environment.