Mechanisms Underlying Testicular Damage and Dysfunction in Mice With Partial IGF-1 Deficiency and the Effectiveness of IGF-1 Replacement Therapy.

OBJECTIVE: To determine whether insulin-like growth factor (IGF-1) deficiency can cause testicular damage and to examine changes of the testicular morphology and testicular function-related gene expression caused by IGF-1 deficiency. Therefore, this study aims to determine the benefits of low doses of IGF-1 and to explore the mechanisms underlying the IGF-1 replacement therapy. MATERIALS AND METHODS: A murine model of IGF-1 deficiency was used to avoid any factor that could contribute to testicular damage. Testicular weight, score of histopathological damage, and gene expressions were studied in 3 experimental groups of mice: controls (wild-type Igf1(+/+)), heterozygous Igf1(+/-) with partial IGF-1 deficiency, and heterozygous Igf1(+/-) treated with IGF-1. RESULTS: Results show that the partial IGF-1 deficiency induced testicular damage and altered expression of genes involved in IGF-1 and growth hormone signaling and regulation, testicular hormonal function, extracellular matrix establishment and its regulation, angiogenesis, fibrogenesis, inflammation, and cytoprotection. In addition, proteins involved in tight junction expression were found to be reduced. However, low doses of IGF-1 restored the testicular damage and most of these parameters. CONCLUSION: IGF-1 deficiency caused the damage of the blood-testis barrier and testicular structure and induced the abnormal testicular function-related gene expressions. However, low doses of IGF-1 constitute an effective replacement therapy that restores the described testicular damage. Data herein show that (1) cytoprotective activities of IGF-1 seem to be mediated by heat shock proteins and that (2) connective tissue growth factor could play a relevant role together with IGF-1 in the extracellular matrix establishment.

Identification of multiple claudins in the rat epididymis.

The luminal environment of the epididymis is highly specialized with specific proteins, ions, pH, etc. required for sperm maturation. Tight junctions between epididymal principal cells are responsible for the formation of the blood-epididymal barrier, which regulates this luminal environment. Claudins (Cldns) are a recently discovered family of transmembrane proteins and are essential components of tight junctions. Previous work from our laboratory has demonstrated the presence and localization of Cldn-1 in all regions of the rat epididymis. The objective of this study was to determine the presence and localization of other Cldns in the epididymis. Using RT-PCR we have identified mRNA transcripts for Cldn-3 through -9 in each region of the adult rat epididymis. Immunolocalization of Cldn-3, Cldn-4, and Cldn-5 were done in adult as well as in 42- and 14-day-old rats. Cldn-5 in adult rats was localized exclusively in blood vessels of the interstitium. Cldn-3 was localized apically in the epididymal epithelium between adjacent principal cells throughout the epididymis, where tight junctions have been reported histologically. There were no differences in the localization of Cldn-3 in epididymides of rats at the different ages. In 14-day-old rats, Cldn-4 was localized all along the lateral plasma membrane between adjacent principal cells. The immunostaining was more pronounced in the proximal regions of the epididymis. In both 42-day-old rats and adults, Cldn-4 was localized primarily to apical tight junctions between principal cells and staining was more pronounced in the proximal region of the epididymis. Cldn-16 transcripts were also identified by RT-PCR. These transcripts were present in both proximal and distal regions of the epididymis of young (Day 14 and 21) animals, but only in the proximal (initial segment) region of the adult epididymis. These data indicate that epididymal tight junctions are composed of several Cldns, suggestive of a complex regulation of the blood-epididymal barrier.

The distribution of drug-efflux pumps, P-gp, BCRP, MRP1 and MRP2, in the normal blood-testis barrier and in primary testicular tumours.

The drug-efflux pumps P-glycoprotein (P-gp) and multidrug resistance-associated protein 1 (MRP1) are present in the blood-testis barrier (BTB) and may hamper the delivery of cytotoxic drugs to the testis. The precise localisation of P-gp and MRP1 in testicular tissue and the presence of the efflux pumps MRP2 and breast cancer resistance protein (BCRP) in the BTB are unknown. We therefore studied the localisation of these pumps in the BTB in normal testis (n = 12), in non-seminoma (n = 10) seminoma (n = 10), and testicular lymphoma (n = 9). Slides were scored semi-quantitatively for P-gp, MRP1, MRP2 and BCRP and blood vessels with factor VIII antibody. In normal testis, P-gp and BCRP were strongly expressed by myoid cells and luminal capillary endothelial wall and P-gp also by Leydig cells. MRP1 was observed at the basal side of Sertoli cells and on Leydig cells. MRP2 was only weakly expressed by myoid cells. Seminomas and non-seminomas expressed P-gp and/or BCRP and/or MRP1, lymphomas strongly expressed P-gp, weakly expressed BCRP and did not or showed weak expression of MRP1. There was very little staining for MRP2 in the tumours. Newly formed vessels in all tumours only expressed P-gp and BCRP. P-gp, BCRP and MRP1 are present in different cell layers of the normal testis, suggesting the optimal protection of spermatogenesis. In germ cell tumours, this expression pattern may explain the chemoresistance observed to P-gp, BCRP and MRP1 substrates. In germ cell tumours and testicular lymphomas, P-gp and BCRP expression by tumour cells and by newly formed vessels may also contribute to chemoresistance. These findings underscore the importance of removing the affected testis in cases of primary germ cell tumours and testicular lymphomas, irrespective of whether the patient has already undergone chemotherapy.