Testis

Peroxisomes in Human and Mouse Testis: Differential Expression of Peroxisomal Proteins in Germ Cells and Distinct Somatic Cell Types of the Testis

Abstract
The vital importance of peroxisomal metabolism for regular function of the testis is stressed by the severe spermatogenesis defects induced by peroxisomal dysfunction. However, only sparse information is available on the role and enzyme composition of this organelle in distinct cell types of the testis. In the present study, we characterized the peroxisomal compartment in human and mouse testis, in primary cultures of murine somatic cells (Sertoli-, peritubular myoid-, and Leydig cells) and in GFP-PTS1 transgenic mice with a variety of morphological and biochemical techniques. Formerly, peroxisomes were thought to be absent in late stages of spermatogenesis. However, our results obtained by detection of different peroxisomal marker proteins show the presence of these organelles in most cell types in the testis except for mature spermatozoa. Furthermore, we demonstrate a strong heterogeneity of peroxisomal protein content in various cell types of the human and mouse testis and show marked differences in structure, abundance and localization of these organelles in spermatids depending on their maturation. Highest and selective enrichment of the peroxisomal lipid transporters (ABCD1 and ABCD3) as well as ACOX2, the key regulatory enzyme of the beta-oxidation pathway 2 for side-chain oxidation of cholesterol was found in Sertoli cells, whereas Leydig cells were enriched in catalase and ABCD2. Our results suggest a cell type-specific metabolic function of peroxisomes in the testis and point to an important role of peroxisomes in spermiogenesis and in the lipid metabolism of Sertoli cells.

Key words: Testis • Leydig cells • Sertoli cells • Spermatid • Spermatogenesis