Insulin 3-like hormone and its role epididymo-testicular descent

Abstract

Purpose: The role of insulin 3-like (Ins13) hormone signaling in the testicular descent process has been demonstrated. The purpose of the present study was to evaluate epididymal development in Ins13-deficient mice. Materials and Methods: Heterozygous and homozygous Ins13 mutants of a mixed CD1 X 129/Sv genetic background were generated by breeding Ins13-/- females with Ins13+/- males, and their genotypes were determined by polymerase chain reaction. On the first postnatal day, newborn males were sacrificed, embedded in paraffin, and cut in 4 μm sections. Sections were stained with hematoxylin/eosin and immunoreacted with anti-α actin antibody. Results: An analysis of stained sections indicated an arrest in the development of the epididymis in all homozygous mice. The cauda and corpus of the epididymis were undersized. Compared to the heterozygous epididymis, the homozygous epididymis had fewer peritubular layers and dwarfish musculature. We confirmed this with immunostaining with monoclonal antibodies against (-smooth muscle actin. Conclusion: Defective development of the smooth musculature in the epididymis of Ins13 homozygous mutant mice, combined with its high intraabdominal undescended position, supports previous observations regarding the importance of intact epididymis morphology and function for descent of the epididymo-testicular unit.