The role of RXFP2 in mediating androgen-induced inguinoscrotal testis descent in LH receptor knockout mice

Abstract

LH receptor knockout (LhrKO) male mice exhibit a bilateral cryptorchidism resulting from a developmental defect in the gubernaculum during the inguinoscrotal phase of testis descent, which is corrected by testosterone replacement therapy (TRT).In vivoandin vitroexperiments were conducted to investigate the roles of the androgen receptor (AR) and RXFP2 signals in regulation of gubernacular development inLhrKO animals. This study demonstrated that AR and RXFP2 proteins were expressed in the gubernaculum during the entire postnatal period. TRT normalized gubernacular RXFP2 protein levels inLhrKO mice. Organ and primary cell cultures of gubernacula showed that 5α-dihydrotestosterone (DHT) upregulated the expression ofRxfp2which was abolished by the addition of an AR antagonist, flutamide. A single s.c. testosterone injection also led to a significant increase inRxfp2mRNA levels in a time-dependent fashion inLhrKO animals. DHT, natural and synthetic insulin-like peptide 3 (INSL3), or relaxin alone did not affect proliferation of gubernacular mesenchymal cells, while co-treatments of DHT with either INSL3 or relaxin resulted in an increase in cell proliferation, and they also enhanced the mesenchymal cell differentiation toward the myogenic pathway, which included a decrease in a mesenchymal cell marker, CD44 and the expression of troponin. These effects were attenuated by the addition of flutamide, siRNA-mediatedRxfp2knockdown, or by an INSL3 antagonist. Co-administration of an INSL3 antagonist curtailed TRT-induced inguinoscrotal testis descent inLhrKO mice. Our findings indicate that the RXFP2 signaling pathway plays an important role in mediating androgen action to stimulate gubernaculum development during inguinoscrotal testis descent.