Hoxa-11 maintains cell proliferation in the mouse gubernaculum to facilitate testicular descent

The gubernaculum is a structure vital for guiding testicular descent. The Homeobox gene, Hoxa-11, is involved in patterning embryonic structures and is necessary for gubernacular development, as Hoxa-11 knock-out mice exhibit abnormal gubernacula and undescended testes. We aimed to elucidate how testicular descent fails by examining cell proliferation and androgen receptor (AR) expression in Hoxa-11 KO mice gubernacula.

Postnatal day 2 wild type (n=6) and Hoxa-11 KO mice (n=6), were prepared for immunohistochemistry and confocal microscopy using antibodies against androgen receptor, slow skeletal myosin (My32), and Ki67, a marker of cell proliferation.

The gubernacula of Hoxa-11 KO mice were hypocellular compared with WT. AR was present in the gubernaculum and abutting inguinal fat pad in both WT and Hoxa-11 KO with no difference in expression. Slow skeletal myosin was present in a clear 'swirl' in the growth centre of WT animals which was absent in the Hoxa-11 KO mice. Ki67, expressed in the growth centre and cremaster muscle in WT, was greatly decreased in Hoxa-11 KO.

Hoxa-11 may regulate fibroblast proliferation in the gubernaculum, as it does in human uterosacral ligaments, allowing formation of the 'growth centre' within the bulb and facilitating myogenesis and elongation to the scrotum. Polymorphisms in Hoxa-11 may contribute to the aetiology of human cryptorchidism.