Leydig insulin-like hormone, gubebnacular development and testicular descent

Purpose: Testicular descent is controlled by 2 morphological and hormonal s teps. Transabdominal testicular descent is mediated by gubernacular swellin g and regression of the cranial suspensory ligament. Mullerian inhibiting s ubstance (MIS) has been proposed to stimulate the swelling but this remains controversial. Recently, a mouse mutant for Leydig insulin-like hormone (I nsl3) was found to have undescended testis and deficient gubernaculum. We e xamine the testicular position of Insl3 mutant mice and the development of gubernacula. Materials and Methods: Mice with Insl3 homozygotes (-/-), heterozygotes (+/ -) and wild-types (+/+) were examined at embryonic day 16.5 and birth. Macr oscopic dissections and measurements of the testicular position, as well as microscopic analysis (hematoxylin and eosin, and Masson's trichrome) were performed. Results: Of the mice 11 Ins13 homozygote males had significantly impaired t esticular descent at embryonic day 16.5 and birth (p <0.01), and the cord w as thin and elongated, while 14 heterozygotes and 7 wild-types had normal t esticular descent. Microscopically, the gubernaculum of Ins13 homozygotes w as small with some muscle development but no central core of mesenchyme at embryonic day 16.5. On the ether hand, heterozygotes and wild-types had nor mal gubernacular development with a swelling reaction. Conclusions: Insl3 mutants show feminized gubernaculum with deficient mesen chymal core. Insl3 appears to have some role in the gubernacular swelling r eaction in mice.