Growth of the rat gubernaculum in vitro and localisation of its growth centre.
OBJECTIVE
Recent studies suggest that testicular descent is accomplished by outgrowth of the gubernaculum from the abdominal wall. The tip of the gubernaculum has been proposed as the primary site of growth, similar to an embryonic limb bud. We aimed to determine the maximum site of growth in organ culture.


METHODS
Gubernacula from 1-day-old Sprague-Dawley rats (n = 40) were collected and divided into 4 groups as follows: whole gubernaculum (control), truncated gubernaculum (tip excised), gubernacular tip alone, and grafted gubernaculum with an extra tip on its side. Tissues were cultured with or without calcitonin gene-related peptide (CGRP) (714nmol/L) in medium for 24 hours. The area of each gubernaculum was determined by "Image J" analysis of digital photos collected via a Leica Wild M28 microscope (Leica Microsystems, Wetzler GmbH Germany) taken before and after culture.


RESULTS
In organ culture, the neonatal rat gubernaculum normally shrank 10% to 15%, but this was prevented by the presence of exogenous CGRP (0.8% vs 11.8%; P < .003). By contrast, gubernacula with their tips excised were not affected by CGRP (3.4% vs 4.7%; not significant). Gubernacular tips alone did respond to CGRP (2.7% vs 13.5%; P < .03). Transplantation of the tip to another gubernaculum caused it to develop 2 tips.


CONCLUSIONS
These results suggest that the rat gubernaculum contains a growth centre in its distal tip that can respond to CGRP. This is consistent with a limb bud model of gubernacular growth during the inguinoscrotal descent of the testis.
Ng
Yang Hwa
YH
Douglas Stephens Surgical Research Unit, Murdoch Childrens Research Institute, Melbourne, Victoria 3052, Australia.
Farmer
Pamela J
PJ
Sourial
Magdy
M
Southwell
Bridget R
BR
Hutson
John M
JM
D000818:Animals; D000831:Animals, Newborn; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D008297:Male; D009924:Organ Culture Techniques; D010537:Peritoneum / Q000187:drug effects / Q000254:growth & development*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013737:Testis / Q000187:drug effects / Q000254:growth & development
D015740:Calcitonin Gene-Related Peptide