The anatomy of the cremaster muscle during inguinoscrotal testicular descent in the rat.
BACKGROUND
Extrapolation of rat testicular descent studies to humans has been criticized because of anatomical differences of the cremaster muscle. Human cremaster is described as a thin strip rather than a large, complete sac as in rats, which is proposed to be more important in propelling the testis during descent. This study investigated cremaster muscle anatomy and ontogeny in both normal and cryptorchid rat models.


METHODS
Gubernacula from 4 groups of neonatal rats were sectioned longitudinally and transversely: normal Sprague-Dawley, capsaicin pretreated, flutamide pretreated, and congenital cryptorchid rats. Gubernacula were stained with hematoxylin-eosin, Masson trichrome, and desmin immunohistochemistry to study muscle development.


RESULTS
Myoblasts are more numerous at the gubernacular tip, whereas the most differentiated muscle is proximal. Rat cremaster develops as an elongated strip rather than a complete sac derived from abdominal wall muscles. Flutamide and capsaicin pretreatment disrupts development.


CONCLUSIONS
Rat cremaster muscle develops as a strip, bearing close resemblance to human cremaster muscle, permitting extrapolation of cremaster function to human testicular descent. The cremaster muscle appears to differentiate from the gubernacular tip during elongation to the scrotum, and requires intact sensory innervation and androgen.
Harnaen
Efrant J
EJ
F. Douglas Stephens Surgical Research Laboratory, Murdoch Childrens Research Institute, Melbourne, Australia.
Na
Angelika F
AF
Shenker
Natalie S
NS
Sourial
Magdy
M
Farmer
Pamela J
PJ
Southwell
Bridget R
BR
Hutson
John M
JM
D000009:Abdominal Muscles / Q000033:anatomy & histology / Q000254:growth & development; D000818:Animals; D000831:Animals, Newborn; D003456:Cryptorchidism; D004195:Disease Models, Animal; D005260:Female; D005485:Flutamide / Q000494:pharmacology; D007264:Inguinal Canal / Q000033:anatomy & histology / Q000254:growth & development; D008297:Male; D011247:Pregnancy; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012611:Scrotum / Q000033:anatomy & histology / Q000196:embryology / Q000254:growth & development; D012680:Sensitivity and Specificity; D013085:Spermatic Cord / Q000033:anatomy & histology* / Q000196:embryology / Q000254:growth & development; D013737:Testis / Q000033:anatomy & histology* / Q000196:embryology / Q000254:growth & development
D005485:Flutamide