Comparison of the ultrastructure of the cremasteric muscle‐scrotal interface in normal and cryptorchid rats following division of the neonatal genitofemoral nerve

Abstract

AbstractThe gubernaculum, innervated by the genital branch of the genitofemoral nerve, plays an important role in inguinoscrotal testicular descent. Cremaster muscle develops within the gubernaculum, and it has been demonstrated that an intact nerve is essential for gubernacular migration and scrotal pouch formation. In this electron microscopy study, we investigated the relationship between the gubernaculum, cremaster muscle, and the developing scrotum in normal rats and rats rendered cryptorchid by genitofemoral nerve division.In 12 neonatal rats, the genitofemural nerve was divided unilaterally. Rats were sacrificed at 2, 4, 7, 10, 14, and 18 days (n = 2 for each group), and sagittal sections through the cremaster muscle‐scrotal interface evaluated with transmission electron microscopy. These were compared to non‐operated control animals sacrificed at 0, 2, 4, 7, 10, 14, and 18 days (n = 2 for each group). We observed the following changes in the cremaster muscle of the operated group compared to unoperated controls: (1) an increase in the number of immature muscle fibers; (2) variable muscle fiber size; (3) disorganization of internal structures; and (4) vacuolization within the muscle fibers. There were no demonstrable ultrastructural interface or scrotal ligament differences between the operated and unoperated specimens.This study suggests that architecturally normal early gubernacular and cremaster muscle growth is dependent on an intact genitofemoral nerve. The poor scrotal growth seen without genitofemoral nerve input may be due to attachment of the scrotal ligament in an ectopic location in combination with abnormal cremaster muscle development. © 1994 Wiley‐Liss, Inc.