Histomorphometric study on germ cell differentiation of unilateral cryptorchidism in the immature pig.

Early spermatogenesis from gonocytes to A-type spermatogonia is inhibited in boys with cryptorchidism. Histological lesions in the undescended testes (UDT) are presumably secondary to the extrascrotal position. The purpose of this study is to determine the abnormalities in number and maturation of germ cells in pigs with undescended testes and to examine the effect of UDT location on early germ cell differentiation. Testicular biopsies from 4-week-old pigs with natural unilateral cryptorchidism (n = 20) were divided into three groups: (1) intraabdominal testes, (2) superficial inguinal pouch testes, and (3) contralateral descended testes (CDT). The testis weight (P < .01) and the area of circular cross-section of the seminiferous tubules (P < .05) in intraabdominal testes was lower than in CDT. The number of germ cells (per tubular cross-section) (P < .05) and A-type spermatogonia (P < .05) in intraabdominal and inguinal testes was significantly lower than in CDT. In contrast, the number of gonocytes in intraabdominal testes was similar to that in CDT. The number of Sertoli cells was similar in the three groups. These results demonstrate that defective transformation of gonocytes to A-type spermatogonia in pigs is similar to that observed in boys with unilateral cryptorchidism. The different locations of UDT in the pig are correlated with the degree of impaired spermatogenesis.