Abnormal germ cell development in cryptorchidism

Background: Previous studies suggest that two fundamental, probably androge n-dependent, steps in maturation of germ cells normally occur in the prepub ertal testis: the disappearance of gonocytes (the fetal stem cell pool) and the appearance of adult dark spermatogonia (the adult stem cell pool) at 2 -3 months of age and the appearance of primary spermatocytes (the onset of meiosis) at 4-5 years. Previous studies of small series of cryptorchid boys suggest that both steps are defective in undescended testes and to a lesse r degree in descended testes contralateral to unilaterally undescended test es. The purpose of this study is to confirm the previous findings of defect ive germ cell maturation in a large series of boys with unilateral undescen ded testes. Patients: Seven hundred and sixty-seven boys with unilateral cr yptorchidism who had orchidopexy and bilateral testicular biopsies between birth and 9 years of age were studied. Materials and Methods: Total and dif ferential germ cell counts were performed on semithin histologic sections o f the biopsies. The results from the undescended and contralateral descende d testes were compared using the Wilcoxon signed-rank test and the Wilcoxon -Whitney-Mann U test. Results: Gonocytes failed to disappear and adult dark spermatogonia failed to appear in undescended testes under 1 year of age i ndicating a defect in the fi rst step in maturation at 2-3 months resulting in failure to establish an adequate adult stem cell pool. Primary spermato cytes failed to appear in undescended testes and appeared in only 19% of co ntralateral descended testes at 4-5 years of age indicating a defect in the onset of meiosis. Conclusion: Unilaterally undescended testes fail to esta blish an adequate adult stem cell pool which normally occurs at 2-3 months of age and fail to establish adequate meiosis which normally occurs at 4-5 years of age. Similar but less severe changes are seen in the contralateral descended testes. Defects in the two pubertal steps in germ cell maturatio n are associated with reduced total germ cell counts. Copyright (C) 2001 S. Karger AG, Basel.