Figure 1.

Loss of SSCs during 9 Days of Inhibited GDNF Signaling and Their Partial Restoration 2 Months after Signaling Resumes

Adult, Ret V805A^+/+, Rosa 26^+/−, ID4-eGFP^+/− mice were injected for 9 days with vehicle (control) or with 1NA-PP1 (treated). Quantitative data are presented as mean + SEM. An asterisk indicates that treated mice differ from controls (p < 0.05).

(A) The effects of inhibition of GDNF signaling on numbers of transplantable SSCs. Two to 4 days after the last injection, germ cells from each animal were transplanted into testes of germ cell-deficient mice. Germ cells from treated and control mice were transplanted into 17 and 16 testes, respectively, and LacZ⁺ germ cell colonies per testis enumerated 2 months later. Data are presented as number of colonies per 10⁶ transplanted cells per testis.

(B) Fraction of tubule cross-sections in control and treated animals were classified as exhibiting normal spermatogenesis, incomplete spermatogenesis, or Sertoli cell-only (SCO) syndrome. Testes were collected 2 months after the last injection, 1 μm testis cross-sections were prepared and each tubule classified. Data (n = 3/group) are presented as fraction of tubule cross-sections per classification per testis.

(C–E). Confocal micrographs of GFRα1⁺ (red), ID4-eGFP⁺ (green) spermatogonia in tubules of control and treated mice. The two boxes on the right side of an image separate red and green channels of the left hand box. Scale bars, 40 μm. (C) Image from a control animal. (D) Image from an animal that was analyzed 2–4 days after the last injection 1NaPP1. Similar images were obtained for 75% of the surface of tubules collected 2 months after treatment. (E) The remaining 25% contained clusters of GFRα1⁺, ID4-eGFP⁺ spermatogonia.

(F) Numbers of GFRα1⁺, ID4-eGFP⁺ spermatogonia/mm² of tubule surface for control (n = 5) and treated mice analyzed 2–4 days or 2 months (n = 3/group) after the last injection.