269. Optimal testicular size of donor and recipient for testicular germ cell transplantation in the bovine

Abstract

The maturity status of donor and recipient testis appears to be important in the efficiency of testicular germ cell transplantation. When neonatal mice were used as recipients, they show 9.4 times greater colonization and 4 times larger colony size than in the adult.1 The objective of this study in cattle was to investigate the effect of testicular maturity of donor and recipient calves on success of the testis cell transplant procedure. Testicular maturity was measured indirectly by scrotal circumference and donor testicular cells were enzymatically isolated from 8 Angus calves aged 5–7 months (scrotal circumference, SC of 18–22cm) and injected into both testes of 12 recipient calves aged 4–6 months (SC 15–21cm. Donor cells were labeled with the red fluorescent dye PKH26 then transferred into the rete testis under ultrasonographic guidance. Castration of recipients was performed 2–6 months following injection and then frozen sections were used to localize the PKH26 positive donor cells. Five sections from different 5 areas in each testis were prepared and 100 tubules were counted. In 15 of the 24 (63%) testes, PKH positive donor cells were identified. There was no correlation between colonization rate and maturity of donor animal testis for the range of testis sizes studied. Testis cells from donors of SC 18-20 cm or of SC 21-22 did not result in different number of recipient testis with positive cells (7/10 (70%) v. 8/14 (57%)) or the number of positive cells per testis (1.92 ± 0.67% v. 2.5 ± 1.01%). Recipient maturity (SC of 15–18 cm v. SC of 19–21 cm) had no effect on the colonization rate (7/11 (64%) v. 8/13 (62%)); however, there were significantly more positive cells per testis in less mature (SC of 15–18) recipients (3.18±1.21% v. 1.52 ± 0.64% P < 0.05)). In summary we have demonstrated successful testicular germ cell transplantation between calves and while donor testis cell age appeared to have little effect on the efficiency of colonization, less mature testis provided more suitable conditions for colonization. (1)Shinohara T, Orwig KE, Avarbock MR and Brinster RL. (2001) Remodeling of the postnatal mouse testis is accompanied by dramatic changes in stem cell number and niche accessibility. PNAS 98(11), 6186–6191.