Granulocyte colony-stimulating factor (G-CSF) promotes spermatogenic regeneration from surviving spermatogonia after high-dose alkylating chemotherapy.

BACKGROUND: The lifesaving chemotherapy and radiation treatments that allow patients to survive cancer can also result in a lifetime of side-effects, including male infertility. Infertility in male cancer survivors is thought to primarily result from killing of the spermatogonial stem cells (SSCs) responsible for producing spermatozoa since SSCs turn over slowly and are thereby sensitive to antineoplastic therapies. We previously demonstrated that the cytokine granulocyte colony-stimulating factor (G-CSF) can preserve spermatogenesis after alkylating chemotherapy (busulfan). METHODS: Male mice were treated with G-CSF or controls before and/or after sterilizing busulfan treatment and evaluated immediately or 10-19 weeks later for effects on spermatogenesis. RESULTS: We demonstrated that the protective effect of G-CSF on spermatogenesis was stable for at least 19 weeks after chemotherapy, nearly twice as long as previously shown. Further, G-CSF treatment enhanced spermatogenic measures 10 weeks after treatment in the absence of a cytotoxic insult, suggesting G-CSF acts as a mitogen in steady-state spermatogenesis. In agreement with this conclusion, G-CSF treatment for 3 days before busulfan treatment exacerbated the loss of spermatogenesis observed with G-CSF alone. Reciprocally, spermatogenic recovery was modestly enhanced in mice treated with G-CSF for 4 days after busulfan. These results suggested that G-CSF promoted spermatogonial proliferation, leading to enhanced spermatogenic regeneration from surviving SSCs. Similarly, there was a significant increase in proportion of PLZF+ undifferentiated spermatogonia that were Ki67+ (proliferating) 1 day after G-CSF treatment. CONCLUSIONS: Together, these results clarify that G-CSF protects spermatogenesis after alkylating chemotherapy by stimulating proliferation of surviving spermatogonia, and indicate it may be useful as a retrospective fertility-restoring treatment.

Granulocyte colony-stimulating factor prevents loss of spermatogenesis after sterilizing busulfan chemotherapy.

OBJECTIVE: To determine whether granulocyte colony-stimulating factor (G-CSF) could prevent loss of spermatogenesis induced by busulfan chemotherapy via protection of undifferentiated spermatogonia, which might serve as an adjuvant approach to preserving male fertility among cancer patients. DESIGN: Laboratory animal study. SETTING: University. ANIMAL(S): Laboratory mice. INTERVENTION(S): Five-week-old mice were treated with a sterilizing busulfan dose and with 7 days of G-CSF or vehicle treatment and evaluated 10 weeks later (experiment 1) or 24 hours after treatment (experiment 2). MAIN OUTCOME MEASURE(S): Experiment 1: testis weights, epididymal sperm counts, testis histology. Experiment 2: PLZF immunofluorescent costaining with apoptotic markers. Molecular analysis of G-CSF receptor expression in undifferentiated spermatogonia. RESULT(S): Ten weeks after treatment, busulfan-treated mice that also received treatment with G-CSF exhibited significantly better recovery of spermatogenesis and epididymal sperm counts than animals receiving busulfan alone. G-CSF led to increased numbers of PLZF+ spermatogonia 24 hours after treatment that was not accompanied by changes in apoptosis. To address the cellular target of G-CSF, mRNA for the G-CSF receptor, Csf3r, was found in adult mouse testes and cultured THY1+ (undifferentiated) spermatogonia, and cell-surface localized CSF3R was observed on 3% of cultured THY1+ spermatogonia. CONCLUSION(S): These results demonstrate that G-CSF protects spermatogenesis from gonadotoxic insult (busulfan) in rodents, and this may occur via direct action on CSF3R+ undifferentiated spermatogonia. G-CSF treatment might be an effective adjuvant therapy to preserve male fertility in cancer patients receiving sterilizing treatments.