Intra-Seminiferous Tubular Injection of Vascular Endothelial Growth Factor C Sustained-Release Ultrafine Particles: A Novel Method for Improving the Regeneration of Spermatogenesis After Chemotherapy

Abstract

Busulfan and other chemotherapeutic drugs used in the treatment of cancer may result in temporary or even permanent damage to spermatogenesis. During spermatogenesis, the rapidly dividing spermatogonia are highly susceptible to chemotherapy. Consequently, there is significant interest in developing an approach that could provide stimulation and regenerate spermatogenesis after chemotherapy. In a previous study, we suggested the potential application for vascular endothelial growth factor C (VEGFC) because of its key role in stimulating the proliferation of spermatogonia. However, methods to facilitate the recovery of spermatogenesis in such patients using VEGFC, or other regulatory factors, are sorely lacking because of the rapid degradation of these proteins and restrictions created by the blood-testis-barrier. To this end, we loaded VEGFC into polyanion dextran sulfate incorporated in a polycation chitosan shell to produce VEGFC sustained-release ultrafine particles (UFPs, CS-DS-VEGFC). We tested such particles in an azoospermic mouse model, created using busulfan. For each mouse, CS-DS-VEGFC was injected into the seminiferous tubules of one testis, while unloaded UFPs (CS-DS), or the VEGFC protein alone, was injected into the opposite testis as a control. All mice were sacrificed and evaluated 5 weeks later. Spermatogenesis in the tubules that were injected with CS-DS-VEGFC was clearly better than those injected with controls, and contained more spermatogonia and spermatocytes, along with Ki67 and PCNA positive-cells per tubule. In addition, the phosphorylation levels of AKT and MAPK in these tubules were also higher than in controls, indicating that CS-DS-VEGFC could induce the sustained activation of these pathways. In conclusion, CS-DS-VEGFC, combined with the efferent tubule injection technique, is a feasible approach with which to improve the regeneration of spermatogenesis in busulfan-induced azoospermic mice.