High-precision microbeam radiotherapy reveals testicular tissue-sparing effects for male fertility preservation

Hisanori Fukunaga,Kiichi Kaminaga,Akinari Yokoya,Ritsuko Watanabe,Takuya Sato,Noriko Usami,Takehiko Ogawa,Kevin M Prise,Karl T Butterworth

doi:10.1038/s41598-019-48772-3

Abstract

Microbeam radiotherapy (MRT) is based on a spatial fractionation of synchrotron X-ray microbeams at the microscale level. Although the tissue-sparing effect (TSE) in response to non-uniform radiation fields was recognized more than one century ago, the TSE of MRT in the testes and its clinical importance for preventing male fertility remain to be determined. In this study, using the combination of MRT techniques and a unique ex vivo testes organ culture, we show, for the first time, the MRT-mediated TSE for the preservation of spermatogenesis. Furthermore, our high-precision microbeam analysis revealed that the survival and potential migration steps of the non-irradiated germ stem cells in the irradiated testes tissue would be needed for the effective TSE for spermatogenesis. Our findings indicated the distribution of dose irradiated in the testes at the microscale level is of clinical importance for delivering high doses of radiation to the tumor, while still preserving male fertility.

Highlights

Infertility is still an unfortunate adverse effect of most cancer therapies, as it impacts the quality of life in cancer survivors
Since the establishment of the fundamental concept of “microbeam radiotherapy (MRT)” in the 1990s, which is based on a spatial fractionation of synchrotron-generated X-ray microbeams at the microscale level[15], notable tissue-sparing effects (TSE) following exposure to micro-slit X-ray microbeams have been confirmed in a variety of species and tissue types[16,17,18,19,20,21]
Our high-precision microbeam analysis demonstrated that the dynamics of the non-irradiated germ cell population via seminiferous tubules would be essential for the effective testes TSE following Microbeam radiotherapy (MRT) for preserving spermatogenesis

Summary

Introduction

Infertility is still an unfortunate adverse effect of most cancer therapies, as it impacts the quality of life in cancer survivors. We used a transgenic mouse model expressing acrosome-green fluorescent protein (Acr-GFP) which is a meiosis-specific biomarker[22,23] We coupled this with a novel ex vivo testes organ culture technique, developed in 2011 to produce fully functional sperm in vitro (Fig. 1, and Supplementary Fig. 1, 2)[24]. This allows clear and easy monitoring of the process of spermatogenesis for more than one month[25] As previously reported, this ex vivo model of spermatogenesis can reproduce the deterministic effects of radiation (e.g., temporary infertility and permanent sterility) following uniform exposure to conventional X-rays[26]. We confirmed that the radiation-induced biological effects on spermatogenesis (e.g., temporary infertility and permanent sterility) in ex vivo replicant samples following uniform exposure to the synchrotron X-ray beams are dose-dependent (see Supplementary Figs 3, 4)

Methods

Results

Conclusion