Fertility restoration using immature testicular tissue cryopreserved before gonadotoxic treatment : optimization of the transplantation technique
(2022)
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- Authors
- Supervisors
- Wyns, Christine
- Abstract
- Chemotherapy and radiotherapy can induce permanent infertility of the treated patient. For prepubertal boys, no option is currently available for the restauration of fertility after anti-cancer treatments. This represents a major concern that moved several centers all over Europe and North America to develop fertility preservation programs that though experimental, are met with high rates of acceptance by the patients and their parents. As no mature gametes can be found in the testicle before puberty, the only available option is the preservation of spermatogonia, diploid germ cells that are precursors of spermatozoa. Retrieval of immature testicular tissue (ITT) through a small biopsy is a safe and efficient method to preserve germ cells before exposure to gonadotoxic treatments. Amongst the several alternatives currently under-study for fertility restoration, transplantation of frozen-thawed ITT fragments is the most promising option. This procedure has not been performed yet on human subjects, although the xeno-transplantation of such fragments to the nude mice provided a valuable model to study. However, every report on human ITT xeno-transplants described an arrest of spermatogenesis at the pachytene spermatocytes stage and an important germ cells loss. After multiple reports of failed attempts at improving the transplantation procedure through in vivo administration of antioxidants or hormonal supplementation and in vitro culture with supporting molecules before grafting, application of tissue engineering led to promising results in autografts of mice testicular tissue. Indeed, administration of nanoparticles delivering Vascular endothelial growth factor (VEGF) and encapsulation in an alginate matrix improved respectively short-term vascularization and spermatogonial survival. The purpose of our project was to obtain a further improvement of testicular tissue transplantation technique applying tissue engineering. In the first part of the experience, we compared non-encapsulated mouse testicular tissue fragments to encapsulation in alginate or alginate supplemented with nanoparticles delivering necrosis inhibitors. In a second part of the experience, nanoparticles delivering necrosis inhibitors and nanoparticles delivering vascular growth factors (VEGF and Platelet derived growth factor- PDGF) were used to supplement the alginate matrices. In both parts of our experience, grafts were recovered after 5 and after 21 days in order to evaluate respectively the effect of hypoxia and of tissue revascularization. Results of the first part of our study confirmed the role of an alginate matrix in improving spermatogonial survival compared to non-encapsulated tissue. Additionally, alginate encapsulation was associated with a reduced peroxidation of lipid membranes. Use of necrosis-inhibitors-loaded nanoparticles was associated with increased survival of germ cells and improved tissue integrity after 21 days of grafting compared to both non-encapsulated tissue and tissue encapsulated in alginate only. In the second part of our study, we confirmed the role of nanoparticles delivering necrosis inhibitors and of the alginate matrix, and we also demonstrated how VEGF and PDGF nanoparticles can increase vascular surfaces as well as accelerate and improve vascular maturation. No further beneficial effect of vascular growth factors was found on tissue integrity and survival of germ cells, but the duration of the experiments should be extended to better evaluate potential benefits on germ cells development. In conclusion, our initial goals of improving germ cells survival and tissue integrity were met with alginate supplemented with nanoparticles containing necrosis inhibitors. The benefits on germ cells development of a faster and improved vascular network in grafts following vascular growth factors supplementation still need to be further evaluated.
- Affiliations
Citations
Del Vento, F. (2022). Fertility restoration using immature testicular tissue cryopreserved before gonadotoxic treatment : optimization of the transplantation technique. https://hdl.handle.net/2078.5/108885