par Nguyen, Thuy 
Président du jury Maenhaut, Carine
Promoteur Demeestere, Isabelle
Publication Non publié, 2025-05-05
Président du jury Maenhaut, Carine
Promoteur Demeestere, Isabelle
Publication Non publié, 2025-05-05
Thèse de doctorat
| Résumé : | Advances in cancer treatments have significantly improved survival rates, but they often come with long-term adverse effects that can impact quality of life. One of the effects is gonadotoxicity, leading to fertility impairment after chemotherapy and radiotherapy. Fertility preservation has become a critical priority for young cancer survivors. Current methods include mainly oocyte and embryo cryopreservation and ovarian tissue cryopreservation. However, these techniques often require invasive procedures and may not be suitable for all patients, particularly for prepubescent girls or those with aggressive cancers requiring immediate treatment. As an alternative, pharmacological protection is gaining attention, including microRNA-based therapies which emerge as a particularly promising approach to prevent chemotherapy-induced ovarian damage. microRNAs are small, non-coding RNAs that regulate gene expression and play essential roles in both physiological and pathological processes. microRNA therapy aims to modify miRNA expression profiles in affected tissues, offering the potential advantage of targeted and minimally invasive treatments.Previous research in our lab identified let-7a as a promising candidate for protecting ovaries from chemotherapy-induced toxicity. Replacement miRNA therapy with let-7a using liposome transfection method demonstrated encouraging preliminary results, by preventing cyclophosphamide-induced apoptosis in vitro and supporting follicular development in vivo using a mouse ovarian transplantation model.This project focuses on clinically applicable delivery systems for miRNA mimics, specifically gold nanoparticles (AuNPs). They are biocompatible, tunable, and can be functionalized to address limitations such as stability, immunogenicity, and tissue specificity, making them a versatile tool for miRNA transport. To synthetize and design microRNA-AuNPs systems, we are collaborating with the Engineering Molecular NanoSystems lab (ULB) to develop calixarene-coated AuNPs, an innovative approach to securely anchor miRNAs onto the nanoparticles.Since molecular modifications can alter AuNP behavior, the first part of the project assessed the safety, internalization, and subcellular localization of calixarene-coated AuNPs carrying nucleic acids. We compared these to AuNPs modified using classical thiol chemistry in MCF-7 and GC-1 spg cell lines. Both systems demonstrated high biocompatibility and effective cellular uptake in vitro. Interestingly, differences in subcellular localization between the two AuNPs systems in MCF-7 and GC-1 spg cells suggest that their intracellular trafficking are cell-type dependent.In the second part of the project, we aim to first confirm the results from the initial study on neonatal mouse ovaries cultured in vitro using AuNPs-Let-7a. Both AuNPs systems demonstrated safety, and calixarene-coated AuNPs effectively entered ovarian tissues. Next, we evaluated the efficiency of calixarene-coated AuNPs in delivering let-7a and protecting ovaries from chemotherapy-induced damage. However, no protective effect was observed under the tested conditions in neonatal ovaries exposed to chemotherapy. Efforts to improve the system by optimizing the let-7a sequence did not enhance let-7a expression in ovaries treated with calixarene-coated AuNPs-Let-7a. Stability assessments of the system during the pre-transfection process revealed significant instability.These findings highlight the need for further development of calixarene-coated AuNPs-Let-7a, including improving system stability and investigating the underlying reasons for the failure to deliver let-7a effectively to ovarian tissues. Addressing these limitations is critical to achieve therapeutic efficacy. |
