To increase chances for women with impaired gonadal function to conceive biological offspring in vitro platforms for cultivating small follicles are developed. These rely mainly on the manual supplementation of required hormones and growth factors. We hypothesize that within a 3D ovary model, direct interactions between stroma cells and follicles would improve follicle viability and growth, thereby resulting in a larger pool of mature follicles. In this study, a transglutaminase crosslinked poly(ethylene glycol) (TG‐PEG) is adapted in its stiffness and functionalized with the cell adhesion peptide RGD to allow growth of follicles and to render it bioactive. During seven days of culture, the follicles grow, retain important morphological characteristics, and oocytes acquire meiotic competence. Following this, a co‐culture system that utilizes either paracrine signaling between follicles and supporting cells or a co‐culture that relies on direct contact is employed, confirming improved follicle growth when cultured with support cells. Confocal imaging reveals formed cell–cell interactions between support cells and follicles in detail. This newly developed ovary model consisting of a highly tunable TG‐PEG hydrogel, follicles, and support cells facilitates functional follicle growth in vitro and allows to study follicle‐stroma cell interactions to help improve fertility preservation techniques.

Background/Objectives: Proton therapy is widely used in paediatric neuro-oncology because of its favourable dose distribution and reduced exposure to radiation of healthy tissue. Nevertheless, current knowledge regarding radiation-induced contrast enhancements (RICE) is largely derived from adult proton therapy cohorts, while evidence in paediatric patients remains limited and the underlying biological mechanisms are still incompletely understood. This study investigated the incidence of RICE in paediatric patients with low-grade glioma (LGG) and ependymoma and evaluated potential associations with linear energy transfer (LET) and variable relative biological effectiveness (RBE)-weighted dose distributions. Methods: In this retrospective single-centre study, paediatric patients with LGG or ependymoma were identified from a prospectively maintained institutional registry patients treated with proton therapy at the Heidelberg Ion-Beam Therapy Centre (HIT) between 2010 and 2024. Follow-up magnetic resonance imaging examinations were systematically reviewed for RICE. Lesions were contoured in RayStation and assessed dosimetrically using a fixed RBE of 1.1 and three variable RBE models. LET-weighted dose metrics and Dose_(RBE) × LET products were compared between RICE regions and planning target volumes (PTVs). Overall survival and progression-free survival were estimated using Kaplan–Meier method. Results: Seventy-six patients met the inclusion criteria, including 33 patients with LGG and 43 with ependymoma. A total of 724 follow-up magnetic resonance imaging examinations were reviewed. RICE occurred in six patients (7.9%), exclusively in the ependymoma subgroup (14.0%). Higher prescribed radiation dose was significantly associated with RICE occurrence (p = 0.031). Across all variable RBE models, biologically weighted dose estimates and Dose_(RBE) × LET products were consistently elevated within RICE regions compared with corresponding PTV regions, particularly at low- and intermediate-dose levels. Five-year overall survival rates were 91.7% for LGG and 86.6% for ependymoma, while corresponding progression-free survival rates were 84.4% and 69.3%, respectively. Conclusions: Variable RBE models identified biologically relevant dose heterogeneities within RICE regions that were not adequately captured by the conventional fixed RBE approach. These findings suggest that LET-associated biological dose escalation may contribute to radiation-related brain tissue changes after proton therapy and support further investigation and prospective validation of LET- and RBE-informed normal-tissue risk assessment in paediatric neuro-oncology.