# Allogenic Follicular Fosterage Technology: Problems, Progress and Potential

## TL;DR

This paper reviews a technique that transfers immature egg cells from young animals into adult ones to improve egg development and embryo production.

## Contribution

The paper provides a comprehensive review of allogeneic follicular fosterage (AFF) technology, highlighting its progress and challenges for clinical use.

## Key findings

- Allogeneic follicular fosterage allows immature egg cells to develop in a natural in vivo environment.
- Improving synchronization between donor egg maturity and recipient follicles may enhance AFF success rates.
- Standardized procedures and reduced follicular aspiration damage are key for advancing AFF technology.

## Abstract

Prepubertal female animals possess an extensive ovarian pool but are unable to ovulate naturally as adult females do. Through the process of transferring oocytes from prepubertal females into the dominant follicles of adult females, a significant number of oocytes can be obtained while minimizing the adverse effects of the in vitro environment. This innovative technology offers an alternative approach to embryo production, independent of complex laboratory equipment. However, the reproducibility and efficiency of this technology are still insufficient for widespread clinical applications. This review shares the latest progress of this technology, outlines the current limitations, and summarizes the factors that affect the success rate of this technology.

The allogeneic follicular fosterage (AFF) technique transfers cumulus–oocyte complexes (COCs) from pubertal female animals to the dominant follicles of adult female animals for further development, allowing the COCs to further develop in a completely in vivo environment. This article reviews the history of AFF and JIVET and their effects on oocyte and embryo development as well as freezing resistance. Improving the efficiency and reproducibility of AFF technology is crucial to its clinical application. This article discusses factors that affect the success rate of AFF, including differences in specific technical procedures and differences between pubertal and adult follicles. Designing standardized procedures and details to improve the synchronization of donor COCs and recipient follicle maturity and reducing the damage to COCs caused by follicular aspiration may be the direction for improving the success rate of AFF in the future.