# Comparing transplantation sites of mouse immature testicular tissue fragments embedded in chitosan scaffold to maintain tissue integrity: Epididymal fat pad or under the back skin

## TL;DR

This study compares two mouse tissue implant sites for preserving immature testicular tissue, finding that the back skin provides better results when using a chitosan scaffold.

## Contribution

The study introduces a novel comparison of two transplantation sites using a chitosan scaffold for mouse immature testicular tissue.

## Key findings

- The subcutaneous back skin site showed better tissue integrity and germ cell survival than the epididymal fat pad.
- The chitosan scaffold improved spermatogonial survival in both transplantation sites.
- The Back + S group had significantly more PLZF-positive cells per seminiferous tubule section.

## Abstract

Cryopreservation of immature testicular tissue (ITT) is currently the only technique available for restoring fertility in adolescent boys with cancer. Preclinical investigations assessing the development of human transplanted ITT using a nude mouse model have revealed a notable decrease in spermatogonial stem cells.

We transplanted ITT from neonatal male NMRI mice (3–5 days old), either embedded in a chitosan (CS) scaffold or without it, into the epididymal fat pad (Epi.fat) and back skin of mature (6–8 weeks old) male NMRI mice. Grafts were recovered 14 days post-transplantation. We evaluated scaffold cytotoxicity, morphology, in vivo degradation, tissue integrity, seminiferous tubule morphometry, and germ cell survival.

The diameters of the seminiferous tubules did not differ significantly between grafted groups. However, the height of the seminiferous epithelium in the Epi.fat + S group was significantly greater than in the Back + S group. The total seminiferous tubule area ratio in the Epi.fat, Epi.fat + S, and Back groups were significantly lower compared to the Back + S group. The number of PLZF-positive cells per seminiferous tubule section was significantly higher in the Back + S group than in the Epi.fat group.

Allotransplantation of ITT embedded in a CS scaffold enhanced spermatogonial survival and tissue integrity in both the Epi.fat and subcutaneous back skin. Among the two transplantation sites, the subcutaneous back skin yielded more favorable outcomes.