# Oocyte and embryo developmental competence following small multiple cyclophosphamide dose administrations in prepubertal female mice are comparable to adolescents

## TL;DR

A small multiple-dose regimen of cyclophosphamide in young mice reduces follicle loss and preserves oocyte and embryo quality over time.

## Contribution

The study shows that oocyte and embryo quality in prepubertal mice treated with small cyclophosphamide doses is comparable to adolescents.

## Key findings

- Prepubertal mice had a three-fold reduction in follicle count compared to untreated controls.
- Oocyte yield was significantly lower in prepubertal mice compared to adolescents.
- Embryo quality, blastulation, and cell count were comparable between prepubertal and adolescent groups.

## Abstract

A small multiple-dose regimen of cyclophosphamide (CY) compared to a large single dose in prepubertal mice has shown reduced follicle loss and improved fertility outcomes at early reproductive age. However, the long-term effects on the competency of oocytes from such surviving follicles, compared to those at post-pubertal age, remain unknown. Small multiple CY (75 mg/Kg, four weekly doses) injections were administered to prepubertal (PP75X4) and adolescent (AD75X4) Swiss albino female mice. At 22 weeks of age, surviving females were assessed for follicular pool and oocyte functional competency. The resulting embryos were assessed for blastulation, total cell number (TCN) quality, and in vitro inner cell mass (ICM) progression. At 22 weeks of life, PP75X4 females had a three-fold reduction (p < 0.001) in the total number of follicles compared to the untreated control. However, the differences between PP75X4 and AD75X4 were not statistically significant. Though PP75X4 females demonstrated a significant (p < 0.001) reduction in oocyte yield when compared to AD75X4, embryo quality, blastulation, TCN, and apoptosis were comparable between PP75X4 and AD75X4 groups. Small multiple doses of CY lead to reduced oocyte yield in prepubertal mice compared to adolescents. This study suggests that oocytes from prepubertal and adolescent individuals receiving small multiple doses of CY exhibit comparable functional competence, resulting in embryos of similar quality.

The online version contains supplementary material available at 10.1038/s41598-025-33355-2.