Modeling methods for busulfan-induced oligospermia and asthenozoospermia in mice: a systematic review and meta-analysis

Abstract

Objective: Modeling methods for busulfan-induced oligoasthenozoospermia are controversial. We aimed to systematically review the modeling method of busulfan-induced oligospermia and asthenozoospermia, and analyze changes in various evaluation indicators at different busulfan doses over time.

Methods: We searched the Cochrane Library, PubMed databases, Web of Science, the Chinese National Knowledge Infrastructure, and the Chinese Biomedical Literature Service System until April 9, 2022. Animal experiments of busulfan-induced spermatogenesis dysfunction were included and screened. The model mortality and parameters of the evaluation indicators were subjected to meta-analysis.

Results: Twenty-nine animal studies were included (control/model: 669/1829). The mortality of mice increased with busulfan dose. Significant spermatogenesis impairment occurred within 5 weeks, regardless of busulfan dose (10-40 mg/kg). Testicular weight (weighted mean difference [WMD]: - 0.04, 95% CI: - 0.05, - 0.03), testicular index (WMD: - 2.10, 95% CI: - 2.43, - 1.76), and Johnsen score (WMD: - 4.67, 95% CI: - 5.99, - 3.35) were significantly decreased. The pooled sperm counts of the model group were reduced by 32.8 × 10⁶/ml (WMD: - 32.8, 95% CI: - 44.34, - 21.28), and sperm motility decreased by 37% (WMD: - 0.37, 95% CI: - 0.47, - 0.27). Sperm counts decreased slightly (WMD: - 3.03, 95% CI: - 3.42, - 2.64) in an intratesticular injection of low-dose busulfan (4 - 6 mg/kg), and the model almost returned to normal after one seminiferous cycle.

Conclusion: The model using low-dose busulfan (10 - 20 mg/kg) returned to normal after 10 - 15 weeks. However, in some spermatogenesis cycles, testicular weight reduction and testicular spermatogenic function damage were not proportional to busulfan dose. Sperm counts and motility results in different studies had significant heterogeneity. Standard protocols for sperm assessment in animal models were needed to reduce heterogeneity between studies.

Keywords: Asthenospermia; Busulfan; Mouse; Oligoasthenospermia; Oligospermia; Spermatogenic dysfunction; System evaluation.

Fig. 1

PRISMA flow diagram detailing process of study selection for the meta-analysis. Key: CNKI, China National Knowledge Infrastructure. Sino Med, Chinese Biomedical Literature Service System

Fig. 2

Forest plot and meta-analysis of mouse mortality

Fig. 3

Forest plot and meta-analysis of testicular weight

Fig. 4

Subgroup analysis of testicular weight

Fig. 5

Subgroup analysis of testicular index

Fig. 6

Subgroup analysis of Johnsen score

Fig. 7

Epididymal sperm count forest plot (A) and subgroup of sperm count (B)

Fig. 8

Epididymal sperm motility forest plot