Preventive effect of swim bladder hydrolysates on cyclophosphamide-induced ovarian injury in mice

Aims This study aimed to prepare swim bladder hydrolysate (SBH) with M-n < 4000 Da, and investigate its effects on cyclophosphamide (CTX)-mediated ovarian injury in mice. Methods Hydrolysates were prepared by heating extraction, enzymatic hydrolysis and ultrafiltration. M-n and distribution of SBH were analyzed via gel filtration chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Changes in the mouse oestrus cycle were determined by cytological examination. The number of follicles was examined using histopathology. Enzyme-linked immunosorbent assays (ELISAs) were used to determine the serum sex hormone levels. Results The M-n of SBH, prepared by heating extraction, enzymatic hydrolysis, ultrafiltration, and from different batches, was below 4000 Da, and the preparation process was stable. Compared with the control group, the low-, middle-, and high-dose SBH treatment groups showed different trends in oestrus duration, serum sex hormone levels, and the number of primordial and secondary follicles. The oestrus cycle duration of the high-dose SBH group was longer than that of the model group. The serum luteinizing hormone, follicle-stimulating hormone, and anti-Mullerian hormone levels in the middle-dose group were the closest to those of control group. The number of primordial and secondary follicles in the medium-dose group was significantly higher than that in the model group and closest to those of control group. Conclusion After heating extraction, trypsin/Flavourzyme hydrolysis and ultrafiltration, a hydrolysate with M-n below 4000 Da could be prepared. We found that a moderate (400 mg/kg) SBH dose resulted in the greatest effect on ovarian injury remission in mice.