The effects of type I collagenase on the degelification of chimpanzee ( Pan troglodytes ) semen plug and sperm quality

Semen from the chimpanzee species becomes a colloidal solid after ejaculation. The formation of this copulatory plug is believed to prevent additional spermatozoa of subsequent mating events from accessing the ova. However, this naturally preserved strategy hampers the processes for sperm preparation. In this study, we investigated whether collagenasecan be used to degelify the semen plug and accelerate the semen liquefactionprocess in zoo captive chimpanzee species (Pan troglodytes). We showed that incubation of chimpanzee ejaculateswith 0.1% type I collagenaseefficiently and significantly (p < 0.05) releases 2.7-fold more spermatozoa from the coagulated ejaculates, and this degelification process did not alter sperm morphology or viability; nor did it stimulate spontaneous capacitation or an acrosome reactionas assessed by tyrosine phosphorylation and peanut agglutininstains; moreover, based on computer assisted sperm analysis assay, motility-related parameters remained similar to those of untreated spermatozoa. When collagenaseeffects were evaluated on cryopreserved sperm samples, we observed post collagenasetreatment in which 2.5% glycerol, as a cryoprotectant, preserved sperm acrosomeintegrity better than 7.8%; however, 7.8% glycerol, as a cryoprotectant, maintained sperm motility better than that of 2.5% glycerol. Our results demonstrated for the first time that type I collagenasecan be used to obtain a significantly higher number of spermatozoa from colloid chimpanzee semen ejaculatewithout affecting the physiological properties of spermatozoa, and these results are critical for the subsequent gamete development. Our results would benefit sperm preparation processes and cryopreservation efficiency per ejaculate, as more unaffected spermatozoa can be released from the semen plug within a shorter period of time. These results would also benefit the genetic diversity of the chimpanzee species, using sperm cellsfrom less dominant individuals, and for achieving better pregnancy success in primates with significantly higher amounts of sperm for artificial insemination.