Persian onager (Equus hemionus onager) endometrial explant cryopreservation and in vitro culture

Assisted reproduction of endangered equids, such as Persian onagers (Equus hemionus onager), is vital for species conservation. Little is known about Persian onager reproductive functions, including functions of the uterine endometrium. Recently, successful cryopreservation of the domestic mare endometrium was reported, but there is no information on cryo-sensitivity or in vitro culture of endometrial tissues of any non-domestic equid. In the present study, endometrial explants from Persian onagers were cryopreserved and cultured in vitro for 5 days. There was no difference between endometrial explants when 10% and 20% dimethyl sulfoxide (DMSO) was used for cryopreservation. Cell viability and structural integrity were comparable to fresh tissue. Abundance of estrogen receptor-a (ESR1) and progesterone receptor (PGR) mRNA transcript in endometrial explants was less in most treatment groups compared to the fresh tissue control. There was variation in E-cadherin mRNA abundance in endometrial explants among treatment groups with some treatment groups having a lesser abundance compared to the control group. The abundance of Ki67 mRNA transcript of endometrial explants was not different among treatment groups compared to the control group. Results indicate that DMSO is a suitable cryoprotectant for the Persian onager endometrium, and in vitro culture in a liquid-gas interface can maintain Persian onager endometrial explants for as long as 5 days. Findings allow for a greater understanding of reproductive mechanisms in vitro for this endangered species and other domestic equids including donkeys.