Human Otic progenitor cell models of congenital hearing loss applied to to Zika virus and cytomegalovirus infections
Congenital hearing loss is a common chronic condition affecting children in both developed and developing nations. In many cases, congenital hearing loss is ultimately attributed to viral infection, most often by cytomegalovirus (CMV), but also in Congenital Zika Syndrome (CZS). The mechanisms by which CMV and ZIKV virus cause these cranial developmental defects have not been elucidated. Inner ear development has been particularly difficult to study, given the inaccessibility and scarcity of the tissue in animal models or on human autopsy; however, it is now possible to culture stem-cell derived otic progenitor cells (OPCs). Here we describe successful in-vitro infection of OPCs with either CMV or ZIKV. We find that ZIKV infection rapidly and strongly induces the expression of type I IFN and inflammatory genes, while simultaneously decreasing otic cell viability in culture that is at least in part attributable to apoptosis. In contrast, CMV infection did not appear to elicit either of these effects and instead demonstrated a clear dysregulation of the expression of many key genes and pathways associated with inner ear development and function, including Cochlin, NGFR, SOX11 and TGF-ß signaling. These findings suggest that ZIKV and CMV infections cause congenital hearing loss through very different pathways; that is, by killing progenitor cells in the case of ZIKV infection, and via disruption of critical developmental pathways in the case of CMV infection. In addition to demonstrating differential hCMV and ZIKV pathogenesis mechanisms in OPCs, this study highlights the advantages of otic progenitor cell models for the study of congenital hearing loss induced by viral infection. Overall design: Zika and CMV infection of human stem-cell derived otic progenitor cells compared with Mock and heat-inactivated viral infection samples at different time points.