Exogenous ephrin-A3 reverses loss of vaginal epithelial barrier protection in progestin-treated mice.

Desmosomes are junctional complexes that confer mechanical strength and enhance barrier protection at mucosal epithelial surfaces by anchoring intermediate filaments to plasma membrane. These roles are best defined in cutaneous epithelium, but we previously identified lower levels of the desmosomal cadherins desmoglein-1 (DSG1) and desmocollin-1 (DSC1) and loss of barrier function in vaginal epithelium of mice treated systemically with the progestin depot medroxyprogesterone acetate (DMPA). We also showed these changes were avoided in mice treated with both DMPA and a conjugated equine estrogen vaginal cream. We extend these earlier results in the current investigation, identifying ephrin-A3 (EFNA3) as an important regulator of desmosomal cadherin gene expression in murine vaginal epithelial tissue. Moreover, topical treatment of mice with recombinant EFNA3 (rEFNA3) significantly increased vaginal expression of DSG1 and partially reversed the loss of vaginal epithelial barrier function induced by DMPA treatment. Consistent with this improvement in vaginal epithelial barrier protection, mortality caused by genital herpes simplex virus type 2 infection was delayed, but not prevented, in mice administered DMPA and rEFNA3 vs. DMPA alone. Together, current studies identify EFNA3 as a key regulator of desmosomal structure and function in vaginal epithelium and newly suggest that ephrin-Eph signaling pathways will provide an important target for enhancing vaginal epithelial integrity and barrier function.