BMP4 overexpression preserves vaginal innervation at high estrogen. A, Immunostaining for PGP9.5 at the site of injection 7 d after injection of lentivirus driving expression of only EGFP (EGFP Inj) showed low innervation density typical of OVX rats receiving estrogen supplementation. B, PGP-positive innervation density at sites injected with lentivirus driving BMP4 expression (BMP4 Inj) was considerably higher, characteristic of low-estrogen OVX rats. Scale bar, 50 μm. C, Injection of EGFP lentivirus did not alter innervation density relative to uninjected adjacent tissues (EGFP Adj), or to innervation at sites adjacent to injection with the BMP4 lentivirus (BMP4 Adj). Innervation density at sites receiving BMP4 lentivirus was significantly greater than that of other sites (*p = 0.019 for BMP4 Inj vs EGFP Inj and **p = 0.026 for BMP4 Inj vs BMP4 Adj). D, Staining for peripherin confirmed that changes noted with PGP9.5 also occur within this axonal population (#p ≤ 0.001 for BMP4 Inj vs EGFP Inj, and ##p ≤ 0.001 for BMP4 Inj vs BMP4 Adj).