J. Hakim1, O. Wyman2, S. Keswani1 1Texas Children’s Hospital,Pediatric Adolescent Gynecology,Houston, TX, USA 2Baylor College Of Medicine,Houston, TX, USA
Introduction: There is a need for new therapies to prevent vaginal fibrosis. Up to 50,000 girls and 213,000 adult women yearly in the United States require vaginal reconstructive surgery. There is a high rate (up to 73%) of vaginal fibrosis after these surgeries. Sequelae from vaginal fibrosis can be life-long and lead to significant reductions in quality of life. Currently, treatments are limited to conjugated estrogen (CEE) creams in combination with vaginal stents. Unfortunately, current CEE creams cannot assess delivered estrogen due to cream egress from the vagina and the cumbersome nature of vaginal stents leads to early discontinuation. We have created a novel hydrogel that utilizes “click” chemistry to make a thermogelling hyaluronic acid (HA) drug eluting hydrogel. We sought to compare local estrogen delivery with Premarin cream to sustained estrogen delivery with a novel CEE-eluding NorbHA hydrogel on vaginal wound healing.
Methods: Norbornene-functionalized hyaluronic acid (NorbHA) and tetrazine-functionalized hyaluronic acid (TetHA) was synthesized. Hydrogel was composed of a 1:1 ratio of NorbHA:TetHA with various concentrations of estradiol (E2), 1.5 MDa HA, or a combination of both. The vaginal stents were placed into a full-thickness 1 mm murine vaginal excisional injury model. Animals were sacrificed at days 0, 2, 3, 7, 10. Macrophage inhibiting factor 1 (MIF1), transforming growth factor-β3 (TGFβ3) expression and vascular endothelial growth factor (VEGF) expression were analysed as markers of inflammation and angiogenesis respectively. Histology and immunohistochemistry were used to assess wound resolution and estrogen receptor (ER) density.
Results: Dissolution parameters demonstrated that drug release was still possible until 72h in the thermogelling hydrogel compared to CEE cream (12h). There was a burst release of E2 over the first 12h period followed by a steady-state release while HA had a burst release at 24 h. A statistically significant decrease in MIF1 expression was found in the group containing both HA and E2 compared to the CEE cream between the day 0 and day 3 timepoints. Greater expression of TGFβ3 and VEGF were found in the groups containing E2, or E2/HA compared to the estrogen cream by day 2. ER density increases with E2 delivery but appears to be dependent on circulating estrogen levels.
Conclusion: Vaginal tissue healing is enhanced through a novel thermogelling vaginal hydrogel with sustained estrogen and HA release compared to local exogenous estrogen cream. Improvements in both the anti-inflammatory and pro-angiogenic effects of sustained estrogen delivery included reduction in neutrophil and macrophage infiltration, modulating ECM degradation and stabilizing collagen. Further development of this platform may provide a substantial increase in efficacy of E2 delivery to the vaginal tissue and reduce post-operative vaginal fibrosis.