Fig. 4: Localized delivery of 17-beta estradiol rescues SSC expansion in skeletal regeneration.

A Schematic of unilateral localized delivery of 17-beta estradiol PLGA nanoparticle scaffold (OVX + LE2) and contralateral PBS PLGA nanoparticle scaffold (OVX + PBS). Representative images demonstrate a smaller callus in the OXR + PBS (top) compared to OVX + LE2 (bottom) fracture callus at post fracture day 7. Black arrows point to areas of endochondral ossification. B Serum estradiol levels of sham vs OVX vs OVX + LE2 mice demonstrate no increase in serum estradiol levels in the localized rescue group (n = 6). C Assessment of bone mineral density (BMD) of trabecular bone in healing femora from sham (grey) vs OVX (red) vs OVX + LE2 (blue) mice (n = 10). D Maximal load to fracture (in newtons) of healing femora from sham vs OVX vs OVX vs OVX + LE2 mice (n = 10)]. E, F Relative rescue of absolute cell numbers of mSSCs (E) and BCSPs (F) in sham (grey) vs OVX with sham local rescue (red) vs OVX with localized E2 mice (blue) (n = 5) (mSSCs and BCSPs). No relative rescue in male mice with localized E2 (yellow) compared to male with sham local rescue (green). G, H Colony-forming assay of mSSCs (G) and BCSPs (H) isolated at post-fracture day 7 from Sham, OVX, and OVX + LE2 mice. mSSCs and mBCSP were plated in biological and technical triplicates. I Schematic showing the effect of stimulation ESR2 on postmenopausal osteoporosis and the related protein interaction pathways. J Schematic showing the cellular and molecular mechanisms underlying impaired ovariectomized skeletal regeneration. Sham environment (left), OVX environment (center), and impaired fracture repair in OVX environment can be rescued by supplying localized E2 sensing (right). The data in B,C,D,E,F,G,H are expressed as the means ± s.e.m; ordinary two-way ANOVA followed by Tukey’s multiple comparisons test; exact P value are indicated in the figures. For data and statistics, see Source Data File.