Fig. 4. Deletion of sensory nerve abolishes divalent cation-induced bone formation.

a, b Representative immunofluorescent images and corresponding quantification showing the sprouting and arborization of calcitonin gene-related polypeptide-α⁺ (CGRP⁺) sensory nerves within the periosteum at week 1 postoperatively. Lower images (scale bars = 20 µm) are high-resolution versions of the boxed regions in the upper images (scale bars = 100 µm). c Co-immunostaining of CGRP with CD68 in the periosteum at week 1 postoperatively. Lower images (scale bars = 20 µm) are high-resolution versions of the boxed regions in the upper images (scale bars = 100 µm). DRG of L4 lumbar, which is responsible for the sensation of left femur, was harvested at week 1 postoperatively for histology study (d), representative immunofluorescent images (e), and corresponding quantification (f) showing the expression of CGRP (scale bars = 100 µm). g Representative immunofluorescent images showing the presence of CGRP⁺ sensory nerves in the femurs of TrkA^wt or TrkA_Avil^−/− mice. Lower images (scale bars = 50 µm) are high-resolution versions of the boxed regions in the upper images (scale bars = 100 µm). Reconstructed µCT images (h, scale bars = 1 mm) showing the cross-section of femurs from TrkA^wt mice or TrkA_Avil^−/− mice grafted with pure alginate or Mg²⁺-releasing alginate and corresponding measurements (i) of BV/TV, BMD of TV, and Ct.Ar. Data are mean ± s.d., *P < 0.05, **P < 0.01 by one-way ANOVA with Tukey’s post hoc test. Source data are provided as a source data file.