Fig. 1. Burst in DMP1 secretion from osteoblasts into ECM at the OF-GP border during periadolescence.

a Volcano plot of significantly differentially expressed genes in juvenile (4 weeks, n = 5) versus adult (12 weeks, n = 4) capillary with surrounding cells from the ossification front (OF) (mean expression value >500, red: Log₂ FC > 0.66, P < 10⁻⁵). b, Log₂ transformed number of reads mapped to the Dmp1 gene. c DMP1 immunostaining in the OF throughout postnatal bone development. Red arrows point at DMP1 at the OF base. Scale bar 250 µm. d DMP1 and endomucin (EMCN) immunostaining of the OF from 5-week-old femur. Red arrows point at type H vessels. Scale bar 50 µm. e Schematic depiction of the femur with a green plane going through the centre of the bone, where DMP1 secretion is observed. Example of DMP1 immunostaining of a section taken from the middle part of the femur, showing the definition of the central and peripheral regions used for further automated quantification. Scale bar 250 µm. f Quantification of DMP1 staining intensity in the centre and periphery of the OF throughout bone development. Mean ± SD. g Quantification of the contribution of the central and peripheral part to the total DMP1 amount. Mean ± SD. f, g at 4 weeks n = 7, 5 weeks n = 5, 5.5–6 weeks n = 10, 8 weeks n = 5, 12–15 weeks n = 6. Pooled data from five independent experiments. P values show the significance between the intensity in the centre versus periphery for every mouse (paired analysis). Two-tailed Wilcoxon matched-pairs signed-rank test. h Dmp1 mRNA (RNAScope) of the central regions of OF and GP from 5- and 5.5-week-old femurs. Lack of Dmp1 expression in chondrocytes of the GP; yellow frame indicates the region shown in i. Scale bar 50 µm. i RNAScope images of Dmp1, Osterix (Osx), and Runx2 (only depicted in Supplementary Fig. 2c). Scale bar 50 µm. j Number of Dmp1-expressing cells in the central and peripheral region of the OF based on RNAScope images. n = 3 per age. Pooled data from two independent experiments. Mean ± SD. k DMP1 and EMCN immunostaining of 5.5-week-old femur. Infiltration of DMP1 from the OF into the GP. Scale bar 50 µm. b, f, g, j Source data are provided in Source Data file.