Fig. 1: RSPO3 is expressed in osteoblasts but not in osteocytes or osteoclasts.
From: RSPO3 is important for trabecular bone and fracture risk in mice and humans
a Rspo3 mRNA expression pattern in various tissues of male, wildtype mice (n = 6). Mean of individual values are presented as horizontal lines and ±SEM as vertical lines. Data are presented as % of expression in cortical diaphyseal bone. b Rspo3 is expressed in primary calvarial osteoblasts (OBL), but not in bone marrow-derived macrophages (BMM) or RANKL-differentiated osteoclasts (OCL). Rspo3 gene expression increase from day 2 (d2) to day 7 (d7) in primary calvarial osteoblasts cultured in osteogenic media. Presented as % of expression in osteoblasts day 2. ND=not detectable. Mean of individual values are presented as horizontal lines and ±SEM as vertical lines. Difference in expression between day 2 and 7 was analyzed by two-sided Student’s t test, n = 4 wells per group. c–f Representative in situ hybridization images in mice. Transverse sections across lumbar vertebra 5 in mouse showing the mRNA expression pattern (red) of Rspo3 (c–f, upper) and Runx2 (c, lower), Col1a1 (d, lower), Dmp1 (e, lower), and Acp5/Trap (f, lower). The lower images are consecutive to the upper images. Rspo3 mRNA could be observed in Runx2-expressing (c), Col1a1-expressing (d), and Dmp1-expressing (e) osteoblast lineage cells (OBL) on the bone surface. In contrast, Rspo3 was not detectable in osteocytes (Ocy; e), or osteoclasts (OCL; f). Scale bar 50 µm. g–i Representative in situ hybridization images in humans. Sections from human proximal femur (g) and iliac crest (h, i) confirmed moderate RSPO3 mRNA expression. Staining for RSPO3 mRNA (red) were observed in immature osteoblast lineage cells (OBL) on eroded lining surfaces (reversal cells), and on quiescent bone surfaces (bone lining cells), as well as in a subset of cells close to blood vessels (bv; g, h). No RSPO3 mRNA expression was observed in osteocytes (Ocy) or TRAP-immunostained osteoclasts (OCL, black; i). Scale bar 20 µm. Experiments were repeated one (a), two (g–i) or at least three (b–f) times. Source data are provided as a Source Data file.
