<p>(<b>A and B</b>) Formation of colony forming units-osteoblasts (CFU-OB) in ex-vivo cultures of bone marrow cells from 3-week-old <i>Lmna</i><sup>−/−</sup> mice (lower panels) and WT controls (upper panels). The number of colony forming units-osteoblast (CFU-OB) per femur was significantly higher after 3 wks of differentiation in WT mice compared to <i>Lmna</i><sup>−/−</sup> mice (<b>B</b>). (<b>C</b>) Sections of plastic embedded proximal tibiae (secondary spongiosa) from <i>Lmna</i><sup>−/−</sup> mice and WT controls (n = 10 per group) were stained sequentially with toluidine blue (upper panels, Magnification ×40) for osteoblasts (black arrows) and osteocytes (red arrows) and ALP (lower panels, Magnification ×20) for osteoblasts (arrows). (<b>D</b>) A significant decrease (−47%) in the number of ALP expressing osteoblasts (N.Ob) and a significant decrease in osteocyte number (N.Ot) (−50%) were seen in <i>Lmna</i><sup>−/−</sup> mice compared with WT<sup>+/+</sup> mice. Micrographs are representative of those from eight different mice of each genotype. *<i>P</i><0.001. Changes in osteoblast differentiation and function correlated with changes in a serum biochemical marker of bone formation (P1NP) in <i>Lmna</i><sup>−/−</sup> mice compared with WT<sup>+/+</sup> mice. *<i>P</i><0.001. (<b>E</b>) The reduction in osteoblast differentiation in <i>Lmna</i><sup>−/−</sup> mice was associated with lower expression of osteocalcin (OCN) and osteopontin (OPN) at the mRNA level. There were no differences in Runx2 expression between <i>Lmna</i><sup>−/−</sup> mice and their WT controls. For PCR, data analysis is expressed as the ratio of the gene of interest vs. GAPDH as control. Data represent the mean±SD of triplicate determinations. *<i>P</i><0.001.</p
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