Connective Tissue Growth Factor reporter XXXX label a subpopulation of mesenchymal progenitor cells that reside in the trabecular bone region.

@entity19 @entity32251 @entity1612
Few gene markers selectively identify mesenchymal progenitor cells inside the bone marrow. We have investigated a cell population located in the @entity19 bone marrow labeled by Connective Tissue Growth Factor reporter expression ( @entity1612 -EGFP). Bone marrow flushed from @entity1612 reporter @entity19 yielded an EGFP+ stromal cell population. Interestingly, the percentage of stromal cells retaining @entity1612 reporter expression decreased with age in vivo and was half the frequency in females compared to males. In culture, @entity1612 reporter expression and endogenous @entity1612 expression marked the same cell types as those labeled using Twist2-Cre and @entity32251 -Cre fate mapping approaches, which previously had been shown to identify mesenchymal progenitors in vitro. Consistent with this past work, sorted @entity1612 + cells displayed an ability to differentiate into osteoblasts, chondrocytes, and adipocytes in vitro and into osteoblast, adipocyte, and stromal cell lineages after transplantation into a parietal bone defect. In vivo examination of @entity1612 reporter expression in bone tissue sections revealed that it marked cells highly localized to the trabecular bone region and was not expressed in the perichondrium or periosteum. Mesenchymal cells retaining high @entity1612 reporter expression were adjacent to, but distinct from mature osteoblasts lining bone surfaces and endothelial cells forming the vascular sinuses. Comparison of @entity1612 and @entity32251 reporter expression in bone tissue sections indicated an inverse correlation between the strength of @entity1612 expression and osteoblast maturation. Down-regulation of @entity1612 reporter expression also occurred during in vitro osteogenic differentiation. Collectively, our studies indicate that @entity1612 reporter @entity19 selectively identify a subpopulation of bone marrow mesenchymal progenitor cells that reside in the trabecular bone region.
