One of the crucial steps in endochondral bone formation is the replacement of a cartilage matrix produced by chondrocytes with bone trabeculae made by osteoblasts. However, the precise sources of osteoblasts responsible for trabecular bone formation have not been fully defined. To investigate whether cells derived from @entity1184 chondrocytes contribute to the osteoblast pool in trabecular bones, we genetically labeled either @entity1184 chondrocytes by @entity21272 -Cre or chondrocytes by @entity440 -induced @entity36448 -CreERT2 using EGFP, LacZ or @entity523 expression. Both Cre drivers were specifically active in chondrocytic cells and not in perichondrium, in periosteum or in any of the osteoblast lineage cells. These in vivo experiments allowed us to follow the fate of cells labeled in @entity21272 -Cre or @entity36448 -CreERT2 -expressing chondrocytes. After the labeling of chondrocytes, both during prenatal development and after birth, abundant labeled non-chondrocytic cells were present in the primary spongiosa. These cells were distributed throughout trabeculae surfaces and later were present in the endosteum, and embedded within the bone matrix. Co-expression studies using osteoblast markers indicated that a proportion of the non-chondrocytic cells derived from chondrocytes labeled by @entity21272 -Cre or by @entity36448 -CreERT2 were functional osteoblasts. Hence, our results show that both chondrocytes prior to initial ossification and growth plate chondrocytes before or after birth have the capacity to undergo transdifferentiation to become osteoblasts. The osteoblasts derived from @entity21272 -expressing @entity1184 chondrocytes represent about sixty percent of all mature osteoblasts in endochondral bones of one month old @entity19 . A similar process of chondrocyte to osteoblast transdifferentiation was involved during bone @entity174 healing in adult @entity19 . Thus, in addition to cells in the periosteum chondrocytes represent a major source of osteoblasts contributing to endochondral bone formation in vivo.

Chondrocytes Transdifferentiate into Osteoblasts in Endochondral Bone during Development, Postnatal Growth and XXXX Healing in @entity19 .

@entity440 :: ('MESH:D013629', 'Chemical') :: ['tamoxifen'] @entity174 :: ('MESH:D050723', 'Disease') :: ['fracture'] @entity1184 :: ('MESH:D006984', 'Disease') :: ['hypertrophic'] @entity19 :: ('10090', 'Species') :: ['mice'] @entity523 :: ('4081', 'Species') :: ['Tomato'] @entity36448 :: ('11595(Tax:10090)', 'Gene') :: ['Agc1'] @entity21272 :: ('12813(Tax:10090)', 'Gene') :: ['Col10a1']
@entity174 :: (MESH:D050723,Disease) :: ['Fracture']
