Periarticular Mesenchymal Progenitors Initiate and Contribute to Secondary Ossification Center Formation During Mouse Long Bone Development. (6th February 2019)

• Record Type: Journal Article
• Authors: Tong, Wei; Tower, Robert J.; Chen, Chider; Wang, Luqiang; Zhong, Leilei; Wei, Yulong; Sun, Hao; Cao, Gaoyuan; Jia, Haoruo; Pacifici, Maurizio; Koyama, Eiki; Enomoto-Iwamoto, Motomi; Qin, Ling
• Is Part Of: Stem cells. Volume 37:Number 5(2019)
• Page Start: 677
• Page End: 689
• Publication Date: 2019-02-06
• Subjects: Mesenchymal progenitors -- Periarticular layer -- Cartilage -- Secondary ossification center -- Blood vessel; Cloning -- Periodicals; Clone cells -- Periodicals; Stem cells -- Periodicals; Cell Differentiation -- Periodicals; Cell Division -- Periodicals; Clone Cells -- Periodicals; Hematopoietic Stem Cells -- Periodicals; Stem Cells -- Periodicals; 571.84
• DOI: 10.1002/stem.2975
• Languages: English
• ISSNs: 1066-5099

Abstract

Abstract: Long bone development involves the embryonic formation of a primary ossification center (POC) in the incipient diaphysis followed by postnatal development of a secondary ossification center (SOC) at each epiphysis. Studies have elucidated major basic mechanisms of POC development, but relatively little is known about SOC development. To gain insights into SOC formation, we used Col2-Cre Rosa-tdTomato ( Col2/Tomato ) reporter mice and found that their periarticular region contained numerous Tomato-positive lineage cells expressing much higher Tomato fluorescence (termed Tomato H ) than underlying epiphyseal chondrocytes (termed Tomato L ). With time, the Tomato H cells became evident at the SOC invagination site and cartilage canal, increased in number in the expanding SOC, and were present as mesenchymal lineage cells in the subchondral bone. These data were verified in two mouse lineage tracing models, Col2-CreER Rosa-tdTomato and Gli1-CreER Rosa-tdTomato . In vitro tests showed that the periarticular Tomato H cells from Col2/Tomato mice contained mesenchymal progenitors with multidifferentiation abilities. During canal initiation, the cells expressed vascular endothelial growth factor (VEGF) and migrated into epiphyseal cartilage ahead of individual or clusters of endothelial cells, suggesting a unique role in promoting vasculogenesis. Later during SOC expansion, chondrocytes in epiphyseal cartilage expressed VEGF, and angiogenic blood vessels preceded Tomato H cells. Gene expression analyses of microdissected samples revealed upregulation of MMPs in periarticular cells at the invagination site and suggested potential roles for novel kinase and growth factor signaling pathways in regulating SOC canal initiation. In summary, our data indicate that the periarticular region surrounding epiphyseal cartilage contains mesenchymal progenitors that initiate SOC development and form subchondral bone. Stem Cells 2019;37:677–689 : Abstract : Schematic of secondary ossification center canal formation. Secondary ossification center development is initiated by invasion of periarticular, multipotent mesenchymal progenitors from discrete sites along the epiphyseal surface into the underlying cartilage. (i) At the time of secondary ossification center initiation, these periarticular cells, but not surrounding chondrocytes, express vascular endothelial growth factor, important for recruiting individual endothelial cells (vasculogenesis) and existing vessels (angiogenesis) from the surrounding vasculature. (ii) Invasion of the secondary ossification center canal is associated with extensive proliferation within the canal, degradation of chondrocyte matrix and chondrocyte apoptosis. Transition from canal invasion to expansion is associated with a redistribution of vascular endothelial growth factor expression, from cells within the canal and along the leading edge, to surrounding hypertrophic chondrocytes. (iii) This transition is associated with a transformation from periarticular cell-led invasion to blood vessel-led secondary ossification center expansion. Secondary ossification center expansion continues, eventually giving rise to the epiphyseal marrow cavity. (iv) Mesenchymal lineage cells (i.e., osteoblasts, osteocytes, perivascular cells, adipocytes, etc.) within the epiphyseal region are derived from periarticular progenitor cells present within the invading secondary ossification center canal.