title: Impaired vascular invasion of Cbfa1-deficient cartilage engrafted in the spleen.
abstract: Chondrocyte maturation and vascular invasion of cartilage are essential in the process of endochondral ossification. Cbfal-deficient (Cbfa1-/-) mice displayed a complete absence of osteoblast and osteoclast maturation as well as severely inhibited chondrocyte maturation in most parts of the skeleton. Although chondrocyte maturation and mineralization were observed in restricted areas of Cbfa1-/- mouse skeleton, vascular invasion of calcified cartilage was never noted. To investigate the possibility of chondrocyte maturation and vascular invasion in Cbfal-/- cartilage and the role of the hematopoietic system in the process of vascular invasion, we transplanted embryonic day 18.5 (E18.5) Cbfa1-/- femurs, which are composed of immature chondrocytes, into spleens of normal mice. One week later, the transplanted femurs contained terminally differentiated chondrocytes expressing osteopontin, bone sialoprotein (BSP), and matrix metalloproteinase (MMP) 13. In the diaphyses of the transplants, the cartilage matrix was mineralized and the cartilage was invaded by vascular vessels and osteoclasts. However, chondrocyte maturation and vascular invasion were severely retarded in comparison with transplants of E14.5 wild-type femurs, in which the cartilage was rapidly replaced by bone, and neither mature osteoblasts nor bone formation were observed. In primary culture of Cbfa1-/- chondrocytes, transforming growth factor (TGF) beta1, platelet-derived growth factor (PDGF), interleukin (IL)-1beta, and thyroid hormone (T3) induced osteopontin and MMP-13 expression. These findings indicated that factors in the hematopoietic system are able to support vascular invasion of cartilage independent of Cbfal but are less effective without it, suggesting that Cbfal functions in cooperation with factors from bone marrow in the process of growth plate vascularization.
authors.affiliation: Department of Molecular Medicine, Osaka University Graduate School of Medicine, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Himeno
authors.forename: Hirayuki
authors.initials: H
authors.lastname: Enomoto
authors.forename: Wenguang
authors.initials: W
authors.lastname: Liu
authors.forename: Kiyoto
authors.initials: K
authors.lastname: Ishizeki
authors.forename: Shintaro
authors.initials: S
authors.lastname: Nomura
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Kitamura
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Komori
mesh_terms: D000818:Animals; D016025:Bone Transplantation; D002358:Cartilage, Articular; D002454:Cell Differentiation; D019902:Chondrocytes / Q000166:cytology*; D017364:Collagenases / Q000235:genetics; D050659:Core Binding Factor Alpha 1 Subunit; D005260:Female; D005269:Femur / Q000166:cytology*; D015870:Gene Expression; D008297:Male; D053509:Matrix Metalloproteinase 13; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009363:Neoplasm Proteins; D009999:Ossification, Heterotopic; D010006:Osteoblasts / Q000166:cytology*; D053495:Osteopontin; D012795:Sialoglycoproteins / Q000235:genetics; D013154:Spleen; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D009363:Neoplasm Proteins; D012795:Sialoglycoproteins; C506896:Spp1 protein, mouse; D014157:Transcription Factors; D053495:Osteopontin; D017364:Collagenases; D053509:Matrix Metalloproteinase 13; C507081:Mmp13 protein, mouse