title: Subchondral bone changes and chondrogenic capacity of progenitor cells from subchondral bone in the collagenase-induced temporomandibular joints osteoarthritis rabbit model.
abstract: OBJECTIVE
  The goals of this study were to characterize subchondral bone changes, and to determine biological activity characteristics of progenitor cell populations from subchondral bone in the collagenase-induced temporomandibular joint osteoarthritis (TMJOA) rabbit model. Greater understanding of such pathological changes occurring in TMJOA samples is critical in the future treatment modalities regarding cartilage protection and repair. Furthermore, the use of progenitor cell populations in various cartilage regeneration strategies proves to be a fruitful avenue for research and clinical applications.
  
  
  METHODS
  Bone remodeling and anabolic activity of subchondral bone was evaluated by hematoxylin-eosin (H&E), Alcian blue-periodic acid-Schiff (AB-PAS) staining and immuohistochemical staining. The biological activity characteristics of progenitor cells were assessed by expressions of collagen type II, CD44, SOX-9 and MMP-9 by immunohistochemistry and Western blot analysis.
  
  
  RESULTS
  In most of the specimens, cartilage of the digested area displayed a reaction characterized by thickening of the cartilage cellular structure with retraction structure formation in the subchondral bone. Most of the specimens focuses on chondroid metaplasia were observed in the subchondral bone, promoting its remodeling, which could develop to endochondral ossification and increasing subchondral bone size. Meanwhile, immunohistochemistry analysis revealed that CD44 expressions in subchondral bone were most significantly increased in TMJOA at 2 weeks group (P < 0.01). And, at 4, 6 and 8 weeks groups, the osteochondral junction had completely disappeared by active subchondral bone remodeling, and collagen type II, CD44, SOX-9 and MMP-9 expressions in active subchondral bone region were significantly increased in TMJOA (P < 0.05). In addition, western blot analysis revealed that CD44 expression significantly emerged in subchondral bone region at 2 weeks group (P < 0.01). Meanwhile, SOX-9 expression emerged in all group, and the intensity was increased in the experimental groups (P < 0.05).
  
  
  CONCLUSIONS
  Our results suggest that the beneficial activation of progenitor cells and bone marrow stem cells in subchondral bone at early stage of TMJOA played an important role on renovation and remodeling of subchondral bone.
authors.affiliation: West China Hospital of Stomatology, State Key Laboratory of Oral Diseases, Sichuan University Chengdu 610041, Sichuan, China.
authors.forename: Guomin
authors.initials: G
authors.lastname: Wu
authors.affiliation: West China Hospital of Stomatology, State Key Laboratory of Oral Diseases, Sichuan University Chengdu 610041, Sichuan, China.
authors.forename: Songsong
authors.initials: S
authors.lastname: Zhu
authors.affiliation: Department of Orthodontics, Hospital of Stomatology, Jilin University Changchun, Jilin Province, China.
authors.forename: Xiumei
authors.initials: X
authors.lastname: Sun
authors.affiliation: West China Hospital of Stomatology, State Key Laboratory of Oral Diseases, Sichuan University Chengdu 610041, Sichuan, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Hu
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000473:pathology; D015153:Blotting, Western; D016723:Bone Remodeling / Q000502:physiology*; D019902:Chondrocytes / Q000166:cytology*; D020219:Chondrogenesis / Q000502:physiology; D017364:Collagenases / Q000633:toxicity; D007150:Immunohistochemistry; D008297:Male; D010003:Osteoarthritis / Q000473:pathology*; D011817:Rabbits; D013234:Stem Cells / Q000166:cytology*; D013705:Temporomandibular Joint Disorders / Q000473:pathology*
chemical_list: D017364:Collagenases
keywords: Subchondral bone; osteoporosis; progenitor cells; temporomandibular joint