Roles of Chondrocytes in Endochondral Bone Formation and Fracture Repair

Abstract Ephrin B2 is critical for endochondral bone development. In this study, we investigated its role in fracture repair by deleting ephrin B2 in type II collagen (Col.2) expressing cells. We used a nonstable tibia fracture model to evaluate fracture repair at 3 sites: intramembranous bone formation, endochondral bone formation, and intramedullary bone formation. We observed that during fracture repair, deletion of ephrin B2 impaired periosteal stem cell activation, inhibited their proliferation, decreased their survival, and blocked their differentiation into osteoblasts and chondrocytes. In addition, deletion of ephrin B2 decreased vascular endothelial growth factor production as well as vascular invasion into the fracture site. These changes led to reduced cartilage to bone conversion in the callus with decreased new bone formation, resulting in impaired fracture repair. Our data indicate that ephrin B2 in Col2-expressing cells is a critical regulator of fracture repair, pointing to a new and potentially targetable mechanism to enhance fracture repair.

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Faculty Opinions recommendation of Intraflagellar transport is essential for endochondral bone formation.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1059698.511609 ◽

2007 ◽

Author(s):

Peter Scambler

Keyword(s):

Bone Formation ◽

Intraflagellar Transport ◽

Endochondral Bone Formation ◽

Endochondral Bone

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The culture microenvironment of juvenile idiopathic arthritis synovial fibroblasts is favorable for endochondral bone formation through BMP4 and repressed by chondrocytes

Pediatric Rheumatology ◽

10.1186/s12969-021-00556-8 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Megan M. Simonds ◽

Amanda R. Schlefman ◽

Suzanne M. McCahan ◽

Kathleen E. Sullivan ◽

Carlos D. Rose ◽

...

Keyword(s):

Juvenile Idiopathic Arthritis ◽

Bone Formation ◽

Synovial Fibroblasts ◽

Conditioned Media ◽

Endochondral Bone Formation ◽

Endochondral Bone ◽

Member Gene ◽

Bmp Antagonist ◽

Fibroblast Like Synoviocytes ◽

Tgfβ Superfamily

Abstract Background We examined influences of conditioned media from chondrocytes (Ch) on juvenile idiopathic arthritis synovial fibroblasts (JFLS) and potential for JFLS to undergo endochondral bone formation (EBF). Methods Primary cells from three control fibroblast-like synoviocytes (CFLS) and three JFLS were cultured in Ch-conditioned media and compared with untreated fibroblast-like synoviocytes (FLS). RNA was analyzed by ClariomS microarray. FLS cells cultured in conditioned media were exposed to either TGFBR1 inhibitor LY3200882 or exogenous BMP4 and compared with FLS cultured in conditioned media from Ch (JFLS-Ch). Media supernatants were analyzed by ELISA. Results In culture, JFLS downregulate BMP2 and its receptor BMPR1a while upregulating BMP antagonists (NOG and CHRD) and express genes (MMP9, PCNA, MMP12) and proteins (COL2, COLX, COMP) associated with chondrocytes. Important TGFβ superfamily member gene expression (TGFBI, MMP9, COL1A1, SOX6, and MMP2) is downregulated when JFLS are cultured in Ch-conditioned media. COL2, COLX and COMP protein expression decreases in JFLS-Ch. BMP antagonist protein (NOG, CHRD, GREM, and FST) secretion is significantly increased in JFLS-Ch. Protein phosphorylation increases in JFLS-Ch exposed to exogenous BMP4, and chondrocyte-like phenotype is restored in BMP4 presence, evidenced by increased secretion of COL2 and COLX. Inhibition of TGFBR1 in JFLS-Ch results in overexpression of COL2. Conclusions JFLS are chondrocyte-like, and Ch-conditioned media can abrogate this phenotype. The addition of exogenous BMP4 causes JFLS-Ch to restore this chondrocyte-like phenotype, suggesting that JFLS create a microenvironment favorable for endochondral bone formation, thereby contributing to joint growth disturbances in juvenile idiopathic arthritis.

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Intraflagellar transport is essential for endochondral bone formation

Development ◽

10.1242/dev.02732 ◽

2007 ◽

Vol 134 (2) ◽

pp. 307-316 ◽

Cited By ~ 238

Author(s):

C. J. Haycraft ◽

Q. Zhang ◽

B. Song ◽

W. S. Jackson ◽

P. J. Detloff ◽

...

Keyword(s):

Bone Formation ◽

Intraflagellar Transport ◽

Endochondral Bone Formation ◽

Endochondral Bone

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Osteoblast‐Specific Loss of IGF1R Signaling Results in Impaired Endochondral Bone Formation During Fracture Healing

Journal of Bone and Mineral Research ◽

10.1002/jbmr.2510 ◽

2015 ◽

Vol 30 (9) ◽

pp. 1572-1584 ◽

Cited By ~ 32

Author(s):

Tao Wang ◽

Yongmei Wang ◽

Alicia Menendez ◽

Chak Fong ◽

Muriel Babey ◽

...

Keyword(s):

Bone Formation ◽

Fracture Healing ◽

Endochondral Bone Formation ◽

Endochondral Bone ◽

Specific Loss ◽

Igf1r Signaling

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Conditional Deletion of Prolyl Hydroxylase Domain-Containing Protein 2 (Phd2) Gene Reveals Its Essential Role in Chondrocyte Function and Endochondral Bone Formation

Endocrinology ◽

10.1210/en.2015-1473 ◽

2016 ◽

Vol 157 (1) ◽

pp. 127-140 ◽

Cited By ~ 11

Author(s):

Shaohong Cheng ◽

Weirong Xing ◽

Sheila Pourteymoor ◽

Jan Schulte ◽

Subburaman Mohan

Keyword(s):

Bone Formation ◽

Growth Plate ◽

Prolyl Hydroxylase ◽

Conditional Knockout ◽

Hypertrophic Chondrocytes ◽

Endochondral Bone Formation ◽

Bone Surface ◽

Endochondral Bone ◽

Prolyl Hydroxylase Domain

Abstract The hypoxic growth plate cartilage requires hypoxia-inducible factor (HIF)-mediated pathways to maintain chondrocyte survival and differentiation. HIF proteins are tightly regulated by prolyl hydroxylase domain-containing protein 2 (Phd2)-mediated proteosomal degradation. We conditionally disrupted the Phd2 gene in chondrocytes by crossing Phd2 floxed mice with type 2 collagen-α1-Cre transgenic mice and found massive increases (>50%) in the trabecular bone mass of long bones and lumbar vertebra of the Phd2 conditional knockout (cKO) mice caused by significant increases in trabecular number and thickness and reductions in trabecular separation. Cortical thickness and tissue mineral density at the femoral middiaphysis of the cKO mice were also significantly increased. Dynamic histomorphometric analyses revealed increased longitudinal length and osteoid surface per bone surface in the primary spongiosa of the cKO mice, suggesting elevated conversion rate from hypertrophic chondrocytes to mineralized bone matrix as well as increased bone formation in the primary spongiosa. In the secondary spongiosa, bone formation measured by mineralizing surface per bone surface and mineral apposition rate were not changed, but resorption was slightly reduced. Increases in the mRNA levels of SRY (sex determining region Y)-box 9, osterix (Osx), type 2 collagen, aggrecan, alkaline phosphatase, bone sialoprotein, vascular endothelial growth factor, erythropoietin, and glycolytic enzymes in the growth plate of cKO mice were detected by quantitative RT-PCR. Immunohistochemistry revealed an increased HIF-1α protein level in the hypertrophic chondrocytes of cKO mice. Infection of chondrocytes isolated from Phd2 floxed mice with adenoviral Cre resulted in similar gene expression patterns as observed in the cKO growth plate chondrocytes. Our findings indicate that Phd2 suppresses endochondral bone formation, in part, via HIF-dependent mechanisms in mice.

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