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Impaired remodeling phase of fracture repair in the absence of matrix metalloproteinase-2.

Lieu S, Hansen E, Dedini R, Behonick D, Werb Z, Miclau T, Marcucio R, Colnot C - Dis Model Mech (2010)

Bottom Line: In humans and mice, MMP2 deficiency causes a musculoskeletal phenotype.Unlike Mmp9- and Mmp13- mutations, which affect both cartilage and bone in the callus, the Mmp2- mutation delayed bone remodeling but not cartilage remodeling.However, we did not detect changes in expression of Mmp9, Mmp13 or Mt1-Mmp (Mmp14) in the calluses of Mmp2- mice compared with wild type by in situ hybridization, but we observed decreased expression of Timp2 in the calluses of Mmp2-, Mmp9- and Mmp13- mice.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, University of California at San Francisco, San Francisco, CA 94143, USA.

ABSTRACT
The matrix metalloproteinase (MMP) family of extracellular proteases performs crucial roles in development and repair of the skeleton owing to their ability to remodel the extracellular matrix (ECM) and release bioactive molecules. Most MMP- skeletal phenotypes that have been previously described are mild, thus permitting the assessment of their functions during bone repair in the adult. In humans and mice, MMP2 deficiency causes a musculoskeletal phenotype. In this study, we assessed the role of MMP2 during mouse fracture repair and compared it with the roles of MMP9 and MMP13. Mmp2 was expressed at low levels in the normal skeleton and was broadly expressed in the fracture callus. Treatment of wild-type mice with a general MMP inhibitor, GM6001, caused delayed cartilage remodeling and bone formation during fracture repair, which resembles the defect observed in Mmp9(-/-) mice. Unlike Mmp9- and Mmp13- mutations, which affect both cartilage and bone in the callus, the Mmp2- mutation delayed bone remodeling but not cartilage remodeling. This remodeling defect occurred without changes in either osteoclast recruitment or vascular invasion of the fracture callus compared with wild type. However, we did not detect changes in expression of Mmp9, Mmp13 or Mt1-Mmp (Mmp14) in the calluses of Mmp2- mice compared with wild type by in situ hybridization, but we observed decreased expression of Timp2 in the calluses of Mmp2-, Mmp9- and Mmp13- mice. In keeping with the skeletal phenotype of Mmp2- mice, MMP2 plays a role in the remodeling of new bone within the fracture callus and impacts later stages of bone repair compared with MMP9 and MMP13. Taken together, our results indicate that MMPs play unique and distinct roles in regulating skeletal tissue deposition and remodeling during fracture repair.

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Related in: MedlinePlus

MMP and Timp2 expression patterns in wild-type, Mmp13–/–, Mmp9–/– and Mmp13–/– mice during fracture repair. (A–L) Lack of MMP2 does not affect expression of Mmp9, Mmp13 or Mt1-Mmp but decreases Timp2 expression. (M–R) Similarly, lack of MMP9 does not affect expression of Mmp2, Mmp13 or Mt1-Mmp but decreases Timp2 expression and (S–X) lack of MMP13 does not affect expression of Mmp2, Mmp9 or Mt1-Mmp but decreases Timp2 expression. Boxed areas in A,G,M and S are shown at higher magnification in the panels on their right. Scale bars: 1 mm (A,G,M,S); 500 μm (B–F,H–L,N–R,T–X).
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f7-0040203: MMP and Timp2 expression patterns in wild-type, Mmp13–/–, Mmp9–/– and Mmp13–/– mice during fracture repair. (A–L) Lack of MMP2 does not affect expression of Mmp9, Mmp13 or Mt1-Mmp but decreases Timp2 expression. (M–R) Similarly, lack of MMP9 does not affect expression of Mmp2, Mmp13 or Mt1-Mmp but decreases Timp2 expression and (S–X) lack of MMP13 does not affect expression of Mmp2, Mmp9 or Mt1-Mmp but decreases Timp2 expression. Boxed areas in A,G,M and S are shown at higher magnification in the panels on their right. Scale bars: 1 mm (A,G,M,S); 500 μm (B–F,H–L,N–R,T–X).

Mentions: The Mmp2–/– fracture repair phenotype differed from the more severe bone repair phenotypes that we observed previously in Mmp9–/– and Mmp13–/– mice. We thus investigated whether MMP2 loss was compensated for by other MMPs that are expressed in the callus. When we compared Mmp2–/– and wild-type calluses, we did not observe qualitative differences in the expression profiles or expression levels of Mmp9, Mmp13 or Mt1-Mmp (Fig. 7A–E,G–K). However, we observed a decrease in Timp2 expression in the callus of Mmp2–/– mice compared with wild type (Fig. 7F,L). Likewise, Mmp2, Mmp13 and Mt1-Mmp expressions were unchanged in Mmp9–/– calluses compared with wild-type calluses, but Timp2 exhibited a decrease in the intensity of in situ hybridization signal (Fig. 7M–R). The expression of Timp2 was also decreased in Mmp13–/– calluses compared with wild-type calluses, whereas the expressions of Mmp2, Mmp9 and Mt1-Mmp were similar to wild type (Fig. 7S–X). These results thus indicate that the absence of Mmp2 might not impact the expression of other MMPs in cartilage and bone, suggesting that normal expression levels might be sufficient to partially compensate for the lack of Mmp2.


Impaired remodeling phase of fracture repair in the absence of matrix metalloproteinase-2.

Lieu S, Hansen E, Dedini R, Behonick D, Werb Z, Miclau T, Marcucio R, Colnot C - Dis Model Mech (2010)

MMP and Timp2 expression patterns in wild-type, Mmp13–/–, Mmp9–/– and Mmp13–/– mice during fracture repair. (A–L) Lack of MMP2 does not affect expression of Mmp9, Mmp13 or Mt1-Mmp but decreases Timp2 expression. (M–R) Similarly, lack of MMP9 does not affect expression of Mmp2, Mmp13 or Mt1-Mmp but decreases Timp2 expression and (S–X) lack of MMP13 does not affect expression of Mmp2, Mmp9 or Mt1-Mmp but decreases Timp2 expression. Boxed areas in A,G,M and S are shown at higher magnification in the panels on their right. Scale bars: 1 mm (A,G,M,S); 500 μm (B–F,H–L,N–R,T–X).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3046093&req=5

f7-0040203: MMP and Timp2 expression patterns in wild-type, Mmp13–/–, Mmp9–/– and Mmp13–/– mice during fracture repair. (A–L) Lack of MMP2 does not affect expression of Mmp9, Mmp13 or Mt1-Mmp but decreases Timp2 expression. (M–R) Similarly, lack of MMP9 does not affect expression of Mmp2, Mmp13 or Mt1-Mmp but decreases Timp2 expression and (S–X) lack of MMP13 does not affect expression of Mmp2, Mmp9 or Mt1-Mmp but decreases Timp2 expression. Boxed areas in A,G,M and S are shown at higher magnification in the panels on their right. Scale bars: 1 mm (A,G,M,S); 500 μm (B–F,H–L,N–R,T–X).
Mentions: The Mmp2–/– fracture repair phenotype differed from the more severe bone repair phenotypes that we observed previously in Mmp9–/– and Mmp13–/– mice. We thus investigated whether MMP2 loss was compensated for by other MMPs that are expressed in the callus. When we compared Mmp2–/– and wild-type calluses, we did not observe qualitative differences in the expression profiles or expression levels of Mmp9, Mmp13 or Mt1-Mmp (Fig. 7A–E,G–K). However, we observed a decrease in Timp2 expression in the callus of Mmp2–/– mice compared with wild type (Fig. 7F,L). Likewise, Mmp2, Mmp13 and Mt1-Mmp expressions were unchanged in Mmp9–/– calluses compared with wild-type calluses, but Timp2 exhibited a decrease in the intensity of in situ hybridization signal (Fig. 7M–R). The expression of Timp2 was also decreased in Mmp13–/– calluses compared with wild-type calluses, whereas the expressions of Mmp2, Mmp9 and Mt1-Mmp were similar to wild type (Fig. 7S–X). These results thus indicate that the absence of Mmp2 might not impact the expression of other MMPs in cartilage and bone, suggesting that normal expression levels might be sufficient to partially compensate for the lack of Mmp2.

Bottom Line: In humans and mice, MMP2 deficiency causes a musculoskeletal phenotype.Unlike Mmp9- and Mmp13- mutations, which affect both cartilage and bone in the callus, the Mmp2- mutation delayed bone remodeling but not cartilage remodeling.However, we did not detect changes in expression of Mmp9, Mmp13 or Mt1-Mmp (Mmp14) in the calluses of Mmp2- mice compared with wild type by in situ hybridization, but we observed decreased expression of Timp2 in the calluses of Mmp2-, Mmp9- and Mmp13- mice.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, University of California at San Francisco, San Francisco, CA 94143, USA.

ABSTRACT
The matrix metalloproteinase (MMP) family of extracellular proteases performs crucial roles in development and repair of the skeleton owing to their ability to remodel the extracellular matrix (ECM) and release bioactive molecules. Most MMP- skeletal phenotypes that have been previously described are mild, thus permitting the assessment of their functions during bone repair in the adult. In humans and mice, MMP2 deficiency causes a musculoskeletal phenotype. In this study, we assessed the role of MMP2 during mouse fracture repair and compared it with the roles of MMP9 and MMP13. Mmp2 was expressed at low levels in the normal skeleton and was broadly expressed in the fracture callus. Treatment of wild-type mice with a general MMP inhibitor, GM6001, caused delayed cartilage remodeling and bone formation during fracture repair, which resembles the defect observed in Mmp9(-/-) mice. Unlike Mmp9- and Mmp13- mutations, which affect both cartilage and bone in the callus, the Mmp2- mutation delayed bone remodeling but not cartilage remodeling. This remodeling defect occurred without changes in either osteoclast recruitment or vascular invasion of the fracture callus compared with wild type. However, we did not detect changes in expression of Mmp9, Mmp13 or Mt1-Mmp (Mmp14) in the calluses of Mmp2- mice compared with wild type by in situ hybridization, but we observed decreased expression of Timp2 in the calluses of Mmp2-, Mmp9- and Mmp13- mice. In keeping with the skeletal phenotype of Mmp2- mice, MMP2 plays a role in the remodeling of new bone within the fracture callus and impacts later stages of bone repair compared with MMP9 and MMP13. Taken together, our results indicate that MMPs play unique and distinct roles in regulating skeletal tissue deposition and remodeling during fracture repair.

Show MeSH
Related in: MedlinePlus