title: Loss of MMP-2 disrupts skeletal and craniofacial development and results in decreased bone mineralization, joint erosion and defects in osteoblast and osteoclast growth.
abstract: The 'vanishing bone' or inherited osteolysis/arthritis syndromes represent a heterogeneous group of skeletal disorders characterized by mineralization defects of affected bones and joints. Differing in anatomical distribution, severity and associated syndromic features, gene identification in each 'vanishing bone' disorder should provide unique insights into genetic/molecular pathways contributing to the overall control of skeletal growth and development. We previously described and then demonstrated that the novel autosomal recessive osteolysis/arthritis syndrome, multicentric osteolysis with arthritis (MOA) (MIM #605156), was caused by inactivating mutations in the MMP2 gene [Al Aqeel, A., Al Sewairi, W., Edress, B., Gorlin, R.J., Desnick, R.J. and Martignetti, J.A. (2000) Inherited multicentric osteolysis with arthritis: A variant resembling Torg syndrome in a Saudi family. Am. J. Med. Genet., 93, 11-18.]. These in vivo results were counterintuitive and unexpected since previous in vitro studies suggested that MMP-2 overexpression and increased activity, not deficiency, would result in the bone and joint features of MOA. The apparent lack of a murine model [Itoh, T., Ikeda, T., Gomi, H., Nakao, S., Suzuki, T. and Itohara, S. (1997) Unaltered secretion of beta-amyloid precursor protein in gelatinase A (matrix metalloproteinase 2)-deficient mice. J. Biol. Chem., 272, 22389-22392.] has hindered studies on disease pathogenesis and, more fundamentally, in addressing the paradox of how functional loss of a single proteolytic enzyme results in an apparent increase in bone loss. Here, we report that Mmp2-/- mice display attenuated features of human MOA including progressive loss of bone mineral density, articular cartilage destruction and abnormal long bone and craniofacial development. Moreover, these changes are associated with markedly and developmentally restricted decreases in osteoblast and osteoclast numbers in vivo. Mmp2-/- mice have approximately 50% fewer osteoblasts and osteoclasts than control littermates at 4 days of life but these differences have nearly resolved by 4 weeks of age. In addition, despite normal cell numbers in vivo at 8 weeks of life, Mmp2-/- bone marrow cells are unable to effectively support osteoblast and osteoclast growth and differentiation in culture. Targeted inhibition of MMP-2 using siRNA in human SaOS2 and murine MC3T3 osteoblast cell lines resulted in decreased cell proliferation rates. Taken together, our findings suggest that MMP-2 plays a direct role in early skeletal development and bone cell growth and proliferation. Thus, Mmp2-/- mice provide a valuable biological resource for studying the pathophysiological mechanisms underlying the human disease and defining the in vivo physiological role of MMP-2.
authors.affiliation: Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, NY 10029, USA.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Mosig
authors.forename: Oonagh
authors.initials: O
authors.lastname: Dowling
authors.forename: Analisa
authors.initials: A
authors.lastname: DiFeo
authors.forename: Maria Celeste M
authors.initials: MC
authors.lastname: Ramirez
authors.forename: Ian C
authors.initials: IC
authors.lastname: Parker
authors.forename: Etsuko
authors.initials: E
authors.lastname: Abe
authors.forename: Janane
authors.initials: J
authors.lastname: Diouri
authors.forename: Aida Al
authors.initials: AA
authors.lastname: Aqeel
authors.forename: James D
authors.initials: JD
authors.lastname: Wylie
authors.forename: Samantha A
authors.initials: SA
authors.lastname: Oblander
authors.forename: Joseph
authors.initials: J
authors.lastname: Madri
authors.forename: Paolo
authors.initials: P
authors.lastname: Bianco
authors.forename: Suneel S
authors.initials: SS
authors.lastname: Apte
authors.forename: Mone
authors.initials: M
authors.lastname: Zaidi
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Doty
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Majeska
authors.forename: Mitchell B
authors.initials: MB
authors.lastname: Schaffler
authors.forename: John A
authors.initials: JA
authors.lastname: Martignetti
mesh_terms: D000818:Animals; D001168:Arthritis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D016723:Bone Remodeling / Q000235:genetics / Q000502:physiology; D001842:Bone and Bones / Q000002:abnormalities / Q000378:metabolism* / Q000503:physiopathology; D002113:Calcification, Physiologic / Q000235:genetics / Q000502:physiology*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D019465:Craniofacial Abnormalities / Q000201:enzymology / Q000235:genetics / Q000503:physiopathology; D017353:Gene Deletion; D006801:Humans; D007150:Immunohistochemistry; D007596:Joints / Q000378:metabolism* / Q000473:pathology; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D010006:Osteoblasts / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D010010:Osteoclasts / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014057:Tomography, X-Ray Computed
chemical_list: D034741:RNA, Small Interfering; D020778:Matrix Metalloproteinase 2