Published online before print May 8, 2008

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Copyright © 2008 American Society for Investigative Pathology
American Journal of Pathology, doi:10.2353/ajpath.2008.071094

Accepted for publication February 14, 2008.

Article

Skeletal Abnormalities in Mice Lacking Extracellular Matrix Proteins, Thrombospondin-1, Thrombospondin-3, Thrombospondin-5, and Type IX Collagen

Karen L. Posey^*, Kurt Hankenson, Alka C. Veerisetty^*, Paul Bornstein, Jack Lawler, and Jacqueline T. Hecht^*¶@

From the Department of Pediatrics,* University of Texas Medical School, Houston, Texas; the University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania; the Departments of Biochemistry and Medicine, University of Washington, Seattle, Washington; the Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts; and the Shriners Hospital for Children,^¶ Houston, Texas

^@ To whom correspondence should be addressed. E-mail: Jacqueline.T.Hecht{at}uth.tmc.edu.

	Abstract

Thrombospondin-5 (TSP5) is a large extracellular matrix glycoprotein found in musculoskeletal tissues. TSP5 mutations cause two skeletal dysplasias, pseudoachondroplasia and multiple epiphyseal dysplasia; both show a characteristic growth plate phenotype with retention of TSP5, type IX collagen (Col9), and matrillin-3 in the rough endoplasmic reticulum. Whereas most studies focus on defining the disease process, few functional studies have been performed. TSP5 knockout mice have no obvious skeletal abnormalities, suggesting that TSP5 is not essential in the growth plate and/or that other TSPs may compensate. In contrast, Col9 knockout mice have diminished matrillin-3 levels in the extracellular matrix and early-onset osteoarthritis. To define the roles of TSP1, TSP3, TSP5, and Col9 in the growth plate, all knockout and combinatorial strains were analyzed using histomorphometric techniques. While significant alterations in growth plate organization were found in certain single knockout mouse strains, skeletal growth was only mildly disturbed. In contrast, dramatic changes in growth plate organization in TSP3/5/Col9 knockout mice resulted in a 20% reduction in limb length, corresponding to similar short stature in humans. These studies show that type IX collagen may regulate growth plate width; TSP3, TSP5, and Col9 appear to contribute to growth plate organization; and TSP1 may help define the timing of growth plate closure when other extracellular proteins are absent.