Hematopoietic disorders such as bone marrow failure, immune dysfunction, and certain cancers, may involve a link between the endochondral skeleton and marrow. The objective of this renewal is to provide a mechanistic basis for the skeleto-hematopoietic link, by addressing how a hematopoietic marrow environment may form by replacement of hypertrophic cartilage by bone and marrow during endochondral ossification (EO). This proposal stems from our transgenic (Tg) and null mice for collagen X, a matrix protein expressed in hypertrophic cartilage prior to EO. Murine skeleto-hematopoietic defects include growth plate compressions, osteopenia, marrow aplasia, and altered blood cell differentiation. We propose that collagen X provides a structural network that is stabilized by proteoglycans (PGs)/glycosaminoglycans (GAGs), and sequesters cytokines. Network disruption causes redistribution of growth plate components and a cytokine imbalance; the latter may cause the hemato-poietic defects. To test this hypothesis we will: 1) Identify the defective cellular component in the marrow environment of collagen X mice by co-cultures of hematopoietic stern cells (HSCs) with stromal cells, hypertrophic chondrocytes, and osteoblasts, and test if marrow transplantation can rescue the hematopoietic defects; 2) Identify which PGs/GAGs are altered in growth plate/marrow junctions by immunohistochemistry and electron microscopy, test if they bind collagen X by affinity coelectrophoreisis, and assess the role of these interactions in hematopoiesis by co-cultures of HSCs and hypertrophic chondrocytes GAG biosynthesis modulators; 3) Examine the relationship between the severity of the skeleto-hematopoietic phenotype and dysregulated cytokine expression by macrophage cytokine production, identify the defect in immune response initiation/regulation by endotoxin challenge, ascertain dysregulated cytokines by blot arrays, identify the tissue source of aberrant cytokine production, and induce/block the disease phenotype by injection of cytokines or neutralizing antibodies; and 4) Test if other murine models with altered hypertrophic cartilage (Grg5 null & Snell dwarfs) have similar hematopoietic defects caused by cytokine dysregulation. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK057904-07
Application #
7049328
Study Section
Skeletal Biology Development and Disease Study Section (SBDD)
Program Officer
Bishop, Terry Rogers
Project Start
2000-04-01
Project End
2009-03-31
Budget Start
2006-04-01
Budget End
2007-03-31
Support Year
7
Fiscal Year
2006
Total Cost
$443,611
Indirect Cost
Name
University of Pennsylvania
Department
Veterinary Sciences
Type
Schools of Veterinary Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Sweeney, Elizabeth; Roberts, Douglas; Corbo, Tina et al. (2010) Congenic mice confirm that collagen X is required for proper hematopoietic development. PLoS One 5:e9518
Sweeney, E; Campbell, M; Watkins, K et al. (2008) Altered endochondral ossification in collagen X mouse models leads to impaired immune responses. Dev Dyn 237:2693-704
Rodgers, Kathryn D; San Antonio, James D; Jacenko, Olena (2008) Heparan sulfate proteoglycans: a GAGgle of skeletal-hematopoietic regulators. Dev Dyn 237:2622-42
Rodgers, Kathryn D; Sasaki, Takako; Aszodi, Attila et al. (2007) Reduced perlecan in mice results in chondrodysplasia resembling Schwartz-Jampel syndrome. Hum Mol Genet 16:515-28
Campbell, Michelle R; Gress, Catherine J; Appleman, Elizabeth H et al. (2004) Chicken collagen X regulatory sequences restrict transgene expression to hypertrophic cartilage in mice. Am J Pathol 164:487-99
Jacenko, Olena; Roberts, Douglas W; Campbell, Michelle R et al. (2002) Linking hematopoiesis to endochondral skeletogenesis through analysis of mice transgenic for collagen X. Am J Pathol 160:2019-34
Jacenko, O; Chan, D; Franklin, A et al. (2001) A dominant interference collagen X mutation disrupts hypertrophic chondrocyte pericellular matrix and glycosaminoglycan and proteoglycan distribution in transgenic mice. Am J Pathol 159:2257-69