Professor and Chair
office: Brody 7N-100
B.A., Pomona College
Ph.D., University of Southern California
Postdoctoral Fellow, Tufts University School of Medicine
Modulation of cell-matrix interactions functions as a rheostat to alter cellular metabolism and signaling involved in tissue homeostasis, development and disease processes particularly in matrix-rich tissues such as cartilage. Hyaluronan (HA) serves to retain aggrecan in the cartilage matrix; but also provides the tether of these matrix components to the chondrocyte cell surface through its receptor CD44.
Chondrocytes directly isolated from embryonic chick cartilage retain HA-dependent pericellular coats. Chondrocytes from human osteoarthritic (OA) cartilage or passaged chondrocytes often lack coats but these can be recovered by conditions that promote the chondrocyte phenotype such as culture in 3D alginate beads. HA deficiencies can be generated experimentally by the use of HA oligosaccharide displacement or hyaluronidase treatment and often result in elevated production of MMPs as well as the release of NO and in cartilage explants, the loss of Safranin O staining. Reducing HA-cell interactions induced these catabolic cascades by activation of signaling pathways that involve NF-kappaB and p38 MAPK. On the anabolic arm, reduction in HA-cell interactions also diminished the cellular response to BMP7 but not to TGF-β1.
These results were extended to chondrocytes derived from Cd44-/- and WT mice. As in bovine and human chondrocytes, hyaluronidase treatment of mouse chondrocytes resulted in a nearly complete block of SMAD1/5/8 phosphorylation in response to BMP7. At physiological concentrations of BMP7, Cd44-/- murine chondrocytes were less responsive than WT cells both in terms of SMAD1 activation and the down-stream stimulation of aggrecan mRNA. Moreover, the reduced responsiveness of Cd44-/- chondrocytes to BMP7 could be rescued by plasmid or adenoviral overexpression of a human CD44 transgene. Conversely, CD44 siRNA knockdown in WT mouse chondrocytes affected a reduction in BMP7 responsiveness. These results demonstrate that HA-CD44 interactions do affect BMP7 signaling and are likely critical under physiological conditions--conditions such as matrix repair wherein autocrine responses rely on endogenous BMPs. Nonetheless, we also learned that the presence or absence of HA itself was of more importance to BMP7 responsiveness irrespective of the CD44 status of chondrocytes. Hyaluronidase-treated chondrocytes displayed very low responsiveness even in the presence of supraphysiological concentrations of BMP7 and, responsiveness could be rescued by pHAS2 transfection. However, the HA inhibitor 4-MU was far less effective at blocking BMP7 responsiveness. We are now exploring whether the release of hyaluronidase-derived HA fragments may induce signaling events directly affecting SMAD1 phosphorylation.
Interestingly, CD44 may again be part of this hyaluronan story based on its susceptibility to proteolytic fragmentation. Substantial levels of C-terminal CD44 fragments are present in direct extracts of OA cartilage and, chondrocytes obtained from OA patients exhibit substantially enhanced CD44 proteolysis that can be blocked by the MMP inhibitor GM6001 and release of the CD44 intracellular domain (ICD) blocked by gamma-secretase inhibitors. CD44 shedding also releases N-terminal extracellular domain (ECD) fragments that not only reduce cell-HA interactions but may also activate the same pathways as hyaluronidase-derived HA fragments.
Our results support the paradigm that information from the extracellular matrix is communicated through cellular receptors that provide signals that ultimately affect cell metabolism. The biological consequence of disruption of the interaction of hyaluronan with functional CD44 receptors is the induction of matrix turnover as well as matrix biosynthesis -- replicating a chondrocyte response that partners attempted repair with enhanced catabolism, hallmarks of osteoarthritis and other degenerative diseases.
Knudson, C.B. and W. Knudson. 1993. Hyaluronan binding proteins in development, tissue homeostasis and disease. FASEB J. 7: 1233-1241
Knudson, C.B. and W. Knudson. 2001. Cartilage proteoglycans. Seminars in Cell & Developmental Biology 12: 69-78.
Knudson, C.B. 2003. Hyaluronan and CD44: Strategic players for cell-matrix interactions during chondrogenesis and matrix assembly. Birth Defects Research Part C: Embryo Today 69: 174-196.
Knudson, W. and C.B. Knudson. 2005. The hyaluronan receptor, CD44 – An update. Glycoforum – Hyaluronan Today.
Knudson, C.B. 1993. Hyaluronan receptor-directed assembly of chondrocyte pericellular matrix. J. Cell Biol. 120: 825-834.
Knudson W., E. Bartnik, and C.B. Knudson. 1993. Assembly of pericellular matrix by COS-7 cells transfected with CD44 homing receptor genes. Proc. Natl. Acad. Sci. USA 90: 4003-4007.
Peterson, R.S., R.A. Andhare, K.T. Rousche, W. Knudson, W. Wang, J.B. Grossfield, R.O. Thomas, R.E. Hollingsworth, and C.B. Knudson. 2004. CD44 modulates Smad1 activation in the BMP-7 signaling pathway. J. Cell Biol. 166: 1081-1091.
Andhare, R.A., N. Takahashi, W. Knudson, and C.B. Knudson. 2009. Hyaluronan promotes the chondrocyte response to BMP-7. Osteoarthr. Cartilage 17: 906-916.
Takahashi N., C.B. Knudson, S. Thankamony, W. Ariyoshi, L. Mellor, H.-J. Im, and W. Knudson. 2010. Induction of CD44 cleavage in articular chondrocytes. Arthritis Rheum. 62: 1338-1348.
Mellor, L., C.B. Knudson, D. Hida, E.B. Askew, and W. Knudson. 2013. Intracellular domain fragment of CD44 alters CD44 function in chondrocytes.J. Biol. Chem. 288: 25838-25850.
Luo N., W. Knudson, E.B. Askew, R.M. Veluci, and C.B. Knudson. 2014. CD44 and hyaluronan promote the bone morphogenetic protein 7 signaling response in murine chondrocytes. Arthritis Rheum. 66:1547-1558.
"Hyaluronan-Cell Interactions in Cartilage" (NIH R01 AR039507); Cheryl B. Knudson, Principal Investigator; National Institute of Arthritis and Musculoskeletal and Skin Diseases.
Location: 7N-100, 7E-118, & 8E-16
|Crystal Hooper||Admin. Support Assistantfirstname.lastname@example.org|
|Ann Sadler||Admin. Support Assistantemail@example.com|
|Joani Zary-Oswald||Research Technician, Core Labfirstname.lastname@example.org|
|Dean J. Aguiar, Ph.D.||Director of Product Development||BioMimetic Therapeutics, Franklin, TN|
|Roma A. Andhare, Ph.D.||Assistant Professor||Department of Chemistry, Oakton Community College, Des Plaines, IL|
|Ankit Desai, M.D.||Assistant Professor||Section of Cardiology, College of Medicine, University of Illinois at Chicago, Chicago, IL|
|Stanca Iacob, Ph.D., M.D.||Research Associate||Comprehensive Transplant Center, Department of Surgery, Northwestern University, Chicago, IL|
|Na Luo, Ph.D.||Assistant Professor||School of Medicine, Nankai University, Tianjin, P.R. China|
|Michael P. Maleski, Ph.D.||Deceased|
|Ghada A. Nofal, Ph.D.||Pharmacist||Chicago, IL|
|Maiko Ohno-Nakahara, Ph.D., D.D.S.||Dentist||Kobe, Japan|
|Pedram Pouryazdanparast, M.D.||Anatomic Pathologist||Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, IL|
|Eka A. Rapava, Ph.D.||Professor Emeritus||Department of Biochemistry, Tbilisi State Medical University, Tbilisi, Georgia|
|Kathleen T. Rousche, Ph.D.||Program Director||Office of Translational Alliances and Coordination, Division of Extramural Research Activities, National Heart, Lung and Blood Institute, Bethesda, MD|