title: Osteopontin-CD44v6 interaction mediates calcium deposition via phospho-Akt in valve interstitial cells from patients with noncalcified aortic valve sclerosis.
abstract: OBJECTIVE
  The activation of valve interstitial cells (VICs) toward an osteogenic phenotype characterizes aortic valve sclerosis, the early asymptomatic phase of calcific aortic valve disease. Osteopontin is a phosphorylated acidic glycoprotein that accumulates within the aortic leaflets and labels VIC activation even in noncalcified asymptomatic patients. Despite this, osteopontin protects VICs against in vitro calcification. Here, we hypothesize that the specific interaction of osteopontin with CD44v6, and the related intracellular pathway, prevents calcium deposition in human-derived VICs from patients with aortic valve sclerosis.
  
  
  RESULTS
  On informed consent, 23 patients and 4 controls were enrolled through the cardiac surgery and heart transplant programs. Human aortic valves and VICs were tested for osteogenic transdifferentiation, ex vivo and in vitro. Osteopontin-CD44 interaction was analyzed using proximity ligation assay and the signaling pathways investigated. A murine model based on angiotensin II infusion was used to mimic early pathological remodeling of the aortic valves. We report osteopontin-CD44 functional interaction as a hallmark of early stages of calcific aortic valve disease. We demonstrated that osteopontin-CD44 interaction mediates calcium deposition via phospho-Akt in VICs from patients with noncalcified aortic valve sclerosis. Finally, microdissection analysis of murine valves shows increased cusp thickness in angiotensin II-treated mice versus saline infused along with colocalization of osteopontin and CD44 as seen in human lesions.
  
  
  CONCLUSIONS
  Here, we unveil a specific protein-protein association and intracellular signaling mechanisms of osteopontin. Understanding the molecular mechanisms of early VIC activation and calcium deposition in asymptomatic stage of calcific aortic valve disease could open new prospective for diagnosis and therapeutic intervention.
authors: From the Department of Surgery, Perelman School of Medicine at University of Pennsylvania, Philadelphia (P.P., E.B., J.B.G., E.K.L., R.C.G., J.H.G., J.E.B., G.F.); Centro Cardiologico Monzino IRCCS, Milan, Italy (P.P.); Columbia University-Valley Heart Center, Ridgewood, NJ (J.B.G.); and Department of Biomedical Engineering, University of Texas at Austin (M.S.S.).
authors: Paolo
authors: P
authors: Poggio
authors: From the Department of Surgery, Perelman School of Medicine at University of Pennsylvania, Philadelphia (P.P., E.B., J.B.G., E.K.L., R.C.G., J.H.G., J.E.B., G.F.); Centro Cardiologico Monzino IRCCS, Milan, Italy (P.P.); Columbia University-Valley Heart Center, Ridgewood, NJ (J.B.G.); and Department of Biomedical Engineering, University of Texas at Austin (M.S.S.).
authors: Emanuela
authors: E
authors: Branchetti
authors: From the Department of Surgery, Perelman School of Medicine at University of Pennsylvania, Philadelphia (P.P., E.B., J.B.G., E.K.L., R.C.G., J.H.G., J.E.B., G.F.); Centro Cardiologico Monzino IRCCS, Milan, Italy (P.P.); Columbia University-Valley Heart Center, Ridgewood, NJ (J.B.G.); and Department of Biomedical Engineering, University of Texas at Austin (M.S.S.).
authors: Juan B
authors: JB
authors: Grau
authors: From the Department of Surgery, Perelman School of Medicine at University of Pennsylvania, Philadelphia (P.P., E.B., J.B.G., E.K.L., R.C.G., J.H.G., J.E.B., G.F.); Centro Cardiologico Monzino IRCCS, Milan, Italy (P.P.); Columbia University-Valley Heart Center, Ridgewood, NJ (J.B.G.); and Department of Biomedical Engineering, University of Texas at Austin (M.S.S.).
authors: Eric K
authors: EK
authors: Lai
authors: From the Department of Surgery, Perelman School of Medicine at University of Pennsylvania, Philadelphia (P.P., E.B., J.B.G., E.K.L., R.C.G., J.H.G., J.E.B., G.F.); Centro Cardiologico Monzino IRCCS, Milan, Italy (P.P.); Columbia University-Valley Heart Center, Ridgewood, NJ (J.B.G.); and Department of Biomedical Engineering, University of Texas at Austin (M.S.S.).
authors: Robert C
authors: RC
authors: Gorman
authors: From the Department of Surgery, Perelman School of Medicine at University of Pennsylvania, Philadelphia (P.P., E.B., J.B.G., E.K.L., R.C.G., J.H.G., J.E.B., G.F.); Centro Cardiologico Monzino IRCCS, Milan, Italy (P.P.); Columbia University-Valley Heart Center, Ridgewood, NJ (J.B.G.); and Department of Biomedical Engineering, University of Texas at Austin (M.S.S.).
authors: Joseph H
authors: JH
authors: Gorman
authors: From the Department of Surgery, Perelman School of Medicine at University of Pennsylvania, Philadelphia (P.P., E.B., J.B.G., E.K.L., R.C.G., J.H.G., J.E.B., G.F.); Centro Cardiologico Monzino IRCCS, Milan, Italy (P.P.); Columbia University-Valley Heart Center, Ridgewood, NJ (J.B.G.); and Department of Biomedical Engineering, University of Texas at Austin (M.S.S.).
authors: Michael S
authors: MS
authors: Sacks
authors: From the Department of Surgery, Perelman School of Medicine at University of Pennsylvania, Philadelphia (P.P., E.B., J.B.G., E.K.L., R.C.G., J.H.G., J.E.B., G.F.); Centro Cardiologico Monzino IRCCS, Milan, Italy (P.P.); Columbia University-Valley Heart Center, Ridgewood, NJ (J.B.G.); and Department of Biomedical Engineering, University of Texas at Austin (M.S.S.).
authors: Joseph E
authors: JE
authors: Bavaria
authors: From the Department of Surgery, Perelman School of Medicine at University of Pennsylvania, Philadelphia (P.P., E.B., J.B.G., E.K.L., R.C.G., J.H.G., J.E.B., G.F.); Centro Cardiologico Monzino IRCCS, Milan, Italy (P.P.); Columbia University-Valley Heart Center, Ridgewood, NJ (J.B.G.); and Department of Biomedical Engineering, University of Texas at Austin (M.S.S.). giovanni.ferrari@uphs.upenn.edu.
authors: Giovanni
authors: G
authors: Ferrari
mesh_terms: D000804:Angiotensin II / Q000633:toxicity; D000818:Animals; D001021:Aortic Valve / Q000378:metabolism / Q000473:pathology*; D001024:Aortic Valve Stenosis / Q000378:metabolism* / Q000473:pathology; D019149:Bioreactors; D055415:Bone Morphogenetic Protein 4 / Q000494:pharmacology; D002114:Calcinosis / Q000378:metabolism* / Q000473:pathology; D002118:Calcium / Q000378:metabolism*; D054338:Cell Transdifferentiation; D004195:Disease Models, Animal; D018450:Disease Progression; D006801:Humans; D018960:Hyaluronan Receptors / Q000737:chemistry / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010012:Osteogenesis; D053495:Osteopontin / Q000737:chemistry / Q000502:physiology*; D010766:Phosphorylation; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D055415:Bone Morphogenetic Protein 4; C112697:CD44v6 antigen; D018960:Hyaluronan Receptors; C506896:Spp1 protein, mouse; D053495:Osteopontin; D000804:Angiotensin II; D051057:Proto-Oncogene Proteins c-akt; D002118:Calcium
keywords: aortic valve; osteopontin