title: Calcification and cellularity in human aortic heart valve tissue determine the differentiation of bone-marrow-derived cells.
abstract: Human bone-marrow-derived mesenchymal stem cells (MSC) are responsible the remodeling of human tissue. However, damaged aortic valves are lack the ability to regenerate which is an active cell-mediated process. Diseased aortic valve remodeling has similarities even to bone formation. In this study, the prerequisites for cultured MSCs to undergo osteoblastic differentiation on aortic valves were explored. An ex vivo model using a human aortic valve microenvironment was developed. The expression of type I procollagen, alkaline phosphatase activity, osteocalcin secretion and osteocalcin immunostaining were studied to evaluate the induction of osteogenesis of the MSCs on noncalcified and calcified human aortic valves. Aortic valves were exposed to freeze-thaw injury to devitalize valves in order to separately study the role of valve matrix vs. endothelial cells in the explants. Thus, valves were assigned to 1 of 4 treatment groups: noncalcified uninjured valves, calcified uninjured valves, noncalcified injured and calcified injured. Finally, valves were decalcified to separately explore the effect of a calcified matrix on the osteogenesis. In this co-culture system, the noncalcified uninjured valves inhibited osteogenesis of MSCs, whereas the calcified valves promoted differentiation towards osteoblastic lineage. Devitalization of the valve matrix inflicted a significant increase in the osteogenesis of co-cultured MSCs. Calcified matrix in the valves seemed to have a role in the spontaneous osteogenesis of the MSCs. This spontaneous matrix induced differentiation of MSCs into osteoblast lineage could not be inhibited by pravastatin, indomethacin or tetracycline. In conclusion, these results suggest that interactions between MSCs and aortic valve matrix components and cells modulate MSC phenotype in this environment. Further studies are required to characterize this interesting phenomenon in greater detail.
authors.affiliation: Clinical Research Center, Department of Surgery, University of Oulu, FI-90014 Oulun Yliopisto, Finland. haleskel@paju.oulu.fi
authors.forename: Hannu-Ville
authors.initials: HV
authors.lastname: Leskelä
authors.forename: Jari
authors.initials: J
authors.lastname: Satta
authors.forename: Jani
authors.initials: J
authors.lastname: Oiva
authors.forename: Heidi
authors.initials: H
authors.lastname: Eriksen
authors.forename: Risteli
authors.initials: R
authors.lastname: Juha
authors.forename: Paula
authors.initials: P
authors.lastname: Korkiamäki
authors.forename: Kaisa K
authors.initials: KK
authors.lastname: Ivaska
authors.forename: Ylermi
authors.initials: Y
authors.lastname: Soini
authors.forename: Petri
authors.initials: P
authors.lastname: Lehenkari
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D001021:Aortic Valve / Q000502:physiology*; D015415:Biomarkers / Q000032:analysis; D001854:Bone Marrow Cells / Q000502:physiology*; D002114:Calcinosis / Q000503:physiopathology*; D018797:Cell Cycle Proteins / Q000494:pharmacology; D002454:Cell Differentiation; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D059630:Mesenchymal Stem Cells / Q000187:drug effects / Q000502:physiology*; D008954:Models, Biological; D010006:Osteoblasts / Q000502:physiology; D010012:Osteogenesis; D020648:Peptide Elongation Factor 1
chemical_list: D000900:Anti-Bacterial Agents; D000894:Anti-Inflammatory Agents, Non-Steroidal; D015415:Biomarkers; D018797:Cell Cycle Proteins; C503234:EEF1A2 protein, human; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D020648:Peptide Elongation Factor 1