The ERK5 and ERK1/2 signaling pathways play opposing regulatory roles during chondrogenesis of adult human bone marrow-derived multipotent progenitor cells.
Adult human bone marrow-derived multipotent progenitor cells (MPCs) are able to differentiate into a variety of specialized cell types, including chondrocytes, and are considered a promising candidate cell source for use in cartilage tissue engineering. In this study, we examined the regulation of MPC chondrogenesis by mitogen-activated protein kinases in an attempt to better understand how to generate hyaline cartilage in the laboratory that more closely resembles native tissue. Specifically, we employed the high-density pellet culture model system to assess the roles of ERK5 and ERK1/2 pathway signaling in MPC chondrogenesis. Western blotting revealed that high levels of ERK5 phosphorylation correlate with low levels of MPC chondrogenesis and that as TGF-beta 3-enhanced MPC chondrogenesis proceeds, phospho-ERK5 levels steadily decline. Conversely, levels of phospho-ERK1/2 paralleled the progression of MPC chondrogenesis. siRNA-mediated knockdown of ERK5 pathway components MEK5 and ERK5 resulted in increased MPC pellet mRNA transcript levels of the cartilage-characteristic marker genes SOX9, COL2A1, AGC, L-SOX5, and SOX6, as well as enhanced accumulation of SOX9 protein, collagen type II protein, and Alcian blue-stainable proteoglycan. In contrast, knockdown of ERK1/2 pathway members MEK1 and ERK1 decreased expression of all chondrogenic markers tested. Finally, overexpression of MEK5 and ERK5 also depressed MPC chondrogenesis, as indicated by diminished activity of a co-transfected collagen II promoter-luciferase reporter construct. In conclusion, our results suggest a novel role for the ERK5 pathway as an important negative regulator of adult human MPC chondrogenesis and illustrate that the ERK5 and ERK1/2 kinase cascades play opposing roles regulating MPC cartilage formation.
Cartilage Biology and Orthopaedics Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, USA.
Brent E
BE
Bobick
Alexander I
AI
Matsche
Faye H
FH
Chen
Rocky S
RS
Tuan
D053687:Adult Stem Cells / Q000201:enzymology*; D000368:Aged; D000369:Aged, 80 and over; D001854:Bone Marrow Cells / Q000201:enzymology*; D002356:Cartilage / Q000378:metabolism; D002454:Cell Differentiation; D002478:Cells, Cultured; D020219:Chondrogenesis / Q000235:genetics; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D048671:MAP Kinase Kinase 5 / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008297:Male; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D048054:Mitogen-Activated Protein Kinase 7 / Q000235:genetics / Q000378:metabolism*; D039902:Multipotent Stem Cells / Q000201:enzymology*; D010766:Phosphorylation; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D013234:Stem Cells / Q000201:enzymology*; D013997:Time Factors; D014162:Transfection; D053782:Transforming Growth Factor beta3 / Q000378:metabolism
D012333:RNA, Messenger; D053782:Transforming Growth Factor beta3; D016222:Fibroblast Growth Factor 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048054:Mitogen-Activated Protein Kinase 7; D048369:MAP Kinase Kinase 1; D048671:MAP Kinase Kinase 5; C482563:MAP2K5 protein, human