title: Effects of pH on human bone marrow stromal cells in vitro: implications for tissue engineering of bone.
abstract: The objective of this study was to address the hypothesis that changes in extracellular pH alter collagen gene expression, collagen synthesis, and alkaline phosphatase activity in bone marrow stromal cells (BMSCs). Potential effects of pH on cell function are of particular importance for tissue engineering because considerable effort is being placed on engineering biodegradable polymers that may generate a local acidic microenvironment on degradation. Human and murine single-cell marrow suspensions were plated at a density of 2 x 10(4) cells/cm(2). After 7 days in culture, the pH of the culture medium was adjusted to one of six ranges: > or = 7.8, 7.5.-7.7, 7.2-7.4, 6.9-7.1, 6.6-6.8, or < or = 6.5. After 48 h of exposure to an altered pH, alkaline phosphatase activity and collagen synthesis decreased significantly with decreasing pH. This decrease was two-to threefold as pH decreased from 7.5 to 6.6. In contrast, alpha1(I) procollagen mRNA levels increased two- to threefold as pH was decreased. The trend in osteocalcin mRNA expression was opposite to that of collagen. Small shifts in extracellular pH led to significant changes in the ability of BMSCs to express markers of the osteoblast phenotype. These pH effects potentially relate to the microenvironment supplied by a tissue-engineering scaffold and suggest that degrading polymer scaffolds may influence the biologic activity of the cells in the immediate environment.
authors.affiliation: Department of Biologic and Materials Sciences, School of Dentistry, The University of Michigan, Ann Arbor, Michigan 48109-1078, USA.
authors.forename: David H
authors.initials: DH
authors.lastname: Kohn
authors.forename: Mojgan
authors.initials: M
authors.lastname: Sarmadi
authors.forename: Joseph I
authors.initials: JI
authors.lastname: Helman
authors.forename: Paul H
authors.initials: PH
authors.lastname: Krebsbach
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D015415:Biomarkers; D001709:Biotechnology; D015152:Blotting, Northern; D001854:Bone Marrow Cells / Q000502:physiology*; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D003470:Culture Media; D006801:Humans; D006863:Hydrogen-Ion Concentration; D051379:Mice; D008807:Mice, Inbred BALB C; D010006:Osteoblasts / Q000502:physiology; D015675:Osteocalcin / Q000096:biosynthesis / Q000235:genetics; D010641:Phenotype; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D017154:Stromal Cells / Q000502:physiology*
chemical_list: D015415:Biomarkers; D003470:Culture Media; D012333:RNA, Messenger; D015675:Osteocalcin; D003094:Collagen; D000469:Alkaline Phosphatase