Osteoblast response to fluid induced shear depends on substrate microarchitecture and varies with time

Z. Schwartz, T. A. Denison, S. R. Bannister, D. L. Cochran, Y. H. Liu, C. H. Lohmann, M. Wieland, B. D. Boyan

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

Osteoblasts are exposed to fluid shear in vivo but the effects are not well understood, particularly how substrate properties or length of exposure modify the response. Short exposure (1 h) to shear reduces the stimulatory effect of micron-scale surface structure on osteoblast differentiation, but the effects of longer term exposures are not known. To test the hypothesis that substrate-dependent responses of osteoblasts to shear depend on the length of exposure to fluid flow, MG63 osteoblasts were grown on tissue culture glass, which has an average roughness (Ra) < 0.2 μm; machined Ti disks (PT, Ra < 0.6 μm); Ti disks with a complex microarchitecture [sand blasted acid etched (SLA), Ra = 4-5 μm); and Ti plasma-sprayed surfaces [Ti via plasma spray (TPS), Ra = 7 μm]. Confluent cultures were exposed to pulsatile flow at shear forces of 0, 1, and 14 dynes/cm2 for 0, 6, 12, and 24 h. Shear reduced cell number on all surfaces, with greatest effects on TPS. Shear had no effect on alkaline phosphatase on smooth surfaces but increased enzyme activity on SLA and TPS in a time-dependent manner. Its effects on osteocalcin, TGF-β1, and PGE2 in the conditioned media were greatest on these surfaces as well. Responses to fluid-induced shear were blocked by the general Cox inhibitor indomethacin and the Cox-2 inhibitor meloxicam, indicating that response to shear is mediated by prostaglandin produced via a Cox-2 dependent mechanism. These results show that the effects of fluid induced shear change with time and are substrate dependent, suggesting that substrate microarchitecture regulates the osteoblast phenotype and effects of shear are determined by the maturation state of the responding population.

Original languageEnglish (US)
Pages (from-to)20-32
Number of pages13
JournalJournal of Biomedical Materials Research - Part A
Volume83
Issue number1
DOIs
StatePublished - Oct 2007

Keywords

  • Fluid shear
  • Osteoblast
  • Substrate microstructure
  • Titanium

ASJC Scopus subject areas

  • Ceramics and Composites
  • Biomaterials
  • Biomedical Engineering
  • Metals and Alloys

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