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Effects of transforming growth factor-beta and mechanical strain on osteoblast cell counts: an in vitro model for distraction osteogenesis. Plast Reconstr Surg 2000 Jan;105(1):130-6; discussion 137-9

Date

01/08/2000

Pubmed ID

10626981

DOI

10.1097/00006534-200001000-00022

Abstract

Factors known to regulate bone production during distraction osteogenesis include mechanical strain on bone forming cells and up-regulation of transforming growth factor-beta (TGF-beta) during the distraction, or strain phase of distraction osteogenesis. In the present study, an in vitro model was used to evaluate the functional effect of exogenous TGF-beta1 on mitogenesis in murine-derived MC3T3 osteoblasts during the period of active mechanical strain. The first hypothesis to be tested was that mitogenic suppression of MC3T3 osteoblasts by TGF-beta1 is further enhanced when these cells are also subjected to mechanical strain. To test this hypothesis, MC3T3 osteoblasts were seeded on flexible and rigid membranes. These were subjected to cyclic, vacuum-induced strain, simulating physiologic stress loads. After 24 hours, all cells were transferred to media containing TGF-beta1, and strain was continued for an additional 48 hours. The study was repeated by using two doses of TGF-beta1. This study demonstrated that final cell counts were significantly decreased in the presence of TGF-beta1 in both the nonstrained and strained groups (p < 0.0001). The final cell count in the strained group was significantly less than that in the nonstrained group (p < 0.0001) for both concentrations of TGF-beta1 tested, confirming the initial hypothesis. The second hypothesis to be tested was that alteration in the mitogenic response of MC3T3 osteoblasts after strain is not directly due to autocrine factors produced by the strained osteoblasts. To test this hypothesis, a proliferation assay was performed on nonconfluent MC3T3 osteoblasts by using conditioned media collected from strained and nonstrained osteoblasts. This study demonstrated no significant differences in cell counts after addition of conditioned media collected from strained versus nonstrained cells, confirming the latter hypothesis. The present study demonstrates the functional significance of mechanical strain on osteoblast cell counts. Furthermore, this may help to explain the temporal relationship observed during the early distraction (strain) phase of distraction osteogenesis in rodent models in which peak up-regulation of TGF-beta1 gene expression correlates with peak suppression of osteoblast function as measured by gene expression of extracellular matrix proteins.

Author List

Gosain AK, Song LS, Santoro T, Weihrauch D, Bosi BO, Corrao MA, Chilian WM

Author

Dorothee Weihrauch DVM, PhD Professor in the Anesthesiology department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Animals
Cell Count
Cell Division
Cell Line
Culture Media, Conditioned
Extracellular Matrix Proteins
In Vitro Techniques
Mice
Osteoblasts
Osteogenesis, Distraction
Stress, Mechanical
Transforming Growth Factor beta
Up-Regulation
jenkins-FCD Prod-410 e9586552fe7f53c71f7923aa6e27aeabbd3c2473