Presented in part in the 2001 Elizabeth Winston-Lanier Kappa Delta Award presentation (MS) at the American Academy of Orthopaedic Surgeons/Orthopaedic Research Society Meeting.
Expression of smooth muscle actin in osteoblasts in human bone†
Article first published online: 1 JAN 2006
Copyright © 2002 Orthopaedic Research Society
Journal of Orthopaedic Research
Volume 20, Issue 3, pages 622–632, May 2002
How to Cite
Kinner, B. and Spector, M. (2002), Expression of smooth muscle actin in osteoblasts in human bone. J. Orthop. Res., 20: 622–632. doi: 10.1016/S0736-0266(01)00145-0
- Issue published online: 1 JAN 2006
- Article first published online: 1 JAN 2006
- Manuscript Accepted: 17 SEP 2001
- Manuscript Received: 15 JUN 2001
- Robert Bosch Foundation (BK)
- Brigham Orthopaedic Foundation
- Smooth muscle actin;
It is well known that certain connective tissue cells (viz., dermal fibroblasts) can express the gene for a muscle actin – α-smooth muscle actin – and can contract. This process contributes to skin wound closure and is responsible for Dupuytren's contracture. The objective of this study was to determine if human osteoblasts can also express the gene for α-smooth muscle actin. Immunohistochemistry using a monoclonal antibody for α-smooth muscle actin was performed on human cancellous bone samples obtained from 20 individuals at the time of total joint arthroplasty. The percentages of resting and active osteoblasts on the bone surfaces containing this muscle actin isoform were evaluated. Explants of human bone were also studied for the expression of α-smooth muscle actin in the tissue and in the outgrowing cells with time in culture. Western blot analysis was performed to quantify the α-smooth muscle actin content of the outgrowing cells relative to smooth muscle cell controls.
Nine ± 2% (mean ± SEM; n = 20) of the cells classified as inactive osteoblasts and 69 ± 3% (n = 19) of the cells identified as active osteoblasts on the bone surface contained α-smooth muscle actin. This difference was highly statistically significant (Student's t test, p < 0.0001). Similar profiles of α-smooth muscle actin-expressing cells were found in explants cultured for up to 12 weeks. Cells forming a layer on the surface of the explants and growing out from them in monolayer also contained α-smooth muscle actin by immunohistochemistry and Western blot analysis.
Human osteoblasts can express the gene for α-smooth muscle actin. This expression should be considered a phenotypic characteristic of this cell type, conferred by its progenitor cells: bone marrow stromal-derived stem cells, and perhaps pericytes and smooth muscle cells. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.