1. ¹Center for Molecular Orthopaedics, Harvard Medical School, Boston, MA 02115, USA
2. ²Department of Orthopaedics, Case Western Reserve University, Cleveland, OH 44106, USA

Correspondence: Steven C. Ghivizzani, Department of Orthopaedics and Rehabilitation, University of Florida, P.O. Box 100137, JHMHC, 1600 SW Archer Road, Gainesville, FL 32610–0137, USA. Fax: +1 352 273 7247. E-mail: ghivisc@otho.ufl.edu

Received 23 July 2004; Accepted 11 March 2005.

Abstract

Adult mesenchymal stem cells (MSCs) have the capacity to differentiate into various connective tissues such as cartilage and bone following stimulation with certain growth factors. However, less is known about the capacity of these cells to undergo chondrogenesis when these proteins are delivered via gene transfer. In this study, we investigated chondrogenesis of primary, bone marrow-derived MSCs in aggregate cultures following genetic modification with adenoviral vectors encoding chondrogenic growth factors. We found that adenoviral-mediated expression of TGF-1 and BMP-2, but not IGF-1, induced chondrogenesis of MSCs as evidenced by toluidine blue metachromasia and immunohistochemical detection of type II collagen. Chondrogenesis correlated with the level and duration of expressed protein and was strongest in aggregates expressing 10–100 ng/ml transgene product. Transgene expression in all aggregates was highly transient, showing a marked decrease after 7 days. Chondrogenesis was inhibited in aggregates modified to express >100 ng/ml TGF-1 or BMP-2; however, this was found to be partly due to the inhibitory effect of exposure to high adenoviral loads. Our findings indicate that parameters such as these are important functional considerations for adapting gene transfer technologies to induce chondrogenesis of MSCs.