1999 Summer Research Faculty-Student Team

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Dr. Ellis Bell and Laura Owen

Ellis Bell is a professor in the Department of Chemistry at Gustavus Adolphus College.
Laura Owen is a sophomore at Gustavus majoing in Chemistry and minoring in Physics and Biochemistry.

The Effects of Bio-Active Glass on Rabbit Chondrocyte Development

Ellis Bell & Laura Owen
Gustavus Adolphus College

Jack Lewis and Ted Oegema
Orthopaedic Surgery, University of Minnesota

Arising from the need produced by injury and arthritis, there is much interest in the in vitro creation of soft/hard tissue interfaces. Since bioactive glass has been shown to affect the differentiation of a variety of cell types, our project involved examining the effects of a bioactive glass on chondrocyte development. Cartilaginous tissues make a number of types of interactions with hard tissues such as bone, and can in addition be mineralized. The overall goals of this project were to assess whether bioactive glass beads had an effect on chondrocyte differentiation and whether or not contact with beads led to a tendency toward mineralization of either the beads or the tissue matrix. Initial experiments established that culture of rabbit chondrocytes with beads led to increased expression of alkaline phosphatase [a marker for mineralizing tissue] as assessed by cytostaining using an alkaline phosphatase specific stain. Biochemical analysis showed that at certain times [1-2 weeks] alkaline phosphatase activity was enhanced in cell lysates. Control experiments using silicates in the absence of beads indicated that contact with beads [rather than release of silicate from he beads] was necessary for this effect. Similar effects were observed with cow chondrocytes but the time scale for observed elevation of alkaline phosphatase was longer.

Scanning electron microscope analysis of long term cultures [6 weeks] of chondrocytes, with bioactive glass beads added after two weeks suggested that the presence of the beads led to increased mineralization of the collagen matrix produced by the cells. Analysis of the beads [with and without prior removal of the organic matrix] by x ray analysis indicated that the organic matrix was the location of precipitated apatite crystals at short incubation times [2 week exposure to bioactive glass] but that with longer exposure apatite was deposited onto the glass as well as in the matrix. These results indicate that addition of bioactive glass to differentiating chondrocytes has an impact both on their differentiation and upon subsequent mineralization of the developing tissue.