Narrow Results

Chondrocytes in the growth plate undergo a relatively linear differentiation process. The progression of a chondrocyte from the proliferative stage to the hypertrophic stage is governed by complex interactions with the extracellular matrix within which it resides. A network of peptides, ion channels, and second messengers affects the transcription of certain genes that are ultimately translated into peptides which control cellular activity. Much effort has been invested into replicating this environment under in vitro conditions. It has been found that the three-dimensional (3D) cell culture is a more accurate representation of the in vivo environment in comparison to the traditional monolayer culture. It has also been found that a variety of stimuli may be used to induce the proliferation and differentiation of chondrocytes; one such stimulus is the mechanical stimulation of chondrocytes embedded in a 3D Gelfoam sponge. Chondrocytes are obtained from the chicken sternum. After the cells are cultured and cyclically loaded, mRNA levels of various mechanosensitive genes are quantified by real-time reverse transcription-polymerase chain reaction (RT-PCR). Mechanical stimulation has been shown to upregulate the expression of type X collagen mRNA in early hypertrophic chondrocytes. The entire process, beginning with the obtainment of chondrocytes and ending with the quantification and interpretation of gene expression, is detailed in the following chapter.