A Spectrophotometric Analysis of Human Osteoarthritic Cartilage Explants Subjected to Specific Capacitively Coupled Electric Fields

Abstract

We have previously shown that capacitively coupled electrical stimulation of either normal bovine articular chondrocytes or osteoarthritic human articular cartilage explants resulted in up-regulation of cartilage matrix gene expression and down-regulation of metalloproteinase gene expression. In addition, collagen and proteoglycan protein levels were also elevated. To determine visually the effect of specific electric fields on modifying cartilage structure, freshly harvested human full-thickness osteoarthritic cartilage explants were stimulated in the absence or presence of interleukin-1β, an inflammatory cytokine, and were examined photographically and spectrophotometrically. Hexosamine and hydroxyproline contents were also determined. Spectrophotometric analysis was used to quantify any changes in the depth of defects in the cartilage ranging from surface level (red-colored) to the deepest affected layer (blue-colored). Interleukin-1β treatment alone caused significant additional cartilage erosion. Electrical stimulation alone resulted in significant decreases in the cartilage defects. Electrical stimulation in the presence of interleukin-1β resulted in a small, but significant, surface improvement. Meta-analysis also confirmed a significant increase in the hexosamine and hydroxyproline contents (indicating matrix deposition). It was concluded that an appropriate electric field could modify osteoarthritic lesions in full-thickness cartilage plugs by increasing matrix production and/or by decreasing matrix destruction. Furthermore, it appears that spectrophotometric analysis is a relatively easy method for quantifying the “filling in” or healing of articular cartilage defects.