9616738 Roberts Articular cartilage lesions often heal slowly and incompletely due to the poor ability of this tissue to proliferate following injury. Controlled upregulation of chondrocyte metabolism and matrix synthesis may potentially enhance the healing outcome. Single Nd:YAG laser (1064 nm) treatments of in vitro bovine and canine articular cartilage explants have been reported to produce significant increases in the matrix content of glycosaminoglycans (GAG), proteoglycans (PG), collagen, and noncollagen protein 3-7 days post-irradiation. Use of the 1064 nm wavelength for this purpose is non-ideal, however, due to the low photon energy and poor absorption characteristics of this wavelength in articular cartilage. Furthermore, the YAG laser is expensive, non- portable, and requires complicated water cooling during operation. The purpose of this proposal is to determine if equine articular cartilage matrix synthesis can be nonthermally modulated in vitro via irradiation with a helium neon (HeNe, 633 nm) laser, a diode laser (810 nm), or a broadband light source. It is hypothesized that 633 and 810 nm laser irradiation will be successful in modulating cartilage metabolism due to the higher photon energy, more favorable absorption characteristics, and reported success in other low energy laser applications using these wavelengths. In Phase 1 of this proposal, PG synthesis will be assayed in cartilage explants following irradiation under a variety of light delivery protocols in order to determine the effective range of parameters necessary to consistently upregulate PG matrix synthesis with these light sources. In Phase 2, irradiation- induced temperature increases in cartilage explants as a function of energy delivery protocol, depth in the explant, and light source will be recorded. Data from Phases 1 and 2 will be used to select appropriate light delivery protocols for Phase 3 experiments and verify the nonthermal nature of the light inte raction with the tissue. In Phase 3, cultured equine articular cartilage explants will be irradiated with one of the three light sources using energy delivery protocols found to be effective in Phase 1. Light-induced changes in matrix PG, GAG, total protein, and cell viability will be compared to non- irradiated control explants. It is anticipated that this interdisciplinary project will develop the preliminary data required for a full NSF funding proposal. Future work will extend this investigation into in vitro human tissue or in vivo animal experiments and investigate the mechanism of action of light in articular cartilage. Ultimately, clinical treatments may be possible in which an appropriate dose of light is delivered to cartilage lesions through arthroscopy or used to enhance cell growth in culture for autologous chondrocyte implantation. ***
