Investigation of the Short-term Effects of Heat Shock on Human Hamstring Tenocytes In Vitro

Tendons and ligaments are collagenous connective tissues involved in locomotion and stabilization of joints. These tissues possess relatively low cellularity and vascularity, resulting in long and potentially incomplete healing responses following injury. For sub-failure injuries such as strains and sprains, the common treatment is an implementation of rest, ice, compression, and elevation. This procedure relies on the tissue’s natural healing ability, leaving the tissue prone to possible re-injury and failure. As a potential aid in the healing process, we investigated the effects of thermal stress on human tenocytes in vitro. This method exploits the activity of heat shock proteins, which assist in cellular proliferation and protein assembly. Heat shock at 40, 44, and 48 °C was applied to human hamstring tenocytes for 5–20 min. Studies were performed to determine metabolic activity, proliferation, protein secretion, and gene expression of the cells shortly after heating. A scratch wound healing assay was performed to monitor migration of cells as they recovered from heat shock. The data showed increased cellular activity following 15 and 20 min of thermal conditioning at 44 and 48 °C. Protein secretion and expression of collagens types I and III and TGF-β1 suggest that the heat shock response of tenocytes is similar to that of natural wound healing. The results revealed different responses for different temperatures and different durations of heat shock. The scratch assay revealed that heat might hasten recovery times following injury. Although additional studies that investigate additional heat shock proteins with different cell lines must be performed, these initial results suggest that heat shock may be a potential therapeutic tool that should be further investigated for the treatment of sub-failure tendon and ligament injuries. Heat shock presents a potential aid for the regeneration of damaged musculoskeletal tissues. In this preliminary study of human hamstring tenocytes in vitro, the application of thermal stress for a short duration caused rapid proliferation of cells after they were allowed to recover. Furthermore, parallels were observed between the in vitro heat shock response and the natural wound healing process of tendons and ligaments. This information provides potential for heat shock to assist in healing damage tendon and ligament tissue. Future works will need to explore the effects of heat shock on a wider range of tendon and ligament cells, as well as develop methods of applying thermal stress to tissue in vivo.