Effects of Mild Heating on the Osteogenic Differentiation of Human Mesenchymal Stem Cells during Inflammation
"Current surgical procedures to treat osteoarthritis have varying degrees of success, but carry inherent risks and a finite life expectancy. A more permanent solution is a treatment that regenerates biologically viable tissue that integrates with the patient and retains functionality. For maximal effectiveness, such a treatment should also repair bone loss known to occur in osteoarthritis and attenuate chronic inflammation that can obstruct healing. Mesenchymal stem cells have great potential to be used as part of a novel therapy for bone and cartilage regeneration. They are a highly regulated, self-renewing population of cells with potent mechanisms to avoid allogeneic rejection, offering significant potential for the generation of tissue that can replace damaged areas in the body with minimal risk of side effects. In order to realize this potential, it is important to take advantage of the mechanisms that induce stem cell differentiation into desired tissues or structures, and enhance the qualitative extent of stem cell proliferation and differentiation, all while mitigating the effects of inflammation. Studies have shown that temperature is strongly correlated with reparative processes in tissue. Mild heat shock has been shown to induce proliferation and differentiation of osteoprogenitor cells in vitro. The central hypothesis of our study is that mild heat shock may facilitate the bone and cartilage regeneration from MSCs under inflammatory conditions of osteoarthritis. In this study we focus on the osteocentric model of osteoarthritis and investigate the direct effects of mild heat shock on the osteogenic differentiation of hMSCs while simulating inflammation. Human MSCs isolated from bone marrow were seeded in 2D culture plates and incubated for 1 hour at 39Â°C once per week during osteogenic differentiation. Alkaline phosphatase activity was downregulated by periodic heating at Day 6 of ii differentiation. Heat shock had little effect on calcium deposition at Day 19, but it did have a cytokine-dependent effect at Day 28 â€“ increasing calcium deposition in MSC cultures with IL-6 and decreasing calcium deposition in MSC cultures with TNF-Î±. Periodic heat shock also induced proliferation of MSCs at Day 6 and mitigated TNF-Î±-induced apoptosis. These results demonstrate that mild hyperthermia may potentially be used to facilitate bone regeneration in osteoarthritis using hMSCs, and therefore may influence the design of heat-based therapies to be used in vivo."