PHOTOBIOMODULATION AND STEM CELL DIFFERENTIATION: APPLICATION TO MODULATE ADIPOGENESIS THROUGH CELLULAR AND NUCLEAR MORPHOLOGY

Abstract

Mesenchymal stem cells (MSCs) are of great interest in regenerative medicine due to their capability to self-renew and differentiate to various lineages. Typically, differentiation to specific cell types has relied on the use of growth factors and other reagents to provide an environment conducive to the desired cell type. More recently, orthogonal cues other than chemical factors have been elucidated to regulate the lineage commitment. For example, the cell shape, cellular mechanics and substrate stiffness have been found to play a role in determining the fate of MSCs. However, it remains still elusive how the morphological and mechanical changes in the nucleus are involved in directing MSCs to the intended lineage. Using immunolabeling and computer-assisted image analysis, the first aim is designed to elucidate changes in the nucleus during differentiation to the fat-storing adipocytes. Recent studies suggest that low level light exposure can serve as yet another nonbiological factor that can modulate the MSC differentiation. Referred to as photobiomodulation (PBM), it describes the influence of light irradiation on biological tissues and has been shown to affect a variety of cells. Laser light in the near infrared spectrum (NIR, 780 – 2500 nm) in particular has been shown to directly affect heme-containing proteins, changing their level of activity. NIR light has been used in the medical field for analyses of cerebral blood flow. Recently, new evidence suggest light exposure can alter stem cell differentiation, potentially by interacting directly with the heme-containing protein of oxidative phosphorylation, cytochrome C. The second aim of the thesis is to apply NIR light exposure (1064 nm) to the cells undergoing adipogenic differentiation and determine the effect of PBM on differentiated adipocytes. Obesity, often caused by enlarged hypertrophic adipocytes, carries a multitude of physiological risks including diabetes and heart disease. Interestingly, clinical trials of photobiomodulation on obese participants has shown significant weight loss, suggesting PBM may hinder lipid accumulation and regulate adipocyte maturation. However, such a hypothesis remains to be validated, and the potential mechanisms need be understood. In addition, to establish possible clinical efficacy, the effects of PBM must be quantitatively determined in an in vitro obesity model. The third aim is to characterize the model and apply NIR exposure (1064 nm) to examine a reduction in the lipid accumulation and conformational and functional restoration of hypertrophic adipocytes.