Abstract
Collagen IV is the major matrix component associated with differentiating adipocytes in adipose tissues, and the understanding of its contribution in adipogenic differentiation could be important for elucidation of mechanisms and processes driving the obesity. Therefore, in the light of our previous findings of differential effects of structural conformation of collagen I matrix on differentiation of bone marrow stromal cells, we investigated whether similar phenomenon occurs on collagen IV matrix in native and denatured structural states. The results of the present study show that native collagen IV is unsupportive of adipogenic differentiation and very little if any adipogenesis occurs on this matrix in the presence of adipogenic stimuli. In sharp contrast to native collagen IV, the same matrix in denatured structural state drives highly efficient adipogenic differentiation suggesting that it might be the major driver of adipogenesis in adipose tissues and that the ratio of native to denatured matrix might regulate the intensity of adipogenesis and possibly underlies the obesity. In contrast to observations that adipogenesis on denatured collagen I (collagen I is the major matrix component in musculoskeletal tissues) is suppressed by stress, adipogenesis on denatured collagen IV appears to be stress-resistant suggesting an explanation for the observed ineffectiveness of physical exercise, i.e. mechanical stress, in the reduction of adipose tissues. The obesity was shown to be associated with overproduction of MMPs and decline in levels of TIMPs. Such a shift in MMP/TIMP balance was considered a consequence of the pathology. In the light of the present study, however, this shift might constitute the primary source of the decease. The findings of the present study suggest strategies for the treatment of obesity, raise significant questions and indicate directions for further experimentation.