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Role of fibroblasts in soft tissue biomechanics Yip, Clare

Abstract

The aim of this project was to investigate the contribution of fibroblasts on the mechanical properties of the dermal connective tissue in rat skin. The research studied the effect of soaking, strairiing and/or poison on the viability of the fibroblasts and the stress relaxation of skin tissue. These studies were carried out for skin soaked in a physiological solution (Kreb's solution) with and without addition of a metabolic poison, 2-Deoxy-D-Glucose. Thirty male rats were used in the study and four strips of two by five centimeters skin were removed from the back of each rat. Skin samples were either soaked in Kreb's solution in the presence or absence of poison, or simultaneously soaked and strained in Kreb's solution in the presence or absence of poison. All tissues were fixed and processed for apoptosis assay and light microscopy. The viability study showed that straining of tissues soaked in Kreb's solution significantly increases the number of apoptotic cells, and it causes more apoptotic cells compared to just soaking in Kreb's solution. Straining the skin tissues causes the extracellular matrix and cytoplasmic contacts of the fibroblasts to become disconnected and allow the tissues to relax moreeasily. However, straining of tissues soaked in Kreb's solution with 2-Deoxy-D-Glucose do not significantly increase the number of apoptotic cells. Thus, the morphological results did not support the hypothesis that 2-Deoxy-D-Glucose kills all of the fibroblasts by apoptosis; however, it may kill the fibroblasts by inducing necrosis. Mechanical testing (straining) involved stress-relaxation for thirty seconds at a fixed strain (13%). Samples strained in Kreb's solution are found to have higher reduction in stress (i.e. stress relaxation) with more apoptotic fibroblasts and less non-apoptotic fibroblasts compared to samples strained in Kreb's solution with 2-Deoxy-D-Glucose. The difference in stress relaxation between the two treatments was found to correlate with the number of non-apoptotic and apoptotic fibroblasts in the samples. A direct linear relationship was observed between the stress relaxation differences and the ratios of apoptotic cells for the two treatments. Samples stretched in Kreb's solution exhibited greater relaxation and had more apoptotic fibroblasts compared to those stretched in Poison. There is an inverse relationship observed between the stress relaxation differences and the ratios of non-apoptotic cells for the two treatments. Samples stretched in Kreb's solution exhibited greater relaxation, but had less apoptotic fibroblasts compared to those stretched in Poison.

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