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Physiological activities in vivo are regulated by a myriad of chemical, physical and mechanical cues that establish a milieu for tissues and the residing cells. Mimicking this milieu is important for the in vitro models incorporated in tissue engineering strategies. Mechanical cues role is significant in regulating the homeostasis of musculoskeletal tissues as well as the remodeling and regeneration of these tissues. In the case of compromised tissue functions, mechanical cues are utilized in vivo to recruit stem and progenitor cells to the injury site to initiate the tissue regeneration process and further to regulate a cascade of actions throughout this process. Mechanical loading platforms have been used to replicate the native tissue environments in vitro for various applications. Modulating stem cells fate toward a specific lineage and conditioning engineered extracellular matrix are one of the many application areas of mechanical loading platforms. Harnessing in vitro mechanical loading platforms with in silico models is found to be a successful approach to replicate the in vivo mechanical conditions and predict various cellular responses. Adipose-derived stem cells (ASCs) have become promising cell type for musculoskeletal tissues regeneration due to their pluripotency, ease of harvesting, and abundance compared to bone marrow-derived stem cells. The use of ASCs and mechanical loading of tissue-engineered constructs can contribute to the ongoing attempts to improve the musculoskeletal tissue engineering outcome. The objective of the current dissertation was twofold: 1) To create and characterize an equiaxial mechanical loading platform and to understand how applied equiaxial strain transferred in multiple scales to the 3D matrix and residing cells using in silico model 2) To investigate the role of equiaxial strain on modulating ASCs fate and 3D tissue-engineered matrix morphology. We combined an in vitro mechanical loading platform with in silico multi-length scale finite element modeling to introduce a strategy that can be utilized to repair annulus fibrosus defects. Our results demonstrated that EQUicycler is effective in applying equiaxial strain within the physiological range of musculoskeletal tissues. The application of equiaxial strain resulted in various positive effects in the matrix as well as the cells levels. Using computational in silico modeling and stochastic analyses, the micromechanical environment around the cells embedded in tissue-engineered constructs was studied. The effect of equiaxial strain on the cell viability was predicted. Based on the results obtained from the in vitro and in silico models, a repair strategy for degenerated annulus fibrosus tissue was presented. The strategy incorporated optimized loading modality to ASCs-encapsulated in biphasic scaffolds made of inner collagen layer and an outer composite layer of nanofibrous polycaprolactone embedded in collagen. The biphasic scaffolds conditioned by equiaxial strain demonstrated biomimetic biochemical and biomechanical features to the annulus fibrous tissue. In conclusion, we demonstrated that in vitro and in silico models can be harnessed together to develop repair strategies for a complex musculoskeletal tissue such as the annulus fibrosus. |
