Development of Cell-only Vascular Tissue Models Using 3D Bioprinting

Figueroa Milla, Andre

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Development of Cell-only Vascular Tissue Models Using 3D Bioprinting

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Coronary artery disease is the leading cause of death in the United States, accounting for around 610,000 deaths per year. The development of new drugs to treat coronary artery disease has been limited due to ineffective pre-clinical models, which are used as to predict the success of novel therapeutics in humans. Current pre-clinical models include two-dimensional (2D) cell culture, which does not capture the complex physiology or pathophysiology of human tissues. Animal models offer complex systemic responses but have innate genetic and physiological differences from humans. These limitations lead to less than 14% of drugs succeeding in clinical trials despite yielding promising results in pre-clinical studies. Three-dimensional (3D) engineered tissue models are an alternative to standard pre-clinical models as they can recapitulate native human tissue anatomy, physiology, and pathology. Current functional engineered tissue models of blood vessels have yet to achieve spatial eccentricity, resulting in constructs that fail to capture the complex anatomy of vascular diseases. For example, atherosclerosis, a pathological precursor of coronary artery disease, initiates in a specific region of the vessel, and can progressively occlude the artery. Thus, there is a need to create a human-relevant functional blood vessel model with localized eccentric regions. The work presented in this dissertation describes the first cell-only 3D bioprinted self-assembled engineered vasculature tissue featuring eccentric regions that does not rely on pre-aggregated cellular units. To achieve this, engineered tissues were created from rat aortic smooth muscle cells (SMC) which were bioprinted into an oxidized and methacrylated alginate (OMA) microgel bath and aggregated in a single step. The self-aggregated constructs secrete their own extracellular matrix (ECM), allowing cell-cell interactions and tissue remodeling. We demonstrated the advantages of dispensing cells with reduced-diameter tips (159 μm) in terms of minimizing cell damage, enhancing tissue morphology, and improving tissue mechanical properties. Subsequently, we developed a workflow for creating high-fidelity constructs containing distinct localized regions with multiple bioinks. Furthermore, we enhanced the functionality of these models by utilizing human cells, specifically investigating the differentiation of human mesenchymal stem cells (hMSCs) into human SMCs through contractile protein expression and contraction studies. Finally, we incorporated eccentric regions of macrophage-like THP-1 cells and hMSCs within an hMSC tissue, to recapitulate the cell populations found in the onset of vascular disease.

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