Computational fluid dynamic analysis of bioprinted self-supporting perfused tissue models

Natural tissues are incorporated with vasculature, which is further integrated with a cardiovascular system responsible for driving perfusion of nutrient‐rich oxygenated blood through the vasculature to support cell metabolism within most cell‐dense tissues. Since scaffold‐free biofabricated tissues being developed into clinical implants, research models, and pharmaceutical testing platforms should similarly exhibit perfused tissue‐like structures, we generated a generalizable biofabrication method resulting in self‐supporting perfused (SSuPer) tissue constructs incorporated with perfusible microchannels and integrated with the modular FABRICA perfusion bioreactor. As proof of concept, we perfused an MLO‐A5 osteoblast‐based SSuPer tissue in the FABRICA. Although our resulting SSuPer tissue replicated vascularization and perfusion observed in situ, supported its own weight, and stained positively for mineral using Von Kossa staining, our in vitro results indicated that computational fluid dynamics (CFD) should be used to drive future construct design and flow application before further tissue biofabrication and perfusion. We built a CFD model of the SSuPer tissue integrated in the FABRICA and analyzed flow characteristics (net force, pressure distribution, shear stress, and oxygen distribution) through five SSuPer tissue microchannel patterns in two flow directions and at increasing flow rates. Important flow parameters include flow direction, fully developed flow, and tissue microchannel diameters matched and aligned with bioreactor flow channels. We observed that the SSuPer tissue platform is capable of providing direct perfusion to tissue constructs and proper culture conditions (oxygenation, with controllable shear and flow rates), indicating that our approach can be used to biofabricate tissue representing primary tissues and that we can model the system in silico

A practical analysis of adipose stromal cell functional differentiation response to multiple microenvironmental stimuli

The cellular microenvironment composed in the extracellular matrix is immediately responsible for influencing cellular activities such as differentiation, morphology, migration, ECM synthesis, apoptosis, and cell proliferation. Microenvironmental modes that influence cell activity include: soluble stimuli such as β-glycerol phosphate, ascorbic acid, and fibroblast growth factor which can influence osteogenesis, ECM synthesis, and proliferation; ECM protein stimuli exemplified by collagen, fibronectin, and laminin existent on the ECM surface; as well as the scale and topographical morphology of stimuli on the ECM surface. Adipose stromal cells are multipotent stem cells showing significant differential capacity in response to microenvironmental stimuli while exhibiting practical attributes that surpass bone marrow stromal cells and embryonic stem cells. The advantages posed by adipose derived stem cells make them better candidates for research and clinical applications regarding cell based regenerative tissue engineering. In this dissertation, the singular and combined influences of soluble, protein, and topographical stimuli on the functional differentiation of ASCs seeded onto a three dimensional poly(lactic-co-glycolic acid) construct were compared, characterized and then evaluated for their utility in real world clinical regenerative tissue engineering applications. Functional differentiation in this dissertation is described as ECM synthesis by seeded cells and cell number, which are proxies of de novo tissue generation integral to tissue regeneration. The data indicate synergistic interaction a of nanoscale surface topography with other stimuli modulate ASC response to soluble and protein stimuli which results in ECM synthesis, cell numbers, and ECM synthesis outputs per cell that are distinct from ASC response to singularly applied stimuli. In some cases, the amount of ECM present per the cell number matches cell-ECM ratios existent in natural tissue profiles, indicating that modulating ASCs response to tissue constructs containing combinations of soluble, protein, and nanotopographical stimuli may be useful in the development of engineered tissue regenerative therapies

Computational fluid dynamic analysis of bioprinted self-supporting perfused tissue models

Natural tissues are incorporated with vasculature, which is further integrated with a cardiovascular system responsible for driving perfusion of nutrient‐rich oxygenated blood through the vasculature to support cell metabolism within most cell‐dense tissues. Since scaffold‐free biofabricated tissues being developed into clinical implants, research models, and pharmaceutical testing platforms should similarly exhibit perfused tissue‐like structures, we generated a generalizable biofabrication method resulting in self‐supporting perfused (SSuPer) tissue constructs incorporated with perfusible microchannels and integrated with the modular FABRICA perfusion bioreactor. As proof of concept, we perfused an MLO‐A5 osteoblast‐based SSuPer tissue in the FABRICA. Although our resulting SSuPer tissue replicated vascularization and perfusion observed in situ, supported its own weight, and stained positively for mineral using Von Kossa staining, our in vitro results indicated that computational fluid dynamics (CFD) should be used to drive future construct design and flow application before further tissue biofabrication and perfusion. We built a CFD model of the SSuPer tissue integrated in the FABRICA and analyzed flow characteristics (net force, pressure distribution, shear stress, and oxygen distribution) through five SSuPer tissue microchannel patterns in two flow directions and at increasing flow rates. Important flow parameters include flow direction, fully developed flow, and tissue microchannel diameters matched and aligned with bioreactor flow channels. We observed that the SSuPer tissue platform is capable of providing direct perfusion to tissue constructs and proper culture conditions (oxygenation, with controllable shear and flow rates), indicating that our approach can be used to biofabricate tissue representing primary tissues and that we can model the system in silico