3D Bioprinting of Vascularized Human Tissues

Abstract

The ability to manufacture human tissues that replicate the spatial, mechano-chemical, and temporal aspects of biological tissues would enable myriad applications, including drug screening, disease modeling, and tissue repair and regeneration. However, given the complexity of human tissues, this is a daunting challenge. Current biofabrication methods are unable to fully recapitulate the form and function of human tissues, which are composed of multiple cell types, extracellular matrices, and pervasive vasculature. My Ph.D. thesis focuses on advancing the capabilities of human tissue fabrication. Specifically, we demonstrate a multimaterial bioprinting method capable of producing 1D, 2D, and 3D vascularized tissue constructs by co-printing ECM, cell-laden, and fugitive inks. After these heterogeneous tissue constructs are printed and infilled with ECM, they are cooled to 4˚C to remove the fugitive ink leaving behind a pervasive network that is subsequently lined with endothelial cells. These constructs are ~ 1 mm in thickness and can be sustained for up to 14 days via rocking-based flow through their vasculature. We then created a new extracellular matrix that enabled the fabrication of tissues that exceed 1 cm in thickness that are perfused on a microfluidic chip for long time periods (> 6 weeks). To demonstrate functionality, growth factors are perfused via the vasculature to differentiate stem cells toward an osteogenic lineage in situ. Finally, we created renal proximal tubules (a sub-unit of kidney tissue) by this approach. Specifically, we constructed 3D tubules circumscribed by renal proximal tubule epithelial cells (PTECs). The PTECs form confluent, leak-tight epithelial monolayers that exhibit primary cilia and expresses Na+/K+ ATPase, Aquaporin 1, and K-cadherin. The combination of 3D geometry and on-chip perfusable nature gives rise to enhanced, polarized PTEC phenotypes that develop an enhanced brush border, basement membrane protein deposition, basolateral interdigitations, enhanced cell height, megalin expression, and albumin uptake relative to 2D controls. In summary, this multimaterial 3D bioprinting platform enables production of engineered human tissue constructs in which multiple cell types and vasculature are programmably placed within extracellular matrices. These 3D tissues may find potential applications in drug screening, disease models, and ultimately, tissue engineering and regenerative medicine.