Characterization of vasculogenic potential of human adipose-derived endothelial cells in a three-dimensional vascularized skin substitute.

PURPOSE: The need for clinically applicable skin substitutes continues to be a matter of fact. Hypothetically, a laboratory grown autologous skin analog with near normal architecture might be a suitable approach to yield both satisfactory functional and cosmetic long-term results. In this study, we explored the use of human endothelial cells derived from freshly isolated adipose stromal vascular fraction (SVF) in a three-dimensional (3D) co-culture model of vascularized bio-engineered skin substitute. METHODS: The SVF was isolated from human white adipose tissue samples and keratinocytes from human skin biopsies. The SVF, in particular endothelial cells, were characterized using flow cytometry and immuofluorescence analysis. Endothelial and mesenchymal progenitors from the SVF formed blood capillaries after seeding into a 3D collagen type I hydrogel in vitro. Subsequently, human keratinocytes were seeded on the top of those hydrogels to develop a vascularized dermo-epidermal skin substitute. RESULTS: Flow cytometric analysis of surface markers of the freshly isolated SVF showed the expression of endothelial markers (CD31, CD34, CD146), mesenchymal/stromal cell-associated markers (CD44, CD73, CD90, CD105), stem cell markers (CD49f, CD117, CD133), and additionally hematopoietic markers (CD14, CD15, CD45). Further analysis of white adipose-derived endothelial cells (watECs) revealed the co-expression of CD31, CD34, CD90, CD105, and partially CD146 on these cells. WatECs were separated from adipose-stromal cells (watASCs) using FACS sorting. WatASCs and watECs cultured separately in a 3D hydrogel for 3 weeks did not form any vascular structures. Only if co-cultured, both cell types aligned to develop a ramified vascular network in vitro with continuous endothelial lumen formation. Transplantation of those 3D-hydrogels onto immuno-incompetent rats resulted in a rapid connection of human capillaries with the host vessels and formation of functional, blood-perfused mosaic human-rat vessels within only 3-4 days. CONCLUSIONS: Adipose tissue represents an attractive cell source due to the ease of isolation and abundance of endothelial as well as mesenchymal cell lineages. Adipose-derived SVF cells exhibit the ability to form microvascular structures in vitro and support the accelerated blood perfusion in skin substitutes in vivo when transplanted.

Towards artificial tissue models: past, present, and future of 3D bioprinting.

Regenerative medicine and tissue engineering have seen unprecedented growth in the past decade, driving the field of artificial tissue models towards a revolution in future medicine. Major progress has been achieved through the development of innovative biomanufacturing strategies to pattern and assemble cells and extracellular matrix (ECM) in three-dimensions (3D) to create functional tissue constructs. Bioprinting has emerged as a promising 3D biomanufacturing technology, enabling precise control over spatial and temporal distribution of cells and ECM. Bioprinting technology can be used to engineer artificial tissues and organs by producing scaffolds with controlled spatial heterogeneity of physical properties, cellular composition, and ECM organization. This innovative approach is increasingly utilized in biomedicine, and has potential to create artificial functional constructs for drug screening and toxicology research, as well as tissue and organ transplantation. Herein, we review the recent advances in bioprinting technologies and discuss current markets, approaches, and biomedical applications. We also present current challenges and provide future directions for bioprinting research.

Magnetic Levitational Assembly for Living Material Fabrication.

Functional living materials with microscale compositional topographies are prevalent in nature. However, the creation of biomaterials composed of living micro building blocks, each programmed by composition, functionality, and shape, is still a challenge. A powerful yet simple approach to create living materials using a levitation-based magnetic method is presented.

Microscale assembly directed by liquid-based template.

A liquid surface established by standing waves is used as a dynamically reconfigurable template to assemble microscale materials into ordered, symmetric structures in a scalable and parallel manner. The broad applicability of this technology is illustrated by assembling diverse materials from soft matter, rigid bodies, individual cells, cell spheroids and cell-seeded microcarrier beads.