Engineering of a complex bone tissue model with endothelialised channels and capillary-like networks

Abstract

In engineering of tissue analogues, upscaling to clinically-relevant sized constructs remains a significant challenge. The successful integration of a vascular network throughout the engineered tissue is anticipated to overcome the lack of nutrient and oxygen supply to residing cells. This work aimed at developing a multiscale bone-tissue-specific vascularisation strategy. Engineering pre-vascularised bone leads to biological and fabrication dilemmas. To fabricate channels endowed with an endothelium and suitable for osteogenesis, rather stiff materials are preferable, while capillarisation requires soft matrices. To overcome this challenge, gelatine-methacryloyl hydrogels were tailored by changing the degree of functionalisation to allow for cell spreading within the hydrogel, while still enabling endothelialisation on the hydrogel surface. An additional challenge was the combination of the multiple required cell-types within one biomaterial, sharing the same culture medium. Consequently, a new medium composition was investigated that simultaneously allowed for endothelialisation, capillarisation and osteogenesis. Integrated multipotent mesenchymal stromal cells, which give rise to pericyte-like and osteogenic cells, and endothelial-colony-forming cells (ECFCs) which form capillaries and endothelium, were used. Based on the aforementioned optimisation, a construct of 8 × 8 × 3 mm, with a central channel of 600 µm in diameter, was engineered. In this construct, ECFCs covered the channel with endothelium and osteogenic cells resided in the hydrogel, adjacent to self-assembled capillary-like networks. This study showed the promise of engineering complex tissue constructs by means of human primary cells, paving the way for scaling-up and finally overcoming the challenge of engineering vascularised tissues.

Inspired by the human placenta: a novel 3D bioprinted membrane system to create barrier models

“…Gelatine is a commonly used ECM component in cell culture and its derivative GelMA is well characterized and widely used in 3D bioprinting, which Yue et al reviewed comprehensively 36 . Many cell types of different tissue origin have been cultured successfully on GelMA: endothelial (HUVEC 37,38 , ECFC 39 ) and epithelial cells (Ishikawa 40 , BeWo 41 ) as well as cells of mesenchymal origin (NIH-3T3 42 , MG63, osteoblasts 43 ).…”

Osteogenic and angiogenic tissue formation in high fidelity nanocomposite Laponite-gelatin bioinks

“…While the significant modification of physical properties allowed printing of complex structures, whether the increased stiffness influenced stem cell differentiation and tissue formation was not examined. It has been shown that the osteogenic differentiation of HBMSCs within 3D matrices occurs preferentially in substrates from 10 to 30 kPa [47], while vascularisation of tissue engineered constructs is favoured in softer matrices below 5 kPa [48]. Furthermore, culture media and additional cell-signaling cues can produce a synergistic effect on cell function and differentiation [48,49].…”

“…It has been shown that the osteogenic differentiation of HBMSCs within 3D matrices occurs preferentially in substrates from 10 to 30 kPa [47], while vascularisation of tissue engineered constructs is favoured in softer matrices below 5 kPa [48]. Furthermore, culture media and additional cell-signaling cues can produce a synergistic effect on cell function and differentiation [48,49]. In the bioink system reported herein, the addition of LPN resulted in unchanged mechanical strength of GelMA (8 kPa) while maintaining significantly enhanced printability.…”

From Shape to Function: The Next Step in Bioprinting

“…[ 271 ] Additionally, incorporation of tubular networks in bioprinted tissues is highly relevant for a wide array of applications, as many tissues present microtubular structures (kidney, bile ducts, milk ducts, among others). Commonly used bioinks, including gelatin-, collagen- and fibrin-derived, have been optimized to support both vascular cells and tissue-specific cells, [ 272 , 273 ] taking advantage of the spontaneous ability of endothelial cells to reorganize themselves into capillary networks, when embedded in soft, cell adhesive hydrogels. Aiming for vascularized bone engineering a vasculogenesis-supportive bioink, based on gelatin/alginate blends and HUVECs was reinforced via coprinting with a PCL-based reinforcing frame.…”