Biomaterial Scaffolds Made of Chemically Cross‐Linked Gelatin Microsphere Aggregates (C‐GMSs) Promote Vascularized Bone Regeneration

Abstract

Various scaffolding systems have been attempted to facilitate vascularization in tissue engineering by optimizing biophysical properties (e.g., vascular-like structures, porous architectures, surface topographies) or loading biochemical factors (e.g., growth factors, hormones). However, vascularization during ossification remains an unmet challenge that hampers the repair of large bone defects. In this study, reconstructing vascularized bones in situ against critical-sized bone defects is endeavored using newly developed scaffolds made of chemically cross-linked gelatin microsphere aggregates (C-GMSs). The rationale of this design lies in the creation and optimization of cell-material interfaces to enhance focal adhesion, proliferation, and function of anchorage-dependent functional cells. In vitro trials are carried out by coculturing human aortic endothelial cells (HAECs) and murine osteoblast precursor cells (MC3T3-E1) within C-GMS scaffolds, in which endothelialized bone-like constructs are yielded. Angiogenesis and osteogenesis induced by C-GMSs scaffold are further confirmed via subcutaneous-embedding trials in nude mice. In situ trials for the repair of critical-sized femoral defects are subsequently performed in rats. The acellular C-GMSs with interconnected macropores, exhibit the capability to recruit the endogenous cells (e.g., bone-forming cells, vascular forming cells, immunocytes) and then promote vascularized bone regeneration as well as integration with host bone.

Expanding tubular microvessels on stiff substrates with endothelial cells and pericytes from the same adult tissue

“…One critical aspect is perfusion, which is essential for the study of microvascular functions, including permeability, 64 , 65 mechanobiology, 66 tumor cell and immune cell infiltration. 67 More advanced microvascular models can be made based on our method in combination with other engineering technologies, such as microfluidics, 66 electrospinning, 68 microspheres, 69 and 3D printing. 57 …”

Progress in Gelatin as Biomaterial for Tissue Engineering

“…One of the purposes of tissue engineering is to create a scaffolding system for cells to provide a suitable environment that ensures tissue repair and healing. In this regard, as gelatin has good biocompatibility, biodegradability and low toxicity, it has been incorporated into some scaffolding systems [68,69]. For instance, Yao and colleagues confirmed the ability of gelatin-based scaffolds to promote osteogenesis both in vivo and in vitro by activating osteoclasts.…”

“…In vitro results showed the ability to assemble a bone-like endothelial structure, which was subsequently translated as an osteoinductive capacity in vivo. Unlike the vast majority of scaffolds, this forefront macroporous approach could address conventional rigid scaffold limitations, as it is a movable structure with abundant RGD motifs that allows for the formation of capillaries for tissue regeneration [69].…”

Translating Material Science into Bone Regenerative Medicine Applications: State-of-The Art Methods and Protocols

“…The human umbilical vein endothelial (HUVECs) cell line is commonly used to assess the effects of bone biomaterial on vessel formation in vitro [ 75 , 105 , 139 , 140 , 142 , 143 , 144 , 145 ]. As an alternative, the use of human aortic endothelial cells (HAECs) is also reported [ 146 ]. The tube formation assay is a classic angiogenesis assay that can be used to assess the angiogenic differentiation of HUVECs in contact with a specific biomaterial; the tube structures as well as the total branch length can be analyzed with a contrast inverted microscope [ 86 , 105 , 140 , 142 , 143 ].…”

“…Briefly, murine models are primarily used to evaluate the long-term integration of the scaffolds [ 78 , 123 , 146 ]. Rats [ 55 , 59 , 62 , 74 , 75 , 86 , 96 , 101 , 106 , 139 ] and rabbits [ 58 , 125 , 147 , 152 , 156 ] find wide use for bone regenerative applications to test osteogenesis, angiogenesis, immune response, resorption, and infections after biomaterial implantation.…”