Construction of nanofibrous scaffolds with interconnected perfusable microchannel networks for engineering of vascularized bone tissue

Abstract

Vascularization and bone regeneration are two closely related processes during bone reconstruction. A three-dimensional (3D) scaffold with porous architecture provides a suitable microenvironment for vascular growth and bone formation. Here, we present a simple and general strategy to construct a nanofibrous poly( l -lactide)/poly(ε-caprolactone) (PLLA/PCL) scaffold with interconnected perfusable microchannel networks (IPMs) based on 3D printing technology by combining the phase separation and sacrificial template methods. The regular and customizable microchannel patterns within the scaffolds (spacings: 0.4 mm, 0.5 mm, and 0.6 mm; diameters: 0.8 mm, 1 mm, and 1.2 mm) were made to investigate the effect of microchannel structure on angiogenesis and osteogenesis. The results of subcutaneous embedding experiment showed that 0.5/0.8-IPMs (spacing/diameter = 0.5/0.8) and 0.5/1-IPMs (spacing/diameter = 0.5/1) scaffolds exhibited more vascular network formation as compared with other counterparts. After loading with vascular endothelial growth factor (VEGF), VEGF@IPMs-0.5/0.8 scaffold prompted better human umbilical vein endothelial cells (HUVECs) migration and neo-blood vessel formation, as determined by Transwell migration, scratch wound healing, and chorioallantoic membrane (CAM) assays. Furthermore, the microangiography and rat cranial bone defects experiments demonstrated that VEGF@IPMs-0.5/0.8 scaffold exhibited better performance in vascular network formation and new bone formation compared to VEGF@IPMs-0.5/1 scaffold. In summary, our results suggested that the microchannel structure within the scaffolds could be tailored by an adjustable caramel-based template strategy, and the combination of interconnected perfusion microchannel networks and angiogenic factors could significantly enhance vascularization and bone regeneration.

Stat3 Signaling Pathway: A Future Therapeutic Target for Bone-Related Diseases

“…In large-scale bone defects and delayed fracture healing, phosphorylation-activated Stat3 increased the rate of bone regeneration at the defect site by enhancing MSC osteogenic differentiation and vascularization ( Yu et al, 2019 ; Chen et al, 2021 ). Coupling of angiogenesis and osteogenesis is imperative for post-traumatic bone regeneration, the activation of Stat3 in vascular endothelial cells would facilitate migration and angiogenesis, which could be a new way to exploit therapy for fracture and osteonecrosis ( Chim et al, 2015 ; Gu et al, 2021 ). The aforementioned studies shed a light on the regulatory mechanisms and the great therapeutic potential of Stat3 ( Figure 1 ).…”

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

“…In recent years, various vascularization strategies have been developed by manipulating the elements that are involved in physiological angiogenesis, such as scaffold materials, [ 7,8,9 ] vascular cells, [ 10,11 ] hypoxia, [ 12 ] and growth factors. [ 13 ] Among them, three‐dimensional (3‐D) scaffolding materials with adjustable biophysical cues (e.g., porous architectures, [ 14 ] degradation, [ 15 ] surface topographies [ 16 ] ) can influence the behaviors (e.g., adhesion, spreading, proliferation, and differentiation) of loaded angiogenic cells and vascularization. [ 17 ] In addition to pre‐vascularization in vitro, it is more important to engineering a universal scaffolding platform with favorable 3‐D geometries and microenvironments that can effectively recruit endogenous angiogenic cells (e.g., endothelial cells, endothelial progenitor cells) in vivo and then achieve vascularization and angiogenesis in situ.…”

Adjusting the accuracy of PEGDA-GelMA vascular network by dark pigments via digital light processing printing

“…1,2 The rapid realization of functionalized regeneration of the transplanted bone scaffold for BTE may depend on a certain amount of angiogenesis. 3 If the implanted scaffolds rely on the blood vessels of the host to grow inward, the scarcity of oxygen and nutrients required for cell metabolism may lead to the ischemic death of cells away from the blood vessel. 4 Therefore, it is necessary to construct a microchannel in artificial tissues to increase the survival of large-scale multicellular organisms.…”

“…4 Therefore, it is necessary to construct a microchannel in artificial tissues to increase the survival of large-scale multicellular organisms. 3,[5][6][7] Taking the skull vascular network as an example, there are a large number of multiscale venous networks in the diploe (called the diploic vein, Figure 1(a)) between the inner and outer laminas of the natural skull 8 (Figure 1(b)). Hollow blood vessels are particularly relevant for modeling macroscale organ biology, 9 including the cell growth mechanism in the blood vessels of the artificial tissue.…”

“…10,11 In the vascularization of skull scaffolds, the three-dimensional (3D) vascular network has better nutrient exchange and cell perfusion capabilities. 3,9,10 Recent research on engineered multi-scale microchannels such as vessel-on-chip models, 5,12 3D blood vessels, 10,13 and prefabricated scaffolds with vascular structures 10,[13][14][15][16][17][18][19] shows promise, but there are still challenges in the precise direct fabrication of hollow hierarchical vascular networks with biocompatible hydrogels. Direct manufacturing of complex spatial structures 12,20 is more efficient and accurate than indirect manufacturing, 10,[13][14][15][16][17][18][19] which helps to simulate the real cell growth microenvironment.…”