Abstract
Using scaffolds with appropriate porosity represents a potential approach for repair of critical-size bone defects. Vascularization is essential for bone formation and healing. This study investigates methods for monitoring angiogenesis within porous biopolymer scaffolds on the basis of polyhydroxybutyrate (PHB)/chitosan. We use the chick and quail chorioallantoic membrane (CAM) assay as an in vivo model focused on the formation of new blood vessels inside the implant structure. Chemical properties of the surface in biopolymer scaffold matrix were characterized as well as the tissue reaction of the CAM. Implantation of a piece of polymer scaffold results in vascular reaction, documented visually and by ultrasound biomicroscopy. Histological analysis shows myofibroblast reaction (smooth muscle actin-positive cells) without excessive collagen deposition. Cell invasion is observed inside the implant, and QH1 marker, detecting hemangioblasts and endothelial cells of quail origin, confirms the presence of vascular network. The CAM assay is a rapid and easy way to test biocompatibility and vasculogenic potential of new candidate scaffolds for bone tissue bioengineering with respect to the 3R´ s.
Highlights
Regeneration maintains or renews the original tissue architecture
Dimensions of individual fibers have to be sufficient for crystallization into coherent regions, which was demonstrated by the XRD analysis (Fig. 2)
Previous studies have reported that various versions of chitosan-based scaffolds may support angiogenesis for different applications (Deng et al, 2010; Wang et al, 2012; Linn et al, 2003; Agarwal et al, 2016; Shahzadi et al, 2016); only few studies have investigated this for the field of bone tissue engineering and these were only able to show evidence of angiogenesis on the scaffold surface (Pan et al, 2018; Ahmadi et al, 2010) or found that chitosan-acetate may inhibit angiogenesis (Shah et al, 2014)
Summary
In case of damage or chronic degenerative disease, fibrotic repair occurs instead of the normal regenerative process. Such a response is considered a reparative process, since the replacement tissue neither contains the original cell types nor is the original tissue architecture reestablished (Stocum, 2002). Angiogenesis is the physiological process of forming new capillaries from existing vessels It is a tiered process involving activation of the existing endothelial cells, degradation of the extracellular matrix, proliferation and migration of endothelial cells, invasion of the stroma by the surrounding cells, and remodeling the extracellular matrix. Induction of angiogenesis and subsequent development of a vascular bed in the engineered tissue is being actively pursued through combinations of physical and chemical cues, notably through the presentation of suitable topographies and growth factors (Klagsburn and Moses, 1999; Liu et al, 2012; Kant and Coulombe, 2018)
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