In vivo tissue engineering has been explored as a method to repopulate scaffolds with autologous cells to create a functional, living, and non-immunogenic tissue substitute. In this study, we describe an approach to in vivo cellular repopulation of a tissue-derived tubular elastin scaffold. Pure elastin scaffolds were prepared from porcine carotid arteries (elastin tubes). Elastin tubes were filled with agarose gel containing basic fibroblast growth factor (bFGF) to allow sustained release of growth factor. These tubes were implanted in subdermal pouches in adult rats. The elastin tubes with growth factor had significantly more cell infiltration at 28 days than those without growth factor. Immunohistochemical staining indicated that most of these cells were fibroblasts, of which a few were activated fibroblasts (myofibroblasts). Microvasculature was also observed within the scaffolds. Macrophage infiltration was seen at 7 days, which diminished by 28 days of implantation. None of the elastin tubes with bFGF calcified. These results demonstrated that the sustained release of bFGF brings about repopulation of elastin scaffolds in vivo while inhibiting calcification. Results showing myofibroblast infiltration and vascularization are encouraging since such an in vivo implantation technique could be used for autologous cell repopulation of elastin scaffolds for vascular graft applications.

In vivo tissue engineering has been explored as a means to create autologous vascular replacements. Elastin is necessary to sustain continual pulsatile flow and to prevent the dilatation of vascular tissues. Unfortunately, elastogenesis in tissue-engineered constructs has been very limited. To overcome this limitation, we have created tubular elastin scaffolds from porcine carotid arteries. Elastin would provide the necessary elasticity to the graft on implanting these scaffolds as vascular grafts. In this study, elastin tubes with agarose gel containing either stromal-derived factor-1 alpha [SDF; for homing of endothelial cells (ECs)] or basic fibroblast growth factor (bFGF; for homing of myofibroblasts) were implanted into adipose tissue, as it is a known source of stem/progenitor cells. We also implanted these tubes into subdermal pouches (as a control location). We observed a difference in the types of cells recruited-ECs were recruited in large numbers by SDF in the adipose tissue, whereas the adipose-FGF group had a vascularized (smooth muscle and EC-positive), collagenous capsule (adventitia) with many smooth muscle alpha-actin (SMA)-positive cells in the elastin scaffold layer (media). These results were in contrast to the subdermal group, which only recruited fibroblasts and some SMA-positive cells. Also, more cell infiltration and neo-collagen formation was seen in adipose implants. This study provides novel results by the use of specific cytokines and implant locations to recruit tissue-specific cells to create autologous vascular grafts.

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