Reduction of suture associated inflammation after 28 days using novel biocompatible pseudoprotein poly(ester amide) biomaterials.

Sutures elicit an inflammatory response, which may impede the healing process and result in wound complications. We recently reported a novel family of biocompatible, biodegradable polymers, amino acid-based poly(ester amide)s (AA-PEA), which we have shown to significantly attenuate the foreign body inflammatory response in vitro. Two types of AA-PEA (Phe-PEA and Arg-Phe-PEA) were used to coat silk or plain-gut sutures, which were implanted in the gluteus muscle of C57BL/6 mice, while the uncoated control sutures were implanted in the contralateral side. After 3, 7, 14, and 28 days the mean area of inflammation surrounding the sutures was compared. Phe-PEA coating of silk sutures significantly decreased inflammation compared with noncoated controls (67.8 ± 17.4% after 3d [p = 0.0014], 51.6 ± 7.2% after 7d [p < 0.001], and 37.3 ± 8.3% after 28d [p = 0.0001]) when assessed via analysis of photomicrographs using digital image software. Phe-PEA coated plain-gut sutures were similarly assessed and demonstrated a significant decrease in the mean area of inflammation across all time points (54.1 ± 8.3% after 3 d, 41.4 ± 3.9% after 7 d, 71.5 ± 8.1% after 14 d, 78.4 ± 8.5%, and after 28 d [all p < 0.0001]). Arg-Phe-PEA coated silk demonstrated significantly less inflammation compared to noncoated controls (61.3 ± 9.4% after 3 d, 44.7 ± 4.7% after 7 d, 19.6 ± 8%, and 38.3 ± 6.8% after 28 d [all p < 0.0001]), as did coated plain-gut (37.4 ± 8.3% after 3 d [p = 0.0004], 55.0 ± 7.8% after 7 d [p < 0.0001], 46.0 ± 4.6% after 14 d [p < 0.0001], and 59.0 ± 7.9% after 28 d [p < 0.0001]). Both Phe-PEA and Arg-Phe-PEA coatings significantly decrease the inflammatory response to sutures in vivo for up to 28 days.

Fabrication and in vivo microanastomosis of vascularized tissue-engineered constructs.

Tissue engineering endeavors to create replacement tissues and restore function that may be lost through infection, trauma, and cancer. However, wide clinical application of engineered scaffolds has yet to come to fruition due to inadequate vascularization. Here, we fabricate hydrogel constructs using Pluronic(®) F127 as a sacrificial microfiber, creating microchannels within biocompatible, biodegradable type I collagen matrices. Microchannels were seeded with human umbilical vein endothelial cells (HUVEC) or HUVEC and human aortic smooth muscle cells (HASMC) in co-culture, generating constructs with an internal endothelialized microchannel. Histological analysis demonstrated HASMC/HUVEC-seeded constructs with a confluent lining after 7 days with preservation and further maturation of the lining after 14 days. Immunohistochemical staining demonstrated von Willebrand factor and CD31(+) endothelial cells along the luminal surface (neointima) and alpha-smooth muscle actin expressing smooth muscle cells in the subendothelial plane (neomedia). Additionally, the deposition of extracellular matrix (ECM) components, heparan sulfate and basal lamina collagen IV were detected after 14 days of culture. HUVEC-only- and HASMC/HUVEC-seeded microchannel-containing constructs were microsurgically anastomosed to rat femoral artery and vein and perfused, in vivo. Both HUVEC only and HUVEC/HAMSC-seeded constructs withstood physiologic perfusion pressures while their channels maintained their internal infrastructure. In conclusion, we have synthesized and performed microvascular anastomosis of tissue-engineered hydrogel constructs. This represents a significant advancement toward the generation of vascularized tissues and brings us closer to the fabrication of more complex tissues and solid organs for clinical application.

Vascular smooth muscle cell optimization of vasculogenesis within naturally derived, biodegradable, hybrid hydrogel scaffolds.

BACKGROUND: As vascularization represents the rate-limiting step in permanent incorporation of hydrogel-based tissue-regeneration templates, the authors sought to identify the material chemistry that would optimize endothelial cell adhesion and invasion into custom hydrogel constructs. The authors further investigated induction of endothelial tubule formation by growth factor supplementation and paracrine stimulation. METHODS: Hydrogel scaffolds consisting of combinations of alginate, collagen type I, and chitosan were seeded with human umbilical vein endothelial cells and maintained under standard conditions for 14 days. Cell density and invasion were then evaluated. Tubule formation was evaluated following basic fibroblast growth factor addition or co-culture with human aortic smooth muscle cells. RESULTS: Human umbilical vein endothelial cells demonstrated greatest cell-surface density and invasion volumes with alginate and collagen (10:1 weight/weight) scaffolds (p < 0.05). Supplementation with basic fibroblast growth factor increased surface density but neither invasion nor tubule formation. A significant increase in tubule content/organization was observed with increasing human aortic smooth muscle cell-to-human umbilical vein endothelial cell ratio co-culture. CONCLUSIONS: Alginate and collagen 10:1 scaffolds allow for maximal cellularization compared with other combinations studied. Growth factor supplementation did not affect human umbilical vein endothelial cell invasion or morphology. Paracrine signaling by means of co-culture with human umbilical vein endothelial cells stimulated endothelial tubule formation and vascular protonetwork organization. These findings serve to guide future endeavors toward fabrication of prevascularized tissue constructs.