Justin L. Perez

Correlation Between Facial Nerve Axonal Load and Age and Its Relevance to Facial Reanimation

Background: Two-stage facial reanimation procedures with a cross-facial nerve graft often have unsatisfactory results in the older patient. Although the cause of result variability is likely multifactorial, some studies suggest that increased donor nerve axonal load improves function of a free muscle transfer after a cross-facial nerve graft. This study attempts to characterize the relationship between age and facial nerve axonal load. Methods: Sixty-three fresh cadaveric heads were dissected to expose the facial nerve. For each hemiface, two facial nerve samples were taken: one proximal as the nerve exits the stylomastoid foramen, and one distal at the buccal branch (at a point 1 cm proximal to the anterior parotid border). Nerve samples were stained and quantified. Correlation analysis was completed using a Pearson correlation coefficient. Results: Thirty-six female and 27 male cadavers were dissected; their average age was 71 years (range, 22 to 97 years). At the proximal (r = −0.26; p < 0.01; n = 104) and distal (r = −0.45; p < 0.0001; n = 114) sampling points, there was a significant negative correlation between age and axonal load. Conclusions: As age increases, the axonal load of the facial nerve decreases at the buccal and zygomatic branches approximately 1 cm proximal to the anterior parotid border. The authors previously suggested this location as significant for cross-facial nerve coaptation. These results propose that decreasing axonal load can be a factor in the unsatisfactory outcomes of cross-facial grafting in the aging population. Moreover, this underscores the importance of recruiting more donor axons in attempting to improve facial reanimation in the older patient.

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.

Optimization of Vasculogenesis within Naturally-Derived, Biodegradable Hybrid Hydrogel Scaffolds

IntroductIon: Cellular ingrowth and neovascularization of acellular tissue-regeneration scaffolds represent the ratelimiting steps of permanent integration.1 In previous work, we have demonstrated that naturally-derived, biodegradable hybrid hydrogel scaffolds fabricated from a 10:1 w/w combination of alginate and type I collagen allow for maximal human umbilical vein endothelial cell (HUVEC) adherence and invasion in an in vitro wound healing model. We next sought to stimulate endothelial tubule formation within these scaffolds.

Abstract 103: Cad-Cam Tissue Engineering of Patient Specific Auricles for Reconstruction of Pediatric Microtia

Introduction: Autologous techniques for reconstruction of pediatric microtia may result in suboptimal aesthetic outcomes and morbidity from costal cartilage harvest. We sought to combine digital photogrammetry with CAD/CAM techniques to develop tissue-engineered auricular reconstructions that would mimic the normal anatomy of the patient-specific external ear while avoiding the morbidity of traditional reconstructions.