Tissue engineering of recellularized small-diameter vascular grafts.

A tissue-engineered small-diameter arterial graft would be of benefit to patients requiring vascular reconstructive procedures. Our objective was to produce a tissue-engineered vascular graft with a high patency rate that could withstand arterial pressures. Rat arteries were acellularized with a series of detergent solutions, recellularized by incubation with a primary culture of endothelial cells, and implanted as interposition grafts in the common femoral artery. Acellular grafts that had not been recellularized were implanted in a separate group of control animals. No systemic anticoagulants were administered. Grafts were explanted at 4 weeks for definitive patency evaluation and histologic examination; 89% of the recellularized grafts and 29% of the control grafts remained patent. Elastin staining demonstrated the preservation of elastic fibers within the media of the acellular grafts before implantation. Immunohistochemical staining of explanted grafts demonstrated a complete layer of endothelial cells on the lumenal surface in grafts that remained patent. Smooth muscle cells were observed to have repopulated the vessel walls. The mechanical properties of the matrix were comparable to native vessels. Such a strategy may present an alternative to autologous harvest of small vessels for use in vascular bypass procedures.

The effect of rate of distraction osteogenesis on structure and function of anterior digastric muscle fibers.

The authors hypothesized that distraction at a rate of 3 mm/day, compared with mandibular distraction at a rate of 1 mm/day, would produce a maladaptive response in adjacent muscles of mastication. The authors further hypothesized that the maladaptive response would manifest at the single fiber level by means of increased sarcomeric heterogeneity, decreased maximum force output, and increased susceptibility to stretch-induced injury. In an ovine model, distraction osteogenesis of the right hemimandible was performed at either 1 mm/day for 21 days (n = 2) or 3 mm/day for 7 days (n = 2) to achieve a total distraction distance of 21 mm. The left hemimandibles served as controls. After a consolidation period of 2 days, the anterior digastric muscles were harvested; in six randomly selected single fibers from each muscle, maximum calcium-activated force (Po) was measured at optimal sarcomere length. The amount of damage to the sarcomeres in each fiber was assessed microscopically. To test susceptibility to contraction-induced injury, each fiber was given an activated stretch of 20 percent. Compared with control fibers and fibers distracted at 1 mm/day, maximum tetanic force (Po) was significantly lower in fibers distracted at 3 mm/day. Compared with control fibers, specific Po (Po/cross-sectional area) was lower in fibers distracted at 3 mm/day. The number of sarcomeres appearing damaged in fibers distracted at 3 mm/day was significantly higher than in control fibers or in fibers distracted at 1 mm/day. A greater deficit in Po was observed after a single activated stretch in fibers distracted at 3 mm/day than in control fibers or in fibers distracted at 1 mm/day. The authors conclude that distraction of the anterior digastric muscle in sheep at 3 mm/day produces a maladaptive response in the muscle fibers but a rate of 1 mm/day is tolerated by the muscle fibers. These data are consistent with the hypothesis that distraction of skeletal muscle at high rates results in increased heterogeneity of sarcomere lengths and that this increase in heterogeneity is the most likely potential mechanism resulting in whole muscle force deficits and in increased susceptibility to stretch-induced injury in distracted muscles.

Uvulopalatopharyngoplasty with tonsillectomy and adenoidectomy as a treatment for obstructive sleep apnea in neurologically impaired children.

RATIONALE: Children with neurologic impairment often present with airway obstruction that may require intervention. No single method of airway intervention is universally appropriate and effective in this patient population. This study was performed to examine the effectiveness of using adenotonsillectomy and uvulopalatopharyngoplasty (UPPP) in resolving obstructive apnea (OA) in patients with neurologic impairment. METHODS: A retrospective chart review of 15 patients with neurologic impairment and OA treated with adenotonsillectomy and UPPP between 1986 and 1998 at Children's Hospital of Wisconsin (CHW) was performed. All patients in the series had their primary area of obstruction in the posterior oropharynx involving the soft palate, pharyngeal walls and base of tongue. Post-operative improvement following adenotonsillectomy and UPPP was examined. Measures of improvement were based primarily on recorded lowest oxygen saturations, but clinical parameters, flexible upper airway endoscopy and polysomnography were used as well. RESULTS: Patient improvement was documented in 87% of patients treated with this modality. For the group, the mean lowest recorded oxygen saturation demonstrated a statistically significant improvement from 65% pre-operatively to 85% post-operatively (P = 0.005). In long-term follow-up of these patients, 77% (10 of 13) of those showing initial improvement have done well and have required no further airway intervention. However, 23% of these patients demonstrated the need for further airway intervention during follow-up. CONCLUSIONS: Adenotonsillectomy with UPPP is worthy of consideration in certain neurologically impaired patients with moderate to severe OA, limited primarily to the posterior pharyngeal area. Initial improvement may not be permanent and close long-term follow-up of patients is imperative.