Nasal Reconstruction: Current Overview.

The nose, with its conspicuous location, intricate convexities, and delicate 3-dimensional structure, continues to challenge the reconstructive surgeon. Today, there are a myriad of options available for reconstruction. The practitioner must take into account the location of the defect as well as the components needed to be restored. This article addresses the current practices in nasal reconstruction, including the different strategies for skin coverage, nasal lining, and structural support. We discuss both the newest techniques as well as basic principles of this long-standing procedure.

Prevention of vein graft intimal hyperplasia with photochemical tissue passivation.

OBJECTIVE: Saphenous vein is the conduit of choice for bypass grafting. Saphenous vein grafts have poor long-term patency rates because of intimal hyperplasia (IH) and subsequent accelerated atherosclerosis. One of the primary triggers of IH is endothelial injury resulting from excessive dilation of the vein after exposure to arterial pressures. Photochemical tissue passivation (PTP) is a technology that cross-links adventitial collagen by a light-activated process, which limits dilation by improving vessel compliance. The objective of this study was to investigate whether PTP limits the development of IH in a rodent venous interposition graft model. METHODS: PTP is accomplished by coating venous adventitia with a photosensitizing dye and exposing it to light. To assess the degree of collagen cross-linking after PTP treatment, a biodegradation assay was performed. Venous interposition grafts were placed in the femoral artery of Sprague-Dawley rats. Rats were euthanized after 4 weeks, and intimal thickness was measured histologically. Vein dilation at the time of the initial procedure was also measured. RESULTS: Time to digestion was 63 ± 7 minutes for controls, 101 ± 2.4 minutes for rose bengal (RB), and 300 ± 0 minutes for PTP (P < .001 PTP vs control). A total of 37 animals underwent the procedure: 12 PTP, 12 RB only, and 13 untreated controls. Dilation of the graft after clamp release was 99% for control, 65% for RB only, and 19% for PTP-treated (P < .001 PTP vs control). Intimal thickness was 77 ± 59 µm in controls, 60 ± 27 µm in RB only, and 33 ± 28 µm in PTP-treated grafts. There was a statistically significant 57% reduction in intimal thickness after treatment with PTP compared with untreated controls (P = .03). CONCLUSIONS: PTP treatment of venous interposition grafts in a rat model resulted in significant collagen cross-linking, decreased vessel compliance, and significant reduction in IH.

Burn Ear Reconstruction Using Porous Polyethylene Implants and Tissue Expansion.

Reconstruction of the external ear after a burn is particularly challenging. The nature of the injury poses many problems including excessive scar tissue, poor blood supply, and the lack of adequate and appropriate materials for a framework. The use of costochondral grafts often leads to marginal outcomes which do not justify the morbidity. Children under the age of 10 years commonly have insufficient cartilage for a graft. Medpor (Stryker, Kalamazoo, MI) offers minimal morbidity and a very effective result. In this series, the authors describe the experience using Medpor and scalp tissue expansion to reconstruct severely burned ears. A total of 16 pediatric patients underwent 18 reconstructions, with two patients receiving bilateral procedures. All patients received Medpor implants. Thirteen patients were tissue expanded under the subgaleal plane before reconstruction, for concomitant scalp alopecia reconstruction. Eleven temporoparietal fascial flaps were performed. In the remaining patients, coverage of the implant was achieved by local advancement flaps. Only two patients had complications, with exposure of the construct after several years. In these two cases, the implants were removed. The experience has shown porous polyethylene reconstruction to be very efficient, with low morbidity and good cosmetic outcomes. Medpor is an excellent option for the reconstruction of both fully and partially burned ears as you may implant only the helical rim, base, or both pieces. The best results were achieved after tissue expansion and the use of the alopecic skin overlying a temporoparietal fascial flap. This has become the preferred method.

Comparative analysis of processing methods in fat grafting.

BACKGROUND: Centrifugation is a popular processing method, with an unclear mechanism of action. Hypotheses include fat concentration, reduced inflammatory response by removal of blood, and concentration of adipose-derived stem cells. The authors performed multiple experiments to determine the role of centrifugation and compared it with a different processing method (mesh/gauze technique). METHODS: Lipoaspirate components were quantified after centrifugation at increasing speed to determine concentration efficacy. For comparison, the authors quantified the concentration efficacy of mesh/gauze. They also compared the number of adipose-derived stem cells isolated by either method. To determine the effects of each component, they compared fat alone to fat mixed with various spinoff components in a mouse model. They also compared centrifugation to mesh/gauze. RESULTS: The adipocyte fraction remains constant above 5000 g, whereas 1200 g results in 91 percent concentrated fat. Mesh/gauze also results in 90 percent concentrated fat. The number of adipose-derived stem cells in 1 g of fat was 1603 ± 2020 and 1857 ± 1832 in the centrifuge and mesh/gauze groups, respectively (p = 0.86). Five "add-back" groups were created: fat plus oil, fat plus surgical tumescence, fat plus fresh tumescence, fat plus cell pellets and fresh tumescence, and fat plus cell pellets. The fat-only group had better retention than the groups mixed with tumescence, regardless of whether it was surgical, fresh, or had cell pellets. Oil did not affect grafts. Centrifugation at 1200 g was equivalent to mesh/gauze (0.73 ± 0.12 g and 0.72 ± 0.13 g, respectively). CONCLUSIONS: Centrifugation improves graft retention by concentration of the adipocyte fraction. The concentration efficacy of mesh/gauze is equivalent to centrifugation at 1200 g, with equivalent in vivo outcomes.

Prevention of capsular contracture with photochemical tissue passivation.

BACKGROUND: Capsular contracture is the most common complication following the insertion of breast implants. Within a decade, half of patients will develop capsular contracture, leading to significant morbidity and need for reoperation. There is no preventative treatment available and the recurrence rate remains high. Photochemical tissue passivation is a novel tissue-stabilization technique that results in collagen cross-linking. It can rapidly link collagen fibers in situ, preserving normal tissue architecture. By using this therapy to passivate the collagenous tissues of the implant pocket, the authors hope to prevent the development of pathogenic collagen bundles and subsequent capsule contracture. METHODS: Six-cubic centimeter tissue expanders were placed below the panniculus carnosus muscle along the dorsum of New Zealand white rabbits. Fibrin glue was instilled into each implant pocket to induce contracture. Treated pockets received photochemical tissue passivation by coating them with a photosensitizing dye and exposing the area to a 532-nm light. After 8 weeks, capsule tissue was harvested for histologic evaluation. RESULTS: Implant capsule thickness is the number one prognostic factor for contracture development. The authors demonstrated a 52 percent decrease in capsule thickness in the passivated group compared with controls. Photochemical tissue passivation resulted in fewer fibrohistiocytic cells and macrophages and in reduced synovial metaplasia and smooth muscle actin deposition. CONCLUSIONS: Photochemical tissue passivation significantly decreased both capsule thickness and smooth muscle actin deposition. It is a promising technique for preventing capsular contracture that can be performed at the time of initial surgery without a significant increase in procedure time.

Micro-mechanical fractional skin rejuvenation.

BACKGROUND: The most commonly performed skin rejuvenation procedure, laser resurfacing, is associated with adverse events and significant expense. The authors have developed a novel device that uses micro-coring needles to remove tissue in a fractional pattern and avoid the side effects of laser therapy. The authors compare the efficacy of these needles to standard needles in a pig model. METHODS: One swine was treated with three needle types: standard hypodermic, solid hypodermic, and the authors' novel coring needles. Thirty-two 1 × 1-inch sites per flank received either 20 or 40 percent treatment coverage. Photographs were taken and punch biopsies were performed at days 0, 7, 28, 56, and 84. Biopsy specimens were evaluated for histology and collagen content. RESULTS: All treatment sites healed quickly, with no evidence of scarring or infection. Coring sites were easily identified and contained increased fibroblast activity and newly synthesized collagen. At 1 month, the papillary dermis and epidermis of the coring sites were up to 196 percent thicker compared with controls (p < 0.001). The coring sites had enhanced undulating rete ridges-consistent with regeneration. At 3 months, a pronounced increase in collagen fibers and newly organized and augmented elastic fibers was seen. Enzyme-linked immunosorbent assay confirmed an 89 percent increase in collagen content in these coring sites (p < 0.001). CONCLUSIONS: This novel approach to skin rejuvenation was found to effectively induce the microscopic and biological endpoints of skin rejuvenation. This may provide a new modality for the safe and cost-effective treatment of age-related rhytides, skin laxity, photodamage, scarring, and striae.

Normal relationship of beta- and non-beta-cells not needed for successful islet transplantation.

Islets are composed mostly of beta-cells, and therefore stem cell research has concentrated on generating purified beta-cells, neglecting the other endocrine cell types in the islet. We investigated the presence of endocrine non-beta-cells after islet transplantation. In addition, we studied whether the transplantation of pure beta-cells, in volumes similar to that used in islet transplantation, would suffice to reverse hyperglycemia in diabetic mice. Rat islets were dispersed and beta-cells were purified by fluorescence-activated cell sorting according to their endogenous fluorescence. After reaggregation, 600 islet equivalents of the purified beta-cell aggregates were implanted into diabetic SCID mice. In mice implanted with beta-cell-enriched aggregates, the hyperglycemia was reversed and good graft function over a 12-week period was observed with regard to glucose and insulin levels, glucose tolerance tests, and graft insulin content. The endocrine cell composition of the beta-cell-enriched aggregates remained constant; before and 12 weeks after transplantation, the beta-cell-enriched aggregates comprised 95% beta-cells and 5% endocrine non-beta-cells. However, islet grafts, despite originally having comprised 75% beta-cells and 25% endocrine non-beta-cells, comprised just 5% endocrine non-beta-cells after transplantation, indicating a loss of these cells. beta-Cell-enriched aggregates can effectively reverse hyperglycemia in mice, and transplanted intact islets are depleted in non-beta-cells. It is therefore likely that islet non-beta-cells are not essential for successful islet transplantation.

Transplantation of islets transduced with CTLA4-Ig and TGFbeta using adenovirus and lentivirus vectors.

BACKGROUND: A major problem facing islet transplantation is immune destruction of grafts by transplant rejection and autoimmunity. Some success in prolonging graft rejection has been obtained by transducing islets prior to transplantation with adenoviral (Ad) vectors containing CTLA4-Ig and TGFbeta. The purpose of this study was to see if lentiviral (LV) vectors would provide superior results compared with adenoviral vectors. METHODS: Islets were isolated from Sprague-Dawley rats and transduced with Ad or LV vectors containing LacZ, CTLA4-Ig, CTLA4, and TGFbeta1 using various MOIs. Islets transduced with LV were healthy as judged by DNA and insulin content, and insulin secretion. Using the kidney capsule transplant site, 500 transduced rat islets were transplanted into streptozotocin diabetic B6AF1 mice. RESULTS: Maintenance of normoglycemia was prolonged in recipient mice carrying islets transduced with Ad vectors containing CTLA4-Ig, CTLA4, and TGFbeta1. Return of hyperglycemia in controls was 17-18 days while loss of function for the experimental groups occurred at 20-27 days. For the lentivirus transduced islets, rejection of controls was 20+/-1.6 days, for CTLA4-Ig was 42+/-21 days and for TGFbeta was 28+/-3.2 days. CONCLUSIONS: Although islets transduced with either adenovirus or lentivirus containing CTLA4-Ig, CTLA4, and TGFbeta1 could prolong graft survival in a rat to mouse transplantation model, with the conditions of this study lentivirus provided no advantage over adenovirus vectors.