Angela Pineros-Fernandez

Octyl 2-cyanoacrylate for repair of peripheral nerve

The repair of peripheral nerves with sutures is time consuming. The aim of this study was to evaluate the benefits and functional outcome of repairing nerves with octyl 2-cyanoacrylate adhesive. The right peroneal nerve of 64 male, Lewis rats was sectioned and repaired. The rats were randomized into 3 experimental groups: A (n = 27), using only octyl 2-cyanoacrylate; B (n = 27), using 4, 10–0 nylon sutures; and C (n = 10), a sham operation. The recovery of nerve function was quantified through walking-track analyses; group A showed faster return of nerve function than B, especially at 15 days (P < 0.017). Histologic analysis showed a greater axonal regeneration in group A versus group B and no indication of tissue toxicity in group A. No dehiscence occurred during the 6-month study. Use of adhesive shortened the anastomosis time from 12 minutes to 4 minutes. These results indicate that the use of octyl 2-cyanoacrylate adhesive for nerve anastomoses is safe and effective and may have benefits compared with the use of sutures.

Complement Activation and STAT4 Expression Are Associated with Early Inflammation in Diabetic Wounds

Diabetic non-healing wounds are a major clinical problem. The mechanisms leading to poor wound healing in diabetes are multifactorial but unresolved inflammation may be a major contributing factor. The complement system (CS) is the most potent inflammatory cascade in humans and contributes to poor wound healing in animal models. Signal transducer and activator of transcription 4 (STAT4) is a transcription factor expressed in immune and adipose cells and contributes to upregulation of some inflammatory chemokines and cytokines. Persistent CS and STAT4 expression in diabetic wounds may thus contribute to chronic inflammation and delayed healing. The purpose of this study was to characterize CS and STAT4 in early diabetic wounds using db/db mice as a diabetic skin wound model. The CS was found to be activated early in the diabetic wounds as demonstrated by increased anaphylatoxin C5a in wound fluid and C3-fragment deposition by immunostaining. These changes were associated with a 76% increase in nucleated cells in the wounds of db/db mice vs. controls. The novel classical CS inhibitor, Peptide Inhibitor of Complement C1 (PIC1) reduced inflammation when added directly or saturated in an acellular skin scaffold, as reflected by reduced CS components and leukocyte infiltration. A significant increase in expression of STAT4 and the downstream macrophage chemokine CCL2 and its receptor CCR2 were also found in the early wounds of db/db mice compared to non-diabetic controls. These studies provide evidence for two new promising targets to reduce unresolved inflammation and to improve healing of diabetic skin wounds.

Advanced Imaging Techniques for Investigation of Acellular Dermal Matrix Biointegration

Background: Biointegration, a concept involving a dynamic interplay among three processes—inflammation, cellular infiltration, and angiogenesis—is key to understanding the interaction between acellular dermal matrices and the host. The current standard for evaluating acellular dermal matrix biointegration involves histologic analysis at fixed time points; however, the authors’ approach uses advanced imaging techniques to serially assess biointegration in real time. Methods: The authors have adapted two advanced imaging techniques—two-photon microscopy and photoacoustic microscopy—to investigate biointegration in a murine deepithelialized dorsal skin-fold window chamber model, specifically engineered to recapitulate the host microenvironment of acellular dermal matrix–assisted breast reconstruction. Four mice per group were assessed. Two-photon imaging of dual-transgenic mice allows for detection of fluorescently labeled perivascular cells, and macrophage lineage cells. Photoacoustic microscopy noninvasively assesses oxygen and hemoglobin concentration in living tissues, generating high-resolution, three-dimensional mapping of the nascent acellular dermal matrix–associated microvasculature and metabolic consumption of oxygen. These outcomes were corroborated by confirmatory histologic analysis at the terminal time point. Results: The acellular dermal matrix/host interface is characterized by robust inflammation (0 to 3 days), increased oxygen consumption and neoangiogenesis in the matrix border zone (10 to 14 days), and vascular and inflammatory cell penetration into the center of the matrix (>21 days). Conclusion: The data broaden the core knowledge of acellular dermal matrix biology, and serve as a potential template for elucidating the key differences among various commercially available and developmental products to guide the reconstructive surgeon to better select a reconstructive adjunct that meets their specific needs.

Plasticity of Auricular Cartilage in Response to Hormone Therapy

Introduction Correction of auricular deformities can be accomplished through splinting within the first few weeks of life. This is hypothesized to be due to retained circulating maternal estrogens decreasing the structural density of collagen; however, this has not been fully tested. Cartilage elasticity is dependent on the concentration of the proteoglycan aggregate, and hyaluronic acid, a constituent of proteoglycan aggregate, is increased by estrogens. Nonsurgical correction of these deformities in more developed patients has the potential to change clinical practice and eliminate surgical risks. Previous studies have demonstrated preliminary promise with the use of injectable estrogen to treat auricular deformities. For this study, we have validated an animal model and demonstrated the feasibility of a more therapeutically appropriate topical estrogen treatment in restoring neonatal plasticity of auricular cartilage. Methods Ears of 12 New Zealand rabbits were folded and splinted, and assigned an experimental group (estrogen, placebo, and untreated control) (n = 8 ears). Treatment ears received topical estrogen or placebo cream daily for 4 weeks, whereas controls received no treatment. The splints were removed following 2 additional weeks, and photographs were taken to calculate the retained fold angle. Biopsies were also taken for histologic analysis. Results The 8 control ears showed a statistically increased angle from a folded orientation of 46.6 degrees to return of ear position to a normal upright position of 151.2 degrees by the fourth day after splint removal. Both the estrogen-treated and placebo-treated ears responded to splinting with maintained folding (36.6 degrees and 32.5 degrees, respectively). Auricular cartilage thickness trended toward thicker in ears treated with estrogen, consistent with increased matrix components. Conclusions Estrogen and placebo treatment with splinting of ears lead to a significant change to the cartilage configuration, validating the model. The results of this study are very encouraging and provide the foundation for a noninvasive therapeutic approach for correcting auricular deformities. Future work will include a more detailed mechanistic study evaluating the dosing of estrogen and the efficiency of dermal penetration as well as evaluating the long-term outcomes and molecular mechanism-associated cartilaginous responses to estrogen.

Effects of Collagenase Digestion and Stromal Vascular Fraction Supplementation on Volume Retention of Fat Grafts

Objective The use of autologous fat as a soft tissue filler has increased over the past decade in both reconstructive and aesthetic surgeries. Enhancement of autologous fat grafts with the addition of the stromal vascular fraction (SVF) has been reported to improve long-term volume retention. Stromal vascular fraction is most commonly isolated using enzymatic digestion, but it is unknown what effect the digestion process has on the adipocytes and SVF cells that comprise the graft. Some clinicians have reported use of enzymatically digested fat grafts to alter the physical properties of the tissue in specialized applications. We have previously reported that increasing collagenase digestion duration adversely affects the viability of adipocytes and SVF cells. Here, we aimed to determine if collagenase digestion of adipocytes before grafting is detrimental to long-term graft retention and if SVF supplementation can abrogate these potential deleterious effects. Methods and Results We used a published xenograft model in which human lipoaspirate was implanted into the scalp of immunocompromised mice to study the effects of collagenase digestion on in vivo graft survival after 12 weeks. We used 4 experimental groups: grafts composed of collagenase-digested and nondigested adipocytes (50-minute digestion) and grafts with and without SVF supplementation. We used microcomputed tomography to serially and noninvasively quantify graft volume, in conjunction with hematoxylin-eosin staining of histological cross-sections of implanted and excised grafts to assess overall tissue viability. We found that adipocytes that were collagenase-digested before implantation had significantly lower retention rates at 12 weeks and poorer tissue health, which was assessed by quantifying the number of intact adipocytes, the number of cystic formations, and by scoring the degree of inflammation and fibrosis. Further, we found that SVF supplementation of the digested grafts improved graft survival, but not to the level observed in undigested grafts. Conclusions We conclude that collagenase digestion adversely affects the long-term volume retention of fat grafts, but that graft retention is improved by SVF supplementation. These experimental results can serve as an initial framework to further elucidate the reported efficacy and safety of using collagenase-digested fat grafts and SVF in the clinical setting.

Abdominal Wall Allograft: Preclinical Biomechanical Investigation of a Novel Reconstructive Adjunct

Introduction Acellular dermal matrices have revolutionized abdominal wall reconstruction; however, device failure and hernia recurrence remain significant problems. Fascia grafts are a reconstructive adjunct with increased tensile strength compared with acellular dermal matrices; however, clinical use is limited by insufficient donor material and donor site morbidity. To this end, we investigate the biomechanical properties of human abdominal wall allografts (AWAs) consisting of the anterior rectus sheath from xiphoid to pubis. Methods After cadaveric procurement of 6 human AWAs, the tissue was divided horizontally and a matched-sample study was performed with specimens randomized to 2 groups: fresh, unprocessed versus processed with gamma irradiation and decellularization. Specimens were evaluated for physical properties, DNA content, tensile strength, and electron microscopy. Results All AWA donors were male, with a mean age of 55.2 years (range, 35–74 years). Procured AWAs had a mean length of 21.70 ± 1.8 cm, width of 14.30 ± 1.32 cm, and area of 318.50 cm2, and processing resulted in a 98.3% reduction in DNA content. Ultimate tensile strength was significantly increased after tissue processing, and after subcutaneous implantation, processed AWA demonstrated 4-fold increased tensile strength compared with unprocessed AWAs. Conclusions Acellular AWAs represent a novel reconstructive adjunct for abdominal wall reconstruction with the potential of replacing “like with like” without additional donor site morbidity or antigenicity.