Regenerative vs flap-based limb salvage: a multi-centered, prospective, randomized controlled trial.

Aim: The goal of this study was to compare success rates of a regenerative limb salvage approach (rLS) using dehydrated human chorion amnion membrane (dHACM) to traditional flap-based limb salvage (fLS). Materials & methods: This prospective RTC enrolled patients presenting with complex extremity wounds over a 3-year period. Primary outcomes included success of primary reconstruction, persistence of exposed structures, time to definitive closure, and time to weight bearing. Results: Patients meeting inclusion criteria were randomized to fLS (n = 14) or rLS (n = 25). The primary reconstructive method was successful for 85.7% of fLS subjects and 80% of rLS subjects (p = 1.00). Conclusion: This trial provides strong evidence that rLS is an effective option in the setting of complex extremity wounds, with success rates comparable to traditional flaps. Clinical Trial Registration: NCT03521258 (ClinicalTrials.gov).

Chronic and traumatic wounds may result in loss of limb without appropriate medical treatment. Traditionally large wounds with exposed bone or other important structures require surgery to transfer healthy soft tissue (a tissue flap) from one area of the body to the defect created by the wound. Our study seeks to demonstrate an approach to similar wounds using a biologic dressing to avoid extensive surgery. We demonstrate that this biologic dressing made from human membranes has a similar success rate to flap surgery for achieving wound healing.

Large Animal Models of Vascularized Composite Allotransplantation: A Review of Immune Strategies to Improve Allograft Outcomes.

Over the past twenty years, significant technical strides have been made in the area of vascularized composite tissue allotransplantation (VCA). As in solid organ transplantation, the allogeneic immune response remains a significant barrier to long-term VCA survival and function. Strategies to overcome acute and chronic rejection, minimize immunosuppression and prolong VCA survival have important clinical implications. Historically, large animals have provided a valuable model for testing the clinical translatability of immune modulating approaches in transplantation, including tolerance induction, co-stimulation blockade, cellular therapies, and ex vivo perfusion. Recently, significant advancements have been made in these arenas utilizing large animal VCA models. In this comprehensive review, we highlight recent immune strategies undertaken to improve VCA outcomes with a focus on relevant preclinical large animal models.

A Single-Institution Case Series of Outpatient Same-Day Mastectomy: Implementation of a Quality Improvement Project and Initiative for Enhanced Recovery After Surgery.

Background: National data demonstrate a trend toward outpatient same-day mastectomy. The possible drivers of this change include the costs related to hospital admission and effective management of postoperative pain. We retrospectively analyzed our single-institution experience with outpatient same-day mastectomy that incorporates a multimodal pain management regimen. Methods: We retrospectively reviewed the medical records of patients who underwent same-day mastectomy at a single academic hospital. All patients received a multimodal, perioperative pain management regimen consisting of the intraoperative administration of 1,000 mg of intravenous (IV) acetaminophen and 30 mg of IV ketorolac, combined with the operating surgeon performing a 4- to 5-level, midaxillary, intercostal nerve block using liposomal bupivacaine. All patients were discharged with a prescription for acetaminophen with codeine, along with options for nonnarcotic alternatives as needed for pain. Results: We reviewed the data on 72 patients who underwent mastectomies: 11 (15.3%) bilateral and 61 (84.7%) unilateral. The average age was 57 years, and average body mass index was 30 kg/m2. The average length of stay of 4 to 6 hours was a marked reduction compared to a 23-hour observational period or an inpatient hospital stay. The average follow-up was 20.1 weeks. Five patients presented to the emergency department (ED) within the 30-day postoperative period, with 2 patients (2.8%) requiring readmission to the hospital for non-pain-related issues. The other 3 patients (4.2%) were evaluated for specific pain-related issues but did not require admission and were discharged home from the ED. Conclusion: Our data support outpatient same-day mastectomy incorporating a multimodal, perioperative pain management regimen as a safe and feasible treatment option. Potential additional benefits may include decreased oral opioid use and cost savings for the hospital.

Population-Based Health Utility Assessment of Migraine Headache Symptoms before and after Surgical Intervention.

BACKGROUND: Approximately 30 million Americans suffer from migraine headaches. The primary goals of this study are to (1) use Migraine-Specific Symptoms and Disability criteria and Migraine Headache Index to describe the symptomatic improvement following decompressive surgery for refractory migraines, and (2) use the average Migraine Headache Index preoperatively and postoperatively for health utility assessment from a healthy patient's perspective. METHODS: The Migraine-Specific Symptoms and Disability criteria and the Migraine Headache Index were used to characterize migraine symptoms in the authors' patient population before and after decompressive surgery. Healthy individuals were randomized to a scenario in which they assumed either the preoperative or postoperative average patient symptom profile described by the authors' migraine patients. Health utility assessments were used to quantify the evaluation of health states the authors' patients experienced before and after surgical migraine therapy. RESULTS: Twenty-five patients underwent surgery for migraine headaches. The Migraine-Specific Symptoms and Disability questionnaire showed a significant decrease in both frequency of headaches per month (p < 0.0001) and overall pain score (p = 0.007). The Migraine Headache Index demonstrated a statistically significant improvement (p = 0.03). Healthy individuals in the preoperative group had significantly lower utility scores compared with the postoperative group in all of the health utility assessments completed for migraine symptoms. CONCLUSION: This is the first study to use health utility assessments to attest the efficacy of decompressive therapy by demonstrating the population perspective, which perceived a significant improvement in quality of life following the surgical treatment of migraines in the authors' patients. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Can It Be Safe and Aesthetic? An Eight-year Retrospective Review of Mastopexy with Concurrent Breast Augmentation.

BACKGROUND: The safety of concurrently performing mastopexy and breast augmentation is controversial, due to the risk of breast tissue and nipple neurovascular compromise and overall potential high complications rates. This article describes a concurrent procedure of augmentation with implants and a "Tailor-Tack" mastopexy that consistently achieves an aesthetically pleasing breast with acceptable complication rates. METHODS: This is a retrospective chart review of all consecutive breast augmentations performed concurrently with mastopexy using the "Tailor-Tack" technique by the 2 senior authors (M.M. and O.T.) over an 8-year period. Independent variables were patient demographics, surgical approach, implant type, shape, size, duration of follow-up, and complications. Complications were categorized as "early" (ie, first 30 days) or "late" (ie, after 30 days). Potential early complications include hematoma, skin necrosis, infection, and nipple loss. Potential late complications include recurrent breast ptosis, poor shape of the nipple areolar complex, hypertrophic scarring, implant rupture, capsular contracture, decreased nipple sensation, implant extrusion, reoperation, and scar revisions. The key principle of the technique is to place the breast implant in the dual plane first, and then perform the tailor tacking of the skin for the mastopexy second. RESULTS: Fifty-six consecutive patients underwent augmentation and mastopexy over 8 years with this technique. The average age of the studied patients was 41.2 years. The average follow-up time period was 2.1 years (±8.9 months). Fifty-four patients (96.4%) had implants placed through the periareolar approach, 2 patients (3.6%) had implants placed via the inframammary approach. All implants were placed in a dual plane. Fifty-two patients (92.9%) received silicone implants and 4 patients (7.1%) received saline implants. Patient preference determined implant choice. All but 5 patients had textured implants. Average implant size was 277 cm3 (range 120-800 cm3). Ten patients had complications (17.9%). Complications included hypertrophic scarring in 5 (8.9%) patients; poor nipple-areola complex shape in 4 patients (7.1%); implant ruptures in 3 patients (5.4%); capsular contracture in 3 patients (5.4%); and recurrent ptosis in 2 patients (3.6%). There were no reported early complications such as nipple loss, breast skin necrosis, decreased nipple sensation, implant infections, or extrusions. However, 6 patients (10.7%) required return trips to the operating room for revisions, and 1 patient (1.8%) had a nipple areolar complex scar revised in the office, yielding a 12.5% surgical revision rate for the late complications. CONCLUSIONS: It is safe to concurrently perform mastopexy and breast augmentation. In our 8-year review, there were no early catastrophic complications such as skin loss, nipple loss, implant extrusion, or infection. The complications that occurred were the same complications known to occur with the independent performance of mastopexy alone or breast augmentation alone, and they occurred at rates comparable to or less than the national averages for those procedures when they are performed independently. The paramount principle for the success of this technique is to first adjust breast volume and then perform an intraoperatively determined skin resection to fit the new breast volume.

American Society of Plastic Surgeons Member Post-Operative Opioid Prescribing Patterns.

INTRODUCTION: Despite the widespread use of opioids in pain management, there are currently no evidence-based guidelines for the treatment of postoperative pain with opioids. Although other surgical specialties have begun researching their pain prescribing patterns, there has yet to be an investigation to unravel opioid prescribing patterns among plastic surgeons. METHODS: Survey Monkey was used to sample the American Society of Plastic Surgeons (ASPS) members regarding their opioid prescribing practice patterns. The survey was sent randomly to 50% of ASPS members. Respondents were randomized to 1 of 3 different common elective procedures in plastic surgery: breast augmentation, breast reduction, and abdominoplasty. RESULTS: Of the 5,770 overall active ASPS members, 298 responses (12% response rate) were received with the following procedure randomization results: 106 for breast augmentation, 99 for breast reduction, and 95 for abdominoplasty. Overall, 80% (N = 240) of respondents used nonnarcotic adjuncts to manage postoperative pain, with 75.4% (N = 181) using nonnarcotics adjuncts >75% of the time. The most commonly prescribed narcotics were Hydrocodone with Acetaminophen (Lortab, Norco) and Oxycodone with Acetaminophen (Percocet, Oxycocet) at 42.5% (N = 116) and 38.1% (N = 104), respectively. The most common dosage was 5 mg (80.4%; N = 176), with 48.9% (N = 107) mostly dispensing 20-30 tablets, and the majority did not give refills (94.5%; N = 207). CONCLUSIONS: Overall, plastic surgeons seem to be in compliance with proposed American College of Surgeon's opioid prescription guidelines. However, there remains a lack of evidence regarding appropriate opioid prescribing patterns for plastic surgeons.

Mosaic Fleur-de-Profunda Artery Perforator Flap for Autologous Breast Reconstruction.

Perforator-free flaps, in autologous breast reconstruction, have expanded to exploit tissue available at smaller donor sites while retaining high success and low risk rates. Abdominal based flaps, such as the deep inferior epigastric perforator, remain the most common; however, when the abdomen is not an appropriate donor site, lower extremity flaps are options. The profunda artery perforator has the benefit of hiding unsightly scar in the gluteal crease but has the drawback of poor donor site volume. Our mosaic fleur-de-profunda artery perforator flap technique for breast reconstruction has shown to increase volume with the addition of a vertical limb, include full angiosome of perforators, and exhibit donor site morbidity equivalent to a medial thigh lift.

Stacked Lateral Thigh Perforator Flap as a Novel Option for Autologous Breast Reconstruction.

BACKGROUND: Autologous breast reconstruction using perforator flaps offers excellent outcomes, minimizes donor-site morbidity, and allows for precise donor-site selection. The deep inferior epigastric artery perforator, profunda artery perforator, and gluteal artery perforator flaps along with the stacked flap technique are the most common options. This study reports the first series of the stacked lateral thigh perforator flap. METHODS: A retrospective review of all stacked lateral thigh perforator flaps done by a single group of surgeons was performed. Demographics, flap weights, complications, indications, and surgical technique were tabulated for each patient. RESULTS: Eight female patients with a history of breast cancer underwent delayed unilateral breast reconstruction with stacked lateral thigh perforator flaps for a total of 16 flaps. Mean patient age, body mass index, flap weight, and stacked flap weight were 47.3 years, 26.2 kg/m, 333.1 g, and 666.1 g, respectively. Microsurgical revascularization was completed in anterograde and retrograde fashion to the internal mammary vasculature. Flap survival was 100 percent and one subsequent flap revision was performed. Two patients developed a seroma at the donor site. Indications included insufficient abdominal tissue, prominent lateral thigh lipodystrophy, prior abdominal surgery, and failed prior abdominally based autologous reconstruction. CONCLUSIONS: This series demonstrates that the lateral thigh perforator flap is a reliable and effective option for a stacked breast reconstruction. Its ease of harvest (stemming from reliable anatomy), straightforward dissection, and intraoperative positioning make it an appealing flap option. The stacked lateral thigh perforator flap allows the reconstructive surgeon to tailor breast reconstruction to the patient, focusing on body habitus and minimizing morbidity. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Assessing Age as a Risk Factor for Complications in Autologous Breast Reconstruction.

BACKGROUND: Breast cancer is primarily a diagnosis of older women. Many patients seeking breast reconstruction are elderly women (aged 65 years or older). However, many surgeons anecdotally believe that surgery in elderly patients is inherently dangerous, or at least prone to more complications. METHODS: The authors conducted a retrospective cohort study composed of chart review of all deep inferior epigastric perforator flap breast reconstruction patients at a single institution divided into an elderly cohort (65 years or older) and a nonelderly cohort (younger than 65 years). Cohort was the primary predictor variable. Demographic and comorbidity data were secondary predictor variables. Primary outcomes were complete flap loss, partial flap loss, or need for flap reexploration. Secondary outcomes such as wound healing problems, seroma, and others were also assessed. RESULTS: There were 285 flaps in the nonelderly cohort and 54 flaps in the elderly cohort. The elderly cohort had higher rates of diabetes, hypertension, and hyperlipidemia. Chi-square analysis showed no significant differences in primary outcomes between the two cohorts. Breast wound dehiscence was significantly higher in the elderly cohort (p < 0.01). On logistic regression, being elderly was seen as a significant risk factor for complete flap loss (OR, 10.92; 95 percent CI, 0.97 to 122.67; p = 0.05). The overall success rate for the nonelderly cohort was 99.6 percent, whereas the success rate for the nonelderly cohort was 96.3 percent. CONCLUSIONS: Elderly women desire breast reconstruction. Free flap breast reconstruction is a viable and safe procedure in these patients. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, II.

Cosmetic Surgeon Representation: Ensuring Board Certification Transparency and Patient Awareness.

BACKGROUND: Previous studies revealed that patients preferred plastic surgeons over cosmetic surgeons for surgical procedures, but few knew that any physician with a medical degree was legally qualified to perform cosmetic surgery. Results also indicated that a primary consideration for patients in selecting a surgeon was board certification. Although patient preferences concerning aesthetic surgery have previously been surveyed, no study examined a consumer's ability delineate between specialties based on Web sites. The purpose of this study was to investigate the responses of medical students to questions regarding a cosmetic and plastic surgeon's board certification. METHODS: A total of 4 cosmetic and 5 plastic surgeon Web sites were selected, in a single large city, from a Google search for the following procedures: liposuction, breast augmentation, blepharoplasty, rhytidectomy, and abdominoplasty. Screenshots of the Google search link, the page after clicking on the link, and the about the doctor page were collected to simulate an actual patient search experience. Four randomized surveys were created using screenshots and scenarios through Survey Monkey. Surveys were distributed and collected anonymously. Data analysis was accomplished using a chi-square test of independence (P < 0.05). RESULTS: A total of 474 medical students responded, and the difference between cosmetic and plastic surgeon variables was significant (P < 0.001). Upon comparison of different procedures, the cosmetic and plastic groups were found to be statistically different (P < 0.05), with some exceptions. On average, when presented with a plastic surgeon, 95.3% thought this was a board-certified plastic surgeon. When presented with a cosmetic surgeon, 54.3% also thought this was a board-certified plastic surgeon. The decline in responses regarding board certification, for the first and second cosmetic surgeons presented, was found to be statistically different (P < 0.0001). CONCLUSIONS: Over 50% of medical students had difficulty distinguishing between a cosmetic and plastic surgeon based on Web site advertisements; therefore, patients may have a more difficult experience. Results of this study prove the need for a universal definition, and patient education, relating to board certifications.

Blockade of IgM-Mediated Inflammation Alters Wound Progression in a Swine Model of Partial-Thickness Burn.

In a mouse model, a second-degree burn elicits a severe inflammatory response that is mediated by circulating autoantibody specific for a neoantigen (nonmuscle myosin). Nonmuscle myosin is expressed by injured tissue, leading to amplified ulceration and scarring. We hypothesize that a synthetic peptide (N2) can mimic the neoantigen and competitively inhibit the autoantibody, decreasing inflammation, and reducing the extent of burn injury in a preclinical swine model of burn. Second-degree burns were created on young swine using brass cylinders, warmed to varying temperatures before skin contact. Animals were treated in double-blind fashion with normal saline, control peptide, or blocking peptide. Biopsies were taken at 2 hours, 1, 4, 7, and 14 days after burn injury. Burn wound healing parameters were assessed. Immunohistochemical staining for Ki-67, immunoglobulin (Ig)M, and interleukin (IL)-8 were also performed. N2 blocking peptide administration decreased dermal injury at 4 days with increased reepithelization, indicating more rapid healing. N2 normalized skin histology by 14 days and showed improved epidermal healing. Granulation tissue thickness was decreased, and there was an accompanying decrease in neutrophil infiltration. The basal layer of epidermis in N2-treated animals displayed more cells positive for Ki-67, suggesting a prompter regenerative capacity. Immunohistochemical staining demonstrated decreased deposition of immunoglobulin M and interleukin-8 after thermal injury in animals treated with N2 peptide, in comparison to controls. The findings of this study identify N2 blocking a specific inflammatory pathway, as a novel therapeutic approach, preventing the evolution of cutaneous burn injuries in a preclinical animal model.

"Idealized" vs. "True" learning curves: the case of laparoscopic liver resection.

BACKGROUND: Learning curves are believed to resemble an "idealized" model, in which continuous improvement occurs until a plateau is reached. We hypothesized that this "idealized" model would not adequately describe the learning process for a complex surgical technique, specifically laparoscopic liver resection (LLR). METHODS: We analyzed the first 150 LLRs performed by a surgeon with expertise in hepatobiliary/laparoscopic surgery but with no previous LLR experience. We divided the procedures performed in 5 consecutive groups of 30 procedures, then compared groups in terms of complications, operative time, length of stay, and estimated blood loss. RESULTS: We observed an increase in operative complexity (3.3% major operations in Group 1 vs. 23.3% in Group 5, p = 0.05). Complications decreased from Group 1 to Group 2 (20%-3%), but increased again as more complex procedures were performed (3% in Group 2-13% in Group 5). Similar improvement/regression patterns were observed for operative time and EBL. DISCUSSION: The "true" learning curve for LLR is more appropriately described as alternating periods of improvement and regression until mastery is achieved. Surgeons should understand the true learning curves of procedures they perform, recognizing and mitigating the increased risk they assume by taking on more complex procedures.

Expanding the Applications of the Profunda Artery Perforator Flap.

BACKGROUND: The profunda artery perforator free flap has not gained traction for nonbreast reconstruction, likely because of the presence of a proven workhorse in the anterolateral thigh flap. The authors believe that the profunda artery perforator flap offers similar coverage characteristics with the benefits of a medial donor site, a more consistent anatomy, and relatively easy dissection. The authors review their indications, technique, and outcomes in seven patients requiring eight free flap reconstructions. METHODS: The authors applied the use of the vertically oriented profunda artery perforator flap to both lower extremity and head and neck reconstructions in which an anterolateral thigh flap would normally have been used. Details reviewed include soft-tissue defect, perforator location, flap size, recipient vessel, and complications. RESULTS: Eight soft-tissue defects were covered with a vertically oriented profunda artery perforator flap in seven patients. Six reconstructions were for distal lower extremity and two were for head and neck reconstruction, both trauma and oncologic reconstructions. Flap sizes ranged from 40 to 92 cm. The pedicle length ranged from 7 to 10 cm. There were no partial or complete flap losses. One complication of seroma at the donor site requiring washout and closure was encountered. CONCLUSIONS: The profunda artery perforator flap is a safe and effective option for perforator-based free flap reconstruction with relative ease of harvest and an inconspicuous donor site. This flap offers an excellent alternative to the anterolateral thigh flap. In certain patient demographics, the profunda artery perforator flap should be considered as a primary option. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.

Immunomodulatory Strategies Directed Toward Tolerance of Vascularized Composite Allografts.

BACKGROUND: Achieving tolerance of vascularized composite allografts (VCAs) would improve the risk-to-benefit ratio in patients who undergo this life-enhancing, though not lifesaving, transplant. Kidney cotransplantation along with a short course of high-dose immunosuppression enables tolerance of heart allografts across a full major histocompatibility complex (MHC) mismatch. In this study, we investigated whether tolerance of VCAs across full MHC disparities could be achieved in animals already tolerant of heart and kidney allografts. METHODS: Miniature swine that were tolerant of heart and/or kidney allografts long term underwent transplantation of myocutaneous VCA across the same MHC barrier. Before VCA transplant, group 1 (n = 3) underwent class I-mismatched kidney transplantation; group 2 (n = 3) underwent 2 sequential class I-mismatched kidney transplantations; group 3 (n = 2) underwent haploidentical MHC-mismatched heart/kidney transplantation; and group 4 (n = 2) underwent full MHC-mismatched heart/kidney transplantation. RESULTS: All 3 animals in group 1 and 2 of 3 animals in group 2 showed skin rejection within 85 days; 1 animal in group 2 showed prolonged skin survival longer than 200 days. Animals in groups 3 and 4 showed skin rejection within 30 days and regained in vitro evidence of donor responsiveness. CONCLUSIONS: This is the first preclinical study in which hearts, kidneys, and VCAs have been transplanted into the same recipient. Despite VCA rejection, tolerance of heart and kidney allografts was maintained. These results suggest that regulatory tolerance of skin is possible but not generally achieved by the same level of immunomodulation that is capable of inducing tolerance of heart and kidney allografts. Achieving tolerance of skin may require additional immunomodulatory therapies.

Genetically modified porcine split-thickness skin grafts as an alternative to allograft for provision of temporary wound coverage: preliminary characterization.

Temporary coverage of severely burned patients with cadaver allograft skin represents an important component of burn care, but is limited by availability and cost. Porcine skin shares many physical properties with human skin, but is susceptible to hyperacute rejection due to preformed antibodies to α-1,3-galactose (Gal), a carbohydrate on all porcine cells. Our preliminary studies have suggested that skin grafts from α-1,3-galactosyltransferase knock out (GalT-KO) miniature swine might provide temporary wound coverage comparable to allografts, since GalT-KO swine lack this carbohydrate. To further evaluate this possibility, eight non-human primates received primary autologous, allogeneic, GalT-KO, and GalT+xenogeneic skin grafts. Additionally, secondary grafts were placed to assess whether sensitization would affect the rejection time course of identical-type grafts. We demonstrate that both GalT-KO xenografts and allografts provide temporary coverage of partial- and full-thickness wounds for up to 11 days. In contrast, GalT+xenografts displayed hyperacute rejection, with no signs of vascularization and rapid avulsion from wounds. Furthermore, secondary GalT-KO transplants failed to vascularize, demonstrating that primary graft rejection sensitizes the recipient. We conclude that GalT-KO xenografts may provide temporary coverage of wounds for a duration equivalent to allografts, and thus, could serve as a readily available alternative treatment of severe burns.

The rejuvenating effects of leuprolide acetate on the aged baboon's thymus.

BACKGROUND: We have previously demonstrated that the juvenile thymus plays an essential role in tolerance induced by both renal transplantation and a short course of calcineurin inhibitors. Aged thymi have a decreased ability to induce tolerance. Luteinizing hormone-releasing hormone (LHRH) is known to pharmacologically rejuvenate the thymus in rodents. In order to develop a clinically applicable regimen of transplantation tolerance in adults, we sought to determine if thymic rejuvenation would occur with LHRH agonism in non-human primates. METHODS AND RESULTS: Thymic rejuvenation was evaluated by magnetic resonance imaging (MRI), histology, as well as in-vitro cellular and molecular tests. Four aged male hamadryas baboons underwent subcutaneous injection of a 3-month depot of Lupron (11.25mg; LI) and were followed for 3 months. Thymi increased volumetrically by MRI. After LI, thymic cellularity markedly increased within the cortical and medullary thymus. Additionally, a significant increase in the CD4(+)/CD45RA(hi+) population in the peripheral blood occurred for 50 days after LI, and flow cytometry of thymic tissue revealed a large increase in the percentage of CD4(+)/CD8(+) cells. TREC assay corroborated enhancement in thymic function. CONCLUSION: These data indicate that LI is associated with thymic rejuvenation in baboons, and further confirm that extrinsic factors play an important role in thymic rejuvenation in a non-human primate model.

Rituximab treatment prevents the early development of proteinuria following pig-to-baboon xeno-kidney transplantation.

We previously reported life-supporting α1,3-galactosyltransferase knockout (GalTKO) thymokidney xenograft survival of >2 months in baboons. However, despite otherwise normal renal function, recipients developed proteinuria with morphologic changes (podocyte effacement), a condition that presents a major obstacle to long-term studies in this model. A recent clinical study showed that rituximab therapy after allogeneic transplant prevented proteinuria possibly associated with loss of sphingomyelin phosphodiesterase acid-like 3b (SMPDL-3b). Here, we demonstrate that rituximab prevents the disruption of pig podocytes in an SMPDL-3b-dependent manner in vitro and the early development of proteinuria after xenogeneic kidney transplantation in baboons. Immunofluorescence showed SMPDL-3b expression in pig glomerular epithelium; immunoprecipitation demonstrated rituximab binding to SMPDL-3b in glomeruli. Culture of isolated pig podocytes with naive baboon sera, which has preformed antipig natural antibodies, reduced SMPDL-3b expression, disrupted podocyte morphology, and decreased podocyte proliferation, whereas pretreatment with rituximab prevented these effects. Six baboons received rituximab before transplantation to deplete B cells and again in the peri-transplant period; 18 baboons treated only before transplantation served as historical controls. The onset of post-transplant proteinuria was significantly delayed in a B cell-independent manner in the animals that received peri-transplant rituximab treatment. Although further optimization of this protocol is required, these data provide intriguing clues to the mechanisms of post-transplant proteinuria in xenogeneic kidney transplantation and a potential strategy for its prevention.

Vascularized composite allograft transplant survival in miniature swine: is MHC tolerance sufficient for acceptance of epidermis?

BACKGROUND: We have previously reported that Massachusetts General Hospital miniature swine, which had accepted class I-mismatched kidneys long-term after 12 days of high-dose cyclosporine A, uniformly accepted donor-major histocompatibility complex (MHC)-matched kidneys without immunosuppression but rejected donor MHC-matched split-thickness skin grafts by day 25, without changes in renal graft function or antidonor in vitro responses. We have now tested whether this "split tolerance" would also be observed for the primarily vascularized skin of vascularized composite allografts (VCAs). METHODS: Group 1 animals (n=3) received donor MHC-matched VCAs less than 70 days after primary kidney transplant (KTx). Group 2 animals (n=3) received a second donor-matched kidney transplant followed by a donor-matched VCA more than 200 days after primary KTx. RESULTS: Animals in Group 1 lost the epidermis on days 28, 30, and 40, with all other components of the VCAs remaining viable. Histology showed cellular infiltration localized to dermal-epidermal junction. One of three recipients of VCAs in Group 2, accepted all components of the VCA, including epidermis (>200 days). The other two recipients lost only the epidermis on days 45 and 85, with survival of the remainder of the VCA long-term. CONCLUSIONS: All tissues of a VCA are accepted long-term on animals tolerant of class I-mismatched kidneys, with the exception of epidermis, the survival of which is markedly prolonged compared with split-thickness skin grafts but not indefinite. Exposure of tolerant animals to second donor-matched kidneys before VCA increases the longevity of the VCA epidermis, suggesting an increase in the immunomodulatory mechanisms associated with tolerance of the kidney.

The gracilis myocutaneous free flap in swine: an advantageous preclinical model for vascularized composite allograft transplantation research.

Vascularized composite allotransplantation (VCA) has become a clinical reality, prompting research aimed at improving the risk-benefit ratio of such transplants. Here, we report our experience with a gracilis myocutaneous free flap in Massachusetts General Hospital miniature swine as a preclinical VCA model. Fourteen animals underwent free transfer of a gracilis myocutaneous flap comprised of the gracilis muscle and overlying skin, each tissue supplied by independent branches of the femoral vessels. End-to-end anastomoses were performed to the common carotid artery and internal jugular vein, or to the femoral vessels of the recipients. Thirteen of fourteen flaps were successful. A single flap was lost due to compromise of venous outflow. This model allows transplantation of a substantial volume of skin, subcutaneous tissue, and muscle. The anatomy is reliable and easily identified and harvest incurs minimal donor morbidity. We find this gracilis myocutaneous flap an excellent pre-clinical model for the study of vascularized composite allotransplantation.