Knock-out of N-glycolylneuraminic acid attenuates antibody-mediated rejection in xenogenically perfused porcine lungs.

Antibody-mediated rejection has long been known to be one of the major organ failure mechanisms in xenotransplantation. In addition to the porcine α1,3-galactose (α1,3Gal) epitope, N-Glycolylneuraminic acid (Neu5Gc), a sialic acid, has been identified as an important porcine antigen against which most humans have pre-formed antibodies. Here we evaluate GalTKO.

Pig-to-baboon lung xenotransplantation: Extended survival with targeted genetic modifications and pharmacologic treatments.

Galactosyl transferase knock-out pig lungs fail rapidly in baboons. Based on previously identified lung xenograft injury mechanisms, additional expression of human complement and coagulation pathway regulatory proteins, anti-inflammatory enzymes and self-recognition receptors, and knock-down of the β4Gal xenoantigen were tested in various combinations. Transient life-supporting GalTKO.

An educated guess - Distance estimation by surgeons.

Introduction: Estimating distance is a common task in surgery, yet development of distance estimation ability receives little attention in surgical training. Although the Small bites versus large bites for closure of abdominal midline incisions (STITCH) trial reinforced the importance of suture spacing by demonstrating reduced incisional hernia incidence in placement of 5-mm fascial sutures over 1 cm, we hypothesize that neither trainee nor attending surgeons possess the ability to estimate these distances with accuracy.

Methods: We distributed a 4-question distance estimation exercise and a 6-question survey to resident and attending surgeons at a single academic medical center.

Postoperative small bowel obstruction secondary to single malformed staple following laparoscopic total abdominal colectomy.

Surgical staplers are ubiquitous in gastrointestinal surgery, especially laparoscopy. Intraperitoneal staples are designed to be inert and are generally regarded as benign; however, complications from primarily malformed staples can rarely occur. Here, we present a case of early mechanical postoperative small bowel obstruction due to a surgical staple following laparoscopic total abdominal colectomy and end ileostomy creation performed for medically refractory ulcerative colitis.

Vascularized Thymosternal Composite Tissue Allo- and Xenotransplantation in Nonhuman Primates: Initial Experience.

Background: Vascularized composite allotransplantation is constrained by complications associated with standard immunosuppressive strategies. Vascularized thymus and bone marrow have been shown to promote prolonged graft survival in composite organ and soft-tissue vascularized composite allotransplantation models. We report development of a nonhuman primate vascularized thymosternal composite tissue transplant model as a platform to address donor-specific immune tolerance induction strategies.

Pilot Study of Delayed ICOS/ICOS-L Blockade With αCD40 to Modulate Pathogenic Alloimmunity in a Primate Cardiac Allograft Model.

Background: Inducible costimulator (ICOS) is rapidly upregulated with T-cell stimulation and may represent an escape pathway for T-cell costimulation in the setting of CD40/CD154 costimulation blockade. Induction treatment exhibited no efficacy in a primate renal allograft model, but rodent transplant models suggest that the addition of delayed ICOS/ICOS-L blockade may prolong allograft survival and prevent chronic rejection. Here, we ask whether ICOS-Ig treatment, timed to anticipate ICOS upregulation, prolongs NHP cardiac allograft survival or attenuates pathogenic alloimmunity.

Selective CD28 Inhibition Modulates Alloimmunity and Cardiac Allograft Vasculopathy in Anti-CD154-Treated Monkeys.

Background: Selective CD28 inhibition is actively pursued as an alternative to B7 blockade using cytotoxic T lymphocyte antigen 4 Ig based on the hypothesis that the checkpoint immune regulators cytotoxic T lymphocyte antigen 4 and programmed death ligand 1 will induce tolerogenic immune signals. We previously showed that blocking CD28 using a monovalent nonactivating reagent (single-chain anti-CD28 Fv fragment linked to alpha-1 antitrypsin [sc28AT]) synergizes with calcineurin inhibitors in nonhuman primate (NHP) kidney and heart transplantation. Here, we explored the efficacy of combining a 3-week "induction" sc28AT treatment with prolonged CD154 blockade.

Harnessing the lymph node microenvironment.

Purpose Of Review: To evaluate role of the lymph node in immune regulation and tolerance in transplantation and recent advances in the delivery of antigen and immune modulatory signals to the lymph node.

Recent Findings: Lymph nodes are a primary site of immune cell priming, activation, and modulation, and changes within the lymph node microenvironment have the potential to induce specific regulation, suppression, and potentially tolerance. Antigen enters the lymph node either from tissues via lymphatics, from blood via high endothelial venules, or directly via injection.

Synthetic liver function is detectable in transgenic porcine livers perfused with human blood.

In addition to immune barriers, molecular incompatibilities between species are predicted to limit pig liver survival in primate xenotransplantation models. Assessment and measurement of synthetic function of genetically modified porcine livers after ex vivo perfusion with human blood have not previously been described. Eight porcine livers from α1,3-galactosyl transferase knockout and human membrane cofactor (GalTKO.

N-glycolylneuraminic acid knockout reduces erythrocyte sequestration and thromboxane elaboration in an ex vivo pig-to-human xenoperfusion model.

Background: Wild-type pigs express several carbohydrate moieties on their cell surfaces that differ from those expressed by humans. This difference in profile leads to pig tissue cell recognition of human blood cells causing sequestration, in addition to antibody-mediated xenograft injury. One such carbohydrate is N-glycolylneuraminic acid (Neu5Gc), a sialic acid molecule synthesized in pigs but not in humans.

Transgenic expression of human leukocyte antigen-E attenuates GalKO.hCD46 porcine lung xenograft injury.

Background: Lung xenografts remain susceptible to loss of vascular barrier function within hours in spite of significant incremental advances based on genetic engineering to remove the Gal 1,3-αGal antigen (GalTKO) and express human membrane cofactor protein (hCD46). Natural killer cells rapidly disappear from the blood during perfusion of GalTKO.hCD46 porcine lungs with human blood and presumably are sequestered within the lung vasculature.

The use of resuscitative endovascular balloon occlusion of the aorta to control hemorrhagic shock during video-assisted retroperitoneal debridement or infected necrotizing pancreatitis.

Introduction: Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a technique that has been shown to provide central vascular control to support proximal aortic pressure and minimize hemorrhage in a wide variety of clinic settings, however the role of REBOA for emergency general surgery is less defined.

Case Description: This is a report of a 44 year old man who experienced hemorrhagic shock during video-assisted retroperitoneal debridement (VARD) for necrotizing pancreatitis where REBOA was used to prevent ongoing hemorrhage and death.

Discussion: This is the first documented report REBOA being used during pancreatic debridement in the literature and one of the first times it has been used in emergency general surgery.