Validated specialty-specific models for multi-disciplinary microsurgery training laboratories: a systematic review.

BACKGROUND: Laboratory simulation is increasingly important for teaching microsurgical skills. Training microsurgeons of different specialties within the same simulation laboratory increases efficiency of resource use. For maximal benefit, simulations should be available for trainees to practice specialty-specific, higher-order skills. Selection of appropriate simulations requires knowledge of the efficacy and validity of the numerous described laboratory models. Here we present a systematic review of validated training models that may serve as useful adjuncts to achieving competency in specialty elements of microsurgery, and appraise the evidence behind them. METHODS: In setting up a multi-disciplinary microsurgery training course, we performed a systematic review according to preferred reporting items for systematic reviews and meta-analyses guidelines. EMBASE, MEDLINE, Cochrane and PubMed databases were searched for studies describing validated, microscope-based, specialty-specific simulations, and awarded a level of evidence and level of recommendation based on a modified Oxford Centre for Evidence-Based Medicine classification. RESULTS: A total of 141 papers describing specialty-specific microsimulation models were identified, 49 of which included evidence of validation. Eleven were in the field of neurosurgery, 21 in otolaryngology/head and neck surgery, two in urology/gynaecology and 15 plastic and reconstructive surgery. These papers described synthetic models in 19 cases, cadaveric animals in 10 cases, live animals in 12 cases and human cadaveric material in 10 cases. CONCLUSION: Numerous specialty-specific models for use in the microscope laboratory are available, but the quality of evidence for them is poor. Provision of models that span numerous specialties may encourage use of a microscope lab whilst still enabling more specific skills training over a 'one-size-fits-all' approach.

Direct recognition of hepatocyte-expressed MHC class I alloantigens is required for tolerance induction.

Adeno-associated viral vector-mediated (AAV-mediated) expression of allogeneic major histocompatibility complex class I (MHC class I) in recipient liver induces donor-specific tolerance in mouse skin transplant models in which a class I allele (H-2Kb or H-2Kd) is mismatched between donor and recipient. Tolerance can be induced in mice primed by prior rejection of a donor-strain skin graft, as well as in naive recipients. Allogeneic MHC class I may be recognized by recipient T cells as an intact molecule (direct recognition) or may be processed and presented as an allogeneic peptide in the context of self-MHC (indirect recognition). The relative contributions of direct and indirect allorecognition to tolerance induction in this setting are unknown. Using hepatocyte-specific AAV vectors encoding WT allogeneic MHC class I molecules, or class I molecules containing a point mutation (D227K) that impedes direct recognition of intact allogeneic MHC class I by CD8+ T cells without hampering the presentation of processed peptides derived from allogeneic MHC class I, we show here that tolerance induction depends upon recognition of intact MHC class I. Indirect recognition alone yielded a modest prolongation of subsequent skin graft survival, attributable to the generation of CD4+ Tregs, but it was not sufficient to induce tolerance.

A modified method for heterotopic mouse heart transplantion.

Mice are often used as heart transplant donors and recipients in studies of transplant immunology due to the wide range of transgenic mice and reagents available. A difficulty is presented due to the small size of the animal and the considerable technical challenges of the microsurgery involved in heart transplantation. In particular, a high rate of technical failure early after transplantation may result from recipient death and post-operative complications such as hind limb paralysis or a non-beating heart. Here, the complete technique for heterotopic mouse heart transplantation is demonstrated, involving harvesting the donor heart and its subsequent implantation into a recipient mouse. The donor heart is harvested immediately following in situ perfusion with cold heparinized saline and transection of the ascending aorta and pulmonary artery. The recipient operation involves preparation of the abdominal aorta and inferior vena cava (IVC), followed by end-to-side anastomosis of the donor aorta with the recipient aorta using a single running 10-0 microsuture and a similar anastomosis of the donor pulmonary artery with the recipient IVC. Following the operation the animal is injected with 0.6 ml normal saline subcutaneously and allowed to recover on a 37 ° C heating pad. The results from 227 mouse heart transplants are summarized with a success rate at 48 hr of 86.8%. Of the 13.2% failures within 48 hr, 5 (2.2%) experienced hind limb paralysis, 10 (4.4%) had a non-beating heart due to graft ischemic injury and/or thrombosis, while 15 (6.6%) died within 48 hr.

Optimized method for ureteric reconstruction in a mouse kidney transplant model.

BACKGROUND: Murine kidney transplantation is an important model for studies of transplantation immunobiology. The most challenging aspect of the difficult surgical procedure is the ureteric anastomosis. METHODS: Two different approaches to ureteric reconstruction are compared here. Method 1, Patch: this involves anastomosis of the donor ureter together with a patch of donor bladder to recipient bladder. Method 2, Implant: this utilizes a 5-0 suture to pull the ureter through the bladder wall. The ureter's peripheral tissue is then fixed to the bladder wall at the implant site with 10-0 micro-sutures. RESULTS: In animals transplanted with the patch method, the initial success rate, defined as survival up to the third post-operative day, was 79% (n = 62), whereas the initial success rate for the implant method was 86.1% (n = 101; P = 0.28). The death rate from unknown and/or unspecified causes in the initial period was 16.1% (10/62) for the patch method, and 8.9% (9/101) for the implant method (P = 0.21). The average donor/recipient operation time with the implant method was 14.8 ± 2.2/61.4 ± 4.7 min (76 min per transplant), whereas operation time with the patch method was 28.3 ± 2.4/77.8 ± 5.5 min (106 min per transplant; P < 0.001). The ureteric implant method resulted in a lower rate of urinary leak compared with the patch method (1.1% versus 10.2%; P = 0.02). CONCLUSIONS: The ureteric implant method for mouse kidney transplantation is a reliable approach with at least as high a success rate as the bladder patch method and with a shorter operation time.

Gene therapy for tolerance: high-level expression of donor major histocompatibility complex in the liver overcomes naive and memory alloresponses to skin grafts.

BACKGROUND: The liver has long been recognized as having tolerogenic properties. We investigated whether recombinant adenoassociated virus (rAAV)-mediated expression of donor major histocompatibility complex in recipient livers could induce tolerance to donor-strain grafts. METHODS: Naive B10.BR (H-2) or B10.BR recipients primed with a H-2K-expressing (K) skin graft were injected with rAAV-expressing H-2K (rAAV-K) to induce K expression on hepatocytes 7 days before challenge with a K skin graft. K-specific responses were measured by interferon (IFN)-γ ELISpot and flow cytometric assessment of directly H-2K reactive cells. Fully allogeneic grafts from C57BL/6 (H-2) donors were transplanted onto longstanding B10.BR recipients of K skin to test for linked epitope suppression. RESULTS: rAAV-K-treated B10.BR mice accepted K skin grafts with increased median survival time (MST) more than 169 days compared to uninoculated (MST=18.5 days) and rAAV-K-treated controls (MST=19 days). rAAV-K-treated B10.BR animals primed with K skin grafts also accepted secondary K skin grafts in the long term (MST>100 days) compared to accelerated rejection in primed, uninoculated mice (MST=12 days). Treatments did not induce liver pathology, assessed by serum alanine aminotransferase levels and histology. IFN-γ ELISpot analysis of splenocytes from rAAV-K-treated mice indicated reduced responses to donor K antigen, but protection was not extended to fully allogeneic C57BL/6 skin or heart grafts, even in recipients that had accepted K skin grafts in the long term. CONCLUSIONS: High-level expression of donor major histocompatibility complex in recipient livers promotes tolerance to skin allografts, even in animals primed to produce a memory response. This provides proof of concept for an approach using liver-targeted gene delivery for tolerance induction to donor antigen.