Muscle is a target for preservation in a rat limb replantation model

Proof of Concept Study for a Closed Ex-Vivo Limb Perfusion System for 24-hour Subnormothermic Preservation Using Acellular Perfusate

BACKGROUND

The two approaches to vascularized tissue machine perfusion utilize either the open (non-pressurized) or closed (pressurized) perfusion system. Most studies describing isolated limb perfusion preservation rely on open perfusion systems and report tissue edema exceeding 40% after 12-14 hours of preservation.A variant of machine perfusion places the limb and perfusate into a reservoir closed to atmosphere. It is hypothesized that the reservoir pressure, acting as a transmural pressure, has the advantage of reducing edema formation by counteracting the hydrostatic pressure gradient from the perfusion pressure.This proof-of-concept study aim was to demonstrate feasibility of the ULiSSESTM device (closed, vertical perfusion system) to preserve forelimbs of Sus Scrofa swine for 24 hours of subnormothermic perfusion compared to an open, horizontal perfusion system. The ULiSSES™ is a compact, practical device that applies pulsatile, pressurized perfusion through the novel use of a diaphragm pump powered by compressed oxygen.

METHODS

Forelimbs from swine were preserved in ULiSSES™ device (closed perfusion system) (n = 9) and in an open perfusion system (n = 4) using sub-normothermic modified Krebs-Henseleit Solution. Physiological parameters were measured at the start and every 3 hours for 24 hours. Limbs were weighed prior to and post perfusion to compare weight gain. Edema and cellular integrity were evaluated using histopathology pre and post perfusion.

RESULTS

Closed perfusion system showed superiority compared to the open perfusion system in terms of oxygen consumption, reduction in vascular resistance, and overall tissue integrity. The closed perfusion system demonstrated a 21% reduction in weight gain compared to the open perfusion system and significantly reduced intracellular edema.

CONCLUSION

The ULiSSES™ closed, pressurized perfusion technology has translatable military applications with the potential to preserve porcine limbs for 24 hours with improved results compared to an open perfusion system.

LEVEL OF EVIDENCE

N/A.

Bionic Prostheses: The Emerging Alternative to Vascularised Composite Allotransplantation of the Limb

Twenty years have surpassed since the first vascularised composite allotransplantation (VCA) of the upper limb. This is an opportunity to reflect on the position of VCA as the gold standard in limb reconstruction. The paucity of recipients, tentative clinical outcomes, and insufficient scientific progress question whether VCA will remain a viable treatment option for the growing numbers of amputees. Bionic technology is advancing at a rapid pace. The prospect of widely available, affordable, safely applied prostheses with long-standing functional benefit is appealing. Progress in the field stems from the contributions made by engineering, electronic, computing and material science research groups. This review will address the ongoing reservations surrounding VCA whilst acknowledging the future impact of bionic technology as a realistic alternative for limb reconstruction.

The Efficacy of Salvage Intervention with Emergency Transient External Arterial Bypass for Traumatic Artery Occlusion of Main Extremities

Even if the vascular repair is successful, the frequency of limb loss is still high when popliteal artery injury is associated with postischemic syndrome due to blunt trauma or a prolonged ischemic time. Because prolonged ischemia interferes with an injured foot rescue, shortening of the ischemic time is a major aim of surgeons. We present two types of transient external arterial bypass and two cases of ischemic extremities due to main arterial injury. Even though the injured extremities had no circulation for more than 6 h, a transient external arterial bypass supplied circulation immediately, and they were reconstructed successfully. Although transient external arterial bypass is a dated technique, it is a recommended option, especially in the management of acute traumatic ischemia of the extremities to shorten the ischemic time and provide immediate reperfusion, which will bring the opportunity to save the ischemic limbs.

Evaluation of Early Markers of Ischemia-reperfusion Injury and Preservation Solutions in a Modified Hindlimb Model of Vascularized Composite Allotransplantation

Background.

Ischemia-reperfusion injury plays an important role in vascularized composite allotransplantation (VCA). Currently, there is no ideal preservation solution for VCA. In this study, we investigated the effects of 4 different preservation solutions on different tissues within an allogeneic hindlimb rat model.

Methods.

Sprague Dawley rat hindlimbs were flushed and placed at 4°C for 6 h in heparinized saline, histidine-tryptophan-ketoglutarate, University of Wisconsin (UW), and Perfadex and heterotopically transplanted for ease of ambulation. Apoptosis, necrosis, and the extracellular matrix of the tissues within the allograft were analyzed 2 h posttransplantation using immunohistochemistry, terminal deoxynucleotidyl transferase 2'-deoxyuridine 5'-triphosphate nick-end labeling (TUNEL) assay, and enzyme-linked immunoassay.

Results.

Higher expression of cleaved caspase 3, a significant increase of high-mobility group box 1 and TUNEL-positive apoptotic cells were observed in the muscle and vessels preserved with heparinized saline compared with UW and Perfadex following reperfusion. Higher expression of TUNEL-positive apoptotic cells was observed in the skin at 12 h of ischemia and in the nerve following reperfusion with histidine-tryptophan-ketoglutarate as a preservation solution.

Conclusions.

Our data suggest that UW and Perfadex are preferred solutions in VCA. The vessels within the allografts appear to be very susceptible, with laminins and CD31 playing a role in ischemia-reperfusion injury.

Strategies to Reduce Ischemia Reperfusion Injury in Vascularized Composite Allotransplantation of the Limb

An important and often underinvestigated contributor to solid organ transplant rejection is ischemia reperfusion injury. This pathophysiological response releases damaging reactive oxygen species and cell stress signals that initiate inflammation, which has a critical role in priming the immune system for allorecognition. In time, this renders graft dysfunction and how this response is mediated in composite tissues remains unknown. Current protocols are drawn from solid organ transplantation with little scientific basis as to how this informs current hand transplantation practices. In addition to preservation flush and allograft cooling, machine perfusion is placing itself experimentally as a concept that could act to promote viability and increase the critical ischemic window, which is especially beneficial at a time of limited donors. With the increasing prevalence worldwide of hand transplantation, we review the potential contribution of ischemia reperfusion injury to hand allograft rejection including both current and experimental strategies.

Effect of Artificial Nerve Conduit Vascularization on Peripheral Nerve in a Necrotic Bed

BACKGROUND

Several types of artificial nerve conduit have been used for bridging peripheral nerve gaps as an alternative to autologous nerves. However, their efficacy in repairing nerve injuries accompanied by surrounding tissue damage remains unclear. We fabricated a novel nerve conduit vascularized by superficial inferior epigastric (SIE) vessels and evaluated whether it could promote axonal regeneration in a necrotic bed.

METHODS

A 15-mm nerve conduit was implanted beneath the SIE vessels in the groin of a rat to supply it with blood vessels 2 weeks before nerve reconstruction. We removed a 13-mm segment of the sciatic nerve and then pressed a heated iron against the dorsal thigh muscle to produce a burn. The defects were immediately repaired with an autograft (n = 10), nerve conduit graft (n = 8), or vascularized nerve conduit graft (n = 8). Recovery of motor function was examined for 18 weeks after surgery. The regenerated nerves were electrophysiologically and histologically evaluated.

RESULTS

The vascularity of the nerve conduit implanted beneath the SIE vessels was confirmed histologically 2 weeks after implantation. Between 14 and 18 weeks after surgery, motor function of the vascularized conduit group was significantly better than that of the nonvascularized conduit group. Electrophysiological and histological evaluations revealed that although the improvement did not reach the level of reinnervation achieved by an autograft, the vascularized nerve conduit improved axonal regeneration more than did the conduit alone.

CONCLUSION

Vascularization of artificial nerve conduits accelerated peripheral nerve regeneration, but further research is required to improve the quality of nerve regeneration.