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Background Photochemical tissue bonding (PTB) is a technique for peripheral nerve repair in which a collagenous membrane is bonded around approximated nerve ends. Studies using PTB with cryopreserved human amnion have shown promising results in a rat sciatic nerve transection model including a more rapid and complete return of function, larger axon size, and thicker myelination than suture repair. Commercial collagen membranes, such as dehydrated amnion allograft, are readily available, offer ease of storage, and have no risk of disease transmission or tissue rejection. However, the biomechanical properties of these membranes using PTB are currently unknown in comparison to PTB of cryopreserved human amnion and suture neurorrhaphy. Methods Rat sciatic nerves (n = 10 per group) were transected and repaired using either suture neurorrhaphy or PTB with one of the following membranes: cryopreserved human amnion, monolayer human amnion allograft (crosslinked and noncrosslinked), trilayer human amnion/chorion allograft (crosslinked and noncrosslinked), or swine submucosa. Repaired nerves were subjected to mechanical testing. Results During ultimate stress testing, the repair groups that withstood the greatest strain increases were suture neurorrhaphy (69 ± 14%), PTB with crosslinked trilayer amnion (52 ± 10%), and PTB with cryopreserved human amnion (46 ± 20%), although the differences between these groups were not statistically significant. Neurorrhaphy repairs had a maximum load (0.98 ± 0.30 N) significantly greater than all other repair groups except for noncrosslinked trilayer amnion (0.51 ± 0.27 N). During fatigue testing, all samples repaired with suture, or PTBs with either crosslinked or noncrosslinked trilayer amnion were able to withstand strain increases of at least 50%. Conclusion PTB repairs with commercial noncrosslinked amnion allograft membranes can withstand physiological strain and have comparable performance to repairs with human amnion, which has demonstrated efficacy in vivo. These results indicate the need for further testing of these membranes using in vivo animal model repairs. [ABSTRACT FROM AUTHOR]

Background For 50 years, static cold storage (SCS) has been the gold standard for solid organ preservation in transplantation. Although logistically convenient, this preservation method presents important constraints in terms of duration and cold ischemia-induced lesions. We aimed to develop a machine perfusion (MP) protocol for recovery of vascularized composite allografts (VCA) after static cold preservation and determine its effects in a rat limb transplantation model. Methods Partial hindlimbs were procured from Lewis rats and subjected to SCS in Histidine-Tryptophan-Ketoglutarate solution for 0, 12, 18, 24, and 48 hours. They were then either transplanted (Txp), subjected to subnormothermic machine perfusion (SNMP) for 3 hours with a modified Steen solution, or to SNMP + Txp. Perfusion parameters were assessed for blood gas and electrolytes measurement, and flow rate and arterial pressures were monitored continuously. Histology was assessed at the end of perfusion. For select SCS durations, graft survival and clinical outcomes after transplantation were compared between groups at 21 days. Results Transplantation of limbs preserved for 0, 12, 18, and 24-hour SCS resulted in similar survival rates at postoperative day 21. Grafts cold-stored for 48 hours presented delayed graft failure (p = 0.0032). SNMP of limbs after 12-hour SCS recovered the vascular resistance, potassium, and lactate levels to values similar to limbs that were not subjected to SCS. However, 18-hour SCS grafts developed significant edema during SNMP recovery. Transplantation of grafts that had undergone a mixed preservation method (12-hour SCS + SNMP + Txp) resulted in better clinical outcomes based on skin clinical scores at day 21 post-transplantation when compared to the SCS + Txp group (p = 0.01613). Conclusion To date, VCA MP is still limited to animal models and no protocols are yet developed for graft recovery. Our study suggests that ex vivo SNMP could help increase the preservation duration and limit cold ischemia-induced injury in VCA transplantation. [ABSTRACT FROM AUTHOR]