Subzero nonfreezing preservation in a murine limb replantation model

Supercooling: A Promising Technique for Prolonged Organ Preservation in Solid Organ Transplantation, and Early Perspectives in Vascularized Composite Allografts

Ex-vivo preservation of transplanted organs is undergoing spectacular advances. Machine perfusion is now used in common practice for abdominal and thoracic organ transportation and preservation, and early results are in favor of substantially improved outcomes. It is based on decreasing ischemia-reperfusion phenomena by providing physiological or sub-physiological conditions until transplantation. Alternatively, supercooling techniques involving static preservation at negative temperatures while avoiding ice formation have shown encouraging results in solid organs. Here, the rationale is to decrease the organ's metabolism and need for oxygen and nutrients, allowing for extended preservation durations. The aim of this work is to review all advances of supercooling in transplantation, browsing the literature for each organ. A specific objective was also to study the initial evidence, the prospects, and potential applications of supercooling preservation in Vascularized Composite Allotransplantation (VCA). This complex entity needs a substantial effort to improve long-term outcomes, marked by chronic rejection. Improving preservation techniques is critical to ensure the favorable evolution of VCAs, and supercooling techniques could greatly participate in these advances.

Cryopreservation and replantation of amputated rat hind limbs

BACKGROUND

In spite of the relatively high success rate of limb replantation, many patients cannot undergo replantation surgery because the preservation time of an amputated limb is only about six hours. In addition, although allotransplantation of composite tissues is being performed more commonly with increasingly greater success rates, the shortage of donors limits the number of patients that can be treated. So the purpose of this study is to examine the feasibility of cryopreservation and replantation of limbs in a rat model.

METHODS

Twelve five-month-old Sprague-Dawley rats were divided evenly into group A (above-knee amputation) and group B (Syme's amputation). One hind limb was amputated from each rat. The limbs were irrigated with cryoprotectant, cooled in a controlled manner to -140°C, and placed in liquid nitrogen. Thawing and replantation were performed 14 days later.

RESULTS

In group A, the limbs became swollen after restoration of blood flow resulting in blood vessel compression and all replantations failed. In group B, restoration of blood flow was noted in all limbs after replantation. In one case, the rat chewed the replanted limb and replantation failed. The other five rats were followed for three months with no abnormalities noted in the replanted limbs.

CONCLUSIONS

Limbs with a minimal amount of muscle tissue can be successfully cryopreserved and replanted.

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

Supplemental Digital Content is available in the text.

Background:

Ischemia exceeding 6 hours makes clinical limb replantation difficult and places the patient at risk of functional deficit or limb loss. We investigated the preservation of muscle function and morphology with solutions in rat hindlimb in vivo and in vitro.

Methods:

Quadriceps femoris muscles from luciferase transgenic rats were preserved for 24 hours at 4°C in extracellular-type trehalose containing Kyoto (ETK), University of Wisconsin (UW), or lactated Ringer’s (LR) solution (control). Muscle luminescence was measured with a bioimaging system. Amputated limbs of Lewis rats preserved with ETK, UW, or LR for 6 or 24 hours at 4°C were transplanted orthotopically. At week 8, terminal latency and amplitude were measured in the tibialis anterior muscle. The muscles were also analyzed histologically.

Results:

Isolated muscles preserved in ETK or UW had significantly higher luminescence than did muscles immersed in LR (P < 0.05). In the 6-hour-preserved limb transplantation model, although the 3 groups had almost the same terminal latency, electrical amplitude was significantly lower in the LR group. Histologically, muscles preserved with LR showed the most atrophic changes. In the 24-hour-preserved model, the survival rate of the LR group was 37.5% in contrast to 80% in the ETK and UW groups. Electrical signals were not detected in the LR group owing to severe muscle atrophy and fibrosis. The ETK and UW groups showed good muscle function electrophysiologically.

Conclusions:

Preservation solutions can protect muscle function and morphology in ischemia–reperfusion limbs and improve recipient survival rates after transplantation of long-term-preserved limbs.

Bone viability of amputated limbs treated with hypothermia: assessment by evaluation of mRNA levels

We evaluated rat bone viability using a bone viability index (BVI). To evaluate hypothermic ischaemic bone injury, 21 amputated hind limbs of Fischer rats were preserved at hypothermia (4 degrees C) for 1, 3 and 6 hours. To evaluate hypothermic ischaemia/reperfusion injury, another 28 amputated limbs were transplanted to recipient rats after hypothermic ischaemia for 3 and 6 hours, respectively. Total RNA isolated from each tibia was fractionated by electrophoresis and hybridised with 32P-labelled cDNA of GAPDH, and the radioactivity of intact and degraded GAPDH mRNA measured. BVI was calculated as follows, BVI = [A / (A + B)] x 100, where A and B represent the radioactivities corresponding to intact and degraded GAPDH mRNA bands, respectively. In the hypothermic ischaemic insult group, BVIs were comparable to those of controls. However, in the 3-hour hypothermic ischaemia/reperfusion group, BVI was lower than that of the controls. Likewise, there was a significant difference between the 6-hour ischaemia/reperfusion group and controls. These results showed that bone viability decreased even after just a 3-hour hypothermic ischaemia/reperfusion.

Successful liquid storage of peripheral blood stem cells at subzero non-freezing temperature

Although non-frozen storage of peripheral blood stem cells (PBSC) has been extensively studied and utilized clinically, the optimal storage conditions have not been determined. In order to improve the maintenance of clonogenic capacity during storage, we evaluated the feasibility of subzero non-freezing preservation of PBSC and attempted to determine the optimal conditions. Human PBSC were stored in different non-cryopreserved conditions. University of Wisconsin (UW) solution was used as the storage medium for PBSC. The stem cell integrity was optimally maintained when PBSC were preserved in a supercooled state at -2 degrees C in UW solution without any cryoprotectants, and the highest values for nucleated cell survival (91.6%), CFU-GM survival (67.3%) and trypan blue viability (92%) were achieved at 72 h. CFU-GM survival in our storage conditions was significantly better than the survival achieved with hypothermic preservation in autologous serum and ACD-A solution at 4 degrees C (67.3 +/- 9.2% vs 42.9 +/- 15.3%; P < 0.01) or cryopreservation at -80 degrees C (67.3 +/- 9.2% vs 52.7 +/- 10.7%; P < 0.01). Thus, the combination of supercooling and UW solution was the optimal non-freezing method of preserving transplantable PBSC tested here. This method is of clinical utility in peripheral blood stem cell transplantation (PBSCT) for its simplicity and storage efficiency, and has value as a short-term storage method for PBSC to support dose-intensive multicyclic chemotherapy.

Viability of hypothermic preserved muscle determined by gene expression levels

We report a muscle viability index (MVI) that reflects mRNA degradation. The viability of hypothermically preserved (48C) rat skeletal muscle was evaluated using this MVI. To evaluate the hypothermic ischaemic insult of the muscle, 21 hind limbs of Fischer rats (three subgroups of seven limbs each) were hypothermically preserved for 1h, 3h and 6h, before harvesting the tibialis anterior muscle. To investigate reperfusion injury after hypothermic preservation, an additional 28 limbs were transplanted to recipient Fischer rats after hypothermic ischaemia for either 3h or 6h. The transplanted muscles were harvested on either day 3 or day 7 after transplantation. Seven fresh muscles were also harvested, and used as controls. In the 3h ischaemia group, the MVIs of both the hypothermic-ischaemia and the ischaemia-reperfusion subgroups were comparable to the controls. Likewise, there were no significant differences between the controls and the 6h hypothermic ischaemia and ischaemia-reperfusion subgroups. These results show that muscle viability is maintained with hypothermic preservation of up to 6h, and after reperfusion. Therefore, in clinical replantations the amputated extremity should be preserved under hypothermic conditions from the time of injury to the time of surgery.

Viability of ischemia/reperfused muscles in rat: a new evaluation method by RNA degradation

The rat's skeletal muscle viability was evaluated using the muscle viability index (MVI) which reflects the mRNA degradation. To evaluate ischemic injury of the muscle, 24 hind limbs of Fischer rats (three subgroups of eight rats each) were preserved at normothermia for 1, 3 and 6 h and then tibialis anterior muscle was harvested. To investigate ischemia/reperfusion injury, another 48 limbs were transplanted to recipient Fischer rats after the ischemia at normothermia for 1, 3 and 6 h, respectively. The transplanted muscles were harvested on day 3 and day 7 after transplantation. Eight fresh muscles were also harvested and used as control. Total RNA isolated from each muscle was fractionated by electrophoresis and hybridized with 32P-labelled cDNA of GAPDH, and the radioactivity of intact and degraded GAPDH mRNA was measured. MVI was calculated as follows, MVI = [X/(X + Y)] x 100, where X and Y represent the radioactivities corresponding to intact GAPDH and degraded GAPDH mRNA band, respectively. In 1-h ischemia group, the MVI indices of both ischemic insult and ischemia/reperfusion group were comparable to control. In the 3-h ischemia group, the index of ischemia/reperfused group was comparable to control although the index of ischemic insult group was significantly lower than control. However, in the 6-h ischemia group, both indices of ischemic insult and ischemia/reperfusion group were significantly lower than control. These results show that the muscle damage was detected in ischemia at normothermia even after 3 h. However, this damage was overcome by reperfusion. There was no recovery from damage in muscles that had been preserved for more than 6 h which had resulted in irreversible degeneration. Therefore, in clinical muscle transplantation, one has to transplant the muscle at least within 3-h ischemia.