Radiation sterilization of tissue allografts:A review

Tissue substitutes are required in a number of clinical conditions for treatment of injured and diseased tissues.Tissues like bone,skin,amniotic membrane and soft tissues obtained from human donor can be used for repair or reconstruction of the injured part of the body.Allograft tissues from human donor provide an excellent alternative to autografts.However,major concern with the use of allografts is the risk of infectious disease transmission.Therefore,tissue allografts should be sterilized to make them safe for clinical use.Gamma radiation has several advantages and is the most suitable method for sterilization of biological tissues.This review summarizes the use of gamma irradiation technology as an effective method for sterilization of biological tissues and ensuring safety of tissue allografts.

Various changes in cryopreserved acellular nerve allografts at-80°C

The experimental design evaluated histological,mechanical,and biological properties of allogeneic decellularized nerves after cryopreservation in a multi-angle,multi-directional manner to provide evidence for long-term preservation.Acellular nerve allografts from human and rats were cryopreserved in a cryoprotectant（10% fetal bovine serum,10% dimethyl sulfoxide,and 5% sucrose in RPMI1640 medium） at-80°C for 1 year,followed by thawing at 40°C or 37°C for 8 minutes.The breaking force of acellular nerve allografts was measured using a tensile test.Cell survival was determined using L-929 cell suspensions.Acellular nerve allografts were transplanted into a rat model with loss of a 15-mm segment of the left sciatic nerve.Immunohistochemistry staining was used to measure neurofilament 200 expression.Hematoxylin-eosin staining was utilized to detect relative muscle area in gastrocnemius muscle.Electron microscopy was applied to observe changes in allograft ultrastructure.There was no obvious change in morphological appearance or ultrastructure,breaking force,or cytotoxicity of human acellular nerve allografts after cryopreservation at-80°C.Moreover,there was no remarkable change in neurofilament 200 expression,myelin sheath thickness,or muscle atrophy when fresh or cryopreserved rat acellular nerve allografts were applied to repair nerve injury in rats.These results suggest that cryopreservation can greatly extend the storage duration of acellular nerve tissue allografts without concomitant alteration of the physiochemical and biological properties of the engineered tissue to be used for transplantation.

Chronic ocular GVHD:limbal and conjunctival stem cell allografts from the same hematopoietic stem cell donor

Dear Editor,I am Dr.Elias F Jarade from the Beirut Eye and ENT Specialist Hospital, Beirut, Lebanon. I write to describe a novel surgical technique in the management of chronic ocular graft-versus-host disease（GVHD）.

Evaluation of the updated definition of early allograft dysfunction in donation after brain death and donation after cardiac death liver allografts

BACKGROUND:An updated definition of early allograft dysfunction(EAD) was recently validated in a multicenter study of 300 deceased donor liver transplant recipients.This analysis did not differentiate between donation after brain death(DBD) and donation after cardiac death(DCD) allograft recipients.METHODS:We reviewed our prospectively entered database for all DBD(n=377) and DCD(n=38) liver transplantations between January 1,2006 and October 30,2011.The incidence of EAD as well as its ability to predict graft failure and survival was compared between DBD and DCD groups.RESULTS:EAD was a valid predictor of both graft and patient survival at six months in DBD allograft recipients,but in DCD allograft recipients there was no significant difference in the rate of graft failure in those with EAD(11.5%) compared with those without EAD(16.7%)(P=0.664) or in the rate of death in recipients with EAD(3.8%) compared with those without EAD(8.3%)(P=0.565).The graft failure rate in the first 6 months in those with international normalized ratio ≥1.6 on day 7 who received a DCD allograft was 37.5% compared with 6.7% for those with international normalized ratio <1.6 on day 7(P=0.022).CONCLUSIONS:The recently validated definition of EAD is a valid predictor of patient and graft survival in recipients of DBD allografts.On initial assessment,it does not appear to be a useful predictor of patient and graft survival in recipients of DCD allografts,however a study with a larger sample size of DCD allografts is needed to confirm these findings.The high ALT/AST levels in most recipients of DCD livers as well as the predisposition to biliary complications and early cholestasis make these parameters as poor predictors of graft failure.An alternative definition of EAD that gives greater weight to the INR on day 7 may be more relevant in this population.

Ganglioside promotes the bridging of sciatic nerve defects in cryopreserved peripheral nerve allografts

Previous studies have shown that exogenous gangliosides promote nervous system regeneration and synapse formation. In this study, 10 mm sciatic nerve segments from New Zealand rabbits were thawed from cryopreservation and were used for the repair of left sciatic nerve defects through allograft bridging. Three days later, 1 mL ganglioside solution （1 g/L） was sub- cutaneously iniected into the right hind leg of rabbits. Compared with non-injected rats, muscle wet weight ratio was increased at 2-12 weeks after modeling. The quantity of myelinated fibers in regenerated sciatic nerve, myelin thickness and fiber diameter were elevated at 4-12 weeks after modeling. Sciatic nerve potential amplitude and conduction velocity were raised at 8 and 12 weeks, while conduction latencies were decreased at 12 weeks. Experimental findings indicate that ganglioside can promote the regeneration of sciatic nerve defects after repair with cryopre- served peripheral nerve allografts.

Knee salvage procedures: The indications, techniques and outcomes of large osteochondral allografts

The overall incidence of osteochondral defect in the general population is estimated to be 15 to 30 per100000 people.These lesions can become symptomatic causing pain,swelling and decreased function of the knee,and may eventually progress to osteoarthritis.In the young and active population,partial or total knee arthroplasty(TKA)is rarely the treatment of choice due to risk of early failure.Osteochondral allograft transplantation has been demonstrated to be a safe and effective treatment of large osteochondral and chondral defects of the knee in appropriately selected patients.The treatment reduces pain,improves function and is a viable limb salvage procedure for patients,especially young and active patients for whom TKA is not recommended.Either large dowels generated with commercially available equipment or free hand shell allografts can be implanted in more posterior lesions.Current recommendations for fresh allografts stored at4C advise implantation within 21-28 d of procurement for optimum chondrocyte viability,following screening and testing protocols.Higher rates of successful allograft transplantation are observed in younger patients,unipolar lesions,normal or corrected malalignment,and defects that are treated within 12 mo of symptom onset.Patients with bipolar lesions,uncorrectable malalignment,advanced osteoarthritis,and those over40 tend to have less favourable outcomes.

Infusion of donor hepatic non-parenchymal cells prolongs survival of skin allografts in mice:role of microchimerism and IL-4

BACKGROUND: In the mouse skin allograft model, specific immune tolerance to the donor was induced by injection of donor hepatic non-parenchymal cells (NPCs). This markedly prolonged the survival time of the allograft. The mechanism of the induction of immune tolerance with donor hepatic NPCs is thought to be related to microchimerism and the IL-4 level. This work aimed at exploring the way of inducing immune tolerance and understanding the mechanism. METHODS: C57BL/6 (B6) mice were primed by intravenous injection of 2 X10(7) NPCs from C3H mice. Cyclophosphamide (200 mg/kg) was injected intraperitoneally 48 hours later. Eighteen days after the NPC injection, skin from C3H mice was transplanted to B6 mice and the survival of the grafts was assessed. The immune reaction of splenocytes from the treated B6 mice to donor-specific T-cells was measured by H-3-TdR incorporation. Microchimerism in the spleen was determined by flow cytometric analysis sytem (FCAS) analysis, and the serum level of IL-4 was assayed by ELISA at designed times. RESULTS: The survival time of the skin graft was markedly prolonged from 10 days to 70 days in controls. Microchimerism. in the spleen was found as early as day I post-NPC injection, then it increased steadily, and there was a positive relationship between graft survival and the quantity of microchimerism. The ELISA results showed that NPC infusion enhanced IL-4 production, especially in the mice with longer graft survival. CONCLUSION: Donor NPC infusion pre-transplant can prolong the survival of the skin graft and microchimerism and high levels of IL-4 may be involved.

Functional and immunological peculiarities of peripheral nerve allografts

This review addresses the accumulating evidence that live(not decellularized)allogeneic peripheral nerves are functionally and immunologically peculiar in comparison with many other transplanted allogeneic tissues.This is relevant because live peripheral nerve allografts are very effective at promoting recovery after segmental peripheral nerve injury via axonal regeneration and axon fusion.Understanding the immunological peculiarities of peripheral nerve allografts may also be of interest to the field of transplantation in general.Three topics are addressed:The first discusses peripheral nerve injury and the potential utility of peripheral nerve allografts for bridging segmental peripheral nerve defects via axon fusion and axon regeneration.The second reviews evidence that peripheral nerve allografts elicit a more gradual and less severe host immune response allowing for prolonged survival and function of allogeneic peripheral nerve cells and structures.Lastly,potential mechanisms that may account for the immunological differences of peripheral nerve allografts are discussed.

Strength and selection of corticocancellous allografts for anterior interbody spinal fusion

Objective: To quantify the strength of the grafts from different body sites and determine the optimalselection of corticocancellous allografts for anterior interbody fusion. Methods: Complete sets of paired freshfrozen femurs, humeri, tibias and iliac crests were obtained from 6 individual donors. One centimeter thick slicesstarting from the proximal and distal bone ends were cut from the non--diaphysial portions of the long bones usinga razor saw with a customized miter box. 2. 5 cm× 3. 0 cm × 1. 0 cm unicortical bone blocks were shaped similarlyfor clinical use as a lumbar interbody graft. Multiple 1 cm thick grafts with 1. 5 cm depth were obtained from theiliac crests, to simulate a cervical interbody graft. The left and right sides of each pair were randomized intoperpendicular and parallel cut groups in the long bones or tricortical and bicortical preparations of the iliac graft.The samples were tested on an MTS by applying a compressive load to failure. Results: The failure loads of distaltibia and femoral head grafts were significantly higher than distal femur, proximal tibia and burneral head grafts(PR0. 05). The strength of the grafts prepared by parallel cutting decreased significantly as compared with theperpendicular cutting (P <0. 05). No significant changes were seen in femoral and burneral head grafts for the 2sectioning orientations. The grafts closer to the anterior superior iliac spine had significant higher failure loads andfailure strengths than those closer to the posterior superior iliac spine. After trimming off the lateral cortex, themean strength of the bicortical grafts decreased significantly as compared with the tricortical grafts (P <0. 05).Conclusion: The grafts from femoral head and distal tibia by perpendicular cutting have higher failure load than theload bearing in lumbar spine. The grafts cut close to the anterior superior iliac spine are recommended for cervicalinterbody fusion.

Identification of cultured male epidermal allografts by detecting Y chromosome DNA fragments in female burn victims

The existence of cultured male epidermal allografts in 14 bioptic samples of 9 female burned cases was identified by detecting Y chromosome DNA fragments with polymerase chain reaction (PCR). Y chromosome DNA fragments were found in all the samples and the longest case of allograft survival was detected in a 92nd-day sample. This suggests that the survival time of cultured human epidermal allografts on the wounds is longer than those of non-cultured ones.

Prolonged Small Bowel Allografts Survival by CTLA4Ig Gene Transfection in Rats

Objective: To evaluate the local expression of CTLA4Ig gene in small intestines and its effect on prolonging survival time of the small bowel allografts. Methods: The donor small bowels were perfused ex vivo with CTLA4Ig cDNA reconstructed plasmid packaged with lipofectin vector via intra-superior mesenteric artery before transplantation. The CTLA4Ig transgene expression in the small bowel allografts was assessed by immunohistology and RT-PCR after transplantation. Results: Immunohistology and RT-PCR demonstrated expression of CTLA4Ig transgene in the allografts at least for 28 d after transplantation. Eleven cases of the 18 small bowel allografts that received CTLA4Ig gene transfection survived more than 90 d in the recipients. Conclusion: A single ex vivo intra-superior mesenteric artery infusion of CTLA4Ig cDNA reconstructed plasmid packaged with lipofectin induced efficient transduction of the small intestine, and the transfected small bowel allografts could survivor longer in nonimmunosupression rats.

The Evaluation of Refrigerated and Frozen Osteochondral Allografts in the Knee

Between 1998 and 2002, 25 patients who were treated with a refrigerated or frozen allograft were evaluated. The mean patient age was 48 years. The mean lesion size was 4.5 cm2. Validated outcome instruments [Knee Society Score, Western Ontario and McMaster University Score] were used. Clinical and radiographic evaluations were performed pre-operatively and at the most recent follow-up. Histological and electron microscopic analysis was performed on grafts prior to implantation. Clinical follow-up averaged 46 months (range 24 - 60 months). The Western Ontario and McMaster University Score improved from 46 + 24 to 66 + 22 (p = 0.003). The Knee Society Score improved from 104 + 43 to 132 + 42 (p = 0.01). No correlation was noted between graft type and histological or electron microscopy scoring. Post-operative mechanical alignment was not correlated with an improvement in Western Ontario and McMaster University Score (p = 0.19) or Knee Society Score (0.27). Six patients (24%), all refrigerated allografts, were failures and underwent knee arthroplasty. Seventy-six percent of implanted frozen and refrigerated osteochondral allografts are in place 4 years after surgery. Frozen allografts appear to be surviving as well as refrigerated grafts. The use of magnetic resonance imaging may enable the evaluation of graft incorporation and articular cartilage integrity.

The Use of Human Amniotic Allograft on Osteochondritis Dissecans of the Talar Dome: A Comparison with and without Allografts in Arthroscopically Treated Ankles

Arthroscopy of the ankle with micro-fracture technique is one way to initially treat symptomatic talar dome lesions. Human amniotic allograft has been used in similar bone, soft tissue and cartilage defects to aid in healing of tissue using graft cells that have not differentiated into a particular cell line. Patients were taken from the primary surgeon’s practice to include those who had undergone arthroscopy with micro-fracture technique for treatment of a talar dome lesion less than 2 cm2. 101 patient surgeries were completed arthroscopically without additional major procedures. 54 surgeries were completed with human amniotic allograft;47 were completed without (control group). Modified ACFAS ankle scores were taken pre-operatively, 3, 12 and 24 months post-operatively. Visual analog pain scores were taken pre-operatively and 24 months post-operatively. Results comparing pre-operative modified ACFAS scores between the control and graft groups were not significantly different (p = 0.14). There was a significant improvement in both groups’ scores following ankle arthroscopy with micro-fracture as expected. However, the amniotic tissue group did significantly better when comparing the post-operative scores between the control and graft group. Pain scores comparing control and amniotic patient groups were significant (p < 0.001) with amniotic allograft patients achieving a greater improvement in pain reduction than the control both early and at 24 months. There were no complications, wound dehiscence or infections recorded. Combining ankle arthroscopy/micro-fracture technique with human amniotic allograft on talar dome lesions, less than 2 cm2, significantly improves the patients’ pain and ACFAS scores.

Salvage of Failed Osteoarticular Tibia Allografts with Knee Arthroplasties

Background: Limb preservation in musculoskeletal tumor surgery has largely replaced amputation. Biologic reconstructions are now performed as preferred choice;if not feasible options are “megaprostheses”, allografts or composites. Endoprosthetic reconstructions usually provide immediate function, but fail at long term. Osteochondral allografts allow for one-to-one restoration and have potential for incorporation;however degeneration of the cartilage requiring revision almost inevitably will occur. In most cases, revision is then done by endoprosthetic replacement. Aim: In our patients, resurfacing of retained allografts failed. Problems encountered are presented and solutions proposed. Case Presentation: Resurfacing over retained allografts in the 2 index cases has resulted in failures related to fractures and instability. Revision with massive constrained endoprostheses was needed. Based on the experience with these failures, primary endoprosthetic replacement anchored in vital bone in a following case resulted in stable function. Conclusion: Knee replacement for advanced degeneration of the osteochondral allograft apparently needs choosing increased femoro-tibial constraint systems and stem extensions anchored to vital host bone.

Limb Salvage Using Human Placental Allografts: Adding to the Reconstructive Ladder Paradigm

Human placental allografts are the latest treatment modalities for diabetic ulcers, chronic wounds, limbs, and tendons for healing cascade and promoting granulation tissue coverage. Purion® processed dehydrated human amnion/chorion membrane allografts (dHACM), decellularized human collagen matrix (dHCM), dehydrated umbilical cord (dHUC) and micronized dehydrated human amnion/chorion membrane allografts (mdHACM) have been the newest modality used to salvage injured human extremities with tendon and bone exposure. A 53-year-old male was assaulted and sustained second and third degree burns to both legs. The left extremity had a 9.5% total body surface area (%TBSA) burned. The right extremity had a 5.5% TBSA and three exposed tendons (Achilles/flexor digitorum longus/tibialis anterior), muscles, talar and tibial bones. Bilateral extremity pedal pulses were present, and all toes had less than two second capillary refill. Sensation, motor, and strength were normal. During the 48-day-hospital stay, the patient had eight operations: tangential excisional debridements of necrotic tissue with weekly wound dressing applications of dHACM and dHCM, on both legs. In addition, dHUC was applied over the exposed tendons on weeks 2 - 5. The exposed tendons were injected with mdHACM on weeks 4 and 5. Negative pressure wound therapy was applied at 125 mmHg for fourteen days over the wound surfaces covered with a nonadherent dressing, 3% bismuth tribromophenate petrolatum dressing with a glycerol-hydroxyethyl cellulose lubricant. At discharge for rehabilitation, 90% of the split-thickness-skin-graft (STSG) was viable over the right ankle joint, tendons and bone. Use of human placental allografts prevented the need for myocutaneous flap coverage or amputation of the right foot.

Risk assessment of hepatitis E transmission through tissue allografts

Hepatitis E virus(HEV)is a small non-enveloped single stranded RNA virus whose genotypes 3 and 4 have been associated with zoonotic transmission in industrialized countries.HEV infection is considered the main cause of acute hepatitis worldwide.In some cases,transfusion of blood components or organ transplantation have been reported as the source of infection.We have conducted a literature review on the risk of transmission through cell and tissue allografts.Although no case was found,measures to control this risk should be taken when donor profile(based upon geographical and behavioural data)recommended it.Issues to be considered in donor screening and tissue processing to assess and to reduce the risk of HEV transmission are approached.

Expression of fractalkine and its receptor in acute cardiac allografts rejection

Objective To investigate the expression of fractalkine(FKN) and its receptor CX3CR1 in cardiac allografts and the effect of Cyclosporin A(CsA). Methods Three groups of rats underwent heterotopic cardiac transplantation, 45 cases in each group and 5 cases in control group:SD to SD regarded as isograft group (group A), Wistear to SD divided into CsA untreated allograft group(group B) and CsA treated allograft group (group C), normal SD rats as control group. The FKN mRNA expression was detected by one-step RT-PCR method and the expression of FKN and CX3CR1 protein was detected by standard ABC immunohistochemical technique. Results The expressin of FKN mRNA and protein was weak in both isografts and normal heart specimens. The changes of FKN mRNA expression were correkted with the process of acute allograft rejection. The peak of FKN mRNA expression(0.8 ±0.26) appeared on the seventh day after transplantation, which could be downregulated by CsA significantly ( t = 2.390, P 【 0.05). FKN protein was

Polyethylene glycol has immunoprotective effects on sciatic allografts, but behavioral recovery and graft tolerance require neurorrhaphy and axonal fusion

Behavioral recovery using(viable)peripheral nerve allografts to repair ablation-type(segmental-loss)peripheral nerve injuries is delayed or poor due to slow and inaccurate axonal regeneration.Furthermore,such peripheral nerve allografts undergo immunological rejection by the host immune system.In contrast,peripheral nerve injuries repaired by polyethylene glycol fusion of peripheral nerve allografts exhibit excellent behavioral recovery within weeks,reduced immune responses,and many axons do not undergo Wallerian degeneration.The relative contribution of neurorrhaphy and polyethylene glycol-fusion of axons versus the effects of polyethylene glycol per se was unknown prior to this study.We hypothesized that polyethylene glycol might have some immune-protective effects,but polyethylene glycol-fusion was necessary to prevent Wallerian degeneration and functional/behavioral recovery.We examined how polyethylene glycol solutions per se affect functional and behavioral recovery and peripheral nerve allograft morphological and immunological responses in the absence of polyethylene glycol-induced axonal fusion.Ablation-type sciatic nerve injuries in outbred Sprague–Dawley rats were repaired according to a modified protocol using the same solutions as polyethylene glycol-fused peripheral nerve allografts,but peripheral nerve allografts were loose-sutured(loose-sutured polyethylene glycol)with an intentional gap of 1–2 mm to prevent fusion by polyethylene glycol of peripheral nerve allograft axons with host axons.Similar to negative control peripheral nerve allografts not treated by polyethylene glycol and in contrast to polyethylene glycol-fused peripheral nerve allografts,animals with loose-sutured polyethylene glycol peripheral nerve allografts exhibited Wallerian degeneration for all axons and myelin degeneration by 7 days postoperatively and did not recover sciatic-mediated behavioral functions by 42 days postoperatively.Other morphological signs of rejection,such as collapsed Schwann cell basal lamina tubes,were absent in polyethylene glycol-fused peripheral nerve allografts but commonly observed in negative control and loose-sutured polyethylene glycol peripheral nerve allografts at 21 days postoperatively.Loose-sutured polyethylene glycol peripheral nerve allografts had more pro-inflammatory and less anti-inflammatory macrophages than negative control peripheral nerve allografts.While T cell counts were similarly high in loose-sutured-polyethylene glycol and negative control peripheral nerve allografts,loose-sutured polyethylene glycol peripheral nerve allografts expressed some cytokines/chemokines important for T cell activation at much lower levels at 14 days postoperatively.MHCI expression was elevated in loose-sutured polyethylene glycol peripheral nerve allografts,but MHCII expression was modestly lower compared to negative control at 21 days postoperatively.We conclude that,while polyethylene glycol per se reduces some immune responses of peripheral nerve allografts,successful polyethylene glycol-fusion repair of some axons is necessary to prevent Wallerian degeneration of those axons and immune rejection of peripheral nerve allografts,and produce recovery of sensory/motor functions and voluntary behaviors.Translation of polyethylene glycol-fusion technologies would produce a paradigm shift from the current clinical practice of waiting days to months to repair ablation peripheral nerve injuries.

Use of machine learning models for the prognostication of liver transplantation: A systematic review

BACKGROUND Liver transplantation(LT)is a life-saving intervention for patients with end-stage liver disease.However,the equitable allocation of scarce donor organs remains a formidable challenge.Prognostic tools are pivotal in identifying the most suitable transplant candidates.Traditionally,scoring systems like the model for end-stage liver disease have been instrumental in this process.Nevertheless,the landscape of prognostication is undergoing a transformation with the integration of machine learning(ML)and artificial intelligence models.AIM To assess the utility of ML models in prognostication for LT,comparing their performance and reliability to established traditional scoring systems.METHODS Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines,we conducted a thorough and standardized literature search using the PubMed/MEDLINE database.Our search imposed no restrictions on publication year,age,or gender.Exclusion criteria encompassed non-English studies,review articles,case reports,conference papers,studies with missing data,or those exhibiting evident methodological flaws.RESULTS Our search yielded a total of 64 articles,with 23 meeting the inclusion criteria.Among the selected studies,60.8%originated from the United States and China combined.Only one pediatric study met the criteria.Notably,91%of the studies were published within the past five years.ML models consistently demonstrated satisfactory to excellent area under the receiver operating characteristic curve values(ranging from 0.6 to 1)across all studies,surpassing the performance of traditional scoring systems.Random forest exhibited superior predictive capabilities for 90-d mortality following LT,sepsis,and acute kidney injury(AKI).In contrast,gradient boosting excelled in predicting the risk of graft-versus-host disease,pneumonia,and AKI.CONCLUSION This study underscores the potential of ML models in guiding decisions related to allograft allocation and LT,marking a significant evolution in the field of prognostication.