Fresh Allograft Research Articles

Cryopreservation alters antigenicity of allografts in a porcine model of transplant vasculopathy

The need for arterial grafts in coronary surgery to complement autologous vessels has generated interest in cryopreservation of small diameter allografts. We evaluated functional and histologic changes occurring in cryopreserved allografts 3 months after porcine femoral artery transplants. Methods Twenty recipient and 15 donor pigs included a control group of 16 fresh and 12 cryopreserved nonimplant arteries were used. Fresh ( n = 5) and cryopreserved ( n = 5) autografts were implanted to assess cryopreservation effects in the absence of rejection. Fresh allografts with or without treatment with cyclosporine (CsA) ( n = 6 of 8) and cryopreserved allografts with or without treatment with CsA ( n = 6 of 10) were performed to study the antigenicity of cryopreserved allografts. Arteries were stained with hematoxylin and eosin, Masson's trichrome, and orcein for morphometric analyses and immunostained to identify endothelial cells, smooth muscle cells, T lymphocytes, and macrophages. Results Among nonimplant arteries, cryopreservation reduced α-actin expression and increased the luminal area. All implanted autografts were patent. Cryopreserved autografts showed reduced α-actin expression and developed intimal hyperplasia compared to fresh autografts. Treatment with CsA improved the patency of fresh allografts from 0% to 83% ( P < .01) and of cryopreserved allografts from 40% to 100% ( P < .05). Cryopreserved allografts showed substantial intimal hyperplasia, and fresh allografts had more T lymphocyte infiltration in the intimal layer with aneurysmal dilatation. Conclusions Cryopreservation reduces the deposition of inflammatory cells and prevents the thrombosis or aneurysmal lesions observed in fresh allografts. Therefore, cryopreservation modifies the antigenicity of vascular allografts.

Renal transplantation in patients with abdominal aortic aneurysm--a new surgical approach.

An increasing number of abdominal aortic aneurysms occurs in renal failure patients because of an accelerated atherosclerosis process associated with uraemia. When technically feasible, endovascular repair of an abdominal aortic lesion should be considered as the treatment of choice. If a surgical repair is suggested, there are several options to select from. Since November 1999, we performed simultaneous aortic reconstruction using fresh arterial allograft and kidney transplantation in five uraemic patients with asymptomatic abdominal aortic aneurysm. The operative and postoperative course of four patients passed without major complications. One patient had ischaemic colitis early after the operation, which required a partial resection of the colon. One patient died 6 weeks after the operation due to non-vascular causes. In conclusion, the advantage of our single-phase procedure is that both diseases are treated simultaneously during a single hospital stay. Moreover, with our procedure, the risk of vascular graft infection in patients with chronic immunosuppression is low.

Effects of FK506 on cold preservation of nerve allografts

目的 研究 FK506结合冷藏保存应用于同种异体神经移植后对神经再生的 实验效果.方法 60只雌性Wistar大鼠做为受体动物模型,按移植物的不 同分为4组,每组15只大鼠.A组:新鲜同种异体神经移植组;B组:冷藏保存同种异体神经 移植组;C组:冷藏保存同种异体神经移植组,同时服用FK506,剂量为(2mg/kg)-1 ·d-1 ;D组:冷藏保存同种异体神经移植组,同时服用FK506,剂量为(0.5mg/kg )-1·d-1.于术后4、8、10周各组 分别行大体观察,测定比目鱼肌肌湿重,运动神经传导速度(MNCV)和运动动作电位(CMAP )的波幅及组织学变化.结果术后8、10周时,4组中以C组神经再生最好 ,D组神经再生好于A、B组,但与C组相比则较差.轴突计数、肌湿重的统计学分析,有明显 差别.结论冷藏保存预处理同种异体神经移植后可以加速神经再生及功能恢复。

Surgical Treatment of Local Prosthetic Graft Infection with Fresh Arterial Homograft: Report of Four Cases

Infection following vascular operations, particularly after synthetic prosthetic graft implantation, remains a serious complication of reconstructive vascular surgery. In this paper, four cases of bifurcated graft infection limited to the distal part of one of the branches are presented. Because of the unsatisfactory results of conventional treatment, the patients underwent in situ replacement of the infected distal part of the prosthesis branch with fresh arterial homograft. Follow-up revealed complete remission of infection. The use of arterial homograft can be limited to the replacement of infected segment of prosthesis.

Platelet rich plasma and fresh frozen bone allograft as enhancement of implant fixationAn experimental study in dogs

Platelet rich plasma and fresh frozen bone allograft as enhancement of implant fixationAn experimental study in dogs

Nerve regeneration and functional recovery after a sciatic nerve gap repaired by an acellular nerve allograft made through chemical extraction

Objective To observe the nerve regeneration and functional recov er y in canines, in which a large gap was made in the continuity of the sciatic ner ve and the gap was repaired by acellular allograft through chemical extraction. Methods 15 canines were divided into acellular nerve allografting group (ANG, 6 canines), autografting group (AG, 6 canines) and fresh nerve allografting group (FNG, 3 canines). The sciatic nerves on the right side of all animals were expos ed and 5.0 cm long segments were removed from the mid-thigh level and replaced by one of the three types of grafts. The motor recovery was assessed by gait tes t at month 6 postoperatively. The sensory and motor conducting functions were as sessed by electrophysiological experiments. The nerve regeneration was revealed by morphological studies on the grafting segments, the distal tibial nerves and motor end-plate of the target muscle. Results All the animals in ANG and AG gro ups had similar patterns of right posterior limb gait cycle and right ankle move ments. Stimuli (1.0-2.0 mA, 0.1 ms, 1.0 Hz) to the sciatic nerves proximal to t he implanted segment resulted in motor-evoked potentials recorded from the musc ulus triceps surae. The motor conducting velocities of the grafting segments wer e on average 47.2 m/s in ANG, 60.9 m/s in AG and 122.0m/s in normal controls. St imuli (5.0-10.0 mA, 0.2 ms, 1.9 Hz) to the right distal tibial nerves resulted in sensory-evoked potentials recorded from the cortical area in all the canines in ANG and AG groups. Axons regeneration and Schwann cells migration had reoccu pied the empty basal lamina tubes of the acellular allografting segments without excessive sign of inflammation. ANG and AG had similar nerve regeneration with massive large nerve fibers in the distal tibial nerves and vast motor end-plate in the target muscle. Conclusions The patterns of functional recovery and nerve regeneration tend to be similar 6 months after implantation in the canines, in which a 5.0 cm gap in the continuity of the sciatic nerve is repaired by either chemical acellular nerve allografting or autografting.

Allograft replacement for infrarenal aortic graft infection: early and late results in 179 patients

Objectives We evaluated early and late results of allograft replacement to treat infrarenal aortic graft infection in a large number of patients and compared the results in patients who received fresh allografts versus patients who received cryopreserved allografts. Methods From 1988 to 2002 we operated on 179 consecutive patients (mean age, 64.6 ± 9.0 years; 88.8% men). One hundred twenty-five patients (69.8%) had primary graft infections, and 54 patients (30.2%) had secondary aortoenteric fistulas (AEFs). Fresh allografts were used in 111 patients (62.0%) until 1996, and cryopreserved allografts were used in 68 patients (38.0%) thereafter. Results Early postoperative mortality was 20.1% (36 patients), including four (2.2%) allograft-related deaths from rupture of the allograft (recurrent AEF, n = 3), all in patients with fresh allografts. Thirty-two deaths were not allograft related. Significant risk factors for early mortality were septic shock ( P < .001), presence of AEF ( P = .04), emergency operation ( P = .003), emergency allograft replacement ( P = .0075), surgical complication ( P = .003) or medical complication ( P < .0001), and need for repeat operation ( P = .04). There were five (2.8%) nonlethal allograft complications (rupture, n = 2; thromboses, which were successfully treated at repeat operation, n = 2; and amputation, n = 1), all in patients with fresh allografts. Four patients (2.2%) were lost to follow-up. Mean follow-up was 46.0 ± 42.1 months (range, 1-148 months). Late mortality was 25.9% (37 patients). There were three (2.1%) allograft-related late deaths from rupture of the allograft, at 9, 10, and 27 months, respectively, all in patients with fresh allografts. Actuarial survival was 73.2% ± 6.8% at 1 year, 55.0% ± 8.8% at 5 years, and 49.4% ± 9.6% at 7 years. Late nonlethal aortic events occurred in 10 patients (7.2%; occlusion, n = 4; dilatation < 4 cm, n = 5; aneurysm, n = 1), at a mean of 28.3 ± 28.2 months, all but two in patients with fresh allografts. The only significant risk factor for late aortic events was use of an allograft obtained from the descending thoracic aorta ( P = .03). Actuarial freedom from late aortic events was 96.6% ± 3.4% at 1 year, 89.3% ± 6.6% at 3 years, and 89.3% ± 6.6% at 5 years. There were 63 late, mostly occlusive, iliofemoral events, which occurred at a mean of 34.9 ± 33.7 months in 38 patients (26.6%), 28 of whom (73.7%) had received fresh allografts. The only significant risk factor for late iliofemoral events was use of fresh allografts versus cryopreserved allografts ( P = .03). Actuarial freedom from late iliofemoral events was 84.6% ± 7.0% at 1 year, 72.5% ± 9.0% at 3 years, and 66.4% ± 10.2% at 5 years. Conclusions Early and long-term results of allograft replacement are at least similar to those of other methods to manage infrarenal aortic graft infections. Rare specific complications include early or late allograft rupture and late aortic dilatation. The more frequent late iliofemoral complications may be easily managed through the groin. These complications are significantly reduced by using cryopreserved allografts rather than fresh allografts and by not using allografts obtained from the descending thoracic aorta.

Incorporación de aloinjertos óseos intercalares corticales: Estudio experimental en conejos

An experimental study was carried out on 40 rabbits in order to evaluate the incorporation of large intercalary bone allografts and the influence of freezing on the bone graft. In 36 rabbits resection of 3 centimetres of diaphysis of the tibia was carried out and the defect was rebuilt with different types of bone graft: fresh autograft and frozen autograft, fresh allograft and frozen allograft; osteosynthesis was carried out with two intramedullary Kirschner needles. Monthly radiological studies were made until the sacrifice of the animals, at 2, 4 and 8 months. A densitometric, histological and diaphanisation study of the tibias was made with Spalteholz's technique. In 24 animals 25 mg/kg of oxytetracicline was administered 3 and 6 days before sacrifice, to study the velocity of bone apposition in the graft. We observed a good and excellent radiological consolidation in 80% of the grafts (99% in the autografts and 66% in the allografts). The bone density showed a fall until the 4th month due to bone reabsorption except in the group of fresh allografts. The revascularization of the allografts was slower and poorer than the autografts, but with the same vascular pattern. Bone incorporation and neoformation were greater in the autografts without significant differences with the frozen allografts. The speed of bone apposition did not change with the different types of bone graft used. Freezing facilitated and accelerated incorporation and the quantity of bone neoformation of the allografts.

Transcriptional profiling and growth kinetics of endothelium reveals differences between cells derived from porcine aorta versus aortic valve.

Valvular tissue and aorta calcify at different rates when placed as fresh homografts or cryopreserved allografts. Furthermore, differences between valvular endothelial cells and aortic endothelial cells are not well appreciated. We established primary cultures of valve and aortic endothelial cells derived from swine and tested transcriptional and proliferative differences on various extracellular matrices. Transcriptional profiling was performed on primary cultures of porcine valve and aortic endothelial cells. We extracted total RNA from both cell types and created cDNA libraries. We scored for 847 genes important in signal transduction pathways, and measured their expression on valve and aortic endothelial cells. To determine if there were functional differences between aortic and valvular cells, their growth rate was determined by cell counting on various extracellular matrices. Of 847 genes investigated, 69 (8.1%) were transcriptionally active on aortic endothelial cells and 89 (10.5%) on valve endothelial cells. Common to both cell types were 55 genes, which represents 79.7% (55/69) of activated genes on aortic endothelial cells and 61.8% (55/89) of those in valve endothelial cells. Remarkable features of the analysis included Ephrin ligand and receptor specificity for cell type, a potential fibroblast growth factor autocrine loop in both cell types, as well as upregulation of the platelet-derived growth factor receptor in valvular cells. Aortic endothelial cells were noteworthy of upregulation of vascular endothelial cell growth factor-B and vascular cell adhesion molecule. Proliferation analysis revealed that valve endothelial cells grew more rapidly (12-fold over control) than aortic endothelial cells (3-fold over control). Furthermore, valve endothelial cells proliferated most rapidly on gelatin or collagen, whereas aortic endothelial cells were most proliferative on lysine or laminin. Valve and aortic endothelial cells have different transcriptional and proliferative profiles. The knowledge of these differences may be an exploitable strategy in the future rational design of artificially engineered valve surfaces and in the study of the valve antigenicity, immunogenicity and structural failure.

Acellular scaffolding for vascular tissue-engineering in a canine model

Introduction: We are presently investigating acellular venous tissue as a bioscaffold to be recellularized with the recipient’s own cells prior to implantation. This study tests the biocompatibility and mechanical stability of this construct in terms of graft patency, acute dilatation and rupture, the ability to achieve and maintain hemostasis and resist infection in a canine model. Methods: Twenty-six carotid interposition grafts were constructed using 13 mongrel dogs. Graft material was obtained from the external jugular veins of the same 13 animals (14 autografts, 4 acellular autografts, 4 allografts, and 4 acellular allografts). Decellularization was performed using 0.075% SDS. At two weeks, each graft was evaluated for evidence of gross patency and dilatation, and perfusion fixed for detailed histological and immunohistochemical analyses (H&E, Factor VIII, smooth muscle actin, and inflammatory markers). Morphometric analysis of the cells present in 20 random high-powered fields (hpf) was conducted at the graft’s midpoint. Healing response was further characterized by evaluation of graft incorporation into surrounding tissues and recellularization at the anastamotic sites. Results: All animals survived without neurologic deficit with 100% patency, and no dilatation or rupture. There were no clinically significant infections. The quantified inflammatory reaction was significantly greater in fresh allografts compared to acellular allografts, acellular autografts and fresh autografts: 59 ± 24 vs 19 ± 15, 27 ± 18 or 19 ± 8 cells/hpf, respectively, P < 0.05. There was no significant difference between fresh autografts and acellular allografts, P > 0.05. Fresh autografts also retained endothelial and smooth muscle cells, which were absent in decellularized grafts at implantation and at two weeks. Conclusions: We have previously shown sufficient strength, the ability to support endothelial cells, preserved extracellular collagen and elastin, and reduced allosensitization. Acellular venous scaffolding also appears to avoid acute dilatation or rupture, maintain hemostasis and remain free of infectious complications. It is our hope that this may improve the overall utility and functionality of autologous cell seeding and continue to remodel as the recipient’s new blood vessel in vivo.

Experimental evaluation of the usefulness of osteochondral allograft for articular cartilage defect

AbstractThis study was conducted to evaluate the usefulness of osteochondral allografts for articular cartilage defects. Cartilaginous defects measuring 4.5mm in diameter were experimentally prepared in both the weight-bearing and nonweight-bearing regions of the femur in six male miniature pigs (9 months old). Osteochondral grafting was performed using fresh autografts (group AU), fresh allografts (group AL), or frozen allografts (group FA). Untreated cartilaginous defects were used as the control (group D). All the pigs were killed 4 weeks later, and the respective osteochondral grafts were macro- and microscopically evaluated. Hematoxylin and eosin staining, safranin O staining, and immunostaining [matrix metalloprotease-1 (MMP-1) and tissue inhibitor of metalloprotease-2 (TIMP-2)] were used for the histological evaluations of transplanted cartilage. Macroscopic and microscopic findings were assessed according to the criteria proposed by Wakitani et al. Although groups AU and AL showed similar median scores (ranges) for the evaluation of cartilaginous defect restoration, groups FA and D showed unfavorable scores: 3.9 (0–9) in group AU; 4.5 (0–12) in group AL; 10.2 (4–12) in group FA; and 7.0 (5–11) in group D. Immunostaining revealed almost identical results in groups AU and AL. As there were no histologically significant differences in the status of the osteochondral grafts between fresh autografts and fresh allografts, fresh allografts might be useful donor osteochondral grafts.

Reoperation after fresh homograft replacement: 23 years' experience with 655 patients.

Through a retrospective study on the use of fresh homografts in 655 aortic valve replacement patients over a period of 23 years, we aimed to assess the reasons for eventual reoperation and causes of valve dysfunction. Between January 1980 and December 2002, 655 patients received fresh homografts. All homografts were antibiotic sterilized and stored at 4 degrees C. During this time, 139 patients (116 male and 23 female) with a mean age of 46.7 years (range 18-72) required reoperation. The 30-day hospital overall mortality was 2.87%. The mean durability for all homografts was 12.4+/-4.54 years (1 month to 23 years). The cumulative rates for freedom from reoperation for any cause were 94.09+/-2% at 5 years and 87.9%+/-4% at 10 years, 76.6 at 15 years, 49.55 at 20 years. The major cause of valve dysfunction and indication for reoperation was degeneration in 111 patients (79.8%). Predominant aortic valve insufficiency in 87 patients (62.5%) and predominant stenosis in 24 patients (17.26%). Endocarditis occurred in 21 patients (15.1%). Early endocarditis was diagnosed in five patients (3.59%), late endocarditis in 16 patients (11.5%). Additional causes for reoperation included ascending aortic aneurysm, mitral valve insufficiency and congestive cardiomyopathy. Seventeen patients (12.2%) required concomitant procedures. Coronary artery bypass grafting was performed in six cases (4.3%), mitral valve replacement in five cases (3.59%), mitral valve annuloplasty in six (4.3%). The primary reoperative procedure was artificial/mechanical aortic valve implantation. In five cases, St. Jude Medical conduit grafts were implanted due to ascending aortic aneurysms. Homograft reimplantation was performed in four cases. One patient underwent mitral valve replacement and one patient received a heart transplant. The results of the study suggest that reoperation in patients with aortic homografts is a low-risk procedure as compared to alternative therapies. Primary allograft aortic valve replacement can give acceptable results for up to 23 years. The major cause of valve dysfunction and indication for reoperation was degeneration. Cumulative rates for freedom from reoperation for any cause in age groups suggest careful selection and indications in homograft implantation in the younger patients. Young age is a risk factor for an early homograft structural deterioration (degeneration).

Establishment of a heart valve homograft bank using existing facilities

THE PROGRESS of cryobiology together with broadening surgical indications have increased the demand for heart valve homografts. Cryopreserved aortic valves have been implanted either in the sub-coronary position or as a complete aortic root replacement. Reconstruction of the right ventricular outflow tract for various forms of congenital heart defects has been performed with aortic or pulmonary homografts. Pulmonary valve homografts have been used for right ventricular outflow reconstruction during the “Ross” procedure. Mitral valve homografts are used for the replacement of the mitral valve in female patients of child-bearing age and in other patients who bears contraindications for anticoagulation. The disadvantages of homografts include limited availability and durability. Although some authors claim the durability of cryopreserved homograft to be superior to that of fresh homografts, other studies did not affirm this, and the different results are probably related to some extent to variability in the sterilization and the preservation protocols. On the other hand, it is widely agreed that cryopreservation increases the shelf life of homografts from a few weeks of the fresh antibiotic-preserved material to at least 5 years among cryopreserved grafts. Thus the problem of availability may be partly solved by using cryopreservation rather than “fresh” grafts, and by establishing more homograft laboratories (“banks”) in remote areas. Establishing an independent homograft bank is costly. We sought to establish an independent bank at no additional cost as a model that can be implemented in any medical center containing some form of tissue bank (eg, a bone marrow bank).

Heterotopic transplantation of cryopreserved tracheae in a rat model.

The successful use of cryopreserved tracheal allografts in canine models suggests their use in humans. The grade of genetic difference, the mechanism of revascularisation and the method of cryopreservation are not clearly defined. The purpose of our study was to investigate the rejection of tracheal transplants in a standardised heterotopic rat model using different forms of cryopreservation. Tracheae from Brown Norway rats were implanted into the omentum from Brown Norway rats or Lewis rats. We transplanted fresh isografts or allografts and pretreated isografts or allografts. Cryopreservation was performed in a medium containing 10% dimethyl sulphoxide at -80 degrees C for 28 days (I) or -196 degrees C for 84 days (II) or without medium at -80 degrees C for 28 days (III). The transplants were excised after 7 and 21 days, respectively. Histological examinations revealed normal structure and function of isografts after 21 days. In the cryopreserved isograft, the epithelium had disappeared and the tracheal lumen was partially obstructed by a non-compact fibrous tissue. In the fresh allografts, the epithelium was replaced by aggressive fibrous tissue, infiltrating the membranous part of the trachea and occluding the tracheal lumen. The cartilage was vital without any sign of rejection. In the cryopreserved allografts, the tracheal lumen was obstructed by dense fibrous tissue with an inflammatory reaction. The cartilage of cryopreserved allografts (II) and (III) had lost the nuclei corresponding to non-vital tissue. Only in the cryopreserved allografts (I) did we find nodular regeneration at the edges of the cartilaginous bow. The heterotopic transplantation model allows the study of the mechanisms leading to tracheal obstruction. Cryopreservation was found to have no clear advantage in reducing transplant immunogenicity. Cryopreservation leads to significant damage to the cartilage, the intensity of which is dependent on the mode of cryopreservation.

Immediate versus delayed meniscal allograft transplantation in sheep.

The aim of the current study was to assess the effect of immediate and delayed transplantation on articular cartilage. Icelandic sheep had surgery on the medial menisci in both knees. The knees were divided into four groups; 16 control knees had sham surgery, 15 knees had meniscectomy, 14 knees had immediate allograft transplantation, and 14 knees had delayed transplantation 3 months after meniscectomy. The two horns of the fresh allograft were fixed with suture anchors through bone tunnels. The sheep had autopsies 6 months after surgery. An additional six knees were examined 3 months after meniscectomy to examine the cartilage before the delayed implantation. Four standardized samples were taken from the medial compartment of the knee for histologic evaluation according to a modification of Mankin's system, where degenerative changes to the articular cartilage were scored semiquantitatively for structure, proteoglycan content, cellularity, and cell cloning. Knees that had meniscectomy and delayed transplantation showed equally high scores in articular cartilage degeneration, and both scored higher than knees that had immediate transplantation, which again scored higher than the control knees. In short-term observations, immediate medial meniscal allograft transplantation reduced but did not prevent degeneration of the articular cartilage. Immediate transplantation was superior to delayed transplantation in preventing cartilage degeneration.

Immediate Versus Delayed Meniscal Allograft Transplantation in Sheep

The aim of the current study was to assess the effect of immediate and delayed transplantation on articular cartilage. Icelandic sheep had surgery on the medial menisci in both knees. The knees were divided into four groups; 16 control knees had sham surgery, 15 knees had meniscectomy, 14 knees had immediate allograft transplantation, and 14 knees had delayed transplantation 3 months after meniscectomy. The two horns of the fresh allograft were fixed with suture anchors through bone tunnels. The sheep had autopsies 6 months after surgery. An additional six knees were examined 3 months after meniscectomy to examine the cartilage before the delayed implantation. Four standardized samples were taken from the medial compartment of the knee for histologic evaluation according to a modification of Mankin’s system, where degenerative changes to the articular cartilage were scored semiquantitatively for structure, proteoglycan content, cellularity, and cell cloning. Knees that had meniscectomy and delayed transplantation showed equally high scores in articular cartilage degeneration, and both scored higher than knees that had immediate transplantation, which again scored higher than the control knees. In short-term observations, immediate medial meniscal allograft transplantation reduced but did not prevent degeneration of the articular cartilage. Immediate transplantation was superior to delayed transplantation in preventing cartilage degeneration.

Effect of cryopreservation on patency and histological changes of arterial isogeneic and allogeneic grafts in the rat model.

Vascular grafting is used frequently in the management of length discrepancies between blood vessels. Cryopreservation permits vascular graft storage and aids availability; however, long-term patency of cryopreserved arterial allografts is not well established. Fifty Fisher and 55 Wistar rats were used in the study. Thirty-eight cryopreserved Fisher femoral arterial grafts were transplanted into the femoral arteries of 15 Fisher (cryoisografts) and 23 Wistar rats (cryoallografts). Thirty-two fresh Fisher arterial grafts were implanted into 32 Wistar femoral arteries (fresh allografts). The animals were killed at 1, 4, and 8 months in each group, and graft patency was assessed. One-month graft patency was 100% in all groups. At 4 months, graft patencies were 86%, 100%, and 75% in the cryoisografts, cryoallografts, and fresh allografts respectively. All cryoisografts and fresh allografts were patent, whereas all the cryoallografts were occluded at 8 months ( < 0.01). Cryopreserved rat arterial allografts offered satisfactory graft patency up to 4 months after implantation and may therefore be applicable clinically in selected cases.

Postal survey on the use of glycerol-preserved allografts in clinical practice

Glycerol-preserved allografts (GPAs) are in widespread use throughout Europe in the management of burns injury. However, little is known of the clinical usage and effectiveness of GPA. To gain more insight into clinical practice, The Euro Skin Bank (ESB), which is the main provider of GPA, sent a questionnaire to 62 burn centres which had received GPA from the ESB in the last 5 years. Replies from 37 centres were received, of which 31 contained useful information. Ninety percent of correspondents used GPA regularly, although 24% of centres would prefer to use cryo-preserved allografts and 16% preferred fresh allografts. Three principal indications for GPA were identified: its use as a temporary cover on freshly excised wounds; its use as an overlay on widely expanded autografts and its use to improve the quality of the wound bed prior to autografting. Twenty-five percent of correspondents used GPA as a biological dressing for partial thickness injuries. Pre-operative topical therapy consisted of semi-closed wound treatment with frequent dressing changes and application of silver sulfadiazine (SSD) or SSD with 1% cerium nitrate. Twenty percent of correspondents also used povidone iodine. The surgical approach of early excision and wound coverage (autograft or allograft) were followed by all correspondents. Graft fixation was achieved by staples alone or in combination with fibrin glue or adhesive dressings. Post-operative care comprised frequent dressing changes. Few clinicians used topical antibacterial agents and peri-operative antibiotics were prescribed by a third of correspondents. Few complications were reported following GPA use. Around 50% of clinicians reported “occasional” wound infection; around 50% of clinicians reported “occasional” graft failure. In general, GPA appeared to perform well in clinical practice.

The immunomodulatory effect of cryopreservation in rat tracheal allotransplantation

Background Cryopreservation is one solution to the problem of donor organ deficit. To investigate the effect of cryopreservation on tracheal allografts, we performed 2 experiments in rats. Methods In Experiment 1, we assessed second-set graft rejection. Two weeks after primary heterotopic transplantation (Group 1, fresh isografts; Group 2, fresh allografts from Lewis rats; and Group 3, cryopreserved allografts from Lewis rats; n = 5, respectively), each animal underwent secondary heterotopic grafting with isografts and allografts from Lewis and Wistar Furth rats ( n = 5, respectively). Four weeks after the secondary transplantation, all grafts were retrieved for histologic analysis. In Experiment 2, we assessed the long-term results of allograft cryopreservation, without immunosuppression therapy. Six months after transplantation of fresh (Group 4) and cryopreserved (Group 5) allografts, the tracheal segments (each group, n = 5) were histologically evaluated. Results In Experiment 1, only the secondary allografts from Lewis rats in Group 2 did not maintain lumen structure and often showed dislocated or destroyed cartilage. Second-set graft rejection was specifically recognized in Group 2, but not in Group 1 or 3. In Experiment 2, the cryopreserved allografts appeared almost normal and lumen rigidity was preserved 6 months after transplantation. These allografts were superior to the fresh allografts in patency and in cartilage dislocation and mononuclear cell infiltration scores, but not in the viable chondrocyte ratio. Conclusions We conclude that cryopreservation may produce successful long-term results because of its immunomodulatory effect on tracheal allografts.

Donor cell survival and repopulation after intraarticular transplantation of tendon and ligament allografts.

The specific cells within ligaments and tendons are important to maintain the unique structural and material properties of these tissues. The use of tendon and ligament allografts with living cells for ligament reconstruction would be desirable assuming that these cells would survive after transplantation and continue to function. We assessed the fate of donor cells in fresh allografts of the patellar and anterior cruciate ligaments after transplantation. The cells in these allografts used to reconstruct the anterior cruciate ligament did not survive. This was demonstrated using a DNA probe technique that clearly distinguished donor cells from host cells in the Spanish goat model. The donor cells were replaced by host cells in a rapid manner. The host cells that repopulated the allografts assumed the histologic similarity to the fibroblasts they replace. Simultaneous full-thickness skin transplants in the same animals were not rejected during the interval of rapid loss of donor DNA from the allografts. The absence of rejection of the skin grafts at the one-week interval suggests that no pre-existing antibody associated with an immune reaction was responsible for the rapid loss of DNA in the allografts. The clinical basis for utilizing intra-articular allografts with living donor cells needs further justification to account for their increased expense, more complicated surgical logistics, and higher potential risk of disease transmission.