BLM has Contrary Effects on Repeat-Mediated Deletions,based on the Distance of DNA DSBs to a Repeat and Repeat Divergence

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Effects of a Peracetic Acid Disinfection Protocol on the Biocompatibility and Biomechanical Properties of Human Patellar Tendon Allografts

Patellar tendon allografts, retrieved from cadaveric human donors, are widely used for replacement of damaged cruciate ligaments. In common with other tissue allografts originating from cadaveric donors, there are concerns regarding the potential for disease transmission from the donor to the recipient. Additionally, retrieval and subsequent processing protocols expose the graft to the risk of environmental contamination. For these reasons, disinfection or sterilisation protocols are necessary for these grafts before they are used clinically. A high-level disinfection protocol, utilising peracetic acid (PAA), has been developed and investigated for its effects on the biocompatibility and biomechanics of the patellar tendon allografts. PAA disinfection did not render the grafts either cytotoxic or liable to provoke an inflammatory response as assessed in vitro . However, the protocol was shown to increase the size of gaps between the tendon fibres in the matrix and render the grafts more susceptible to digestion with collagenase. Biomechanical studies of the tendons showed that PAA treatment had no effect on the ultimate tensile stress or Young's modulus of the tendons, and that ultimate strain was significantly higher in PAA treated tendons.     

Bone bank service in Odense, Denmark. Audit of the first ten years with bone banking at the Department of Orthopaedics, Odense University Hospital

There has been an increase in the demand for allograft bone in recentyears. The Odense University Hospital bone bank has been in function since1990,and this paper outlines our results during the 10 year period 1990–1999.Potential donors were screened by contemporary banking techniques which includea social history, donor serum tests for HIV, hepatitis B and C, and graftmicrobiology. The bones were stored at –80 °C. No typeofsecondary sterilisation was made. 423 femoral heads were approved and donatedto300 patients,1–6 heads/operation. The allografts have been used mainly toreconstruct defects at revision hip arthroplasty (34%), and for fracturesurgery(24%). 7 % of all transplanted patients were reoperated because of infection.Inthe hip revision group the infection rate was 4 %. There were no cases ofdisease transmission. During the 10 year period there was a change in theclinical use of the allografts. In the first years the allografts were mainlyused for spinal fusion surgery, but today the majority are used in hip revisionand fracture surgery. The clinical results correspond to those reported inlarger international series.     

Composite grafts in the treatment of osteosarcoma of the proximal humerus

Treatment of osteosarcoma (OSA) of the proximal humerus poses many difficulties and challenges to the treating team. Between 1993 and 2000, we treated 11 patients (three women, eight men; age range, 17–74 years) suffering from OSA of the proximal humerus by composite: massive allografts and long humeral prosthesis. At presentation, 10 patients were at stage 2-B and one at stage 3-B of OSA. One patient presented with a pathologic fracture. All patients except patient No. 6, received preoperative chemotherapy followed by limb salvage surgery and postoperative chemotherapy.Surgical margins were graded as wide in all patients. Postoperative complications included non-union at the allograft/host junction (which united after auto grafting) and superficial wound infections that resolved after antibiotic therapy. All surgical procedures were performed by a team headed by an orthopedic oncologist and shoulder surgeon. At latest follow-up (December 2001) all patients, with the exception of one (who was at stage 3-B at presentation) were alive, and had good function of the upper limb. It is our opinion that the team approach comprising an orthopedic oncologist and shoulder surgeon greatly contributed to the good surgical outcome, and hence the good survival and functional results of the patients. Bone allograft offers a modular malleable durable solution to the resected bone segment.     

Validation of Radiation Dose Received by Frozen Unprocessed and Processed Bone during Terminal Sterilisation

Fresh frozen femoral heads (FH) and frozen processed bone (FP) are widely used as a source of allograft bone. The FP bone and some of the FH are terminally sterilised by the National Blood Service Tissue Services (NSBTS), via application of a minimum 25 kGy gamma radiation dose. To comply with the Guidelines for the Blood Transfusion Services in the United Kingdom (2002), frozen musculoskeletal tissue must be maintained below −40 °C during storage and transit. In practice, NBSTS stores bone long-term in −80 °C freezers. During transport for irradiation, a temperature of circa −79 °C is maintained by packing the bone in dry ice. An evaluation of the radiation dose received by bone has previously been made via dosimeters located within the tissue and dry ice, however, some evidence suggests that low temperature can influence the accuracy of the dosimeter readings. The aim of this study was to determine the actual radiation dose received by FH and FP bone during the irradiation process. This was accomplished by comparing radiation dose readings from dosimeters placed in dry ice with dosimeters placed in a dry ice substitute of similar dimensions and density i.e., polytetrafluoroethylene (PTFE) at ambient temperature. New packing formats were developed for both FH and FP bone such that 15 FH or 3 kg of FP bone could be irradiated in one transport box at any given time in a standardised fashion. The data show that low temperature consistently increased dosimeter readings 10–27%, and that radiation dose always fell within the range of 25–40 kGy (FH = 25.1–35.7 kGy; FP bone = 25.2–32.4 kGy).     

Activation and migration of allo-peptide specific TCR transgenic T cells in cardiac allograft rejection

T cells from TCR transgenic mice, expressing receptors specific for an allogeneic MHC class I peptide, were used to track T cell activation and migration in normal adoptive recipients that were subsequently transplanted with heterotopic hearts that were syngeneic except for a transgenic MHC class I antigen. T cells rapidly disappeared from the blood into the lymphoid tissues where they were activated within one day after transplantation. T cells initially formed discrete clusters in the spleen and lymph nodes. After proliferating for 2-4 days in lymphoid tissues, T cells reappeared in the blood and migrated to the heart and the intestines. The T cells underwent another round of proliferation in the heart, but not the intestines, and induced cardiac rejection uniformly on 6 day.     

建立小鼠皮肤移植排斥模型稳定获得记忆T细胞

目的建立一种稳定的通过小鼠皮肤移植获得小鼠记忆T细胞的方法。方法以C57BL/6小鼠为受者、DBA/2小鼠为供者行皮肤移植;同时行C57BL/6小鼠行同种同系皮肤移植做对照。术后1-8周,每周取小鼠脾脏,使用流式细胞仪检测所有受体鼠脾单个核细胞悬液中记忆T细胞的比例（n=10）。结果（1）同种异系皮肤移植组：术后第4周的C57BL/6小鼠脾单个核细胞悬液中记忆T细胞的比例较术后1~3周显著增多（P〈0.01）;术后5~8周的记忆T细胞比例较术后第4周显著增多（P〈0.01）;术后1~3周小鼠记忆T细胞比例无差异（P〉0.05）;术后5~8周小鼠记忆T细胞比例无差异（P〉0.05）。（2）同种同系皮肤移植组：术后8周,每周产生的记忆T细胞比例无差异（P〉0.05）。结论接受同种异系皮肤抗原刺激4~5周后,小鼠记忆T细胞发生稳态增殖,此模型可以稳定的获得小鼠记忆T细胞。     

Immunosuppression in cardiac graft rejection: a human in vitro model to study the potential use of new immunomodulatory drugs

CXCL10-CXCR3 axis plays a pivotal role in cardiac allograft rejection, so that targeting CXCL10 without inducing generalized immunosuppression may be of therapeutic significance in allotransplantation. Since the role of resident cells in cardiac rejection is still unclear, we aimed to establish reliable human cardiomyocyte cultures to investigate Th1 cytokine-mediated response in allograft rejection. We used human fetal cardiomyocytes (Hfcm) isolated from fetal hearts, obtained after legal abortions. Hfcm expressed specific cardiac lineage markers, specific cardiac structural proteins, typical cardiac currents and generated ventricular action potentials. Thus, Hfcm represent a reliable in vitro tool for allograft rejection research, since they resemble the features of mature cells. Hfcm secreted CXCL10 in response to IFNgamma and TNFalphaalpha; this effect was magnified by cytokine combination. Cytokine synergy was associated to a significant TNFalpha-induced up-regulation of IFNgammaR. The response of Hfcm to some currently used immunosuppressive drugs compared to rosiglitazone, a peroxisome proliferator-activated receptor gamma agonist and Th1-mediated response inhibitor, was also evaluated. Only micophenolic acid and rosiglitazone halved CXCL10 secretion by Hfcm. Given the pivotal role of IFNgamma-induced chemokines in Th1-mediated allograft rejection, these preliminary results suggest that the combined effects of immunosuppressive agents and rosiglitazone could be potentially beneficial to patients receiving heart transplants.