Implantation of decellularized small-caliber vascular xenografts with and without surface heparin treatment

Heparin treatment of decellularized xenografts has been reported to reduce graft thrombogenicity. However, little is known about the in vivo comparison of heparin-treated with non-heparin-treated xenografts, especially for small-caliber vascular implants. We implanted either a heparin-treated or a non-heparin-treated canine carotid artery as bilateral carotid xenograft in rabbits (n = 24). Small-caliber xenografts (3 approximately 4 mm) were decellularized by enzymatic and detergent extraction and were further covalently linked with heparin. During implantation, thrombosis rate was 4% in the heparin-treated xenografts and 25% in the non-heparin-treated xenografts after 3 weeks (P < 0.05). After 6 months, it was 8 versus 58%, respectively (P < 0.01). Both heparin-treated and non-heparin-treated xenografts harvested at the end of 3 and 6 months showed a satisfactory cellular reconstruction of either smooth muscle cells or endothelial cells. These results indicate that heparin treatment of the small-caliber decellularized xenograft reduces the in vivo thrombogenicity. Both heparin-treated and non-heparin-treated xenografts seem to undergo a similar cellular remodeling process up to 6 months.     

1 α-Hydroxyvitamin D<Subscript>2</Subscript> inhibits growth of human neuroblastoma

Neuroblastoma is the most common extracranial solid tumor in childhood. The poor outcomes of patients with high-risk neuroblastoma have encouraged the search for new therapies. In the current study, the effect of the vitamin D analog 1α-hydroxyvitamin D₂ (1α-OH-D₂, doxercalciferol) was assessed in a mouse xenograft model of human neuroblastoma. Vitamin D receptor (VDR) expression levels in seven neuroblastoma cell lines were compared using real-time PCR. SK-N-AS cells, which express relatively high levels of VDR, were injected into the flanks of 60 mice. The mice were treated daily via oral gavage for 5 weeks with vehicle (control), 0.15 μg, or 0.3 μg of 1α-OH-D₂. The animals were then euthanized, and tumors, sera, and kidneys were collected and analyzed. End tumor volumes were significantly smaller in both the 0.15 μg group (712.07 mm³, P = 0.0121) and 0.3 μg group (772.97 mm³, P = 0.0209) when compared to controls (1,681.75 mm³). In terms of toxicity, serum calcium levels were increased but mortality was minimal in both treatment groups. These results were similar to those previously described in the transgenic (LHβ-Tag) and human xenograft (Y-79) models of retinoblastoma, a related tumor. In vitro cell viability studies of SK-N-AS and NGP cells, which represent two major human neuroblastoma subtypes that differ in their genetic abnormalities as well as their VDR expression levels, show that both are sensitive to calcitriol, the active metabolite of vitamin D₃. In conclusion, the present study shows that 1α-OH-D₂ can inhibit human neuroblastoma growth in vivo with relatively low toxicity. The safety of 1α-OH-D₂ has been extensively studied; the drug is FDA-approved for the treatment of adult kidney patients, and Phase I/II trials have been conducted in adult oncology patients. There should not be major obstacles to starting Phase I and II clinical trials with this drug in pediatric patients with high-risk neuroblastoma.     

供体血管内皮细胞对小鼠-大鼠移植心脏存活时间的影响

目的 探讨供体血管内皮细胞对小鼠-大鼠移植心脏存活时间的影响.方法 分离小鼠血管内皮细胞并于移植前14 d注入大鼠阴茎背静脉2×106细胞/只或联合注射环磷酰胺20 mg/kg·d.异位小鼠-大鼠心脏移植后观察供心存活时间. 结果 成功分离小鼠血管内皮细胞,注射小鼠血管内皮细胞14 d后,移植心脏平均存活时间(10±1.414)min, 组化染色显示供心有IgM、C3沉积,血浆IgM、IgG、C3、C4较未注射血管内皮细胞组明显增高;联合使用环磷酰胺能延长供心成活时间(19.44±2.603 4)min(t=2.880,P ＜ 0.01).结论 外周静脉注射供体血管内皮细胞不能诱导延迟性异种移植排斥反应(DXR)的免疫耐受,却促使发生HAR.联合环磷酰胺可延长供心存活时间.     

Accommodation in allogeneic and xenogeneic organ transplantation: Prevalence,impact, and implications for monitoring and for therapeutics

Accommodation refers to acquired resistance of organs or tissues to immune or inflammatory reactions that might otherwise cause severe injury or rejection. As first observed in ABO-incompatible kidney transplants and heterotopic cardiac xenografts, accommodation was identified when organ transplants continued to function despite the presence of anti-graft antibodies and/or other reactants in the blood of recipients. Recent evidence suggests many and perhaps most organ transplants have accommodation, as most recipients mount B cell responses specific for the graft. Wide interest in the impact of graft-specific antibodies on the outcomes of transplants prompts questions about which mechanisms confer protection against such antibodies, how accommodation might be detected and whether and how rejection could be superimposed on accommodation. Xenotransplantation offers a unique opportunity to address these questions because immune responses to xenografts are easily detected and the pathogenic impact of immune responses is so severe. Xenotransplantation also provides a compelling need to apply these and other insights to decrease the intensity and toxicity of immunosuppression that otherwise could limit clinical application.     

Transitioning of renal transplant pathology from allograft to xenograft and tissue engineering pathology: Are we prepared?

Currently, the most feasible and widely practiced option for patients with end-stage organ failure is the transplantation of part of or whole organs, either from deceased or living donors. However, organ shortage has posed and is still posing a big challenge in this field. Newer options being explored are xenografts and engineered/bioengineered tissues/organs. Already small steps have been taken in this direction and sooner or later, these will become a norm in this field. However, these developments will pose different challenges for the diagnosis and management of problems as compared with traditional allografts. The approach to pathologic diagnosis of dysfunction in these settings will likely be significantly different. Thus, there is a need to increase awareness and prepare transplant diagnosticians to meet this future challenge in the field of xenotransplantation/ regenerative medicine. This review will focus on the current status of transplant pathology and how it will be changed in the future with the emerging scenario of routine xenotransplantation.     

滋阴补脾方对人结肠癌裸鼠移植瘤的抑制作用机制研究

目的：探讨滋阴补脾方对人结肠癌裸鼠移植瘤的抑制作用机制。方法：4周龄BALB/c雌性裸鼠20只，制备人结肠癌裸鼠模型，按照随机数字表法分随机分为4组，每组5只。对照组注射等量生理盐水，化疗药物组腹腔注射氟尿嘧啶，中成药组灌胃中药汤剂10 mL，联合用药组：每只裸鼠腹腔注射氟尿嘧啶联合灌胃中药汤剂。1次/d，均连续应用4 d，至第14天处死动物收集标本。测量各组肿瘤重量、肿瘤体积和体积抑瘤率；采用蛋白质印迹法测定CD113、CD116和P53蛋白表达。结果：与对照组比较，化疗药物组、中成药组和联合用药组肿瘤重量、肿瘤体积、CD113和CD116表达明显降低，肿瘤体积抑瘤率和P53表达明显升高（P<0.05）；化疗药物组和联合用药组肿瘤重量、肿瘤体积、CD113和CD116表达低于中成药组，肿瘤体积抑瘤率和P53表达高于中成药组（P<0.05）；联合用药组肿瘤重量、肿瘤体积、CD113和CD116表达低于化疗药物组，肿瘤体积抑瘤率和P53表达高于化疗药物组（P<0.05）。结论：滋阴补脾法可抑制人结肠癌HT29裸鼠移植瘤生长，认为其机制可能与下调CD113和CD116表达及上调P53表达有关。