Adult Porcine Islet Isolation Using a Ductal Preservation Method and Purification With a Density Gradient Composed of Histidine-Tryptophan-Ketoglutarate Solution and Iodixanol

Background

Given the fragility of adult porcine islets, reduction of shearing stress in islet purification using histidine-tryptophan-ketoglutarate (HTK) solution and iodixanol could be an effective strategy. We examined the effect of ductal preservation with HTK solution and an islet purification protocol that utilizes HTK solution and iodixanol in adult porcine islet isolation.

Methods

Islets were isolated with a modified Ricordi method using adult Prestige World Genetics (PWG) and Yucatan pigs. The discontinuous density gradient was composed of either HTK solution/iodixanol (n = 23, iodixanol group) or Hank's balanced salt solution (HBSS)/Ficoll (n = 17, Ficoll group). In the iodixanol group, ductal injection of HTK solution was performed before purification.

Results

In PWG pigs, significantly higher islet yield after purification (3480 ± 214.2 islet equivalent [IEQ]/g, P = .003) and higher recovery rate (85.45% ± 3.49%, P = .0043) were obtained from the HTK/iodixanol group as compared to the HBSS/Ficoll group (1905 ± 323.2 IEQ/g, and 67.22% ± 4.77%, respectively). Similar results were obtained in Yucatan pigs with greater body weight.

Conclusion

Ductal preservation and iodixanol-based islet purification using HTK solution improved the yield of adult porcine islet isolation compared to the conventional method using HBSS and Ficoll. The results of this study support the feasibility of an adult porcine islet isolation protocol using HTK solution and iodixanol, which have the favorable physical properties.     

Isolation and Purification of Islet Cells From Adult Pigs

We used in situ perfusion and a multiple-organ harvesting technique to collect islets from adult pig pancreata. The tissues were digested with collagenase P followed by purification in a lympholyte discontinuous gradient using a COBE2991 cell separator. The yield and purity of isolated islets were evaluated with a light microscope after dithizone (DTZ) staining. Islet function was assessed using an in vitro insulin release assay. The results showed that before purification 275,000 ± 20,895 islet equivalents (IEQ) were obtained from 1 digested pancreas. After purification with gradient centrifugation, the islet yield was 230,350 ± 26,679 IEQ/pancreas. Each gram of the purified pancreatic tissues yielded 2710 ± 229 IEQ with an average purity of 50.2 ± 2.0%. The purified islet cells responded to stimulation with high glucose concentrations (16.7 mmol/L), namely, 4.74-fold greater than the insulin secretion with exposure to the basal level of glucose (3.3 mmol/L; P < .001). These results suggested that the established isolation method can be applied to large-scale purification of fully functional islets from pig pancreata.     

预防性添加胰蛋白酶抑制剂对成年猪胰岛分离的影响

目的　开发成年猪胰岛分离方法。方法　取成年猪胰体尾部,胰管内注入0.1%冷胶原酶(type Ⅺ)消化液, 在38.5 ℃水箱中消化后,放入4 ℃Hanks液中分离并用600μm的滤过网过滤。残留的组织重新悬浮在冷Hanks液中,并放入Ricordi’s chamber内振荡5 min后再次过滤。胰岛分离分为对照组(n=14)、Pefabloc(胰蛋白酶抑制剂)组(n=8)及FOY(胰蛋白酶抑制剂)组(n=5)。Pefabloc组和FOY组消化液中分别添加1.0 mmol/LPefabloc或FOY。结果　Pefabloc组及FOY组的胰岛收获量分别为(11 848±3 530) 个/g 和(14 496±3 693)个/g,明显高于对照组的(8 505±3 349) 个/g,P<0.05。消化后的消化液胰蛋白酶活性对照组为(114.7±50.0)BAEEU,明显高于胰管内注入前的(4. 0±1. 8) BAEEU 及Pefabloc 组的(5. 5±2. 7) BAEEU(P<0. 01),但Pefabloc组与胰管内注入前却差异无统计学意义。对照组胰岛收获量≥8 000 个/g组的胰蛋白酶活性明显低于收获量<8 000 个/g组的活性〔(78.3±26.7) BAEEU vs (137.5±48.4) BAEEU〕,P<0.05。对照组、Pefabloc组及FOY组纯化后的胰岛对不同浓度葡萄糖显示了良好的胰岛素分泌能力。结论　本实验采用的胰岛分离方法能够获得大量的猪胰岛细胞,而且预防性添加胰蛋白酶抑制剂后进一步稳定地提高了胰岛收获     

Engraftment of Adult Porcine Islet Xenografts in Diabetic Nonhuman Primates Through Targeting of Costimulation Pathways

Recent advances in human allogeneic islet transplantation have established beta-cell replacement therapy as a potentially viable treatment option for individuals afflicted with Type 1 diabetes. Two recent successes, one involving neonatal porcine islet xenografts transplanted into diabetic rhesus macaques treated with a costimulation blockade-based regimen and the other involving diabetic cynomolgus monkeys transplanted with adult porcine islet xenografts treated with an alternative multidrug immunosuppressive regimen have demonstrated the feasibility of porcine islet xenotransplantation in nonhuman primate models. In the current study, we assessed whether transplantation of adult porcine islet xenografts into pancreatectomized macaques, under the cover of a costimulation blockade-based immunosuppressive regimen (CD28 and CD154 blockade), could correct hyperglycemia. Our findings suggest that the adult porcine islets transplanted into rhesus macaques receiving a costimulation blockade-based regimen are not uniformly subject to hyperacute rejection, can engraft (2/5 recipients), and have the potential to provide sustained normoglycemia. These results provide further evidence to suggest that porcine islet xenotransplantation may be an attainable strategy to alleviate the islet supply crisis that is one of the principal obstacles to large-scale application of islet replacement therapy in the treatment of Type 1 diabetes.     

Porcine Endogenous Retroviral Nucleic Acid in Peripheral Tissues Is Associated with Migration of Porcine Cells Post Islet Transplant

Porcine islets represent an alternative source of insulin-producing tissue, however, porcine endogenous retrovirus (PERV) remains a concern. In this study, SCID mice were transplanted with nonencapsulated (non-EC), microencapsulated (EC) or macroencapsulated (in a TheraCyte trade mark device) neonatal porcine islets (NPIs), and peripheral tissues were screened for presence of viral DNA and mRNA. To understand the role of an intact immune system in PERV incidence, mice with established NPI grafts were reconstituted with splenocytes. Peripheral tissues were screened for PERV and porcine DNA using PCR. Tissues with positive DNA were analyzed for PERV mRNA using RT-PCR. No significant difference was observed between non-EC and EC transplants regarding presence of PERV or porcine-specific DNA or mRNA. In reconstituted animals, little PERV or porcine DNA, and no PERV mRNA was detected. No PERV or porcine-specific DNA was observed in animals implanted with a TheraCyte trade mark device. In conclusion, an intact immune system significantly lowered the presence of PERV. Microencapsulation of islets did not alter PERV presence, however, macroencapsulation in the TheraCyte device did. Lower PERV incidence coincided with lower porcine DNA in peripheral tissues, linking the presence of PERV to migration of porcine cells.     

Percoll法分离犬骨髓单个核细胞与体外成骨诱导培养的实验研究

目的建立犬骨髓单个核细胞(Bone marrow mononuclear cells,BMNCs)的分离培养、体外扩增和成骨诱导方法,为骨缺损的修复提供理想的骨组织工程种子细胞。方法用1.063g/ml percoll液分离2.5ml Beagle犬骨髓,利用细胞贴壁筛选法进行分离、培养、扩增和成骨诱导。结果采用1.063g/ml percoll液可获得纯度较高的BMNCs,接种细胞生长良好,平均倍增周期为1d,经成骨诱导培养后可定向分化为成骨细胞。结论采用1.063g/ml percoll液能够较好的进行Beagle犬BMNCs的分离培养和体外扩增,分离得到的细胞具备骨髓基质干细胞(Bone marrow mesenchymal stem cells,BMSCs)的特性。     

Long‐Term Control of Diabetes in Immunosuppressed Nonhuman Primates (NHP) by the Transplantation of Adult Porcine Islets

Pig islets are an alternative source for islet transplantation to treat type 1 diabetes (T1D), but reproducible curative potential in the pig‐to‐nonhuman primate (NHP) model has not been demonstrated. Here, we report that pig islet grafts survived and maintained normoglycemia for >6 months in four of five consecutive immunosuppressed NHPs. Pig islets were isolated from designated pathogen‐free (DPF) miniature pigs and infused intraportally into streptozotocin‐induced diabetic rhesus monkeys under pretreatment with cobra venom factor (CVF), anti‐thymocyte globulin (ATG) induction and maintenance with anti‐CD154 monoclonal antibody and low‐dose sirolimus. Ex vivo expanded autologous regulatory T cells were adoptively transferred in three recipients. Blood glucose levels were promptly normalized in all five monkeys and normoglycemia (90–110 mg/dL) was maintained for >6 months in four cases, the longest currently up to 603 days. Intravenous glucose tolerance tests during the follow‐up period showed excellent glucose disposal capacity and porcine C‐peptide responses. Adoptive transfer of autologous regulatory T cells was likely to be associated with more stable and durable normoglycemia. Importantly, the recipients showed no serious adverse effects. Taken together, our results confirm the clinical feasibility of pig islet transplantation to treat T1D patients without the need for excessive immunosuppressive therapy.     

Pseudotyping of Porcine Endogenous Retrovirus by Xenotropic Murine Leukemia Virus in a Pig Islet Xenotransplantation Model

The potential of porcine endogenous retrovirus (PERV) as a human pathogen, particularly as a public health risk, is a major concern for xenotransplantation. In vitro PERV transmission to human cells is well established. Evidence from human/pig hematopoietic chimeras in immunodeficient mice suggests PERV transmission from pig to human cells in vivo . However, recently Yang et al. demonstrated in such a model that PERV-C, a nonhuman-tropic class, could be transmitted via pseudotyping by xenotropic murine leukemia virus (X-MLV). We developed a mouse pig islet xenotransplant model, where pig and human cells are located in physically separate compartments, to directly assess PERV transmission from a functional pig xenograft. X-MLV efficiently pseudotypes all three classes of PERV, including PERV-A and -B that are known to productively infect human cell lines and PERV-C that is normally not infectious for human cells. Pseudotyping also extends PERV's natural tropism to nonpermissive, nonhuman primate cells. X-MLV is activated locally by the surgical procedure involved in the tissue transplants. Thus, the presence and activation of endogenous X-MLV in immunodeficient mice limits the clinical significance of previous reports of in vivo PERV transmission from pig tissues to human cells.     

Amount and Distribution of Collagen in the Pancreas Have No Effect on Porcine Islet Isolation Outcome

Xenotransplantation of porcine islets of Langerhans is considered to be a possible alternative for clinical islet transplantation. However, porcine islet isolation procedures have been shown to produce highly variable yields between pigs with similar backgrounds. One of the variables that could account for this is the collagen substrate within the pancreas. We determined the amount and distribution of collagen within porcine pancreata as they determined islet isolation outcomes. This study involved the histological examination of 140 porcine pancreata (64 juvenile and 76 adult) and islet isolation from 58 adult organs. To quantify the amount of collagen, tissue samples were stained with Sirius Red. Collagen distribution was determined by assessing the presence of collagen in the endocrine-exocrine interface (the “islet capsule”), in tissue samples double-stained with Sirius Red and anti-insulin. Strong variation in total collagen was observed in both adult and juvenile pigs. The mean collagen content in the juvenile group was significantly lower than that in the adult group. Apparently, the pancreas undergoes a process of fibrosis as pigs age. The vast majority of islets from both adult and juvenile pancreata had no or only a limited collagen capsule. However, islet encapsulation was highly variable between pancreata. We observed no significant correlation between total collagen content or the percentage islet encapsulation and islet yield. Although total collagen content and islet encapsulation show great variability between pancreata, neither the amount nor the distribution of collagen affected porcine islet isolation outcome.     

Superiority of Portal Venous Drainage Over Systemic Venous Drainage in Pancreas Transplantation: A Retrospective Study

OBJECTIVE: To compare portal and systemic venous drainage of pancreas transplants and demonstrate an immunologic and survival superiority of portal venous drainage. SUMMARY BACKGROUND DATA: Traditionally, solitary pancreas transplants have been performed using systemic venous and bladder drainage, but more recently, the advantages of enteric drainage have been well documented. Although physiologic benefits for portal venous drainage have been described, the impact of portal venous drainage, especially with solitary pancreas transplants, has yet to be determined. METHODS: Since August 1995, 280 pancreas transplants with enteric duct drainage were analyzed. One hundred and seventeen were simultaneous pancreas and kidney (SPK), 63 with systemic venous drainage (SV) and 54 with portal venous drainage (PV). The remainder were solitary transplants; 97 pancreas after kidney (PAK; 42 SV and 55 PV) and 66 transplants alone (PTA; 26 SV and 40 PV). Immunosuppressive therapy was equivalent for both groups. RESULTS: The groups were similar with respect to recipient characteristics and HLA matching. Thirty-six month graft survival for all transplants was 79% for PV and 65% for SV (P =.008). By category, SPK graft survival was 74% for PV and 76% for SV, PAK graft survival was 70% for PV and 56% for SV, and PTA graft survival was 84% for PV and 50% for SV. The rate of at least one rejection episode was also significantly higher in the SV group. At 36 months, for all pancreas transplants, the rejection rate was 21% for PV and 52% for SV (P <.0001). For SPK, rejection rates were 9% for PV and 45% for SV. For PAK, rejection rates were 16% for PV and 65% for SV, and for PTA 36% for PV and 51% for SV. The rejection rates for kidneys following SPK were also lower in the PV group (26% versus 43% for SV). Furthermore, the grades of rejection were milder in PV for all transplants (P =.017). By multivariate analysis, portal venous drainage was the only parameter that significantly affected rejection. CONCLUSION: Graft survival and rejection is superior for PV. These clinical findings are consistent with published reports of experimentally induced portal tolerance and strongly argue that PV drainage should be the procedure of choice for pancreas transplantation.     

Bone Density of the Spine and Femur in Adult White Females

We measured bone mineral density (BMD in g/cm²) of the spine (L2-L4) and femur (four regions) in 1472 and 1487 cases, respectively, of ambulatory white women ages 20–79 years in the USA. A DPX densitometer was used in a mobile setting. The BMD values for women up to 69 years corresponded closely with published values for the USA, the UK, and northern Europe; our values were somewhat lower than those from other studies only in women over 70 years. The USA data were combined with data from Europe to give reference curves on about 12,000 subjects. Decreases of BMD with age in women below 50 years were much smaller than in older women (0.2% versus 0.6–1.0% per year). Femoral bone decreased from the neck region, but not the trochanter with age; the decrease of total femur BMD with age was due to loss from the former region. Loss of bone mineral content (BMC in g) from the femur neck and total femur region did not accelerate until after age 50 years, much like the spine. The apparent decrease of BMD in these regions that begins about age 40 actually is due to an increase of bone area. About 20% of USA women aged 50–79 years had BMD levels for the lumbar spine, or for the femur neck, more than −2.5 SD below the average values in young adult women 20–39 years old. Body weight had several times more impact on BMD than height, and in fact, a change of 1 kg in postmenopausal women was commensurate with the effect of a 1-year change in age. Subjects in the lowest quartile of body weight had T-scores that were 1 SD below those in the highest quartile. Received: 10 September 1998 / Accepted: 15 December 1998     

成人肾母细胞瘤（附12例报告）

自１９５８年１月～１９９１年１２月收治成人肾母细胞瘤１２例，均经病理证实，占同期收治的肾恶性肿瘤的２．５３％（１２／４７５）。患者男２例，女１０例。年龄１６～５４岁。临床分期，Ⅰ、Ⅱ期５例（４２％），Ⅲ、Ⅳ期７例（５８％）。症状主要为血尿，腹部肿块，腰腹部疼痛或发热。本组病人以手术加放化疗为主要治疗手段。随访其３、５年生存率均为３３％，２例术后无瘤生存达２０年以上。认为对成人肾母细胞瘤Ⅱ期病例应采取手术加放、化疗的综合治疗，以期提高治愈率     

Bone Mineral Content and Density in the Humerus of Adult Myostatin-Deficient Mice

Myostatin (GDF-8), a member of the transforming growth factor-b superfamily of secreted growth and differentiation factors, is a negative regulator of skeletal muscle growth. We investigated the effects of increased muscle mass on bone morphology by examining bone mineral content and density in the humeri of myostatin-deficient mice. We compared the humeri of 11 mixed-gender, adult mice homozygous for the disrupted myostatin sequence with those from 11 mixed-gender, adult wild-type mice. Body mass, deltoid mass, and triceps mass were recorded from each animal and densitometric and geometric parameters were collected from the humerus using peripheral quantitative computed tomography (pQCT). Cross-sectional slices were scanned at four different positions along the humerus corresponding to 15%, 40%, 60%, and 85% of total humerus length. Results show that the myostatin- deficient mice weigh more than controls and have significantly larger triceps and deltoid muscles. The myostatin-deficient animals also have significantly (P < 0.05) higher trabecular area and trabecular bone mineral content (BMC) in the proximal humerus (15% length) and significantly (P < 0.01) higher cortical BMC, cortical area, and periosteal circumference in the region of the deltoid crest (40% length). The myostatin knockouts otherwise do not differ from controls in cortical BMC. Moreover, experimental and control mice do not differ significantly from one another in cortical bone mineral density (BMD) at any of the sites examined. These results suggest that the effects of increased muscle mass on the mouse humerus are localized to regions where muscles attach; furthermore, these effects include increased mineral content of both trabecular and cortical bone.     

Esophagogastrectomy: Superiority of the Combined Abdominal-Right Thoracic Approach (Lewis Operation)

The advantages of the combined abdominal-right thoracic approach to operating upon carcinoma of the esophagus (Lewis operation) are reviewed; they include elimination of the need for incision of the diaphragm or costal arch; easier mobilization of the esophagus; better visualization of the anastomosis through a high thoracotomy incision; and no interference by the heart and aortic arch.The operation is performed in one stage, using separate abdominal (upper midline) and thoracic (excision of the fourth rib) incisions. A careful two-layer anastomosis is performed using a separate circular opening in the stomach and invaginating the esophagus into the stomach by suturing the gastric serosa to the mediastinal fascia and pleura. Important principles of postoperative care include monitoring in the intensive care unit for five to seven days, use of a sump-type nasogastric tube, and frequent measurement of body weight, blood volume, blood gases, and electrolytes. Colloid infusions are preferred to crystalloid solutions in order to avoid fluid overload. Vigorous nasotracheal suction is important, and early tracheostomy is performed if bronchopulmonary secretions tend to accumulate.This operation was performed on 37 unselected patients during a seven-year period without operative mortality or anastomotic leak. Thirty-three patients had metastases at the time of resection, but all were relieved of dysphagia and the degree of palliation was very encouraging.     

Superiority of Rapamycin Over Tacrolimus in Preserving Nonhuman Primate Treg Half‐Life and Phenotype After Adoptive Transfer

Many critical issues remain concerning how best to deploy adoptive regulatory T cell (Treg) immunotherapy to the clinic. These include a determination of their pharmacokinetic characteristics, their optimal dose, their phenotypic stability and the best therapies with which to pair Tregs. By performing a CFSE‐labeled autologous Treg pulse experiment, we determined that the accessible peripheral blood Treg pool in rhesus macaques is quite large (75 ± 11 × 10⁶ Tregs/kg). Pharmacokinetic analysis revealed that Tregs have two phases of elimination: an α phase, with a T_1/2 in the peripheral blood of 32.4 ± 11.3 h and a β phase with a T_1/2 of 120.4 ± 19.7 h. In addition to their short initial half‐life, Tregs underwent rapid phenotypic shifts after infusion, with significant loss of both CD25 and FoxP3 by day +6. While tacrolimus stabilized CD25 expression, it did not improve T_1/2, nor mitigate the loss of FoxP3. In contrast, rapamycin significantly stabilized both CD25 and FoxP3, and supported an increased half‐life, with an α phase of 67.7 ± 6.9 h and a β phase of 252.1 ± 54.9 h. These results suggest that rapamycin may be a necessary addition to Treg immunotherapy, and that tacrolimus may be deleterious to Treg integrity posttransfer.