Tissue culture of human fetal pancreas. Development and function of B-cells in vitro and transplantation of explants to nude mice

Clinical Islet Xenotransplantation: Development of Isolation Protocol, Anti-Rejection Strategies, and Clinical Outcomes

Allogeneic islet transplantation has become a standard therapy for unstable type 1 diabetes. However, considering the large number of type 1 diabetic patients, the shortage of donors is a serious issue. To address this issue, clinical islet xenotransplantation is conducted. The first clinical islet xenotransplantation was performed by a Swedish team using fetal pancreatic tissue. Thereafter, clinical trials of islet xenotransplantation were conducted in New Zealand, Russia, Mexico, Argentina, and China using neonatal pig islets. In clinical trials, fetal or neonatal pancreata are used because of the established reliable islet isolation methods. These trials demonstrate the method's safety and efficacy. Currently, the limited number of source animal facilities is a problem in terms of promoting islet xenotransplantation. This limitation is due to the high cost of source animal facilities and the uncertain future of xenotransplantation. In the United States, the first xenogeneic heart transplantation has been performed, which could promote xenotransplantation. In Japan, to enhance xenotransplantation, the 'Medical Porcine Development Association' has been established. We hope that xenogeneic transplantation will become a clinical reality, serving to address the shortage of donors.

Frederick Banting's actual great idea: The role of fetal bovine islets in the discovery of insulin

BACKGROUND

Frederick Banting approached Toronto physiology professor JJR Macleod with a way to prevent pancreatic trypsin from destroying the pancreas' internal secretion. Banting proposed to induce exocrine atrophy by ligating canine pancreatic ducts and to use extracts of islet-rich residua to treat pancreatectomized dogs. His next plan was to make extracts from fetal pancreas, which he had read was islet-rich and lacked exocrine tissue capable of making trypsin; this work has not been historically evaluated.

METHODS

Banting's fetal calf pancreas story is told using primary and secondary historical sources and then critically examined using both historical and recent data on species phylogeny, islet ontogeny, fetal/neonatal islet culture/transplantation, etc. Results/Discussion: Only ruminants develop dual islets populations sequentially; fetal calf pancreata, at the gestational ages Banting used, possess numerous insulin-rich giant peri-lobular islets, which credibly explain the potency of his fetal calf insulin extract. Use of non-ruminant fetal pancreata would have failed.

Characterization of neural crest-derived stem cells isolated from human bone marrow for improvement of transplanted islet function

Background: Murine boundary cap-derived neural crest stem cells (NCSCs) are capable of enhancing islet function by stimulating beta cell proliferation as well as increasing the neural and vascular density in the islets both in vitro and in vivo. This study aimed to isolate NCSC-like cells from human bone marrow.Methods: CD271 magnetic cell separation and culture techniques were used to purify a NCSC-enriched population of human bone marrow. Analyses of the CD271+ and CD271- fractions in terms of protein expression were performed, and the capacity of the CD271+ bone marrow cells to form 3-dimensional spheres when grown under non-adherent conditions was also investigated. Moreover, the NCSC characteristics of the CD271+ cells were evaluated by their ability to migrate toward human islets as well as human islet-like cell clusters (ICC) derived from pluripotent stem cells.Results: The CD271+ bone marrow population fulfilled the criterion of being multipotent stem cells, having the potential to differentiate into glial cells, neurons as well as myofibroblasts in vitro. They had the capacity to form 3-dimensional spheres as well as an ability to migrate toward human islets, further supporting their NCSC identity. Additionally, we demonstrated similar migration features toward stem cell-derived ICC.Conclusion: The results support the NCSC identity of the CD271-enriched human bone marrow population. It remains to investigate whether the human bone marrow-derived NCSCs have the ability to improve transplantation efficacy of not only human islets but stem cell-derived ICC as well.

Production, Characterization, and Function of Pseudoislets from Perinatal Canine Pancreas

We evaluated the cell composition and function of canine pancreatic pseudoislets (PIs) produced from 42- to 55-day-old fetuses, 1- to 21-day-old pups, and an adult dog pancreas. After mild collagenase treatment, partially digested tissues were cultured for 2–3 weeks. PI production started on culture day 3, was marked for 6 to 9 days, and then stopped. PI production was greatest with the neonatal specimens, reaching about 12 million aggregates per litter (55-day-old fetus) or per pancreas (1-day-old pup). Cell composition at all stages was similar to that in adult pancreatic islets, with predominant β cells, scant α cells and, most importantly, presence of δ cells. Among pancreatic markers assessed by quantitative real-time PCR (qRT-PCR) mRNA assay, insulin showed the highest expression levels in PIs from newborn and adult pancreas, although these were more than 1000 times lower than in adult islets. Pdx1 mRNA expression was high in PIs from 55-day-old pancreases and was lower at later stages. Consistent with the qRT-PCR results, the insulin content was far lower than reported in adult dog pancreatic islets. However, insulin release by PIs from 1-day-old pups was demonstrated and was stimulated by a high-glucose medium. PIs were transplanted into euglycemic and diabetic SCID mice. In euglycemic animals, the transplant cell composition underwent maturation and transplants were still viable after 6 months. In diabetic mice, the PI transplants produced insulin and partially controlled the hyperglycemia. These data indicate that PIs can be produced ex vivo from canine fetal or postnatal pancreases. Although functional PIs can be obtained, the production yield is most likely insufficient to meet the requirements for diabetic dog transplantation without further innovation in cell culture amplification.

Fetal Islet Cell Transplants: Promises and Limits of the Experience in the Eastern Countries

The fetal pancreas is a potential source of islet ceils for transplantation. Despite marked advances in experimental islet grafting over the past two decades, successful clinical fetal transplantation seems to be very rare. The possible reasons for the failure of this transplantation are discussed. The review summarizes the development of a method for the isolation of fetal tissue, and the factor influencing the growth and differentiation of isolated fetal islets prior to and after transplantation. Finally, a brief overview is given of the status of clinical human pancreatic transplantation and a possible key to successful grafting.

Production and Characterization of Fetal Sheep Pancreatic Islet-Like Cell Clusters

Explants of fetal sheep pancreas transplanted into diabetic athymic mice survive for many months but there is only partial differentiation of the endocrine cells. As an alternative form of graft we examined the possibility of creating islet-like cell clusters (ICCs) by collagenase digestion of the fetal sheep pancreas, as has been described for human and porcine fetal pancreas. Such ICCs did form at the rate of 6-23 per 10 mg pancreas; their size varied between 65 and 474 μm (median 232 μm) and their insulin content was 1.6 ± 0.2 mU per 20 ICCs. Laser scanning confocal analysis showed that 4.6 ± 0.7% of the cells contained insulin. Insulin was secreted from ICCs maintained in culture at the daily rate of 2.5 mU per 30 ICCs. Arginine but not glucose or theophylline enhanced acute insulin secretion in vitro. Transplantation of up to 1000 ICCs into athymic and scid mice resulted in sparse growth of the epithelial-like cells in the graft and only partial differentiation of the endocrine cells. Hyperglycaemia in diabetic recipients was not normalized. Thus, while functioning ICCs can be created from fetal sheep pancreas, they do not appear to be appropriate for transplantation to reverse diabetes in mice.

New tools for experimental diabetes research: Cellular reprogramming and genome editing

Isolated human islets are a rare and precious material for diabetes research. However, their availability is limited, and it is impossible to obtain them from patients with specific genotypes. Human pluripotent stem cells provide an alternative. Induced pluripotent stem cells can be generated from any individual's somatic cells and differentiated into pancreatic cells. Currently, this approach is limited by the immaturity of the islet-like cells derived from stem cells. However, this approach can already be used to model developmental defects, and the possibilities for studying insulin secretion are continuously improving. In addition, genome editing using the CRISPR/Cas9 technology provides powerful possibilities to study the impact of specific genotypes. The same technology can also be used for transcriptional regulation in order to improve the functional maturation of stem cell-derived islets. These tools are today becoming available for tomorrow's translational diabetes research.

Gut microbiota in health and disease

Gut microbiota is an assortment of microorganisms inhabiting the length and width of the mammalian gastrointestinal tract. The composition of this microbial community is host specific, evolving throughout an individual's lifetime and susceptible to both exogenous and endogenous modifications. Recent renewed interest in the structure and function of this "organ" has illuminated its central position in health and disease. The microbiota is intimately involved in numerous aspects of normal host physiology, from nutritional status to behavior and stress response. Additionally, they can be a central or a contributing cause of many diseases, affecting both near and far organ systems. The overall balance in the composition of the gut microbial community, as well as the presence or absence of key species capable of effecting specific responses, is important in ensuring homeostasis or lack thereof at the intestinal mucosa and beyond. The mechanisms through which microbiota exerts its beneficial or detrimental influences remain largely undefined, but include elaboration of signaling molecules and recognition of bacterial epitopes by both intestinal epithelial and mucosal immune cells. The advances in modeling and analysis of gut microbiota will further our knowledge of their role in health and disease, allowing customization of existing and future therapeutic and prophylactic modalities.

Anatomical and histological observation on the pancreas in adult zebrafish

OBJECTIVES

To investigate the anatomic structure of the pancreas and the distribution of the islets in adult zebrafish.

METHODS

In situ immunofluorescent staining, electron microscopy, and serial paraffin-embedded sectioning with hematoxylin/eosin staining were applied.

RESULTS

The pancreas along the intestine included 4 relatively independent and concentrated lobes, in which 4 kinds of islets-principal islets, Brockmann bodies, diffusely existing islets, and single beta-cell-were observed. Some islets contained both alpha and beta cells, whereas some contained only beta cells. The islet number in each adult zebrafish averaged 84.53 +/- 43.77; and the lower quartile, median, and upper quartile were 55.25, 70.50, and 112.00, respectively (n = 40). The different islets were differently distributed in the 4 pancreatic lobes with statistical significance (P < 0.05). Meanwhile, 3 kinds of secretory granules were found in the cytoplasm of different islet cells.

CONCLUSIONS

According to the distinct distribution, concentration of the pancreas, and different contents of the islets within the pancreas, 4 lobes of the pancreas along the intestine-the gallbladder-spleen lobe, the middle lobe, the left lobe, and the ventral lobe-were identified in adult zebrafish.

Characterization of human islet-like structures generated from pancreatic precursor cells in culture

This study addresses the characterization of human islet-like structures generated from a newly discovered sparse population of precursor cells (Petropavlovskaia and Rosenberg, 2002) in the human pancreas. These cells may be progenitor cells capable of producing pancreatic cells suitable for the treatment of type 1 diabetes. The cells were cultured successfully in non-adherent stationary cultures and yielded, as an important first step, a 1.9-fold expansion in a serum-free medium developed specifically for this cell type. This expanded population grew as pancreatic cell aggregates, which were analyzed for islet-like characteristics. Specifically, through RT-PCR analyses and functionality assays, we show that cells within the population expressed all four of the endocrine hormone genes and proteins (insulin, glucagon, somatostatin, pancreatic polypeptide). As well, the expanded pancreatic precursor cell population exhibited glucose responsiveness although the produced cells appeared to be still primitive in nature.

Development and retroviral transduction of porcine neonatal pancreatic islet cells in monolayer culture

To learn more about the potential of neonatal porcine pancreatic duct and islet cells for xenotransplantation, the development of these cells when cultured as monolayers was evaluated. Immunostaining for islet hormones and cytokeratin-7 revealed that day eight monolayers consisted of approximately 70% duct cells and less than 10% beta cells. Using Ki-67 immunostaining as a proliferation marker, the fraction of beta cells in the cell cycle was shown to decrease from 20% at day three to 10% at day eight, and for duct cells from 36 to 19%. Insulin secretion increased 2.4-fold upon glucose stimulation, and 38-fold when 10 mm theophylline was added, showing the responsiveness of the neonatal beta cells. Reaggregated monolayers consisted mostly of duct cells, but 4 weeks after transplantation, grafts contained predominantly endocrine cells, with duct cells being almost absent, suggesting in vivo differentiation of duct cells to endocrine cells. Monolayer susceptibility to retroviral transduction was also investigated using a Moloney Murine Leukemia Virus-based vector. Approximately 60% of duct cells but less than 5% of beta cells expressed the transgene, indicating that precursor duct cells are better targets for transgene expression. These results show that porcine neonatal pancreatic cells can be cultured as monolayers in preparation for transplantation. Furthermore, in such a culture setting, precursor duct cells have a high rate of proliferation and are more efficiently transduced with a retrovirus-based reporter gene than are beta cells.

Adult porcine islet transplantation in baboons treated with conventional immunosuppression or a non-myeloablative regimen and CD154 blockade

The aim of the present study was to assess the survival of adult porcine islets transplanted into baboons receiving either (I) conventional triple drug immunosuppressive therapy or (2) a non-myeloablative regimen and an anti-CD154 monoclonal antibody (mAb) aimed at tolerance-induction. Group 1 baboons (n = 3) were pancreatectomized prior to intraportal injection of 10,000 porcine islet equivalents (IE)/kg and immunosuppressed with anti-thymocyte globulin (ATG), cyclosporine and azathioprine. In Group 2 (n = 2), non-pancreatectomized baboons underwent induction therapy with whole body and thymic irradiation, and ATG. Extracorporeal immunoadsorption (EIA) of anti-Galalpha1,3Gal (Gal) antibody was carried out. Maintenance therapy was with cobra venom factor, cyclosporine. mycophenolate mofetil, methylprednisolone and anti-CD154 mAb. Porcine islets were injected intraportally (14,000 and 32,000 IE/kg, respectively) and high-dose pig mobilized peripheral blood progenitor cells (3 x 10(10) cells/kg) were infused into a systemic vein. Porcine islets were also implanted in the sternomastoid muscle to facilitate subsequent biopsies. In both groups. porcine C-peptide was measured, and histological examination of liver or sternomastoid muscle biopsies was performed at regular intervals. In Group 1, total pancreatectomy reduccd human C-peptide to < 0.1 ng/ml and induced insulin-requiring diabetes. The transplantation of porcine islets was followed by normalization of glycemia for 15-24 h. Porcine C-peptide was detected only transiently immediately after porcine islet injection (maximum 0.12 ng/ml). Histological examination of liver biopsies taken between days 2 and 19 did not reveal viable islets, but necrotic cell structures with mononuclear cell infiltrates were identified in portal venules. In Group 2, injection of porcine islets into non-pancreatectomized recipients induced a transient hypoglycemia (2-4 h) requiring concentrated intravenous dextrose administration. Porcine C-peptide was detectable for 5 and 3 days (maximum 2.8 and 1.0 ng/ml), respectively. Baboon #4 died on day 12 from small bowel intussusception. Liver and sternomastoid muscle biopsies showed well-preserved porcine islets, staining positive for insulin and glucacon, without signs of rejection. In baboon #5, viable islets were detected in the sternomastoid muscle biopsy on day 14, but not on day 28 or thereafter. A progressive mononuclear cell and macrophage infiltration was seen in the biopsies. In conclusion, conventional immunosuppression allowed survival of porcine islets in baboons for < 24 h. The non-myeloablative regimen prolonged survival of porcine islets for > 14 days. However, despite depletion of T cells, anti-Gal antibody and complement, and CD154-hlockade, porcine islets were rejected by day 28. These results suggest that powerful innate immune responses are involved in rejection of discordant xenogencic islets.

A large-animal model to evaluate the clinical potential of fetal pig pancreas fragment transplantation

The long-term goal of this study is to assess the feasibility of using fetal pig pancreas fragment (FPPF) transplantation to treat patients with type I diabetes. Using the highly inbred Westran Pigs, our initial aim was to establish a rejection-free transplant model of FPPF grafted into sibling recipient pigs without immunosuppression. FPPFs were isolated from 80-100-day-old fetuses of either Westran Pigs or outbred pigs and transplanted into the thymus, spleen, liver, or kidney of the recipient Westran pig. Biopsies were taken from each transplant site at set time points and assessed histologically for islet viability, rejection, and endocrine function. Fifty-eight fetal donors were used to transplant 16 recipient pigs. A nonspecific inflammation was seen for both outbred and inbred FPPF donor tissue at day 3 and was considered a response to ischemic necrosis. However, all the transplanted outbred FPPF donor tissue was acutely rejected and lost by day 10-14. In contrast, inbred FPPF tissue showed little evidence of graft necrosis after 3 days, and growth and formation of epithelial islet cell nest-like structures were seen to 28 days after transplantation. With time after transplantation, increasing amounts of insulin immunoperoxidase staining was seen together with chromogranin and somatostatin staining. In summary, this study confirms the potential of the Westran pig to answer the unproven ability of fetal pancreatic tissue to reverse type I diabetes in a large animal model.

A role for activin A and betacellulin in human fetal pancreatic cell differentiation and growth

Activin A (Act.A), a member of the transforming growth factor beta family of secreted proteins, has been implicated in the regulation of growth and differentiation of various cell types. Betacellulin (BTC), a member of the epidermal growth factor family, converts exocrine AR42J cells to insulin-expressing cells when combined with Act.A. We have used primary cultures of human fetal pancreatic tissue to identify the effects of Act.A and/or BTC on islet development and growth. Exposure to Act.A resulted in a 1.5-fold increase in insulin content (P < 0.005) and a 2-fold increase in the number of cells immunopositive for insulin (P < 0.005). The formation of islet-like cell clusters, containing mainly epithelial cells, during a 5-day culture, was stimulated 1.4-fold by BTC (P < 0.05). BTC alone caused a 2.6-fold increase in DNA synthesis (P < 0.005). These data suggest that Act.A induces endocrine differentiation, whereas BTC has a mitogenic effect on human undifferentiated pancreatic epithelial cells.

Expression and function of alpha(v)beta(3) and alpha(v)beta(5) integrins in the developing pancreas: roles in the adhesion and migration of putative endocrine progenitor cells

Cell-cell and cell-matrix interactions play a critical role in tissue morphogenesis and in homeostasis of adult tissues. The integrin family of adhesion receptors regulates cellular interactions with the extracellular matrix, which provides three-dimensional information for tissue organization. It is currently thought that pancreatic islet cells develop from undifferentiated progenitors residing within the ductal epithelium of the fetal pancreas. This process involves cell budding from the duct, migration into the surrounding mesenchyme, differentiation, and clustering into the highly organized islet of Langerhans. Here we report that alpha(v)beta(3) and alpha(v)beta(5), two integrins known to coordinate epithelial cell adhesion and movement, are expressed in pancreatic ductal cells and clusters of undifferentiated cells emerging from the ductal epithelium. We show that expression and function of alpha(v)beta(3) and alpha(v)beta(5) integrins are developmentally regulated during pancreatic islet ontogeny, and mediate adhesion and migration of putative endocrine progenitor cells both in vitro and in vivo in a model of pancreatic islet development. Moreover, we demonstrate the expression of fibronectin and collagen IV in the basal membrane of pancreatic ducts and of cell clusters budding from the ductal epithelium. Conversely, expression of vitronectin marks a population of epithelial cells adjacent to, or emerging from, pancreatic ducts. Thus, these data provide the first evidence for the contribution of integrins alpha(v)beta(3) and alpha(v)beta(5) and their ligands to morphogenetic events in the human endocrine pancreas.

KSA antigen Ep-CAM mediates cell-cell adhesion of pancreatic epithelial cells: morphoregulatory roles in pancreatic islet development

Cell adhesion molecules (CAMs) are important mediators of cell-cell interactions and regulate cell fate determination by influencing growth, differentiation, and organization within tissues. The human pancarcinoma antigen KSA is a glycoprotein of 40 kD originally identified as a marker of rapidly proliferating tumors of epithelial origin. Interestingly, most normal epithelia also express this antigen, although at lower levels, suggesting that a dynamic regulation of KSA may occur during cell growth and differentiation. Recently, evidence has been provided that this glycoprotein may function as an epithelial cell adhesion molecule (Ep-CAM). Here, we report that Ep-CAM exhibits the features of a morphoregulatory molecule involved in the development of human pancreatic islets. We demonstrate that Ep-CAM expression is targeted to the lateral domain of epithelial cells of the human fetal pancreas, and that it mediates calcium-independent cell-cell adhesion. Quantitative confocal immunofluorescence in fetal pancreata identified the highest levels of Ep-CAM expression in developing islet-like cell clusters budding from the ductal epithelium, a cell compartment thought to comprise endocrine progenitors. A surprisingly reversed pattern was observed in the human adult pancreas, displaying low levels of Ep-CAM in islet cells and high levels in ducts. We further demonstrate that culture conditions promoting epithelial cell growth induce upregulation of Ep-CAM, whereas endocrine differentiation of fetal pancreatic epithelial cells, transplanted in nude mice, is associated with a downregulation of Ep-CAM expression. In addition, a blockade of Ep-CAM function by KS1/4 mAb induced insulin and glucagon gene transcription and translation in fetal pancreatic cell clusters. These results indicate that developmentally regulated expression and function of Ep-CAM play a morphoregulatory role in pancreatic islet ontogeny.

Experimental transplantation of human fetal and adult pancreatic islets

We examined morphology and function following transplantation of human fetal islet-like clusters (ICCs) in nude mice and compared the functional efficiency of human adult islets and fetal ICCs after transplantation. To assess the optimal site we first transplanted ICCs under the kidney capsule, pancreas, lung, and liver in nude mice. Grafts to the kidney and pancreas matured functionally and morphologically, as evidenced by a 4-fold increase in C peptide after glucose stimulation and the presence of insulin in the grafts of all animals. Grafts to the lung, liver, and spleen did poorly; C peptide was only measurable in two of eight, two of five, or three of five of mice grafted to the lung, liver, or spleen, respectively. Using chemically diabetic nude rats as recipients, we were able to restore normoglycemia using 15,000 ICCs/kg. Lastly, when transplanted under the kidney capsule of normal nude mice, ICCs had significantly higher insulin contents and C peptide release than equivalent grafts of adult islets. In summary, ICCs are an efficient source of insulin-producing cells of potential use in clinical transplantation. In nude mice, both the kidney and the pancreas provide suitable environments for the growth and maturation of undifferentiated human beta-cells.

Phosphatidylinositol 3-kinase is a negative regulator of cellular differentiation

Phosphatidylinositol 3-kinase (PI3K) has been shown to be an important mediator of intracellular signal transduction in mammalian cells. We show here, for the first time, that the blockade of PI3K activity in human fetal undifferentiated cells induced morphological and functional endocrine differentiation. This was associated with an increase in mRNA levels of insulin, glucagon, and somatostatin, as well as an increase in the insulin protein content and secretion in response to secretagogues. Blockade of PI3K also increased the proportion of pluripotent precursor cells coexpressing multiple hormones and the total number of terminally differentiated cells originating from these precursor cells. We examined whether any of the recently described modulators of endocrine differentiation could participate in regulating PI3K activity in fetal islet cells. The activity of PI3K was inversely correlated with the hepatocyte growth factor/scatter factor-induced downregulation or nicotinamideinduced upregulation of islet-specific gene expression, giving support to the role of PI3K, as a negative regulator of endocrine differentiation. In conclusion, our results provide a mechanism for the regulation of hormone-specific gene expression during human fetal neogenesis. They also suggest a novel function for PI3K, as a negative regulator of cellular differentiation.

Expression of glucokinase in glucose-unresponsive human fetal pancreatic islet-like cell clusters

Glucokinase (GK) is the glucose sensor in the adult beta-cell, resulting in fuel for insulin synthesis and secretion. Defects in this enzyme in the beta-cell are responsible for the genetic disorder maturity-onset diabetes of the young, with the beta-cell being unable to secrete insulin appropriately when challenged with glucose. The human fetal beta-cell is also unable to secrete insulin when exposed to glucose, but whether GK is present and functional in this developing cell is unknown. To determine the expression of GK in human fetal pancreatic tissue, cytosolic protein was extracted from human fetal islet-like cell clusters (ICCs) at 17-19 weeks gestation and examined for protein content and enzyme activity. On Western blots, a single band corresponding to GK was seen at 52 kDa, and this was similar to that obtained from human adult islets. The maximal velocity (Vmax) of GK was less in fetal ICCs than that in adult islets (8.7 vs. 20.7 nmol/mg protein x h); similar K(m) values were found in both ICCs and islets. No attempt was made to determine which cells in an ICC contained GK. Glucose utilization was determined radiometrically; the Vmax of the high K(m) component was less in ICCs than in islets (31.3 pmol/ICC x h vs. 101.4 pmol/islet.h). Culture of ICCs for 3-7 days in medium containing 11.2 mmol/L glucose resulted in a 3.7-fold increase in the Vmax of GK and a 1.8-fold increase in glucose utilization. These enhanced activities of glucose phosphorylation and glycolysis, however, did not lead to the beta-cell being able to secrete insulin when exposed to glucose. In conclusion, glucokinase is present and functional in human fetal ICCs, but the inability of the human fetal beta-cell to secrete insulin in response to an acute glucose challenge is not due to immaturity of this enzyme.

Morphology and function of cultured human fetal pancreatic cells transplanted into athymic mice: a longitudinal study

Islet-like cell clusters generated from human fetal pancreases between 18-24 wk gestation were able to grow and mature both morphologically and functionally after transplantation under the kidney capsule of athymic nude mice. Grafted tissue, predominantly ductal in appearance was unresponsive to glucose 2 wk after grafting. The tissue assumed the trabecular column-like architecture of adult islets by 3 mo, with a concomitant 3-4-fold increase in serum human C-peptide concentration after glucose challenge. Moreover, at that time the surface area of insulin containing cells in the graft increased 20-fold over the starting material. Exocrine components, identified by their characteristic eosinophilic secretory granules were also identified at this time. Transplanted cell clusters were capable of releasing C-peptide for at least 12 mo, when the experiment was terminated. At this time, 1 yr posttransplantation, although the proportion of insulin containing cells in the graft remained unchanged from that measured at 4 mo, a reduction in the magnitude of the C-peptide response to glucose was observed; this finding coincided with a significant mononuclear infiltrate in some areas of the transplanted tissue. In summary, human fetal pancreatic cells grown in tissue culture as cell aggregates, after transplantation under the kidney capsule, remain functionally viable for virtually the life span of immunocompromised rodents. Because of their long-term viability, the use of islet-like cell clusters is a potentially useful method to expand transplantable cells.

Differential integrin expression facilitates isolation of human fetal pancreatic epithelial cells

We have studied the expression of the beta 1 family of integrins in fetal and adult human pancreas. Immunohistochemical staining with a monoclonal anti-beta 1 antibody revealed that the epithelial cells of the human fetal pancreas express high amounts of beta 1 integrin, while the pancreatic stromal cells express substantially lower amounts. Islets of Langerhans from human adult pancreas also expressed high amounts of beta 1 integrin. Taking advantage of the extremely high affinity binding between the invasin protein of Yersinia pseudotuberculosis and many beta 1 integrins, we have been able to isolate highly enriched populations of fetal pancreatic epithelial cells. Epithelial-enriched cell populations retain the ability to differentiate into mature endocrine cells following transplantation into nude mice.

Human fetal tissue research: practice, prospects, and policy

Tissue from human fetal cadavers has long been used for medical research, experimental therapies, and various other purposes. Research within the last two decades has led to substantial progress in many of these areas, particularly in the application of fetal tissue transplantation to the treatment of human disease. As a result, clinical trials have now been initiated at centers around the world to evaluate the use of human fetal tissue transplantation for the therapy of Parkinson's disease, insulin-dependent diabetes mellitus, and a number of blood, immunological and, metabolic disorders. Laboratory studies suggest a much wider range of disorders may in the future be treatable by transplantation of various types of human fetal tissue. A combination of characteristics renders fetal tissue uniquely valuable for such transplantation, as well as for basic research, the development of vaccines, and a range of other applications. Although substitutes for human fetal tissue are being actively sought, for many of these applications there are at present no satisfactory alternatives. Important issues remain unresolved concerning the procurement, distribution, and use of human fetal cadaver tissue as well as the effects of such use on abortion procedures and incidence. These issues can be addressed by the introduction of appropriate guidelines or legislation, and need not be an impediment to legitimate research and therapeutic use of fetal tissue.

Development of a method for embedded-culture of pig pancreatic islet-like cell clusters in agarose containing maltose-carrying polystyrene (HEVM) and nicotinamide

A method for embedded-culture of islet-like cell clusters (ICCs) from neonatal pig pancreas is described. The procedure is based on a sequential treatment of the pancreas with a proteolytic enzyme and ethylenediaminetetraacetate (EDTA). During the exposure to EDTA-Dispase, small pieces of pancreas were gradually digested, with gentle stirring. Under- and over-digested pancreatic cell clusters were separated from the pancreatic fragments by filtration, and formed whole islet-like cell clusters in RPMI 1640 containing 11.0 mM D-glucose and 10% fetal bovine serum (FBS). The ICCs were embedded in agarose with or without a gel containing a random copolymer hydroxethylmethacrylate-vinylbenzyl maltonamide (HEVM) of hydroxethylmethacrylate-(HEMA)-vinylbenzyl maltonamide (VMA) and nicotinamide. They remained morphologically intact and a physiological response to acute stimulation with glucose was obtained when they were embedded in the agarose containing HEVM and nicotinamide. These findings suggest that ICCs in agarose containing HEVM and nicotinamide could be a useful tool for morphological, biochemical and molecular biological studies, and also as a potential source of material for transplantation.

In vitro screening of putative compounds inducing fetal porcine pancreatic beta-cell differentiation: implications for cell transplantation in insulin-dependent diabetes mellitus

Successful transplantation of fetal pancreatic beta-cells to diabetic recipients requires that differentiation of the immature beta-cells is achieved. Animal experiments have shown that this can occur in vivo, but it would be desirable to induce beta-cell maturation in vitro prior to transplantation. For that purpose the effect of several putative inducers of beta-cell differentiation and/or replication in explant cultures of fetal porcine pancreatic islet-like cell clusters (ICC) were investigated. Initial screening experiments indicated that dexamethasone (DEX; 200 ng/ml) and sodium butyrate (BUT; 2 mM) might promote beta-cell differentiation as evidenced by increased insulin/DNA contents in the ICC. In subsequent experiments these two substances, and also nicotinamide (NIC; 10 mM) which previously has been found to promote fetal beta-cell differentiation, were added alone or in combinations to the basal control medium consisting of RPMI 1640 + 1% human serum. All three test agents alone or in combinations increased the insulin content/DNA of the ICC compared with that of the control group. The combination of NIC+DEX increased the insulin mRNA levels of the ICC. No significant stimulation of insulin release was observed in any test group after short-term incubation with high glucose alone. Addition of 5 mM theophylline to high glucose stimulation, however, increased the insulin secretion in most groups of ICC. Finally, ICC in groups of about 600, which had developed in the presence of NIC or NIC+DEX, were transplanted under the kidney capsule of alloxan-diabetic nude mice. However, neither the time for reversal of diabetes (4 weeks) nor the amount of insulin secretion during perfusion from the grafted ICC were further affected by adding DEX to the NIC supplemented medium. The marked increase of the insulin content of the ICC cultured with DEX supplementation, appeared transient and was not manifested after transplantation. In conclusion, the present study demonstrated that some compounds can stimulate porcine fetal beta-cells in an in vitro system, but in order to attain terminal differentiation of the beta-cells including glucose-sensitive insulin secretion, longer observation periods might be required than used herein. Alternatively, an in vivo environment like that after transplantation is mandatory for this process.

Regulation of major histocompatibility complex (MHC) products in fresh and cultured human fetal pancreata aged 9-16 gestational weeks by gamma-interferon

Immunological data on the human fetal pancreas (HFP) are mainly confined to its constitutive expression of the MHC antigens. However, cytokines, such as gamma-interferon (g-IFN), released by lymphocytes during immune reactions, can induce or upregulate the expression of MHC products in allografts and alter their immunological behaviour. We investigated the effects of g-IFN on fresh and cultured HFPs aged 9-16 gestational weeks (gw). Following g-IFN stimulation of fresh HFPs, there was class I hyperexpression by the ductal cells, and some of the ductal, endothelial and islet cells also became class II+. Conventional tissue culture (5% CO2 in air at 37 degrees C) reduced the number of interstitial class II+ cells within the HFP after 1 week but was associated with de novo class I expression by some of the ductal cells. Remarkably, the changes in major histocompatibility complex (MHC) antigen expression by the ductal cells occurred earlier and were markedly enhanced when the HFPs were cultured beforehand. The number of interstitial class II+ cells in fresh and cultured HFPs was not influenced by g-IFN. The significance of these observations with regard to clinical HFP transplantation is discussed.

Cryopreservation of hamster pancreatic islets using a rapid cooling rate

To clarify the possibility of developing a rapid cooling rate for islet cryopreservation, we used a cooling rate of 25 degrees C/min for hamster pancreatic islet cryopreservation using 15 per cent dimethylsulfoxide as a cryoprotectant. After preservation, these islets were examined for their morphology and function by assaying the insulin release after glucose stimulation and the contents of the insulin and DNA in 10 islets. In addition, islet cell replicatory activity was investigated by an autoradiographic technique. The effects of transplantation of the islets upon isogeneic and xenogeneic transplantation were also examined. Freezing using a rapid cooling rate of 25 degrees C/min was found to be as effective as a slow cooling rate of 1 degree C/min for hamster islet cryopreservation. Morphologically, the cryopreserved islets appeared to be similar to the non-frozen cultured islets. The glucose-stimulated insulin release and cell replicatory activities in vitro also remained unchanged, whereas the number of cells per islet decreased slightly after cryopreservation. The grafting of cryopreserved islets normalized streptozotocin induced hyperglycemia following isogeneic transplantation. On the other hand, no prolongation of graft survivals in the case of the xenogeneic transplantation of hamster islets to rats was observed. The isogeneically transplanted islets exhibited the same cell replicatory activities in vivo, which was even higher compared that of normal hamster pancreatic islets in situ. In conclusion, the present findings indicate that hamster pancreatic islets can be successfully cryopreserved using a rapid cooling rate, however, it does not appear that this treatment reduces islet vulnerability to xenogeneic graft rejection.

Functional and morphological differentiation of fetal porcine islet-like cell clusters after transplantation into nude mice

By using a previously described culture technique for the midgestational fetal porcine pancreas, islet-like cell clusters with a Beta-cell frequency of approximately 5% have been produced in large numbers. These islet-like cell clusters were transplanted beneath the kidney capsule to either normoglycaemic or alloxan-treated nude mice. The grafts consistently failed to cure the alloxan-treated mice immediately after implantation, however, normoglycaemia was restored in a majority of the mice within 2 months after transplantation and in all animals after 4 and 6 months. Indeed, the insulin released from the transplanted fetal Beta cells was able to normalize the serum glucose concentration at porcine levels (4-5 mmol/l) rather than at the level maintained in mice (8-10 mmol/l). In the cured mice there was a normal secretory response to glucose in the grafts as evidenced by normal glucose profiles during intravenous glucose tolerance test and a biphasic insulin response to high glucose when perfusing the graft bearing kidney. On the other hand, in the normoglycaemic animals the second phase faded before the glucose stimulus had been withdrawn. Two months after transplantation the endocrine cells were arranged so that the endocrine non-Beta cells were randomly scattered among a majority of Beta cells. The cell replication of the Beta cells, measured by 3H-thymidine incorporation, was within the lower range of that seen in the native islets of adult mice. No major differences between the controls and the alloxan-treated animals were observed in this respect. Cultured islet-like cell clusters had high rates of glucose utilization, paralleled by low rates of glucose oxidation, compared with adult mouse islets.(ABSTRACT TRUNCATED AT 250 WORDS)

Cryopreservation of mouse pancreatic islets: effects of human serum on islet survival

The aim of this study was to compare the survival of cryopreserved mouse pancreatic islets frozen in the presence of either a simple salt solution (Hanks' balanced salt solution) or a complete tissue culture medium (RPMI 1640). Moreover, the addition of 10% human serum to the freezing solutions was evaluated. Collagenase isolated islets were kept in culture for three days, before being cooled at a rate of 5 degrees C/min or 25 degrees C/min to -70 degrees C, at which temperature the islets were transferred to liquid nitrogen. All freezing media were supplemented with 2 M dimethylsulphoxide as cryoprotectant. The islets were rapidly thawed at 37 degrees C and subsequently cultured for another three days. The recovery of islets was higher when the more rapid cooling rate was used and the addition of serum further improved the recovery. Compared to non-frozen cultured islets there was a loss of cells in all groups of cryopreserved islets, as measured by their DNA content, and this was accompanied by a lowered insulin content. All groups of frozen-thawed islets responded to a high glucose stimulus in vitro with a 5-9 fold increase in insulin secretion. There was no obvious advantage of using a complete tissue culture medium for islet cryopreservation, but the addition of serum had some beneficial effects. Data obtained from non-frozen control islets suggest that human serum slightly impairs the function of mouse pancreatic B-cells.

The renal subcapsular site offers better growth conditions for transplanted mouse pancreatic islet cells than the liver or spleen

In order to investigate the importance of the transplantation site for the replication of grafted islet cells, we implanted syngeneic mouse pancreatic islets intrasplenically, intraportally and subcapsularly in the kidney. Fourteen days later the alloxan-diabetic mice were killed after an injection of tritiated thymidine, and the graft-bearing organs fixed and processed for autoradiography. The highest labelling indices were recorded for subcapsularly grafted islets, followed by intraportal and intrasplenic islets in that order. In separate experiments some islet-containing kidney sections were immune stained for insulin before the autoradiographic process. The labelling index of the insulin-positive cells was as high as in the entire islet cell population of the sections from the same mice stained with haematoxylin only. This indicates that the B cells of the islets replicate as often as the other islet cell types. The present data also suggest that the renal subcapsular space offers better growth conditions for transplanted islet cells than the liver or spleen.