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K Tatarkiewicz

Publications and source records attributed to K Tatarkiewicz.

At least 19 recordsLinked to original sources
PubMed2002

Considerations for successful transplantation of encapsulated pancreatic islets.

Encapsulation of pancreatic islets allows for transplantion in the absence of immunosuppression. The technology is based on the principle that transplanted tissue is protected for the host immune system by an artificial membrane. Encapsulation offers a solution to the shortage of donors in clinical islet transplantation because it allows animal islets or insulin-producing cells engineered from stem cells to be used. During the past two decades three major approaches to encapsulation have been studied. These include intravascular macrocapsules, which are anastomosed to the vascular system as AV shunt; extravascular macrocapsules, which are mostly diffusion chambers transplanted at different sites; and extravascular microcapsules transplanted in the peritoneal cavity. The advantages and pitfalls of these three approaches are discussed and compared in the light of their applicability to clinical islet transplantation. All systems have been shown to be successful in preclinical studies but not all approaches meet the technical or physiological requirements for application in human beings. The extravascular approach has advantages over the intravascular because since it is associated with less complications such as thrombosis and infection. Microcapsules, due to their spatial characteristics, have a better diffusion capacity than macrocapsules. Recent progress in biocompatibility of microcapsules has brought this technology close to clinical application. Critical issues such as limitations in the functional performance and survival are being discussed. The latest results show that both issues can be solved by the transplantation of microencapsulated islets close to blood vessels in prevascularized solid supports.

Animals↗
PubMed2001

Porcine neonatal pancreatic cell clusters in tissue culture: benefits of serum and immobilization in alginate hydrogel.

Porcine neonatal pancreatic cell clusters (NPCCs) may be a suitable source of insulin producing tissue for transplantation in diabetic patients. The possible beneficial effect of serum on maturation of NPCCs in vitro is difficult to achieve because of cell clumping, which can be avoided by immobilization in alginate hydrogel matrix. Collagenase treated pancreata, cultured for 4 days, formed NPCCs that were embedded in alginate cross-linked with CaCl2 and cultured in modified Ham's F10 medium with 10% fetal calf serum (FCS) for 10 days. NPCCs cultured as suspension in F10+ with 0.5% bovine serum albumin or with 10% FCS were used as control. To prevent the aggregation when cultured with serum, NPCCs were kept as a very diluted suspension. At the beginning and end of the culture, samples were taken for insulin and DNA content and immunostained for beta and non-beta cells. The culture of NPCCs immobilized in alginate resulted with 3-fold increase in insulin content and 9-fold increase in insulin/DNA ratio. Histology revealed evident increase of number of insulin- and other hormone-positive cells compared with the control. Even though 2 weeks in culture resulted in impaired glucose-induced insulin release, the amount of insulin secreted by clusters cultured in the presence of serum was 4-fold higher than in serum-free conditions. After transplantation, NPCCs retrieved from alginate reversed hyperglycemia similarly to NPCCs cultured in standard conditions. In conclusion, this study shows the feasibility of in vitro immobilization of NPCCs in alginate three-dimensional matrix, allowing cell clusters to be cultured at least two times higher density compared with culture in suspension.

Alginates↗
PubMed2001

Enhanced maturation of porcine neonatal pancreatic cell clusters with growth factors fails to improve transplantation outcome.

BACKGROUND: Porcine neonatal pancreatic cell clusters (NPCC) are a potential source of islet tissue for clinical transplantation. They can normalize glycemia after transplantation, although after a relatively long (several weeks) period of time, possibly due to the immaturity of the tissue. METHODS: One week after isolation NPCCs were immobilized in alginate hydrogel to be cultured for 2 more weeks in the presence of different growth factors, which were applied individually or in various combinations. Their effect was assessed by measuring DNA and insulin content, and expression of islet genes by reverse transcriptase-polymerase chain reaction. Enhanced maturation of NPCCs was also evaluated after transplantation in streptozotocin-diabetic mice. RESULTS: A combination of fetal calf serum, insulin-like growth factor-I, nicotinamide and sodium butyrate in NPCCs media from day 7 to day 21 resulted in increased insulin/DNA content and higher expression of insulin, somatostatin, GLUT2 and Nkx6.1 genes. NPCCs cultured under the same conditions from day 3 to day 12 were transplanted into diabetic mice. Control mice were transplanted with NPCCs cultured in parallel in the presence of nicotinamide, but with no serum, insulin-like growth factor-I or butyrate. Normoglycemia was achieved at the same rate in both groups. Plasma porcine C-peptide (week 6) and graft insulin content (week 20) were also similar in both groups. CONCLUSIONS: Increased insulin content of NPCCs was achieved in vitro by addition of fetal calf serum, insulin-like growth factor-I, nicotinamide, and sodium butyrate, but this increase did not translate into a faster achievement of normoglycemia after transplantation, which suggests that there is a time frame required for complete maturation that is difficult to alter.

Animals↗
PubMed2001

C-peptide responses after meal challenge in mice transplanted with microencapsulated rat islets.

AIMS/HYPOTHESIS: This study aimed to assess a response of microencapsulated rat islets to a meal challenge after being transplanted intraperitoneally into diabetic mice. METHODS: Microencapsulated rat islets or control naked syngeneic mouse islets were transplanted intraperitoneally into mice with streptozotocin-induced diabetes. Meal challenges were done 3, 6 and 9 weeks after transplantation. Glucose-induced insulin secretion from microencapsulated islets before and after transplantation was assessed in vitro. RESULTS: Within the first week, all animals transplanted with either microencapsulated rat islets or with syngeneic murine islets became normoglycaemic (< 11 mmol/l). At 4 and 6 weeks, body weight was less than normal in the non-diabetic control mice. Mice with the encapsulated rat islets had lower fasting glucose concentrations and more rapid glucose clearance after a meal challenge than the control mice. The group of mice with transplanted syngeneic islets had similar glucose profiles to control mice, except for slightly accelerated glucose clearance. The C peptide responses of mice with either microencapsulated or naked islets were clearly lower than the controls. An increase of C peptide appeared as early as 20 min in the plasma of the group with encapsulated islets, but this was considerably slower than in the other two groups. Microencapsulated rat islets retrieved 9 weeks after transplantation did not lose their ability to respond to glucose, but their output was less than half of the pretransplant control islets. CONCLUSION/INTERPRETATION: The delivery of C peptide and presumably the accompanying insulin are delayed by restrictions of the capsules and the peritoneal location. However, this delay in reaching peripheral target organs does not prevent microencapsulated grafts from efficiently clearing glucose after a meal.

Alginates↗
PubMed2000

In vitro cultivation of human islets from expanded ductal tissue.

A major obstacle to successful islet transplantation for both type 1 and 2 diabetes is an inadequate supply of insulin-producing tissue. This need for transplantable human islets has stimulated efforts to expand existing pancreatic islets and/or grow new ones. To test the hypothesis that human adult duct tissue could be expanded and differentiated in vitro to form islet cells, digested pancreatic tissue that is normally discarded from eight human islet isolations was cultured under conditions that allowed expansion of the ductal cells as a monolayer whereupon the cells were overlaid with a thin layer of Matrigel. With this manipulation, the monolayer of epithelial cells formed three-dimensional structures of ductal cysts from which 50-to 150- micrometer diameter islet-like clusters of pancreatic endocrine cells budded. Over 3-4 weeks culture the insulin content per flask increased 10- to 15-fold as the DNA content increased up to 7-fold. The cultivated human islet buds were shown by immunofluorescence to consist of cytokeratin 19-positive duct cells and hormone-positive islet cells. Double staining of insulin and non-beta cell hormones in occasional cells indicated immature cells still in the process of differentiation. Insulin secretion studies were done over 24 h in culture. Compared with their basal secretion at 5 mM glucose, cysts/cultivated human islet buds exposed to stimulatory 20 mM glucose had a 2.3-fold increase in secreted insulin. Thus, duct tissue from human pancreas can be expanded in culture and then be directed to differentiate into glucose responsive islet tissue in vitro. This approach may provide a potential new source of pancreatic islet cells for transplantation.

Adult↗
PubMed1999

Reversal of hyperglycemia in mice after subcutaneous transplantation of macroencapsulated islets.

BACKGROUND: Macroencapsulated islets can reverse hyperglycemia in diabetic animals when transplanted i.p. or into the fat pad. The s.c. space is an attractive site for such transplantation because macrocapsules can be implanted with local anesthesia and be easily removed or reloaded with fresh islets. METHODS: Immunoprotective 20 microl ported devices were transplanted under the skin of Streptozocin-diabetic nude mice. Devices were loaded with 1200 rat islets in culture medium or in alginate. Empty devices were implanted for 2 weeks and then loaded with islets. Normal mice and mice with islets transplanted under the renal capsule or under the skin were used as controls. Seven weeks after transplantation, an intraperitoneal glucose tolerance test (IPGTT) was performed, followed by implant removal. RESULTS: Three weeks after transplantation, normal blood glucose levels were observed in all animals. Compared with those of normal controls, IPGTTs showed accelerated blood glucose clearance in mice transplanted with islets either within devices or beneath the kidney capsule. Fasted transplanted mice were hypoglycemic before glucose injection and 2 hr later. After removal of the implants, all recipient mice returned to hyperglycemia. Histological evaluation revealed viable islet cells and a network of close vascular structures outside the devices. CONCLUSIONS: Macroencapsulated islets transplanted into the s.c. space were able to survive and regulate blood glucose levels in mice. The observed differences in glucose metabolism between normal and transplanted mice may be attributed to the site of transplantation and to the use of rat islets, which have a different set point for glucose induced insulin release.

Animals↗
PubMed1997

Comparison of two methods of pancreas islets immunoisolation.

The efficacy of two methods of Langerhans islets immunoisolation was compared. For this purpose the function of islets encapsulated with alginate/polyethylenimine/protamine/heparin (APPH) or with alginate/poly-L-lisine/alginate (APA) membranes was assessed: in vitro according to their survival and response to glucose challenges, and in vivo according to their capability to provide sufficient insulin delivery to maintain normal fasting blood glucose following xenotransplantation to streptozotocin diabetic mice. In vitro insulin secretion and the response to glucose challenge of APPH and APA encapsulated islets were comparable to free islets. In vivo intraperitoneal concordant xenotransplantation of APA encapsulated rat islets reversed the diabetic state of streptozotocin diabetic mice for a longer period, than APPH islet grafts. This study clearly demonstrated the inadequacy of in vitro methods in the prediction of in vivo results of islets transplantation.

Alginates↗
PubMed1997

[Experiments with pancreas islet xenotransplantation].

Different methods of human, porcine and rat pancreata digestion Langerhans islets purification, immuno-isolation and cryopreservation were compared. The results obtained were assessed in vitro and in vivo. The longest concordial xenograft survival was observed after transplantation of rats islets immunoisolated by Sun's method to streptozotocin diabetic mice. Due to its simplicity and lesser time consumption using Kriomedpol machine was recommended.

Adult↗
PubMed1997

Reversal of hyperglycemia in streptozotocin diabetic mice by xenotransplantation of microencapsulated rat islets.

Rat pancreatic islets were immunoisolated within alginate capsules with additional polyethyleneimine-protamine-heparin highly biocompatible membrane. Perifusion study in vitro demonstrated satisfactory similarities between the insulin release profiles of encapsulated and free islets. Concordant xenotransplantation of microencapsulated rat islets significantly prolonged mean time of restored normoglycemia (46 +/- 15 days) in streptozotocin-diabetic BALB/c mice recipients comparing to uncoated grafts (7 +/- 2 days).

Alginates↗
PubMed1997

Porcine neonatal pancreatic cell clusters (NPCCs): a potential source of tissue for islet transplantation.

This is a short review of porcine neonatal pancreatic cell clusters (NPCCs) which might eventually be useful for beta cell replacement therapy in people with diabetes. The current success with islet allograft transplantation is reviewed and is problematic because only partial success has been obtained and the shortage of human islet tissue means that only a small fraction of people with diabetes would be able to benefit. For these reasons there is considerable interest in xenotransplantation, with pigs being a particularly attractive source. The relative merits of early fetal, late fetal, neonatal and adult porcine tissue are discussed. Neonatal tissue has several attractive features, with their hardiness and potential for growth being especially noteworthy. NPCCs are harvested after digested and dispersed clumps of cells are kept in culture for 7 days. The NPCCs consist mainly of duct cells, protodifferentiated cells and mature endocrine cells. The protodifferentiated cells are either double or triple stained for insulin, cytokeratin 7, glucagon, pancreatic polypeptide, or somatostatin. When transplanted into diabetic nude mice it usually takes weeks before glucose levels are normalized, and during that time differentiation and growth of the graft can be observed. Potential strategies for controlling xenograft rejection are mentioned, with these being immunosuppression, induction of tolerance, immunobarrier devices, and gene transfer approaches.

Animals↗
PubMed1996

Experience with pancreas islets separation, immunoisolation and cryopreservation.

Experience of Warsaw Pancreas Laboratory is presented. Some improvement in the methods of rat, human and pig pancreases digestion, and in identification of Langerhans islets by means of intravenous injection of I-DTZ was achieved. For immunoisolation of islets, 2 methods were elaborated: capsules containing alginate/polyethyleneimine/protamine/heparin membrane prepared by modified Sun method, and microcapsules based on Zekorn method. Biocompability of hollow fibers, prepared with polypropylene (PP), surface modified PP (PPS) and polysulphone (PS) was assessed in vitro. Only PS fibers were fully compatible. It was shown, that the mixture of exocrine tissue did not influence in vitro insulin secretion, providing that alginate in which islets are embedded remain gelled. The efficacy of 3 methods of islets cryopreservation was compared: freezing in "semicontrolable" conditions, in programmable Kriomedpol machine, and vitrification. The highest percentage of frozen/thawed living cells, and the most reliable results were obtained with Kriomedpol method.

Alginates↗
PubMed1994

In vitro and in vivo evaluation of protamine-heparin membrane for microencapsulation of rat Langerhans islets.

Rat pancreatic islets were microencapsulated with multilayer protamine-heparin (PH) membrane. Basal and stimulatory insulin secretion of microencapsulated islets was similar to the controlled free islets in vitro. During the long-term culture (up to 2 weeks) mean insulin release of encapsulated islets did not significantly differ from the mean of free ones (the ratio of mentioned means was 54-167%). Empty PH microcapsules transplanted into Wistar rats intraperitoneally and under the kidney capsule were generally harmless up to 4 months. In only a few cases traces of fibrotic tissue around capsules entrapped in the omentum were found. No damage of microcapsules structure was observed. The worst results were obtained in the instance of retroperitoneal transplantation. We conclude, therefore, that PH membrane was proved to be highly biocompatible, nontoxic for islets, and did not impair viability and glucose-dependent insulin secretion of Langerhans islets in in vitro culture.

Animals↗