Xenografts of porcine islets immunoprotected in hollow fibres reduce the incidence of diabetes in non-obese diabetic mice

AN69 Hollow Fiber Membrane will Reduce but Not Abolish the Risk of Transmission of Porcine Endogenous Retroviruses

As the risk of porcine endogenous retrovirus (PERV) infection is a major obstacle to the xenotransplantation of porcine tissue, we investigated whether an AN69 hollow fibre membrane, used for islets of Langerhans transplantation, could prevent the transfer of PERVs and thus reduce the risk of PERV infection. PK15 cells were used as a PERV source. A specific and highly sensitive RCR was used for detection of a PERV provirus DNA (gag region) and a porcine mtDNA. Human U293 cells were incubated in vitro with encapsulated PK15 cells, concentrated encapsulated PK15 supernatant, or concentrated PK15 supernatant as a control. CD1 mice were implanted in vivo with encapsulated PK15 cells or injected with PK15 supernatant. We found no infection in human cells incubated with either encapsulated PK15 supernatant or in 10 out of 11 samples after coincubation with encapsulated PK15 cells. Infection of human cells was, however, detected in 1 out of 11 samples after coincubation with encapsulated PK15 cells. The presence of PERV provirus DNA and porcine mtDNA was detected in all the investigated tissues of the mice injected with PK15 supernatant and in various tissues of the mice implanted with encapsulated PK15 cells. Four weeks after the last injection of PK15 supernatant or a fiber explantation, no mouse showed any presence of PERV provirus DNA or porcine mtDNA. Our results demonstrate that AN69 hollow fiber membrane will reduce but not abolish the risk of PERV infection. Because the real risk of PERV infection still remains unknown, it is necessary to investigate further the real protection that could be provided by hollow fibers to ensure the safety of clinical xenotransplantation.

Cytokine mobilization of bone marrow cells and pancreatic lesion do not improve streptozotocin-induced diabetes in mice by transdifferentiation of bone marrow cells into insulin-producing cells

OBJECTIVE

Transdifferentiation of bone marrow cells (BMC) into insulin-producing cells might provide a new cellular therapy for type I diabetes, but its existence is controversial. Our aim was to determine if those cells could transdifferentiate, even at low frequency, into insulin-producing cells, in testing optimized experimental conditions.

METHODS

We grafted mice with total BMC, genetically labeled either ubiquitarily, or with a marker conditionally expressed under the control of the insulin beta-cell specific promoter. We treated some of the recipients with an agent toxic to beta-cells (streptozotocin) and with cytokines stem cell factor (SCF) and granulocyte-colony stimulating factor (G-CSF).

RESULTS

The contribution of grafted cells could be detected neither for natural turnover (n=6), nor for beta-cell regeneration after pancreatic lesion (n=7), 90 days post-transplantation. Cytokine mobilization of BMC in the blood stream, reported to favor their transdifferentiation into cardiac and neural cells, had never been tested before for beta-cell generation. Here, we showed that injection of SCF and G-CSF did not lead to a detectable level of transdifferentiation (n=7).

CONCLUSIONS

We conclude that BMC cannot spontaneously transdifferentiate into insulin-producing cells in vivo, even after beta-cell lesion and mobilization induced by cytokines. Interestingly, however, treatment by cytokines may have beneficial indirect effects on STZ-induced hyperglycaemia.

Immunocompatibility and biocompatibility of cell delivery systems

Immunoisolation therapy overcomes important disadvantages of implanting free cells. By mechanically blocking immune attacks, synthetic membranes around grafted cells should obviate the need for immunosuppression. The membrane used for encapsulation must be biocompatible and immunocompatible to the recipient and also to the encapsulated graft. The ability of the host to accept the implanted graft depends not only on the material used for encapsulation, but also on the defense reaction of the recipient, which is very individual. Such a reaction usually starts as absorption of cell-adhesive proteins, immunoglobulins, complement components, growth factors and some other proteins on the surface of the device. The absorption of proteins is difficult to avoid, but the amount and specificity of absorbed proteins can be controlled to some extent by selection and modification of the device material. If the adsorption of proteins to the surface of the implanted material is reduced, the overgrowth of the device with fibroblast-like and macrophage-like cells is also reduced. Cell adhesion at the surface of the implanted device is, in addition to the selected polymeric material, greatly influenced by the device content. Xenografts trigger a more vigorous inflammatory reaction than allografts, most probably due to the release of antigenic products from encapsulated deteriorated and dying cells which diffuse through the membrane and activate adhering immune cells. There is an evident effect of autoimmune status on the fate of the encapsulated graft. While encapsulated xenogeneic islets readily reverse streptozotocin-induced diabetes in mice, the same xenografts are short-functioning in NOD autoimmune diabetes-prone mice. Autoantibodies, to which most devices are impermeable, are not involved. Among the cytotoxic factors which are responsible for the limited survival of the encapsulated graft the most important are cytokines and perhaps some other low-molecular-weight factors released by activated macrophages at the surface of the encapsulating membrane.

Oral insulin administration and residual beta-cell function in recent-onset type 1 diabetes: a multicentre randomised controlled trial. Diabète Insuline Orale group

BACKGROUND

Oral administration of autoantigens can slow the progression of beta-cell destruction in non-obese diabetic mice. We investigated whether oral administration of recombinant human insulin could protect residual beta-cell function in recent-onset type 1 diabetes.

METHODS

We enrolled 131 autoantibody-positive diabetic patients aged 7-40 years within 2 weeks of diagnosis (no ketoacidosis at diagnosis, weight loss <10%, polyuria for <6 weeks). They were randomly assigned 2.5 mg or 7.5 mg oral insulin daily or placebo for 1 year, in addition to subcutaneous insulin therapy. Serum C-peptide concentrations were measured in the fasting state and after stimulation, to assess beta-cell function. Autoantibodies to beta-cell antigens were assayed. Analyses were by intention to treat.

FINDINGS

Baseline C-peptide and haemoglobin A1c concentrations were similar in the three groups. During follow-up, there were no differences between the groups assigned 2.5 mg or 7.5 mg oral insulin or placebo in subcutaneous insulin requirements, haemoglobin A1c concentrations, or measurements of fasting (mean at 12 months 0.18 [SD 0.17], 0.17 [0.17], and 0.17 [0.12] nmol/L) or stimulated C-peptide concentrations (glucagon-stimulated 0.39 [0.38], 0.37 [0.39], and 0.33 [0.24] nmol/L; meal-stimulated 0.72 [0.60], 0.49 [0.49], and 0.57 [0.51 nmol/L]. Neither age nor C-peptide concentration at entry influenced treatment effects. No differences were seen in the time-course or titres of antibodies to insulin, glutamic acid decarboxylase, or islet antigen 2.

INTERPRETATION

At the doses used in this trial, oral administration of insulin initiated at clinical onset of type 1 diabetes did not prevent the deterioration of beta-cell function.

The rescue effect of 15-deoxyspergualin on intraperitoneal microencapsulated xenoislets

Because the development of surface neogrowth composed mainly of macrophages and fibroblasts precedes the recurrence of hyperglycemia in treated diabetic animals, the pericapsular macrophages may adversely affect the graft function of i.p. alginate-poly-L-lysine-alginate (A-P-A) microencapsulated islets. In order to clarify the role of pericapsular macrophages on late islet xenograft dysfunction, we investigated whether 15-deoxyspergualin (15-DSG), a macrophage inhibitor, has a rescue effect on the recurrent hyperglycemia in streptozotocin-induced diabetic mice that had been treated with i.p. transplantation of A-P-A microencapsulated rat islets. The mean duration of normoglycemia (whole blood glucose level below 8.3 mmol/l) in streptozotocin-induced diabetic mice treated with implantation of about 2200-2400 of A-P-A microencapsulated rat islets was 75 days. When the blood glucose levels were higher than 11.1 mmol/l for two consecutive determinations, 15-DSG at a dose of 0.625 mg/kg body weight or isotonic sodium chloride solution (control group) was given daily s.c.. The blood glucose levels decreased significantly from 13.9 +/- 0.5 mmol/l to 11.0 +/- 1.3 mmol/l (n = 18, p < 0.05) at the fourth day and to 7.6 +/- 1.0 mmol/l (n = 18) at the 14th day of 15-DSG administration. That was not significantly different from the mean glycemic level during the normoglycemic period (7.6 +/- 1.0 vs. 7.0 +/- 1.7 mmol/l, n = 18, p = NS). Isotonic sodium chloride solution injections did not reduce glycemic levels of mice in the control group. As another control, 10 streptozotocin-induced diabetic mice were given the same daily doses of 15-DSG for 14 days. 15-DSG did not decrease the blood glucose levels of diabetic mice in the control group. We further studied the effect of 15-DSG on the expression of interleukin-1beta (IL-1beta) in peritoneal exudate mononuclear cells (PEMCs) using reverse transcription-polymerase chain reaction. It was found that the mRNA of IL-1beta was undetectable in PEMCs of 15-DSG-treated diabetic mice even after those cells were stimulated by lipopolysaccharides in vitro. Administration of 15-DSG at a daily dose of 0.625 mg/kg body weight from the 22nd to the 28th day after transplantation and 7 consecutive days every 3 weeks thereafter did not prolong graft survival of i.p. microencapsulated rat islets. Our data suggest that 15-DSG has a rescue effect when A-P-A microencapsulated islets have induced cellular overgrowth that threatens the survival of the graft. It is possible that the surface overgrowth composed of macrophages is involved in the pathophysiology of late failure of A-P-A microencapsulated xenogeneic islets.