Proliferative and Cytokine Responses in CTLA4-Ig-Treated Diabetic NOD Mice Transplanted with Microencapsulated Neonatal Porcine ICCs

Abstract

Our goal is to develop effective islet xenografts for treating human diabetes. We have studied microencapsulated neonatal porcine islet cell clusters (ICCs) transplanted intraperitoneally in spontaneously diabetic NOD mice, where they function to maintain normoglycemia in the autoimmune host. Nonencapsulated neonatal porcine ICCs functioned for 4.5 ± 0.5 days before being rejected; encapsulation prolonged graft function to 17 ± 2 days. CTLA4-Ig treatment did not enhance the survival of nonencapsulated ICCs. However, CTLA4-Ig treatment significantly extended the function of encapsulated ICCs to 73 ± 5 days. Histological analyses demonstrated a profuse pericapsular cellular reaction associated with rejection of encapsulated islet xenografts in untreated mice, while this reaction was significantly reduced in CTLA4-Ig-treated mice. To study mechanisms of xenograft rejection in this model, we analyzed proliferative responses to neonatal porcine ICCs and cytokines present in the peritoneal cavities of transplanted mice. Spleen cells from both CTLA4-Igtreated and untreated rejecting NODs exhibited vigorous proliferation in the absence of antigenic stimulation, suggesting prior activation in vivo, while splenocytes from CTLA4-Ig-treated NODs with functioning grafts had low proliferative levels, equal to controls. Islet-specific proliferation was not detected in islet-rejecting mice, perhaps due to their high background levels. With the exception of elevated IL-6 levels, empty capsules did not provoke a significant peritoneal cytokine response compared with sham surgery or untransplanted control mice. However, IL-5, IL-12, TGF-β, and IL-1β were significantly elevated in NODs receiving encapsulated neonatal porcine ICCs compared with untransplanted controls. There were no significant differences between peritoneal cytokine concentrations in CTLA4-Ig-treated mice with long-term functioning grafts compared to mice that rejected grafts at earlier time points. We conclude that the combination of donor islet microencapsulation and brief treatment of the recipient with co-stimulatory blockade delays sensitization of the host, possibly by altering mechanism(s) for recruitment and/or activation of host effector cells.

The Use of Biomaterials in Islet Transplantation

“…Similar results were also seen elsewhere [96]. Safley et al [94, 95] showed that empty microcapsules did not elicit an immune response and it was the presence of the xenogenic islets that attracted large numbers of leukocytes to the transplantation site. Others showed that the composition of the microcapsules also affects the biocompatibility of the microcapsule [93].…”

“…Recent reports are now attempting to combine microcapsule optimization with immunosuppression to determine whether graft function can be extended. For example, Safley et al [94, 95] observed that inhibition of T-cell costimulatory molecules CD28/B7 by CTLA-Ig in NOD mice transplanted with microencapsulated porcine islets extended graft function compared with no treatment. Similar results were also seen elsewhere [96].…”

Accelerated Functional Maturation of Isolated Neonatal Porcine Cell Clusters: In Vitro and In Vivo Results in NOD Mice

“…Moreover, either free or microencapsulated NPCCs (12,000/ grafted into diabetic NOD mice, resulting in full reversal of hyperglycemia throughout 7 weeks post-TX. To our mouse) were grafted into four groups of diabetic NOD mice (29). Free islets were implanted intrasplenically in knowledge, this is the first observation on the capability of microencapsulated low-mass NPCCs to reverse hyanimals that received or not peritoneal daily injections of cytotoxic T-lymphocyte antigen 4 immunoglobulin perglycemia in NOD mice.…”

“…Nevertheless, it should be underlined that, up to Briefly, each testicle pair, upon removal under sterile now, there is no evidence of hyperglycemia correction conditions, was placed in Eurocollins (SALF), finely in stringent animal models of T1DM such as spontaneminced, and immediately incubated with a solution conously diabetic NOD mice, except for the article pubtaining collagenase, trypsin, and DNAase. At the end of lished by Weber and coworkers (29) demonstrating that digestion, the tissue was resuspended in HBSS, filtered NPCCs transplanted intraperitoneally in spontaneousthrough a 500-µm stainless steel mesh, plated in 100 × ly diabetic NOD mice can maintain normoglycemia 20-mm petri dishes, and culture maintained in HAMfor 73 ± 5 days (upon daily treatment of mice with F12 (Sigma) supplemented as described above, in 95% CTLA4-Ig).…”

Microencapsulated adult porcine islets transplanted intraperitoneally in streptozotocin‐diabetic non‐human primates

“…Microcapsules were formalin-fixed, embedded in paraffin, sectioned, mounted on glass slides, and stained by hematoxylin-eosin as previously described. 52 Explanted encapsulated islets from representative NHPs transplanted with APIs in either single or double capsules were stained for endogenous markers of hypoxia, including hypoxia-inducible factor 1 (HIF-1α), osteopontin, and glucose transporter-1 (GLUT-1). 53 Briefly, deparaffinized encapsulated islets were stained using an avidin-biotinylated enzyme complex kit human liver (for osteopontin), and renal cell carcinoma lysate (for GLUT-1).…”