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Cell microencapsulation continues to hold significant promise for biotechnology and medicine. The controlled, and continuous, delivery of therapeutic products to the host by immunoisolated cells is a potentially cost-effective method to treat a wide range of diseases. Although there are several issues that need to be addressed, including capsule manufacture, properties and performance, in the past few years, a stepwise analysis on the essential obstacles and limitations has brought the whole technology closer to a realistic proposal for clinical application. This paper summarizes the current situation in the cell encapsulation field and discusses the main events that have occurred along the way.

OBJECTIVETo assess long-term metabolic and immunological follow-up of microencapsulated human islet allografts in nonimmunosuppressed patients with type 1 diabetes (T1DM).RESEARCH DESIGN AND METHODSFour nonimmunosuppressed patients, with long-standing T1DM, received intraperitoneal transplant (TX) of microencapsulated human islets. Anti-major histocompatibility complex (MHC) class I–II, GAD65, and islet cell antibodies were measured before and long term after TX.RESULTSAll patients turned positive for serum C-peptide response, both in basal and after stimulation, throughout 3 years of posttransplant follow-up. Daily mean blood glucose, as well as HbA1c levels, significantly improved after TX, with daily exogenous insulin consumption declining in all cases and being discontinued, just transiently, only in patient 4. Anti-MHC class I–II and GAD65 antibodies all tested negative at 3 years after TX.CONCLUSIONSThe grafts did not elicit any immune response, even in the cases where more than one preparation was transplanted, as a unique finding, compatible with encapsulation-driven “bioinvisibility” of the grafted islets. This result had never been achieved with the recipient’s general immunosuppression.

T ime-related decline of human islet allograft (TX) function in generally immunosuppressed type 1 diabetic patients (1-5) has led us, after years of preclinical study (6), to initiate a phase 1 pilot clinical trial of microencapsulated TX into 10 nonimmunosuppressed patients with type 1 diabetes, under permission and surveillance by the Italian Ministry of Health (file no. 19382, PRE 805, 5 September 2003). RESEARCH DESIGN AND METHODS Human islet procurementHuman islets were isolated from singledonor pancreases according to the Edmonton protocol (1). Only preparations complying with standard quality control criteria (1) were considered for TX. The islets were cultured for 24 h in HAM F12 (Celbio, Milano, Italy), supplemented with antibiotics and 1.25% human albumin (Kedrion Spa, Milano, Italy) at 37°C in 95% air/CO 2 . MicroencapsulationThe islets were washed and thoroughly mixed with 1.6% endotoxin-and pyrogenfree sodium alginate (Stern Italia, Milan, Italy) that had been highly purified according to U.S. Pharmacopeia. Upon extrusion through a microdroplet generator (droplets generated by combination of air shears and mechanical pressure by a peristaltic pump), microdroplets containing the islets, upon collection in a CaCl 2 bath, turned into gel microbeads. The beads, containing 1-2 islets and measuring an average 500 m in diameter, were sequentially double-coated with 0.12% and 0.06% poly-L-ornithine (Sigma) and finally with 0.04% sodium alginate (Stern) (7). Patient recruitmentTen patients with long-standing type 1 diabetes on intensive insulin therapy regimens (lispro prebreakfast, lunch, and supper and glargine presupper) and undetectable serum C-peptide responses (sCPRs) were tested for complete blood chemistry, parameters of diabetes control (GHb, daily blood glucose profiles, and insulin requirement), anti-GAD 65 antibodies, and islet cell antibodies. Chest Xray and abdominal echography were also performed. Pre-and post-TX patient assessmentThe patients were maintained on euglycemia overnight before TX by supplementing exogenous insulin as required. After TX, the patients were monitored hourly for blood glucose (range: 80 -150 mg/dl) and insulin requirement. sCPR samples, assayed by radioimmunoassay (sCPR sensitivity: 0.06 ng/ml [intra-assay CV 3.7-4.5%, interassay CV 4.4 -5%]) (TechnoGenetics, Milan, Italy) in our laboratory, were drawn twice daily for the first 7 days and weekly thereafter, both in basal and 90 min after meals. A 75-g oral glucose tolerance test (OGTT) was scheduled for patient 1 at 60 days post-TX. At 7 days post-TX, the patients were discharged and instructed to continue blood glucose home selfmonitoring, with adjustments of insulin requirement. At 30 days post-TX, control abdominal echography was scheduled. Encapsulated human islets for TXA total of 400,000 and 600,000 microencapsulated islets (islet equivalents normalized to 150 ) were grafted in patient 1 and patient 2, respectively. The final TX volume included 50 ml of microcapsules diluted in 100 ml of saline. Empty microcaps...