A simple high efficiency intra-islet transduction protocol using lentiviral vectors

Successful normalization of blood glucose in patients transplanted with pancreatic islets isolated from cadaveric donors established the proof-of-concept that Type 1 Diabetes Mellitus is a curable disease. Nonetheless, major caveats to the widespread use of this cell therapy approach have been the shortage of islets combined with the low viability and functional rates subsequent to transplantation. Gene therapy targeted to enhance survival and performance prior to transplantation could offer a feasible approach to circumvent these issues and sustain a durable functional β-cell mass in vivo. However, efficient and safe delivery of nucleic acids to intact islet remains a challenging task. Here we describe a simple and easy-to-use lentiviral transduction protocol that allows the transduction of approximately 80 % of mouse and human islet cells while preserving islet architecture, metabolic function and glucose-dependent stimulation of insulin secretion. Our protocol will facilitate to fully determine the potential of gene expression modulation of therapeutically promising targets in entire pancreatic islets for xenotransplantation purposes

Multicenter Assessment of Animal-free Collagenase AF-1 for Human Islet Isolation

Animal-free (AF) SERVA Collagenase AF-1 and Neutral Protease (NP) AF GMP Grade have recently become available for human islet isolation. This report describes the initial experiences of 3 different islet transplant centers. Thirty-four human pancreases were digested using 1 vial of the 6 different lots of Collagenase AF-1 (2,000-2,583 PZ-U/vial) supplemented with 4 different lots of NP AF in a range of 50 to 160 DMC-U per pancreas. Isolation, culture, and quality assessment were performed using standard techniques as previously described. All data are presented as mean +/- standard error of the mean (SEM). Variability of pancreas weight was associated with a wide range of collagenase and NP activities, ranging from 12.7 to 46.6 PZ-U/g (26.0 +/- 1.5 PZ-U/g) and 0.4 to 3.0 DMC-U/g (1.5 +/- 0.1 DMC-U/g), respectively. Postpurification islet yield was 296,494 +/- 33,620 islet equivalents (IEQ) equivalent to 3,274 +/- 450 IEQ/g with a purity of 55.9% +/- 3.2%. Quality assessment performed after 2 to 4 d of culture demonstrated a viability of 88.1% +/- 1.5% and a stimulation index of 3.7 +/- 0.7. Eighteen of the 34 preparations were transplanted into type 1 diabetic patients equivalent to a transplantation rate of 52.9%. Six preparations, which were infused into patients as first transplant, could be analyzed and increased the fasting C-peptide level from 0.11 +/- 0.08 pretransplant to 1.23 +/- 0.24 and 2.27 +/- 0.31 ng/mL 3 and 6 mo posttransplant (P < 0.05), respectively. Insulin requirements were simultaneously reduced at the same time from 39.2 +/- 3.8 IU/d before transplantation to 10.8 +/- 4.1 and 4.0 +/- 2.3 IU/d, after 3 and 6 mo posttransplant (P < 0.05), respectively. This study demonstrates the efficiency of AF SERVA Collagenase AF-1 and NP AF for clinical islet isolation and transplantation. The new plant-based production process makes these products a safe new option for the islet field

Survival and function of encapsulated rat islets <i>in vitro</i>.

<p>Viability was assessed over 30 days in(green) and propidium iodide (red). Encapsulated islets remained viable over 30 days of culture. Scale bar 200 µm (A). The function of the encapsulated islets was tested in vitro 30 days post encapsulation by glucose stimulated insulin secretion test. Islets were incubated in medium with 2.8 mM glucose, 16.8 mM glucose and 16.8 mM glucose supplemented with theophylline. The stimulation index was respectively 2 (glucose-stimulated) and 5 (theophylline-stimulated). The mean and SEM are shown of one representative experiment out of three (B).</p

Characterization of the rejection in the bone marrow after rat islets transplantation.

<p>(A–C) Seven days post-transplantation, animals were sacrificed for the characterization of rejection. The graft-bearing femur (n = 5), the opposite control femur (n = 4) and the femur of non-transplanted animals (n = 4) were harvested, flushed and the cells analyzed by flow cytometry. The percentage of CD8⁺ (A) cells in transplanted femurs was significantly increased whereas percentages of CD4⁺ (B) and F4/80⁺ (C) cells remained unchanged compared to the non-transplanted contralateral control femurs. Box-and-whisker diagram are shown. (D–F) Alternatively, the femurs of graft bearing-femurs (D–F) and the contralateral femurs (G–I) were frozen in liquid nitrogen and double stained for insulin (green) and CD8 (D/G), CD4 (E/H) or F4/80 (F/I) (red) three days post transplantation. Scale bar 50 µm. (J) CD4⁺, CD8⁺ and F4/80⁺ cells were quantified using the MetaMorph software. The levels of CD4⁺ and F4/80⁺ cells were similar between both groups; CD8⁺ cells were significantly more abundant in femurs containing the islet graft. Abbreviation. Tx Cont: contralateral femur. TX D7: graft bearing femur.</p

Characterization of the splenocytes after rat islet transplantation into the bone marrow.

<p>The splenocytes of transplanted and naive animals were harvested seven days after transplantation. The absolute number of splenocytes was not significantly different compared to naive mice; data are shown for individual animals with the horizontal line representing the mean value (A). The percentages of CD4⁺, CD8⁺ and F4/80⁺ cells were not significantly different either. Box-and-whisker diagram are shown (B). However, splenocytes of transplanted mice showed a significantly increased level of proliferation compared to naive mice when stimulated by donor (T cell-depleted) rat irradiated splenocytes. Results are expressed in counts per minute and show the mean value of 4 naive and 6 transplanted animals (C). Abbreviation. Tx: transplanted. CPM: Count per minutes.</p

Transplantation of syngeneic islets into the bone marrow.

<p>A 22-gauge needle was used for injection of the syngeneic islets into the bone marrow of C57BL/6 through the distal part of the femur (A). Transplanted mice remained normoglycemic over 30 days (B). Intraperitoneal glucose tolerance test was performed after 30 days in transplanted and naïve mice. Error bars represent the standard deviation. (C). Bones were harvested after 30 days and stained for haematoxylin and eosin (D), insulin (E) and glucagon/insulin (F). Glucagon positive cells appear in red whereas insulin positive cells appear in green. Scale bar 500 µm (D,E), 100 µm (F).</p