Tissue factor and CCL2/monocyte chemoattractant protein-1 released by human islets affect islet engraftment in type 1 diabetic recipients

Islet survival in the early posttransplantation period is likely to be influenced by inflammatory events in and around islets. Twenty-seven human islet preparations were transplanted by 24 infusions into 14 patients with brittle type 1 diabetes under the Edmonton protocol. Patients were monitored for their coagulation [cross-linked fibrin degradation products (XDPs)] and liver function test [aspartate and alanine aminotransferase (AST and ALT)] as markers of early posttransplant complications, and these were correlated with in vitro islet number, purification, volume, monocyte-chemoattractant protein-1 (CCL2/MCP-1) and tissue factor (TF) islet release. Consistent with activation of coagulation pathways and hepatic damage, serum XDP values increased early after 11 infusions and transaminase after 13 of 24 infusions. TF and CCL2/MCP-1 were detected in supernatants of 21 and 22 islet preparations, respectively. Serum XDP peak values were correlated with TF/equivalent islets (EI) (r(2)=0.26, P = 0.001) and CCL2/MCP-1/EI (r(2) = 0.42; P < 0.001); serum transaminase areas under the curve in the first week posttransplantation were correlated with CCL2/MCP-1/EI (r(2) = 0.55; P < 0.001 for ALT and r(2) = 0.51; P = 0.001 for AST) and TF/EI (r(2) = 0.31; P = 0.002 for ALT, and r(2) = 0.36; P = 0.002 for AST). These data suggest that reducing the islet proinflammatory state may be a means to reduce the early posttransplant complications and perhaps improve islet engraftment.     

Beta cell function during rapamycin monotherapy in long-term type 1 diabetes

Aims/hypothesis  

Type 1 diabetes is considered non-reversible at end-stage disease when there is no measurable insulin production. However, there are indications that insulin-producing beta cells could be present or return if autoimmunity could be controlled. We therefore sought to determine whether immunosuppression therapy can reinstate beta cell function in patients with long-term type 1 diabetes.     

Optimizing dose and administration regimen of a high-relaxivity contrast agent for myocardial MRI late gadolinium enhancement

Objectives

To investigate the time-course of late gadolinium enhancement of infarcted myocardium using gadobenate dimeglumine at different dosages and administration regimens.

Materials and methods

After institutional review board approval and informed consent, we studied 13 patients (aged 63 ± 11 years) with chronic myocardial infarction. They underwent two gadobenate dimeglumine-enhanced MR examinations (interval 24–48 h) using short-axis inversion-recovery gradient-echo sequences, with the following two different protocols, in randomized order: 0.05 mmol/kg and imaging at the 2.5th, 5th, 7.5th and 10th minute plus 0.05 mmol/kg and imaging at the 12.5th, 15th, 17.5th and 20th minute; the same as before but using 0.1 mmol/kg for both contrast injections. Contrast-to-noise ratios (CNRs) between infarcted myocardium, non-infarcted myocardium and left ventricle cavity were calculated for each time-point (2.5-min steps). Friedman ANOVA was used for comparing the CNR time-course; Wilcoxon test for comparing CNR at the 10th and the 20th minute.

Results

The CNR between infarcted and non-infarcted myocardium obtained at the 20th minute with 0.05 plus 0.05 mmol/kg resulted significantly higher than that obtained at the 10th minute with 0.05 mmol/kg (P = 0.033) while not significantly different from that obtained at the 10th (0.1 mm/kg) or at the 20th minute with 0.1 plus 0.1 mmol/kg. The CNR between infarcted myocardium and the left ventricle cavity obtained at the 20th minute with 0.05 plus 0.05 mmol/kg resulted significantly higher than all other measured values (P ≤ 0.017).

Conclusion

Using gadobenate dimeglumine, 0.05 plus 0.05 mmol/kg allows for a higher CNR between infarcted myocardium and the left ventricle cavity allowing for reliable assessment of the sub-endocardial infarctions.     

Monoclonal antibodies as a probe for the unfolding of porcine growth hormone

Monoclonal antibodies (mAbs) were generated against pituitary porcine growth hormone (pGH). Ten mAbs were selected for their specificity and affinity for pGH. These mAbs were of the immunoglobulin G (IgG)(1) kappa subclass, with dissociation constants (K(d)) between 7.42 and 0.26 nM, and recognised seven non-overlapping epitopes. We measured whether the mAbs detected alterations of the pGH three-dimensional structure by comparing the antibody reactivity to native pGH and to pGH experimentally unfolded by heating at 50 degrees C, 75 degrees C and 100 degrees C or by reduction and S-carboxymethylation. The antibody-antigen interactions were studied with two enzyme-linked immunosorbent assays (ELISA), based either on a direct binding or inhibition format. The results show that: 1) one mAb, mAb D12, is a conformation-sensitive antibody that recognises an epitope present only in the native pGH. Because the intact three-dimensional structure is essential for the expression of biological activity, mAb D12 could be used to detect altered pGH molecules in biological samples (blood, pituitary extracts or material produced with recombinant technology), and for the one-step purification of biologically active pGH by immunoaffinity chromatography; 2) one mAb, mAb I4, binds to a linear epitope that is not significantly modified in the denatured hormone. This mAb was able to detect the hormone in assays where protein conformation is usually strongly altered, i.e. immunoblotting and immunohistochemistry; 3) the performances of the other eight mAbs differed significantly in the competitive and non-competitive ELISA.