Beating diabetes: strategies to improve pancreatic islet transplantation

Type 1 diabetes is a chronic disease that is caused by nearly complete destruction of insulin producing beta-cells in the islets of Langerhans, affecting approximately 25 million people worldwide. Prior to the discovery of insulin, diabetes most certainly led to death. To date, patients with type 1 diabetes require daily insulin injections to control their blood glucose levels. Although this therapy is effective, it lacks precise glycemic control which on the long term increases the risk of developing life-threatening diseases such as heart disease, stroke, and kidney failure. Patients with type 1 diabetes who have had a kidney transplant or who suffer from severe hypoglycemia unawareness might benefit from intrahepatic transplantation of donor islets, according to the so-called ‘Edmonton protocol’. This procedure has worldwide been conducted over 750 times. Although the initial results are promising, only 10% of patients remained insulin-independent five years after treatment, which together with a lack of sufficient quantities of donor tissue and the need for lifelong immunosuppressive therapy have hampered its widespread application. This thesis describes several strategies that aim at improving the current pancreatic islet transplantation procedure

Predicting success of vagus nerve stimulation (VNS) from EEG symmetry

Purpose Vagus nerve stimulation (VNS) has shown to be an effective treatment for drug resistant epilepsy, with achieving more than 50% seizure reduction in one third of the treated patients. In order to predict which patients will profit from VNS, we previously found that a low pairwise derived Brain Symmetry Index (pdBSI) could potentially predict good responders to VNS treatment. These findings however have to be validated before they can be generalized. Methods 39 patients (age 18???68 years) with medically intractable epilepsy who were referred for an implanted VNS system were included. Routine EEG registrations, recorded before implantation, were analyzed. Artefact-free epochs with eyes open and eyes closed were quantitatively analyzed. The pdBSI was tested for relation with VNS outcome one year after surgery. Results Twenty-three patients (59%) obtained a reduction in seizure frequency, of whom ten (26%) had a reduction of at least 50% (good responders) and thirteen (33%) a reduction of less than 50% (moderate responders). Sixteen patients without seizure reduction are defined as non-responders. No significant differences were found in the pdBSI of good responders (mean 0.27), moderate responders (mean 0.26) and non-responders (mean 0.25) (p??>??0.05). Besides seizure reduction, many patients (56%) reported additional positive effects of VNS in terms of seizure duration, seizure intensity and/or postictal recovery. Conclusion EEG features that correlate with VNS therapy outcome may enable better patient selection and prevent unnecessary VNS surgery. Contrary to earlier findings, this validation study suggests that pdBSI might not be helpful to predict VNS therapy outcome

Controlled aggregation of primary human pancreatic islet cells leads to glucose-responsive pseudoislets comparable to native islets

Clinical islet transplantation is a promising treatment for patients with type 1 diabetes. However, pancreatic islets vary in size and shape affecting their survival and function after transplantation because of mass transport limitations. To reduce diffusion restrictions and improve islet cell survival, the generation of islets with optimal dimensions by dispersion followed by reassembly of islet cells, can help limit the length of diffusion pathways. This study describes a microwell platform that supports the controlled and reproducible production of three-dimensional pancreatic cell clusters of human donor islets. We observed that primary human islet cell aggregates with a diameter of 100-150m consisting of about 1000 cells best resembled intact pancreatic islets as they showed low apoptotic cell death

Insulin-like-growth-factor-I enhances proliferation and differentiation of human mesenchymal stromal cells in vitro

Human mesenchymal stromal cells (hMSCs) offer great potential for bone tissue engineering applications, but their in vivo performance remains limited. Pre-conditioning of these cells with small molecules to improve their differentiation prior to implantation or incorporation of growth factors are possible solutions. Insulin-like growth factor-1 (IGF-1) is one of the most abundant growth factors in bone, involved in growth, development and metabolism, but its effects on hMSCs are still subject of debate. Herein, we examined the effects of IGF-1 on proliferation and differentiation of hMSCs in vitro and we found that serum abolished the effects of IGF-1. Only in the absence of serum, IGF-1 increased proliferation, ALP expression and osteogenic gene expression of hMSCs. Furthermore, we examined synergistic effects of BMP-2 and IGF-1 and, although IGF-1 enhanced BMP-2-induced mineralization, IGF-1 only slightly affected in vivo bone formation

Alamar blue and DNA quantification assay results to compare metabolic activity and proliferation of SCs.

<p>(A, C) PHB(50)/PHBV(50) random nanofibers (PHB/PHBV R group) and PHB(50)/PHBV(50) aligned nanofibers (PHB/PHBV A group); (B, D) PHB(50)/PHBV(50) aligned nanofibers (PHB/PHBV A group) and PHB(45)/PHBV(45)/collagen(10) aligned nanofibers (PHB/PHBV/Col group) during 14 days of culture. Asterisks represent significant difference at <i>p</i>≤0.05.</p

Raman spectra of PHB/PHBV nanofibers in different blend compositions.

<p>Raman spectra of PHB/PHBV nanofibers in different blend compositions.</p

SEM images of SCs on PHB(50)/PHBV(50) random (R) and aligned (A) nanofibers.

<p>(A) 1 day, (B) 3 days, and (C) 7 days after cell seeding. Scale bars represent 50 µm for top and 10 µm for button pictures, respectively.</p

SEM images and histograms illustrating the orientation of PHB(50)/PHBV(50) nanofibrous mats.

<p>Nanofibers collected with speed of (A) 1000 rpm, (B) 3000 rpm, (C) 5000 rpm. The voltage, flow rate and collecting conditions were fixed at 16 kV, 1.5 ml/h and 15 cm, respectively. Scale bars represent 20 µm for SEM images.</p