Hematopoietic stem cell transplantation prevents diabetes in NOD mice but does not contribute to significant islet cell regeneration once disease is established

The treatment of type I diabetes by islet cell transplantation, while promising, remains restricted due to the incomplete efficacy and toxicity associated with current immunosuppression, and by limited organ availability. Given reports suggesting bone marrow derived stem cell plasticity, we sought to determine whether such cells could give rise to pancreatic islet cells in vivo. In the context of autoimmune diabetes, we transplanted unfractionated bone marrow from beta-gal trangenic donor mice into NOD mice prior to, at, and two weeks beyond the onset of disease. Successful bone marrow engraftment before diabetes onset prevented disease in all mice and for 1 year after transplant. However, despite obtaining full hematopoietic engraftment in over 50 transplanted mice, only one mouse became insulin independent, and no beta-Gal positive islets were detected in any of the mice. To test whether tolerance to islets was achieved, we injected islets obtained from the same allogeneic donor strain as the hematopoietic cells into 4 transplant recipients, and 2 had a reversion of their diabetes. Thus allogeneic bone marrow transplantation prevents autoimmune diabetes and tolerizes the recipient to donor islet grants, even in diabetic animals, yet the capacity of bone marrow derived cells to differentiate into functional islet cells, at least without additional manipulation, is limited in our model.     

Atrial rhythm influences catheter tissue contact during radiofrequency catheter ablation of atrial fibrillation: comparison of contact force between sinus rhythm and atrial fibrillation

Catheter tissue contact force (CF) is an important factor for durable lesion formation during radiofrequency catheter ablation (RFCA) of atrial fibrillation (AF). Since CF varies in the beating heart, atrial rhythm during RFCA may influence CF. A high-density map and RFCA points were obtained in 25 patients undergoing RFCA of AF using a CF-sensing catheter (Tacticath, St. Jude Medical). The operators were blinded to the CF information. Contact type was classified into three categories: constant, variable, and intermittent contact. Average CF and contact type were analyzed according to atrial rhythm (SR vs. AF) and anatomical location. A total of 1364 points (891 points during SR and 473 points during AF) were analyzed. Average CFs showed no significant difference between SR (17.2 ± 11.3 g) and AF (17.2 ± 13.3 g; p = 0.99). The distribution of points with an average CF of ≥20 and <10 g also showed no significant difference. However, the distribution of excessive CF (CF ≥40 g) was significantly higher during AF (7.4 %) in comparison with SR (4.2 %; p < 0.05). At the anterior area of the right inferior pulmonary vein (RIPV), the average CF during AF was significantly higher than during SR (p < 0.05). Constant contact was significantly higher during AF (32.2 %) when compared to SR (9.9 %; p < 0.01). Although the average CF was not different between atrial rhythms, constant contact was more often achievable during AF than it was during SR. However, excessive CF also seems to occur more frequently during AF especially at the anterior part of RIPV.     

Induction and repair of DNA double-strand breaks in blood lymphocytes of patients undergoing 18F-FDG PET/CT examinations

Purpose

The purpose of this study was to evaluate DNA double-strand breaks (DSBs) in blood lymphocytes of patients undergoing positron emission tomography (PET)/CT using γ-H2AX immunofluorescence microscopy and to differentiate between ¹⁸F-fluorodeoxyglucose (FDG) and CT-induced DNA lesions.

Methods

This study was approved by the local Ethics Committee and complies with Health Insurance Portability and Accountability Act (HIPAA) requirements. After written informed consent was obtained, 33 patients underwent whole-body ¹⁸F-FDG PET/CT (3?MBq/kg body weight, 170/100 reference mAs at 120?kV). The FDG PET and CT portions were performed as an initial CT immediately followed by the PET. Blood samples were obtained before, at various time points following ¹⁸F-FDG application and up to 24?h after the CT scan. Distinct foci representing DSBs were quantified in isolated lymphocytes using fluorescence microscopy after staining against the phosphorylated histone variant γ-H2AX.

Results

The DSB values at the various time points were significantly different (p?<?0.001). The median baseline level was 0.08/cell (range 0.06–0.12/cell). Peaks of radiation-induced DSBs were found 30?min after ¹⁸F-FDG administration (median excess foci 0.11/cell, range 0.06–0.27/cell) and 5?min after CT (median excess foci 0.17/cell, range 0.05–0.54/cell). A significant correlation between CT-induced DSBs and dose length product was obtained (ρ?=?0.898, p?<?0.001). After 24?h DSB values were still slightly but significantly elevated (median foci 0.11/cell, range 0.10–0.14/cell, p?=?0.003) compared to pre-exposure levels.

Conclusion

PET/CT-induced DSBs can be monitored using γ-H2AX immunofluorescence microscopy. Peak values may be obtained 30?min after ¹⁸F-FDG injection and 5?min after CT. The radionuclide contributes considerably to the total DSB induction in this setting.