Rapid screening for MTHFR gene 677C>T polymorphism in Down syndrome using high resolution melting curve and pyrosequencing / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To establish a rapid method for detecting MTHFR gene 677C>T polymorphisms with high-resolution melting curve method (HRM) and pyrosequencing.</p><p><b>METHODS</b>Peripheral blood samples were collected from 155 Down syndrome patients and 182 normal controls from Children's Hospital of Shanghai. The accuracy of three methods including regular HRM, internal control HRM and artificial heterozygosity HRM was compared. Meanwhile, allele frequencies in 10, 30 and 50 mixed samples were measured with pyrosequencing, and the results were compared with that of HRM.</p><p><b>RESULTS</b>Heterozygosity of 677C>T polymorphism could be distinguished by various HRM methods. However, homozygotes CC and TT were only identifiable by internal control HRM and artificial heterozygosity HRM. The accuracy of pyrosequencing for allele frequency has improved with increased sample number. When the number of mixed samples has exceeded 30, the difference between pyrosequencing results and actual values became less than 4%. TT genotype was more frequent in Down syndrome patients than controls (25.2% vs. 14.3%). No significant difference was found in T allele frequency between the two groups (44.9% vs. 40.1%).</p><p><b>CONCLUSION</b>Respectively, internal control HRM and pyrosequencing may be ideal methods for determination of genotypic and allelic frequencies.</p>

AKT-modified autologous intracoronary mesenchymal stem cells prevent remodeling and repair in swine infarcted myocardium / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Transplantation of adult bone marrow-derived mesenchymal stem cells (MSCs) has been proposed as a strategy for cardiac repair following myocardial damage. However cell transplantation strategies to replace lost myocardium are limited by the inability to deliver large numbers of cells that resist peritransplantation graft cell death. Accordingly, we set out to isolate and expand adult swine bone marrow-derived MSCs, and to engineer these cells to overexpress AKT1 (protein kinase B), to test the hypothesis that AKT1-engineered MSCs are more resistant to apoptosis and can enhance cardiac repair after transplantation into the ischemic swine heart.</p><p><b>METHODS</b>The CDS (regulation domain of AKT1) AKT1-cDNA fragment was amplified, and MSCs were transfected following synthesis with a pCDH1-AKT1 shuttling plasmid. Western blotting analysis and real-time reverse transcription-polymerase chain reaction (RT-PCR) was performed. Myocardial infarction (MI) models were constructed in Meishan pigs, and cardiac function was evaluated by magnetic resonance imaging (MRI) measurements and echocardiography 4 weeks later. All pigs were assigned to four groups: control (A), DMEM (B), MSC (C), and AKT-transfected (D). MSCs were transfected with the AKT1 gene, and autologous BrdU-labeled stem cells (1 x 10(7)/5 ml) were injected into left anterior descending coronary atery (LAD) of the infarct heart in groups C and D. In group B, DMEM was injected using the same approach. In group A, there was no injection following LAD occlusion. After 4 weeks, cardiac function and regional perfusion measurements were repeated by MRI and echocardiography, and histological characteristics of the hearts were assessed. Connecxin-43 (CX-43), BrdU, and von Willebrand factor (VWF) immunoreactivity was tested using enzyme linked immunosorbent assay (ELISA). Vascular endothelial growth factor (VEGF), transforming growth factor-beta1 (TGF-beta1) were analyzed at the same time.</p><p><b>RESULTS</b>AKT1-cDNA was cloned into pCDH1-MCS1-EF1-copGFP and the sequence was confirmed. AKT mRNA expression was detected at 24 hours after transfection. AKT1 expression in MSCs remained strong after 2 weeks, according to real-time RT-PCR and Western blotting. Prior to cell implantation, end-diastolic left ventricular dimension (EDLVd) increased and stroke volume (SV) decreased in the MI hearts. MRI scans revealed significantly improved cardiac function following implantation, and implanted MSCs prevented thinning and expanding in the infarct region, as well as improved contraction and increased perfusion in all groups compared to control hearts. The left ventricular chamber size was smaller in cell-transplanted hearts than in control hearts. Moreover, group D exhibited significant improvement. The expression of CX-43, BrdU, and VWF could be found in the immunohistochemical pathological sections of group C and group D. The level of VEGF reached a high level 1 week after implanting the MSCs, but the level of TGF-beta1 decreased gradually.</p><p><b>CONCLUSIONS</b>The AKT1-expressing lentiviral vector resulted in stable over-expression of AKT1 in MSCs. MSC engraftment in host myocardium improved cardiac function by attenuating contractile dysfunction and pathological thinning of the infracted left ventricular wall, which likely resulted from myocardial regeneration and angiogenesis.</p>