Endothelial progenitor cells and plaque burden in stented coronary artery segments: an optical coherence tomography study six months after elective PCI.

BACKGROUND: Endothelial progenitor cells (EPC) are involved in neovascularization and endothelial integrity. They might be protective in atherosclerosis. Optical coherence tomography (OCT) is a precise intracoronary imaging modality that allows assessment of subintimal plaque development. We evaluated the influence of EPC on coronary plaque burden in stable disease and implemented a novel computational plaque analysis algorithm using OCT. METHODS: Forty-three patients (69.8% males, 69.6 ± 7.7 years) were investigated by OCT during re-angiography 6 months after elective stent implantation. Different subpopulations of EPCs were identified by flow cytometry according to their co-expression of antigens (CD34+, CD133+, kinase domain receptor, KDR+). An algorithm was applied to calculate the underlying total plaque burden of the stented segments from OCT images. Plaque morphology was assessed according to international consensus in OCT imaging. RESULTS: A cumulative sub-strut plaque volume of 10.87 ± 12.7 mm3 and a sub-stent plaque area of 16.23 ± 17.0 mm2 were found within the stented vessel segments with no significant differences between different stent types. All EPC subpopulations (mean of EPC levels: CD34+/CD133+: 2.66 ± 2.0%; CD34+/KDR+: 7.50 ± 5.0%; CD34+/CD133+/KDR+: 1.12 ± 1.0%) inversely correlated with the identified underlying total plaque volume and plaque area (p ≤ 0.012). CONCLUSIONS: This novel analysis algorithm allows for the first time comprehensive quantification of coronary plaque burden by OCT and illustration as spread out vessel charts. Increased EPC levels are associated with less sub-stent coronary plaque burden which adds to previous findings of their protective role in atherosclerosis.

Monitoring of seven industrial anaerobic digesters supplied with biochar.

BACKGROUND: Recent research articles indicate that direct interspecies electron transfer (DIET) is an alternative metabolic route for methanogenic archaea that improves microbial methane productivity. It has been shown that multiple conductive materials such as biochar can be supplemented to anaerobic digesters to increase the rate of DIET. However, the industrial applicability, as well as the impact of such supplements on taxonomic profiles, has not been sufficiently assessed to date. RESULTS: Seven industrial biogas plants were upgraded with a shock charge of 1.8 kg biochar per ton of reactor content and then 1.8 kg per ton were added to the substrate for one year. A joint analysis for all seven systems showed a decreasing trend for the concentration of acetic acid (p < 0.0001), propionic acid (p < 0.0001) and butyric acid (p = 0.0022), which was significant in all cases. Quantification of the cofactor F420 using fluorescence microscopy showed a reduction in methanogenic archaea by up to a power of ten. Methanogenic archaea could grow within the biochar, even if the number of cells was 4 times less than in the surrounding sludge. 16S-rRNA gene amplicon sequencing showed a higher microbial diversity in the biochar particles than in the sludge, as well as an accumulation of secondary fermenters and halotolerant bacteria. Taxonomic profiles indicate microbial electroactivity, and show the frequent occurrence of Methanoculleus, which has not been described in this context before. CONCLUSIONS: Our results shed light on the interplay between biochar particles and microbial communities in anaerobic digesters. Both the microbial diversity and the absolute frequency of the microorganisms involved were significantly changed between sludge samples and biochar particles. This is particularly important against the background of microbial process monitoring. In addition, it could be shown that biochar is suitable for reducing the content of inhibitory, volatile acids on an industrial scale.