The fine analysis of cell components during the generation of pluripotent cells and their comparison to bone fide human embryonic stem cells (hESCs) are valuable tools to understand their biological behavior. In this report, human mesenchymal cells (hMSCs) generated from the human ES cell line H9, were reprogrammed back to induced pluripotent state using Oct-4, Sox2, Nanog, and Lin28 transgenes. Human induced pluripotent stem cells (hIPSCs) were analyzed using electron microscopy and compared with regard to the original hESCs and the hMSCs from which they were derived. This analysis shows that hIPSCs and the original hESCs are morphologically undistinguishable but differ from the hMSCs with respect to the presence of several morphological features of undifferentiated cells at both the cytoplasmic (ribosomes, lipid droplets, glycogen, scarce reticulum) and nuclear levels (features of nuclear plasticity, presence of euchromatin, reticulated nucleoli). We show that hIPSC colonies generated this way presented epithelial aspects with specialized junctions highlighting morphological criteria of the mesenchymal–epithelial transition in cells engaged in a successful reprogramming process. Electron microscopic analysis revealed also specific morphological aspects of partially reprogrammed cells. These results highlight the valuable use of electron microscopy for a better knowledge of the morphological aspects of IPSC and cellular reprogramming.

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The aims of the study were to measure the collagen content in pancreas using a colorimetric method and to compare the amount of collagen in normal pancreas (11 cases), diffuse fibrosing pancreatitis (17 cases), and chronic calcifying pancreatitis (11 cases). The procedure of fibrosis measurement was based on the selective capacity of two dyes, Sirius red and fast green, to set on collagen and noncoUagenous proteins, respectively. After staining of sections, colors were eluted from the sections and the specific absorbance of each eluted dye was read on a spectrophotometer. The collagen content in normal pancreata was 26.5 ± 7.2 μg collagen/mg protein. The amount of collagen increased with the age of patients: the mean value of the patients under the age of 50 was 18.2 ± 4 μg collagen/mg protein whereas the mean value in older patients was 31.9 ± 8 μg collagen/mg protein (p < 0.01). The value of collagen in pancreas with a diffuse fibrosing pancreatitis was 44.7 ± 7.5 μg collagen/mg protein. This value was significantly different from the collagen content in normal pancreas (p < 0.001) and in pancreas with a chronic calcifying pancreatitis (77.9 ± 8 μg collagen/mg protein, p < 0.001). This method permits discrimination between different chronic diseases that can also be differentiated on a histopathologic basis.

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