Morphological analysis of human induced pluripotent stem cells during induced differentiation and reverse programming

Area of Science:

• Cell Biology
• Stem Cell Research
• Developmental Biology

Background:

• Comparative analysis of pluripotent cells and human embryonic stem cells (hESCs) is crucial for understanding biological behavior.
• Human mesenchymal stem cells (hMSCs) derived from H9 hESC line were used as a starting point for reprogramming.

Purpose of the Study:

• To compare the morphology of human induced pluripotent stem cells (hiPSCs) with their parental hESCs and originating hMSCs.
• To evaluate the utility of electron microscopy in assessing cellular reprogramming and identifying partially reprogrammed cells.

Main Methods:

• Reprogramming of hMSCs using Oct-4, Sox2, Nanog, and Lin28 transgenes to generate hiPSCs.
• Comparative analysis of hiPSCs, hESCs, and hMSCs using electron microscopy.
• Assessment of cytoplasmic and nuclear features, colony morphology, and cell junctions.

Main Results:

• hiPSCs and hESCs are morphologically indistinguishable, exhibiting features of undifferentiated cells (e.g., abundant ribosomes, scarce reticulum, nuclear plasticity, euchromatin, reticulated nucleoli).
• hiPSCs differ significantly from hMSCs, which lack these undifferentiated features.
• hiPSC colonies displayed epithelial characteristics with specialized junctions, indicating mesenchymal-epithelial transition during successful reprogramming.
• Electron microscopy identified specific morphological traits of partially reprogrammed cells.

Conclusions:

• Electron microscopy is a valuable tool for detailed morphological characterization of hiPSCs and understanding the reprogramming process.
• Morphological similarities between hiPSCs and hESCs confirm successful pluripotency induction.
• The study provides insights into the cellular and ultrastructural changes occurring during mesenchymal-to-epithelial transition in reprogramming.