Amyloid-β oligomers are a cytotoxic structure that is key for the establishment of the beginning stages of Alzheimer’s disease (AD). These structures promote subcellular alterations that cause synaptic dysfunction, loss of cell communication, and even cell death, generating cognitive deficits. The aim of this study was to investigate the cytotoxic effects of amyloid-β1-42 oligomers (AβOs) on the membranous organelles involved in protein processing: the endoplasmic reticulum (ER) and Golgi apparatus (GA). The results obtained with 10 μM AβOs in SH-SY5Y neuroblastoma cells showed that oligomeric structures are more toxic than monomers because they cause cell viability to decrease as exposure time increases. Survivor cells were analyzed to further understand the toxic effects of AβOs on intracellular organelles. Survivor cells showed morphological alterations associated with abnormal cytoskeleton modification 72–96 h after exposure to AβOs. Moreover, the ER and GA presented rearrangement throughout the cytoplasmic space, which could be attributed to a lack of constitutive protein processing or to previous abnormal cytoskeleton modification. Interestingly, the disorganization of both ER and GA organelles exposed to AβOs is likely an early pathological alteration that could be related to aberrant protein processing and accumulation in AD.

Mesenchymal stem cells (MSCs) are multipotent precursor cells with the ability to self-renew and differentiate into multiple cell linage, including the Schwann-like fate that promotes regeneration after lesion. Raman spectroscopy provides a precise characterization of the osteogenic, adipogenic, hepatogenic and myogenic differentiation of MSCs. However, the differentiation of bone marrow mesenchymal stem cells (BMSCs) towards a glial phenotype (Schwann-like cells) has not been characterized before using Raman spectroscopy. We evaluated three conditions: 1) cell culture from rat bone marrow undifferentiated (uBMSCs), and two conditions of differentiation; 2) cells exposed to olfactory ensheathing cells-conditioned medium (dBMSCs) and 3) cells obtained from olfactory bulb (OECs). uBMSCs phenotyping was confirmed by morphology, immunocytochemistry and flow cytometry using antibodies of cell surface: CD90 and CD73. Glial phenotype of dBMSCs and OECs were verified by morphology and immunocytochemistry using markers of Schwann-like cells and OECs such as GFAP, p75 NTR and O4. Then, the Principal Component Analysis (PCA) of Raman spectroscopy was performed to discriminate components from the high wavenumber region between undifferentiated and glial-differentiated cells. Raman bands at the fingerprint region also were used to analyze the differentiation between conditions. Differences between Raman spectra from uBMSC and glial phenotype groups were noted at multiple Raman shift values. A significant decrease in the concentration of all major cellular components, including nucleic acids, proteins, and lipids were found in the glial phenotype groups. PCA analysis confirmed that the highest spectral variations between groups came from the high wavenumber region observed in undifferentiated cells and contributed with the discrimination between glial phenotype groups. These findings support the use of Raman spectroscopy for the characterization of uBMSCs and its differentiation in the glial phenotype.

Olfactory ensheathing cells (OECs) and mesenchymal stem cells (MSCs) differentiated towards Schwann-like have plasticity properties. These cells express the Glial fibrillary acidic protein (GFAP), a type of cytoskeletal protein that significantly regulates many cellular functions, including those that promote cellular plasticity needed for regeneration. However, the expression of GFAP isoforms (α, β, and δ) in these cells has not been characterized. We evaluated GFAP isoforms (α, β, and δ) expression by Polymerase Chain Reaction (PCR) assay in three conditions: (1) OECs, (2) cells exposed to OECs-conditioned medium and differentiated to Schwann-like cells (dBM-MSCs), and (3) MSC cell culture from rat bone marrow undifferentiated (uBM-MSCs). First, the characterization phenotyping was verified by morphology and immunocytochemistry, using p75, CD90, and GFAP antibodies. Then, we found the expression of GFAP isoforms (α, β, and δ) in the three conditions; the expression of the GFAPα (10.95%AUC) and GFAPβ (9.17%AUC) isoforms was predominantly in OECs, followed by dBM-MSCs (α: 3.99%AUC, β: 5.66%AUC) and uBM-MSCs (α: 2.47%AUC, β: 2.97%AUC). GFAPδ isoform has a similar expression in the three groups (OEC: 9.21%AUC, dBM-MSCs: 11.10%AUC, uBM-MSCs: 9.21%AUC). These findings suggest that expression of different GFAPδ and GFAPβ isoforms may regulate cellular plasticity properties, potentially contributing to tissue remodeling processes by OECs, dBM-MSCs, and uBM-MSCs.

The journal retracts the article “Cytotoxic Effect of Amyloid-β1-42 Oligomers on Endoplasmic Reticulum and Golgi Apparatus Arrangement in SH-SY5Y Neuroblastoma Cells”