Aberrant CHCHD2-Associated Mitochondriopathy in Kii ALS/PDC Astrocytes

Medical Laboratory Science Neurology Biochemistry Life Sciences Immunology Medicine Cell Biology
ALS PDC Kii ALS/PDC CHCHD2 astrocytes mitochondria

Study Report on Abnormal CHCHD2-Related Mitochondrial Pathology in Astrocytes in Kii ALS/PDC

I. Research Background

Amyotrophic lateral sclerosis/Parkinsonism-dementia complex (ALS/PDC) is a rare and complex neurodegenerative disorder primarily observed in Western Pacific islands such as Japan, Guam, and Papua New Guinea. Patients with this disease exhibit symptoms characteristic of classical ALS or Parkinson’s disease (PD). Autopsy findings reveal accumulations of α-synuclein and TDP-43 proteins, markers of PD and ALS, respectively. Additionally, phosphorylated tau protein is detected, further complicating the disease’s protein pathology. Despite research into various factors influencing this disease, its etiology remains unclear. Increasing evidence suggests that astrocytes, cells crucial for maintaining brain health, may play a significant role in the pathogenesis of ALS/PDC. This study utilized induced pluripotent stem cell (iPSC) technology to cultivate various astrocyte cell lines to further investigate ALS/PDC in the Kii region of Japan (referred to as Kii ALS/PDC), focusing particularly on the role of the CHCHD2 gene in the disease.

II. Research Source

This paper was co-authored by Nicolas Leventoux, Satoru Morimoto, and others from institutions such as Keio University and Mie University. The article was published in the 2024 issue of the journal Acta Neuropathologica.

III. Research Process

a) Research Process and Methods

The research was conducted in the following steps:

  1. Donor Selection and Approval: Diagnoses were conducted at Minamiise Municipal Hospital and Higashi-Nagoya National Hospital. All patients had a family history and exhibited at least Parkinson’s disease and motor neuron disease (MND), with four cases accompanied by dementia.

  2. Generation and Characterization of iPSCs: iPSCs were generated from peripheral blood T cells of Kii ALS/PDC patients. The activated T cells were fused with circular plasmid vectors through electroporation, followed by culture and chromosomal integrity assessment.

  3. Differentiation of iPSCs into Astrocytes: A multi-step differentiation process was used to culture iPSCs into embryoid bodies (EBs) in suspension. The cells were then induced to differentiate into neural lineages using retinoic acid and purmorphamine, expanded with epidermal growth factor and basic fibroblast growth factor, and purified to isolate astrocytes.

  4. Immunofluorescence and RNA Sequencing: The astrocytes differentiated from iPSCs were characterized and analyzed using immunofluorescence and RNA sequencing.

  5. Mitochondrial Function Testing: Mitochondrial respiration was assessed by measuring oxygen consumption and extracellular acidification rates, and the effects of the drug Elamipretide on astrocytes were evaluated.

b) Key Results

  1. Generation and Characterization of iPSCs: Multiple iPSCs were successfully generated from patients, and their pluripotency was confirmed through chromosomal analysis, alkaline phosphatase staining, and quantitative RT-PCR for pluripotency markers.

  2. Generation and Characteristics of Astrocytes: Astrocytes were successfully derived from Kii ALS/PDC patients, displaying typical astrocytic characteristics, including high expression of GFAP and S100B, with significant upregulation of GJA1. Some cells exhibited abnormal aggregation of TDP-43.

  3. Mitochondrial Function and Structural Abnormalities: RNA sequencing revealed a series of mitochondrial-related gene expression abnormalities, particularly a significant reduction in CHCHD2 expression. Further immunofluorescence and electron microscopy confirmed that CHCHD2 deficiency led to abnormal mitochondrial morphology and function, characterized by damage to the mitochondrial inner membrane cristae.

  4. Impact on Astrocyte Function: The reduction in CHCHD2 expression resulted in decreased glutamate uptake capacity in astrocytes, with notable impairments in mitochondrial ATP production and respiration. Treatment with Elamipretide and overexpression of CHCHD2 partially restored mitochondrial function in some astrocytes.

c) Research Conclusions

The findings indicate that astrocytes in Kii ALS/PDC patients exhibit abnormal CHCHD2 expression, leading to mitochondrial morphological and functional damage, thereby affecting the survival and health of brain cells. The study highlights the potential role of CHCHD2 in maintaining mitochondrial health and its involvement in ALS/PDC pathology, suggesting the possibility of gene therapy targeting CHCHD2.

d) Research Highlights

  1. Association of CHCHD2 Expression with Mitochondrial Pathology: This is the first confirmation of a direct association between CHCHD2 expression and mitochondrial pathology in astrocytes from Kii ALS/PDC patients.

  2. Role of Astrocytes: The study provides new insights into the potential role of astrocytes in neurodegenerative diseases, offering a fresh perspective on understanding ALS/PDC pathology.

  3. Multidisciplinary Approach: The comprehensive analysis of astrocyte pathology using iPSC technology, RNA sequencing, immunofluorescence, and electron microscopy presents a multidisciplinary approach.

  4. Therapeutic Potential: The findings provide a theoretical foundation for CHCHD2-based gene therapy, offering new hope for ALS/PDC patients.

IV. Important Information and Discussion

This paper highlights the potential significant role of astrocytes in ALS/PDC pathology, and the close association between CHCHD2 dysfunction and the disease’s pathogenesis. Although the specific role of CHCHD2 in neurodegenerative diseases requires further study, the findings of this study undoubtedly guide future research and provide an important basis for developing new therapeutic strategies. Future research could further verify the role of CHCHD2 in other neurodegenerative diseases and explore the efficacy and safety of CHCHD2-based therapeutic approaches.

By employing advanced technologies, this study reveals the pathological characteristics of astrocytes in Kii ALS/PDC patients, offering new insights and potential therapeutic avenues, thus making a significant contribution to neuroscience research.