bims-mitrat Biomed News
on Mitochondrial Transplantation and Transfer
Issue of 2024‒04‒07
eight papers selected by
Gökhan Burçin Kubat, Gulhane Health Sciences Institute



  1. bioRxiv. 2024 Mar 20. pii: 2024.03.18.585552. [Epub ahead of print]
      Background: The phenomenon of intercellular mitochondrial transfer from mesenchymal stromal cells (MSCs) has shown promise for improving tissue healing after injury and has potential for treating degenerative diseases like osteoarthritis (OA). Recently MSC to chondrocyte mitochondrial transfer has been documented, but the mechanism of transfer is unknown. Full-length connexin43 (Cx43, encoded by GJA1 ) and the truncated internally translated isoform GJA1-20k have been implicated in mitochondrial transfer between highly oxidative cells, but have not been explored in orthopaedic tissues. Here, our goal was to investigate the role of Cx43 in MSC to chondrocyte mitochondrial transfer. In this study, we tested the hypotheses that (a) mitochondrial transfer from MSCs to chondrocytes is increased when chondrocytes are under oxidative stress and (b) MSC Cx43 expression mediates mitochondrial transfer to chondrocytes.Methods: Oxidative stress was induced in immortalized human chondrocytes using tert-Butyl hydroperoxide (t-BHP) and cells were evaluated for mitochondrial membrane depolarization and reactive oxygen species (ROS) production. Human bone-marrow derived MSCs were transduced for mitochondrial fluorescence using lentiviral vectors. MSC Cx43 expression was knocked down using siRNA or overexpressed (GJA1+ and GJA1-20k+) using lentiviral transduction. Chondrocytes and MSCs were co-cultured for 24 hrs in direct contact or separated using transwells. Mitochondrial transfer was quantified using flow cytometry. Co-cultures were fixed and stained for actin and Cx43 to visualize cell-cell interactions during transfer.
    Results: Mitochondrial transfer was significantly higher in t-BHP-stressed chondrocytes. Contact co-cultures had significantly higher mitochondrial transfer compared to transwell co-cultures. Confocal images showed direct cell contacts between MSCs and chondrocytes where Cx43 staining was enriched at the terminal ends of actin cellular extensions containing mitochondria in MSCs. MSC Cx43 expression was associated with the magnitude of mitochondrial transfer to chondrocytes; knocking down Cx43 significantly decreased transfer while Cx43 overexpression significantly increased transfer. Interestingly, GJA1-20k expression was highly correlated with incidence of mitochondrial transfer from MSCs to chondrocytes.
    Conclusions: Overexpression of GJA1-20k in MSCs increases mitochondrial transfer to chondrocytes, highlighting GJA1-20k as a potential target for promoting mitochondrial transfer from MSCs as a regenerative therapy for cartilage tissue repair in OA.
    DOI:  https://doi.org/10.1101/2024.03.18.585552
  2. Neurotherapeutics. 2024 Apr 04. pii: S1878-7479(24)00041-2. [Epub ahead of print] e00355
      Mitochondria are essential organelles for cell survival that manage the cellular energy supply by producing ATP. Mitochondrial dysfunction is associated with various human diseases, including metabolic syndromes, aging, and neurodegenerative diseases. Among the diseases related to mitochondrial dysfunction, Parkinson's disease (PD) is the second most common neurodegenerative disease and is characterized by dopaminergic neuronal loss and neuroinflammation. Recently, it was reported that mitochondrial transfer between cells occurred naturally and that exogenous mitochondrial transplantation was beneficial for treating mitochondrial dysfunction. The current study aimed to investigate the therapeutic effect of mitochondrial transfer on PD in vitro and in vivo. The results showed that PN-101 mitochondria isolated from human mesenchymal stem cells exhibited a neuroprotective effect against 1-methyl-4-phenylpyridinium, 6-hydroxydopamine and rotenone in dopaminergic cells and ameliorated dopaminergic neuronal loss in the brains of C57BL/6J mice injected 30 ​mg/kg of methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intraperitoneally. In addition, PN-101 exhibited anti-inflammatory effects by reducing the expression of pro-inflammatory cytokines in microglial cells and suppressing microglial activation in the striatum. Furthermore, intravenous mitochondrial treatment was associated with behavioral improvements during the pole test and rotarod test in the MPTP-induced PD mice. These dual effects of neuroprotection and anti-neuroinflammation support the potential for mitochondrial transplantation as a novel therapeutic strategy for PD.
    Keywords:  Mitochondria; Mitotherapy; Neuroprotective; Parkinson's disease; Transplantation
    DOI:  https://doi.org/10.1016/j.neurot.2024.e00355
  3. Mol Neurobiol. 2024 Apr 04.
      Diabetes-associated cognitive dysfunction (DACD) has ascended to become the second leading cause of mortality among diabetic patients. Phosphoserine phosphatase (PSPH), a pivotal rate-limiting enzyme in L-serine biosynthesis, has been documented to instigate the insulin signaling pathway through dephosphorylation. Concomitantly, CD38, acting as a mediator in mitochondrial transfer, is activated by the insulin pathway. Given that we have demonstrated the beneficial effects of exogenous mitochondrial supplementation on DACD, we further hypothesized whether astrocytic PSPH could contribute to improving DACD by promoting astrocytic mitochondrial transfer into neurons. In the Morris Water Maze (MWM) test, our results demonstrated that overexpression of PSPH in astrocytes alleviated DACD in db/db mice. Astrocyte specific-stimulated by PSPH lentivirus/ adenovirus promoted the spine density both in vivo and in vitro. Mechanistically, astrocytic PSPH amplified the expression of CD38 via initiation of the insulin signaling pathway, thereby promoting astrocytic mitochondria transfer into neurons. In summation, this comprehensive study delineated the pivotal role of astrocytic PSPH in alleviating DACD and expounded upon its intricate cellular mechanism involving mitochondrial transfer. These findings propose that the specific up-regulation of astrocytic PSPH holds promise as a discerning therapeutic modality for DACD.
    Keywords:  Diabetes-associated cognitive dysfunction (DACD); Hippocampus; Mitochondrial transfer; PSPH
    DOI:  https://doi.org/10.1007/s12035-024-04064-0
  4. EMBO Rep. 2024 Apr 02.
      Most mitochondrial proteins are synthesized on cytosolic ribosomes and imported into mitochondria in a post-translational reaction. Mitochondrial precursor proteins which use the ER-SURF pathway employ the surface of the endoplasmic reticulum (ER) as an important sorting platform. How they reach the mitochondrial import machinery from the ER is not known. Here we show that mitochondrial contact sites play a crucial role in the ER-to-mitochondria transfer of precursor proteins. The ER mitochondria encounter structure (ERMES) and Tom70, together with Djp1 and Lam6, are part of two parallel and partially redundant ER-to-mitochondria delivery routes. When ER-to-mitochondria transfer is prevented by loss of these two contact sites, many precursors of mitochondrial inner membrane proteins are left stranded on the ER membrane, resulting in mitochondrial dysfunction. Our observations support an active role of the ER in mitochondrial protein biogenesis.
    Keywords:  Contact sites; ERMES; Endoplasmic reticulum; Mitochondria; Protein import
    DOI:  https://doi.org/10.1038/s44319-024-00113-w
  5. Biochem Cell Biol. 2024 Apr 03.
      Cell-in-cell (CIC) structures have been suggested to mediate intracellular substance transport between cells and have been found widely in inflammatory lung tissue of asthma. The aim of this study was to investigate the significance of CIC structures in inflammatory progress of asthma. CIC structures and related inflammatory pathways were analyzed in asthmatic lung tissue and normal lung tissue of mouse model. In vitro, the activation of inflammatory pathways by CIC-mediated intercellular communication was analyzed by RNA-Seq and verified by Western blotting and immunofluorescence. Results showed that CIC structures of lymphocytes and alveolar epithelial cells in asthmatic lung tissue mediated intercellular substance (such as mitochondria) transfer and promoted pro-inflammation in two phases. At early phase, internal lymphocytes triggered inflammasome-dependent pro-inflammation and cell death of itself. Then, degraded lymphocytes released cellular contents such as mitochondria inside alveolar epithelial cells, further activated multi-pattern-recognition receptors and NF-kappa B signaling pathways of alveolar epithelial cells, and thereby amplified pro-inflammatory response in asthma. Our work supplements the mechanism of asthma pro-inflammation progression from the perspective of CIC structure of lymphocytes and alveolar epithelial cells, and provides a new idea for anti-inflammatory therapy of asthma.
    Keywords:  asthma; cell-in-cell; inflammasome; mitochondria transfer; pro-inflammation
    DOI:  https://doi.org/10.1139/bcb-2023-0228
  6. Am J Transplant. 2024 Apr;pii: S1600-6135(24)00173-4. [Epub ahead of print]24(4): 509-511
      
    DOI:  https://doi.org/10.1016/j.ajt.2024.03.001
  7. bioRxiv. 2024 Mar 22. pii: 2024.03.21.586162. [Epub ahead of print]
      Mitochondria are highly dynamic double membrane-bound organelles that exist in a semi- continuous network. Mitochondrial morphology arises from the complex interplay of numerous processes, including opposing fission and fusion dynamics and the formation of highly organized cristae invaginations of the inner membrane. While extensive work has examined the mechanisms of mitochondrial fission, it remains unclear how fission is coordinated across two membrane bilayers and how mitochondrial inner membrane organization is coupled with mitochondrial fission dynamics. Previously, the yeast protein Mdm33 was implicated in facilitating fission by coordinating with inner membrane homeostasis pathways. However, Mdm33 is not conserved outside fungal species and its precise mechanistic role remains unclear. Here, we use a bioinformatic approach to identify a putative structural ortholog of Mdm33 in humans, CCDC51 (also called MITOK). We find that the mitochondrial phenotypes associated with altered CCDC51 levels implicate the protein in mitochondrial fission dynamics. Further, using timelapse microscopy, we spatially and temporally resolve Mdm33 and CCDC51 to a subset of mitochondrial fission events. Finally, we show that CCDC51 can partially rescue yeast Δ mdm33 cells, indicating the proteins are functionally analogous. Our data reveal that Mdm33/CCDC51 are conserved mediators of mitochondrial morphology and suggest the proteins play a crucial role in maintaining normal mitochondrial dynamics and organelle homeostasis.
    DOI:  https://doi.org/10.1101/2024.03.21.586162
  8. Nanoscale. 2024 Apr 04.
      Extracellular vesicles (EVs) are cell-derived nanoparticles that carry small molecules, nucleic acids, and proteins long distances in the body facilitating cell-cell communication. Microorganism-derived EVs mediate communication between parent cells and host cells, with recent evidence supporting their role in biofilm formation, horizontal gene transfer, and suppression of the host immune system. As lipid-bound bacterial byproducts, EVs demonstrate improved cellular uptake and distribution in vivo compared to cell-free nucleic acids, proteins, or small molecules, allowing these biological nanoparticles to recapitulate the effects of parent cells and contribute to a range of human health outcomes. Here, we focus on how EVs derived from vaginal microorganisms contribute to gynecologic and obstetric outcomes. As the composition of the vaginal microbiome significantly impacts women's health, we discuss bacterial EVs from both healthy and dysbiotic vaginal microbiota. We also examine recent work done to evaluate the role of EVs from common vaginal bacterial, fungal, and parasitic pathogens in pathogenesis of female reproductive tract disease. We highlight evidence for the role of EVs in women's health, gaps in current knowledge, and opportunities for future work. Finally, we discuss how leveraging the innate interactions between microorganisms and mammalian cells may establish EVs as a novel therapeutic modality for gynecologic and obstetric indications.
    DOI:  https://doi.org/10.1039/d3nr05524h