Internalization of isolated functional mitochondria: involvement of macropinocytosis

Abstract

In eukaryotic cells, mitochondrial dysfunction is associated with a variety of human diseases. Delivery of exogenous functional mitochondria into damaged cells has been proposed as a mechanism of cell transplant and physiological repair for damaged tissue. We here demonstrated that isolated mitochondria can be transferred into homogeneic and xenogeneic cells by simple co-incubation using genetically labelled mitochondria, and elucidated the mechanism and the effect of direct mitochondrial transfer. Intracellular localization of exogenous mitochondria was confirmed by PCR, real-time PCR, live fluorescence imaging, three-dimensional reconstruction imaging, continuous time-lapse microscopic observation, flow cytometric analysis and immunoelectron microscopy. Isolated homogeneic mitochondria were transferred into human uterine endometrial gland-derived mesenchymal cells in a dose-dependent manner. Moreover, mitochondrial transfer rescued the mitochondrial respiratory function and improved the cellular viability in mitochondrial DNA-depleted cells and these effects lasted several days. Finally, we discovered that mitochondrial internalization involves macropinocytosis. In conclusion, these data support direct transfer of exogenous mitochondria as a promising approach for the treatment of various diseases.

Mitochondrial transplantation attenuates hypoxic pulmonary hypertension

“…The mechanism(s) involved in transplantation of exogenous mitochondria into smooth muscle cells of pulmonary arteries may be more complicated in vivo than in vitro as reported recently from other lab [16] and ours [8]. In addition to the direct interaction between mitochondrial membrane and cytoplasma membrane and the subsequent processes like fusion and or endocytosis as suggested from recent works of another lab [16] and ours [8], the other possible pathways may be related with the interspace and gap junctional channels between endothelial and smooth muscle cells as well as those between smooth muscle cells, since mitochondrial transfer between cells was reported in very recent studies [17, 18].…”

Mitochondrial Transfer by Photothermal Nanoblade Restores Metabolite Profile in Mammalian Cells

“…A defined ratio of mixed donor mitochondria can also be simultaneously transferred into a cell, which aid in studies of heteroplasmy mtDNA competition, nuclear/mitochondrial genome compatibility, and kinetics of metabolic rewiring. Finally, the nanoblade could dissect mechanisms of inefficient, uncontrolled, and spontaneous cellular uptake of mitochondria without cell fusion (Katrangi et al, 2007; Kitani et al, 2014; Masuzawa et al, 2013). …”

Modifying the Mitochondrial Genome

“…Consistent with the latter results, cellular uptake of mitochondria from the media was discovered to be temperature dependent, could occur between species, and was shown for MDA-MB-435, COLO 205, and MCF-7 cell lines (Katrangi et al, 2007). The incorporation of isolated mitochondria into endometrial gland-derived mesenchymal cells was also shown to be dose-dependent (Kitani et al, 2014a; Kitani et al, 2014b). Rho-zero (ρ0) cells can be generated that lack mtDNA and, therefore, cannot respire or generate ATP by OXPHOS and become uridine auxotrophs due to the inactivation of ETC-dependent dihydroorotate dehydrogenase (King and Attardi, 1989).…”

“…Rho-zero (ρ0) cells can be generated that lack mtDNA and, therefore, cannot respire or generate ATP by OXPHOS and become uridine auxotrophs due to the inactivation of ETC-dependent dihydroorotate dehydrogenase (King and Attardi, 1989). The uptake of isolated mitochondria into ρ0 cells increased cell viability and respiration (Kitani et al, 2014b). The uptake mechanism did not involve clathrin-mediated endocytosis, but data obtained using inhibitors against microtubule assembly, actin polymerization, and Na+/H+ exchange suggested that non-selective macropinocytosis was a key component (Kitani et al, 2014b).…”

“…The uptake of isolated mitochondria into ρ0 cells increased cell viability and respiration (Kitani et al, 2014b). The uptake mechanism did not involve clathrin-mediated endocytosis, but data obtained using inhibitors against microtubule assembly, actin polymerization, and Na+/H+ exchange suggested that non-selective macropinocytosis was a key component (Kitani et al, 2014b). …”