Effects of Cell Density and Microenvironment on Stem Cell Mitochondria Transfer among Human Adipose-Derived Stem Cells and HEK293 Tumorigenic Cells

Abstract

Stem cells (SC) are largely known for their potential to restore damaged tissue through various known mechanisms. Among these mechanisms is their ability to transfer healthy mitochondria to injured cells to rescue them. This mitochondrial transfer plays a critical role in the healing process. To determine the optimal parameters for inducing mitochondrial transfer between cells, we assessed mitochondrial transfer as a function of seeding density and in two-dimensional (2D) and semi three-dimensional (2.5D) culture models. Since mitochondrial transfer can occur through direct contact or secretion, the 2.5D culture model utilizes collagen to provide cells with a more physiologically relevant extracellular matrix and offers a more realistic representation of cell attachment and movement. Results demonstrate the dependence of mitochondrial transfer on cell density and the distance between donor and recipient cell. Furthermore, the differences found between the transfer of mitochondria in 2D and 2.5D microenvironments suggest an optimal mode of mitochondria transport. Using these parameters, we explored the effects on mitochondrial transfer between SCs and tumorigenic cells. HEK293 (HEK) is an immortalized cell line derived from human embryonic kidney cells which grow rapidly and form tumors in culture. Consequently, HEKs have been deemed tumorigenic and are widely used in cancer research. We observed mitochondrial transfer from SCs to HEK cells at significantly higher transfer rates when compared to a SC–SC co-culture system. Interestingly, our results also revealed an increase in the migratory ability of HEK cells when cultured with SCs. As more researchers find co-localization of stem cells and tumors in the human body, these results could be used to better understand their biological relationship and lead to enhanced therapeutic applications.

Mitochondrial transfer in tunneling nanotubes—a new target for cancer therapy

“…The transfer of mitochondria from stem cells to immortalized cells rapidly induces tumorigenesis. For instance, the transfer of mitochondria from adipose stem cells to HEK293 cells not only makes them more tumorigenic but also enhances their aggressiveness [ 53 ]. In gliomas, the uptake of astrocyte mitochondria promotes cell cycle progression to the proliferative G2/M phase, enhancing self-renewal and tumorigenicity of GBM cells [ 54 , 55 ].…”

“…Increased invasiveness and metastasis [13] Lung cancer cells and CD8 + T cell Endocytosis (CICs) Unidirectional from lymphocyte to Lung cancer cells Increased proliferation and immune escape [17] Cancer cells and endothelial cells TNTs Bidirectional between endothelial cells and cancer cells Increased Chemotherapy resistance [18] Cancer cells and platelet TNTs Unidirectional from platelet to cancer cells Promoted metastasis and reduced oxidative stress [20] Adipose stem cells and HEK293 TNTs Unidirectional from Adipose stem cells to HEK293 Enhanced tumorigenicity [53] PCa cells and CAFs TNTs Unidirectional from CAFs to PCa cells Increased invasiveness and metastasis [58] Chemotherapy-resistant TNBC cells and TNBC cells TNTs Unidirectional from Chemotherapy-resistant TNBC cells to TNBC cells Increased Chemotherapy resistance [80] Melanoma cells and MSCs TNTs Unidirectional from MSCs to Melanoma cells Increased proliferation [56] cytochrome C (cytC), thereby activating apoptotic protease activating factor 1 (Apaf1) to induce the formation of the apoptosome, which then activates Caspase 9 and Caspase 3, triggering apoptosis [91] (Fig. 7).…”

Recent Development of Advanced Fluorescent Molecular Probes for Organelle-Targeted Cell Imaging

“…The microenvironment is also important for the activity of mitochondria, since most of the enzymes are influenced by pH, temperature, and even the viscosity of the surroundings [ 101 ]. Using a piperazine-linked naphthalimide as the pH sensor moiety and TPP as the guider, Lee et al synthesized a probe ( 25 , Scheme 3 ) for the real-time monitoring of pH change in mitochondria in living cells [ 102 ].…”