Mitochondrial Transfer and Regulators of Mesenchymal Stromal Cell Function and Therapeutic Efficacy.

Amina Mohammadalipour,Pamela L Wenzel,Sandeep P Dumbali

doi:10.3389/fcell.2020.603292

Abstract

Mesenchymal stromal cell (MSC) metabolism plays a crucial role in the surrounding microenvironment in both normal physiology and pathological conditions. While MSCs predominantly utilize glycolysis in their native hypoxic niche within the bone marrow, new evidence reveals the importance of upregulation in mitochondrial activity in MSC function and differentiation. Mitochondria and mitochondrial regulators such as sirtuins play key roles in MSC homeostasis and differentiation into mature lineages of the bone and hematopoietic niche, including osteoblasts and adipocytes. The metabolic state of MSCs represents a fine balance between the intrinsic needs of the cellular state and constraints imposed by extrinsic conditions. In the context of injury and inflammation, MSCs respond to reactive oxygen species (ROS) and damage-associated molecular patterns (DAMPs), such as damaged mitochondria and mitochondrial products, by donation of their mitochondria to injured cells. Through intercellular mitochondria trafficking, modulation of ROS, and modification of nutrient utilization, endogenous MSCs and MSC therapies are believed to exert protective effects by regulation of cellular metabolism in injured tissues. Similarly, these same mechanisms can be hijacked in malignancy whereby transfer of mitochondria and/or mitochondrial DNA (mtDNA) to cancer cells increases mitochondrial content and enhances oxidative phosphorylation (OXPHOS) to favor proliferation and invasion. The role of MSCs in tumor initiation, growth, and resistance to treatment is debated, but their ability to modify cancer cell metabolism and the metabolic environment suggests that MSCs are centrally poised to alter malignancy. In this review, we describe emerging evidence for adaptations in MSC bioenergetics that orchestrate developmental fate decisions and contribute to cancer progression. We discuss evidence and potential strategies for therapeutic targeting of MSC mitochondria in regenerative medicine and tissue repair. Lastly, we highlight recent progress in understanding the contribution of MSCs to metabolic reprogramming of malignancies and how these alterations can promote immunosuppression and chemoresistance. Better understanding the role of metabolic reprogramming by MSCs in tissue repair and cancer progression promises to broaden treatment options in regenerative medicine and clinical oncology.

Highlights

MSCs are multipotent non-hematopoietic cell precursors found in the bone marrow
Induced pluripotent stem cell derived-MSCs intrinsically express a high-level of Miro1 and possess higher efficiency of mitochondrial transfer relative to bone marrow MSCs (Zhang et al, 2016)
Further evidence for Connexin 43 (Cx43) in tunneling nanotubes (TNTs) development in lung injury comes from reports showing that Cx43 is upregulated in mouse lungs during asthma and that overexpression of Cx43 in therapeutically administered induced pluripotent stem cell derived (iPSC)-MSCs restores mitochondrial membrane potential, decreases excess mucus secretion, and reduces inflammatory cells and cytokines caused by lung injury (Yao et al, 2015, 2018)

Summary

Introduction

MSCs are multipotent non-hematopoietic cell precursors found in the bone marrow. Albeit highly heterogeneous, similar multipotent stromal cells are ubiquitous in many other tissues throughout the body, such as connective tissue and tumor stroma, and are referred to as MSCs in the literature (Ullah et al, 2015). Conclusive evidence for horizontal mitochondrial transfer between cells was published the following year, showing that human bone marrow MSCs could rescue aerobic respiration in cells depleted of mtDNA and mitochondria by ethidium bromide (Spees et al, 2006).

Results

Conclusion