Andrés Caicedo, Ph.D.
Associate Professor
Universidad San Francisco de Quito, USFQ
School of Medicine, College of Health Sciences (COCSA)
Quito, Ecuador
Sebastián Peñaherrera, B.Eng. (Candidate)
Biotechnology Student
Universidad San Francisco de Quito, USFQ
Biotechnology, College of Biological and Environmental Sciences (COCIBA)
Quito, Ecuador
Kevin Zambrano, Ph.D. (Candidate)
Ph.D. and Physician Candidate
Universidad San Francisco de Quito, USFQ and Maastricht University
School of Medicine, College of Health Sciences (COCSA)
Quito, Ecuador
Maastricht University, the Netherlands
Romina Maya, M.D. (Candidate)
Physician Candidate
Universidad San Francisco de Quito, USFQ
School of Medicine, College of Health Sciences (COCSA)
Quito, Ecuador
Disclaimer/Conflict of interest statement.
Andrés Caicedo is the scientific founder and advisor of Dragon Biomed, an entrepreneurial initiative at the Universidad San Francisco de Quito (USFQ). He also serves as a scientific advisor in the Research and Development department of Luvigix. In these roles, he provides scientific guidance and expertise but does not participate in the decision-making processes or operational activities of either company.
Mitochondria are being transferred between MSCs (a). Mitochondria in red are able to pass through nanotubular structures and vesicles. This process is seen as part of the inspiration to develop the artificial transfer/transplant of mitochondria and its use as a 'Living Drug.' In (b), an image from Caicedo et al. (2015) shows the internalization of mitochondria in a recipient or acceptor cell, visualized through a confocal microscope and 3D representation (1).
What?
Mitochondria revolutionized the proto-eukaryotic cell, enabling the evolution and diversification of complex life forms on our planet. Within cells, mitochondria drive complex biological functions, from energy production and management to extending their supportive roles in cellular signaling, survival, and communication between cells in different organs (2,3). Intercellular communication triggers complex and concurrent nuclear and mitochondrial programming, enabling body cells to differentiate from glycolytic stem cells into aerobic somatic cells, thanks to mitochondria plasticity (4,5). Various signals serve as inputs to cells and reprogram mitochondrial functions, even leading to the production of reactive oxygen species and the induction of protective molecules crucial for cellular survival. Mitochondrial programming and state maintain a delicate balance between cellular differentiation, proliferation, maintenance, aging, or programmed cell death (6,7).
The organs in our bodies contain different types of mitochondria. Interestingly, mitochondria from one cell type can be transferred to others, such as from adipocytes to macrophages (8,9) . Furthermore, physiological changes influence this transfer, putting mitochondria into circulation to deliver adipocyte-derived mitochondria to heart tissue (8,9). The discovery of fully functional and intact mitochondria in the bloodstream, along with the ability of mesenchymal stem/stromal cells (MSCs) to transfer their mitochondria to damaged cells to repair their function, has supported the development of artificial mitochondrial transfer/transplant (AMT/T) as a possible therapeutic option to repair or rejuvenate cells whose function has been compromised by stress or time (10–13) .
Since the 1970s, with the earliest assays of AMT/T to our knowledge, scientific progress has deepened our understanding of the multifaceted roles of mitochondria in our physiology. This period also saw the emergence of mitochondrial augmentation therapy (MAT) as a promising therapeutic option for treating large-scale mitochondrial DNA deletion syndromes (SLSMDs) (13–17). As a result of these developments, the biological concept and scientific perception of mitochondria have evolved. They are no longer considered merely as "the powerhouse of the cell," but rather as a "Signaling Organelle," and more recently, as a "Living Drug” (13,17,18)
The use of AMT/T and mitochondria as a "Living Drug" parallels the success of MSCs in cell therapy, with massive investment but also significant questions to resolve, such as source, autologous vs. allogeneic transplantation, manufacturing, dosage, and route (13). Pharmaceutical companies like Astellas have made major investments in and acquisitions of AMT/T companies, such as Minovia in Israel and Mitobridge in the USA (19). New insights into the therapeutic effects of AMT/T are emerging from preclinical and clinical trials, covering a range of applications from neurological diseases to skin wound healing (13,20). This novel therapy is rapidly evolving, and the coming years will be exciting as scientific evidence from the application of this therapy could validate its potential to solve major problems, such as tissue stress and function loss due to aging (21).
Why?
AMT/T has been extensively studied and applied due to the simplicity of its principle: isolating functional mitochondria from a cell, platelet, vesicle or tissue and then using methods to incorporate them into other cells via administration, infusion, or aerosol delivery to damaged organs. However, understanding, studying, and validating the effects in the recipient cell and tissue is complex, requiring assurance of mitochondrial viability, uptake, possible integration into the cytoplasm, and ultimate fate (13,21–23). Nevertheless, therapeutic successes continue to emerge, leveraging the principle that damaged cells and tissues universally require mitochondria that can support or induce positive phenotypic changes.
In many respects, AMT/T mimics the therapeutic effects of MSCs, which transfer mitochondria to damaged cells and tissues via nanotubular structures and vesicles. Interestingly, since mitochondria are carried by microvesicles, evidence of the therapeutic effect of these subcellular products may also support the principle of AMT/T as a viable option for treating numerous diseases (24–26). It has been observed that AMT/T can reprogram the pro-inflammatory phenotype of Th17 cells, transforming them into immune-regulatory cells (27). This immune-regulatory effect offers many potential applications, including treating immune disorders and chronic inflammation.
Mitochondria as “Living Drugs” offer a wide range of potential therapies. The diversity of mitochondria in our body and cell sources is immense, leading to multiple effects when different mitochondria are transferred into recipient cells (13). Mitochondria contain their own mtDNA, with specific polymorphisms that could serve to reprogram recipient cell function and are even susceptible to future modifications through gene editing (13,28). Mitochondria can interact with the intracellular environment in various ways, from triggering mitophagy to increasing mitochondrial content and cellular respiration and function (17,18,29). Mitochondria can be obtained in large quantities by culturing donor cells or isolating them from platelets, allowing for growth and expansion (13,30). They can be transferred ex vivo into recipient cells, which can then be reintroduced into the patient or administered in situ or intravenously, ex-vivo modification (13,17). However, the effectiveness of the administration route still requires rigorous preclinical and clinical validation.
The simplicity of AMT/T, the diversity of mitochondrial sources, and the possibility of engineering and programming mitochondria for specific functions before administration make mitochondria a new and exciting form of acellular therapy.
Who?
To our knowledge, there are still no commercially available mitochondria as a “Living Drug” or for cosmetic applications. However, evidence that cells can uptake mitochondria from their surroundings or other cell types has spurred interest in leveraging this capability for therapeutic purposes. Both academia and industry have shown interest in enhancing cell therapies by incorporating purified mitochondria during cell processing and directly administering mitochondria to patients. This approach is starting to gain significant attention. Preclinical studies have shown that MAT can improve the engraftment of hematopoietic stem cells (HSCs). This has led to promising clinical trials in which patients with mtDNA deletion syndromes received healthy mitochondria, ultimately improving their quality of life (13,17,22,23) .
Other strategy involves administering purified mitochondria to treat conditions such as ischemia-reperfusion injury (31). Early clinical trials suggest that administering mitochondria has shown to be safe and might represent a new subcellular therapy to treat damaged tissue (13,31,32).
Early studies in pediatric patients using autologous mitochondria showed no short-term complications, and the presence of free mitochondria in the bloodstream suggests that the human body can accommodate these structures (11) (10,13,31). These findings support the potential safety of using autologous or heterologous mitochondria, although rigorous evaluation of safety and efficacy is essential as this therapeutic approach progresses (13).
How?
There is an immense therapeutic potential of mitochondria as “Living Drugs” with a growing industry's interest in harnessing their regenerative properties (13). Several challenges exist, including the need for GMP manufacturing of mitochondria, determining the best source for isolation, understanding optimal dosing and administration routes, scaling up production while maintaining quality, and identifying suitable diseases and patients for AMT/T (13). Accessibility, regulation, and responsiveness to public health needs are also important, and collaboration between regulatory agencies, academia, and industry is crucial to addressing these challenges common to cell and acellular or cell-free therapies. Mitochondria sourced from healthy tissues or cultured cells present scalability challenges; however, advancements in the development of clinical-grade protocols for MSC and CAR T therapies could be applied to the production of mitochondria and their therapeutic application. Emerging evidence has driven significant advancements in the field, with companies developing novel therapeutic approaches using both direct mitochondrial administration and ex vivo manipulation of host cells like HSCs (13,17).
Another key challenge is understanding the long-term effects of transferring isolated mitochondria to stem cells, as mtDNA appears to be capable of surviving in HSCs (17). Another challenge is maintaining their viability and properties after isolation, as mitochondria are fragile and susceptible to temperature and formula changes in the suspension medium.
Research is essential to fully understand the potential applications of mitochondria as "Living Drugs." Preclinical data will provide insights into optimal application methods, dosing, safety, scalability, and long-term preservation. Establishing a classification system to categorize mitochondria-based therapies could also facilitate their development and accessibility. By gathering robust evidence on the use of mitochondria as "Living Drugs," we can ensure their safe and effective use across a wide range of medical conditions.
Did you know that…
In the initial experiments with AMT/T, Mike Clark and Jerry Shay demonstrated in 1988 that isolating mitochondria from mammalian cells that were resistant to antibiotics like chloramphenicol could transfer this resistance to sensitive cells. Their work showed that the transferred mitochondria could transfer specific mtDNA and alter the recipient cell's phenotype to acquire resistance (16).
Cancer cells can potentially achieve "immortality" by acquiring mtDNA from their environment, leading to mitochondrial amplification and rejuvenation. This phenomenon has been observed in canine transmissible venereal tumors (CTVT), an infectious cancer cell line transmitted between dogs. It's estimated that this cancer originated around 10,000 years ago, making CTVT possibly the oldest cancer cell type still propagating today. This discovery suggests that there might be a way to rejuvenate aging cells by introducing younger mitochondria (33) .
Not only mitochondria is transferred in mammalian cells, researchers observed mitochondria moving from cell to cell through graft junctions in plants (34).
References
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