An emerging area of research is the evolutionarily conserved transfer of mitochondria between cells. Yet researchers have lacked unique and universally accepted terms and practices to describe such transfers. Absent an agreed nomenclature and standard practices, different researchers may use different methods and terminology to describe the same event, or they may employ the same term that actually describe two different processes.

“Over the past few years, we have come to understand that mitochondria can be transferred from one cell to another, and that isolated mitochondria can be transplanted like an organ transplant,” said Keshav K. Singh, Ph.D., professor in the University of Alabama at Birmingham Department of Genetics. “Though the origins of mitochondria transfer are unclear, it has been observed in evolutionarily diverse eukaryotes, including yeast, mollusks, fish and rodents, as well as human cells. We are just beginning to understand how alterations in this process contribute to disease pathogenesis and how to harness mitochondria transfer and transplantation biology to develop new therapies.”

In 2024, Singh and Jonathan Brestoff, M.D., Ph.D., Washington University School of Medicine, Saint Louis, Missouri, set up an international consortium on mitochondria transfer and transplantation and led an international team of 31 researchers to develop consensus and recommendations about how to advance the field by providing common terminology and characterizations for the transfer or transplantation of mitochondria. Their consensus paper, “Recommendations for mitochondria transfer and transplantation nomenclature and characterization,” is published in the journal Nature Metabolism.

The paper begins with a brief history of the field — some foundational early discoveries, recent studies of mitochondrial transfer and development of therapeutic approaches, including cell engineering and clinical trials for children requiring extracorporeal membrane oxygenation.

The paper defines types of mitochondria transfer and mitochondria transplantation, and when both the donor and acceptor cell types are established in vivo, that defines a mitochondria transfer axis. The paper reviews methods to define mitochondria transfer, including mitochondria reporter proteins and dyes, methods to enforce transfer, and discussion of the fate of mitochondria after cell entry. Mechanism-based nomenclature is roughly grouped into contact-dependent mitochondria transfer, where the donor cell and recipient cell touch each other, and contact-independent mitochondria transfer.

The recommendations also review therapeutic approaches of mitochondria transplantation, including the definition of transplants; the types, durability, degree of engraftment and heterogeneity of transplants; cell engineering using extracellular mitochondria; and drugs that affect mitochondria transfer. Extracellular mitochondria are common in humans — for example there are about 3 billion to 12 billion extracellular mitochondria in a unit of blood platelets, a blood product that is routinely and safely transfused to patients intravenously.

The paper concludes that “the goal of this proposed nomenclature is to reduce the confusion that can be caused by the introduction of different names for similar processes or extracellular mitochondria subsets as this field has evolved. We recognize that mitochondria transfer and transplantation are very active areas of research and that it is possible that new findings and insights may necessitate updates to the proposed nomenclature.”

Singh has a long-standing interest in mitochondria. He was founding editor-in-chief of the journal Mitochondrion and the founder of the Society for Mitochondria Research and Medicine. In 2007 and 2009, his laboratory showed that isolated mouse mitochondria can be transferred to human cells by co-incubation, providing a proof of principle for transfer of mitochondria by diffusion, and that xeno-transplanted platelet mitochondria from an African American woman who suffered aggressive breast cancer at young age was able to recapitulate aggressiveness of breast cancer in mice. At that time, these findings were not appreciated by the field, Singh says.

The increase in physical activity was mainly seen in those doing semi-routine occupations such as bus driving or hairdressing, and routine occupations such as cleaning or waiting, or technical jobs. There was little change seen among people entering managerial or professional occupations.

The largest drop in levels of physical activity was seen among people who work from home — though their sleep levels did not change when they started work.

Young adulthood — ages 16 to 30 years — is an important time in terms of health. Although we are typically at our peak physical health, it is also a time when many risk factors for long term diseases such as heart disease, type 2 diabetes and cancer begin to develop.

Health guidelines recommend young adults get between seven and nine hours of sleep a night, engage in 150 minutes or more of moderate physical activity per week, and consume at least five portions of fruit and vegetables per day.

Young adulthood is also the time when most people start work, which changes their daily routines and activities, resources such as time and money, and social and physical environments — all of which affect health behaviours and health in later life.

To quantify the impact that starting work has on health-related behaviours, a team led by researchers at the Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge examined repeated data taken over time from more than 3,000 participants in the UK Household Longitudinal Study. All the participants were aged 16-30 years and started work for the first time between 2015 and 2023.

The results are published today in the International Journal of Behavioral Nutrition and Physical Activity.

Dr Eleanor Winpenny, who was based at the University of Cambridge when she carried out the work, but is now at Imperial College London, said: “We know about physical activity and sleep patterns among young people while they’re at school, but very little about what happens when they start work. Given the impact that work can have on our lives — and the lasting impacts this can have on our health — it’s important to try and understand what happens at this transition.”

The analysis showed that when people started work, their physical activity increased by an amount equivalent to around 28 min of moderate activity (such as cycling) per day on average — but then decreased each year after starting work by around 7 min per day.

The biggest increase was among males — up by an equivalent of around 45 min of moderate activity per day compared to an increase of around 16 min for females. People who did not have a university degree also showed a greater increase in physical activity compared to those with a university degree — equivalent to around a 42 min increase of moderate physical activity per day compared to 15 min per day.

Working from home, however, appeared to be associated with an initial decrease in physical activity, equivalent to around 32 min of moderate activity per day.

When young adults started work, the amount of time they slept per night dropped immediately by almost 10 minutes and remained stable at this level over time; however, people without a degree showed a continuing decrease of about 3 minutes of sleep per night each year after starting work, while those with a degree slowly increased back to their pre-work sleep levels.

There was little change in the amount of fruit and vegetables consumed after starting work.

Alena Oxenham, from the MRC Epidemiology Unit, said: “Beginning work can have a profound impact on our lifestyles and on behaviours that might make a difference to our health, if not immediately then later in life.

“Although we found that people tend to do more physical activity when they begin work, which is good news, these are averages, and some people — particularly those who work from home and, to a lesser degree, those with office-based jobs — may do less.

“If we want to stay healthy throughout our lives, we need to remember that keeping active is an important way of helping us achieve this goal. Those working at home might want to consider incorporating physical activity into their day, for example by going for a walk before or after work, or during a lunch break.”

Dr Winpenny added: “Workplaces provide an opportunity to create environments and cultures that support healthier diets, more physical activity and better sleep for young adults. This could result in healthier employees and fewer sick days in the immediate term, but also have long term benefits, helping prevent health issues in later life.”