Aging is a natural biological process that affects every cell in our bodies, resulting in various age-related pathologies, and finally the death of each multicellular organism. It is a complicated and multifactorial process, in which different mechanisms participate, including mitochondrial dysfunction, lysosome processing, endoplasmic reticulum stress, genomic instability, telomere attrition, epigenetic alterations, stem cell exhaustion, and altered intercellular communication.
Regardless of its origin, cellular aging is consequently reflected at the level of organs and system dysfunction. In mammals, this process is particularly important in the immune system. This process called immunosenescence leads to detrimental effects on the innate and adaptive immune responses, leading to chronic inflammation, poor responses to infections and vaccination, and increases the risk of metabolic conditions.
In a study published in the journal Rejuvenation Research, a team of scientists evaluated the use of autologous hematopoietic stem cell transplantation (HSCT) in slowing and reversing the aging process.
Stem Cells Role in the Immune System
HSCT has been used for the treatment of hematological and other malignancies, hereditary diseases, and some autoimmune diseases for almost 45 years. For autologous transplantation, HSCs are collected in a disease-free period and cryopreserved in liquid nitrogen where they retain complete engraftment potential after an extended period of cryostorage, remaining viable for up to 100 or more years.
The optimal age for collecting autologous HSCs is during an individual’s healthy period of life, preferably between 20 and 40 years of age.
Based on the experience related to HSCT in humans and animals, various defects of the immune system could be alleviated by their transplantation. It could mitigate a long list of age-related defects of immunity.
In the innate immune system, it could mitigate the impaired cytotoxic capacity of natural killer (NK) cells, the decreased production of cytokines by activated NK cells, impaired migration and antigen presentation of dendritic cells, decrease the chronic activation of proinflammatory cytokines, and by doing so decrease the morbidity and mortality associated with infections.
They could also contribute to the mitigation of impairments in the adaptive immunity, in both B cells and T cells, by increasing the production of long-term immunoglobulin-producing B lymphocytes and the immunoglobulin diversity and affinity, increasing the response to vaccination, and the T cell pool.
In a study by Aspinall and colleagues, researchers transplanted young naive T cells into old recipients, which led to their successful incorporation into the peripheral T cell pool. Transfusion of autologous blood-derived leukocytes from an individual taken at an earlier age, therefore, seems to be a valid replacement strategy for rejuvenating and restoring certain immune functions.
In 2011, Shen et al. conducted a study on age-related osteoporosis and found that transplanting young mesenchymal stem cells (MSCs) into old mice not only significantly slowed the loss of bone density but also prolonged their life span by 16.3%.
Kim et al. recently reported that young stem cells, when intravenously transplanted to old rats extended their life span by up to 31.3% and even improved their cognitive functions.
Multiple studies have confirmed the feasibility of this procedure, which has not only improved different age-related health conditions but had also extended their longevity. If translated to human medicine, stem cells could prevent or mitigate age-related immune defects and extend the healthy life span.
Rozman, P. (2019). How Could we Slow or Reverse the Human Aging Process and Extend the Healthy Life Span with Heterochronous Autologous Hematopoietic Stem Cell Transplantation. Rejuvenation Research. doi:10.1089/rej.2018.2164