Ashok Singh
Chicago, Illinois, United States

Stem cells represent a fascinating and promising frontier in modern medicine. As they multiply, stem cells are unique in their ability to differentiate themselves into cells with different properties. This ability is observable in the development of a complete body from a single, unique fertilized cell. After fertilization and multiplication into a critical mass, the cells start to differentiate into organs and tissues. Embryonic stem cells, or pluripotent stem cells, can transform themselves into any organ or tissue.

We still do not fully understand the biochemical signals that turn embryonic stem cells into various organs and tissues. Second order embryonic stem cells arise after the initial multiplication of a fertilized cell; they are organ specific but can become any cell type within that organ. While embryonic stem cells could be theoretically beneficial for healing or replacing a diseased organ, ethical, immunogenic, and tumor formation concerns also arise, since these cells are collected from early-stage human embryos.

A newer category, induced pluripotent stem cells (iPSCs), are mature adult cells that have been genetically reprogrammed to behave like embryonic stem cells. However, like embryonic stem cells, their practical use in growing specific organs or tissues is still limited until further technical breakthroughs allow for their use.

In addition to embryonic and iPSCs, there is a third kind of stem cell. Adult stem cells exist in the bone marrow and fat issue and have limited potency to form other cell types in the mature adult body. The bone marrow contains stem cells that form various kinds of white and red blood cells. These hematopoietic stem cells are continuously active in replacing aging blood cells throughout adult life. These types of stem cells are in clinical use to treat certain blood cancers or replace blood cells that have been damaged by disease or chemotherapy. This is known as a stem cell transplant, or bone marrow transplant.

Adult bone marrow and fat tissues also contain mesenchymal stem cells (MSCs), which can form connective tissue such as cartilage, fat, and bone in laboratory studies. Their discovery was soon followed by several landmark demonstrations that injection of autologous or allogeneic MSCs could repair ischemic heart tissue by reducing scar size and improving cardiac function. Initially, it was thought that the injected MSCs differentiated into new heart cells, but careful examination showed that MSCs worked primarily by releasing paracrine factors that reduce inflammation and stimulate the heart’s own regeneration mechanisms. This opened an additional avenue of treatment that uses not MSCs but the factors they produce in culture, called collectively the secretome.

The above studies caused great excitement, which led to the opening of hundreds of private clinics that promised cures for diabetes, arthritis, and multiple sclerosis, as well as kidney, lung, and liver diseases using autologous or allogeneic MSCs and/or their secretome. When the US Food and Drug Administration (FDA) formally announced that MSC treatment lacked scientific rigor and was an unproven technology, many of these clinics moved their operations to other countries. Anecdotally, these clinics and treatments have resulted in reports of both miraculous cures and allegations of fraud. It is difficult to assess the risks and benefits of these treatments because of a lack of standardization in sourcing MSCs, the number of cells injected, the viability of cells before injection, and the potency units of cell preparations among these clinics.

Stem cell therapy holds great promise for the future. However, more research is needed until treatments, or even cures, are safely and widely available.