As stem cell technology continues to evolve, the applications for stem cell treatment have expanded dramatically. One of the most popular uses of stem cells has been using it as an alternative therapy for knee replacement surgery. Studies have shown that people who undergo stem cell treatment experience a much quicker recovery than surgical patients with far fewer complications. And, perhaps most interestingly, stem cell treatment tends to last longer than surgery, in terms of relieving knee pain.
However, recent research results suggest that stem cells may play another important role in treating past injuries, such as knee problems.
In general, we think of memories only residing in the human brain. However, a breakthrough study suggests that stem cells may retain memories, and particularly memories of previous injuries. This may be true for stem cells throughout the body, but it is particularly true of stem cells located in a person’s gut, airwaves, and skin. These stored memories may help the body respond in a more effective way to new injuries; in other words, the body remembers what it did well in the past and what still may need improvement.
For years, scientists believed that most cells did not retain memories. And this belief was particularly strong about stem cells, because stem cells are needed for replication purposes throughout the body. Scientists had hypothesized that replication could only effectively happen if these cells did not retain memories.
But, a study released in August dramatically changed this thought process.
What the Study Said
The study that was released in August of 2018 was the result of work from stem cell innovators at the Massachusetts Institute of Technology (MIT) and Brigham and Women’s Hospital. This study was primarily focused on exploring inflammation, and particularly inflammation resulting airborne allergens. Allergies affect millions of people each year, and result in a dramatic loss of manpower hours (and huge economic costs).
This particular study examined the cells from inside the nose of patients with chronic sinusitis, and then compared these cells with the cells of people not affected by sinusitis. These cells were then sequenced and the study revealed that for chronic sinusitis sufferers, many of the active genes in the cells were genes linked to allergic inflammation. These genes have also been linked to Interleukin 4 (IL-4) and Interleukin 13 (IL-13), which are well-known immune mediators.
These results seemed to suggest that stem cells directly interacted and communicated with the person’s immune system.
Taking It A Step Further
Based on this, the scientists decided to take their experiment a step further. In this next stage, they cultured cells from the airwaves of patients who have been impacted by allergy symptoms. Even though the patients were no longer directly exposed to the airborne allergens, the biopsied cells still showed a significant amount of inflammation. Due to these results, scientists hypothesized that stem cells that had been triggered or inflamed in early stages communicated this triggering to future generations of stem cells, which then responded in a triggered manner (even though the source of the trigger was no longer there).
The Impact of Cellular Memory
It is important to note that these memories can have both positive or negative impacts on a person and their overall health. For example, in the case of the allergy sufferer, this may be a negative. Cells and tissues will be inflamed even though no trigger is present. Put simply, the body is over-reacting to something that is not problematic. However, the same response can also be positive. For example, stem cells may retain memories of how they effectively fought an infection. This may mean that the next response to an infection will be even more effective.
The first case would be considered a maladaptive response, whereas the second case would be considered adaptive.
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And What This Tells Us About the Future
If scientists can determine what cells activate and what makes some responses maladaptive (and others adaptive), then scientists can potentially figure out ways to channel the positive responses and mitigate the negative ones. But, this will require additional research and thought. One initial thought is that if interleukin 4 (IL-4) and interleukin 13 (IL-13) are turned on in these hyper-immune system responses then a therapeutic intervention that blocks IL-4 and IL-13 may calm the immune system and lead to better outcomes for the impacted patients.
Cells Don’t Exist In A Vacuum
Other scientists argue that the most important conclusion from this research is that cells do not exist in a vacuum. Instead, cells interact with the environment in which they are found, and feedback loops exist. Cells react to what stimulates them and they remember these prior stimulations (both for good and bad). The question remains: What can scientists do to channel these findings into improved therapeutic outcomes for patients?
Keep In Mind Previous Examples of Positive Adaptive Behavior
One interesting result emerged roughly 18 months ago. In this study, scientists discovered that if the skin of mice was wounded and was allowed to heal that future injuries to the same area would heal much faster (compared with previously intact skin). It appeared that the mice’s stem cells in this area remembered the previous injury and recalled how to effectively heal these injuries. The rate of healing was dramatically different, up to 2.5 times faster. And, interestingly, the stem cell memory in mice seemed to last for up to 6 months. It is not clear if this memory term will be longer in humans compared with mice.
This would clearly be an example of a positive adaptive behavior. But, scientists are quick to point out that there is also an associated downside with this. So, the question becomes: How do scientists maximize the positives while making sure that cells do not repeat prior bad behaviors? Unfortunately, at the moment, there is not necessarily an easy answer to this question … This may take years of additional research!
But, It’s Still A Mystery
This is not the only thing that is unknown. Much of the science of these memories still remains a mystery. Scientists still do not know the mechanisms by which cells retain these memories. Preliminary suppositions suggest that during the initial inflammation process the DNA is modified as genes have been switched on. It is important to remember that these cells are not just switched on or modified by these retained memories, they are also able to communicate with the environment that surrounds them and other cells, creating a matrix of key feedback loops.