A few recent studies involving heart attack victims have found that regenerative potential exists within the heart itself. In the past, heart failure as a result of heart attack has been inevitable and unavoidable. One doctor said that it's only a matter of time before the heart fails. However, that could be changing within our lifetime. Stem cells derived from the heart itself have the potential to regenerate heart muscle and blood vessel tissue, and reverse the damage of a heart attack.
So far, the studies have shown that after administration of the stem cells, heart function is gradually restored above the "Left Ventricle Ejection Fraction" of 40% that is indicative of heart failure. Scar tissue retreats in addition to new tissue formation after the treatment. Even though further studies are necessary before the treatment becomes standard, several studies thus far paint a promising picture for our ever-growing population of heart attack and heart disease patients.
In addition to the exciting results of the studies, I found it very interesting that treatments including a mixture of stem cells and other types of cells extracted from a patient's heart have been more effective than nearly pure stem cell administrations. Similarly, some data suggests that treatment with bone marrow-derived stem cells yields the greatest results when administered within a few days of a heart attack, rather than a few weeks or months post-heart attack. Though no explanation is offered in the article, perhaps this is because the heart would be at its peak of trying to repair damage from the heart attack shortly after, and the stem cells boost this repair even further. That idea brings up further questions, though, as to why the heart doesn't automatically repair itself before the heart attack even happens then, if these cells already exist in the heart. Is it because the number of these cells is too low, and they must be multiplied in the lab to be effective? Or because they are not active in the heart without some sort of action to activate them?
All of this data seems exciting and likely to become a promising treatment, but I have concerns about the social impact of the treatment. In many ways, our society is working to eat healthier and be more active to reduce the current obesity epidemic and ultimately decrease the incidence of heart conditions. If this treatment becomes standard, will it deter people from the current healthy movement since they have the option to reverse the damage they could do by eating less healthfully and not maintaining an active lifestyle? If the repercussions of a less healthy lifestyle are potentially removed, perhaps people will not put as much effort into taking care of their bodies. Or is this worry an overreaction to something that could greatly benefit a society that isn't turning away from unhealthy lifestyles quickly enough? Either way, the physiology behind the heart and its newly-discovered repair mechanisms is interesting and a step in the right direction of understanding the intricacies of the human body.
http://www.cnn.com/2011/11/14/health/stem-cells-heart-damage-reverse/index.html?hpt=he_c2
I found an article here that addresses the reason why treatment will have the greatest yield when stem cells are injected soon after the heart attack. After a heart attack, there is swelling around the area that was affected/damaged. The earlier the stem cells are injected, the more likely they will be attracted to the multitude of chemicals and granules released by those damaged cells. Essentially, the damaged cells act as "a homing device for the stem cells to respond to, and then repair." If the time after a heart attack is increased the swelling and chemical attractants will diminish, and because stem cells are injected intravenously, they will not be as inclined to repair the heart.
ReplyDeletehttp://www.katu.com/news/medicalalert/86225792.html
Also, you asked why these cells dont repair the heart before the heart attack happens. This is because a heart attack occurs as a result of a coronary artery blockage, resulting in oxygen shortage to the heart cells. Stem cells are not able to remove artery blockages, which would be the only repair needed prior to a heart attack.
Your final argument is good, and can be made for many new and upcoming treatments that could potentially encourage a less healthy lifestyle. However, in this case, this treatment will only be viable ASSUMING the patient survives the heart attack. Living a healthy lifestyle (with both diet and exercise) are known to dramatically decrease the risk of a heart attack, which is by far the leading cause of death here in the US.
The wonderful thing about using a patients own cells to assist in regeneration is the nearly zero risk of rejection of the tissues or cells. In fact as previously stated, the immune systems activation assists in guiding the cells and activating them....most of the time.
ReplyDeleteI decided to look a little closer at the immune system and its interaction with stem cell regeneration. An interesting article I came across while digging was "Recipient's immune system governs stem cell regeneration".
http://www.sciencedaily.com/releases/2011/11/111120134749.htm
It was published November of this year in Nature Medicine. The research (although on mice) was specifically looking at the effects of different T cells (A lymphocyte that plays a key role in cell mediated immunity). Usually they play a role in protecting the body from infection, but they can also block healthy cellular regeneration. T cells in the study produced cytokines INF-gamma and TNF-alpha in an inflammatory response that attacked and killed many of the stem cells.
In the experiment the researchers injected T regulatory cells that produced lower cytokine levels and increased the rate of regeneration over the normal inflammatory response. They found a similar benefit when using aspirin (COX inflammatory pathway inhibitor). So it appears that there are many levels and difference in the immune response and its effect on tissue regeneration.
I found an interesting article on the actual induction of stem cells, in this case pluripotent stem cells. In the paper they show that cellular microRNAs (miRNAs) regulate iPSC generation. Knock-down of key microRNA pathway proteins resulted in significant decreases in reprogramming efficiency. First, they ran an assay to determine which miRNAs were upregulated in the early stages of reprogramming, or induction into a pluripotent state. They then followed with several dosage-dependent experiments of the miRNAs and reprogramming efficiency. In short, they determined that the particular family of miRNAs directly targeted Tgfbr2 and p21 and that miRNAs function in the reprogramming process and that iPSC induction efficiency can be greatly enhanced by modulating miRNA levels in cells.
ReplyDeleteReference:
Zhonghan, Li, and Yang Chao-Shun. "Small RNA-mediated Regulation of IPS Cell Generation." The EMBO Journal 30 (2011): 823-34. Web. 2 Dec. 2011.
The study that Ashley described is very interesting and important for the future treatment of many individuals. For the first time, stem cells were injected into the hearts of humans who had previously encountered heart damage (Salzberg, 2011). The patients’ conditions improved and the treatment shows great promise for the future of stem cell treatment—by repairing or replacing damaged organs. The studied led by Robert Bolli grew stem cells from the patients’ own hearts (Salzberg, 2011).
ReplyDeleteI think Ashley makes a great point in regards to society eventually relying on these kinds of procedures instead of fixing them themselves through means of exercise and eating healthier. Having this type of treatment available is very beneficial and allows for more research in stem cell treatment—for example using the same technique to replace damaged livers, kidneys, spinal cords, cartilage, and other human tissues (Salzberg, 2011). I hope that this new treatment will not discourage people from the current healthy movement. Physicians are still going to highly encourage exercise and healthy diet—but it still stands on the fact that the patients want to commit to the hard work. Heart disease is the leading cause of death in the United States, thus the research involved in stem cell repair mechanisms offers hope for future successful treatments of many patients (Salzberg, 2011). Only a few patients have been injected with the stem cells in the heart—but all showed improvement. Importantly, this research shows great promise and will be beneficial for the future of stem cell treatments.
Salzberg, Steven. Stem cells show promise for repairing damaged hearts. Pharma & Healthcare, December 4, 2011. http://www.forbes.com/sites/stevensalzberg/2011/12/04/stem-cells-show-promise-for-repairing-damaged-hearts/.