Are there stem cells in blood? Can hormones optimize those stem cells?
POSTED ON 4/12/2011 IN Research BY Christopher Centeno
Episode 1 of Stem Cell Mythbusters: The site being reviewed by Mythbusters today just popped up and is run by a physician who has expertise in hormone prescription for general health and alternative medicine. This site says it uses blood derived Endothelial Progenitor Cells (EPCs) to treat cosmetic and orthopedic conditions. The site goes on to make the statement that the doctor will optimize your hormones which is "well known" to improve stem cell function, so balanced hormones optimize blood stem cells.
First, the doctor states that he is using autologous stem cells from blood. Are there stem cells in blood? The answer is yes, no, maybe. The most well known type of stem cell in blood is an Endothelial Progenitor Cell (EPC). EPCs help make, create and maintain blood vessels. While EPCs circulate in the peripheral blood, there are very few when compared to bone marrow. This is because EPCs are made and live primarily in the bone marrow and mobilize from there in response to some stress (see below). The doctor makes the opposite claim, that there are more EPCs in the peripheral blood than bone marrow, but I can't find a single paper that supports this claim.
What do we know about EPCs? We know that circulating EPC's decrease in patients with chronic disease like diabetes. In addition, the metabolic syndrome that I've blogged about in many posts, is also associated with EPCs that don't work as well to repair blood vessels. Other chronic diseases like erectile dysfunction also show marked decreases in circulating EPCs. There's even a inverse relationship between the number of circulating EPCs and hardening of the arteries (the more you have of these cells, the less artery disease is detected). It's also interesting to note that women have EPCs that work better than men. This may explain why women have less heart disease than men, as it's believed that these circulating EPCs help to reduce cardiac risk. In addition. exercise will increase the number of circulating EPCs, so it's thought that this could be one of the beneficial effects of exercise. The upshot? This myth is CONFIRMED on circulating stem cells called EPC's, but BUSTED on the idea that your blood contains more of these stem cells than your bone marrow, which is where they primarily live and reside.
The doctor states he's using autologous stem cells, but the literature makes clear he's really using platelet rich plasma. The site also claims that since the PRP is concentrating these stem cells, this will work better to help treat wrinkles and knee arthritis. So the next myth to be tested is PRP better at promoting EPC stem cells to repair tissues when compared to plain old whole blood (WB)? One recent study looked at the ability of PRP vs. WB to help other cells grow, which should be one hallmark of tissue repair (i.e. the more that PRP can help cells grow, the better it will be in helping healing). This study showed no great differences between PRP and WB. So on this front, the myth is likely BUSTED.
The site also makes clear that the doctor is using EPCs to treat cosmetic problems like wrinkles and arthritis. As evidence that EPCs will help your knee arthritis, the site describes a study by Mishra from 2006 where PRP was injected in a small group of patients to treat tennis elbow (not arthritis). To vet the claim, it's first helpful to identify what types of stem cells might be helpful for the problem being addressed. Stem cells come in many types, some of these are better at treating certain conditions than others. Since we're discussing orthopedic conditions being treated by this doctor (who usually prescribes hormones and treats wrinkles, not knees), what kind of stem cells might be helpful for arthritis? The two most published stem cell types to treat cartilage are mesenchymal stem cells (MSCs) and hematopoetic stem cells (HSCs). As of today, in the U.S. National Library of Medicine there are 1,610 research studies published on cartilage and MSCs (mostly derived from bone marrow) and 195 on HSCs (most of these are about MSCs and HSCs working together and used together). The clinic claims that the type of stem cells it's using are EPCs. A search under cartilage and EPCs today yields 125 articles, however almost all of these are about how EPCs may help MSCs. So the balance of the research performed to date showing that stem cells can repair cartilage has been with bone marrow derived MSCs and not peripheral blood derived EPCs. In fact, I was unable to find any studies were EPCs alone were used to repair cartilage. This is because the primary function of an EPC is to create and repair blood vessels. The clinic also claims that EPCs treat cosmetic problems like wrinkles. Is there anything published on the use of peripheral blood derived EPCs to treat cosmetic conditions? No, not a single paper. The references the clinic page provides are about peripheral blood EPC deficiencies in aging men or how certain hormones might impact these cells (like testosterone). So the myth that EPCs are well known to repair cartilage and wrinkles is BUSTED.
How do hormones impact stem cells? The clinic claims that getting hormones replaced or optimized if you're middle aged or elderly is well established to help stem cells and lists a few references. While getting your hormones optimized may be a great way to combat aging and disease, let's examine if it helps stem cells as claimed. First, the references refer to EPCs and the treatments discussed are for orthopedic and cosmetic conditions. There are no publications showing that EPCs work in orthopedic or cosmetic conditions, so why hormone optimization is needed for these stem cells is unclear. The references provided don't shed much light either. One study discusses how adding certain hormones may help optimize cardiovascular health (which is not being treated with the PRP/stem cells). Another study supplemented growth hormone which generally seemed to help EPC function, but orthopedic conditions or cosmetic treatments aren't discussed. One discussed erectile dysfunction-we don't need to go there. One discusses how testosterone can make your muscles bigger by impacting muscle satellite cells (not EPCs) which are cousins to MSCs, but different than the type found in bone marrow. Another discuses how your peripheral blood EPCs get less and less as you get older and have lower sex hormone levels. Lastly, one article discusses how a very specific nerve growth factor impacts neural progenitor cells (not EPCs)-so I have no idea why this reference is included. So how does the myth that optimizing hormones will optimize your peripheral blood EPCs stand up? BUSTED. While this could be the case, there really isn't any significant medical literature supporting this claim and none of the references quoted support the claim.
In summary, most of the statements thrown about on this site about hormones and stem cells and EPCs and arthritis are myths that are easily busted. While optimizing hormones may do great things for a lot of body systems, we simply don't know if they'll optimize your stem cells. We also don't have much research published that EPCs will treat your arthritis or wrinkles. While patients may feel better, look better, and could be healthier on hormone supplementation, making the claim that it's "well known" that optimizing hormones results in better stem cells isn't based on any existing science. In addition while PRP may work very well to treat wrinkles (not much published, but there are some interesting before and after pictures circulating around the internet), we don't know if that's because of the growth factors in the platelets or the EPCs in the blood or both. Getting stem cells to work is a complex interplay of a myriad of factors such as exact placement and likely control over the complex biochemical environment where cells are placed. Hormonal control over that environment likely only represents a small part of a much bigger picture.
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