Should You Culture Expand Stem Cells for 10 Weeks?
POSTED ON 12/30/2017 IN Regenerative Medicine Education BY Christopher Centeno
One of the more interesting problems in the stem cell-treatment world is misaligned incentives. One of the places that issue tends to show up is in growing stem cells to bigger numbers, or a process called culture expansion. I've seen a number of outfits that charge by the number of cells used by the patient, and let me show you why this can create problems.
Culture expansion is a process by which stem cells are grown to bigger numbers. In this process, the cells are grown in flasks over several weeks while being fed. This isn't always necessary, but we've seen advantages in a few patients and diseases. The upside of culture expansion is that you get many more cells. The downside is that the following graphs apply to the properties of the cells versus time in culture:
Basically, the longer the cells are grown in culture, the less potent they become. In addition, the risk of a genetic aberration also increases. If this happens, it means that the cells that pick up these changes in DNA will be nonfunctional. While these abnormal cells will likely have no cancer-causing implications in patients with a normal immune system, they could potentially cause cancer in a patient who is immunocompromised.
Cell Quality vs Quantity and Selling by the Dozen
Since growing high-quality cells in greater numbers is a trade-off between the time in culture needed to grow more cells and the decrease in potency that occurs when you keep cells in culture for extended periods, it's best to grow cells for short periods. How short? Usually a max of 2–3 weeks. If you grow cells any longer, not only will the quality decline, but the risk of getting nonfunctional, genetically altered, and potentially dangerous cells increases. As an example of this effect, a clinical trial compared cells grown for 10–14 days with cells grown for just 2–3 weeks. The result? The cells grown longer didn't help patients with organ rejection nearly as much. In fact, twice the number of patients in the group where cells were grown twice as long died due to graft versus host disease (GVHD) compared to the group where cells were grown for shorter periods. This is, of course, where the problem begins for companies that grow cells and then sell them based on lots. For example, they may charge X to culture the cells and Y to pull each aliquot of 20 million cells out of the bank (in this case the cells are frozen down after they're grown). In that business model, the financial metrics get better if you grow more cells. This brings us to the illustration above. First, I've tried hard to "de-identify" the company that posted this on social media. Second, you'll notice the time the company says the cells are grown, which is 10 weeks! Yikes! At our licensed Grand Cayman site, we have never grown cells for more than 4 weeks and, frankly, growing them any longer than 3 weeks dramatically compromises cell quality. So while our licensed site could get many more cells by continuing to grow them longer, the cells would be basically nonfunctional or barely able to heal by the end of the process.
Genetic Aberrations and Karyotyping
One of the tests that should be done on cells that are culture expanded, but often isn't, is a genetic quality test of the cells. This is called karyotyping. This means that a qualified lab looks at the genetic structure of a sample of cells to ensure that it's normal. Why is this a big deal? This is a key metric of cell health. In addition, several studies have shown genetic abnormalities in stem cells cultured for longer periods. Hence, if your cells are grown in culture, insist on seeing a karyotype report. We've done this for years at our Grand Cayman licensed site, and it's stopped us from reinjecting a number of patients with poor-quality cells. If this is not offered where your cells are being grown in culture, then run. The upshot? Stem cell culture can be helpful by increasing the number of cells that can be injected. However, it's a delicate dance of quantity versus quality. Hence, I would recommend avoiding clinics that grow your cells for more than 3–4 weeks. In addition, make sure that you see a karyotype report for those cells to ensure that they're genetically normal!
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