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I was directed to ask these questions here. Perhaps someone can help. >They can be modified and multiplied indefinitely in the culture dish What conditions ex

I was directed to ask these questions here. Perhaps someone can help. >They can be modified and multiplied indefinitely in the culture dish What conditions exist within a culture that allow stem cells (or other cells) to replicate without regard for the Hayflick limit? I was totally unaware that we had extended it (not defeated it) in any life more complex than a worm. And on the topic of the Hayflick limit… >What is special about the reprogrammed cells of the Heidelberg researchers is that they are a homogeneous cell type that resembles a stage of neural stem cells that occurs during the embryonic development of the nervous system. Are they saying that the stem cells can be reprogrammed into cells that more greatly resemble younger human cells, or that they're actually being made into scientifically-defined younger cells? How is that even possible? I was under the impression that all cloned cells retained their telomerase length. As such, any clone (or cloned tissue) made from them isn't going to be any more "youthful" than the original. If the case is that an entirely cloned organism is made, it will only a life expectancy as long as the original has LEFT to live–since the telomere isn't restored to its original length. I guess they wouldn't call it a "regenerative" therapy if they hadn't fixed the telomere length problem in the cloned cells, but… if they have, isn't that sort of the single biggest fucking deal in human history? Isn't this the first time that human cells have been genuinely restored to youth, and could therefore be reapplied into a person to extend his life? And, thereafter, be the gateway into figuring out how to simply restore the DNA of cells in the body without excision and replacement? Thanks for any answers!

JackStriker 8y ago
Oh dear, I may have double posted. Sorry if I did.
Misker 8y ago
I wish I had an answer for you, but I don't. Just dropping in to say that KS for asking those questions, as I didn't even know of the Hayflick limit before. I now have more questions.
fanzhang 8y ago
Many types of human-cells don't abide by the classic Hayflick limit, including HeLa cells, cancer cells, and gametes. This brings up the point: if the cells can indeed divide indefinitely, which even stem cells cannot, then aren't these effectively cancer cells / made cancerified? Perhaps this was done on purpose independently to make the cell culture easier to work with, but that should have been mentioned.
- thomasfedb 8y ago
  They might share some properties with cancer cells, but probably not all the key characteristics. For example, one key feature of a cancer cell is that it ignores signals that would causes normal cells to stop growing or apoptose (die).
maxander 8y ago
My understanding of it is (although I'm not remotely an expert on cell culture) that stem cells can in general be made to divide in culture "indefinitely"; the Hayflick limit applies only to (non-stem) somatic cells. Stem cells use telomerase to maintain their telomeres, similar to how germ cells use telomerase to reset themselves to a "newborn" state. Stem cells can progress from "universal progenitors," the stuff of the featureless blastocyst, to embryonic stem cells of various forms, to adult cells (both stem and somatic); this process has to do with changes in gene activation and cell morphology, not with telomeres. When the article notes that these cells can be "multiplied indefinitely," the point is that researchers can prevent them from differentiating into more-mature forms of cell when they divide.

JackStriker 8y ago

Oh dear, I may have double posted. Sorry if I did.

Misker 8y ago

I wish I had an answer for you, but I don't. Just dropping in to say that KS for asking those questions, as I didn't even know of the Hayflick limit before. I now have more questions.

fanzhang 8y ago

Many types of human-cells don't abide by the classic Hayflick limit, including HeLa cells, cancer cells, and gametes. This brings up the point: if the cells can indeed divide indefinitely, which even stem cells cannot, then aren't these effectively cancer cells / made cancerified? Perhaps this was done on purpose independently to make the cell culture easier to work with, but that should have been mentioned.

thomasfedb 8y ago
They might share some properties with cancer cells, but probably not all the key characteristics. For example, one key feature of a cancer cell is that it ignores signals that would causes normal cells to stop growing or apoptose (die).

maxander 8y ago

My understanding of it is (although I'm not remotely an expert on cell culture) that stem cells can in general be made to divide in culture "indefinitely"; the Hayflick limit applies only to (non-stem) somatic cells. Stem cells use telomerase to maintain their telomeres, similar to how germ cells use telomerase to reset themselves to a "newborn" state. Stem cells can progress from "universal progenitors," the stuff of the featureless blastocyst, to embryonic stem cells of various forms, to adult cells (both stem and somatic); this process has to do with changes in gene activation and cell morphology, not with telomeres. When the article notes that these cells can be "multiplied indefinitely," the point is that researchers can prevent them from differentiating into more-mature forms of cell when they divide.