Cell proliferation limit and senescence of embryonic stem cells and fibroblasts?

Question

I am trying to understand the importance of proliferation limits and cell senescence. In particular, I would like to compare the proliferation limit of Embryonic Stem cells (ES) and fibroblasts (which would be trans-differentiated) and describe how this difference plays a role when thinking about engineering organs, for example a heart transplant.How do ES cells and fibroblasts compare with regards to the Hayflick limit?

Answer 1

So, in the case of the Hayflick limit, a fibroblast normally can only replicate around 50 times. The Hayflick limit is often talked about when thinking about the loss of telomere length during cellular replication. There was initially the idea that cells could replicate infinitely due to an experiment on chick heart tissue, but it could never be reproduced. So, the hayflick limit can actually be lengthened when cells are presented with telomerase, the enzyme that replicated the telomeres. Having a supply of the enzyme can help the fibroblasts escape cell death.

Stem cells are actually similar in terms of their hayflick limit. They tend to only replicate around 70 times. However, they most stem cells don't replicate as often. I think they only really replicate when they need to create another stem cell which can then allow their other cells to start differentiating, as stem cells tend to be less differentiated. Our stem cells don't seem to have the endless replication activity of certain organisms. They also tend to respond to telomerase when extending their limit.