Ken wrote: ↑Mon Aug 23, 2021 3:48 pm
Soloist wrote: ↑Mon Aug 23, 2021 2:02 pm
Care to present some research articles on the limitless replication rate of these stem cells that are used for vaccines?
You are the one making the argument about limited replication of stem cells. I'm just asking if
you have any idea how fast the stem cells are replicating (dividing) within a culture of HEK-293 or MRC-5 cells?
I'm not asking how many time the culture itself is duplicated, which is what is referred to as "passages." I'm asking how frequently the cells within a single culture are dividing. Or how many times they have divided since being isolated 50+ years ago.
No I don't know the actual replication rate. Studies I've seen suggest the rate takes longer then 24 hours after 30 replications. This passages that you are referring to is something else. They have a finite replication (cellular division) of the Hayflick limit. A gram of cells is roughly 1billion cells. The argument is that it is immortal is not supported by science.
Looks like about 33 hours for a doubling of population of cells.
https://www.sigmaaldrich.com/deepweb/as ... 5/r022.pdf
What is passaging
https://www.allevi3d.com/passaging-cells-protocol/ it is not the number of replications.
and as referenced below, each time he did a subculture that is considered passaging.
In his 1964 experiment, Hayflick further examined the mechanisms that could cause the fetal cells to stop dividing. He created subcultures from fetal lung cell lines and adult lung tissue and named the cultures after the Wistar Institute and by number order. Hayflick cultured fetal lung tissues which he had received from male and female fetuses, and which he named the male derived cells WI-26 and the female derived cells WI-38 and WI-44. He extracted the fetal lung tissue from fetuses aborted at about three months gestation, he generated the adult strains from lung tissue of dead adults, and froze all of the tissues in a container with liquid nitrogen to preserve them. Each subculture split in a two-to-one ratio, which means that each cell in the samples divided once, producing two more cells.
Hayflick's results indicated that in a two-to-one split ratio, the average number of times a fetal cell could divide was between forty to sixty times. In adult cells, the average number of times a cell would multiply was twenty. That data indicated that in adult cells, numerous cell duplications had already occurred, as their number of duplications in the lab setting were less in comparison to the number of cell divisions in the fetal cell strains. In the experiment, Hayflick called the phase when the cell ceases to divide phase III, with phase I and II being periods in which a cell rapidly proliferates.
Hayflick investigated whether fifty was the average number of divisions for every fetal cell within the same population, or if it was just a randomly occurring number. To test his hypothesis, Hayflick randomly selected and cloned three samples of the fetal cell line, WI-38, and he recorded when each population stopped dividing. The resulting range for each clone was from fifty to fifty-four divisions. That data lead Hayflick to hold that something in cells limited the amount of times a cell can double. From the results, Hayflick concluded that cellular aging is based on the amount of times a cell doubles.
https://blog.genofab.com/hek293-cell-line
This continuity and reproducibility has made cell lines integral to many endeavors and is in sharp contrast to the usual behavior of mammalian cells, namely a growth arrest after a set number of divisions imposed by the Hayflick limit. Methods to generate immortalized cell lines differ and include starting from already immortalized cancer cells (such as HeLa cells) as well as introducing viral or mammalian genes such as telomerase to effect an indefinite proliferation. As the method of immortalization influences the resulting cell line, the origin of a widely used cell line such as HEK293 can be illuminating for working with it.
So... to recap, HEK-293 cells are not specifically stem cells. Some strains are immortal due to mutation with SV-40 virus or cancer.
https://pubmed.ncbi.nlm.nih.gov/12463478/
This link explains that stem cells also are subject to the Hayflick limit however, it varies much more as it differentiates.