At the RIKEN Center for Development Biology some researchers have finally decrypted a long pending mystery of why both induced pluripotent stem (iPS) and human embryonic stem (ES) cells are programmed to apoptosis (cell death) when cultured in isolation. The unveiling of new hints of cell therapy techniques is offering hopes to treat debilitating degenerative diseases.
There is a particular cell therapy technique known as cell dissociation. It is a method for isolating cells. A procedure used in sub-cloning, but it does stand as an obstacle for effective stem cell research because it tends to pose negative effects on human embryonic stem cells. For human embryonic stem cells, 99 percent of its culture is eradicated by a widespread apoptotic reaction, but this effect does not apply for mouse embryonic stem cells. These researchers had recently discovered that the cell death could be decreased by 30 percent through the use of a protein called Rho-associated kinase (ROCK). Unfortunately, mysterious questions remain unsolved concerning how the mechanism functions.
The researchers used what is so called live-cell imaging to find answer to these unsolved questions. The technique was used to understand the prime phases of dissociation in mouse and human embryonic stem cells. The findings were radically different: The mouse embryonic stem cell did hardly change position while the human embryonic stem cells skittered about in a sort of “death dance”; instantly realising finger-shaped bulges, called blebs, which developed into the cells burst and died. The study examined the development of these blebbings, it was the first time that this type blebbings were examined to the extent of the source of hyper-activation of myosin, which is an enzyme in charge of cell motility.
The researchers were expecting to shown that myosin hyper-activation, mediated through the launch of ROCK kinase, was responsible for the cell death (apoptosis) in dissociated human embryonic stem cells, instead of the blebbing. The study did thus reveal other implication related to cell motility, through the inhibition of Rac, which joins with ROCK to activate and support the myosin hyper-activation causing apoptosis.
This study was published in the Journal Stem Cell, and it was the first time that a fully clear explanation of the reason how dissociation-induced apoptosis occurs in human embryonic stem cells. The study will also support the emergence of more effective and safer cellular therapies associated with debilitating degenerative diseases.
Source: Science Daily and E-science News
Mon, Aug 9, 2010
Anti Aging, Stem cells