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The latest from Calico. A bit technical.

Reprogramming of ordinary somatic cells into induced pluripotent stem cells (iPSCs) was initially thought to be a way to obtain all of the patient matched cells needed for tissue engineering or cell therapies. A great deal of work has gone towards realizing that goal over the past fifteen years or so; the research community isn’t there yet, but meaningful progress has taken place. Of late, another line of work has emerged, in that it might be possible to use partial reprogramming as a basis for therapy, delivering reprogramming factors into animals and humans in order to improve tissue function, without turning large numbers of somatic cells into iPSCs and thus risking cancer or loss of tissue structure and function.

Reprogramming triggers some of the same mechanisms of rejuvenation that operate in the developing embryo, removing epigenetic marks characteristic of aged tissues, and restoring youthful mitochondrial function. It cannot do much for forms of damage such as mutations to nuclear DNA or buildup of resilient metabolic waste, but the present feeling is there is nonetheless enough of a potential benefit to make it worth developing this approach to treatments for aging. Some groups have shown that partial reprogramming — via transient expression of reprogramming factors — can reverse functional losses in cells from aged tissues without making those cells lose their differentiated type. But this is a complicated business. Tissues are made up of many cell types, all of which can need subtly different approaches to safe reprogramming.

Today’s open access preprint is illustrative of the amount of work that lies ahead when it comes to the exploration of in vivo reprogramming. Different cell types behave quite differently, will require different recipes and approaches to reprogramming, different times of exposure, and so forth. It makes it very hard to envisage a near term therapy that operates much like present day gene therapies, meaning one vector and one cargo, as most tissues are comprised of many different cell types all mixed in together. On the other hand, the evidence to date, including that in the paper here, suggests that there are ways to create the desired rejuvenation of epigenetic patterns and mitochondrial function without the risk of somatic cells dedifferentiating into stem cells.