Berkeley Campus:Image via Wikipedia
When muscles are damaged in young animals they are repaired by stem (satellite) cells. However, older animals are not efficiently repaired, despite having enough stem cells. In previous papers (here and here) this group found that if the blood circulation of young animals were shared (parabiotic pairing) with older animals the old animals had better muscle (and liver) repair (after damage) compared to older animals with their normal blood supply (or paired with older animals). This line of research suggest that there is an active component in the blood of older animals inhibiting the stem cells from repairing the damaged muscle. In the 2nd prior paper they found that young stem cells ‘age’ if exposed to the blood or environment of older animals.
In the current Nature paper the group found two key signals that are involved in the fine balance between stem cell aging and retained ‘youth’: Notch and TGF-beta. Notch maintains the stem cell ability, while TGF-beta inhibits these cells. As we age Notch decreases and TGF-beta increases – thereby inhibiting stem cells ability. When the group altered the balance of these pathways (by inhibiting the TGF-beta/pSmad3 pathway via RNA interference) in older animals they increased the level of celluar regeneration 3-4 times – compared to untreated aged animals.
However I thought the researchers gave the appropriate concern: “The researchers cautioned that shutting down the TGF-beta/pSmad3 pathway altogether by turning off the gene that controls it could lead to many health problems. The ability to suppress cell division is critical in controlling the development of tumors, for instance.”
And guess what, in humans long term calorie restriction reduces TGF-beta blood levels. Would this lead to better cellular regenerative potential? Additionally, calorie restriction is known to dramatically reduce cancer.
So you have the option of waiting X number of years to wait for a pill to reduce you TGF-beta levels or increase your notch to the right level (appropriate balance between the two so that you do not have an increased incidence of tumors or cancer). Or you an option that is available to you today to potentially increase your cellular repair potential.
Another interesting question is does exercise keep your stem cells young? Are there other practical interventions we can use to keep our stem cells health?
I do hope in the near future that big pharma can come up with something to mimic all the positive effects of calorie restriction, and I know they are spending millions of dollars and many hours on this potentially lucrative problem.
What are you doing today to keep your stem cells young?