A therapy that can robustly correct any mitochondrial DNA mutation throughout the body can be turned into a way to rejuvenate the stochastic damage of aging that occurs to the thirteen important mitochondrial genes not replicated in the cell nucleus. If asked to wager, based on the evidence I'd suggest that mitochondrial damage is the largest individual contribution to aging, which is why it's important to see progress on fixing it or making it irrelevant. So this, I think, is a development worth watching: "Researchers [have] identified, for the first time, a generic way to correct mutations in human mitochondrial DNA by targeting corrective RNAs ... I think this is a finding that could change the field. We've been looking to do this for a long time and we had a very reasoned approach, but some key steps were missing. Now we have developed this method and the next step is to show that what we can do in human cell lines with mutant mitochondria can translate into animal models and, ultimately, into humans. ... Gene therapy is often used to express proteins that can treat the cause of a variety of diseases. In this case, [researchers] developed a strategy to target and import specific RNA molecules encoded in the nucleus into the mitochondria and, once there, to express proteins needed to repair mitochondrial gene mutations. First, the research team had to figure out a way to stabilize the reparative RNA so that it was transported out of the nucleus and then localized to the mitochondrial outer membrane. This was accomplished by engineering an export sequence to direct the RNA to the mitochondrion. Once the RNA was in the vicinity of the transport machinery on the mitochondrial surface, then a second transport sequence was required to direct the RNA into the targeted organelle. With these two modifications, a broad spectrum of RNAs were targeted to and imported into the mitochondria, where they functioned to repair defects in mitochondrial respiration and energy production in two different cell line models of human mitochondrial disease. ... This study indicates that a wide range of RNAs can be targeted to mitochondria by appending a targeting sequence with or without a mitochondrial localization sequence, to provide an exciting, general approach for overcoming mitochondrial genetic disorders."