Regenerative medicine holds great - albeit not unlimited - promise for extending healthy life by replacing age-damaged tissue, and ultimately replacing age-damaged organs. However, as for everything involving our biology, the path forward is not as simple as it might appear. Repairing the damage of aging by simply replacing tissue - even assuming you've repaired any age-related damage in the stem cells taken from the patient to use in therapy - runs into the interconnected nature of the body's systems:

Tissue engineering for a new heart, plus the necessary understanding to repair any damage in your stem cells? One problem you quickly run into in this sort of thought experiment is that everything of importance is influenced by everything else. New cells will be damaged by the old intracellular environment, as well as by the actions of old cells next door. An age-damaged immune system can't protect rejuvenated cells in a new heart.

And so on; I'm sure you could list many more important connections that will trip you up if you replace only one component of the aging body. This is a challenge for the near future of regenerative medicine - also known as cell therapy in its present form - as this paper reminds us:

Cell therapy is a promising option for treating ischemic diseases and heart failure. Adult stem and progenitor cells from various sources have experimentally been shown to augment the functional recovery after ischemia, and clinical trials have confirmed that autologous cell therapy using bone marrow-derived or circulating blood-derived progenitor cells is safe and provides beneficial effects.

However, aging and risk factors for coronary artery disease affect the functional activity of the endogenous stem/progenitor cell pools, thereby at least partially limiting the therapeutic potential of the applied cells. In addition, age and disease affect the tissue environment, in which the cells are infused or injected. The present review article will summarize current evidence for cell impairment during aging and disease but also discuss novel approaches how to reverse the dysfunction of cells or to refresh the target tissue. Pretreatment of cells or the target tissue by small molecules, polymers, growth factors, or a combination thereof may provide useful approaches for enhancement of cell therapy for cardiovascular diseases.

A challenge, but not an impassable barrier. As I've said before, present directions in research and funding culture suggest that the regenerative medicine research community - large and well funded - will soon be branching out into attempts to repair the damage of aging at the cellular level. That is a natural outgrowth of trying to make cell therapies and tissue engineering work more effectively in the aged:

One consequence of the dominance of the aging [stem cell] niche is the direction taken in order to develop the next generation of stem cell therapies. Clearly it's not enough to gain far better control over stem cells if the damaged niche then sabotages your efforts.

I believe that this will likely see the large and well-funded regenerative medicine industry start down the path of trying to rejuvenate and repair stem cell niches. I don't know when that will start in earnest, but it will be a tremendous opportunity for those of us interested in the success of more general strategies for biochemical repair throughout the body - a chance to apply large-scale funding and a large research community to specific challenges in repairing the damage of aging.

Posted by Reason at June 9, 2008 8:29 AM | TrackBack (0)