Elasticity is essential to the function of many tissues, including the walls of our major arteries and the lens of the eye. The stiffening of these tissues with age leads to impairment of their function, resulting (amongst other conditions) in increasing hypertension and risk of renal failure with age. The increase in systolic blood pressure driven by loss of large artery elasticity is one of the major reasons for the increased risk of stroke and the development of dementia in older people.
The stiffening of our tissues with aging is caused in substantial part by the accumulation of chemical crosslinks between proteins of the extracellular matrix (ECM), the network of proteins between cells that gives our tissues their structure. In youthful tissues, ECM proteins are structured in a regular lattice, but subsequent crosslinks that accumulate during aging are located randomly, which causes the loss of elasticity. The creation of these crosslinks involves many chemical pathways and forms many differently-shaped structures, which are collectively called advanced glycation endproducts (AGE). Of these, it has been established that one specific AGE structure, called glucosepane, is the most abundant in aged human tissue.
A method or compound that would unlink glucosepane crosslinks from aging tissues would therefore be of great therapeutic value in the prevention and reversal of age-related tissue degeneration; yet it is not being energetically pursued in any academic institution or biotech lab, which elevates its priority for SRF research in critical-path analysis. We have therefore established and funded a GlycoSENS collaboration between researchers at Cambridge and Yale Universities, whose aim is to discover and test such a glucosepane “AGE-breaker” therapeutic.
Our Cambridge postdoc, Rhian Grainger, has identified and bought in a range of antibodies against AGEs, and tested them to see how good they are at finding the ‘authentic’ AGEs generated by the Yale group. The results are quite mixed, which has two important implications. Firstly, some of the research on AGEs that uses these antibodies may be wrong, which is important for our understanding of the possible effects of removing AGEs. Secondly, it means we have to make our own antibodies. The Cambridge group is working on this now: much of the routine work will be outsourced to specialist companies.
Rhian has also been working on making and analyzing AGE-cross-linked proteins, and finding chemical reagents that can selectively bind to these proteins. This is early stage work, but will develop the methods we need to check candidate glucosepane-targetting chemicals when we have them.
The other side of finding reagents that measure glucosepane breaking is having some real tissue to test. Because human tissue is hard to come by and comes with substantial safety, regulatory and ethical concerns, we plan to start out developing the methods on animal tissues. (This will also provide information on which animals models most closely reflect the AGE chemistry observed in humans. This will be important when we start to take potential treatments into animal tests.) The Cambridge group has just started a collaboration with Prof. Alun Williams and the Cambridge Veterinary School to get samples of tissue from old animals. This is critical to the project, as common sources of tissue (from lab animals or from the butcher’s shop) are from quite young animals, and so are not that relevant to what goes on in old humans. We hope to report more on this exciting resource in the coming months.