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During ageing, cellular and physiological processes naturally decline and this is a particular problem in collagen-rich tissues such as the articular cartilage and bone, where tissue turnover is low and repair of the tissue is reduced with age. Reduced repair capacity increases the risk of common age-related diseases such as osteoarthritis (OA), non-union after bone fracture, and osteoporosis.
Protein studies have previously indicated levels of protein in a tissue at any given time, but are unable to provide information on how much is being newly synthesised and incorporated into the tissue. A new study, published in ELife, uses a new methodology that gives researchers the ability to examine protein synthesis in situ, providing details of activity in the tissues under normal physiological conditions at different ages.
The tissues in the cartilage, bone and skin are made up of an extracellular matrix (ECM), which is a dynamic network composed of collagens and proteins, and collectively known as the matrisome.
The research team at the Kennedy Institute used an in vivo technique called pulsed SILAC labelling in healthy mice to show changes in the synthesis of proteins of the matrisome over three stages of life: during maximum skeletal growth, and at young, and older adulthood.
Metabolic labelling with stable isotopes in combination with quantitative proteomics were used to estimate the rates of incorporation of new proteins into cartilage, bone and skin. Plasma was used as a reference tissue comparator.
The study found that comparing young adult with older adult mice, new protein incorporation was reduced in all tissues and this was particularly marked in cartilage and bone. Changes were less apparent in skin, perhaps in line with what is known about its ability to self-renew throughout the healthy lifespan.
Tonia Vincent, Professor of Musculoskeletal Biology said: "Although new protein incorporation changes significantly in all tissues after skeletal maturity, it displays distinct temporal and molecular tissue signatures. As some of these changes affect pathways implicated in age-related disease, the study may be identifying tissue changes that predispose to subsequent osteoarthritis and osteoporosis."