Science Notes – Picking out Paget’s disease using proteomics

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Cross-section of a normal clavicle. (IMAGE: Paul Quigley, The Norton Priory Museum Trust)

In CA 338, we discussed proteomics – the study of proteins – and how it is quickly growing as a new way of analysing archaeological remains. That month’s ‘Science Notes’ explored how it had been applied to dental calculus, or plaque build-up, to assess an individual’s diet and health. Now research has used proteomics to help with the identification and diagnosis of ancient diseases, further proving its potential to revolutionise our understanding of health through history.

An international team of researchers coordinated by the University of Nottingham recently reassessed skeletons excavated at Norton Priory in Cheshire, all of which dated to the medieval period (AD 1020-1479). Earlier analyses of this collection had suggested that it included six individuals who may have been affected by a chronic skeletal disorder that resembled Paget’s disease of bone (PDB), but with many unusual features. To confirm these preliminary diagnoses, the team turned to proteomic analysis.

PDB is a relatively rare condition, characterised by a fault in the cellular remodelling of bone. Normally, bone undergoes a pattern of destruction and construction, creating a balance to make sure new bone can be made without weakening the existing support structure. In people with PDB, however, this balance is skewed and there is an increase in bone resorption, while any new bone formation is much more disorganised. This causes the bone to significantly weaken, and in extreme cases can lead to bone cancer. The cause of PDB is currently unknown, but it appears to be due to a combination of genetic and environmental factors.

The cross-section of a clavicle from an individual, buried at Norton Priory, affected by PDB. (IMAGE: Paul Quigley, The Norton Priory Museum Trust)

While osteological changes characteristic of PDB are often apparent from simply looking at a skeleton, macroscopic analysis of bone can never provide a definitive diagnosis. So, the team attempted to confirm these potential cases by identifying a protein, p62, which controls the cells responsible for destroying bone and which is frequently overexpressed in individuals with the disease, and faulty in those with familial (genetic) forms of the disorder.

First, they re-examined the six individuals identified as having PDB, and identified a further 12 individuals from the collection as having the disorder using radiography. They found that in each of these cases the disease was extensive, with up to 75% of each skeleton affected, and that some of the examined individuals had died quite young. Contemporary instances of PDB do not affect as many parts of the skeleton and normally only manifest in people over 55. It seems that these cases might represent a variant of the disease that is no longer present in modern populations.

To determine whether these cases were indeed PDB, the team took samples from seven of the identified individuals and two skeletons with no evidence of the disease. Mass spectrometry-based methods were used to detect ancient human p62 protein sequences in the affected individuals, and all results were confirmed using an alternative approach called western blotting.

In four of the seven sampled skeletons with probable PDB, p62 was identified, representing a molecular diagnosis of PDB. The protein was detected in the petrous bone of three samples, the femur of another, and a tooth of the last. While PDB commonly affects the skull and femur, the identification of p62 in the tooth is particularly interesting: it was not previously known that PDB affected the oral cavity. Crucially, p62 was not detected in the control skeletons.

Overall, the macroscopic identification of 18 individuals with PDB out of the 114 adult skeletons in the collection (15%), four of which have now been confirmed, is remarkable for a relatively rare disease. But PDB also appears to have been common in other nearby medieval centres. In CA 352, we saw that nearby in Poulton multiple individuals have been preliminarily diagnosed with the disease. Interestingly, the north-west of England is still considered a hot spot of PDB, although the number of cases has decreased in recent decades. It seems PDB has been affecting this region for centuries.

With the success of this project, proteomics is now set to expand even further into archaeological research. These results represent one of the first molecular diagnoses of an ancient disease based on proteomic analysis, but this is very likely to be just the beginning, as it opens the way for similar research to be done on other ancient diseases far back into history.

This article appeared in CA 353.

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