Principal investigator: J.C. Aurégan
The organic matrix of the vast majority of tissues in the human body is composed of different types of collagen, and in particular type I collagen, which represents 90% of the bone tissue matrix, 85% of the dentin matrix and between 60 and 80% of the collagen in the skin dermis. Its fibrous structure gives it important mechanical properties. This structure also plays a critical role in the mineralization process by allowing the formation of hydroxyapatite crystals due to the existence of nucleation sites located in particular places in these fibres.
Modifications in the production or the quality of collagen strongly affect the mechanical properties of the tissue. We can cite i/ collagen pathologies such as osteogenesis imperfecta, also called “brittle bone disease”, which makes bones very fragile, ii/ ageing, which reduces the mechanical resistance of bone tissue frequently leading to fractures and iii/ the deterioration of collagen during ageing of the skin which is well known in dermatology and can be linked to the topography of the skin (wrinkles) characterized with the skin patch technique (Sampson, Nature 1961). As early as 2005, Shuster (Shuster, Med Hypotheses 2005) suggested that the quantitative and qualitative alterations of collagen related to intrinsic ageing would happen at the same speed in bones and skin. We hypothesized that skin topography could be used as a clinical diagnostic tool for bone tissue quality (patent WO/2019/149393). In this regard, our project is articulated aroun three main axes :
1/ Artificial intelligence for clinical diagnosis
The development of a “watershed”-type segmentation of skin patch images acquired with a smartphone makes it possible to instantly characterize the skin topography. This new technology allows non-invasive and reliable analysis of the patient in a clinical environment. In this context, a deep learning approach applied to both image processing and patient metadata (age, sex, weight) should provide an accurate and reliable classification tool for collagen degradation.
2/ Diagnosis of osteogenesis imperfecta
In a lack of family history, the diagnosis of osteogenesis imperfecta can be difficult because it is based on a combination of clinical and paraclinical cues. If the diagnosis is evoked when repeated fractures are observed in a child, a suspicion of abuse may also be raised, which leads to a delicate and very difficult situation for all people concerned; the aim always being to provide the best care and protect the child. For several years, our team has been working on osteogenesis imperfecta and in particular on the biomechanical properties of bone and dental tissue (in collaboration with Pr C. Chaussain). Our objective is to set up a diagnostic clinical study to analyze the skin topography of patients affected by this collagen pathology in relation to the mechanical properties of these mineralized tissues.
3/ Diagnosis of contralateral femoral neck fracture
Contralateral femoral neck fracture affects the very elderly and leads to a 50% increased risk of mortality in these patients. If the link between skin topography and skin collagen deterioration is well demonstrated between different age groups (20-40 years, 40-60 years, 60 years and over), this link has never really been studied in the very elderly patient. In the perspective of using the skin patch as a diagnostic tool, our project consists in analyzing the correlations between skin topography, the collagen/elastin ratio of the dermis, and the mechanical properties of bone tissue in very elderly peoples.
Publications of the project
Aurégan, J.-C., Frison, A., Bégué, T., Hannouche, D., Bosser, C., Bensidhoum, M., Hoc, T. Contra-lateral hip fracture in the elderly: are decreased body mass index and skin thickness predictive factors? (2017) International Orthopaedics, 41 (2), pp. 247-252. Link for the publication .
Aurégan, J.-C., Bosser, C., Bensidhoum, M., Bégué, T., Hoc, T. Correlation between skin and bone parameters in women with postmenopausal osteoporosis: A systematic review (2018) EFORT Open Reviews, 3 (8), pp. 449-460. Link for the publication .