A potential prognostic test for bone erosion development in patients with cutaneous predictive sites for psoriatic arthritis.

Claudio Lembo1, Annunziata Raimondo1, Nicola Balato1, Fabio Ayala1, Anna Balato2
1Department of Clinical Medicine and Surgery, University of Naples Federico II, Italy
2Department of Advanced Biomedical Sciences, University of Naples Federico II, Italy

Corresponding author:
Annunziata Raimondo
Department of Clinical Medicine and Surgery
University of Naples Federico II, Italy
¬¬¬+393294376459; +390817462457
nunzia.raimondo@libero.it













Aim of the study
Aim of this study was to assess if psoriatic cutaneous inflammation in predictive areas for psoriatic arthritis (PsA) influenced osteoclast differentiation and maturation as well as if osteoclastogenic assay might represent a prognostic test for bone damage onset. 
Materials and methods
For this purpose, 20 psoriatic patients (Pso) not including PsA were enrolled: 10 with cutaneous manifestations in predictive sites for PsA (nail, scalp, intergluteal cleft and site of sacrum) and 10 without. Moreover, 10 healthy subjects and 10 patients affected by rheumatoid arthritis (RA), typical erosive arthritis, were recruited as negative and positive controls, respectively. Blood samples were taken from all subjects. Monocytes were isolated and cultured in Osteo Assay Surface 96-well plate with complete RPMI medium plus M-CSF. After 14 days, cells were stained for tartrate-resistant acid phosphatase (TRAP) and TRAP-positive cells with three or more nuclei were counted as osteoclast precursors (OCPs). Once counted, they were removed and resorption areas were quantified. 
Results
Our results showed that OCP differentiation was increased in all Pso patients compared with healthy subjects. Interestingly, comparing within Pso patients, OCPs were more significantly increased and active in those with psoriatic plaques involving the predictive sites for PsA, having equal PASI. 
Conclusions
These data suggest that psoriatic skin inflammation of specific body areas epidemiologically associated to an augmented risk of PsA could be related to an enhanced risk of bone damage, too. In conclusion, we suppose that the assessment of osteoclastogenic profile in these patients might acquire a prognostic feature for erosive bone injuries linked to PsA.