AB0113 A MINIMAL-INVASIVE METHOD TO RETRIEVE AND IDENTIFY ENTHESEAL TISSUE FROM PSORIATIC ARTHRITIS PATIENTS

Abstract

BackgroundEnthesitis represents a hallmark feature of spondyloarthritis, including psoriatic arthritis (PsA).1 So far, most of the data on enthesitis in PsA are based on clinical assessment of tenderness as well as MRI or ultrasound examinations.2 These approaches, however, do not allow molecular analysis of entheses, which will require acquisition of entheseal tissue. Up today, it is unknown, which entheseal structure in humans would qualify for a feasible biopsy and how correct sampling of entheseal structures could be ascertained within such biopsy material. These technical challenges have led to substantial lack of knowledge on human entheseal tissues.ObjectivesTo establish a minimally invasive biopsy technique of human entheses for the analysis of entheseal tissue in patients with PsA.MethodsHuman cadavers were used for establishing the technique to retrieve tissue from the lateral humeral epicondyle enthesis (cadaveric biopsies). After biopsy, the entire entheses was surgically resected (cadaveric resections). Biopsies and resections were assessed by label-free second-harmonic-generation (SHG) microscopy. The same biopsy technique was then applied in PsA patients with subsequent definition of entheseal tissue by SHG.ResultsEntheseal biopsies were performed in five cadavers and allowed the retrieval of entheseal tissue, validated by analysis of the resection material. Thus, microscopy of biopsy and resection sections allowed differentiation of entheseal, tendon and muscle tissue by SHG and definition of specific intensity thresholds for entheseal tissue. The same method was then successfully applied to 10 PsA patients. Hence, the fraction of entheseal tissue within the PsA biopsy specimens was high (65%) and comparable to the fraction retrieved in cadaveric biospies (68%) as assessed by SHG microscopy.ConclusionEntheseal biopsy of the tendon plate of the lateral epicondyle is feasible in PsA patients allowing reliable retrieval of entheseal tissue and its identification by SHG microscopy.References[1]Schett, G, Lories D, D´Agostino MA, Elewaut E, Kirkham B, Soriano ER, McGonagle D. Enthesitis: from pathophysiology to treatment Nat Rev Rheumatol 2017 Nov 21;13(12):731-741.[2]Groves C, Chandramohan M, Chew NS, et al. Clinical Examination, Ultrasound and MRI Imaging of The Painful Elbow in Psoriatic Arthritis and Rheumatoid Arthritis: Which is Better, Ultrasound or MR, for Imaging Enthesitis? Rheumatol Ther 2017;4:71-84.Disclosure of InterestsNone declared