Lamina Propria Collagen Architecture in Interstitial Cystitis/Bladder Pain Syndrome

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a heterogeneous condition of uncertain etiology. We assessed bladder collagen characteristics in phenotypically characterized IC/BPS patient subgroups that may influence pathophysiology. Forty-four females (30 IC/BPS; 14 non-IC/BPS) were included. Patients were divided into groups based on Hunner lesions (HL; N=14 or non-HL; N=16) and anesthetic bladder capacity (BC) (BC≤500 cc; low BC; N=17 or BC>500 cc; non-low BC; N=13). Bladder biopsy tissue slides were stained with hematoxylin and eosin or picrosirius red and semi-quantitatively analyzed by a pathologist. CT-FIRE software was used to quantitatively assess lamina propria collagen. All patients with IC/BPS had lower collagen fiber density independent of subgroup (p<0.0001-0.0038) compared to controls. HL had more peri-muscular collagen accumulation (p=0.0061), more acute inflammation (p=0.0364), more severe chronic inflammation (p=0.0088), and narrower collagen fibers than non-HL and controls. Non-low-BC patients had lower collagen density (p=0.0075) and straighter collagen fibers (p=0.0127) than low BC. Low-BC patients had narrower collagen fibers than control (p=0.0096). IC/BPS, regardless of subgroup, is associated with a bladder lamina propria with diminished collagen density. HL, non-low-BC, and low-BC subgroups have unique collagen characteristics. These findings suggest a collagen fiber destruction and redistribution process, which differs by subgroup, and may contribute to pathophysiology of IC/BPS.