PROJECT SUMMARY Healthcare costs for lower urinary tract symptoms (LUTS) ascribed to benign prostatic hyperplasia/hypertrophy (BPH) are billions of dollars annually. BPH/LUTS is a debilitating disease that affects nearly all aged men. BPH can be a lethal disease (kidney disease/urinary retention) and world-wide it has been estimated that more men die from BPH than prostate cancer. Therapies for BPH/LUTS target smooth muscle contractility with α-blockers or hyperplasia with 5α-reductase inhibitors. Although these therapies can be medicinal, they are not effective/durable for all; this leaves millions of men needing more effective therapies. Estrogens and downstream targets are important in the development and progression of BPH/LUTS, yet there are no medical treatments directed at these pathways. The standard of medical care for BPH/LUTS currently over-treats the BPH/LUTS patient population, in part due to a poor understanding of etiology and progression of the disease. There is an apparent need to define what BPH represents in patient populations as well as to identify the true anatomic, cellular, and molecular causes of the disease. Clarification here may elucidate the true causes in development and progression of this disease as well as institute effective strategies and therapies. We and others have previously demonstrated prostatic collagen deposition coincident with prostate stiffness, LUTS, and failed medical treatment supporting the concept that BPH/LUTS is, in part, a fibrotic disease. Moreover we propose estrogens mediate prostate fibrosis and associated LUTD. The goal of this research is to identify the anatomical, cellular, and molecular origins of prostate fibrosis in men with BPH/LUTS and understand its regulation by the estrogen pathway. Recently, estrogens, specifically signaling through estrogen receptor (ER)-α, was discovered to be necessary for the development of LUTD in mice. Although, multiple stromal and epithelial cells express ER-α, we provide evidence that ER-α positive stromal cells are responsible for increased collagen deposition. These cells are sensitive to estrogens and produce large amounts of collagen in vitro and in vivo. Therefore we propose to identify the tissue specific ER-? regulation of prostate fibrosis/LUTD. At the same time we will determine if fibrosis/collagen accumulation acts independently or in collaboration with prostate hyperplasia. Additionally, we will determine the ER molecular mechanism of action in the transcription of Col1a1 by determining if classical or non-classical ER signaling is necessary. We will also determine if therapeutic selective ER-? modulators (SER?Ms) are effective in the treatment of prostate fibrosis and alleviate associated urinary dysfunction. Lastly, stratification of men with fibrotic prostates is imperative to increase BPH treatment efficacy. To address this challenge, novel collagen MRI techniques will be used to assess whether prostatic fibrosis can be identified in p...