BPH is one of the most common diseases among aging males with the incidence reaching 80% or higher for those over 80 years old (Chughtai et al., 2016, Berry et al., 1984). Although it is not life threatening, the lower urinary tract symptoms (LUTS), such as intermittent urinary stream, urgent incontinence, post-micturition dribbling etc., can be bothersome and have a negative impact on the quality of life of BPH patients (Chughtai et al., 2016, Lower urinary tract symptoms: Evidence Update, 2012, Copyright, 2012). The dysregulation of androgen and estrogen, imbalance between cell proliferation and apoptosis, stromal-epithelial interaction and tissue fibrosis caused by inflammation may all play a role, either singly or in combination, in the etiology of the hyperplastic process (Vignozzi et al., 2016, Shapiro and Lepor, 1994). Despite the significant progress made in exploring the cause-and-effect mechanisms of BPH, the precise molecular etiology of this illness remains vague. Thus, it is critical to identify novel markers and rediscover new therapeutic targets for BPH.

As experimental technology develops, from polymerase chain reaction (PCR) to multi-omics, increasing numbers of BPH-related molecular pathways will be elucidated. Research on various illnesses, including BPH, has focused heavily on the identification of differentially expressed genes (DEGs) to examine molecular pathways, searching for diagnostic indicators, and discovering therapeutic targets by transcriptome sequencing (RNA-seq) (Lepor, 2004, Ke et al., 2019). Indeed, a comparative study conducted by Zhao et al (Middleton et al., 2019). had obtained comprehensive transcriptional data in prostatic stromal cells of various histological origin, which revealed that S100A4 was one of the most upregulated genes in BPH versus the normal transition zone. Until now, none of those studies were in-depth enough to clarify the functional actions and underlying molecular mechanisms of this stromal protein in the development of BPH.

S100A4, also known as FSP1 (fibroblast-specific protein 1), belongs to the S100 Ca2+-binding protein superfamily. S100A4 protein functions both intra- and extracellularly, and regulates a variety of cellular processes including cell cycle progression, cell survival, motility and epithelial-mesenchymal transition (Zhao et al., 2007, Gonzalez et al., 2020, Donato, 1999, Donato, 2001). Previous studies demonstrated that S100A4 was intimately connected to the mitogen activated protein kinase (MAPK) signaling pathway (Garrett et al., 2006). The MAPK pathway contains c-Jun NH2-terminal kinase (JNK), p38 MAPK, and extracellular signal-regulated kinase (ERK), all of which are involved in complicated cellular programs such as proliferation, apoptosis and differentiation (Dahlmann et al., 2014). Indeed, our recent research discovered that functional abnormalities in the MAPK cascades may be involved in an imbalance between cell proliferation and apoptosis, which facilitates the advancement of BPH (Cagnol and Chambard, 2010, Xiao et al., 2020).

Apart from a cell survival-promoting effect, S100A4 was also involved in the pathophysiology of fibrosis (Liu et al., 2021a, Xia et al., 2017, Fei et al., 2017, Iwano et al., 2002). It was reported that α‐SMA and collagen I were up-regulated by exogenous S100A4 treatment in both hepatic stellate cells and lung fibroblasts (Li et al., 2020, Chen et al., 2015, Li et al., 2018a). Additionally, downregulation of S100A4 had been shown to retard myocardial fibrosis through the Wnt/β-catenin pathway (Zhang et al., 2018). Rising evidence suggests that there is a close relationship between the tissue fibrosis process and activation of the classical Wnt/β-catenin pathway (Qian et al., 2018, Duchartre et al., 2016, Hu et al., 2020, Miao et al., 2019, Beljaars et al., 2017). Importantly, our recent study reported that simvastatin (an older lipid-lowering medication) might suppress prostate fibrosis via deactivation of the classic Wnt/β-Catenin Pathway (Tao et al., 2016).

In our current study, the expression and localization of S100A4 protein was investigated. Loss- and gain-of function assays were performed to analyze alteration of cell proliferation, cell apoptosis and fibrosis process, as well as to identify signal transduction via the MAPK and Wnt/β-catenin pathway.