Epimorphin in bleomycin-induced pulmonary fibrosis in mice

Increased expression of epimorphin in a peritoneal fibrosis mouse model

BACKGROUND

Long-term peritoneal dialysis results in functional and histopathological alterations of the peritoneal membrane, leading to peritoneal fibrosis (PF). The mechanism of PF has not been fully elucidated, and at present there is no effective therapy for PF. Epimorphin is a mesenchymal protein that not only regulates morphogenesis in organ development but is implicated in tissue repair. However, the role of epimorphin in PF has not yet been clarified.

METHODS

PF was induced in C57/Bl6 mice by intraperitoneal injection of chlorhexidine gluconate (CG-injected mice) three times a week for 3 weeks. The parietal peritoneum was subsequently dissected and assessed by Masson's trichrome staining, and epimorphin expression was analysed by immunohistochemistry and real-time reverse transcription polymerase chain reaction (RT-PCR). Furthermore, epimorphin-positive regions were analysed by multiple immunofluorescence staining using fibrosis-associated markers. In addition, normal rat fibroblast cells (NRK-49F) were treated with transforming growth factor-β (TGF-β) in the presence or absence of epimorphin. The expression of fibrosis-associated markers was assessed by real-time RT-PCR.

RESULTS

In CG-injected mice, Masson's trichrome staining showed marked thickening of the submesothelial compact zone. Weak epimorphin expression was observed in the narrow submesothelial compact zone beneath the mesothelial cells in control mice; however, epimorphin expression was stronger in the submesothelial compact zone in CG-injected mice. Epimorphin expression was observed mainly in α-smooth muscle actin (α-SMA)-positive myofibroblasts. Epimorphin suppressed the TGF-β-induced upregulation of α-SMA and platelet-derived growth factor receptor-β in cultured cells.

CONCLUSIONS

Our results suggest that epimorphin may be a therapeutic target for fibrotic diseases of the peritoneum.

Involvement of epimorphin in the repair of experimental renal fibrosis in mice

Interaction between epithelial cells and mesenchymal cells is essential in normal organ morphogenesis and in tissue repair after injury. Epimorphin, a mesenchymal protein that regulates epithelial morphogenesis through epithelial-mesenchymal interactions, has recently attracted attention as an important modulator of tissue repair. In this study we analyzed the role of epimorphin in renal fibrosis. We first found a progressive increase in epimorphin expression corresponding to the progression of renal fibrosis in mice with unilateral ureteral obstruction (UUO). To determine whether this expression has a role in the repair or progression of renal fibrosis, we analyzed a model of renal fibrosis repair, the UUO-release (UUO-R) model. Epimorphin expression was increased at 3 and 7 days after the UUO-R rather than on the day of release, but was decreased at 21 days after the release. Inhibition of endogenous epimorphin with anti-epimorphin antibody (MC-1) significantly delayed the repair of fibrosis. When compared with normal-IgG-injected mice, MC-1-injected mice showed significantly decreased renal matrix metalloproteinase (MMP)-2 and MMP-9 expressions by western blotting and increased expression of TGF-beta and collagen-I mRNA by real-time RT-PCR. Recombinant epimorphin induced prominent increases in MMP-2 and MMP-9 activities in the culture media of renal interstitial fibroblasts in vitro. These findings indicate that epimorphin has a pivotal role in the repair of renal fibrosis by modulating both extracellular matrix (ECM) degradation and its production.

Delivering the message: epimorphin and mammary epithelial morphogenesis

The mammary gland consists of a highly branched tubular epithelium surrounded by a complex mesenchymal stroma. Epimorphin is an extracellular protein that is expressed by mammary mesenchymal cells that directs epithelial morphogenesis. Depending upon the context of presentation--polar versus apolar--epimorphin can selectively direct two key processes of tubulogenesis: branching morphogenesis (processes involved in tubule initiation and extension) and luminal morphogenesis (required for enlargement of tubule caliber). Here, we outline the fundamentals of mammary gland development and describe the function of epimorphin in these processes. We conclude with a review of recent studies that suggest similar morphogenic roles for epimorphin in other glandular organs.