Bae SH, et al: Hepatic Oval Cell Proliferation via COX-2 Signaling 369 ally, immunofluorescence staining of α-smooth muscle actin CD45 (BD Biosciences) was performed on isolated Thy1+ HOCs. (SMA) (Abcam) with COX-2 was performed, using a previously Signals were detected using a Vector ABC Kit (Vector Laborato- described cytochemical method, to exclude myofibroblasts as the COX-2 source.35 Immunostaining for OV-6 (R & D Systems, ries, Burlingame, CA, USA) and 3,3’-diaminobenzidine tetrahy- drochloride (DakoCytomation). Finally, BrdU (DakoCytomation) Minneapolis, MN, USA), COX-2, Thy1.1, albumin (DakoCytoma- staining was conducted for the HOC proliferation assay on FN- tion, Carpinteria, CA, USA), AFP (DakoCytomation), FN, and coated culture dishes following NS398 treatment, as described Fig. 1. Proliferation of hepatic oval cells (HOCs) on day 9 after induction of the 2-acetylaminofluorene (2-AAF)/70% partial hepatectomy (PHx) model. Immunohistochemical (IHC) staining is conducted to detect OV-6, thymus cell antigen1 (Thy1), and cyclooxygenase (COX)-2. (A) Hema- toxylin and eosin staining (magnification, ×400). (B) OV-6 IHC staining in activated HOCs. OV-6 is a hepatic oval cell marker (magnification, ×400). (C, E) Thy1 and (D, F) COX-2 IHC staining in activated HOCs (magnification, ×100 and ×400, respectively).