![Figure 2. SPARC is expressed by CD146+ BM-MSCs and associates with components of the expanded osteoblastic niche in osteosclerosis. (A) Immunohistochemical analysis of SPARC and CD146 (AEC, red signal) expression in PMF BM sections. Several SPARC-expressing stromal cells show subendothelial distribution and reticular morphology (black arrows, inset), which overlap those of CD146+ BM-MSCs (black arrows, inset). Representative immunostained sections of the 114 evaluated are shown. Original magnifications ×400, insets ×630. Scale bars represent 50 μm. (B) Confocal microscopic analysis for SPARC (green signal) and CD146 (red signal) expression in PMF shows that, in addition to MKs and stromal cells expressing SPARC (white arrows), a subset of stromal cells with a perivascular distribution coexpresses SPARC and CD146 (yellow arrows and insets). Representative immunostained section of the 30 evaluated is shown. Original magnifications ×200 (top panels) and ×400 (bottom panels and insets). Scale bars represent 100 and 50 μm, respectively. (C) Immunohistochemical analysis for collagen type I (Coll-I) and fibronectin (Fibro; 3-3′-diaminobenzidine [DAB], brown signal) in sections from prefibrotic (PMF-0) and advanced PMF (PMF-3) cases. In the former (left panels), the 2 ECM components display selective localization at the endosteal edge of the bone trabeculae (black arrows) while undergoing a significant increase in expression and diffusion in the latter (right panels). Representative immunostained sections of the 30 evaluated are shown. Original magnifications ×400. Scale bars represent 50 μm. (D) Confocal microscopic analysis for SPARC (red signal) and collagen type I (Coll-I, green signal) expression showing that these 2 proteins colocalize in the sclerotic foci of an advanced PMF case (PMF-3). Representative immunostained sections of the 30 evaluated are shown. Original magnifications ×200. Scale bars represent 100 μm. (E) Immunohistochemical analysis of SPARC (red signal) showing its expression in osteoblasts (black arrows) lining bone trabeculae in myeloid malignancies undergoing osteosclerotic progression (PMF-3). Representative immunostained sections from 2 cases of the 30 evaluated are shown. Original magnifications ×400 (left panel) and ×630 (right panel). Scale bars represent 50 and 30 μm, respectively.](https://ash.silverchair-cdn.com/ash/content_public/journal/blood/120/17/10.1182_blood-2011-12-398537/4/zh89991298110002.jpeg?Expires=1743077442&Signature=iAGaUEw4J4TZFOFTIbEG7kajYiNWoYVVR0md~zJKqgK~JSttu1a3~-YnhxCWQftilYz9WWRQttemIdSdB8dzZ3eUgtoVJS2Z6Xu8i-aLePpN1cOukaoOrClVFXCHyGruzd~Q1pk3ZM~sXGff6T4E~Po3nzC6fnjzf6w5fR2qWctkXYMXfgDhMK6YMdpAMJHJUrLbJxbbrAf0618~rMBpbTrcmjpjA717lq-DjZ6kNwKtnCRROGDUwcLdesfJLAjxsytZl25KdRy3mj4IcmiQXZacH1opR5jF7CDEyWW2HrltKvG2w4Kui1oyf~fcK4xpgYS1kcLVg6JFV9vS3KSSpQ__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
SPARC is expressed by CD146+ BM-MSCs and associates with components of the expanded osteoblastic niche in osteosclerosis. (A) Immunohistochemical analysis of SPARC and CD146 (AEC, red signal) expression in PMF BM sections. Several SPARC-expressing stromal cells show subendothelial distribution and reticular morphology (black arrows, inset), which overlap those of CD146+ BM-MSCs (black arrows, inset). Representative immunostained sections of the 114 evaluated are shown. Original magnifications ×400, insets ×630. Scale bars represent 50 μm. (B) Confocal microscopic analysis for SPARC (green signal) and CD146 (red signal) expression in PMF shows that, in addition to MKs and stromal cells expressing SPARC (white arrows), a subset of stromal cells with a perivascular distribution coexpresses SPARC and CD146 (yellow arrows and insets). Representative immunostained section of the 30 evaluated is shown. Original magnifications ×200 (top panels) and ×400 (bottom panels and insets). Scale bars represent 100 and 50 μm, respectively. (C) Immunohistochemical analysis for collagen type I (Coll-I) and fibronectin (Fibro; 3-3′-diaminobenzidine [DAB], brown signal) in sections from prefibrotic (PMF-0) and advanced PMF (PMF-3) cases. In the former (left panels), the 2 ECM components display selective localization at the endosteal edge of the bone trabeculae (black arrows) while undergoing a significant increase in expression and diffusion in the latter (right panels). Representative immunostained sections of the 30 evaluated are shown. Original magnifications ×400. Scale bars represent 50 μm. (D) Confocal microscopic analysis for SPARC (red signal) and collagen type I (Coll-I, green signal) expression showing that these 2 proteins colocalize in the sclerotic foci of an advanced PMF case (PMF-3). Representative immunostained sections of the 30 evaluated are shown. Original magnifications ×200. Scale bars represent 100 μm. (E) Immunohistochemical analysis of SPARC (red signal) showing its expression in osteoblasts (black arrows) lining bone trabeculae in myeloid malignancies undergoing osteosclerotic progression (PMF-3). Representative immunostained sections from 2 cases of the 30 evaluated are shown. Original magnifications ×400 (left panel) and ×630 (right panel). Scale bars represent 50 and 30 μm, respectively.
