Bone sialoprotein (BSP) secretion and osteoblast differentiation: relationship to bromodeoxyuridine incorporation, alkaline phosphatase, and matrix deposition

• Published in: The journal of histochemistry and cytochemistry Vol. 41; no. 2; pp. 183 - 191
• Main Authors: Bianco, P, Riminucci, M, Bonucci, E, Termine, JD, Robey, PG
• Format: Journal Article
• Language: English
• Published: Los Angeles, CA Histochemical Soc 01.02.1993; SAGE Publications; Histochemical Society
• Subjects: Alkaline Phosphatase - metabolism; Animals; Biological and medical sciences; Bone Matrix - metabolism; Bromodeoxyuridine - metabolism; Cell Differentiation; Cell Division; Embryology: invertebrates and vertebrates. Teratology; Fundamental and applied biological sciences. Psychology; Histocytochemistry; Immunoenzyme Techniques; Integrin-Binding Sialoprotein; Organogenesis. Fetal development; Organogenesis. Physiological fonctions; Osteoblasts - cytology; Osteoblasts - metabolism; Osteogenesis; Rats; Rats, Wistar; Sialoglycoproteins - secretion; Space life sciences; Alkaline phosphatase; Embryonic development; Rat; Enzyme; Rodentia; Gene expression; Vertebrata; Mammalia; Sialoproteins; Osteoblast; Fetus; Skeleton; Bone; Differentiation; Osteogenesis
• ISSN: 0022-1554; 1551-5044
• DOI: 10.1177/41.2.8419458

We defined two distinct maturational compartments (proliferative and secretory) of osteogenic cells in vivo on the basis of ALP activity, BrdU incorporation, cell shape, and BSP production. BSP immunoreactivity was found to mark cells in the secretory but not in the proliferative compartment. We established the phenotypic similarity of primitive marrow stromal cells with proliferating perichondral cells (fibroblast-like, ALP+, BrdU+, BSP-). This suggests the potential functional equivalence of the two cell types as committed non-secretory osteogenic cells and points to the duality of osteogenic cell compartments as a generalized feature of bone formation. We further showed that although BSP secretion is a hallmark of the onset of osteogenesis, BSP antigenicity is lost both in osteoid and in a large proportion of mature osteoblasts during subsequent phases of bone deposition. This suggests that bone formation may not be a uniform event, as bone cells actually deposit antigenically, and likely biochemically, distinct matrices at specific times.