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Ultrastructural immunolocalization of noncollagenous (osteopontin and osteocalcin) and plasma (albumin and α 2 HS‐glycoprotein) proteins in rat bone
Author(s) -
McKee Marc D.,
FarachCarson M.C.,
Butler W.T.,
Hauschka P.V.,
Nanci A.
Publication year - 1993
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1002/jbmr.5650080413
Subject(s) - osteoid , osteopontin , osteocalcin , chemistry , albumin , pathology , matrix (chemical analysis) , anatomy , biology , alkaline phosphatase , endocrinology , biochemistry , medicine , enzyme , chromatography
The high‐resolution, postembedding protein A‐gold immunocytochemical technique was used to visualize the distribution of two noncollagenous bone proteins, osteopontin (OPN) and osteocalcin (OC), and two plasma proteins, α 2 HS‐glycoprotein (α 2 HS‐GP) and albumin (ALB), in sections of Lowicryl K4M‐embedded rat tibial and alveolar bone. In the primary spongiosa of the metaphysis, a seam of organic material (lamina limitans) that labeled intensely with OPN and OC antibodies was observed at the bone/calcified cartilage interface just below the zone of vascular invasion of the growth plate. With deposition of bone matrix proper by osteoblasts in this region and its subsequent mineralization, extensive areas of bone were heavily labeled with anti‐OPN, anti‐OC, and anti‐α 2 HS‐GP antibodies, where the majority of gold particles were associated with amorphous, electron‐dense patches of organic material throughout the mineralized bone. In the unmineralized osteoid, substantially less labeling was observed, and where occasional mineralization loci were dispersed throughout the osteoid layer, these sometimes showed a concentration of gold particles. ALB labeling, on the other hand, was moderate and generally diffuse throughout the mineralized bone matrix and the osteoid. In alveolar bone, labeling patterns were generally similar to those found in tibial bone. Particularly striking in alveolar bone, however, was an intense anti‐OPN labeling of (1) the lamina limitans at cell‐lined bone surfaces, including that surrounding cell processes and osteocytes, (2) cement (reversal, resting) lines, and (3) the perilacumar matrix of some osteocytes. In summary, these data suggest that certain plasma proteins, such as α 2 HS‐GP, interact with bone matrix proteins, such as OPN and OC, at sites of tissue mineralization and that the presence of OPN in mineralized bone and at bone surfaces (lamina limitans) and cement lines has a multifunctional role, including regulation of mineralization and mediation of cell dynamics during endochondral and intramembranous bone modeling and remodeling.