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Figure 1. Immunolocalization of SPARC in mouse periodontal tissues. (A) Immunostaining for SPARC in the first molar and surrounding tissues of a three-day-old mouse. SPARC is present in most cells, including the enamel epithelium, but is more strongly stained in odontoblasts (green arrows) and bone cells (red arrows). (B) In an enlarged section shown by the red rectangle in A, strong staining for SPARC is evident in osteoblasts, osteocytes, and the surrounding periosteal cells, with no staining evident in the bone matrix. (C) Immunostaining for SPARC in the incisor and surrounding tissues of the same mouse. Collagen-expressing periodontal ligament fibroblasts (magenta arrows) and cementoblasts (blue arrows), osteoblasts and osteocytes of the mandibular bone (red arrows), and odontoblasts (green arrows) all stain strongly for SPARC. However, while there was some staining of the matrix of the developing periodontal ligament and cementum, no staining was evident in the mineralized bone and dentin matrices. A weak staining for SPARC was also evident in the ameloblasts (black arrows). The SPARC was identified with the use of affinity-purified rabbit antibodies and specificity ascertained by staining similar sections from SPARC-null mice (not shown).
