title: SPARC and the N-propeptide of collagen I influence fibroblast proliferation and collagen assembly in the periodontal ligament.
abstract: The periodontal ligament (PDL) is a fibrous connective tissue that anchors tooth cementum into alveolar bone. Secreted protein acidic and rich in cysteine (SPARC) is a collagen-binding matricellular protein known to influence collagen fiber assembly in the PDL. In contrast, functional properties of the N-propeptide of collagen I, encoded in exon 2 of the COL1A1 gene, are poorly understood. In this study, the PDL of collagen I exon 2-deleted (wt/ko), SPARC-null (ko/wt), and double transgenic (ko/ko) mice were evaluated in terms of cellularity, collagen area, fiber morphology, and extraction force and compared to WT (wt/wt) mice. Picro sirius red staining indicated a decrease in total PDL collagen content in each of the transgenic mice compared to WT at 1 and 3 month age points. At 12 months, only SPARC-null (ko/wt) and double-null PDL demonstrated less total collagen versus WT. Likewise, an increase in thin PDL collagen fibers was observed at 1 and 3 months in each transgenic, with increases only in SPARC-null and double-null mice at 12 months. The force required for tooth extraction was significantly reduced in SPARC-null versus exon 2-deleted and WT mice, whereas double-null mice demonstrated further decreases in force required for tooth extraction. The number of proliferating fibroblasts and number and size of epithelial rests of Malassez were increased in each transgenic versus WT with double-null PDL exhibiting highest levels of proliferation and rests of Malassez at 1 month of age. Consistent with increases in PDL collagen in exon-2 deleted mice, with age, numbers of rests decreased at 12 months in this genotype. These results demonstrate for the first time a functional role of the N-propeptide in regulating collagen fiber assembly and cell behavior and suggest that SPARC and the N-propeptide of collagen I have distinct activities in regulating collagen fiber assembly and fibroblast function.
authors.affiliation: Department of Oral Health Sciences, Medical University of South Carolina, Charleston, South Carolina, United States of America.
authors.forename: Emilie Moore
authors.identifier: http://orcid.org/0000-0001-6338-3617
authors.initials: EM
authors.lastname: Rosset
authors.affiliation: Department of Oral Health Sciences, Medical University of South Carolina, Charleston, South Carolina, United States of America.
authors.forename: Jessica
authors.initials: J
authors.lastname: Trombetta-eSilva
authors.affiliation: Department of Bioengineering, Clemson University, Clemson, South Carolina, United States of America.
authors.forename: Glenn
authors.initials: G
authors.lastname: Hepfer
authors.affiliation: Department of Oral Health Sciences, Medical University of South Carolina, Charleston, South Carolina, United States of America.|Department of Bioengineering, Clemson University, Clemson, South Carolina, United States of America.
authors.forename: Hai
authors.initials: H
authors.lastname: Yao
authors.affiliation: Department of Oral Health Sciences, Medical University of South Carolina, Charleston, South Carolina, United States of America.|Gazes Cardiac Research Institute, Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States of America.|The Ralph H. Johnson Department of Veteran's Affairs Medical Center, Charleston, South Carolina, United States of America.
authors.forename: Amy Dodd
authors.initials: AD
authors.lastname: Bradshaw
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000235:genetics / Q000502:physiology; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism*; D005091:Exons / Q000235:genetics; D005260:Female; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D005838:Genotype; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D015676:Osteonectin / Q000235:genetics / Q000378:metabolism*; D010513:Periodontal Ligament / Q000378:metabolism*
chemical_list: D024042:Collagen Type I; D015676:Osteonectin; C578250:SPARC protein, mouse