Premium
Expression of Extracellular Matrix Proteins in Human Periodontal Ligament Cells During Mineralization In Vitro
Author(s) -
Nohutcu Rahime M.,
McCauley Laurie K.,
Koh Amy J.,
Somerman Martha J.
Publication year - 1997
Publication title -
journal of periodontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.036
H-Index - 156
eISSN - 1943-3670
pISSN - 0022-3492
DOI - 10.1902/jop.1997.68.4.320
Subject(s) - cementoblast , bone sialoprotein , von kossa stain , periodontal fiber , osteonectin , osteopontin , chemistry , osteocalcin , osteoblast , ascorbic acid , cementum , alkaline phosphatase , type i collagen , population , microbiology and biotechnology , medicine , in vitro , endocrinology , biology , pathology , biochemistry , dentistry , dentin , food science , environmental health , enzyme
P eriodontal regeneration is a complex process that requires coordinated responses from several cell types within the periodontium. It is generally accepted that the periodontal ligament (PDL) has a heterogeneous cell population, where some of the cells may be capable of differentiating into either cementoblasts or osteoblasts. Thus, it has been hypothesized that PDL cells play a role in promoting periodontal regeneration. However, definitive evidence to support this concept is lacking. Previously, we reported that PDL cells induce biomineralization as determined by Von Kossa histochemistry and transmission electron microscopy. To further determine the osteoblast‐like properties of PDL cells, human PDL cells were exposed to dexamethasone (DEX) in order to promote an Osteoblast phenotype, and then cell activity monitored during mineral nodule formation in vitro. For mineralization studies, cells were cultured in DMEM containing 10% FBS and a) vehicle only; b) ascorbic acid (50 μg/ml) and β‐glycerophosphate (10 mM); or c) ascorbic acid, β‐glycerophosphate and DEX (100 nM) for 30 days. In addition, the effects of DEX on PDL cells in non‐mineralizing media were determined. Cells were stained weekly to evaluate mineral‐like nodules, using the Von Kossa method. Northern blot analyses for rnRNA steady state levels for several bone‐associated proteins, i.e., osteopontin (OPN), bone sialoprotein (BSP), alkaline Phosphatase (ALP), osteocalcin (OCN), α 2 (1)(type 1) collagen and osteonectin (ON), were performed. DNA levels were also detennined during the 30‐day minerahzation period. Under phase contrast microscopy, PDL cells in non‐rnineralizing media treated with DEX exhibited a more spindle‐shaped morphology when compared with similar cells not exposed to DEX. Mineralizing conditions were required to induce mineral nodule formation. However, in this situation, mineral induction was independent of DEX; and furthermore, DEX‐treated cells did not exhibit a different morphological pattern when compared with non‐DEX treated cells. Mineral‐like nodules were first seen at day 15, in concert with an increase followed by a decrease in expression of type I collagen and ON rnRNA in both DEX‐treated and non‐treated cultures. Using Northern blot analysis for detection of specific proteins, we found that PDL cells did not express OPN, BSP, OCN, or ALP under any of the conditions used in this study. DEX did not alter DNA content in the cultures during the mineralization period. These results confirm that human periodontal ligament cells can be induced to mineralize in vitro and indicate that dexamethasone does not significantly alter the extent and pattern of mineralization. J Periodontol 1997;68:320–327 .