Effects of two wattages of low-level laser therapy on orthodontic tooth movement.

INTRODUCTION: Mixed outcomes have been found in animal and clinical studies with regard to the use of low-level laser therapy (LLLT) as a modality to accelerate orthodontic tooth movement (OTM). One major reason for the variable findings is the different methodologies and protocols for laser therapy use. OBJECTIVE: The aim of this study was to determine whether orthodontically moved molars exposed to two different wattages at the same energy density of LLLT exhibited differences in the amount of tooth movement and molecular and histological changes in the adjacent periodontal areas. METHODS: An orthodontic force was applied to rat upper first molars exposed to 500mW (EX-500) and 1000mW (EX-1000) of laser application, with a control group (CT) with no laser application. Gene expression in the periodontal ligament (PDL) and histology of the palatal gingiva of the molars were analyzed. RESULTS: There was a statistically significant difference for OTM between EX-500 but not between EX-1000 and CT groups. RANKL and MMP-13 expression levels in the PDL of orthodontically moved molars, however, were increased significantly in laser-exposed groups compared to CT. Early signs of dysplasia were observed in over half of the animals in the EX-1000 group. CONCLUSIONS: Our results provide evidence for molecular changes and the potential dysplastic effects of laser on the surrounding soft tissues. Further studies are needed to better identify an optimum laser protocol to maximize the desired effect.

FLRT2 interacts with fibronectin in the ATDC5 chondroprogenitor cells.

Expression studies have implicated FLRT2 in cranial neural crest cell migration and prechondrogenic cell condensation during craniofacial skeletogenesis. We aimed to determine whether FLRT2 was involved in mediating cell-matrix interactions in the ATDC5 chondroprogenitor cell line. Immunolocalization experiments of ATDC5 cells revealed that FLRT2 was present on the cell membrane as well as extracellularly, where it colocalized with Fibronectin (Fn). After cell extraction of the matrix, FLRT2 was identified in the ATDC5-derived extracellular matrix (ECM) and was further found to be associated with Fn-coated beads in cell cultures. Blockage of Fn fibril formation via a blocking peptide resulted in a concomitant decrease in extracellular FLRT2 accumulation. Over a 7-day period following the replenishment of the Fn blocking peptide to the cultures, there was a partial rebound in Fn fibril formation that was accompanied by a concomitant reappearance of FLRT2 co-expression. Co-immunoprecipitation confirmed that FLRT2 and Fn interacted, either directly or indirectly. Immunoprecipitation and Western blot analyses with antibodies recognizing epitopes located on the extra- and intracellular domains of FLRT2 further revealed the presence of different sized bands, suggesting that FLRT2 may exist in both membrane-bound and shed forms. Our data therefore provide evidence that FLRT2 and/or its cleavage products may be cooperating with Fn and other ECM proteins to regulate critical cellular events. Further studies will be necessary in delineate more precisely the roles of FLRT2 in mediating cell- and cell-matrix interactions during normal development.

PACAP receptor (PAC1-R) expression in rat and rhesus monkey thymus.

The expression of PACAP receptor (PAC1-R) was investigated in the thymus of rats and rhesus monkeys. In the rat thymus, PAC1-R positive cells were found in the intermediate type of thymic epithelial cells of the medulla. PAC1-R-positive cells were also seen in the thymic medulla of the rhesus monkey. The thymus showed unusual structures in some rhesus monkey dams (F0) and offspring (F1) exposed to 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD). Additionally, in these rhesus monkeys, PAC1-R expression was different from that in the control thymus.

Semiquantitative morphological analysis of stromal cells in the irradiated and recovering rat thymus.

To understand the roles of thymic stromal cells in T-lymphocyte development, we semiquantitatively analysed rat thymi recovering from irradiation (6 Gy), using a transmission electron microscope. The most striking findings were that the percentage of subcapsular epithelial cells significantly increased in the cortex on day 3 after irradiation compared with the control; the percentage of intermediate epithelial cells significantly increased in the cortex on days 3 and 5 after irradiation and in the medulla on days 5 and 7 compared with the control; the interdigitating cells disappeared from the medulla by day 7 after irradiation and reappeared on day 9. The present data thus reveal that during recovery after irradiation (6 Gy), marked changes occur in the relative proportions of different epithelial cell subtypes in the cortex and medulla of the rat thymus. In addition, the percentages of macrophages and interdigitating cells also changed during the recovery. These changes, which may be associated with the abrupt proliferation of thymocytes after irradiation, should shed light on the significance of stromal cells in the T cell development.