Dylan Agha
Research Mentor(s): Rafael Correia Cavalcante
Department or Program: School of Dentistry
Authors: Dylan Agha, Rafael C. Cavalcante, Yuji Mishina
Session: Session 1: 12:00pm-12:50pm
Poster: 1
Abstract
The TMJ, or temporomandibular joint, is a joint hinge that connects the lower jaw to the temporal bone and possesses life-sustaining roles such as chewing, breathing, and talking. Temporomandibular disorders, or TMDs, are a wide set of disorders that target this joint and compromise the functions of the joint. TMDs often result in severe discomfort or pain for the patient, thus making it an important area of research. The Hedgehog Signaling, HH, Pathway is a developmental pathway that transmits information to embryonic cells for proper cell differentiation. Thus, HH could be vital for TMJ development and maintenance, and different genes in this pathway will be targeted/manipulated in this project.
In this project, mouse models based on the conditional knockout, cKO, of two genes in the HH pathway, SMO and EVC2/LBN are used to examine the morphology of the TMJ. The mice are also subject to either a Soft or Hard Diet (SD, HD), to test for the effect of mechanosensing, and as a result, examine whether the type of diet would affect the morphology. Conditional knockout, cKO, mice were developed for this project using Cre-Lox recombination, where certain desired genes were cut out by Cre recombinase (cre), specifically the wnt1cre enhancer in this project, marked at sites by the presence of the “flanking” flux(fx) in the gene, and only in cells that express the wnt1 gene. Control groups in this project were marked as fx/+, meaning only one strand of DNA had been modified and the mutants were fx/fx, meaning both strands had been edited. The samples were prepared for examination using a regular histology technique, where the samples were dehydrated, embedded in paraffin, and then sliced and stained. After Hematoxylin and Eosin staining, images of the TMJ were taken using a microscope to analyze the morphology.
In both HD and SD control mice, the TMJ is expected to be completely healthy, with no cartilage or disk degradation seen, since no expected genetic factor contributes to TMJ degradation. In EVC2 cKO mutant mice, the TMJ is expected to show signs of degradation since mutations in LBN/EVC2 have been shown to affect joints in humans, such as in Ellis van-Creveld Syndrome, which causes severe valgus deformity of the knee joint. In SMO cKO mutant mice, the TMJ should also show signs of damage/degradation, as studies on the knee joint have already concluded that deactivation of SMO can result in a phenotype with less cartilage between bones. The HD mutant mice (both SMO and EVC2) should exhibit worsened signs of TMJ damage compared to the SD mice due to the mechanical stress of a hard diet.
Not much is currently known about the effects of different genes in the HH pathway on the morphology and health of the TMJ, so this project aims to provide this insight. Also, the changes in the morphology of the TMJ depending on the type of diet aim to provide insight into the effects of mechanosensing on the TMJ.
