Researcher(s)
- Karl Matthew Ebron, , University of Delaware
Faculty Mentor(s)
- Justin Parreno, Biological Sciences, University of Delaware
Abstract
Background
Tendons connect muscle to bone that provide contractile force for movement. Tendinosis is the degenerative disease that occurs due to tendon overuse. Though overloaded, this condition leads to the understimulation of tenocytes. This under-stimulation leads to a change in matrix homeostasis: a downregulation of tenogenic mRNA levels and an increase in chondrogenic and matrix metalloprotease mRNA levels within the cell. Additionally, the tenocyte cytoskeleton is altered; filamentous (F-) actin depolymerizes leading to a greater proportion of globular (G-) to F-actin. It is unclear if and how F-actin depolymerization regulates gene expression. We hypothesize that F-actin depolymerization regulates gene expression, in part through myocardin-related transcription factor (MRTF), which has high affinity to G-actin molecules.
Methods and Results
Tenocytes were extracted from 8-10 week wild-type mouse tail fascicles and were cultured in vitro. After cells reached 70-90% confluency, we treated the cells with Latrunculin A, an agent that prevents tenocyte F-actin polymerization. This led to an overall decrease of F-actin. Additionally, exposure of tenocytes to latrunculin A results in nuclear export of MRTF. Concomitantly, latrunculin treatment decreases tenogenic mRNA levels and increases chondrogenic and matrix metalloproteinase mRNA levels. To determine how MRTF itself changed the gene expression, we exposed tenocytes to CCG1423, an agent that prevents the nuclear localization of MRTF within tenocytes. CCG1423 treatment decreased tenogenic but did not alter chondrogenic and matrix metalloproteinase mRNA levels. We verified that the decrease in tenogenic mRNA levels are consistent at the protein level; WES capillary electrophoresis demonstrates that CCG1423 decreases aSMA and Col1 protein levels.
Conclusions
In conclusion, actin depolymerization is a regulator of gene expression in tenocytes, partially through the regulation of MRTF. Attaining a deeper understanding of the regulation of tendinosis-like gene expression changes will allow for the creation of novel therapeutics designed to limit the development of tendon disease.