# The novel roles of tendon in TMJ condyle formation and remodeling

> **NIH NIH R03** · TEXAS A&M UNIVERSITY HEALTH SCIENCE CTR · 2021 · $150,000

## Abstract

Project Summary/Abstract
The Temporomandibular joint (TMJ) is considered to be the most complex and mysterious joint in the human
body. There is a disc between the temporal bone and TMJ condyle whose cell origin is unclear. Its displacement
leads to a specific TMJ disorder which causes TMJ pain and limited mouth opening. Second, there is an extra
fibrous layer on the surface of condylar articular cartilage followed by a prechondroblastic layer. The cell origin
and function for both are still unknown. Even more compelling, the mandible and TMJ condyle are commonly
injured. Up to 75% of the injured TMJ condyle is able to regenerate itself with no need for surgery in children,
while some patients developed into unilateral condylar hyperplasia for unknown reasons. Ironically, this joint has
received the least attention compared to other joints or the growth plate. The TMJ condyle has abundant
attachment sites of tendon, whose sole function has been thought to be transmitting muscle forces to stabilize
joints. Tendon is also known to undergo ectopic ossification in trauma or diseases, although it is largely unclear
if it has any direct contribution to normal skeleton formation. Considering all the information thus far, a series of
in vivo experiments have been performed to search for a potential role of tendon in TMJ condyle formation and
remodeling. The key findings are: 1) Scx+ (a tendon specific gene) cells in the fibrous layer directly contribute to
TMJ condyle articular cartilage growth by transdifferentiating into prechondroblasts and chondrocytes; 2) Scx+
cells in the area under the tendon attachment play a key role in condyle expansion from a carrot-like to a broccoli-
like shape by forming a fibrocartilage with a mixture of cartilage, bone and fibrous tissue 3) Scx+ cells directly
transdifferentiate into chondrocytes followed by bone cells during TMJ condylar remodeling and regeneration;
and 4) Scx+ cells are the major cell source for TMJ disc formation. Based on these findings, the central hypothesis
is that tendon cells, beyond their role in joint movement, function as key precursors for TMJ disc formation,
condyle growth, and joint remodeling. To test this central hypothesis, two highly related, yet independent Specific
Aims are proposed: 1) To define the overlooked role of tendon in TMJ formation and growth beyond moving
joints; and 2) To determine the vital role of tendon in TMJ remodeling via the regulation of mechanical force.
Upon completion of the proposed work, it is expected to demonstrate that 1) tendon cells directly contribute to
TMJ condyle chondrogenesis by forming fibrous-, prechondroblastic-, and chondrocyte-layers; 2) tendon cells
are vital sources for TMJ condyle expansion by forming fibrocartilage; 3) tendon cells play critical roles in TMJ
remodeling, which is mechanical force-dependent; and 4) tendon cells have a sole (or dominant) role of in TMJ
disc formation and remodeling. Completion of this project is expected to h...

## Key facts

- **NIH application ID:** 10131188
- **Project number:** 5R03DE029541-02
- **Recipient organization:** TEXAS A&M UNIVERSITY HEALTH SCIENCE CTR
- **Principal Investigator:** Yan Jing
- **Activity code:** R03 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $150,000
- **Award type:** 5
- **Project period:** 2020-04-01 → 2023-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10131188

## Citation

> US National Institutes of Health, RePORTER application 10131188, The novel roles of tendon in TMJ condyle formation and remodeling (5R03DE029541-02). Retrieved via AI Analytics 2026-06-01 from https://api.ai-analytics.org/grant/nih/10131188. Licensed CC0.

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