# Triamcinolone Modulates Chondrocyte Biomechanics and Calcium-Dependent Mechanosensitivity

## TL;DR

Triamcinolone affects chondrocyte stiffness and calcium sensitivity, which may influence osteoarthritis progression.

## Contribution

This study reveals triamcinolone's dual effect on chondrocyte biomechanics and mechanosensitivity in osteoarthritis.

## Key findings

- TA increases chondrocyte stiffness via cytoskeletal reorganization and higher elastic modulus.
- TA enhances calcium influx during mechanical stimulation, indicating altered mechanosensitivity.
- TA reduces MMP1 gene expression, suggesting a protective effect on cartilage matrix.

## Abstract

Glucocorticoids are widely applied intra-articularly to alleviate inflammation and pain in osteoarthritis (OA). However, repeated administration and high local concentrations can lead to crystal deposition on the cartilage surface, contributing to chondrocyte damage and extracellular matrix (ECM) degradation, potentially accelerating OA progression. Calcium-dependent mechanosensors play a critical role in mediating catabolic responses in chondrocytes, but it remains unclear whether glucocorticoids affect chondrocyte mechanosensitivity or biomechanical properties. This in vitro study examined the dose-dependent effects of triamcinolone acetonide (TA) on chondrocyte biomechanics and mechanosensitivity. Primary human chondrocytes (N = 23) were cultured for one week with TA (2 µM–2 mM) or control medium. Cytoskeletal organization was visualized by F-actin staining (N = 6), and cellular elasticity (N = 5) was quantified via atomic force microscopy (AFM). Mechanotransduction was analyzed by Ca2+ imaging (Fluo-4 AM) upon AFM-based indentation (500 nN). Expression of matrix-related and mechanosensitive genes (N = 9) was assessed by qPCR. TA exposure induced a concentration-dependent reorganization of the F-actin cytoskeleton, pronounced at 0.2 mM, accompanied by a significant increase in the elastic modulus (p < 0.001). TA further augmented Ca2+ fluorescence intensity under basal conditions and during mechanical stimulation. Blocking cationic mechanosensitive channels with GsMtx4 (N = 3) markedly reduced the TA-evoked Ca2+ influx (p < 0.0001). Significant reduction in MMP1 was observed on the transcriptional level (N = 9) after TA-treatment (p < 0.05). In summary, TA enhances chondrocyte stiffness through cytoskeletal condensation and amplifies Ca2+-dependent mechanotransduction but reduces MMP1 expression, indicating a dual biomechanical response of chondrocytes to OA under exposure of potent corticosteroid.