Substrate Stiffness Mediate Inflammatory Response of Chondrocyte Stimulated by IL-1β

Abstract

Purposes Osteoarthritis (OA) is a degenerative joint disease that commonly occurs in middle-aged and elderly people. Mechanical microenvironment is one of the most significant factors in the development of OA. However, when the mechanical microenvironment changes, the inflammatory response of chondrocyte is elusive. Methods By adopting polydimethylsiloxane (PDMS) substrates with varying stiffness which can mimic the physiological stiffness of chondrocyte pericellular matrix (PCM), influences of co-regulated substrate stiffness and inflammatory factors interleukin-1β (IL-1β) on chondrocyte morphology, inflammatory mediators, and PCM remodeling protein expression are quantitatively analyzed. First, prostaglandin E2 (PGE2) and nitric oxide (NO) released in different stiffness substrates and IL-1β stimulated substrates with chondrocytes are detected. Second, the changes in different stiffness substrates and IL-1β stimulated substrates through immunofluorescence technique are observed and recorded. Third, the protein expressions of type Ⅱ collagen (COLII) and matrix metalloproteinase-13 (MMP13) are measured by Western blot assay. Findings The experimental results identify that substrate stiffness regulates the response of chondrocyte to inflammatory signals. Soft substrate dramatically enhances the release of PGE2 and NO (P<0.000 1), and MMP13 (P<0.05) expression, with IL-1β further enhances this regulation. In addition, stiff substrate significantly increases chondrocyte spreading area (P<0.000 1) and COLII expression level (P<0.01), IL-1β will further enhance this regulation. Conclusions This study will shed light into the mechanobiological mechanism of the chondrocyte sensing matrix mechanical microenvironment, and provide a reference for optimizing cell-inductive biomaterials.

Keywords

• chondrocyte
• substrate stiffness
• interleukin-1β
• pericellular matrix
• type ii collagen
• matrix metalloproteinase-13