Stiffened fibre-like microenvironment based on patterned equidistant micropillars directs chondrocyte hypertrophy

Mengmeng Duan; Shuang Xia; Yang Liu; Xiaohua Pu; Yukun Chen; Yilin Zhou; Minglei Huang; Caixia Pi; Demao Zhang; Jing Xie

doi:10.1016/j.mtbio.2023.100682

Stiffened fibre-like microenvironment based on patterned equidistant micropillars directs chondrocyte hypertrophy

Mater Today Bio. 2023 May 27:20:100682. doi: 10.1016/j.mtbio.2023.100682. eCollection 2023 Jun.

Authors

Mengmeng Duan^{1

2}, Shuang Xia³, Yang Liu¹, Xiaohua Pu¹, Yukun Chen³, Yilin Zhou³, Minglei Huang¹, Caixia Pi¹, Demao Zhang^{1

4}, Jing Xie^{1

2}

Affiliations

¹ State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
² National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, China.
³ State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, 610065, China.
⁴ Institute of Biomedical Engineering, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu, China.

Abstract

Articular cartilage, composed of collagen type II as a major extracellular matrix and chondrocyte as a unique cell type, is a specialized connective tissue without blood vessels, lymphatic vessels and nerves. This distinctive characteristic of articular cartilage determines its very limited ability to repair when damaged. It is well known that physical microenvironmental signals regulate many cell behaviors such as cell morphology, adhesion, proliferation and cell communication even determine chondrocyte fate. Interestingly, with increasing age or progression of joint diseases such as osteoarthritis (OA), the major collagen fibrils in the extracellular matrix of articular cartilage become larger in diameter, leading to stiffening of articular tissue and reducing its resistance to external tension, which in turn aggravates joint damage or progression of joint diseases. Therefore, designing a physical microenvironment closer to the real tissue and thus obtaining data closer to the real cellular behaviour, and then revealing the biological mechanisms of chondrocytes in pathological states is of crucial importance for the treatment of OA disease. Here we fabricated micropillar substrates with the same topology but different stiffnesses to mimic the matrix stiffening that occurs in the transition from normal to diseased cartilage. It was first found that chondrocytes responded to stiffened micropillar substrates by showing a larger cell spreading area, a stronger enhancement of cytoskeleton rearrangement and more stability of focal adhesion plaques. The activation of Erk/MAPK signalling in chondrocytes was detected in response to the stiffened micropillar substrate. Interestingly, a larger nuclear spreading area of chondrocytes at the interface layer between the cells and top surfaces of micropillars was observed in response to the stiffened micropillar substrate. Finally, it was found that the stiffened micropillar substrate promoted chondrocyte hypertrophy. Taken together, these results revealed the cell responses of chondrocytes in terms of cell morphology, cytoskeleton, focal adhesion, nuclei and cell hypertrophy, and may be beneficial for understanding the cellular functional changes affected by the matrix stiffening that occurs during the transition from a normal state to a state of osteoarthritis.

Keywords: Chondrocyte hypertrophy; ECM stiffness; Mechanoreception; Mechanotransduction; Micropillar substrate.