Substrate stiffness influences phenotype and function of human antigen-presenting dendritic cells

Svenja F B Mennens,Matteo Bolomini-Vittori,Ben Joosten,Alessandra Cambi,Jorieke Weiden,Koen Van Den Dries

doi:10.1038/s41598-017-17787-z

Abstract

Dendritic cells (DCs) are specialized immune cells that scan peripheral tissues for foreign material or aberrant cells and, upon recognition of such danger signals, travel to lymph nodes to activate T cells and evoke an immune response. For this, DCs travel large distances through the body, encountering a variety of microenvironments with different mechanical properties such as tissue stiffness. While immune-related pathological conditions such as fibrosis or cancer are associated with tissue stiffening, the role of tissue stiffness in regulating key functions of DCs has not been studied yet. Here, we investigated the effect of substrate stiffness on the phenotype and function of DCs by conditioning DCs on polyacrylamide substrates of 2, 12 and 50 kPa. Interestingly, we found that C-type lectin expression on immature DCs (iDCs) is regulated by substrate stiffness, resulting in differential antigen internalization. Furthermore, we show that substrate stiffness affects β2 integrin expression and podosome formation by iDCs. Finally, we demonstrate that substrate stiffness influences CD83 and CCR7 expression on mature DCs, the latter leading to altered chemokine-directed migration. Together, our results indicate that DC phenotype and function are affected by substrate stiffness, suggesting that tissue stiffness is an important determinant for modulating immune responses.

Highlights

Dendritic cells (DCs) are key regulators of both the innate and adaptive arms of the immune system
In the presence of CCL21, there was a striking difference in chemokine-directed migration. mature DCs (mDCs) conditioned on 12 kPa displayed a significantly lower transwell migration compared to mDCs conditioned on 2 kPa substrates, correlating positively with the CCR7 expression in these cells (Fig. 7b). mDCs conditioned on 12 kPa displayed a lower transwell migration compared to mDCs conditioned on 50 kPa, but these results were not significant. These results indicate that substrate stiffness regulates the expression of CCR7 in mDCs, thereby altering their capacity to migrate towards the chemokine CCL21, and suggest that tissue stiffness may influence the ability of mDCs to reach lymph vessels or lymph nodes
In Immature DCs (iDCs), C-type lectin receptors (CLRs) expression and CLR-mediated antigen internalization is decreased on 12 kPa, as well as β2 integrin cell surface expression and podosome formation

Summary

Introduction

Dendritic cells (DCs) are key regulators of both the innate and adaptive arms of the immune system They are considered the most potent antigen-presenting cells and, as such, are the main orchestrators of adaptive immune responses against invading pathogens or aberrant cells. The potential of these cells to control immune responses is well recognized and exploited in anti-cancer immunotherapies where autologous DCs are loaded with tumour antigens to instruct T cells to eradicate tumour cells. We demonstrate that substrate stiffness influences CD83 and CCR7 expression on mDCs, the latter leading to altered chemokine-directed migration Together, these results indicate that DCs can sense substrate stiffness during differentiation and maturation, leading to alterations in both iDC and mDC phenotype that can critically affect their function and eventual in vivo application

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