The alveolar epithelial type I-like cell line as an adequate model for leukocyte migration studies in vitro

A three-dimensional in vitro model to demonstrate the haptotactic effect of monocyte chemoattractant protein-1 on atherosclerosis-associated monocyte migration

Monocyte transendothelial migration is a multi-step process critical for the initiation and development of atherosclerosis. The chemokine monocyte chemoattractant protein-1 (MCP-1) is overexpressed during atheroma and its concentration gradients in the extracellular matrix (ECM) is critical for the transendothelial recruitment of monocytes. Based on prior observations, we hypothesize that both free and bound gradients of MCP-1 within the ECM are involved in directing monocyte migration. The interaction between a three-dimensional (3D), cell-free, collagen matrix and MCP-1; and its effect on monocyte migration was measured in this study. Our results showed such an interaction existed between MCP-1 and collagen, as 26% of the total MCP-1 added to the collagen matrix was bound to the matrix after extensive washes. We also characterized the collagen-MCP-1 interaction using biophysical techniques. The treatment of the collagen matrix with MCP-1 lead to increased monocyte migration, and this phenotype was abrogated by treating the matrix with an anti-MCP-1 antibody. Thus, our results indicate a binding interaction between MCP-1 and the collagen matrix, which could elicit a haptotactic effect on monocyte migration. A better understanding of such mechanisms controlling monocyte migration will help identify target cytokines and lead to the development of better anti-inflammatory therapeutic strategies.

Development of a mathematical model to describe the transport of monocyte chemoattractant protein-1 through a three-dimensional collagen matrix

INTRODUCTION

Monocyte chemoattractant protein-1 is a bioactive molecule that is expressed in significant amounts in all stages of atherosclerosis. The role of monocyte chemoattractant protein-1 in this disease is to recruit monocytes across the endothelium and into the arterial tissue. Eventually, the monocytes differentiate into cholesterol-engorged macrophages called "foam cells" that result in atherosclerotic plaque formation. The mechanism that monocyte chemoattractant protein-1 uses to mediate monocyte transendothelial migration is believed to be via its concentration gradient. However, the formation of the monocyte chemoattractant protein-1 concentration gradient in the extracellular matrix is still poorly understood.

METHODS

A three-dimensional in vitro vascular tissue model has been developed to study the cellular mechanisms involved in the early stages of atherosclerosis. In the present study, a mathematical model is used to determine the gradient of monocyte chemoattractant protein-1 in the collagen matrix of the three-dimensional in vitro vascular tissue model. Experiments were performed to investigate the stability of monocyte chemoattractant protein-1 and the interaction between monocyte chemoattractant protein-1 and the collagen matrix.

RESULTS AND CONCLUSIONS

Monocyte chemoattractant protein-1 is stable for at least 24 h under experimental conditions and monocyte chemoattractant protein-1 interacts with the collagen matrix. The diffusion coefficient for the transport of monocyte chemoattractant protein-1 in the collagen matrix and the rate constant for the binding of monocyte chemoattractant protein-1 to collagen were determined to be 0.108 mm(2) h(-1) and 0.858 h(-1), respectively. Numerical results from the model indicate that the concentration gradients of both soluble and matrix-bound (or static) monocyte chemoattractant protein-1 are formed inside the collagen matrix.