Degradation of extracellular matrix regulates osteoblast migration: A microfluidic-based study

Abstract

Bone regeneration is strongly dependent on the capacity of cells to move in a 3D microenvironment, where a large cascade of signals is activated. To improve the understanding of this complex process and to advance in the knowledge of the role of each specific signal, it is fundamental to analyze the impact of each factor independently. Microfluidic-based cell culture is an appropriate technology to achieve this objective, because it allows recreating realistic 3D local microenvironments by taking into account the extracellular matrix, cells and chemical gradients in an independent or combined scenario. The main aim of this work is to analyze the impact of extracellular matrix properties and growth factor gradients on 3D osteoblast movement, as well as the role of cell matrix degradation. For that, we used collagen-based hydrogels, with and without crosslinkers, under different chemical gradients, and eventually inhibiting metalloproteinases to tweak matrix degradation. We found that osteoblast's 3D migratory patterns were affected by the hydrogel properties and the PDGF-BB gradient, although the strongest regulatory factor was determined by the ability of cells to remodel the matrix.

Primary Human Osteoblasts Cultured in a 3D Microenvironment Create a Unique Representative Model of Their Differentiation Into Osteocytes

“…Bone models on a chip were developed in recent years to reveal different elements of bone biology, each one based on a critical advantage of microengineered devices over traditional 2D or 3D macroscale in vitro systems. For example, the use of optically transparent materials allowed the monitoring of osteoblast motility in a confined 3D environment (Movilla et al, 2018). The results of this study elucidated the effect of ECM degradation and its architecture on osteoblast migration, by applying growth factor gradients or interstitial fluid flow (Del Amo et al, 2018).…”

Matrix architecture plays a pivotal role in 3D osteoblast migration: The effect of interstitial fluid flow

“…Collagen hydrogel type I (rat tail, BD Biosciences) was used at a final concentration of 4 mg/ml with DPBS 10X (Lonza), adjusting the pH to 7.4 with 0.5 M NaOH. In hydrogels crosslinked with transglutaminase 2 (rhTGM2, R&D Systems), this enzyme was added at the concentration of 25 µg/ml [35]. The polymerization of hydrogels and cell maintenance were performed in an incubator at 37°C and 5% CO2 under humidity conditions, avoiding prepolymerization of the hydrogels.…”

“…In addition, 3D experimental assays revealed a low chemotactic effect of growth factors on osteoblasts in terms of migration compared to the response of other cell types under similar conditions [35,36]. For instance, while fibroblasts exhibit directional migration under PDGF-BB gradients [37], osteoblast migration seems to be regulated by the ability of cells to remodel the matrix [35].…”

“…Other micro environmental factors, such as transforming growth factor beta (TGF-β) superfamily, bone morphogenetic proteins (BMPs), and interleukins (IL-6, IL17F, and IL1β), can also play a regulatory role in bone fracture healing [11,33,34]. In addition, 3D experimental assays revealed a low chemotactic effect of growth factors on osteoblasts in terms of migration compared to the response of other cell types under similar conditions [35,36]. For instance, while fibroblasts exhibit directional migration under PDGF-BB gradients [37], osteoblast migration seems to be regulated by the ability of cells to remodel the matrix [35].…”

Inhibition of Osteoblast Proliferation and Migration by Exogenous and Endogenous Formaldehyde

“…Osteoblast growth and migration are essential for not only bone metabolism, including bone remodeling and responses to mechanical loading, but also bone pathological processes including bone repair after fractures and during osteoporosis [1][2][3].…”