TY - JOUR

T1 - Monitoring matrix remodeling in the cellular microenvironment using microrheology for complex cellular systems.

AU - Hafner, J

AU - Grijalva, D

AU - Ludwig-Husemann, A

AU - Bertels, S

AU - Bensinger, L

AU - Raic, A

AU - Gebauer, J

AU - Oelschlaeger, C

AU - Bastmeyer, M

AU - Bieback, K

AU - Lee-Thedieck, C

AU - Willenbacher, N

N1 - Funding Information: ALH, AR and CLT have received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No 757490) and from the BMBF NanoMatFutur program (FKZ 13N12968). MB and SB acknowledge support by the Helmholtz Association via the program “BioInterfaces in Technology and Medicine” (BIFTM); the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy – 2082/1 – 390761711, Cluster of Excellence “3D Matter Made to Order” (3DMM2O) and by the Carl Zeiss Foundation. Julian Gebauer acknowledges support by the International Research Training Group 1874/2 DIAMICOM and the Deutsche Diabetes Gesellschaft.

PY - 2020/7/15

Y1 - 2020/7/15

N2 - Multiple particle tracking (MPT) microrheology was employed for monitoring the development of extracellular matrix (ECM) mechanical properties in the direct microenvironment of living cells. A customized setup enabled us to overcome current limitations: (i) Continuous measurements were enabled using a cell culture chamber, with this, matrix remodeling by fibroblasts in the heterogeneous environment of macroporous scaffolds was monitored continuously. (ii) Employing tracer laden porous scaffolds for seeding human mesenchymal stem cells (hMSCs), we followed conventional differentiation protocols. Thus, we were, for the first time able to study the massive alterations in ECM elasticity during hMSC differentiation. (iii) MPT measurements in 2D cell cultures were enabled using a long distance objective. Exemplarily, local mechanical properties of the ECM in human umbilical vein endothelial cell (HUVEC) cultures, that naturally form 2D layers, were investigated scaffold-free. Using our advanced setup, we measured local, apparent elastic moduli G 0,app in a range between 0.08 and 60 Pa. For fibroblasts grown in collagen-based scaffolds, a continuous decrease of local matrix elasticity resulted during the first 10 hours after seeding. The osteogenic differentiation of hMSC cells cultivated in similar scaffolds, led to an increase of G 0,app by 100 %, whereas after adipogenic differentiation it was reduced by 80 %. The local elasticity of ECM that was newly secreted by HUVECs increased significantly upon addition of protease inhibitor and in high glucose conditions even a twofold increase in G 0,app was observed. The combination of these advanced methods opens up new avenues for a broad range of investigations regarding cell-matrix interactions and the propagation of ECM mechanical properties in complex biological systems. Statement of Significance: Cells sense the elasticity of their environment on a micrometer length scale. For studying the local elasticity of extracellular matrix (ECM) in the direct environment of living cells, we employed an advanced multipleparticle tracking microrheology setup. MPT is based on monitoring the Brownian motion oftracer particles, which is restricted by the surrounding network. Network elasticity can thusbe quantified. Overcoming current limitations, we realized continuous investigations of ECM elasticityduring fibroblast growth. Furthermore, MPT measurements of stem cell ECM showed ECMstiffening during osteogenic differentiation and softening during adipogenic differentiation.Finally, we characterized small amounts of delicate ECM newly secreted in scaffold-freecultures of endothelial cells, that naturally form 2D layers.

AB - Multiple particle tracking (MPT) microrheology was employed for monitoring the development of extracellular matrix (ECM) mechanical properties in the direct microenvironment of living cells. A customized setup enabled us to overcome current limitations: (i) Continuous measurements were enabled using a cell culture chamber, with this, matrix remodeling by fibroblasts in the heterogeneous environment of macroporous scaffolds was monitored continuously. (ii) Employing tracer laden porous scaffolds for seeding human mesenchymal stem cells (hMSCs), we followed conventional differentiation protocols. Thus, we were, for the first time able to study the massive alterations in ECM elasticity during hMSC differentiation. (iii) MPT measurements in 2D cell cultures were enabled using a long distance objective. Exemplarily, local mechanical properties of the ECM in human umbilical vein endothelial cell (HUVEC) cultures, that naturally form 2D layers, were investigated scaffold-free. Using our advanced setup, we measured local, apparent elastic moduli G 0,app in a range between 0.08 and 60 Pa. For fibroblasts grown in collagen-based scaffolds, a continuous decrease of local matrix elasticity resulted during the first 10 hours after seeding. The osteogenic differentiation of hMSC cells cultivated in similar scaffolds, led to an increase of G 0,app by 100 %, whereas after adipogenic differentiation it was reduced by 80 %. The local elasticity of ECM that was newly secreted by HUVECs increased significantly upon addition of protease inhibitor and in high glucose conditions even a twofold increase in G 0,app was observed. The combination of these advanced methods opens up new avenues for a broad range of investigations regarding cell-matrix interactions and the propagation of ECM mechanical properties in complex biological systems. Statement of Significance: Cells sense the elasticity of their environment on a micrometer length scale. For studying the local elasticity of extracellular matrix (ECM) in the direct environment of living cells, we employed an advanced multipleparticle tracking microrheology setup. MPT is based on monitoring the Brownian motion oftracer particles, which is restricted by the surrounding network. Network elasticity can thusbe quantified. Overcoming current limitations, we realized continuous investigations of ECM elasticityduring fibroblast growth. Furthermore, MPT measurements of stem cell ECM showed ECMstiffening during osteogenic differentiation and softening during adipogenic differentiation.Finally, we characterized small amounts of delicate ECM newly secreted in scaffold-freecultures of endothelial cells, that naturally form 2D layers.

KW - ECM elasticity

KW - HUVECs

KW - MMP inhibitor

KW - Mesenchymal stem cell differentiation

KW - Micromechanics

KW - Multiple particle tracking

UR - http://www.scopus.com/inward/record.url?scp=85085596890&partnerID=8YFLogxK

U2 - 10.1016/j.actbio.2020.04.053

DO - 10.1016/j.actbio.2020.04.053

M3 - Article

C2 - 32434077

VL - 111

SP - 254

EP - 266

JO - Acta biomaterialia

JF - Acta biomaterialia

SN - 1742-7061

ER -