Biology subjects

Harmsen, M. C.

Publications and source records attributed to Harmsen, M. C..

4 recordsLinked to original sources

bioRxiv2025

Fibroblast alignment is governed by stiffness interfaces in hydrogels.

Transitions in mechanical properties between different tissue scaffolds, such as extracellular matrices (ECMs), are common in the human body and influence cellular orientation. For example, in teeth, the abrupt transition between soft ([~]5 kPa) dental pulp and stiff (>100 kPa) dentin directs the alignment of odontoblasts. In this study, hydrogels, with defined mechanical transitions were used to evaluate the phenotypic response of fibroblasts to either a soft/soft (3 kPa/3 kPa) or soft/stiff (3 kPa/200 kPa) interface. Near the soft/soft interface fibroblasts aligned in a more parallel fashion to the interface (11{degrees} angle to the interface), compared to the more perpendicular fashion (69{degrees} angle to the interface) observed at the soft-stiff interface. Notably, regions of alignment also showed an increased proportion of alpha smooth muscle actin (SMA)-positive cells, indicating myofibroblast differentiation in response to the mechanical transition. These findings demonstrate that modifying a biomaterial by introducing an interface alters the bioactivity of responding cells solely through mechanical mechanisms, without any change to the cells biochemical environment. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=147 HEIGHT=200 SRC="FIGDIR/small/695439v1_ufig1.gif" ALT="Figure 1000"> View larger version (42K): org.highwire.dtl.DTLVardef@d0ca04org.highwire.dtl.DTLVardef@17ee49forg.highwire.dtl.DTLVardef@1d389a5org.highwire.dtl.DTLVardef@f1b2a0_HPS_FORMAT_FIGEXP M_FIG C_FIG Schematic summary showing interface-induced fibroblast orientation and variety in phenotypic expression. On the bottom left the perpendicular orientation of fibroblast (skin tone) and myofibroblast (pink) on a soft/soft (3kPa/3kPa) GelMA hydrogel interface and on the right side the parallel orientation near a soft/stiff (3kPa/200kPa) GelMA hydrogel interface with greater collagen deposition, depicted by purple halos.

bioengineering↗

bioRxiv2025

Modelling cigarette smoke-induced lung vascular dysfunction using an alveolus-on-chip

The alveolus is central to gas exchange in the lung, and alveolar damage is a characteristics of a variety of lung diseases. Understanding alveolar microvascular dynamics and epithelial-endothelial interactions is essential for accurately modeling alveolar physiology and its dysfunction in lung diseases such as Chronic Obstructive Pulmonary Disease (COPD), pulmonary fibrosis and acute respiratory distress syndrome (ARDS). In this study, we present an open-top, membrane-free alveolus-on-chip platform incorporating self-assembled, perfusable 3D vascular networks by primary human lung endothelial cells and pericytes, co-cultured with alveolar epithelial type 2 (AEC2) cells. These vascular networks were developed within 6 days under continuous flow and remained stable for at least 12 days. The inclusion of pericytes supported capillary-like vessel formation and increased gene expression of EDNRB1, a gene enriched in alveolar microvascular endothelial cells. Furthermore, CD31 gene expression was higher in 3D endothelial networks compared to 2D endothelial monolayers, suggesting increased cell-cell adhesion. Monocytes could be successfully perfused through the networks, expanding the platforms potential for studying immune interactions in lung disorders. Culturing AEC2 monolayers directly on the vascularized hydrogel enabled physiologically relevant cell-cell interactions without artificial membranes, while maintaining air-liquid interface conditions. Importantly, exposure of the AEC2 layer to whole cigarette smoke (WCS) led to complete disintegration of the underlying vascular network, an effect not observed in the absence of AEC2. This chip model provides a human-relevant system for investigating vascular-epithelial crosstalk in the alveolus, smoke-induced lung injury, and immune recruitment, offering a valuable platform for future disease modeling and drug testing applications.

bioengineering↗

bioRxiv2025

Contrasting responses of control and fibrotic lung fibroblasts to fibrotic stimuli: the role of osteoprotegerin in extracellular matrix remodeling

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease characterized by dysregulated wound healing, leading to excessive production of extracellular matrix (ECM) proteins, particularly collagen, by activated fibroblasts. Osteoprotegerin (OPG), a soluble protein associated with ECM remodeling in bone, has been found in higher levels in serum and lung tissue of IPF patients compared to controls. However, whether OPG is associated with ECM remodeling by fibroblasts in lung fibrosis remains poorly understood. In this study we assessed differences in OPG levels in ECM-derived hydrogels from non-disease controls and patients with IPF encapsulated with primary human lung fibroblasts from control and patients with IPF (7 days). OPG levels were assessed in a collected culture medium and stained lung tissue sections, and related to biomechanical properties. Fibrotic human lung fibroblasts secreted and deposited more OPG compared to controls, which was observed in both non-diseased and IPF ECM hydrogels. OPG levels correlated significantly with matrix stiffness and collagen fiber structural properties, but only in IPF hydrogels, independent of fibroblast source. Strikingly, we also observed opposite correlations for control and fibrotic fibroblasts in fibrotic hydrogels. Control fibroblasts within a fibrotic microenvironment, secreted less OPG when hydrogel stiffness increased and deposited more OPG when collagen fibers were more aligned. Interestingly, fibrotic fibroblasts secreted more OPG when collagen fiber length increased and when collagen fiber curvature increased. Overall, our findings suggest that control and fibrotic lung fibroblasts exhibited opposite behavior with respect to OPG and ECM remodeling under fibrotic conditions and this may have consequences for matrix stiffness

cell biology↗

bioRxiv2022

An in vitro model of fibrosis using crosslinked native extracellular matrix-derived hydrogels to modulate biomechanics without changing composition

Extracellular matrix (ECM) is a dynamic network of proteins, proteoglycans and glycosaminoglycans, providing structure to the tissue and biochemical and biomechanical instructions to the resident cells. In fibrosis, the composition and the organization of the ECM are altered, and these changes influence cellular behaviour. Biochemical (i. e. protein composition) and biomechanical changes in ECM take place simultaneously in vivo. Investigating these changes individually in vitro to examine their (patho)physiological effects has been difficult. In this study, we generated an in vitro model to reflect the altered mechanics of a fibrotic microenvironment through applying fibre crosslinking via ruthenium/sodium persulfate crosslinking on native lung ECM-derived hydrogels. Crosslinking of the hydrogels without changing the biochemical composition of the ECM resulted in increased stiffness and decreased viscoelastic stress relaxation. The altered stress relaxation behaviour was explained using a generalized Maxwell model. Fibre analysis of the hydrogels showed that crosslinked hydrogels had a higher percentage of matrix with a high density and a shorter average fibre length. Fibroblasts seeded on ruthenium-crosslinked lung ECM-derived hydrogels showed myofibroblastic differentiation with a loss of spindle-like morphology together with greater -smooth muscle actin (-SMA) expression, increased nuclear area and circularity without any decrease in the viability, compared with the fibroblasts seeded on the native lung-derived ECM hydrogels. In summary, ruthenium crosslinking of native ECM-derived hydrogels provides an exciting opportunity to alter the biomechanical properties of the ECM-derived hydrogels while maintaining the protein composition of the ECM to study the influence of mechanics during fibrotic lung diseases.

pathology↗