More Like this

1. Variations in mechanical stiffness alter microvascular sprouting and stability in a PEG hydrogel model of idiopathic pulmonary fibrosis

   https://doi.org/10.1111/micc.12817  

   Leonard‐Duke, Julie ; Bruce, Anthony C. ; Peirce, Shayn M. ; Taite, Lakeshia J. ( May 2023 , Microcirculation)

   Microvascular remodeling is governed by biomechanical and biochemical cues which are dysregulated in idiopathic pulmonary fibrosis. Understanding how these cues impact endothelial cell‐pericyte interactions necessitates a model system in which both variables can be independently and reproducibly modulated. In this study we develop a tunable hydrogel‐based angiogenesis assay to study how varying angiogenic growth factors and environmental stiffness affect sprouting and vessel organization.

   Lungs harvested from mice were cut into 1 mm long segments then cultured on hydrogels having one of seven possible stiffness and growth factor combinations. Time course, brightfield, and immunofluorescence imaging were used to observe and quantify sprout formation.

   Our assay was able to support angiogenesis in a comparable manner to Matrigel in soft 2 kPa gels while enabling tunability to study the effects of stiffness on sprout formation. Matrigel and 2 kPa groups contained significantly more samples with sprouts when compared to the stiffer 10 and 20 kPa gels. Growth factor treatment did not have as obvious an effect, although the 20 kPa PDGF + FGF‐treated group had significantly longer vessels than the vascular endothelial growth factor‐treated group.

   We have developed a novel, tunable hydrogel assay for the creation of lung explant vessel organoids which can be modulated to study the impact of specific environmental cues on vessel formation and maturation.

    

   more » « less
2. Agent‐based computational model of retinal angiogenesis simulates microvascular network morphology as a function of pericyte coverage

   https://doi.org/10.1111/micc.12393  

   Walpole, Joseph ; Mac Gabhann, Feilim ; Peirce, Shayn M. ; Chappell, John C. ( November 2017 , Microcirculation)

   Define a role for perivascular cells during developmental retinal angiogenesis in the context of EC Notch1‐DLL4 signaling at the multicellular network level.

   The retinal vasculature is highly sensitive to growth factor‐mediated intercellular signaling. Although EC signaling has been explored in detail, it remains unclear how PC function to modulate these signals that lead to a diverse set of vascular network patterns in health and disease. We have developed an ABM of retinal angiogenesis that incorporates both ECs and PCs to investigate the formation of vascular network patterns as a function of pericyte coverage. We use our model to test the hypothesis that PC modulate Notch1‐DLL4 signaling in endothelial cell‐endothelial cell interactions.

   Agent‐based model (ABM) simulations that include PCs more accurately predict experimentally observed vascular network morphologies than simulations that lack PCs, suggesting that PCs may influence sprouting behaviors through physical blockade of endothelial intercellular connections.

   This study supports a role for PCs as a physical buffer to signal propagation during vascular network formation—a barrier that may be important for generating healthy microvascular network patterns.

    

   more » « less
3. Substrate Stiffness and Stretch Regulate Profibrotic Mechanosignaling in Pulmonary Arterial Adventitial Fibroblasts

   https://doi.org/10.3390/cells10051000  

   Wang, Ariel ; Cao, Shulin ; Stowe, Jennifer C. ; Valdez-Jasso, Daniela ( May 2021 , Cells)

   Pulmonary arterial adventitial fibroblasts (PAAFs) are important regulators of fibrotic vascular remodeling during the progression of pulmonary arterial hypertension (PAH), a disease that currently has no effective anti-fibrotic treatments. We conducted in-vitro experiments in PAAFs cultured on hydrogels attached to custom-made equibiaxial stretchers at 10% stretch and substrate stiffnesses representing the mechanical conditions of mild and severe stages of PAH. The expression of collagens α(1)I and α(1)III and elastin messenger RNAs (Col1a1, Col3a1, Eln) were upregulated by increased stretch and substrate stiffness, while lysyl oxidase-like 1 and α-smooth muscle actin messenger RNAs (Loxl1, Acta2) were only significantly upregulated when the cells were grown on matrices with an elevated stiffness representative of mild PAH but not on a stiffness representative of severe PAH. Fibronectin messenger RNA (Fn1) levels were significantly induced by increased substrate stiffness and transiently upregulated by stretch at 4 h, but was not significantly altered by stretch at 24 h. We modified our published computational network model of the signaling pathways that regulate profibrotic gene expression in PAAFs to allow for differential regulation of mechanically-sensitive nodes by stretch and stiffness. When the model was modified so that stiffness activated integrin β3, the Macrophage Stimulating 1 or 2 (MST1\2) kinases, angiotensin II (Ang II), transforming growth factor-β (TGF-β), and syndecan-4, and stretch-regulated integrin β3, MST1\2, Ang II, and the transient receptor potential (TRP) channel, the model correctly predicted the upregulation of all six genes by increased stiffness and the observed responses to stretch in five out of six genes, although it could not replicate the non-monotonic effects of stiffness on Loxl1 and Acta2 expression. Blocking Ang II Receptor Type 1 (AT1R) with losartan in-vitro uncovered an interaction between the effects of stretch and stiffness and angiotensin-independent activation of Fn1 expression by stretch in PAAFs grown on 3-kPa matrices. This novel combination of in-vitro and in-silico models of PAAF profibrotic cell signaling in response to altered mechanical conditions may help identify regulators of vascular adventitial remodeling due to changes in stretch and matrix stiffness that occur during the progression of PAH in-vivo. 

   more » « less
4. Elastin‐like protein hydrogels with controllable stress relaxation rate and stiffness modulate endothelial cell function

   https://doi.org/10.1002/jbm.a.37520  

   Shayan, Mahdis ; Huang, Michelle S. ; Navarro, Renato ; Chiang, Gladys ; Hu, Caroline ; Oropeza, Beu P. ; Johansson, Patrik K. ; Suhar, Riley A. ; Foster, Abbygail A. ; LeSavage, Bauer L. ; et al ( March 2023 , Journal of Biomedical Materials Research Part A)

   Mechanical cues from the extracellular matrix (ECM) regulate vascular endothelial cell (EC) morphology and function. Since naturally derived ECMs are viscoelastic, cells respond to viscoelastic matrices that exhibit stress relaxation, in which a cell‐applied force results in matrix remodeling. To decouple the effects of stress relaxation rate from substrate stiffness on EC behavior, we engineered elastin‐like protein (ELP) hydrogels in which dynamic covalent chemistry (DCC) was used to crosslink hydrazine‐modified ELP (ELP‐HYD) and aldehyde/benzaldehyde‐modified polyethylene glycol (PEG‐ALD/PEG‐BZA). The reversible DCC crosslinks in ELP‐PEG hydrogels create a matrix with independently tunable stiffness and stress relaxation rate. By formulating fast‐relaxing or slow‐relaxing hydrogels with a range of stiffness (500–3300 Pa), we examined the effect of these mechanical properties on EC spreading, proliferation, vascular sprouting, and vascularization. The results show that both stress relaxation rate and stiffness modulate endothelial spreading on two‐dimensional substrates, on which ECs exhibited greater cell spreading on fast‐relaxing hydrogels up through 3 days, compared with slow‐relaxing hydrogels at the same stiffness. In three‐dimensional hydrogels encapsulating ECs and fibroblasts in coculture, the fast‐relaxing, low‐stiffness hydrogels produced the widest vascular sprouts, a measure of vessel maturity. This finding was validated in a murine subcutaneous implantation model, in which the fast‐relaxing, low‐stiffness hydrogel produced significantly more vascularization compared with the slow‐relaxing, low‐stiffness hydrogel. Together, these results suggest that both stress relaxation rate and stiffness modulate endothelial behavior, and that the fast‐relaxing, low‐stiffness hydrogels supported the highest capillary density in vivo.

    

   more » « less
5. Guiding Cell Network Assembly using Shape‐Morphing Hydrogels

   https://doi.org/10.1002/adma.202002195  

   Viola, John M. ; Porter, Catherine M. ; Gupta, Ananya ; Alibekova, Mariia ; Prahl, Louis S. ; Hughes, Alex J. ( June 2020 , Advanced Materials)

   Forces and relative movement between cells and extracellular matrix (ECM) are crucial to the self‐organization of tissues during development. However, the spatial range over which these dynamics can be controlled in engineering approaches is limited, impeding progress toward the construction of large, structurally mature tissues. Herein, shape‐morphing materials called “kinomorphs” that rationally control the shape and size of multicellular networks are described. Kinomorphs are sheets of ECM that change their shape, size, and density depending on patterns of cell contractility within them. It is shown that these changes can manipulate structure‐forming behaviors of epithelial cells in many spatial locations at once. Kinomorphs are built using a new photolithographic technology to pattern single cells into ECM sheets that are >10× larger than previously described. These patterns are designed to partially mimic the branch geometry of the embryonic kidney epithelial network. Origami‐inspired simulations are then used to predict changes in kinomorph shapes. Last, kinomorph dynamics are shown to provide a centimeter‐scale program that sets specific spatial locations in which ≈50 µm‐diameter epithelial tubules form by cell coalescence and structural maturation. The kinomorphs may significantly advance organ‐scale tissue construction by extending the spatial range of cell self‐organization in emerging model systems such as organoids.

    

   more » « less