Roles of mechanical force and CXCR1/CXCR2 in shear-stress-induced endothelial cell migration

Biomimetic Hydrogels in the Study of Cancer Mechanobiology: Overview, Biomedical Applications, and Future Perspectives

Hydrogels are biocompatible polymers that are tunable to the system under study, allowing them to be widely used in medicine, bioprinting, tissue engineering, and biomechanics. Hydrogels are used to mimic the three-dimensional microenvironment of tissues, which is essential to understanding cell–cell interactions and intracellular signaling pathways (e.g., proliferation, apoptosis, growth, and survival). Emerging evidence suggests that the malignant properties of cancer cells depend on mechanical cues that arise from changes in their microenvironment. These mechanobiological cues include stiffness, shear stress, and pressure, and have an impact on cancer proliferation and invasion. The hydrogels can be tuned to simulate these mechanobiological tissue properties. Although interest in and research on the biomedical applications of hydrogels has increased in the past 25 years, there is still much to learn about the development of biomimetic hydrogels and their potential applications in biomedical and clinical settings. This review highlights the application of hydrogels in developing pre-clinical cancer models and their potential for translation to human disease with a focus on reviewing the utility of such models in studying glioblastoma progression.

Fluid shear stress induces cell migration and invasion via activating autophagy in HepG2 cells

Fluid shear stress (FSS) regulates the metastasis of hepatocellular carcinoma (HCC). In the present study, we aimed to study the role of autophagy in HCC cells under FSS. The results showed that FSS upregulated the protein markers of autophagy, induced LC3B aggregation and formation of autophagosomes. Inhibition of integrin by Cliengitide (Cli) or inhibition of the microfilaments formation both inhibited the activation of autophagy in HepG2 under FSS. In addition, Cli inhibited the microfilaments formation and expressions of Rac1 and RhoA in HepG2 cells under FSS. Finally, inhibition of autophagy suppressed the cell migration and invasion in HepG2 under FSS. In conclusion, FSS induced autophagy to promote migration and invasion of HepG2 cells via integrin/cytoskeleton pathways.

MicroRNA-regulated pathways of flow-stimulated angiogenesis and vascular remodeling in vivo

BACKGROUND

Vascular shear stress promotes endothelial cell sprouting in vitro. The impact of hemodynamic forces on microRNA (miRNA) and gene expression within growing vascular networks in vivo, however, remain poorly investigated. Arteriovenous (AV) shunts are an established model for induction of neoangiogenesis in vivo and can serve as a tool for analysis of hemodynamic effects on miRNA and gene expression profiles over time.

METHODS

AV shunts were microsurgically created in rats and explanted on postoperative days 5, 10 and 15. Neoangiogenesis was confirmed by histologic analysis and micro-computed tomography. MiRNA and gene expression profiles were determined in tissue specimens from AV shunts by microarray analysis and quantitative real-time polymerase chain reaction and compared with sham-operated veins by bioinformatics analysis. Changes in protein expression within AV shunt endothelial cells were determined by immunohistochemistry.

RESULTS

Samples from AV shunts exhibited a strong overexpression of proangiogenic cytokines, oxygenation-associated genes (HIF1A, HMOX1), and angiopoetic growth factors. Significant inverse correlations of the expressions of miR-223-3p, miR-130b-3p, miR-19b-3p, miR-449a-5p, and miR-511-3p which were up-regulated in AV shunts, and miR-27b-3p, miR-10b-5p, let-7b-5p, and let-7c-5p, which were down-regulated in AV shunts, with their predicted interacting targets C-X-C chemokine receptor 2 (CXCR2), interleukin-1 alpha (IL1A), ephrin receptor kinase 2 (EPHA2), synaptojanin-2 binding protein (SYNJ2BP), forkhead box C1 (FOXC1) were present. CXCL2 and IL1A overexpression in AV shunt endothelium was confirmed at the protein level by immunohistochemistry.

CONCLUSIONS

Our data indicate that flow-stimulated angiogenesis is determined by an upregulation of cytokines, oxygenation associated genes and miRNA-dependent regulation of FOXC1, EPHA2 and SYNJ2BP.

Effects of dexamethasone on C6 cell proliferation, migration and invasion through the upregulation of AQP1

Dexamethasone (Dex) is commonly used to treat glioma; however, the mechanism underlying the action of Dex remains unclear. In the present study, the hypothesis that aquaporin-1 (AQP1) may participate in tumor cell proliferation, apoptosis, migration and invasion was tested using small interfering RNA (siRNA). The results of the current study indicated that Dex could inhibit the proliferation, in addition to promoting the migration, of C6 cells. Dex was indicated to promote the expression of AQP1. Downregulation of AQP1, achieved using siRNAs, demonstrated the inhibition of cell proliferation, promotion of cell migration and suppression of invasion; therefore, Dex was indicated to serve a role in these effects in the C6 cells, via the upregulation of AQP1. This demonstrated that AQP1 could be utilized as a novel therapeutic target, with the aim of inhibiting the proliferation and metastasis of gliomas.

IGFBP3 deposited in the human umbilical cord mesenchymal stem cell-secreted extracellular matrix promotes bone formation

The extracellular matrix (ECM) contains rich biological cues for cell recruitment, proliferationm, and even differentiation. The osteoinductive potential of scaffolds could be enhanced through human bone marrow mesenchymal stem cell (hBMSC) directly depositing ECM on surface of scaffolds. However, the role and mechanism of human umbilical cord mesenchymal stem cells (hUCMSC)-secreted ECM in bone formation remain unknown. We tested the osteoinductive properties of a hUCMSC-secreted ECM construct (hUCMSC-ECM) in a large femur defect of a severe combined immunodeficiency (SCID) mouse model. The hUCMSC-ECM improved the colonization of endogenous MSCs and bone regeneration, similar to the hUCMSC-seeded scaffold and superior to the scaffold substrate. Besides, the hUCMSC-ECM enhanced the promigratory molecular expressions of the homing cells, including CCR2 and TβRI. Furthermore, the hUCMSC-ECM increased the number of migrated MSCs by nearly 3.3 ± 0.1-fold, relative to the scaffold substrate. As the most abundant cytokine deposited in the hUCMSC-ECM, insulin-like growth factor binding protein 3 (IGFBP3) promoted hBMSC migration in the TβRI/II- and CCR2-dependent mechanisms. The hUCMSC-ECM integrating shRNA-mediated silencing of Igfbp3 that down-regulated IGFBP3 expression by approximately 60%, reduced the number of migrated hBMSCs by 47%. In vivo, the hUCMSC-ECM recruited 10-fold more endogenous MSCs to initiate bone formation compared to the scaffold substrate. The knock-down of Igfbp3 in the hUCMSC-ECM inhibited nearly 60% of MSC homing and bone regeneration capacity. This research demonstrates that IGFBP3 is an important MSC homing molecule and the therapeutic potential of hUCMSC-ECM in bone regeneration is enhanced by improving MSC homing in an IGFBP3-dependent mechanism.

Role of heparan sulfate in mediating CXCL8-induced endothelial cell migration

CXCL8 (Interleukin-8, IL-8) plays an important role in angiogenesis and wound healing by prompting endothelial cell migration. It has been suggested that heparan sulfate (HS) could provide binding sites on endothelial cells to retain and activate highly diffusible cytokines and inflammatory chemokines. In the present study, we aimed to test the hypothesis that HS is essential for enhancement of endothelial cell migration by CXCL8, and to explore the underlying mechanism by detecting the changes in expression and activity of Rho GTPases and in the organization of actin cytoskeleton after enzymatic removal of HS on human umbilical vein endothelial cells (HUVECs) by using heparinase III. Our results revealed that the wound healing induced by CXCL8 was greatly attenuated by removal of HS. The CXCL8-upregulated Rho GTPases including Cdc42, Rac1, and RhoA, and CXCL8-increased Rac1/Rho activity were suppressed by removal of HS. The polymerization and polarization of actin cytoskeleton, and the increasing of stress fibers induced by CXCL8 were also abolished by heparinase III. Taken together, our results demonstrated an essential role of HS in mediating CXCL8-induced endothelial cell migration, and highlighted the biological importance of the interaction between CXCL8 and heparan sulfate in wound healing.

Endothelial mechanosensors: the gatekeepers of vascular homeostasis and adaptation under mechanical stress

Endothelial cells (ECs) not only serve as a barrier between blood and extravascular space to modulate the exchange of fluid, macromolecules and cells, but also play a critical role in regulation of vascular homeostasis and adaptation under mechanical stimulus via intrinsic mechanotransduction. Recently, with the dissection of microdomains responsible for cellular responsiveness to mechanical stimulus, a lot of mechanosensing molecules (mechanosensors) and pathways have been identified in ECs. In addition, there is growing evidence that endothelial mechanosensors not only serve as key vascular gatekeepers, but also contribute to the pathogenesis of various vascular disorders. This review focuses on recent findings in endothelial mechanosensors in subcellular microdomains and their roles in regulation of physiological and pathological functions under mechanical stress.

Control of stem cell fate and function by engineering physical microenvironments

The phenotypic expression and function of stem cells are regulated by their integrated response to variable microenvironmental cues, including growth factors and cytokines, matrix-mediated signals, and cell–cell interactions. Recently, growing evidence suggests that matrix-mediated signals include mechanical stimuli such as strain, shear stress, substrate rigidity and topography, and these stimuli have a more profound impact on stem cell phenotypes than had previously been recognized, e.g. self-renewal and differentiation through the control of gene transcription and signaling pathways. Using a variety of cell culture models enabled by micro and nanoscale technologies, we are beginning to systematically and quantitatively investigate the integrated response of cells to combinations of relevant mechanobiological stimuli. This paper reviews recent advances in engineering physical stimuli for stem cell mechanobiology and discusses how micro- and nanoscale engineered platforms can be used to control stem cell niche environments and regulate stem cell fate and function.