Fluid shear promotes chondrosarcoma cell invasion by activating matrix metalloproteinase 12 via IGF-2 and VEGF signaling pathways

Distinguishing high-metastasis-potential circulating tumor cells through fluidic shear stress in a bloodstream-like microfluidic circulatory system

Circulating tumor cells (CTCs) play a critical role as initiators in tumor metastasis, which unlocks an irreversible process of cancer progression. Regarding the fluid environment of intravascular CTCs, a comprehensive understanding of the impact of hemodynamic shear stress on CTCs is of profound significance but remains vague. Here, we report a microfluidic circulatory system that can emulate the CTC microenvironment to research the responses of typical liver cancer cells to varying levels of fluid shear stress (FSS). We observe that HepG2 cells surviving FSS exhibit a marked overexpression of TLR4 and TPPP3, which are shown to be associated with the colony formation, migration, and anti-apoptosis abilities of HepG2. Furthermore, overexpression of these two genes in another liver cancer cell line with normally low TLR4 and TPPP3 expression, SK-Hep-1 cells, by lentivirus-mediated transfection also confirms the critical role of TLR4 and TPPP3 in improving colony formation, migration, and survival capability under a fluid environment. Interestingly, in vivo experiments show SK-Hep-1 cells, overexpressed with these genes, have enhanced metastatic potential to the liver and lungs in mouse models via tail vein injection. Mechanistically, TLR4 and TPPP3 upregulated by FSS may increase FSS-mediated cell survival and metastasis through the p53-Bax signaling pathway. Moreover, elevated levels of these genes correlate with poorer overall survival in liver cancer patients, suggesting that our findings could offer new therapeutic strategies for early cancer diagnosis and targeted treatment development.

PRISMA-the 100 most-cited articles on chondrosarcoma recurrence: A bibliometric analysis

BACKGROUND

Chondrosarcoma (CHS) is highly prone to recurrence and has become the most common malignant bone tumor in adults. The authors aim to identify and analyze the top 100 most-cited articles in this field, enabling researchers to quickly grasp the research focus and progress in the area of chondrosarcoma recurrence.

METHODS

A search in the Web of Science database yielded a total of 305 articles related to CHS recurrence between 2013 and 2022. Filtering was done based on the titles and abstracts of the articles in the list, and the top 100 most-cited articles were selected. The following information were analyzed using bibliometric methods: article title, first author, year of publication, journal of publication, total citations, country, institution, and keywords.

RESULTS

Among the selected 100 articles, the most frequently cited one has 224 citations. The most commonly appearing journals, institutions, and countries are as follows: "Clinical Orthopaedics Related Research" (5 times); Fudan University, University of Texas System, and Royal Orthopaedic Hospital (4 times each), with China and the USA cited the most (21 times each). The year 2018 is the most productive year (17 articles). About 97 first authors contributed one article each, and 3 had 2 articles each. Among all 229 keywords, the top 3 in frequency are CHS (20%), recurrence (4%), and surgery (3%). Twenty article topics are related to surgical treatment.

CONCLUSION

Research on CHS recurrence is citation-rich but focuses more on treatments than understanding mechanisms, indicating a need for deeper mechanistic exploration for treatment breakthroughs in the future.

Response of cells and tissues to shear stress

Shear stress is essential for normal physiology and malignancy. Common physiological processes - such as blood flow, particle flow in the gut, or contact between migratory cell clusters and their substrate - produce shear stress that can have an impact on the behavior of different tissues. In addition, shear stress has roles in processes of biomedical interest, such as wound healing, cancer and fibrosis induced by soft implants. Thus, understanding how cells react and adapt to shear stress is important. In this Review, we discuss in vivo and in vitro data obtained from vascular and epithelial models; highlight the insights these have afforded regarding the general mechanisms through which cells sense, transduce and respond to shear stress at the cellular levels; and outline how the changes cells experience in response to shear stress impact tissue organization. Finally, we discuss the role of shear stress in collective cell migration, which is only starting to be appreciated. We review our current understanding of the effects of shear stress in the context of embryo development, cancer and fibrosis, and invite the scientific community to further investigate the role of shear stress in these scenarios.

Polysialylation controls immune function of myeloid cells in murine model of pneumococcal pneumonia

Polysialic acid (polySia) is a post-translational modification of a select group of cell-surface proteins that guides cellular interactions. As the overall impact of changes in expression of this glycan on leukocytes during infection is not known, we evaluate the immune response of polySia-deficient ST8SiaIV-/- mice infected with Streptococcus pneumoniae (Spn). Compared with wild-type (WT) mice, ST8SiaIV-/- mice are less susceptible to infection and clear Spn from airways faster, with alveolar macrophages demonstrating greater viability and phagocytic activity. Leukocyte pulmonary recruitment, paradoxically, is diminished in infected ST8SiaIV-/- mice, corroborated by adoptive cell transfer, microfluidic migration experiments, and intravital microscopy, and possibly explained by dysregulated ERK1/2 signaling. PolySia is progressively lost from neutrophils and monocytes migrating from bone marrow to alveoli in Spn-infected WT mice, consistent with changing cellular functions. These data highlight multidimensional effects of polySia on leukocytes during an immune response and suggest therapeutic interventions for optimizing immunity.

The Emerging Role of MMP12 in the Oral Environment

Matrix metalloproteinase-12 (MMP12), or macrophage metalloelastase, plays important roles in extracellular matrix (ECM) component degradation. Recent reports show MMP12 has been implicated in the pathogenesis of periodontal diseases. To date, this review represents the latest comprehensive overview of MMP12 in various oral diseases, such as periodontitis, temporomandibular joint dysfunction (TMD), orthodontic tooth movement (OTM), and oral squamous cell carcinoma (OSCC). Furthermore, the current knowledge regarding the distribution of MMP12 in different tissues is also illustrated in this review. Studies have implicated the association of MMP12 expression with the pathogenesis of several representative oral diseases, including periodontitis, TMD, OSCC, OTM, and bone remodelling. Although there may be a potential role of MMP12 in oral diseases, the exact pathophysiological role of MMP12 remains to be elucidated. Understanding the cellular and molecular biology of MMP12 is essential, as MMP12 could be a potential target for developing therapeutic strategies targeting inflammatory and immunologically related oral diseases.

DRP1 contributes to head and neck cancer progression and induces glycolysis through modulated FOXM1/MMP12 axis

Abnormal DRP1 expression has been identified in a variety of human cancers. However, the prognostic potential and mechanistic role of DRP1 in head and neck cancer (HNC) are currently poorly understood. Here, we demonstrated a significant upregulation of DRP1 in HNC tissues, and that DRP1 expression correlates with poor survival of HNC patients. Diminished DRP1 expression suppressed tumor growth and metastasis in both in vitro and in vivo models. DRP1 expression was positively correlated with FOXM1 and MMP12 expression in HNC patient samples, suggesting pathological relevance in the context of HNC development. Moreover, DRP1 depletion affected aerobic glycolysis through the downregulation of glycolytic genes, and overexpression of MMP12 in DRP1‐depleted cells could help restore glucose consumption and lactate production. Using ChIP‐qPCR, we showed that DRP1 modulates FOXM1 expression, which can enhance MMP12 transcription by binding to its promoter. We also showed that miR‐575 could target 3’UTR of DRP1 mRNA and suppress DRP1 expression. Collectively, our study provides mechanistic insights into the role of DRP1 in HNC and highlights the potential of targeting the miR‐575/DRP1/FOXM1/MMP12 axis as a novel therapy for the prevention of HNC progression.

Giant obscurin regulates migration and metastasis via RhoA-dependent cytoskeletal remodeling in pancreatic cancer

Obscurins, encoded by the OBSCN gene, are giant cytoskeletal proteins with structural and regulatory roles. Large scale omics analyses reveal that OBSCN is highly mutated across different types of cancer, exhibiting a 5-8% mutation frequency in pancreatic cancer. Yet, the functional role of OBSCN in pancreatic cancer progression and metastasis has to be delineated. We herein show that giant obscurins are highly expressed in normal pancreatic tissues, but their levels are markedly reduced in pancreatic ductal adenocarcinomas. Silencing of giant obscurins in non-tumorigenic Human Pancreatic Ductal Epithelial (HPDE) cells and obscurin-expressing Panc5.04 pancreatic cancer cells induces an elongated, spindle-like morphology and faster cell migration via cytoskeletal remodeling. Specifically, depletion of giant obscurins downregulates RhoA activity, which in turn results in reduced focal adhesion density, increased microtubule growth rate and faster actin dynamics. Although OBSCN knockdown is not sufficient to induce de novo tumorigenesis, it potentiates tumor growth in a subcutaneous implantation model and exacerbates metastasis in a hemispleen murine model of pancreatic cancer metastasis, thereby shortening survival. Collectively, these findings reveal a critical role of giant obscurins as tumor suppressors in normal pancreatic epithelium whose loss of function induces RhoA-dependent cytoskeletal remodeling, and promotes cell migration, tumor growth and metastasis.

A Novel Small Peptide H-KI20 Inhibits Retinal Neovascularization Through the JNK/ATF2 Signaling Pathway

Purpose

Abundant evidence has shown benefits of antivascular endothelial growth factor (anti-VEGF) therapies in neovascular eye diseases. However, the high cost, side effects, and inconvenience of frequent injections demand alternative novel drug candidates. This study aimed to analyze antiangiogenic effects of peptide H-KI20 and illustrated signaling mechanisms.

Methods

Live cell culture and tracing, wound healing assay, and tube formation were performed in human retinal microvascular endothelial cells (HRECs). The chick embryo chorioallantoic membrane and mouse oxygen-induced ischemic retinopathy model were applied to examine the effects of H-KI20 in vivo. The intracellular signaling pathways were examined. Molecular docking and surface plasmon resonance assay were used to validate the direct interaction of H-KI20 and c-Jun N-terminal kinase 2 (JNK2).

Results

H-KI20 had high penetration ability in vitro and in vivo. It inhibited motility, migration, and tube formation of HRECs, without cytotoxicity, and inhibited angiogenesis in vivo. Furthermore, H-KI20 treatment reduced the phosphorylation level of activating transcription factor 2 (ATF2) stimulated by VEGF via downregulating p-JNK. H-KI20 bound to JNK2 directly with a dissociation constant value of 83.68 µM. The knockdown of ATF2 attenuated VEGF-induced tube formation and decreased the movement speed of HRECs.

Conclusions

H-KI20 inhibited angiogenesis both in vitro and in vivo. The ratios of p-ATF2/ATF2 and p-JNK/JNK stimulated by VEGF were decreased by H-KI20, and H-KI20 targeted JNK2 directly. In addition, the pivotal role of ATF2 in VEGF-induced retinal neovascularization was elucidated for the first time. Taken together, H-KI20 displays potential for pathological retinal angiogenesis as a sustained and low-toxic peptide.

Complex Interplay of Genes Underlies Invasiveness in Fibrosarcoma Progression Model

Sarcomas are a heterogeneous group of mesenchymal tumours, with a great variability in their clinical behaviour. While our knowledge of sarcoma initiation has advanced rapidly in recent years, relatively little is known about mechanisms of sarcoma progression. JUN-murine fibrosarcoma progression series consists of four sarcoma cell lines, JUN-1, JUN-2, JUN-2fos-3, and JUN-3. JUN-1 and -2 were established from a single tumour initiated in a H2K/v-jun transgenic mouse, JUN-3 originates from a different tumour in the same animal, and JUN-2fos-3 results from a targeted in vitro transformation of the JUN-2 cell line. The JUN-1, -2, and -3 cell lines represent a linear progression from the least transformed JUN-2 to the most transformed JUN-3, with regard to all the transformation characteristics studied, while the JUN-2fos-3 cell line exhibits a unique transformation mode, with little deregulation of cell growth and proliferation, but pronounced motility and invasiveness. The invasive sarcoma sublines JUN-2fos-3 and JUN-3 show complex metabolic profiles, with activation of both mitochondrial oxidative phosphorylation and glycolysis and a significant increase in spared respiratory capacity. The specific transcriptomic profile of invasive sublines features very complex biological relationships across the identified genes and proteins, with accentuated autocrine control of motility and angiogenesis. Pharmacologic inhibition of one of the autocrine motility factors identified, Ccl8, significantly diminished both motility and invasiveness of the highly transformed fibrosarcoma cell. This progression series could be greatly valuable for deciphering crucial aspects of sarcoma progression and defining new prognostic markers and potential therapeutic targets.

MTA2 silencing attenuates the metastatic potential of cervical cancer cells by inhibiting AP1-mediated MMP12 expression via the ASK1/MEK3/p38/YB1 axis

Metastasis-associated protein 2 (MTA2) is a transcription factor that is highly associated with matrix metalloproteinase 12 (MMP12). Thus, we hypothesized that MTA2 may regulate MMP12 expression and is involved in cervical cancer metastasis. Results showed that MTA2 and MMP12 were highly expressed in cervical cancer cells, and MTA2 knockdown reduced MMP12 expression and inhibited the metastasis of cervical cancer cells in xenograft mice. MMP12 knockdown did not influence the viability of cervical cancer cells but clearly inhibited cell migration and invasion both in vitro and in vivo. MMP12 was highly expressed in cervical tumor tissues and correlated with the poor survival rate of patients with cervical cancer. Further investigations revealed that p38 mitogen-activated protein kinase (p38), mitogen-activated protein kinase kinase 3 (MEK3), and apoptosis signal-regulating kinase 1 (ASK1) were involved in MMP12 downregulation in response to MTA2 knockdown. Results also demonstrated that p38-mediated Y-box binding protein1 (YB1) phosphorylation disrupted the binding of AP1 (c-Fos/c-Jun) to the MMP12 promoter, thereby inhibiting MMP12 expression and the metastatic potential of cervical cancer cells. Collectively, targeting both MTA2 and MMP12 may be a promising strategy for the treatment of cervical cancer.

The effects of luminal and trans-endothelial fluid flows on the extravasation and tissue invasion of tumor cells in a 3D in vitro microvascular platform

Throughout the process of metastatic dissemination, tumor cells are continuously subjected to mechanical forces resulting from complex fluid flows due to changes in pressures in their local microenvironments. While these forces have been associated with invasive phenotypes in 3D matrices, their role in key steps of the metastatic cascade, namely extravasation and subsequent interstitial migration, remains poorly understood. In this study, an in vitro model of the human microvasculature was employed to subject tumor cells to physiological luminal, trans-endothelial, and interstitial flows to evaluate their effects on those key steps of metastasis. Luminal flow promoted the extravasation potential of tumor cells, possibly as a result of their increased intravascular migration speed. Trans-endothelial flow increased the speed with which tumor cells transmigrated across the endothelium as well as their migration speed in the matrix following extravasation. In addition, tumor cells possessed a greater propensity to migrate in close proximity to the endothelium when subjected to physiological flows, which may promote the successful formation of metastatic foci. These results show important roles of fluid flow during extravasation and invasion, which could determine the local metastatic potential of tumor cells.

Functional roles of GDF15 in modulating microenvironment to promote carcinogenesis

Obesity and related metabolic dysregulation are risk factors for many types of cancer. The interactions between a developing tumor and its microenvironment are known to implicate a complex "crosstalk" among the factors produced by the population of cells. Among these factors, Growth and differentiation factor 15 (GDF15) has a functional role in cancer. GDF15 expression is induced in response to the conditions associated with cellular stress and diseases. The GDF15 receptor, a member of the glial-cell-derived neurotropic factor family (GDNF), is a GDNF family receptor α-like (GFRAL) protein. GDF15 induces pro-angiogenic effects in tumors. However, GDF15 could affect tumorigenesis both positively and negatively. With a better understanding of the upstream disease pathways reflected by GDF15, new treatment targets may emerge.

Knockdown of Linc00511 inhibits TGF-β-induced cell migration and invasion by suppressing epithelial-mesenchymal transition and down-regulating MMPs expression

Epithelial mesenchymal transition (EMT) is a critical step in cancer metastasis. Some evidences have been provided to verify up-regulation of linc00511 in multiple cancers and oncogenic roles during cancer malignant process. But, the roles of linc00511 on the metastasis of lung cancer are still largely unclear. Our study aims to reveal the functional effects of linc00511 on TGF-β1-induced EMT in lung cancer. Our results showed that knockdown of linc00511 significantly inhibited TGF-β1-induced migration and invasion and down-regulated the mRNA and protein levels of MMP2, MMP9 and MMP12 in TGF-β1 treated SPCA1 and H1975 cells. Also, western blotting results showed that inhibition of linc00511 remarkably suppressed TGF-β1-induced N-cadherin, Vimentin and snail and increased E-cadherin expression in SPCA1 and H1975 cells. Noteworthy, we further found that inhibition of linc00511 could down-regulate TGF-β1-induced ZEB2 mRNA and protein levels by sponging miR-183-5p in SPCA1 and H1975 cells. Taken together, our findings suggested knockdown linc00511 suppressed TGF-β1-induced migration and invasion via inhibiting EMT and MMPs in lung cancer cells.

Shear stress activates ATOH8 via autocrine VEGF promoting glycolysis dependent-survival of colorectal cancer cells in the circulation

Background

Metastasis and recurrence, wherein circulating tumour cells (CTCs) play an important role, are the leading causes of death in colorectal cancer (CRC). Metastasis-initiating CTCs manage to maintain intravascular survival under anoikis, immune attack, and importantly shear stress; however, the underlying mechanisms remain poorly understood.

Methods

In view of the scarcity of CTCs in the bloodstream, suspended colorectal cancer cells were flowed into the cyclic laminar shear stress (LSS) according to previous studies. Then, we detected these suspended cells with a CK8+/CD45−/DAPI+ phenotype and named them mimic circulating tumour cells (m-CTCs) for subsequent CTCs related researches. Quantitative polymerase chain reaction, western blotting, and immunofluorescence were utilised to analyse gene expression change of m-CTCs sensitive to LSS stimulation. Additionally, we examined atonal bHLH transcription factor 8 (ATOH8) expressions in CTCs among 156 CRC patients and mice by fluorescence in situ hybridisation and flow cytometry. The pro-metabolic and pro-survival functions of ATOH8 were determined by glycolysis assay, live/dead cell vitality assay, anoikis assay, and immunohistochemistry. Further, the concrete up-and-down mechanisms of m-CTC survival promotion by ATOH8 were explored.

Results

The m-CTCs actively responded to LSS by triggering the expression of ATOH8, a fluid mechanosensor, with executive roles in intravascular survival and metabolism plasticity. Specifically, ATOH8 was upregulated via activation of VEGFR2/AKT signalling pathway mediated by LSS induced VEGF release. ATOH8 then transcriptionally activated HK2-mediated glycolysis, thus promoting the intravascular survival of colorectal cancer cells in the circulation.

Conclusions

This study elucidates a novel mechanism that an LSS triggered VEGF-VEGFR2-AKT-ATOH8 signal axis mediates m-CTCs survival, thus providing a potential target for the prevention and treatment of hematogenous metastasis in CRC.

Cdc42-mediated supracellular cytoskeleton induced cancer cell migration under low shear stress

Tumor microenvironment is composed of biological, chemical and physical factors. Mechanical factors are more and more focused these years. Therefore, mimicking mechanical factors' contribution to cancer cell malignancy will greatly improve the advance in this field. Although the induced malignant behaviors are present under many stimuli such as growth or inflammatory factors, the cell key physical migration mechanisms are still missing. In this study, we identify that low shear stress significantly promotes the formation of needle-shaped membrane protrusions, which is called filopodia and important for the sense and interact of a cell with extracellular matrix in the tumor microenvironment. Under low shear stress, the migration is promoted while it is inhibited in the presence of ROCK inhibitor Y27632, which could abolish the F-actin network. Using cell imaging, we further unravel that key to these protrusions is Cell division cycle 42 (Cdc42) dependent. After Cdc42 activation, the filopodia is more and longer, acting as massagers to pass the information from a cell to the microenvironment for its malignant phenotype. In the Cdc42 inhibition, the filopodia is greatly reduced. Moreover, small GTPases Cdc42 rather than Rac1 and Rho directly controls the filopodia formation. Our work highlights that low shear stress and Cdc42 activation are sufficient to promote filopodia formation, it not only points out the novel structure for cancer progression but also provides the experimental physical basis for the efficient drug anti-cancer strategies.

Mechanical Stress-Dependent Autophagy Component Release via Extracellular Nanovesicles in Tumor Cells

Tumor cells metastasizing through the bloodstream or lymphatic systems must withstand acute shear stress (ASS). Autophagy is a cell survival mechanism that functions in response to stressful conditions, but also contributes to cell death or apoptosis. We predicted that a compensation pathway to autophagy exists in tumor cells subjected to mechanical stress. We found that ASS promoted autophagosome (AP) accumulation and induced release of extracellular nanovesicles (EVs) containing autophagy components. Furthermore, we found that ASS promoted autophagic vesicles fused with multivesicular body (MVB) to form an AP-MVB compartment and then induced autophagy component release into the extracellular space via EVs through the autophagy-MVB-exosome pathway. More importantly, either increasing intracellular autophagosome accumulation or inhibiting autophagic degradation promoted AP-MVB accumulation but did not induce autophagy-associated protein release via EVs except under ASS, demonstrating the existence of a mechanical stress-dependent compensation pathway. Together, these findings revealed that EVs provide an additional protection mechanism for tumor cells and counteract autophagy to maintain cellular homeostasis under acute shear stress.

The mechanical and pharmacological regulation of glioblastoma cell migration in 3D matrices

The invasion of glioblastoma is a complex process based on the interactions of tumor cells and the extracellular matrix. Tumors that are engineered using biomaterials are more physiologically relevant than a two-dimensional (2D) cell culture system. Matrix metalloproteinases and the plasminogen activator generated by tumor cells regulate a tumor's invasive behavior. In this study, microtumors were fabricated by encapsulating U87 glioma cells in Type I collagen and then glioma cell migration in the collagen hydrogels was investigated. Crosslinking of collagen with 8S-StarPEG increased the hydrogel viscosity and reduced the tumor cell migration speed in the hydrogels. The higher migration speed corresponded to the increased gene expression of MMP-2, MMP-9, urokinase plasminogen activator (uPA), and tissue plasminogen activator (tPA) in glioma cells grown in non-crosslinked collagen hydrogels. Inhibitors of these molecules hindered U87 and A172 cell migration in collagen hydrogels. Aprotinin and tranexamic acid did not inhibit U87 and A172 migration on the culture dish. This study demonstrated the differential effect of pharmacologic molecules on tumor cell motility in either a 2D or three-dimensional culture environment.

Solid stress-induced migration is mediated by GDF15 through Akt pathway activation in pancreatic cancer cells

Solid stress is a biomechanical abnormality of the tumor microenvironment that plays a crucial role in tumor progression. When it is applied to cancer cells, solid stress hinders their proliferation rate and promotes cancer cell invasion and metastatic potential. However, the underlying mechanisms of how it is implicated in cancer metastasis is not yet fully understood. Here, we used two pancreatic cancer cell lines and an established in vitro system to study the effect of solid stress-induced signal transduction on pancreatic cancer cell migration as well as the mechanism involved. Our results show that the migratory ability of cells increases as a direct response to solid stress. We also found that Growth Differentiation Factor 15 (GDF15) expression and secretion is strongly upregulated in pancreatic cancer cells in response to mechanical compression. Performing a phosphoprotein screening, we identified that solid stress activates the Akt/CREB1 pathway to transcriptionally regulate GDF15 expression, which eventually promotes pancreatic cancer cell migration. Our results suggest a novel solid stress signal transduction mechanism bringing GDF15 to the centre of pancreatic tumor biology and rendering it a potential target for future anti-metastatic therapeutic innovations.

FAK is Required for Tumor Metastasis-Related Fluid Microenvironment in Triple-Negative Breast Cancer

Cancer cell metastasis is the main cause of death in patients with cancer. Many studies have investigated the biochemical factors that affect metastasis; however, the role of physical factors such as fluid shear stress (FSS) in tumorigenesis and metastasis have been less investigated. Triple-negative breast cancer (TNBC) has a higher incidence of lymph node invasion and distant metastasis than other subtypes of breast cancer. In this study, we investigated the influence of FSS in regulating the malignant behavior of TNBC cells. Our data demonstrate that low FSS promotes cell migration, invasion, and drug resistance, while high FSS has the opposite results; additionally, we found that these phenomena were regulated through focal adhesion kinase (FAK). Using immunohistochemistry staining, we show that FAK levels correlate with the nodal stage and that FAK is a significant independent predictor of overall survival in patients. Altogether, these data implicate FAK as a fluid mechano-sensor that regulates the cell motility induced by FSS and provide a strong rationale for cancer treatments that combine the use of anti-cancer drugs and strategies to modulate tumor interstitial fluid flow.

The roles of prostaglandin F2 in regulating the expression of matrix metalloproteinase-12 via an insulin growth factor-2-dependent mechanism in sheared chondrocytes

Osteoarthritis (OA) was recently identified as being regulated by the induction of cyclooxygenase-2 (COX-2) in response to high fluid shear stress. Although the metabolic products of COX-2, including prostaglandin (PG)E₂, 15-deoxy-Δ^12,14-PGJ₂ (15d-PGJ₂), and PGF_2α, have been reported to be effective in regulating the occurrence and development of OA by activating matrix metalloproteinases (MMPs), the roles of PGF_2α in OA are largely overlooked. Thus, we showed that high fluid shear stress induced the mRNA expression of MMP-12 via cyclic (c)AMP- and PGF_2α-dependent signaling pathways. Specifically, we found that high fluid shear stress (20 dyn/cm²) significantly increased the expression of MMP-12 at 6 h ( > fivefold), which then slightly decreased until 48 h ( > threefold). In addition, shear stress enhanced the rapid synthesis of PGE₂ and PGF_2α, which generated synergistic effects on the expression of MMP-12 via EP2/EP3-, PGF2α receptor (FPR)-, cAMP- and insulin growth factor-2 (IGF-2)-dependent phosphatidylinositide 3-kinase (PI3-K)/protein kinase B (AKT), c-Jun N-terminal kinase (JNK)/c-Jun, and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-activating pathways. Prolonged shear stress induced the synthesis of 15d-PGJ₂, which is responsible for suppressing the high levels of MMP-12 at 48 h. These in vitro observations were further validated by in vivo experiments to evaluate the mechanisms of MMP-12 upregulation during the onset of OA by high fluid shear stress. By delineating this signaling pathway, our data provide a targeted therapeutic basis for combating OA.

Shear stress induces cartilage cells to produce hormone-like molecules that activate the expression of an enzyme implicated in the development of osteoarthritis, a degenerative joint disease. Pu Wang and colleagues from Northeastern University in Shenyang, China, exposed human cartilage cells to high fluid shear stress for up to 2 days. This frictional strain rapidly stimulated the production of a proinflammatory enzyme, COX-2, which in turn promoted the synthesis of two hormone-like substances, called prostaglandins. These prostaglandins, PGE₂ and PGF_2α, then induced expression of an osteoarthritis-associated enzyme called MMP-12 that destroys the supporting structure that surrounds cartilage cells. The researchers, working both in human cells and in mouse models, further delineated several intermediate signaling molecules in the pathway linking shear stress with MMP-12 activation, thereby revealing several new potential drug targets for combating osteoarthritis in patients.

Fluid Shear Stress Promotes Autophagy in Hepatocellular Carcinoma Cells

The autophagy in cancer cells is recognized as an essential hallmark of tumors, which can enhance cancer cell migration and invasion, and result in high incidence of tumor metastasis. The fluid shear stress (FSS) in tumor mechanical microenvironment plays a pivotal role in mediating the behaviors and functions of cells. In this study, the hepatocellular carcinoma cells were exposed to 1.4 dyn/cm² FSS to explore whether FSS could induce autophagy. The results of TEM, Ad-mCherry-GFP labeled LC3B, and mRNA and protein expression of autophagy markers confirmed that FSS could induce autophagy in a time-dependent manner. Additionally, the inhibition of autophagy significantly downregulated the expression of PI3K, FAK and Rho GTPases, and attenuated the ability of cell migration, suggesting that FSS-induced autophagy depended on PI3K- FAK-Rho GTPases pathway. This study elucidated the role of FSS in inducing autophagy during tumor progression, which has emerged as a promising clinical strategy for cancer.

Supervillin promotes epithelial-mesenchymal transition and metastasis of hepatocellular carcinoma in hypoxia via activation of the RhoA/ROCK-ERK/p38 pathway

Background

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world and metastasis is the leading cause of death associated with HCC. Hypoxia triggers the epithelial-mesenchymal transition (EMT) of cancer cells, which enhances their malignant character and elevates metastatic risk. Supervillin associates tightly with the membrane and cytoskeleton, promoting cell motility, invasiveness, and cell survival. However, the roles of supervillin in HCC metastasis remain unclear.

Methods

Tissue microarray technology was used to immunohistochemically stain for supervillin antibody in 173 HCC tissue specimens and expression levels correlated with the clinicopathological variables. Tumor cell motility and invasiveness, as well as changes in the mRNA expression levels of genes associated with cancer cell EMT, were investigated. The relationship between supervillin and Rho GTPases was examined using Co-IP and GST pull-down.

Results

Hypoxia-induced upregulation of supervillin promoted cancer cell migration and invasion via the activation of the ERK/p38 pathway downstream of RhoA/ROCK signaling. Furthermore, supervillin regulated the expression of EMT genes during hypoxia and accelerated the metastasis of HCC in vivo.

Conclusions

Hypoxia-induced increase in supervillin expression is a significant and independent predictor of cancer metastasis, which leads to poor survival in HCC patients. Our results suggest that supervillin may be a candidate prognostic factor for HCC and a valuable target for therapy.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0787-2) contains supplementary material, which is available to authorized users.

Fluid shear stress and tumor metastasis

The tumor microenvironment (TME) is a key factor regulating tumor cell invasion and metastasis. The effects of biochemical factors such as stromal cells, immune cells, and cytokines have been previously investigated. Owing to restrictions by the natural barrier between physical and biochemical disciplines, the role of physical factors in tumorigenesis is unclear. However, with the emergence of interdisciplinary mechanobiology and continuous advancements therein in the past 30 years, studies on the effect of physical properties such as hardness or shear stress on tumorigenesis and tumor progression are constantly renewing our understanding of mechanotransduction mechanisms. Shear stress, induced by liquid flow, is known to actively participate in proliferation, apoptosis, invasion, and metastasis of tumor cells. The present review discusses the progress and achievements in studies on tumor fluid microenvironment in recent years, especially fluid shear stress, on tumor metastasis, and presents directions for future study.

Low-level shear stress promotes migration of liver cancer stem cells via the FAK-ERK1/2 signalling pathway

Cancer stem cells (CSCs) are a small subpopulation of tumour cells that have been proposed to be responsible for cancer initiation, chemotherapy resistance and cancer recurrence. Shear stress activated cellular signalling is involved in cellular migration, proliferation and differentiation. However, little is known about the effects of shear stress on the migration of liver cancer stem cells (LCSCs). Here, we studied the effects of shear stress that are generated from a parallel plated flow chamber system, on LCSC migration and the activation of focal adhesion kinase (FAK) and extracellular signal regulated kinase1/2 (ERK1/2), using transwell assay and western blot, respectively. We found that 2 dyne/cm² shear stress loading for 6 h promotes LCSC migration and activation of the FAK and ERK1/2 signalling pathways, whereas treatment with the FAK phosphorylation inhibitor PF573228 or the ERK1/2 phosphorylation inhibitor PD98059 suppressed the shear stress-promoted migration, indicating the involvement of FAK and ERK1/2 activation in shear stress-induced LCSC migration. Additionally, atomic force microscopy (AFM) analysis showed that shear stress lowers LCSC stiffness via the FAK and ERK1/2 pathways, suggesting that the mechanism by which shear stress promotes LCSC migration might partially be responsible for the decrease in cell stiffness. Further experiments focused on the role of the actin cytoskeleton, demonstrating that the F-actin filaments in LCSCs are less well-defined after shear stress treatment, providing an explanation for the reduction in cell stiffness and the promotion of cell migration. Overall, our study demonstrates that shear stress promotes LCSC migration through the activation of the FAK-ERK1/2 signalling pathways, which further results in a reduction of organized actin and softer cell bodies.

Matrix metalloproteinase 12 promotes tumor propagation in the lung

OBJECTIVE

Past studies are inconsistent with regard to the role of matrix metalloproteinase 12 in lung tumorigenesis. This is due, in part, to differential tumorigenesis based on tumor-derived versus immune-derived matrix metalloproteinase 12 expression. Our study aims to thoroughly dissect the role of matrix metalloproteinase 12 in lung tumorigenesis.

METHODS

We tested matrix metalloproteinase 12 expression and the association with prognosis using a tissue array and a published non-small cell lung cancer gene expression database. In addition, we characterized the contribution of matrix metalloproteinase 12 to tumor propagation in the lung using a series of in vitro and in vivo studies.

RESULTS

Tumor cells of a diverse set of human lung cancers stained positive for matrix metalloproteinase 12, and high matrix metalloproteinase 12 mRNA levels in the tumor were associated with reduced survival. The lung microenvironment stimulated endogenous production of matrix metalloproteinase 12 in lung cancer cells (human 460 lung cancer cell line, Lewis lung carcinoma). In vitro, matrix metalloproteinase 12 knockout Lewis lung carcinoma and Lewis lung carcinoma cells had the same proliferation rate, but Lewis lung carcinoma showed increased invasiveness. In vivo, deficiency of matrix metalloproteinase 12 in Lewis lung carcinoma cells, but not in the host, reduced tumor growth and invasiveness.

CONCLUSIONS

We suggest that tumor cell-derived matrix metalloproteinase 12 promotes tumor propagation in the lung and that in the context of pulmonary malignancies matrix metalloproteinase 12 should further be tested as a potential novel therapeutic target.

Giant obscurins regulate the PI3K cascade in breast epithelial cells via direct binding to the PI3K/p85 regulatory subunit

Obscurins are a family of giant cytoskeletal proteins, originally identified in striated muscles where they have structural and regulatory roles. We recently showed that obscurins are abundantly expressed in normal breast epithelial cells where they play tumor and metastasis suppressing roles, but are nearly lost from advanced stage breast cancer biopsies. Consistent with this, loss of giant obscurins from breast epithelial cells results in enhanced survival and growth, epithelial to mesenchymal transition (EMT), and increased cell migration and invasion in vitro and in vivo. In the current study, we demonstrate that loss of giant obscurins from breast epithelial cells is associated with significantly increased phosphorylation and subsequent activation of the PI3K signaling cascade, including activation of AKT, a key regulator of tumorigenesis and metastasis. Pharmacological and molecular inhibition of the PI3K pathway in obscurin-depleted breast epithelial cells results in reversal of EMT, (re)formation of cell-cell junctions, diminished mammosphere formation, and decreased cell migration and invasion. Co-immunoprecipitation, pull-down, and surface plasmon resonance assays revealed that obscurins are in a complex with the PI3K/p85 regulatory subunit, and that their association is direct and mediated by the obscurin-PH domain and the PI3K/p85-SH3 domain with a KD of ~50 nM. We therefore postulate that giant obscurins act upstream of the PI3K cascade in normal breast epithelial cells, regulating its activation through binding to the PI3K/p85 regulatory subunit.

Fluid shear stress induces epithelial-mesenchymal transition (EMT) in Hep-2 cells

Laryngeal squamous cell carcinoma (LSCC) is one of the most commonly diagnosed malignancies with high occurrence of tumor metastasis, which usually exposes to fluid shear stress (FSS) in lymphatic channel and blood vessel. Epithelial-mesenchymal transition (EMT) is an important mechanism that induces metastasis and invasion of tumors. We hypothesized that FSS induced a progression of EMT in laryngeal squamous carcinoma. Accordingly, the Hep-2 cells were exposed to 1.4 dyn/cm² FSS for different durations. Our results showed that most of cells changed their morphology from polygon to elongated spindle with well-organized F-actin and abundant lamellipodia/filopodia in protrusions. After removing the FSS, cells gradually recovered their flat polygon morphology. FSS induced Hep-2 cells to enhance their migration capacity in a time-dependent manner. In addition, FSS down-regulated E-cadherin, and simultaneously up-regulated N-cadherin, translocated β-catenin into the nucleus. These results confirmed that FSS induced the EMT in Hep-2 cells, and revealed a reversible mesenchymal-epithelial transition (MET) process when FSS was removed. We further examined the time-expressions of signaling cascades, and demonstrated that FSS induces the EMT and enhances cell migration depending on integrin-ILK/PI3K-AKT-Snail signaling events. The current study suggests that FSS, an important biophysical factor in tumor microenvironment, is a potential determinant of cell behavior and function regulation.

Erythrocyte membrane-encapsulated celecoxib improves the cognitive decline of Alzheimer's disease by concurrently inducing neurogenesis and reducing apoptosis in APP/PS1 transgenic mice

Alzheimer's disease (AD) is characterized by the loss of neurogenesis and excessive induction of apoptosis. The induction of neurogenesis and inhibition of apoptosis may be a promising therapeutic approach to combating the disease. Celecoxib (CB), a cyclooxygenase-2 specific inhibitor, could offer neuroprotection. Specifically, the CB-encapsulated erythrocyte membranes (CB-RBCMs) sustained the release of CB over a period of 72 h in vitro and exhibited high brain biodistribution efficiency following intranasal administration, which resulted in the clearance of aggregated β-amyloid proteins (Aβ) in neurons. The high accumulation of the CB-RBCMs in neurons resulted in a decrease in the neurotoxicity of CB and an increase in the migratory activity of neurons, and alleviated cognitive decline in APP/PS1 transgenic (Tg) mice. Indeed, COX-2 metabolic products including prostaglandin E2 (PGE₂) and PGD₂, PGE₂ induced neurogenesis by enhancing the expression of SOD2 and 14-3-3ζ, and PGD₂ stimulated apoptosis by increasing the expression of BIK and decreasing the expression of ARRB1. To this end, the CB-RBCMs achieved better effects on concurrently increasing neurogenesis and decreasing apoptosis than the phospholipid membrane-encapsulated CB liposomes (CB-PSPD-LPs), which are critical for the development and progression of AD. Therefore, CB-RBCMs provide a rational design to treat AD by promoting the self-repairing capacity of the brain.

Prostaglandin I2 is responsible for ameliorating prostaglandin E2 stress in stimulating the expression of tumor necrosis factor α in a β-amyloid protein -dependent mechanism

Cyclooxygenase-2 (COX-2) has been found to be induced during the early stage of Alzheimer's disease (AD). Using mouse-derived astrocyte and APP/PS1 transgenic (Tg) mice as model systems, we firstly elucidated the mechanisms underlying COX-2 metabolic production including prostaglandin (PG)E₂- and PGI₂-mediated tumor necrosis factor α (TNF-α) regulation. Specifically, PGE₂ accumulation in astrocyte activated the p38 and JNK/c-Jun signaling pathways via phosphorylation, resulting in TNF-α expression. In contrast, the administration of PGI₂ attenuated the effects of PGE₂ in stimulating the production of TNF-α by inhibiting the activity of TNF-α promoter and the binding activity of AP1 on the promoter of TNF-α. Moreover, our data also showed that not only Aβ_1-42 oligomers but also Aβ_1-42 fibrils have the ability to involve in mediating the antagonistic effects of PGE₂ and PGI₂ on regulating the expression of TNF-α via a p38- and JNK/c-Jun-dependent, AP1-transactivating mechanism. Reciprocally, the production of TNF-α finally accelerated the deposition of β-amyloid protein (Aβ)_1-42 in β-amyloid plaques (APs), which contribute to the cognitive decline of AD.

Activation of tumor suppressor LKB1 by honokiol abrogates cancer stem-like phenotype in breast cancer via inhibition of oncogenic Stat3

Tumor suppressor and upstream master kinase Liver kinase B1 (LKB1) plays a significant role in suppressing cancer growth and metastatic progression. We show that low-LKB1 expression significantly correlates with poor survival outcome in breast cancer. In line with this observation, loss-of-LKB1 rendered breast cancer cells highly migratory and invasive, attaining cancer stem cell-like phenotype. Accordingly, LKB1-null breast cancer cells exhibited an increased ability to form mammospheres and elevated expression of pluripotency-factors (Oct4, Nanog and Sox2), properties also observed in spontaneous tumors in Lkb1^-/- mice. Conversely, LKB1-overexpression in LKB1-null cells abrogated invasion, migration and mammosphere-formation. Honokiol (HNK), a bioactive molecule from Magnolia grandiflora increased LKB1 expression, inhibited individual cell-motility and abrogated the stem-like phenotype of breast cancer cells by reducing the formation of mammosphere, expression of pluripotency-factors and aldehyde dehydrogenase activity. LKB1, and its substrate, AMP-dependent protein kinase (AMPK) are important for HNK-mediated inhibition of pluripotency factors since LKB1-silencing and AMPK-inhibition abrogated, while LKB1-overexpression and AMPK-activation potentiated HNK's effects. Mechanistic studies showed that HNK inhibited Stat3-phosphorylation/activation in an LKB1-dependent manner, preventing its recruitment to canonical binding-sites in the promoters of Nanog, Oct4 and Sox2. Thus, inhibition of the coactivation-function of Stat3 resulted in suppression of expression of pluripotency factors. Further, we showed that HNK inhibited breast tumorigenesis in mice in an LKB1-dependent manner. Molecular analyses of HNK-treated xenografts corroborated our in vitro mechanistic findings. Collectively, these results present the first in vitro and in vivo evidence to support crosstalk between LKB1, Stat3 and pluripotency factors in breast cancer and effective anticancer modulation of this axis with HNK treatment.

Orthodontic tensile strain induces angiogenesis via type IV collagen degradation by matrix metalloproteinase-12

BACKGROUND AND OBJECTIVE

During orthodontic tooth movement (OTM), periodontal ligament (PDL) is remodeled dynamically, which requires sufficient blood supply for the regeneration of PDL. However, little is known about the remodeling of blood vessels during OTM. In this study, we hypothesized that the orthodontic tensile strain upregulates matrix metalloproteinase-12 (MMP-12) expression in the tension zone and induces angiogenesis via degradation of type IV collagen (Col-IV) in vascular endothelial basement membrane during the early stage of OTM.

MATERIAL AND METHODS

Temporal and spatial MMP-12 expression in the tension zone of PDL, during the early stage of OTM, were examined by immunohistochemistry in rats. Continuous tensile strain was applied to cultured human immortalized PDL cell lines (HPL cells) and MMP-12 expression was examined in vitro. Colocalization of MMP-12 and Col-IV in vivo were examined by immunohistochemistry. To investigate whether MMP-12 produced by HPL cells could degrade Col-IV, recombinant Col-IV was incubated in the culture supernatants of HPL cells. Intact Col-IV in vitro was also examined by western blot analysis. Finally, the changes in blood vessels in the PDL were examined by micro-computed tomography analysis with perfused contrast agents and by conventional histological analysis.

RESULTS

Orthodontic tensile strain induced MMP-12 expression in PDL cells in vivo and in vitro. Immunohistochemistry revealed that MMP-12-positive cells were observed adjacent to the Col-IV-positive tubular area in the tension zone of PDL. MMP-12 in culture supernatant of HPL cells degraded recombinant Col-IV, and specific MMP-12 inhibitor blocked the Col-IV degradation. Micro-computed tomography analysis and conventional histological analysis demonstrated that the areas of blood vessels were increased in the tension zone of the PDL after OTM.

CONCLUSION

We discovered that the orthodontic tensile strain upregulates MMP-12 expression in the tension zone of PDL and induces angiogenesis via degradation of Col-IV in the vascular endothelial basement membrane.

Cancer cell motility: lessons from migration in confined spaces

Time-lapse, deep-tissue imaging made possible by advances in intravital microscopy has demonstrated the importance of tumour cell migration through confining tracks in vivo. These tracks may either be endogenous features of tissues or be created by tumour or tumour-associated cells. Importantly, migration mechanisms through confining microenvironments are not predicted by 2D migration assays. Engineered in vitro models have been used to delineate the mechanisms of cell motility through confining spaces encountered in vivo. Understanding cancer cell locomotion through physiologically relevant confining tracks could be useful in developing therapeutic strategies to combat metastasis.

Role for Mechanotransduction in Macrophage and Dendritic Cell Immunobiology

Tissue homeostasis is not only controlled by biochemical signals but also through mechanical forces that act on cells. Yet, while it has long been known that biochemical signals have profound effects on cell biology, the importance of mechanical forces has only been recognized much more recently. The types of mechanical stress that cells experience include stretch, compression, and shear stress, which are mainly induced by the extracellular matrix, cell-cell contacts, and fluid flow. Importantly, macroscale tissue deformation through stretch or compression also affects cellular function.Immune cells such as macrophages and dendritic cells are present in almost all peripheral tissues, and monocytes populate the vasculature throughout the body. These cells are unique in the sense that they are subject to a large variety of different mechanical environments, and it is therefore not surprising that key immune effector functions are altered by mechanical stimuli. In this chapter, we describe the different types of mechanical signals that cells encounter within the body and review the current knowledge on the role of mechanical signals in regulating macrophage, monocyte, and dendritic cell function.

MicroRNAs as biomarkers in the diagnosis and treatment of chondrosarcoma

MicroRNAs are a group of small non-coding RNAs that play a complex role in post-transcriptional gene expression and can be used for diagnosis, prognosis, and targeted treatment. Despite advances in diagnosis and treatment of chondrosarcoma, its underpinning molecular mechanisms still remain elusive. Given the recent increasing knowledge base of micro RNA (miRNA) roles in neoplasia, both as oncogenes and tumor suppressor genes, this review will focus on discussing the available data on expression profiles and potential roles of miRNA in chondrosarcoma. Accumulating evidence suggests that microRNAs have the potential to be used in the future for clinical management of chondrosarcoma.

Cell Blebbing in Confined Microfluidic Environments

Migrating cells can extend their leading edge by forming myosin-driven blebs and F-actin-driven pseudopods. When coerced to migrate in resistive environments, Dictyostelium cells switch from using predominately pseudopods to blebs. Bleb formation has been shown to be chemotactic and can be influenced by the direction of the chemotactic gradient. In this study, we determine the blebbing responses of developed cells of Dictyostelium discoideum to cAMP gradients of varying steepness produced in microfluidic channels with different confining heights, ranging between 1.7 μm and 3.8 μm. We show that microfluidic confinement height, gradient steepness, buffer osmolarity and Myosin II activity are important factors in determining whether cells migrate with blebs or with pseudopods. Dictyostelium cells were observed migrating within the confines of microfluidic gradient channels. When the cAMP gradient steepness is increased from 0.7 nM/μm to 20 nM/μm, cells switch from moving with a mixture of blebs and pseudopods to moving only using blebs when chemotaxing in channels with confinement heights less than 2.4 μm. Furthermore, the size of the blebs increases with gradient steepness and correlates with increases in myosin-II localization at the cell cortex. Reduction of intracellular pressure by high osmolarity buffer or inhibition of myosin-II by blebbistatin leads to a decrease in bleb formation and bleb size. Together, our data reveal that the protrusion type formed by migrating cells can be influenced by the channel height and the steepness of the cAMP gradient, and suggests that a combination of confinement-induced myosin-II localization and cAMP-regulated cortical contraction leads to increased intracellular fluid pressure and bleb formation.

Prostaglandin I2 upregulates the expression of anterior pharynx-defective-1α and anterior pharynx-defective-1β in amyloid precursor protein/presenilin 1 transgenic mice

Cyclooxygenase‐2 (COX‐2) has been recently identified to be involved in the pathogenesis of Alzheimer's disease (AD). Yet, the role of an important COX‐2 metabolic product, prostaglandin (PG) I₂, in the pathogenesis of AD remains unknown. Using human‐ and mouse‐derived neuronal cells as well as amyloid precursor protein/presenilin 1 (APP/PS1) transgenic mice as model systems, we elucidated the mechanism of anterior pharynx‐defective (APH)‐1α and pharynx‐defective‐1β induction. In particular, we found that PGI₂ production increased during the course of AD development. Then, PGI₂ accumulation in neuronal cells activates PKA/CREB and JNK/c‐Jun signaling pathways by phosphorylation, which results in APH‐1α/1β expression. As PGI₂ is an important metabolic by‐product of COX‐2, its suppression by NS398 treatment decreases the expression of APH‐1α/1β in neuronal cells and APP/PS1 mice. More importantly, β‐amyloid protein (Aβ) oligomers in the cerebrospinal fluid (CSF) of APP/PS1 mice are critical for stimulating the expression of APH‐1α/1β, which was blocked by NS398 incubation. Finally, the induction of APH‐1α/1β was confirmed in the brains of patients with AD. Thus, these findings not only provide novel insights into the mechanism of PGI₂‐induced AD progression but also are instrumental for improving clinical therapies to combat AD.

Time-lapse lens-free imaging of cell migration in diverse physical microenvironments

Time-lapse imaging of biological samples is important for understanding complex (patho)physiological processes. A growing number of point-of-care biomedical assays rely on real-time imaging of flowing or migrating cells. However, the cost and complexity of integrating experimental models simulating physiologically relevant microenvironments with bulky imaging systems that offer sufficient spatiotemporal resolution limit the use of time-lapse assays in research and clinical settings. This paper introduces a compact and affordable lens-free imaging (LFI) device based on the principle of coherent in-line, digital holography for time-lapse cell migration assays. The LFI device combines single-cell resolution (1.2 μm) with a large field of view (6.4 × 4.6 mm(2)), thus rendering it ideal for high-throughput applications and removing the need for expensive and bulky programmable motorized stages. The set-up is so compact that it can be housed in a standard cell culture incubator, thereby avoiding custom-built stage top incubators. LFI is thoroughly benchmarked against conventional live-cell phase contrast microscopy for random cell motility on two-dimensional (2D) surfaces and confined migration on 1D-microprinted lines and in microchannels using breast adenocarcinoma cells. The quality of the results obtained by the two imaging systems is comparable, and they reveal that cells migrate more efficiently upon increasing confinement. Interestingly, assays of confined migration more readily distinguish the migratory potential of metastatic MDA-MB-231 cells from non-metastatic MCF7 cells relative to traditional 2D migration assays. Altogether, this single-cell migration study establishes LFI as an elegant and useful tool for live-cell imaging.

Class 3 semaphorins induce F-actin reorganization in human dendritic cells: Role in cell migration

Class 3 semaphorins (Semas) are soluble proteins that are well recognized for their role in guiding axonal migration during neuronal development. In the immune system, Sema3A has been shown to influence murine dendritic cell (DC) migration by signaling through a neuropilin (NRP)-1/plexin-A1 coreceptor axis. Potential roles for class 3 Semas in human DCs have yet to be described. We tested the hypothesis that Sema3A, -3C, and -3F, each with a unique NRP-1 and/or NRP-2 binding specificity, influence human DC migration. In this report, we find that although NRP-1 and NRP-2 are expressed in human immature DCs (imDCs), NRP-2 expression increases as cells mature further, whereas expression of NRP-1 declines dramatically. Elevated levels of RNA encoding plexin-A1 and -A3 are present in both imDCs and mature DC (mDCs), supporting the relevance of Sema/NRP/plexin signaling pathways in these cells. Sema3A, -3C, and -3F bind to human DCs, with Sema3F binding predominantly through NRP-2. The binding of these Semas leads to reorganization of actin filaments at the plasma membrane and increased transwell migration in the absence or presence of chemokine CCL19. Microfluidic chamber assays failed to demonstrate consistent changes in speed of Sema3C-treated DCs, suggesting increased cell deformability as a possible explanation for enhanced transwell migration. Although monocytes express RNA encoding Sema3A, -3C, and -3F, only RNA encoding Sema3C increases robustly during DC differentiation. These data suggest that Sema3A, -3C, and -3F, likely with coreceptors NRP-1, NRP-2, and plexin-A1 and/or -A3, promote migration and possibly other activities of human DCs during innate and adaptive immune responses.

Engineered Models of Confined Cell Migration

Cells in the body are physically confined by neighboring cells, tissues, and the extracellular matrix. Although physical confinement modulates intracellular signaling and the underlying mechanisms of cell migration, it is difficult to study in vivo. Furthermore, traditional two-dimensional cell migration assays do not recapitulate the complex topographies found in the body. Therefore, a number of experimental in vitro models that confine and impose forces on cells in well-defined microenvironments have been engineered. We describe the design and use of microfluidic microchannel devices, grooved substrates, micropatterned lines, vertical confinement devices, patterned hydrogels, and micropipette aspiration assays for studying cell responses to confinement. Use of these devices has enabled the delineation of changes in cytoskeletal reorganization, cell-substrate adhesions, intracellular signaling, nuclear shape, and gene expression that result from physical confinement. These assays and the physiologically relevant signaling pathways that have been elucidated are beginning to have a translational and clinical impact.

By activating matrix metalloproteinase-7, shear stress promotes chondrosarcoma cell motility, invasion and lung colonization

Interstitial fluid flow and associated shear stress are relevant mechanical signals in cartilage and bone (patho)physiology. However, their effects on chondrosarcoma cell motility, invasion and metastasis have yet to be delineated. Using human SW1353, HS.819.T and CH2879 chondrosarcoma cell lines as model systems, we found that fluid shear stress induces the accumulation of cyclic AMP (cAMP) and interleukin-1β (IL-1β), which in turn markedly enhance chondrosarcoma cell motility and invasion via the induction of matrix metalloproteinase-7 (MMP-7). Specifically, shear-induced cAMP and IL-1β activate PI3-K, ERK1/2 and p38 signaling pathways, which lead to the synthesis of MMP-7 via transactivating NF-κB and c-Jun in human chondrosarcoma cells. Importantly, MMP-7 upregulation in response to shear stress exposure has the ability to promote lung colonization of chondrosarcomas in vivo. These findings offer a better understanding of the mechanisms underlying MMP-7 activation in shear-stimulated chondrosarcoma cells, and provide insights on designing new therapeutic strategies to interfere with chondrosarcoma invasion and metastasis.

Interplay of the physical microenvironment, contact guidance, and intracellular signaling in cell decision making

The peritumoral physical microenvironment consists of complex topographies that influence cell migration. Cell decision making, upon encountering anisotropic, physiologically relevant physical cues, has yet to be elucidated. By integrating microfabrication with cell and molecular biology techniques, we provide a quantitative and mechanistic analysis of cell decision making in a variety of well-defined physical microenvironments. We used MDA-MB-231 breast carcinoma and HT1080 fibrosarcoma as cell models. Cell decision making after lateral confinement in 2-dimensional microcontact printed lines is governed by branch width at bifurcations. Cells confined in narrow feeder microchannels prefer to enter wider branches at bifurcations. In contrast, in feeder channels that are wider than the cell body, cells elongate along one side wall of the channel and are guided by contact with the wall to the contiguous branch channel independent of its width. Knockdown of β1-integrins or inhibition of cellular contractility suppresses contact guidance. Concurrent, but not individual, knockdown of nonmuscle myosin isoforms IIA and IIB also decreases contact guidance, which suggests the existence of a compensatory mechanism between myosin IIA and myosin IIB. Conversely, knockdown or inhibition of cell division control protein 42 homolog promotes contact guidance-mediated decision making. Taken together, the dimensionality, length scales of the physical microenvironment, and intrinsic cell signaling regulate cell decision making at intersections.-Paul, C. D., Shea, D. J., Mahoney, M. R., Chai, A., Laney, V., Hung, W.-C., Konstantopoulos, K. Interplay of the physical microenvironment, contact guidance, and intracellular signaling in cell decision making.

Prostaglandin I₂ Attenuates Prostaglandin E₂-Stimulated Expression of Interferon γ in a β-Amyloid Protein- and NF-κB-Dependent Mechanism

Cyclooxygenase-2 (COX-2) has been recently identified as being involved in the pathogenesis of Alzheimer’s disease (AD). However, the role of an important COX-2 metabolic product, prostaglandin (PG) I₂, in AD development remains unknown. Using mouse-derived astrocytes as well as APP/PS1 transgenic mice as model systems, we firstly elucidated the mechanisms of interferon γ (IFNγ) regulation by PGE₂ and PGI₂. Specifically, PGE₂ accumulation in astrocytes activated the ERK1/2 and NF-κB signaling pathways by phosphorylation, which resulted in IFNγ expression. In contrast, the administration of PGI₂ attenuated the effects of PGE₂ on stimulating the production of IFNγ via inhibiting the translocation of NF-κB from the cytosol to the nucleus. Due to these observations, we further studied these prostaglandins and found that both PGE₂ and PGI₂ increased Aβ_1–42 levels. In detail, PGE₂ induced IFNγ expression in an Aβ_1–42-dependent manner, whereas PGI₂-induced Aβ_1–42 production did not alleviate cells from IFNγ inhibition by PGI₂ treatment. More importantly, our data also revealed that not only Aβ_1–42 oligomer but also fibrillar have the ability to induce the expression of IFNγ via stimulation of NF-κB nuclear translocation in astrocytes of APP/PS1 mice. The production of IFNγ finally accelerated the deposition of Aβ_1–42 in β-amyloid plaques.

Megakaryocytic Maturation in Response to Shear Flow Is Mediated by the Activator Protein 1 (AP-1) Transcription Factor via Mitogen-activated Protein Kinase (MAPK) Mechanotransduction

Megakaryocytes (MKs) are exposed to shear flow as they migrate from the bone marrow hematopoietic compartment into circulation to release pro/preplatelets into circulating blood. Shear forces promote DNA synthesis, polyploidization, and maturation in MKs, and platelet biogenesis. To investigate mechanisms underlying these MK responses to shear, we carried out transcriptional analysis on immature and mature stem cell-derived MKs exposed to physiological shear. In immature (day (d)9) MKs, shear exposure up-regulated genes related to growth and MK maturation, whereas in mature (d12) MKs, it up-regulated genes involved in apoptosis and intracellular transport. Following shear-flow exposure, six activator protein 1 (AP-1) transcripts (ATF4,JUNB,JUN,FOSB,FOS, andJUND) were up-regulated at d9 and two AP-1 proteins (JunD and c-Fos) were up-regulated both at d9 and d12. We show that mitogen-activated protein kinase (MAPK) signaling is linked to both the shear stress response and AP-1 up-regulation. c-Jun N-terminal kinase (JNK) phosphorylation increased significantly following shear stimulation, whereas JNK inhibition reduced shear-induced JunD expression. Although p38 phosphorylation did not increase following shear flow, its inhibition reduced shear-induced JunD and c-Fos expression. JNK inhibition reduced fibrinogen binding and P-selectin expression of d12 platelet-like particles (PLPs), whereas p38 inhibition reduced fibrinogen binding of d12 PLPs. AP-1 expression correlated with increased MK DNA synthesis and polyploidization, which might explain the observed impact of shear on MKs. To summarize, we show that MK exposure to shear forces results in JNK activation, AP-1 up-regulation, and downstream transcriptional changes that promote maturation of immature MKs and platelet biogenesis in mature MKs.

The role of cyclooxygenase-2, interleukin-1β and fibroblast growth factor-2 in the activation of matrix metalloproteinase-1 in sheared-chondrocytes and articular cartilage

MMP-1 expression is detected in fluid shear stress (20 dyn/cm²)-activated and osteoarthritic human chondrocytes, however, the precise mechanisms underlying shear-induced MMP-1 synthesis remain unknown. Using primary chondrocytes and T/C-28a2 chondrocytic cells as model systems, we report that prolonged application of high fluid shear to human chondrocytes induced the synthesis of cyclooxygenase-2 (COX-2), interleukin-1β (IL-1β) and fibroblast growth factor-2 (FGF-2), which led to a marked increase in MMP-1 expression. IL-1β, COX-2-dependent PGE₂ activated the PI3-K/AKT and p38 signaling pathways, which were in turn responsible for MMP-1 synthesis via NF-κB- and c-Jun-transactivating pathways. Prolonged shear stress exposure (>12 h) induced 15-Deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) synthesis. Although 15d-PGJ₂ suppressed PI3-K/AKT and p38 signaling pathways, it stimulated MMP-1 expression via activating heme oxygenase 1 (HO-1). The critical role of COX-2 in regulating MMP-1 expression in articular cartilage in vivo was demonstrated using COX-2^+/− transgenic mice in the absence or presence of rofecoxib oral administration. These findings provide novel insights for developing therapeutic strategies to combat OA.