Dual effects of the membrane-anchored MMP regulator RECK on chondrogenic differentiation of ATDC5 cells

RECK as a Potential Crucial Molecule for the Targeted Treatment of Sepsis

Reversion inducing cysteine rich protein with kazal motifs (RECK), a Kazal motif-containing protein, regulates pro-inflammatory cytokines production, migration of inflammatory cells, vascular endothelial growth factor (VEGF) and Wnt pathways and plays critical roles in septic inflammatory storms and vascular endothelial dysfunction. Recently, RECK has been defined as the negative regulator of adisintegrin and metalloproteinases (ADAMs) and matrix metalloproteinases (MMPs), which are both membrane "molecular scissors" and aggravate the poor prognosis of sepsis. To better understand the roles of RECK and the related mechanisms, we make here a systematic and in-depth review of RECK. We first summarize the findings on structural characteristics of RECK protein and the regulation at the transcription, post-transcription, or protein level of RECK. Then, we discuss the roles of RECK in inflammation, infection, and vascular injury by focusing on the RECK function on ADAMs and MMPs, as well as the pathways of VEGF, WNT, angiopoietin, and notch signaling. In conclusion, RECK participation as a guardian in the development of sepsis provides insight into the strategies of precisely intervening in RECK dysregulationfor the treatment of sepsis.

Eurycomanone inhibits osteosarcoma growth and metastasis by suppressing GRP78 expression

ETHNOPHARMACOLOGICAL RELEVANCE

Osteosarcoma (OS) is characterized by rapid growth and frequent pulmonary metastasis. Eurycoma longifolia Jack, a flowering plant primarily found in Southeast Asian countries, is commonly used in traditional herbal medicine. Its root extract is mainly used for against cancer, malaria, parasites and other conditions. The active compound in its root extract, eurycomanone (EUR), has been proven to inhibit lung and liver cancer proliferation.

AIM OF THE STUDY

Our research aimed to investigate the inhibitory effect and underlying molecular mechanism of EUR on OS growth and metastasis.

MATERIALS AND METHODS

In vitro experiments: western blotting (WB) screened 41 compounds that inhibited GRP78 expression and evaluated the protein levels of GRP78, PARP, cleaved-PARP, MMP2, and MMP9. Cell proliferation was evaluated using CCK-8, EdU, colony formation assay, and cell apoptosis was assessed by flow cytometry. Transwell, wound healing, and tube formation assays were performed to determine the effect of EUR on tumor invasion, migration, and angiogenesis, respectively. Quantitative real-time polymerase chain (qRT-PCR) and dual-luciferase activity assays detected GRP78 mRNA stability and transcription levels post-EUR and thapsigargin treatment. RNA-Seq identified signaling pathways inhibited by EUR. In vivo experiments: effects of EUR in mice were evaluated by H&E staining to detect lung metastasis and potential toxic effects in tissues. Immunohistochemical (IHC) staining detected the expression of Ki-67, CD31, and cleaved caspase-3 in tumors.

RESULTS

GRP78 is highly expressed in OS and correlated with poor prognosis. In vitro, eurycomanone (EUR) significantly downregulated GRP78 expression, inhibited cell proliferation, migration, invasion, tube formation, and induced apoptosis. Moreover, it enhanced trichostatin A (TSA) sensitivity and exhibited inhibitory effects on other cancer types. Mechanistically, EUR decreased GRP78 mRNA stability and transcription. In vivo, EUR inhibited proliferation and invasion in tibial and PDX models.

CONCLUSIONS

Our study demonstrated that EUR inhibits the growth and metastasis of OS by reducing GRP78 mRNA stability and inhibiting its transcription, which offers a novel approach for clinical treatment of OS.

Loss of MMP9 disturbs cranial suture fusion via suppressing cell proliferation, chondrogenesis and osteogenesis in mice

Cranial sutures function as growth centers for calvarial bones. Abnormal suture closure will cause permanent cranium deformities. MMP9 is a member of the gelatinases that degrades components of the extracellular matrix. MMP9 has been reported to regulate bone development and remodeling. However, the function of MMP9 in cranial suture development is still unknown. Here, we identified that the expression of Mmp9 was specifically elevated during fusion of posterior frontal (PF) suture compared with other patent sutures in mice. Interestingly, inhibition of MMP9 ex vivo or knockout of Mmp9 in mice (Mmp9-/-) disturbed the fusion of PF suture. Histological analysis showed that knockout of Mmp9 resulted in wider distance between osteogenic fronts, suppressed cell condensation and endocranial bone formation in PF suture. Proliferation, chondrogenesis and osteogenesis of suture cells were decreased in Mmp9-/- mice, leading to the PF suture defects. Moreover, transcriptome analysis of PF suture revealed upregulated ribosome biogenesis and downregulated IGF signaling associated with abnormal closure of PF suture in Mmp9-/- mice. Inhibition of the ribosome biogenesis partially rescued PF suture defects caused by Mmp9 knockout. Altogether, these results indicate that MMP9 is critical for the fusion of cranial sutures, thus suggesting MMP9 as a potential therapeutic target for cranial suture diseases.

TBC1D1 represses glioma progression by altering the integrity of the cytoskeleton

BACKGROUND

Glioma is one of the most aggressive malignant brain tumors and is characterized by invasive growth and poor prognosis. TBC1D1, a member of the TBC family, is associated with the development of various malignancies. However, the role of TBC1D1 in glioma-genesis remains unclear.

METHODS

The effect of TBC1D1 on the prognosis of glioma patients and related influencing factors were analyzed in the Chinese Glioma Genome Atlas (CGGA) and The Cancer Genome Atlas (TCGA) databases. Expression of TBC1D1 in glioma cell lines was detected by western blotting. Cell viability and proliferation were measured by EdU and Colony formation assays, respectively. Transwell and wound healing assays were performed to determine the cell migration and invasion capacities. Immunofluorescence was used to observe actin morphology in the cytoskeleton.

RESULTS

We discovered that high TBC1D1 expression in gliomas led to poor prognosis. Downregulation of TBC1D1 in glioma cells significantly inhibited multiple important functions, such as proliferation, migration, and invasion. We further demonstrated that the tumor-inhibitory effect of TBC1D1 might occur through the P-LIMK/cofilin pathway, destroying the cytoskeletal structure and affecting the depolymerization of F-actin, thereby inhibiting glioma migration.

CONCLUSION

TBC1D1 affects the balance and integrity of the actin cytoskeleton via cofilin, thereby altering the morphology and aggressiveness of glioma cells. This study provides a new perspective on its role in tumorigenesis, thereby identifying a potential therapeutic target for the treatment of gliomas.

Radical-Scavenging and Subchondral Bone-Regenerating Nanomedicine for Osteoarthritis Treatment

Osteoarthritis (OA) is characterized by cartilage degradation and subchondral bone remodeling. However, most available studies focus on either cartilage degradation or subchondral bone lesion, alone, and rarely pay attention to the synergy of these two pathological changes. Herein, a dual-functional medication is developed to simultaneously protect cartilage and achieve subchondral bone repair. Black phosphorus nanosheets (BPNSs), with a strong reactive oxygen species (ROS)-scavenging capability and high biocompatibility, also present a notable promoting effect in osteogenesis. BPNSs efficiently eliminate the intracellular ROS and, thus, protect the inherent homeostasis between cartilage matrix anabolism and catabolism. RNA sequencing results of BPNSs-treated OA chondrocytes further reveal the restoration of chondrocyte function, activation of antioxidant enzymes, and regulation of inflammation. Additional in vivo assessments solidly confirm that BPNSs inhibit cartilage degradation and prevent OA progression. Meanwhile, histological evaluation and microcomputed tomography (micro-CT) scanning analysis verify the satisfying disease-modifying effects of BPNSs on OA. Additionally, the excellent biocompatibility of BPNSs enables them as a competitive candidate for OA treatment. This distinct disease-modifying treatment of OA on the basis of BPNSs provides an insight and paradigm on the dual-functional treatment strategy focusing on both cartilage degradation and subchondral bone lesion in OA and explores a broader biomedical application of BPNS nanomedicine in orthopedics.

Within or Without You? A Perspective Comparing In Situ and Ex Situ Tissue Engineering Strategies for Articular Cartilage Repair

Human articular cartilage has a poor ability to self-repair, meaning small injuries often lead to osteoarthritis, a painful and debilitating condition which is a major contributor to the global burden of disease. Existing clinical strategies generally do not regenerate hyaline type cartilage, motivating research toward tissue engineering solutions. Prospective cartilage tissue engineering therapies can be placed into two broad categories: i) Ex situ strategies, where cartilage tissue constructs are engineered in the lab prior to implantation and ii) in situ strategies, where cells and/or a bioscaffold are delivered to the defect site to stimulate chondral repair directly. While commonalities exist between these two approaches, the core point of distinction-whether chondrogenesis primarily occurs "within" or "without" (outside) the body-can dictate many aspects of the treatment. This difference influences decisions around cell selection, the biomaterials formulation and the surgical implantation procedure, the processes of tissue integration and maturation, as well as, the prospects for regulatory clearance and clinical translation. Here, ex situ and in situ cartilage engineering strategies are compared: Highlighting their respective challenges, opportunities, and prospects on their translational pathways toward long term human cartilage repair.

Differentiation of Induced Pluripotent Stem Cells Into Chondrocytes: Methods and Applications for Disease Modeling and Drug Discovery

Induced pluripotent stem cell (iPSC) technology allows pathomechanistic and therapeutic investigation of human heritable disorders affecting tissue types whose collection from patients is difficult or even impossible. Among them are cartilage diseases. Over the past decade, iPSC-chondrocyte disease models have been shown to exhibit several key aspects of known disease mechanisms. Concurrently, an increasing number of protocols to differentiate iPSCs into chondrocytes have been published, each with its respective (dis)advantages. In this review we provide a comprehensive overview of the different differentiation approaches, the hitherto described iPSC-chondrocyte disease models and mechanistic and/or therapeutic insights that have been derived from their investigation, and the current model limitations. Key lessons are that the most appropriate differentiation approach is dependent upon the cartilage disease under investigation and that further optimization is still required to recapitulate the in vivo cartilage. © 2022 American Society for Bone and Mineral Research (ASBMR).

Impact of Reck expression and promoter activity in neuronal in vitro differentiation

Reck (REversion-inducing Cysteine-rich protein with Kazal motifs) tumor suppressor gene encodes a multifunctional glycoprotein which inhibits the activity of several matrix metalloproteinases (MMPs), and has the ability to modulate the Notch and canonical Wnt pathways. Reck-deficient neuro-progenitor cells undergo precocious differentiation; however, modulation of Reck expression during progression of the neuronal differentiation process is yet to be characterized. In the present study, we demonstrate that Reck expression levels are increased during in vitro neuronal differentiation of PC12 pheochromocytoma cells and P19 murine teratocarcinoma cells and characterize mouse Reck promoter activity during this process. Increased Reck promoter activity was found upon induction of differentiation in PC12 cells, in accordance with its increased mRNA expression levels in mouse in vitro models. Interestingly, Reck overexpression, prior to the beginning of the differentiation protocol, led to diminished efficiency of the neuronal differentiation process. Taken together, our findings suggest that increased Reck expression at early stages of differentiation diminishes the number of neuron-like cells, which are positive for the beta-3 tubulin marker. Our data highlight the importance of Reck expression evaluation to optimize in vitro neuronal differentiation protocols.

Sclerostin inhibits interleukin-1β-induced late stage chondrogenic differentiation through downregulation of Wnt/β-catenin signaling pathway

It is known that Wnt/β-catenin signaling induces endochondral ossification and plays a significant role in the pathophysiology of osteoarthritis (OA). Sclerostin is a potent inhibitor of the Wnt/β-catenin signaling pathway. This study investigated the role of sclerostin in the endochondral differentiation under an OA-like condition induced by proinflammatory cytokines. ATDC5 cells were used to investigate chondrogenic differentiation and terminal calcification, and 10 ng/ml IL-1β and/or 200 ng/ml sclerostin were added to the culture medium. IL-1β impaired early chondrogenesis from undifferentiated state into proliferative chondrocytes, and it was not altered by sclerostin. IL-1β induced progression of chondrogenic differentiation in the late stage and promoted terminal calcification. These processes were inhibited by sclerostin and chondrogenic phenotype was restored. In addition, sclerostin restored IL-1β-induced upregulation of Wnt/β-catenin signaling in the late stage. This study provides insights into the possible role of sclerostin in the chondrogenic differentiation under the IL-1β-induced OA-like environment. Suppression of Wnt signaling by an antagonist may play a key role in the maintenance of articular homeostasis and has a potential to prevent the progression of OA. Thus, sclerostin is a candidate treatment option for OA.

Abundant expression of the membrane-anchored protease-regulator RECK in the anterior pituitary gland and its implication in the growth hormone/insulin-like growth factor 1 axis in mice

The tumor suppressor gene Reversion-inducing cysteine-rich protein with Kazal motifs (Reck) encodes a membrane-anchored protease regulator expressed in multiple tissues in mouse embryos and is essential for embryonic development. In postnatal mice, however, physiological roles for the RECK protein remain unclear. We found in this study that Reck is abundantly expressed in growth hormone (GH)-producing cells (somatotrophs) in the anterior pituitary gland (AP). We also found that two types of viable Reck mutant mice, one with reduced RECK expression (Hypo mice) and the other with induced Reck deficiency from 10 days after birth (iKO mice treated with tamoxifen), exhibit common phenotypes including decreases in body size and plasma levels of insulin-like growth factor-1 (IGF1). To gain insights into the function of RECK in the AP, we characterized several somatotroph-associated molecules in the AP of these mice. Immunoreactivity of GH was greatly reduced in tamoxifen-treated iKO mice; in these mice, two membrane receptors involved in the stimulation of GH secretion [growth hormone secretagogue receptor (GHSR) and growth hormone releasing hormone receptor (GHRHR)] were decreased, however, their mRNAs were increased. Decrease in GHSR immunoreactivity and concomitant increase in its mRNA were also found in the other mutant line, Hypo. Furthermore, reduced immunoreactivity of growth hormone receptor (GHR) and concomitant increase in its mRNA was also found in the liver of Hypo mice. These results raise the possibility that RECK supports proper functioning of the GH/IGF1 axis in mice, thereby affecting their growth and metabolism.

Eupatilin inhibits glioma proliferation, migration, and invasion by arresting cell cycle at G1/S phase and disrupting the cytoskeletal structure

Purpose: Eupatilin is a pharmacologically active flavonoid extracted from Asteraceae argyi that has been identified as having antitumor effects. Gliomas are the most common intracranial malignant tumors and are associated with high mortality and a poor postoperative prognosis. There are few studies on the therapeutic effects of eupatilin on glioma. Therefore, we explored the efficacy and the underlying molecular mechanism of eupatilin on glioma.

Methods: The effect of eupatilin on cell proliferation and viability was detected using Cell Counting Kit-8 assays. Cell migration was analyzed with a scratch wound healing assay and invasion was analyzed using transwell assays.

Results: We found that eupatilin significantly inhibits the viability and proliferation of glioma cells by arresting the cell cycle at the G1/S phase. In addition, eupatilin disrupts the structure of the cytoskeleton and affects F-actin depolymerization via the “P-LIMK”/cofilin pathway, thereby inhibiting the migration of glioma. We also found that eupatilin inhibits the invasion of gliomas. The underlying mechanism may be related to the destruction of epithelial–mesenchymal transition, with eupatilin also affecting the RECK/matrix metalloproteinase pathway. However, we did not observe the proapoptotic effect of eupatilin on glioma, which is inconsistent with other studies. Finally, we observed a significant inhibitory effect of eupatilin on U87MG glioma in xenograft nude mice.

Conclusion: Eupatilin inhibits the viability and proliferation of glioma cells, attenuates the migration and invasion, and inhibits tumor growth in vivo, but does not promote apoptosis. Therefore, due to the poor clinical efficacy of drug treatment of glioma and high drug resistance, the emergence of eupatilin brings a new dawn for glioma patients.

Sclerostin is upregulated in the early stage of chondrogenic differentiation, but not required in endochondral ossification in vitro

Sclerostin is a potent inhibitor of the canonical Wnt signaling pathway. Wnt signaling pathways have multiple roles in the regulation of cartilage development, growth, and maintenance. This study focused on the role of sclerostin in the process of chondrogenic differentiation. We hypothesized that sclerostin is essential to induce chondrogenic differentiation and regulate endochondral ossification. ATDC5 cells were used to investigate chondrogenic differentiation and terminal calcification. During chondrogenic differentiation, intrinsic sclerostin was upregulated in the early stage, but downregulated in the late stage. Addition of sclerostin elevated expressions of Sox9 and Col2a1 (P<0.05) and reduced expressions of Runx2, Col10a1, MMP-3, MMP-13, and ADAMTS5 (P<0.05) through inhibition of the Wnt-β-catenin signaling pathway (P<0.05). Terminal calcification was significantly inhibited by sclerostin (P<0.05). In contrast, deletion of sclerostin decreased expressions of Sox9 and Col2a1 (P<0.05), increased expressions of Runx2, Col10a1, MMP-3, and MMP-13 (P<0.05), and promoted terminal calcification (P<0.05). This study provides insights into the possible role of sclerostin in the regulation of chondrogenic differentiation. Sclerostin is upregulated in the early stage of chondrogenic differentiation, but is not required in endochondral ossification. Sclerostin is a candidate modulator for chondrogenic differentiation.

Extracellular matrix dynamics during mesenchymal stem cells differentiation

Mesenchymal stem cells (MSCs) are stromal cells that display self-renewal and multipotent differentiation capacity. The repertoire of mature cells generated ranges but is not restricted to: fat, bone and cartilage. Their potential importance for both cell therapy and maintenance of in vivo homeostasis is indisputable. Nonetheless, both their in vivo identity and use in cell therapy remain elusive. A drawback generated by this fact is that little is known about the MSC niche and how it impacts differentiation and homeostasis maintenance. Hence, the roles played by the extracellular matrix (ECM) and its main regulators namely: the Matrix Metalloproteinases (MMPs) and their counteracting inhibitors (TIMPs and RECK) upon stem cells differentiation are only now beginning to be unveiled. Here, we will focus on mesenchymal stem cells and review the main mechanisms involved in adipo, chondro and osteogenesis, discussing how the extracellular matrix can impact not only lineage commitment, but, also, their survival and potentiality. This review critically analyzes recent work in the field in an effort towards a better understanding of the roles of Matrix Metalloproteinases and their inhibitors in the above-cited events.

Generation and characterization of a mouse line carrying Reck-CreERT2 knock-in allele

Reck encodes a membrane-anchored glycoprotein implicated in the regulation of extracellular metalloproteinases, Notch-signaling, and Wnt7-signaling and shown to play critical roles in embryogenesis and tumor suppression. Precise mechanisms of its actions in vivo, however, remain largely unknown. By homologous recombination, we generated a new Reck allele, Reck^CreERT2 (MGI symbol: Reck<tm3.1(cre/ERT2)Noda>). This allele is defective in terms of Reck function but expected to induce loxP-mediated recombination in the cells committed to express Reck. Similarity in the expression patterns of the Reck^CreERT2 transgene and the endogenous Reck gene was confirmed in five tissues. In the adult hippocampus, induction of Reck expression after transient cerebral ischemia could be demonstrated using this allele. These results indicate the utility of this Cre-driver allele in further studies.

Effects of matrix metalloproteinases on the fate of mesenchymal stem cells

Mesenchymal stem cells (MSCs) have great potential as a source of cells for cell-based therapy because of their ability for self-renewal and differentiation into functional cells. Moreover, matrix metalloproteinases (MMPs) have a critical role in the differentiation of MSCs into different lineages. MSCs also interact with exogenous MMPs at their surface, and regulate the pericellular localization of MMP activities. The fate of MSCs is regulated by specific MMPs associated with a key cell lineage. Recent reports suggest the integration of MMPs in the differentiation, angiogenesis, proliferation, and migration of MSCs. These interactions are not fully understood and warrant further investigation, especially for their application as therapeutic tools to treat different diseases. Therefore, overexpression of a single MMP or tissue-specific inhibitor of metalloproteinase in MSCs may promote transdifferentiation into a specific cell lineage, which can be used for the treatment of some diseases. In this review, we critically discuss the identification of various MMPs and the signaling pathways that affect the differentiation, migration, angiogenesis, and proliferation of MSCs.

Enhancement of Matrix Metalloproteinase-2 (MMP-2) as a Potential Chondrogenic Marker during Chondrogenic Differentiation of Human Adipose-Derived Stem Cells

Human adipose-derived stem cells (hASCs) have a capacity to undergo adipogenic, chondrogenic, and osteogenic differentiation. Recently, hASCs were applied to various fields including cell therapy for tissue regeneration. However, it is hard to predict the direction of differentiation of hASCs in real-time. Matrix metalloproteinases (MMPs) are one family of proteolytic enzymes that plays a pivotal role in regulating the biology of stem cells. MMPs secreted by hASCs are expected to show different expression patterns depending on the differentiation state of hASCs because biological functions exhibit different patterns during the differentiation of stem cells. Here, we investigated proteolytic enzyme activity, especially MMP-2 activity, in hASCs during their differentiation. The activities of proteolytic enzymes and MMP-2 were higher during chondrogenic differentiation than during adipogenic and osteogenic differentiation. During chondrogenic differentiation, mRNA expression of MMP-2 and the level of the active form of MMP-2 were increased, which also correlated with Col II. It is concluded that proteolytic enzyme activity and the level of the active form of MMP-2 were increased during chondrogenic differentiation, which was accelerated in the presence of Col II protein. According to our findings, MMP-2 could be a candidate maker for real-time detection of chondrogenic differentiation of hASCs.

MiR-324-5p Suppresses Hepatocellular Carcinoma Cell Invasion by Counteracting ECM Degradation through Post-Transcriptionally Downregulating ETS1 and SP1

Hepatocellular carcinoma (HCC) is one of the common malignancies, which is highly metastatic and the third common cause of cancer deaths in the world. The invasion and metastasis of cancer cells is a multistep and complex process which is mainly initiated by extracellular matrix (ECM) degradation. Aberrant expression of microRNA has been investigated in HCC and shown to play essential roles during HCC progression. In the present study, we found that microRNA-324-5p (miR-324-5p) was downregulated in both HCC cell lines and tissues. Ectopic miR-324-5p led to the reduction of HCC cells invasive and metastatic capacity, whereas inhibition of miR-324-5p promoted the invasion of HCC cells. Matrix metalloproteinase 2 (MMP2) and MMP9, the major regulators of ECM degradation, were found to be downregulated by ectopic miR-324-5p, while upregulated by miR-324-5p inhibitor. E26 transformation-specific 1 (ETS1) and Specificity protein 1 (SP1), both of which could modulate MMP2 and MMP9 expression and activity, were presented as the direct targets of and downregulated by miR-324-5p. Downregulation of ETS1 and SP1 mediated the inhibitory function of miR-324-5p on HCC migration and invasion. Our study demonstrates that miR-324-5p suppresses hepatocellular carcinoma cell invasion and might provide new clues to invasive HCC therapy.

Bone tissue remodeling and development: focus on matrix metalloproteinase functions

Bone-forming cells originate from distinct embryological layers, mesoderm (axial and appendicular bones) and ectoderm (precursor of neural crest cells, which mainly form facial bones). These cells will develop bones by two principal mechanisms: intramembranous and endochondral ossification. In both cases, condensation of multipotent mesenchymal cells occurs, at the site of the future bone, which differentiate into bone and cartilage-forming cells. During long bone development, an initial cartilaginous template is formed and replaced by bone in a coordinated and refined program involving chondrocyte proliferation and maturation, vascular invasion, recruitment of adult stem cells and intense remodeling of cartilage and bone matrix. Matrix metalloproteinases (MMPs) are the most important enzymes for cleaving structural components of the extracellular matrix (ECM), as well as other non-ECM molecules in the ECM space, pericellular perimeter and intracellularly. Thus, the bioactive molecules generated act on several biological events, such as development, tissue remodeling and homeostasis. Since the discovery of collagenase in bone cells, more than half of the MMP members have been detected in bone tissues under both physiological and pathological conditions. Pivotal functions of MMPs during development and bone regeneration have been revealed by knockout mouse models, such as chondrocyte proliferation and differentiation, osteoclast recruitment and function, bone modeling, coupling of bone resorption and formation (bone remodeling), osteoblast recruitment and survival, angiogenesis, osteocyte viability and function (biomechanical properties); as such alterations in MMP function may alter bone quality. In this review, we look at the principal properties of MMPs and their inhibitors (TIMPs and RECK), provide an up-date on their known functions in bone development and remodeling and discuss their potential application to Bone Bioengineering.

Sox9 reprogrammed dermal fibroblasts undergo hypertrophic differentiation in vitro and trigger endochondral ossification in vivo

Strategies for bone regeneration are undergoing a paradigm shift, moving away from the replication of end-stage bone tissue and instead aiming to recapture the initial events of fracture repair. Although this is known to resemble endochondral bone formation, chondrogenic cell types with favorable proliferative and hypertrophic differentiation properties are lacking. Recent advances in cellular reprogramming have allowed the creation of alternative cell populations with specific properties through the forced expression of transcription factors. Herein, we investigated the in vitro hypertrophic differentiation and in vivo tissue formation capacity of induced chondrogenic cells (iChon cells) obtained through direct reprogramming. In vitro hypertrophic differentiation was detected in iChon cells that contained a doxycycline-inducible expression system for Klf4, cMyc, and Sox9. Furthermore, endochondral bone formation was detected after implantation in nude mice. The bone tissue was derived entirely from host origin, whereas cartilage tissue contained cells from both host and donor. The results obtained highlight the promise of cellular reprogramming for the creation of functional skeletal cells that can be used for novel bone healing strategies.

S100A8/A9 regulates MMP-2 expression and invasion and migration by carcinoma cells

Intracellular calprotectin (S100A8/A9) functions in the control of the cell cycle checkpoint at G2/M. Dysregulation of S100A8/A9 appears to cause loss of the checkpoint, which frequently characterizes head and neck squamous cell carcinoma (HNSCC). In the present study, we analyzed carcinoma cells for other S100A8/A9-directed changes in malignant phenotype. Using a S100A8/A9-negative human carcinoma cell line (KB), transfection to express S100A8 and S100A9 caused selective down-regulation of MMP-2 and inhibited in vitro invasion and migration. Conversely, silencing of endogenous S100A8 and S100A9 expression in TR146 cells, a well-differentiated HNSCC cell line, increased MMP-2 activity and in vitro invasion and migration. When MMP-2 expression was silenced, cells appeared to assume a less malignant phenotype. To more closely model the architecture of cell growth in vivo, cells were grown in a 3D collagen substrate, which was compared to 2D. Growth on 3D substrates caused greater MMP-2 expression. Whereas hypermethylation of CpG islands occurs frequently in HNSCC, S100A8/A9-dependent regulation of MMP-2 could not be explained by modification of the upstream promoters of MMP2 or TIMP2. Collectively, these results suggest that intracellular S100A8/A9 contributes to the cancer cell phenotype by modulating MMP-2 expression and activity to regulate cell migration and mobility.

E-cadherin-downregulation and RECK-upregulation are coupled in the non-malignant epithelial cell line MCF10A but not in multiple carcinoma-derived cell lines

Expression of a mesenchymal phenotype is often associated with invasive/metastatic behaviors of carcinoma cells. Acquisition of a mesenchymal phenotype by a carcinoma cell is known as epithelial-mesenchymal transition (EMT). The membrane-anchored matrix metalloproteinase-regulator RECK is abundant in normal mesenchymal cells. In aggressive carcinomas, however, RECK expression is often downregulated. This apparent paradox prompted us to clarify the relationship between EMT and RECK. We found that TGFβ-induced E-cadherin downregulation, a hallmark of EMT, is accompanied by RECK-upregulation in a non-tumorigenic epithelial cell line (MCF10A). In contrast, the loss of E-cadherin expression is uncoupled from RECK-upregulation in carcinoma-derived cell lines (MCF7, MDA-MB-231, and A549). When RECK was artificially expressed in A549 cells, it showed little effect on EMT but elevated the level of integrin α5 and attenuated cell proliferation and migration. These findings implicate RECK in the regulation of proliferation and migration of normal epithelial cells after EMT and suggest how the uncoupling between EMT and RECK-upregulation impacts on the fates and behaviors of carcinoma cells.

Estrogen suppresses expression of the matrix metalloproteinase inhibitor reversion-inducing cysteine-rich protein with Kazal motifs (RECK) within the mouse uterus

RECK (reversion-inducing cysteine-rich protein with Kazal motifs) is a membrane-anchored glycoprotein which regulates MMP2 and MMP9 activity and has been proposed to play a role in embryo implantation while misexpression of RECK has been associated with a variety of carcinomas. Unfortunately, understanding on the steroidal regulation of uterine RECK is lacking. To address this gap in our knowledge, we examined steroidal regulation and cellular expression of Reck mRNA and protein within the mouse uterus in vivo. Uterine Reck mRNA and protein were decreased by estrogen, while progesterone alone had no effect. The estrogen-induced down regulation could be partially blocked by progesterone. RECK was localized primarily to luminal and glandular epithelial cells and the level of expression was regulated in a similar fashion as in whole tissue by the steroids. Knock-down of endogenous RECK in human endometrial epithelial and stromal cells resulted in a significant increase in active MMP9 expression but not that of pro-MMP9 or MMP2. These studies demonstrate that RECK expression in the mouse uterus is steroidally regulated and that within endometrial epithelial and stromal cells, RECK regulates MMP9, but not MMP2 activity.

Knockdown of glucose-regulated protein 78 decreases the invasion, metalloproteinase expression and ECM degradation in hepatocellular carcinoma cells

Background

We have reported previously that overexpression of glucose-regulated protein 78 (GRP78) promotes the invasion of hepatocellular carcinoma. However, whether GRP78 knockdown affects the extracellular matrix degradation has not been elucidated. Here we are going to determine whether GRP78 knockdown affect the ECM degradation and the role of MMP-2 and MMP-9 in these process in hepatocellular carcinoma cells.

Methods

Human hepatocellular carcinoma cell line SMMC7721 and HepG2 were cultured in DMEM supplemented with 10% FBS, RT-PCR and western blot were used to detect the endogenous expression of GRP78, MMP-2, MMP-9 and TIMP-2 in SMMC7721 and HepG2. GRP78 shRNAs were transfected using lipofection2000. Transwell assay and wound healing assay were used to analyze the invasion of each transfectant. Gelatin zymography and FITC-gelatin degradation assay were employed to investigate the capabilities of ECM degradation of each transfectant. MTT assay was used to determine the proliferation status. Western blot was employed to detect the expression of matrix metalloproteinase 2(MMP-2), MMP-9, MMP-14, and tissue inhibitor of metalloproteinases 2(TIMP-2), focal adhesion kinase (FAK), ERK1/2, JNK and Src.

Results

According to the expression levels of GRP78, MMP-2, MMP-9, MMP-14 and TIMP-1 in hepatocellular carcinoma cell lines SMMC7721 and hepG2, we used SMMC7721 as the in vitro invasion model for further functional analysis. Using this model, we found that GRP78 knockdown decreased the invasion of tumor cells, and this inhibitory effect was independent of cell proliferation. In hepatocellular carcinoma cells, Grp78 knockdown inhibited ECM degradation and the decreased activity and expression of MMP-2, but not MMP-9 contributed largely to this impact. Further analysis revealed that the decreased activity and expression of MMP-2 is mediated by JNK.

Conclusion

Knockdown of GRP78 decreases ECM degradation, and downregulates the expression and activity of MMP-2 and TIMP-2. These results further demonstrate that GRP78 is a potential target for inhibiting the invasion of hepatocellular carcinoma cells.

The transformation suppressor gene Reck is required for postaxial patterning in mouse forelimbs

The membrane-anchored metalloproteinase-regulator RECK has been characterized as a tumor suppressor. Here we report that mice with reduced Reck-expression show limb abnormalities including right-dominant, forelimb-specific defects in postaxial skeletal elements. The forelimb buds of low-Reck mutants have an altered dorsal ectoderm with reduced Wnt7a and Igf2 expression, and hypotrophy in two signaling centers (i.e., ZPA and AER) that are essential for limb outgrowth and patterning. Reck is abundantly expressed in the anterior mesenchyme in normal limb buds; mesenchyme-specific Reck inactivation recapitulates the low-Reck phenotype; and some teratogens downregulate Reck in mesenchymal cells. Our findings illustrate a role for Reck in the mesenchymal-epithelial interactions essential for mammalian development.

Involvement of the SKP2-p27(KIP1) pathway in suppression of cancer cell proliferation by RECK

The membrane-anchored matrix metalloproteinase-regulator RECK is often downregulated in cancers; in some cases, a significant correlation between the level of residual RECK in resected tumors and patient survival has been noted. Furthermore, restoration of RECK expression in certain cancer-derived cell lines results in reduced tumorigenicity. Here we report that acute RECK expression in colon carcinoma cells results in cell cycle-arrest accompanied by downregulation of a ubiquitin ligase component, S-phase kinase-associated protein 2 (SKP2), and upregulation of its substrate, p27(KIP1). Our data indicate that RECK-induced growth suppression is at least partially dependent on p27, and that RECK and type I collagen share similar effects on the SKP2-p27 pathway. Importantly, in patients with lung, colorectal and bladder cancers, the RECK/SKP2 ratio is high in normal tissues and lower in the cancer tissues. These findings reveal a novel molecular pathway linking cell-cycle progression to RECK downregulation, extracellular matrix degradation and SKP2 upregulation, and suggest that treatment regimens that induce RECK expression could be promising cancer therapies.

Involvement of the Reck tumor suppressor protein in maternal and embryonic vascular remodeling in mice

Background

Developmental angiogenesis proceeds through multiple morphogenetic events including sprouting, intussusception, and pruning. Mice lacking the membrane-anchored metalloproteinase regulator Reck die in utero around embryonic day 10.5 with halted vascular development; however, the mechanisms by which this phenotype arises remain unclear.

Results

We found that Reck is abundantly expressed in the cells associated with blood vessels undergoing angiogenesis or remodelling in the uteri of pregnant female mice. Some of the Reck-positive vessels show morphological features consistent with non-sprouting angiogenesis. Treatment with a vector expressing a small hairpin RNA against Reck severely disrupts the formation of blood vessels with a compact, round lumen. Similar defects were found in the vasculature of Reck-deficient or Reck conditional knockout embryos.

Conclusions

Our findings implicate Reck in vascular remodeling, possibly through non-sprouting angiogenesis, in both maternal and embyornic tissues.

RECK-mediated inhibition of glioma migration and invasion

RECK is an anti-tumoral gene whose activity has been associated with its inhibitory effects regulating MMP-2, MMP-9, and MT1-MMP. RECK level decreases as gliobastoma progresses, varying from less invasive grade II gliomas to very invasive human glioblastoma multiforme (GBM). Since RECK expression and glioma invasiveness show an inverse correlation, the aim of the present study is to investigate whether RECK expression would inhibit glioma invasive behavior. We conducted this study to explore forced RECK expression in the highly invasive T98G human GBM cell line. Expression levels as well as protein levels of RECK, MMP-2, MMP-9, and MT1-MMP were assessed by qPCR and immunoblotting in T98G/RECK+ cells. The invasion and migration capacity of RECK+ cells was inhibited in transwell and wound assays. Dramatic cytoskeleton modifications were observed in the T98G/RECK+ cells, when compared to control cells, such as the abundance of stress fibers (contractile actin-myosin II bundles) and alteration of lamellipodia. T98G/RECK+ cells also displayed phosphorylated focal adhesion kinase (P-FAK) in mature focal adhesions associated with stress fibers; whereas P-FAK in control cells was mostly associated with immature focal complexes. Interestingly, the RECK protein was predominantly localized at the leading edge of migrating cells, associated with membrane ruffles. Unexpectedly, introduced expression of RECK effectively inhibited the invasive process through rearrangement of actin filaments, promoting a decrease in migratory ability. This work has associated RECK tumor-suppressing activity with the inhibition of motility and invasion in this GBM model, which are two glioma characteristics responsible for the inefficiency of current available treatments.

What we learn from transformation suppressor genes: lessons from RECK

Expression cloning is a powerful approach to finding genes that induce appreciable changes in cultured cells. One way to use this technique in cancer research is to isolate cDNAs that induce flat reversion in transformed cells. Such screening, however, is inherently artificial, and therefore requires independent validation of the clinical relevance of isolated genes. Studies of the mechanisms of actions, physiological functions and mechanisms of regulation of these genes at various levels may enrich our knowledge of cancer biology and supplement our toolbox in developing new cancer diagnoses and therapies. In this article we discuss the promise, limitations and recent innovations in this approach, taking one transformation suppressor gene, RECK, as an example.

RECK is up-regulated and involved in chondrocyte cloning in human osteoarthritic cartilage

Reversion-inducing cysteine-rich protein with Kazal motifs (RECK) is a membrane-anchored matrix metalloproteinase regulator, but its functions in cartilage are not fully understood. The aim of the present study was to examine the expression and functions of RECK in human osteoarthritic (OA) cartilage. Quantitative RT-PCR indicated that the expression level of RECK is significantly higher in OA cartilage than in normal cartilage. By immunohistochemical analysis, RECK was localized to chondrocytes in OA cartilage, and the immunoreactivity directly correlated with the Mankin score and degree of chondrocyte cloning and proliferation. In cultured OA chondrocytes, RECK was expressed on the cell surface by glycosylphosphatidylinositol anchoring. The expression was stimulated by insulin-like growth factor-1 and suppressed by interleukin-1 and tumor necrosis factor-alpha. Down-regulation of RECK by small interfering RNA showed reduced spreading and smaller focal adhesions in the chondrocytes. Chondrocyte migration in a monolayer wounding assay was increased by down-regulation of RECK and inhibited by RECK overexpression in an matrix metalloproteinase activity-dependent manner. On the other hand, chondrocyte proliferation was suppressed by RECK silencing, and this was associated with reduced phosphorylation of focal adhesion kinase and extracellular signal-regulated kinase, whereas the proliferation was enhanced by RECK overexpression. These data are the first to demonstrate that RECK is up-regulated in human OA cartilage and suggest that RECK plays a role in chondrocyte cloning probably through suppression and promotion of chondrocyte migration and proliferation, respectively.

Density- and serum-dependent regulation of the Reck tumor suppressor in mouse embryo fibroblasts

Reck is a membrane-anchored glycoprotein identified as a transformation suppressor. Accumulating evidence indicates that Reck negatively regulates a wide spectrum of matrix metalloproteinases and is commonly down-regulated in a variety of malignant solid tumors. Physiological cues that regulate Reck expression, however, remained unknown. In this study, we found that Reck expression was up-regulated at high cell density, low serum, or after treatment with some kinase inhibitors, such as PP2 (Src inhibitor), LY294002 (PI3-kinase inhibitor), and PF573228 (FAK inhibitor), in mouse embryo fibroblasts. Curve fitting indicated that the levels of Reck protein and Reck mRNA are quadratic in the cell density. Other factors, including serum, extracellular matrix components (type I collagen and fibronectin), the kinase inhibitors, and some of their oncogenic targets (v-Src and PIK3CA mutants), modify the shape of the quadratic curve. Comparison of these modifications implicated Src in Reck down-regulation under sparse conditions, PI3-kinase in serum-induced Reck down-regulation, and FAK in Reck down-regulation at high cell density. Fibronectin and type I collagen down-regulated Reck, supporting the role of integrin-FAK signaling in Reck down-regulation at high cell density. Our study has revealed multiple signaling pathways impinging on Reck in cultured mouse embryo fibroblasts and sets a foundation for future studies to find effective Reck inducers of potential value in cancer therapy.

Rat forming incisor requires a rigorous ECM remodeling modulated by MMP/RECK balance

Reversion-inducing-cysteine-rich protein with Kazal motifs (RECK) is a single membrane-anchored MMP-regulator and regulates matrix metalloproteinases (MMP) 2, 9 and 14. In turn, MMPs are endopeptidases that play a pivotal role in remodeling ECM. In this work, we decided to evaluate expression pattern of RECK in growing rat incisor during, specifically focusing out amelogenesis process. Based on different kinds of ameloblasts, our results showed that RECK expression was conducted by secretory and post-secretory ameloblasts. At the secretory phase, RECK was localized in the infra-nuclear region of the ameloblast, outer epithelium, near blood vessels, and in the stellate reticulum. From the transition to the maturation phases, RECK was strongly expressed by non-epithelial immuno-competent cells (macrophages and/or dendritic-like cells) in the papillary layer. From the transition to the maturation stage, RECK expression was increased. RECK mRNA was amplified by RT-PCR from whole enamel organ. Here, we verified the presence of RECK mRNA during all stages of amelogenesis. These events were governed by ameloblasts and by non-epithelial cells residents in the enamel organ. Concluding, we found differential expression of MMPs-2, -9 and RECK in the different phases of amelogenesis, suggesting that the tissue remodeling is rigorously controlled during dental mineralization.

Morphogenetic and regulatory mechanisms during developmental chondrogenesis: new paradigms for cartilage tissue engineering

Cartilage is the first skeletal tissue to be formed during embryogenesis leading to the creation of all mature cartilages and bones, with the exception of the flat bones in the skull. Therefore, errors occurring during the process of chondrogenesis, the formation of cartilage, often lead to severe skeletal malformations such as dysplasias. There are hundreds of skeletal dysplasias, and the molecular genetic etiology of some remains more elusive than of others. Many efforts have aimed at understanding the morphogenetic event of chondrogenesis in normal individuals, of which the main morphogenetic and regulatory mechanisms will be reviewed here. For instance, many signaling molecules that guide chondrogenesis--for example, transforming growth factor-beta, bone morphogenetic proteins, fibroblast growth factors, and Wnts, as well as transcriptional regulators such as the Sox family--have already been identified. Moreover, extracellular matrix components also play an important role in this developmental event, as evidenced by the promotion of the chondrogenic potential of chondroprogenitor cells caused by collagen II and proteoglycans like versican. The growing evidence of the elements that control chondrogenesis and the increasing number of different sources of progenitor cells will, hopefully, help to create tissue engineering platforms that could overcome many developmental or degenerative diseases associated with cartilage defects.

Expression and biological significance of matrix metalloprofeinase inhibitor RECK gene in esophageal squamous cell carcinoma

AIM: To explore the expression of reversion inducing cysteine rich protein with kazal motifs (RECK) in esophageal squamous cell carcinoma (ESCC) and its correlations with the occurrence and development of ESCC.

METHODS: A total of 62 ESCC specimens, resected in Anyang Tumor Hospital of Henan Province from Februrary 26 to March 16, 2006, were collected. All the cases didn't receive chemotherapy, radiotherapy, and immunotherapy. SP immunohistochemical method and in situ hubridyzation were used to detect the expression of RECK protein and mRNA in the 62 carcinoma specimens, 31 cancer-adjacent specimens (within 3 cm) and 62 normal esophageal epithelial specimens.

RESULTS: The protein and mRNA expression of RECK were closely related with the tumor grades, infilatration and lymphatic metastasis in ESCC. The expression rates of RECK protein were increased ordinally in carcinoma specimens, cancer-adjacent epithelium and normal esophageal epithelial specimens, and there was a significant difference in group comparison (RECK protein: χ² = 10.331, P < 0.01; RECK mRNA: χ² = 19.186, P < 0.01). There was a positive correlation between the protein and mRNA expression of RECK (r = 0.416, P < 0.01) in ESCC.

CONCLUSION: Lower expression of RECK has a correlation with the pathogenesis of and development of ESCC, and RECK may be a new assistant index for early diagnosis and prognosis of ESCC.

Recklessness as a hallmark of aggressive cancer

Cancer recurrence after surgical treatment is a major concern for patients and doctors. Understanding what makes tumors prone to recurrence would be an important step toward its prevention. Accumulating evidence indicates that the level of membrane-associated protease regulator reversion-inducing cysteine-rich protein with Kazal motifs (RECK) expressed in tumor tissue is a good prognostic indicator in several common cancers. Certain members of the matrix metalloproteinase family are often upregulated in advanced cancers and are known to play important roles in tumor angiogenesis, invasion and metastasis. RECK negatively regulates several matrix metalloproteinases. Therefore, RECK itself may well be considered a promising tool or target molecule to be activated in cancer therapy. Here we review the recent advances in RECK research and discuss some of the important issues to be addressed in future studies.

Localization of the membrane-anchored MMP-regulator RECK at the neuromuscular junctions

Nerve apposition on nicotinic acetylcholine receptor clusters and invagination of the post-synaptic membrane (i.e. secondary fold formation) occur by embryonic day 18.5 at the neuromuscular junctions (NMJs) in mouse skeletal muscles. Finding the molecules expressed at the NMJ at this stage of development may help elucidating how the strong linkage between a nerve terminal and a muscle fiber is established. Immunohistochemical analyses indicated that the membrane-anchored matrix metalloproteinase regulator RECK was enriched at the NMJ in adult skeletal muscles. Confocal and electron microscopy revealed the localization of RECK immunoreactivity in secondary folds and subsynaptic intracellular compartments in muscles. Time course studies indicated that RECK immunoreactivity becomes associated with the NMJ in the diaphragm at around embryonic day 18.5 and thereafter. These findings, together with known properties of RECK, support the hypothesis that RECK participates in NMJ formation and/or maintenance, possibly by protecting extracellular components, such as synaptic basal laminae, from proteolytic degradation.