A Novel Recombinant Vitronectin Variant Supports the Expansion and Differentiation of Pluripotent Stem Cells in Defined Animal-Free Workflows.

An essential aspect of harnessing the potential of pluripotent stem cells (PSCs) and their derivatives for regenerative medicine is the development of animal-free and chemically defined conditions for ex vivo cultivation. PSCs, including embryonic and induced PSCs (iPSCs), are in the early stages of clinical trials for various indications, including degenerative diseases and traumatic injury. A key step in the workflows generating these cells for more widespread clinical use is their safe and robust ex vivo cultivation. This entails optimization of cell culture media and substrates that are safe and consistent while maintaining robust functionality. Here, we describe the design of a human vitronectin (hVTN) variant with improved manufacturability in a bacterial expression system along with improved function in comparison to wild-type VTN and other previously characterized polypeptide fragments. In conjunction with an animal component-free media formulation, our hVTN fragment provides animal-free conditions for the enhanced expansion of iPSCs. This hVTN variant also supports the reprogramming of PBMCs into iPSCs. Furthermore, we show that these iPSCs can be efficiently differentiated into the three major germ layers and cortical neurons, thereby closing the loop on a completely defined animal-free workflow for cell types relevant for regenerative medicine.

Vitronectin Levels in the Plasma of Neuroblastoma Patients and Culture Media of 3D Models: A Prognostic Circulating Biomarker?

Vitronectin is a glycoprotein present in plasma and the extracellular matrix that is implicated in cell migration. The high amount of vitronectin found in neuroblastoma biopsies has been associated with poor prognosis. Moreover, increased vitronectin levels have been described in the plasma of patients with different cancers. Our aim was to assess vitronectin as a potential circulating biomarker of neuroblastoma prognosis. Vitronectin concentration was quantified using ELISA in culture media of four neuroblastoma cell lines grown in a monolayer and in 3D models, and in the plasma of 114 neuroblastoma patients. Three of the neuroblastoma cell lines secreted vitronectin to culture media when cultured in a monolayer and 3D models. Vitronectin release was higher by neuroblastoma cells cultured in 3D models than in the monolayer and was still elevated when cells were grown in 3D scaffolds with cross-linked vitronectin. Vitronectin secretion occurred independently of cell numbers in cultures. Its concentration in the plasma of neuroblastoma patients ranged between 52.4 and 870 µg/mL (median, 218 µg/mL). A ROC curve was used to establish a cutoff of 361 µg/mL, above which patients over 18 months old had worse prognosis (p = 0.0018). Vitronectin could be considered a new plasma prognostic biomarker in neuroblastoma and warrants confirmation in collaborative studies. Drugs inhibiting vitronectin interactions with cells and/or the extracellular matrix could represent a significant improvement in survival for neuroblastoma patients.

Fibronectin and vitronectin alleviate adipose-derived stem cells senescence during long-term culture through the AKT/MDM2/P53 pathway.

Cellular senescence plays a role in the development of aging-associated degenerative diseases. Cell therapy is recognized as a candidate treatment for degenerative diseases. To achieve the goal of cell therapy, the quality and good characteristics of cells are concerned. Cell expansion relies on two-dimensional culture, which leads to replicative senescence of expanded cells. This study aimed to investigate the effect of cell culture surface modification using fibronectin (FN) and vitronectin (VN) in adipose-derived stem cells (ADSCs) during long-term expansion. Our results showed that ADSCs cultured in FN and VN coatings significantly enhanced adhesion, proliferation, and slow progression of cellular senescence as indicated by lower SA-ß-gal activities and decreased expression levels of genes including p16, p21, and p53. The upregulation of integrin α5 and αv genes influences phosphatidylinositol 4,5-bisphosphate 3-kinase (PI3K), and AKT proteins. FN and VN coatings upregulated AKT and MDM2 leading to p53 degradation. Additionally, MDM2 inhibition by Nutlin-3a markedly elevated p53 and p21 expression, increased cellular senescence, and induced the expression of inflammatory molecules including HMGB1 and IL-6. The understanding of FN and VN coating surface influencing ADSCs, especially senescence characteristics, offers a promising and practical point for the cultivation of ADSCs for future use in cell-based therapies.

Development of advanced cardiac progenitor cell culture system through fibronectin and vitronectin derived peptide coated plate.

Cardiovascular disease remains a global health concern. Stem cell therapy utilizing human cardiac progenitor cells (hCPCs) shows promise in treating cardiac vascular disease. However, limited availability and senescence of hCPCs hinder their widespread use. To address these challenges, researchers are exploring innovative approaches. In this study, a bioengineered cell culture plate was developed to mimic the natural cardiac tissue microenvironment. It was coated with a combination of extracellular matrix (ECM) peptide motifs and mussel adhesive protein (MAP). The selected ECM peptide motifs, derived from fibronectin and vitronectin, play crucial roles in hCPCs. Results revealed that the Fibro-P and Vitro-P coated plates significantly improved hCPC adhesion, proliferation, migration, and differentiation compared to uncoated plates. Additionally, long-term culture on the coated plates delayed cellular senescence and maintained hCPC stemness. These enhancements were attributed to the activation of integrin downstream signaling pathways. The findings suggest that the engineered ECM peptide motif-MAP-coated plates hold potential for enhancing the therapeutic efficacy of stem cell-based therapies in cardiac tissue engineering and regenerative medicine.

Potential Benefits of Integrin αvß3 Antagonists in a Mouse Model of Experimental Dry Eye.

PURPOSE: The purpose of this study was to extensively evaluate the efficacy of integrin αvß3 antagonists for the treatment of experimental dry eye (EDE). METHODS: Vitronectin, an αvß3 ligand, was used to induce tumor necrosis factor-α gene expression in human THP-1 macrophages. To induce EDE, C57BL/6 mice were housed in a low-humidity controlled environment chamber and injected subcutaneously with scopolamine for 7 days. Subsequently, αvß3 antagonists, including RGDfD, c(RGDfD), c(RGDiD), c(RGDfK), ATN-161, SB273005, and cilengitide, were administered topically to EDE animals under controlled environment chamber conditions. Corneal epithelial damage in EDE was assessed by fluorescein staining. The density of conjunctival goblet cells and secretion of tears was measured by period acid-Schiff staining and phenol red-impregnated cotton threads, respectively. Inflammation markers, including tumor necrosis factor-α, interleukin (IL)-1ß, IL-6, IL-17A, and metalloproteinase (MMP)-9, in the pooled cornea and conjunctiva tissues were examined by real-time polymerase chain reaction. RESULTS: The inhibitory effects of αvß3 antagonists on the vitronectin-induced tumor necrosis factor-α gene expression and integrin-mediated inflammatory signaling were validated in THP-1 macrophages. αvß3 antagonists ameliorated the impairment of the corneal epithelial barrier with varying therapeutic efficacies, compared with vehicle-treated mice. c(RGDfD) and c(RGDiD) significantly protected against goblet cell loss, tear reduction, and proinflammatory gene expression in EDE. CONCLUSIONS: Topical applications of αvß3 antagonists yield therapeutic benefits in EDE by promoting corneal epithelial defect healing and reducing inflammation. Antagonistic targeting αvß3 may be a novel promising strategy to treat patients with dry eye disease.

Macrophage promotes fibroblast activation and kidney fibrosis by assembling a vitronectin-enriched microenvironment.

Background: Renal infiltration of inflammatory cells including macrophages is a crucial event in kidney fibrogenesis. However, how macrophage regulates fibroblast activation in the fibrotic kidney remains elusive. In this study, we show that macrophages promoted fibroblast activation by assembling a vitronectin (Vtn)-enriched, extracellular microenvironment. Methods: We prepared decellularized kidney tissue scaffold (KTS) from normal and fibrotic kidney after unilateral ischemia-reperfusion injury (UIRI) and carried out an unbiased quantitative proteomics analysis. NRK-49F cells were seeded on macrophage-derived extracellular matrix (ECM) scaffold. Genetic Vtn knockout (Vtn-/-) mice and chronic kidney disease (CKD) model with overexpression of Vtn were used to corroborate a role of Vtn/integrin αvß5/Src in kidney fibrosis. Results: Vtn was identified as one of the most upregulated proteins in the decellularized kidney tissue scaffold from fibrotic kidney by mass spectrometry. Furthermore, Vtn was upregulated in the kidney of mouse models of CKD and primarily expressed and secreted by activated macrophages. Urinary Vtn levels were elevated in CKD patients and inversely correlated with kidney function. Genetic ablation or knockdown of Vtn protected mice from developing kidney fibrosis after injury. Conversely, overexpression of Vtn exacerbated renal fibrotic lesions and aggravated renal insufficiency. We found that macrophage-derived, Vtn-enriched extracellular matrix scaffold promoted fibroblast activation and proliferation. In vitro, Vtn triggered fibroblast activation by stimulating integrin αvß5 and Src kinase signaling. Either blockade of αvß5 with neutralizing antibody or pharmacological inhibition of Src by Saracatinib abolished Vtn-induced fibroblast activation. Moreover, Saracatinib dose-dependently ameliorated Vtn-induced kidney fibrosis in vivo. These results demonstrate that macrophage induces fibroblast activation by assembling a Vtn-enriched extracellular microenvironment, which triggers integrin αvß5 and Src kinase signaling. Conclusion: Our findings uncover a novel mechanism by which macrophages contribute to kidney fibrosis via assembling a Vtn-enriched extracellular niche and suggest that disrupting fibrogenic microenvironment could be a therapeutic strategy for fibrotic CKD.

Selective Grafting of Protease-Resistant Adhesive Peptides on Titanium Surfaces.

In orthopedic, dental, and maxillofacial fields, joint prostheses, plates, and screws are widely used in the treatment of problems related to bone tissue. However, the use of these prosthetic systems is not free from complications: the fibrotic encapsulation of endosseous implants often prevents optimal integration of the prostheses with the surrounding bone. To overcome these issues, biomimetic titanium implants have been developed where synthetic peptides have been selectively grafted on titanium surfaces via Schiff base formation. We used the retro-inverted sequence (DHVPX) from [351-359] human Vitronectin and its dimer (D2HVP). Both protease-resistant peptides showed increased human osteoblast adhesion and proliferation, an augmented number of focal adhesions, and cellular spreading with respect to the control. D2HVP-grafted samples significantly enhance Secreted Phosphoprotein 1, Integrin Binding Sialoprotein, and Vitronectin gene expression vs. control. An estimation of peptide surface density was determined by Two-photon microscopy analysis on a silanized glass model surface labeled with a fluorescent analog.

Potential Urine Proteomic Biomarkers for Focal Segmental Glomerulosclerosis and Minimal Change Disease.

Primary focal segmental glomerulosclerosis (FSGS), along with minimal change disease (MCD), are diseases with primary podocyte damage that are clinically manifested by the nephrotic syndrome. The pathogenesis of these podocytopathies is still unknown, and therefore, the search for biomarkers of these diseases is ongoing. Our aim was to determine of the proteomic profile of urine from patients with FSGS and MCD. Patients with a confirmed diagnosis of FSGS (n = 30) and MCD (n = 9) were recruited for the study. For a comprehensive assessment of the severity of FSGS a special index was introduced, which was calculated as follows: the first score was assigned depending on the level of eGFR, the second score-depending on the proteinuria level, the third score-resistance to steroid therapy. Patients with the sum of these scores of less than 3 were included in group 1, with 3 or more-in group 2. The urinary proteome was analyzed using liquid chromatography/mass spectrometry. The proteome profiles of patients with severe progressive FSGS from group 2, mild FSGS from group 1 and MCD were compared. Results of the label free analysis were validated using targeted LC-MS based on multiple reaction monitoring (MRM) with stable isotope labelled peptide standards (SIS) available for 47 of the 76 proteins identified as differentiating between at least one pair of groups. Quantitative MRM SIS validation measurements for these 47 proteins revealed 22 proteins with significant differences between at least one of the two group pairs and 14 proteins were validated for both comparisons. In addition, all of the 22 proteins validated by MRM SIS analysis showed the same direction of change as at the discovery stage with label-free LC-MS analysis, i.e., up or down regulation in MCD and FSGS1 against FSGS2. Patients from the FSGS group 2 showed a significantly different profile from both FSGS group 1 and MCD. Among the 47 significantly differentiating proteins, the most significant were apolipoprotein A-IV, hemopexin, vitronectin, gelsolin, components of the complement system (C4b, factors B and I), retinol- and vitamin D-binding proteins. Patients with mild form of FSGS and MCD showed lower levels of Cystatin C, gelsolin and complement factor I.

A Vitronectin-Derived Peptide Restores Ovariectomy-Induced Bone Loss by Dual Regulation of Bone Remodeling.

BACKGROUND: Bone remodeling is tightly regulated through bone resorption and bone formation; imbalances in bone remodeling can cause various pathological conditions such as osteoporosis. Antiresorptive agents commonly used for treating osteoporosis do not substantially reverse osteoporotic bone loss. METHODS: We evaluated the effects of the RVYFFKGKQYWE motif (residues 270-281; VnP-16) of human vitronectin on the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and osteoclastogenesis of bone marrow-derived macrophages. The effects of VnP-16 were also assessed in a mouse model of estrogen deficiency-induced osteoporosis (ovariectomized female C57BL/6 mice). To assay whether VnP-16 can reverse ovariectomy-induced bone loss, synthetic peptides or vehicle were subcutaneously injected into ovariectomized mice once a week for 4 weeks (n = 10/group). To evaluate the bone restorative effects of VnP-16, in-vivo micro-computed tomography analysis and histological staining were performed. RESULTS: VnP-16 induced osteogenic differentiation of hMSCs and inhibited the RANKL-RANK-TRAF6 axis in the osteoclastogenesis signaling pathway. Furthermore, systemic administration of VnP-16 reversed ovariectomy-induced bone loss in the femoral neck, distal femur and lumbar spine by increasing osteoblast differentiation and promoting bone formation, and concomitantly decreasing osteoclastogenesis and inhibiting bone resorption. The bone restorative effect of VnP-16 was observed one week after subcutaneous administration, and although the timing of the effect differed according to bone location, it persisted for at least 3 weeks. CONCLUSION: Our findings suggest that VnP-16 is a potential therapeutic agent for treating osteoporosis that mediates its effects through dual regulation of bone remodeling.

Hsa_circ_0079530/AQP4 Axis Is Related to Non-Small Cell Lung Cancer Development and Radiosensitivity.

BACKGROUND: Circular RNAs are associated with non-small cell lung cancer (NSCLC) development and radiosensitivity. Nevertheless, the function and regulation mechanism of hsa_circ_0079530 (circ_0079530) in NSCLC development and radiosensitivity are largely unknown. METHODS: The abundances of circ_0079530, microRNA (miR-409-3p), aquaporin 4 (AQP4), E-cadherin, intercellular adhesion molecule-1, vitronectin, proliferating cell nuclear antigen, and matrix metalloproteinase 9 were determined via quantitative reverse transcription polymerase chain reaction or western blotting. Cell proliferation, survival fraction, cycle process, migration, invasion, and in vivo growth were examined by cell counting kit-8, colony formation, flow cytometry, transwell, and xenograft analyses. The binding relationship was assessed via dual-luciferase reporter assay and RNA immunoprecipitation assay. RESULTS: Circ_0079530 expression was increased in NSCLC tissues and radioresistant samples. Circ_0079530 knockdown restrained cell proliferation, migration, and invasion, and facilitated radiosensitivity. Circ_0079530 silence decreased tumor growth with or without radiation treatment. Circ_0079530 was verified as a miR-409-3p sponge, and miR-409-3p downregulation mitigated the effects of circ_0079530 interference on NSCLC cell malignancy and radiosensitivity. AQP4 was directly targeted by miR-409-3p. MiR-409-3p restrained cell proliferation, migration, and invasion, and enhanced radiosensitivity by decreasing AQP4 expression. Notably, circ_0079530 silence decreased AQP4 expression by regulating miR-409-3p expression. CONCLUSION: Circ_0079530 silence repressed cell proliferation, migration, and invasion, and facilitated radiosensitivity in NSCLC cells by mediating miR-409-3p/AQP4 axis.

Female-specific neuroprotection after ischemic stroke by vitronectin-focal adhesion kinase inhibition.

We found that blood vitronectin (VTN) leaks into the brain and exacerbates tissue loss after stroke by increasing pro-inflammatory IL-6 expression in female, but not male, mice. VTN signals through integrins and downstream focal adhesion kinase (FAK). Here, a two day systemic treatment with a small molecule FAK inhibitor starting 6 h after middle cerebral artery occlusion reduced ipsilateral brain injury size by ∼40-45% at 7 and 14 d, as well as inflammation and motor dysfunction in wild-type female, but not male, mice. FAK inhibition also reduced IL-6 expression in the injured female striatum at 24 h by 62%. Inducible selective gene deletion of FAK in astrocytes also reduced acute IL-6 expression by 72% only in females, and mitigated infarct size by ∼80% and inflammation at 14 d after stroke. Lastly, VTN-/- females had better outcomes, but FAK inhibitor treatment had no additional protective or anti-inflammatory effects. Altogether, this suggests that VTN is detrimental in females primarily through FAK and that FAK inhibition provides neuroprotection (cerebroprotection) by reducing VTN-induced IL-6 expression in astrocytes. Thus, VTN signaling can be targeted to mitigate harmful inflammation with relevance to treatments for women with ischemic stroke, who often have worse outcomes than men.

A vitronectin-derived dimeric peptide suppresses osteoclastogenesis by binding to c-Fms and inhibiting M-CSF signaling.

Vitronectin is an abundant multifunctional glycoprotein found in serum, the extracellular matrix, and bone, and is involved in diverse physiological processes. Here, we developed a new bioactive dimeric peptide (VnP-8-DN1 dimer) from a human vitronectin-derived motif (IDAAFTRINCQG; residues 206-217; VnP-8) via removal of an isoleucine residue at the N-terminus of VnP-8 and spontaneous air oxidation. The VnP-8-DN1 dimer potently enhanced cell attachment activity, and this activity was mediated by binding to cellular heparan sulfate proteoglycan receptors. Moreover, the VnP-8-DN1 dimer suppressed osteoclast differentiation by blocking the early stage of osteoclastogenesis induced by macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL). Furthermore, the VnP-8-DN1 dimer decreased the bone-resorbing activity of osteoclasts and increased the survival of osteoclast precursor cells by decreasing the cellular level of c-Fms and reducing RANK expression. Taken together, these results demonstrate that the VnP-8-DN1 dimer inhibits the early stages of M-CSF- and RANK-induced osteoclast differentiation by binding to c-Fms and inhibiting M-CSF signaling.

Extracellular matrix modulates T cell clearance of malignant cells in vitro.

Despite the success of T cell checkpoint therapies, breast cancers rarely express these immunotherapy markers and are believed to be largely "immune cold" with limited inflammation and immune activation. The reason for this limited immune activation remains poorly understood. We sought to determine whether extracellular matrix substrate could contribute to this limited immune activation. Specifically, we asked whether extracellular matrix could alter T cell cytotoxicity against malignant mammary gland carcinoma cells (MCC) in a setup designed to promote maximal T cell efficacy (i.e., rich media with abundant IL2, high ratio of T cells to MCC). We observed that T cell clearance of MCC varied from 0% in collagen 4 or 6 conditions to almost 100% in fibronectin or vitronectin. Transcriptomics revealed that T cell function was defective in MCC/T cell cocultures on collagen 4 (Col4), potentially corresponding to greater expression of cytokines MCC cultured in this environment. In contrast, transcriptomics revealed an effective, exhausted phenotype on vitronectin. The observation that Col4 induces T cell suppression suggests that targeting tumor-ECM interactions may permit new approaches for utilizing immunotherapy in tumors which do not provoke a strong immune response.

The effect of endocrine disrupting chemicals on the vitronectin-receptor (integrin αvß3)-mediated cell adhesion of human umbilical vein endothelial cells.

Endocrine disrupting chemicals (EDCs) are associated with cancer development and progression due to their promotion of increased cell invasiveness and metastasis formation. However, the effects of EDCs on cell adhesion mediated through integrins have not been well studied to date. Their actions are implicated by binding sites for hormones on the vitronectin receptor (VTNR; or integrin αvß3), which is involved in tumor angiogenesis and metastasis. VTNR-expressing human umbilical vein endothelial cells (HUVECs) were used to determine the effects of EDCs and endogenous hormones on cell adhesion to vitronectin-coated surfaces, and on VTNR activation. Cell adhesion was significantly increased for bisphenol A, triclocarban, and triclosan (10, 100 nM; p < 0.05), with similar trends for bisphenols AF and S (10, 100 nM; p > 0.05). No changes in cell adhesion were seen for 5α-dihydrotestosterone, 17ß-estradiol, triiodothyronine, imatinib and paroxetine. These data indicate that EDC-mediated increases in HUVEC adhesion to vitronectin are not mediated through androgenic, estrogenic, or thyroid activities, nor through activation of VTNR. Although these effects of EDCs on HUVEC adhesion require further investigation of the underlying mechanism(s) of action to define their biological relevance, the low-dose effects and nonmonotonic responses revealed here define the need for further investigation of these EDCs.

Integrin αv and Vitronectin Prime Macrophage-Related Inflammation and Contribute the Development of Dry Eye Disease.

Cell signaling mediated by the αv integrin plays a pivotal role in macrophage activation in various inflammatory processes, but its involvement in the pathogenesis of dry eye disease (DED) remains unclear. In a murine model of DED, we found increased αv integrin expression in ocular surface macrophages. The αv integrins inhibitor c(RGDfK) ameliorated the corneal damage caused by DED, suggesting a pathogenic role for αv integrin. Because tear hyperosmolarity induces ocular inflammation in DED, a hyperosmolar culture of murine bone marrow-derived macrophages (BMDMs) is used to reproduce inflammation in vitro. However, the expression of proinflammatory cytokine mRNA was minimal, even though αv integrin was induced. In searching for components that are involved in αv integrin-mediated inflammation but that are missing from the culture model, we showed that the levels of vitronectin (VTN), a binding ligand of αv integrins, were increased in the tear fluid and conjunctival stroma of DED animals. The addition of VTN prominently enhanced hyperosmolarity-induced inflammation in BMDMs. Mechanistically, we showed that VTN/αv integrins mediated NF-κB activation to induce inflammatory gene expression in the BMDMs. Our findings indicate that interaction the of VTN with αv integrins is a crucial step in the inflammatory process in DED and suggests a novel therapeutic target.

Modulation of αVß6 integrin in osteoarthritis-related synovitis and the interaction with VTN(381-397 a.a.) competing for TGF-ß1 activation.

Osteoarthritis is characterized by structural alteration of joints. Fibrosis of the synovial tissue is often detected and considered one of the main causes of joint stiffness and pain. In our earlier proteomic study, increased levels of vitronectin (VTN) fragment (amino acids 381-397) were observed in the serum of osteoarthritis patients. In this work, the affinity of this fragment for integrins and its putative role in TGF-ß1 activation were investigated. A competition study determined the interaction of VTN(381-397 a.a.) with αVß6 integrin. Subsequently, the presence of αVß6 integrin was substantiated on primary human fibroblast-like synoviocytes (FLSs) by western blot and flow cytometry. By immunohistochemistry, ß6 was detected in synovial membranes, and its expression showed a correlation with tissue fibrosis. Moreover, ß6 expression was increased under TGF-ß1 stimulation; hence, a TGF-ß bioassay was applied. We observed that αVß6 could mediate TGF-ß1 bioavailability and that VTN(381-397 a.a.) could prevent TGF-ß1 activation by interacting with αVß6 in human FLSs and increased α-SMA. Finally, we analyzed serum samples from healthy controls and patients with osteoarthritis and other rheumatic diseases by nano-LC/Chip MS-MS, confirming the increased expression of VTN(381-397 a.a.) in osteoarthritis as well as in lupus erythematosus and systemic sclerosis. These findings corroborate our previous observations concerning the overexpression of VTN(381-397 a.a.) in osteoarthritis but also in other rheumatic diseases. This fragment interacts with αVß6 integrin, a receptor whose expression is increased in FLSs from the osteoarthritic synovial membrane and that can mediate the activation of the TGF-ß1 precursor in human FLSs.

Entry of spores into intestinal epithelial cells contributes to recurrence of Clostridioides difficile infection.

Clostridioides difficile spores produced during infection are important for the recurrence of the disease. Here, we show that C. difficile spores gain entry into the intestinal mucosa via pathways dependent on host fibronectin-α5ß1 and vitronectin-αvß1. The exosporium protein BclA3, on the spore surface, is required for both entry pathways. Deletion of the bclA3 gene in C. difficile, or pharmacological inhibition of endocytosis using nystatin, leads to reduced entry into the intestinal mucosa and reduced recurrence of the disease in a mouse model. Our findings indicate that C. difficile spore entry into the intestinal barrier can contribute to spore persistence and infection recurrence, and suggest potential avenues for new therapies.

Vitronectin regulates the axon specification of mouse cerebellar granule cell precursors via αvß5 integrin in the differentiation stage.

Vitronectin, an extracellular matrix protein, controls the differentiation of cerebellar granule cell precursors (CGCPs) via αvß5 integrin, particularly in the initial stage of differentiation to granule cells. In this study, we determined whether vitronectin regulates axon specification in this initial differentiation stage of CGCPs. First, we analyzed whether vitronectin deficiency, ß5 integrin knockdown (KD), and ß5 integrin overexpression affect axon specification of primary cultured CGCPs. Vitronectin deficiency and ß5 integrin KD inhibited axon formation, while vitronectin administrated- and ß5 integrin overexpressed-neurons formed multiple axons. Moreover, KD of ß5 integrin suppressed vitronectin-induced multiple axon formation. These findings indicate that vitronectin contributes to regulating axon specification via αvß5 integrin in CGCPs. Next, we determined the signaling pathway involved in regulating vitronectin-induced axon specification. Wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3K), inhibited vitronectin-induced multiple axon specification, and lithium chloride, an inhibitor of glyocogen synthase kinase 3 beta (GSK3ß), attenuated the inhibitory effect of vitronectin-KO and ß5 integrin KD on the specification of CGCPs. In addition, vitronectin induced the phosphorylation of protein kinase B (Akt) and GSK3ß in neuroblastoma Neuro2a cells. Taken together, our results indicate that vitronectin plays an important factor in axon formation process in CGCPs via a ß5 integrin/PI3K/GSK3ß pathway.

Altered Protein Function Caused by AMD-associated Variant rs704 Links Vitronectin to Disease Pathology.

Purpose: Vitronectin, a cell adhesion and spreading factor, is suspected to play a role in the pathogenesis of age-related macular degeneration (AMD), as it is a major component of AMD-specific extracellular deposits (e.g., soft drusen, subretinal drusenoid deposits). The present study addressed the impact of AMD-associated non-synonymous variant rs704 in the vitronectin-encoding gene VTN on vitronectin functionality. Methods: Effects of rs704 on vitronectin expression and processing were analyzed by semi-quantitative sequencing of VTN transcripts from retinal pigment epithelium (RPE) cells generated from human induced pluripotent stem cells (hiPSCs) and from human neural retina, as well as by western blot analyses on heterologously expressed vitronectin isoforms. Binding of vitronectin isoforms to retinal and endothelial cells was analyzed by western blot. Immunofluorescence staining followed extracellular matrix (ECM) deposition in cultured RPE cells heterologously expressing the vitronectin isoforms. Adhesion of fluorescently labeled RPE or endothelial cells in dependence of recombinant vitronectin or vitronectin-containing ECM was investigated fluorometrically or microscopically. Tube formation and migration assays addressed effects of vitronectin on angiogenesis-related processes. Results: Variant rs704 affected expression, secretion, and processing but not oligomerization of vitronectin. Cell binding and influence on RPE-mediated ECM deposition differed between AMD-risk-associated and non-AMD-risk-associated protein isoforms. Finally, vitronectin affected adhesion and endothelial tube formation. Conclusions: The AMD-risk-associated vitronectin isoform exhibits increased expression and altered functionality in cellular processes related to the sub-RPE aspects of AMD pathology. Although further research is required to address the subretinal disease aspects, this initial study supports an involvement of vitronectin in AMD pathogenesis.

The iron-regulated surface determinant B (IsdB) protein from Staphylococcus aureus acts as a receptor for the host protein vitronectin.

Staphylococcus aureus is an important bacterial pathogen that can cause a wide spectrum of diseases in humans and other animals. S. aureus expresses a variety of virulence factors that promote infection with this pathogen. These include cell-surface proteins that mediate adherence of the bacterial cells to host extracellular matrix components, such as fibronectin and fibrinogen. Here, using immunoblotting, ELISA, and surface plasmon resonance analysis, we report that the iron-regulated surface determinant B (IsdB) protein, besides being involved in heme transport, plays a novel role as a receptor for the plasma and extracellular matrix protein vitronectin (Vn). Vn-binding activity was expressed by staphylococcal strains grown under iron starvation conditions when Isd proteins are expressed. Recombinant IsdB bound Vn dose dependently and specifically. Both near-iron transporter motifs NEAT1 and NEAT2 of IsdB individually bound Vn in a saturable manner, with KD values in the range of 16-18 nm Binding of Vn to IsdB was specifically blocked by heparin and reduced at high ionic strength. Furthermore, IsdB-expressing bacterial cells bound significantly higher amounts of Vn from human plasma than did an isdB mutant. Adherence to and invasion of epithelial and endothelial cells by IsdB-expressing S. aureus cells was promoted by Vn, and an αvß3 integrin-blocking mAb or cilengitide inhibited adherence and invasion by staphylococci, suggesting that Vn acts as a bridge between IsdB and host αvß3 integrin.