Browsing by Subject "ADHESION"

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  • Guenther, Carla; Faisal, Imrul; Uotila, Liisa; Llort Asens, Marc; Harjunpää, Heidi; Savinko, Terhi; Öhman, Tiina; Yao, Sean; Moser, Markus; Morris, Stephan W.; Tojkander, Sari; Fagerholm, Susanna (2019)
    beta2-integrins are essential for immune system function because they mediate immune cell adhesion and signaling. Consequently, a loss of beta2-integrin expression or function causes the immunodeficiency disorders, Leukocyte Adhesion Deficiency (LAD) type I and III. LAD-III is caused by mutations in an important integrin regulator, kindlin-3, but exactly how kindlin-3 regulates leukocyte adhesion has remained incompletely understood. Here we demonstrate that mutation of the kindlin-3 binding site in the b2-integrin (TTT/AAA-b2-integrin knock-in mouse/KI) abolishes activation of the actin-regulated myocardin related transcription factor A/serum response factor (MRTF-A/SRF) signaling pathway in dendritic cells and MRTF-A/SRF-dependent gene expression. We show that Ras homolog gene family, member A (RhoA) activation and filamentous-actin (F-actin) polymerization is abolished in murine TTT/AAA-b2-integrin KI dendritic cells, which leads to a failure ofMRTF-A to localize to the cell nucleus to coactivate genes together with SRF. In addition, we show that dendritic cell gene expression, adhesion and integrin-mediated traction forces on ligand coated surfaces is dependent on the MRTF-A/SRF signaling pathway. The participation of b2-integrin and kindlin-3-mediated cell adhesion in the regulation of the ubiquitous MRTF-A/SRF signaling pathway in immune cells may help explain the role of b2-integrin and kindlin-3 in integrin-mediated gene regulation and immune system function.
  • Pallares, Jordi; Senan, Oriol; Guimera, Roger; Vernet, Anton; Aguilar-Mogas, Antoni; Vilahur, Gemma; Badimon, Lina; Sales-Pardo, Marta; Cito, Salvatore (2015)
    Thrombus formation is a multiscale phenomenon triggered by platelet deposition over a protrombotic surface (eg. a ruptured atherosclerotic plaque). Despite the medical urgency for computational tools that aid in the early diagnosis of thrombotic events, the integration of computational models of thrombus formation at different scales requires a comprehensive understanding of the role and limitation of each modelling approach. We propose three different modelling approaches to predict platelet deposition. Specifically, we consider measurements of platelet deposition under blood flow conditions in a perfusion chamber for different time periods (3, 5, 10, 20 and 30 minutes) at shear rates of 212 s(-1), 1390 s(-1) and 1690 s(-1). Our modelling approaches are: i) a model based on the mass-transfer boundary layer theory; ii) a machine-learning approach; and iii) a phenomenological model. The results indicate that the three approaches on average have median errors of 21%, 20.7% and 14.2%, respectively. Our study demonstrates the feasibility of using an empirical data set as a proxy for a real-patient scenario in which practitioners have accumulated data on a given number of patients and want to obtain a diagnosis for a new patient about whom they only have the current observation of a certain number of variables.
  • Harjumaki, Riina; Zhang, Xue; Nugroho, Robertus Wahyu N.; Farooq, Muhammad; Lou, Yan-Ru; Yliperttula, Marjo; Valle-Delgado, Juan Jose; Osterberg, Monika (2020)
    Transmembrane protein integrins play a key role in cell adhesion. Cell-biomaterial interactions are affected by integrin expression and conformation, which are actively controlled by cells. Although integrin structure and function have been studied in detail, quantitative analyses of integrin-mediated cell-biomaterial interactions are still scarce. Here, we have used atomic force spectroscopy to study how integrin distribution and activation (via intracellular mechanisms in living cells or by divalent cations) affect the interaction of human pluripotent stem cells (WA07) and human hepatocarcinoma cells (HepG2) with promising biomaterials.human recombinant laminin-521 (LN-521) and cellulose nanofibrils (CNF). Cell adhesion to LN-521-coated probes was remarkably influenced by cell viability, divalent cations, and integrin density in WA07 colonies, indicating that specific bonds between LN-521 and activated integrins play a significant role in the interactions between LN-521 and HepG2 and WA07 cells. In contrast, the interactions between CNF and cells were nonspecific and not influenced by cell viability or the presence of divalent cations. These results shed light on the underlying mechanisms of cell adhesion, with direct impact on cell culture and tissue engineering applications.
  • Reunanen, Justus; Kainulainen, Veera; Huuskonen, Laura; Ottman, Noora; Belzer, Clara; Huhtinen, Heikki; de Vos, Willem M.; Satokari, Reetta (2015)
    Akkermansia muciniphila is a Gram-negative mucin-degrading bacterium that resides in the gastrointestinal tracts of humans and animals. A. muciniphila has been linked with intestinal health and improved metabolic status in obese and type 2 diabetic subjects. Specifically, A. muciniphila has been shown to reduce high-fat-diet-induced endotoxemia, which develops as a result of an impaired gut barrier. Despite the accumulating evidence of the health-promoting effects of A. muciniphila, the mechanisms of interaction of the bacterium with the host have received little attention. In this study, we used several in vitro models to investigate the adhesion of A. muciniphila to the intestinal epithelium and its interaction with the host mucosa. We found that A. muciniphila adheres strongly to the Caco-2 and HT-29 human colonic cell lines but not to human colonic mucus. In addition, A. muciniphila showed binding to the extracellular matrix protein laminin but not to collagen I or IV, fibronectin, or fetuin. Importantly, A. muciniphila improved enterocyte monolayer integrity, as shown by a significant increase in the transepithelial electrical resistance (TER) of cocultures of Caco-2 cells with the bacterium. Further, A. muciniphila induced interleukin 8 (IL-8) production by enterocytes at cell concentrations 100-fold higher than those for Escherichia coli, suggesting a very low level of proinflammatory activity in the epithelium. In conclusion, our results demonstrate that A. muciniphila adheres to the intestinal epithelium and strengthens enterocyte monolayer integrity in vitro, suggesting an ability to fortify an impaired gut barrier. These results support earlier associative in vivo studies and provide insights into the interaction of A. muciniphila with the host.
  • Kratochwil, Claudius; Kautt, Andreas F.; Nater, Alexander; Härer, Andreas; Liang, Yipeng; Henning, Frederico; Meyer, Axel (2022)
    Polymorphisms have fascinated biologists for a long time, but their genetic underpinnings often remain elusive. Here, we aim to uncover the genetic basis of the gold/dark polymorphism that is eponymous of Midas cichlid fish (Amphilophus spp.) adaptive radiations in Nicaraguan crater lakes. While most Midas cichlids are of the melanic “dark morph”, about 10% of individuals lose their melanic pigmentation during their ontogeny and transition into a conspicuous “gold morph”. Using a new haplotype-resolved long-read assembly we discover an 8.2 kb, transposon-derived inverted repeat in an intron of an undescribed gene, which we term goldentouch in reference to the Greek myth of King Midas. The gene goldentouch is differentially expressed between morphs, presumably due to structural implications of inverted repeats in both DNA and/or RNA (cruciform and hairpin formation). The near-perfect association of the insertion with the phenotype across independent populations suggests that it likely underlies this trans-specific, stable polymorphism.
  • Myllymaki, Satu-Marja; Kämäräinen, Ulla-Reetta; Liu, Xiaonan; Cruz, Sara Pereira; Miettinen, Sini; Vuorela, Mikko; Varjosalo, Markku; Manninen, Aki (2019)
    Integrin-mediated laminin adhesions mediate epithelial cell anchorage to basement membranes and are critical regulators of epithelial cell polarity. Integrins assemble large multiprotein complexes that link to the cytoskeleton and convey signals into the cells. Comprehensive proteomic analyses of actin network-linked focal adhesions (FA) have been performed, but the molecular composition of intermediate filament-linked hemidesmosomes (HD) remains incompletely characterized. Here we have used proximity-dependent biotin identification (BioID) technology to label and characterize the interactome of epithelia-specific beta 4-integrin that, as alpha 6 beta 4-heterodimer, forms the core of HDs. The analysis identified similar to 150 proteins that were specifically labeled by BirA-tagged integrin-beta 4. In addition to known HDs proteins, the interactome revealed proteins that may indirectly link integrin-beta 4 to actin-connected protein complexes, such as FAs and dystrophin/dystroglycan complexes. The specificity of the screening approach was validated by confirming the HD localization of two candidate beta 4-interacting proteins, utrophin (UTRN) and ELKS/Rab6-interacting/CAST family member 1 (ERC1). Interestingly, although establishment of functional HDs depends on the formation of alpha 6 beta 4-heterodimers, the assembly of beta 4-interactome was not strictly dependent on alpha 6-integrin expression. Our survey to the HD interactome sets a precedent for future studies and provides novel insight into the mechanisms of HD assembly and function of the beta 4-integrin.
  • Vuorio, Joni; Vattulainen, Ilpo; Martinez-Seara, Hector (2017)
    Hyaluronan is a polyanionic, megadalton-scale polysaccharide, which initiates cell signaling by interacting with several receptor proteins including CD44 involved in cell-cell interactions and cell adhesion. Previous studies of the CD44 hyaluronan binding domain have identified multiple widespread residues to be responsible for its recognition capacity. In contrast, the X-ray structural characterization of CD44 has revealed a single binding mode associated with interactions that involve just a fraction of these residues. In this study, we show through atomistic molecular dynamics simulations that hyaluronan can bind CD44 with three topographically different binding modes that in unison define an interaction fingerprint, thus providing a plausible explanation for the disagreement between the earlier studies. Our results confirm that the known crystallographic mode is the strongest of the three binding modes. The other two modes represent metastable configurations that are readily available in the initial stages of the binding, and they are also the most frequently observed modes in our unbiased simulations. We further discuss how CD44, fostered by the weaker binding modes, diffuses along HA when attached. This 1D diffusion combined with the constrained relative orientation of the diffusing proteins is likely to influence the aggregation kinetics of CD44. Importantly, CD44 aggregation has been suggested to be a possible mechanism in CD44-mediated signaling.
  • Simonsen, Johan Rasmus; Järvinen, Asko; Hietala, Kustaa; Harjutsalo, Valma; Forsblom, Carol; Groop, Per-Henrik; Lehto, Markku (2021)
    Background/Aims Diabetic retinopathy (DR) is associated and shares many risk factors with other diabetic complications, including inflammation. Bacterial infections, potent inducers of inflammation have been associated with the development of diabetic complications apart from DR. Our aim was to investigate the association between bacterial infections and DR. Methods Adult individuals with type 1 diabetes (n=1043) were recruited from the Finnish Diabetic Nephropathy Study (FinnDiane), a prospective follow-up study. DR was defined as incident severe diabetic retinopathy (SDR), identified as first laser treatment. Data on DR were obtained through fundus photographs and medical records, data on bacterial infections from comprehensive national registries (1 January 1995 to 31 December 2015). Risk factors for DR and serum bacterial lipopolysaccharide (LPS) activity were determined at baseline. Results Individuals with incident SDR (n=413) had a higher mean number of antibiotic purchases/follow-up year compared with individuals without incident SDR (n=630) (0.92 [95% CI 0.82 to 1.02] vs 0.67 [0.62-0.73], p=0.02), as well as higher levels of LPS activity (0.61 [0.58-0.65] vs 0.56 [0.54-0.59] EU/mL, p=0.03). Individuals with on average >= 1 purchase per follow-up year (n=269) had 1.5 times higher cumulative incidence of SDR, compared with individuals with
  • Jiu, Yaming; Lehtimaki, Jaakko; Tojkander, Sari; Cheng, Fang; Jäälinoja, Harri; Liu, Xiaonan; Varjosalo, Markku; Eriksson, John E.; Lappalainen, Pekka (2015)
    The actin cytoskeleton and cytoplasmic intermediate filaments contribute to cell migration and morphogenesis, but the interplay between these two central cytoskeletal elements has remained elusive. Here, we find that specific actin stress fiber structures, transverse arcs, interact with vimentin intermediate filaments and promote their retrograde flow. Consequently, myosin-II-containing arcs are important for perinuclear localization of the vimentin network in cells. The vimentin network reciprocally restricts retrograde movement of arcs and hence controls the width of flat lamellum at the leading edge of the cell. Depletion of plectin recapitulates the vimentin organization phenotype of arc-deficient cells without affecting the integrity of vimentin filaments or stress fibers, demonstrating that this cytoskeletal crosslinker is required for productive interactions between vimentin and arcs. Collectively, our results reveal that plectin-mediated interplay between contractile actomyosin arcs and vimentin intermediate filaments controls the localization and dynamics of these two cytoskeletal systems and is consequently important for cell morphogenesis.
  • Ciuba, Katarzyna; Hawkes, William; Tojkander, Sari; Kogan, Konstantin; Engel, Ulrike; Iskratsch, Thomas; Lappalainen, Pekka (2018)
    Contractile actomyosin bundles, stress fibers, contribute to morphogenesis, migration, and mechanosensing of non-muscle cells. In addition to actin and non-muscle myosin II (NMII), stress fibers contain a large array of proteins that control their assembly, turnover, and contractility. Calponin-3 (Cnn3) is an actin-binding protein that associates with stress fibers. However, whether Cnn3 promotes stress fiber assembly, or serves as either a positive or negative regulator of their contractility has remained obscure. Here, we applied U2OS osteosarcoma cells as a model system to study the function of Cnn3. We show that Cnn3 localizes to both NMII-containing contractile ventral stress fibers and transverse arcs, as well as to non-contractile dorsal stress fibers that do not contain NMII. Fluorescencerecovery-after-photobleaching experiments revealed that Cnn3 is a dynamic component of stress fibers. Importantly, CRISPR/Cas9 knockout and RNAi knockdown studies demonstrated that Cnn3 is not essential for stress fiber assembly. However, Cnn3 depletion resulted in increased and uncoordinated contractility of stress fibers that often led to breakage of individual actomyosin bundles within the stress fiber network. Collectively these results provide evidence that Cnn3 is dispensable for the assembly of actomyosin bundles, but that it is required for controlling proper contractility of the stress fiber network.
  • Rasinkangas, Pia; Tytgat, Hanne L. P.; Ritari, Jarmo; Reunanen, Justus; Salminen, Seppo; Palva, Airi; Douillard, Francois P.; de Vos, Willem M. (2020)
    Lacticaseibacillus rhamnosusGG is one of the best studied lactic acid bacteria in the context of probiotic effects.L. rhamnosusGG has been shown to prevent diarrhea in children and adults and has been implicated to have mitigating or preventive effects in several disorders connected to microbiota dysbiosis. The probiotic effects are largely attributed to its adhesive heterotrimeric sortase-dependent pili, encoded by thespaCBA-srtC1gene cluster. Indeed, the strain-specific SpaCBA pili have been shown to contribute to adherence, biofilm formation and host signaling. In this work we set out to generate non-GMO derivatives ofL. rhamnosusGG that adhere stronger to mucus compared to the wild-type strain using chemical mutagenesis. We selected 13 derivatives that showed an increased mucus-adherent phenotype. Deep shotgun resequencing of the strains enabled division of the strains into three classes, two of which revealed SNPs (single nucleotide polymorphisms) in thespaAandspaCgenes encoding the shaft and tip adhesive pilins, respectively. Strikingly, the other class derivatives demonstrated less clear genotype - phenotype relationships, illustrating that pili biogenesis and structure is also affected by other processes. Further characterization of the different classes of derivatives was performed by PacBio SMRT sequencing and RNAseq analysis, which resulted in the identification of molecular candidates driving pilin biosynthesis and functionality. In conclusion, we report on the generation and characterization of three classes of strongly adherentL. rhamnosusGG derivatives that show an increase in adhesion to mucus. These are of special interest as they provide a window on processes and genes driving piliation and its control inL. rhamnosusGG and offer a variety of non-GMO derivatives of this key probiotic strain that are applicable in food products.
  • Kaimio, Mirja; Malkamäki, Sanna; Kaukonen, Maria; Ahonen, Saija; Hytönen, Marjo K.; Rantala, Merja; Lohi, Hannes; Saijonmaa-Koulumies, Leena; Laitinen-Vapaavuori, Outi (2021)
    American Cocker Spaniels (ACSs) develop aural ceruminous gland hyperplasia and ectasia more often than dogs of other breeds. Data on the cause and development of these breed characteristic histopathological changes are lacking. We performed video-otoscopic examinations and dermatological work-up on 28 ACSs, obtained aural biopsies from each dog and assessed the statistical associations between the presence of ceruminous gland hyperplasia and ectasia and disease history, clinical or microbiological findings and underlying cause of otitis externa (OE). Histological lesions of ceruminous gland hyperplasia and ectasia were observed in aural biopsies from 6/13 clinically healthy ears and 13/15 ears with OE from 19/28 examined dogs. Nine of 28 dogs had histologically normal ceruminous glands (odds ratio [OR] 6.2, 95% confidence interval [CI] 1.1-36.6). Bacterial growth in microbiological culture of aural exudate (OR 14.1, 95% CI 2.1-95.3) was associated with ceruminous glandular changes, whereas previous history of OE, cutaneous findings or underlying allergies were not. Pedigree analysis and a genome-wide association study (GWAS) were performed on 18 affected and eight unaffected dogs based on histopathological diagnosis. While the GWAS indicated a tentative, but not statistically significant, association of ceruminous gland hyperplasia and ectasia with chromosome 31, a larger cohort is needed to confirm this preliminary result. Based on our results, ceruminous gland hyperplasia and ectasia may also precede clinical signs of OE in ACSs and a genetic aetiological component is likely Further studies with larger cohorts are warranted to verify our preliminary results. (C) 2021 The Authors. Published by Elsevier Ltd.
  • Ruskamo, Salla; Krokengen, Oda C.; Kowal, Julia; Nieminen, Tuomo; Lehtimäki, Mari; Raasakka, Arne; Dandey, Venkata P.; Vattulainen, Ilpo; Stahlberg, Henning; Kursula, Petri (2020)
    Myelin protein P2 is a peripheral membrane protein of the fatty acid?binding protein family that functions in the formation and maintenance of the peripheral nerve myelin sheath. Several P2 gene mutations cause human Charcot-Marie-Tooth neuropathy, but the mature myelin sheath assembly mechanism is unclear. Here, cryo-EM of myelin-like proteolipid multilayers revealed an ordered three-dimensional (3D) lattice of P2 molecules between stacked lipid bilayers, visualizing supramolecular assembly at the myelin major dense line. The data disclosed that a single P2 layer is inserted between two bilayers in a tight intermembrane space of ?3 nm, implying direct interactions between P2 and two membrane surfaces. X-ray diffraction from P2-stacked bicelle multilayers revealed lateral protein organization, and surface mutagenesis of P2 coupled with structure-function experiments revealed a role for both the portal region of P2 and its opposite face in membrane interactions. Atomistic molecular dynamics simulations of P2 on model membrane surfaces suggested that Arg-88 is critical for P2-membrane interactions, in addition to the helical lid domain. Negatively charged lipid headgroups stably anchored P2 on the myelin-like bilayer surface. Membrane binding may be accompanied by opening of the P2 ?-barrel structure and ligand exchange with the apposing bilayer. Our results provide an unprecedented view into an ordered, multilayered biomolecular membrane system induced by the presence of a peripheral membrane protein from human myelin. This is an important step toward deciphering the 3D assembly of a mature myelin sheath at the molecular level.
  • Mishra, Arjun K.; Megta, Abhin Kumar; Palva, Airi; von Ossowski, Ingemar; Krishnan, Vengadesan (2017)
    SpaE is the predicted basal pilin subunit in the sortase-dependent SpaFED pilus from the gut-adapted and commensal Lactobacillus rhamnosus GG. Thus far, structural characterization of the cell-wall-anchoring basal pilins has remained difficult and has been limited to only a few examples from pathogenic genera and species. To gain a further structural understanding of the molecular mechanisms that are involved in the anchoring and assembly of sortase-dependent pili in less harmful bacteria, L. rhamnosus GG SpaE for crystallization was produced by recombinant expression in Escherichia coli. Although several attempts to crystallize the SpaE protein were unsuccessful, trigonal crystals that diffracted to a resolution of 3.1 angstrom were eventually produced using PEG 3350 as a precipitant and high protein concentrations. Further optimization with a combination of additives led to the generation of SpaE crystals in an orthorhombic form that diffracted to a higher resolution of 1.5 angstrom. To expedite structure determination by SAD phasing, selenium-substituted (orthorhombic) SpaE crystals were grown and X-ray diffraction data were collected to 1.8 angstrom resolution.
  • Apu, Ehsanul Hoque; Akram, Saad Ullah; Rissanen, Jouni; Wan, Hong; Salo, Tuula (2018)
    Desmoglein 3 (Dsg3) is an adhesion receptor in desmosomes, but its role in carcinoma cell migration and invasion is mostly unknown. Our aim was to quantitatively analyse the motion of Dsg3-modified carcinoma cells in 2D settings and in 3D within tumour microenvironment mimicking (TMEM) matrices. We tested mutant constructs of C-terminally truncated Dsg3 (Delta 238 and Delta 560), overexpressed full-length (FL) Dsg3, and empty vector control (Ct) of buccal mucosa squamous cell carcinoma (SqCC/Y1) cells. We captured live cell images and analysed migration velocities and accumulated and Euclidean distances. We compared rodent collagen and Matrigel. with human Myogel TMEM matrices for these parameters in 3D sandwich, in which we also tested the effects of monoclonal antibody AK23, which targets the EC1 domain of Dsg3. In monolayer culture, FL and both truncated constructs migrated faster and had higher accumulated distances than Ct cells. However, in the 3D assays, only the mutants invaded faster relative to Ct cells. Of the mutants, the shorter form (Delta 238) exhibited faster migration and invasion than Delta 560 cells. In the Transwell, all of the cells invaded faster through Myogel than Matrigel coated wells. In 3D sandwich, AK23 antibody inhibited only the invasion of FL cells. We conclude that different experimental 2D and 3D settings can markedly influence the movement of oral carcinoma cells with various Dsg3 modifications.
  • Roselli, Marianna; Finamore, Alberto; Hynönen, Ulla; Palva, Airi; Mengheri, Elena (2016)
    Background: The role of Lactobacillus cell wall components in the protection against pathogen infection in the gut is still largely unexplored. We have previously shown that L. amylovorus DSM 16698(T) is able to reduce the enterotoxigenic F4(+)Escherichia coli (ETEC) adhesion and prevent the pathogen-induced membrane barrier disruption through the regulation of IL-10 and IL-8 expression in intestinal cells. We have also demonstrated that L. amylovorus DSM 16698T protects host cells through the inhibition of NF-kB signaling. In the present study, we investigated the role of L. amylovorus DSM 16698(T) cell wall components in the protection against F4(+)ETEC infection using the intestinal Caco-2 cell line. Methods: Purified cell wall fragments (CWF) from L. amylovorus DSM 16698T were used either as such (uncoated, U-CWF) or coated with S-layer proteins (S-CWF). Differentiated Caco-2/TC7 cells on Transwell filters were infected with F4(+)ETEC, treated with S-CWF or U-CWF, co-treated with S-CWF or U-CWF and F4(+)ETEC for 2.5 h, or pre-treated with S-CWF or U-CWF for 1 h before F4(+)ETEC addition. Tight junction (TJ) and adherens junction (AJ) proteins were analyzed by immunofluorescence and Western blot. Membrane permeability was determined by phenol red passage. Phosphorylated p65-NF-kB was measured by Western blot. Results: We showed that both the pre-treatment with S-CWF and the co- treatment of S-CWF with the pathogen protected the cells from F4(+)ETEC induced TJ and AJ injury, increased membrane permeability and activation of NF-kB expression. Moreover, the U-CWF pre-treatment, but not the co- treatment with F4(+)ETEC, inhibited membrane damage and prevented NF-kB activation. Conclusions: The results indicate that the various components of L. amylovorus DSM 16698(T) cell wall may counteract the damage caused by F4(+)ETEC through different mechanisms. S-layer proteins are essential for maintaining membrane barrier function and for mounting an anti-inflammatory response against F4(+)ETEC infection. U-CWF are not able to defend the cells when they are infected with F4(+)ETEC but may activate protective mechanisms before pathogen infection.
  • Ihermann-Hella, Anneliis; Hirashima, Tsuyoshi; Kupari, Jussi; Kurtzeborn, Kristen; Li, Hao; Kwon, Hyuk Nam; Cebrian, Cristina; Soofi, Abdul; Dapkunas, Arvydas; Miinalainen, Ilkka; Dressler, Gregory R.; Matsuda, Michiyuki; Kuure, Satu (2018)
    The in vivo niche and basic cellular properties of nephron progenitors are poorly described. Here we studied the cellular organization and function of the MAPK/ERK pathway in nephron progenitors. Live-imaging of ERK activity by a Forster resonance energy transfer biosensor revealed a dynamic activation pattern in progenitors, whereas differentiating precursors exhibited sustained activity. Genetic experiments demonstrate that MAPK/ERK activity controls the thickness, coherence, and integrity of the nephron progenitor niche. Molecularly, MAPK/ERK activity regulates niche organization and communication with extracellular matrix through PAX2 and ITGA8, and is needed for CITED1 expression denoting undifferentiated status. MAPK/ERK activation in nephron precursors propels differentiation by priming cells for distal and proximal fates induced by the Wnt and Notch pathways. Thus, our results demonstrate a mechanism through which MAPK/ERK activity controls both progenitor maintenance and differentiation by regulating a distinct set of targets, which maintain the biomechanical milieu of tissue-residing progenitors and prime precursors for nephrogenesis.
  • Teixidó, Joaquin; Hidalgo, Andres; Fagerholm, Susanna (2019)
  • Zhang, Xue; Viitala, Tapani; Harjumäki, Riina; Kartal-Hodzic, Alma; Valle-Delgado, Juan Jose; Österberg, Monika (2021)
    The development of in vitro cell models that mimic cell behavior in organs and tissues is an approach that may have remarkable impact on drug testing and tissue engineering applications in the future. Plant based, chemically unmodified cellulose nanofibrils (CNF) hydrogel is a natural, abundant, and biocompatible material that has attracted great attention for biomedical applications, in particular for threedimensional cell cultures. However, the mechanisms of cell-CNF interactions and factors that affect these interactions are not yet fully understood. In this work, multi-parametric surface plasmon resonance (SPR) was used to study how the adsorption of human hepatocellular carcinoma (HepG2) cells on CNF films is affected by the different proteins and components of the cell medium. Both human recombinant laminin 521 (LN-521, a natural protein of the extracellular matrix) and poly -L-lysine (PLL) adsorbed on CNF films and enhanced the attachment of HepG2 cells. Cell medium components (glucose and amino acids) and serum proteins (fetal bovine serum, FBS) also adsorbed on both bare CNF and on protein-coated CNF substrates. However, the adsorption of FBS hindered the attachment of HepG2 cells to LN-521and PLLcoated CNF substrates, suggesting that serum proteins blocked the formation of laminin-integrin bonds and decreased favorable PLL-cell electrostatic interactions. This work sheds light on the effect of different factors on cell attachment to CNF, paving the way for the utilization and optimization of CNF-based materials for different tissue engineering applications. (C) 2020 The Authors. Published by Elsevier Inc.
  • Hjerppe, J; Perea-Lowery, L; Lassila, LVJ; Vallittu, PK (2021)
    The objective of this study was to compare potassium hydrogen difluoride (KHF2) etching for zirconia with commonly used surface roughening and chemical bonding methods (silane, MDP-monomer primer) for resin-based luting cement bonding to zirconia. Zirconia specimens were divided into six groups (n=10) according to surface treatment and bonding procedures, with and without thermocycling (6,000 cycles, 5-55 degrees C): 1) air-borne particle abrasion with alumina+MDP-monomer (ABP), 2) air-borne particle abrasion with silica-coated trialuminium trioxide+silane (ABPR-S) and 3) KHF2 etching+silane (ETC). Surface roughness and bond strength (SBS-test) for dry and thermocycled specimens were measured. SBS did not vary statistically between the dry groups, but thermocycling decreased the bond strengths of all the tested methods (p