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Regenerative Therapy Dec 2024Mesenchymal stem cells (MSCs) are increasingly used for intra-articular injections in the treatment of knee osteoarthritis. The aim of this study was to use scanning...
INTRODUCTION
Mesenchymal stem cells (MSCs) are increasingly used for intra-articular injections in the treatment of knee osteoarthritis. The aim of this study was to use scanning electron microscopy (SEM) to compare the morphological characteristics of synovial and adipose MSCs.
METHODS
Synovium and adipose tissues were concurrently harvested from eight patients with knee osteoarthritis. Suspensions of both synovial and adipose MSCs were examined to identify the presence of microspikes. In addition to this study, the MSC suspensions in four patients were applied to abraded porcine cartilage discs and observed 10 s, 10 min, and 1 h later.
RESULTS
The median percentage of cells exhibiting microspikes was 14% for synovial MSC suspensions and 13% for adipose MSC suspensions; this difference was not statistically significant (n = 8). No notable differences were detected in the number of adherent cells or in the proportion of cells displaying microspikes or pseudopodia. Strong correlations were found between the proportion of cells with pseudopodia and the number of attached cells for both synovial (r = 0.92, n = 12) and adipose (r = 0.86, n = 12) MSCs, with no significant difference in the correlation coefficients between the two groups.
CONCLUSION
SEM analysis revealed no obvious differences in morphological characteristics during MSC adhesion to cartilage for either synovial or adipose MSCs.
PubMed: 38756702
DOI: 10.1016/j.reth.2024.04.012 -
PLoS Computational Biology May 2024Filopodia are thin synaptic protrusions that have been long known to play an important role in early development. Recently, they have been found to be more abundant in...
Filopodia are thin synaptic protrusions that have been long known to play an important role in early development. Recently, they have been found to be more abundant in the adult cortex than previously thought, and more plastic than spines (button-shaped mature synapses). Inspired by these findings, we introduce a new model of synaptic plasticity that jointly describes learning of filopodia and spines. The model assumes that filopodia exhibit strongly competitive learning dynamics -similarly to additive spike-timing-dependent plasticity (STDP). At the same time it proposes that, if filopodia undergo sufficient potentiation, they consolidate into spines. Spines follow weakly competitive learning, classically associated with multiplicative, soft-bounded models of STDP. This makes spines more stable and sensitive to the fine structure of input correlations. We show that our learning rule has a selectivity comparable to additive STDP and captures input correlations as well as multiplicative models of STDP. We also show how it can protect previously formed memories and perform synaptic consolidation. Overall, our results can be seen as a phenomenological description of how filopodia and spines could cooperate to overcome the individual difficulties faced by strong and weak competition mechanisms.
Topics: Pseudopodia; Neuronal Plasticity; Models, Neurological; Dendritic Spines; Learning; Animals; Humans; Computational Biology; Synapses; Neurons; Action Potentials
PubMed: 38743789
DOI: 10.1371/journal.pcbi.1012110 -
Communications Biology May 2024Amphiphysin 2 (BIN1) is a membrane and actin remodeling protein mutated in congenital and adult centronuclear myopathies. Here, we report an unexpected function of this...
Amphiphysin 2 (BIN1) is a membrane and actin remodeling protein mutated in congenital and adult centronuclear myopathies. Here, we report an unexpected function of this N-BAR domain protein BIN1 in filopodia formation. We demonstrated that BIN1 expression is necessary and sufficient to induce filopodia formation. BIN1 is present at the base of forming filopodia and all along filopodia, where it colocalizes with F-actin. We identify that BIN1-mediated filopodia formation requires IRSp53, which allows its localization at negatively-curved membrane topologies. Our results show that BIN1 bundles actin in vitro. Finally, we identify that BIN1 regulates the membrane-to-cortex architecture and functions as a molecular platform to recruit actin-binding proteins, dynamin and ezrin, to promote filopodia formation.
Topics: Pseudopodia; Actins; Tumor Suppressor Proteins; Humans; Adaptor Proteins, Signal Transducing; Animals; Nerve Tissue Proteins; Cell Membrane; Mice; Nuclear Proteins
PubMed: 38724689
DOI: 10.1038/s42003-024-06168-8 -
Life Science Alliance Jul 2024Septins are cytoskeletal proteins that participate in cell adhesion, migration, and polarity establishment. The septin subunit SEPT9 directly interacts with the single...
Septins are cytoskeletal proteins that participate in cell adhesion, migration, and polarity establishment. The septin subunit SEPT9 directly interacts with the single LIM domain of epithelial protein lost in neoplasm (EPLIN), an actin-bundling protein. Using a human SEPT9 KO fibroblast cell line, we show that cell adhesion and migration are regulated by the interplay between both proteins. The low motility of SEPT9-depleted cells could be partly rescued by increased levels of EPLIN. The normal organization of actin-related filopodia and stress fibers was directly dependent on the expression level of SEPT9 and EPLIN. Increased levels of SEPT9 and EPLIN enhanced the size of focal adhesions in cell protrusions, correlating with stabilization of actin bundles. Conversely, decreased levels had the opposite effect. Our work thus establishes the interaction between SEPT9 and EPLIN as an important link between the septin and the actin cytoskeleton, influencing cell adhesion, motility, and migration.
Topics: Humans; Septins; Cell Movement; Cell Adhesion; Fibroblasts; LIM Domain Proteins; Focal Adhesions; Cytoskeletal Proteins; Pseudopodia; Actin Cytoskeleton; Cell Line; Actins; Stress Fibers
PubMed: 38719752
DOI: 10.26508/lsa.202201686 -
Heliyon May 2024Magnesium-based composites are a focal point in biomaterials research. However, the rapid degradation rate of magnesium alloys does not align with the healing time of...
Magnesium-based composites are a focal point in biomaterials research. However, the rapid degradation rate of magnesium alloys does not align with the healing time of bone tissue. Additionally, the host reaction caused by magnesium implantation hampers its full osteogenic potential. To maintain an appropriate microenvironment, it is important to enhance both corrosion resistance and osteogenic activity of the magnesium matrix. In this study, a composite scaffold composed of mineralized collagen and magnesium alloy was utilized to investigate the regulatory effect of mineralized collagen on mouse macrophages and evaluate its impact on mouse bone marrow mesenchymal stem cells in terms of osteogenesis, immune response, and macrophage-induced osteogenic differentiation. This experiment examined the biocompatibility of mouse bone marrow mesenchymal stem cells and macrophage-induced osteogenic differentiation in vitro, and examined the expression levels of relevant pathways proteins. Magnesium calcium alloys/mineralized collagen exhibited extensive spreading, facilitated by broad and abundant pseudopodia that firmly adhered them to the material surface and promoted growth and pseudopodia formation. The findings revealed that magnesium calcium alloy/mineralized collagen scaffold materials induced osteogenic differentiation mainly through M2 polarization of macrophages. This effect was mainly mediated by promoting the integrin α2β1-FAK-ERK1/2 signaling pathways and inhibiting the RANK signaling pathways.
PubMed: 38711636
DOI: 10.1016/j.heliyon.2024.e30279 -
Bioactive Materials Jul 2024Magnesium phosphate bone cements (MPC) have been recognized as a viable alternative for bone defect repair due to their high mechanical strength and biodegradability....
Magnesium phosphate bone cements (MPC) have been recognized as a viable alternative for bone defect repair due to their high mechanical strength and biodegradability. However, their poor porosity and permeability limit osteogenic cell ingrowth and vascularization, which is critical for bone regeneration. In the current study, we constructed a novel hierarchically-porous magnesium phosphate bone cement by incorporating extracellular matrix (ECM)-mimicking electrospun silk fibroin (SF) nanofibers. The SF-embedded MPC (SM) exhibited a heterogeneous and hierarchical structure, which effectively facilitated the rapid infiltration of oxygen and nutrients as well as cell ingrowth. Besides, the SF fibers improved the mechanical properties of MPC and neutralized the highly alkaline environment caused by excess magnesium oxide. Bone marrow stem cells (BMSCs) adhered excellently on SM, as illustrated by formation of more pseudopodia. CCK8 assay showed that SM promoted early proliferation of BMSCs. Our study also verified that SM increased the expression of OPN, RUNX2 and BMP2, suggesting enhanced osteogenic differentiation of BMSCs. We screened for osteogenesis-related pathways, including FAK signaing, Wnt signaling and Notch signaling, and found that SM aided in the process of bone regeneration by suppressing the Notch signaling pathway, proved by the downregulation of NICD1, Hes1 and Hey2. In addition, using a bone defect model of rat calvaria, the study revealed that SM exhibited enhanced osteogenesis, bone ingrowth and vascularization compared with MPC alone. No adverse effect was found after implantation of SM . Overall, our novel SM exhibited promising prospects for the treatment of critical-sized bone defects.
PubMed: 38698920
DOI: 10.1016/j.bioactmat.2024.03.021 -
Proceedings of the National Academy of... Apr 2024Regulation of subcellular messenger (m)RNA localization is a fundamental biological mechanism, which adds a spatial dimension to the diverse layers of...
Regulation of subcellular messenger (m)RNA localization is a fundamental biological mechanism, which adds a spatial dimension to the diverse layers of post-transcriptional control of gene expression. The cellular compartment in which mRNAs are located may define distinct aspects of the encoded proteins, ranging from production rate and complex formation to localized activity. Despite the detailed roles of localized mRNAs that have emerged over the past decades, the identity of factors anchoring mRNAs to subcellular domains remains ill-defined. Here, we used an unbiased method to profile the RNA-bound proteome in migrating endothelial cells (ECs) and discovered that the plasma membrane (PM)-associated scaffolding protein A-kinase anchor protein (AKAP)12 interacts with various mRNAs, including transcripts encoding kinases with Actin remodeling activity. In particular, AKAP12 targets a transcript coding for the kinase Abelson Tyrosine-Protein Kinase 2 (ABL2), which we found to be necessary for adequate filopodia formation and angiogenic sprouting. Moreover, we demonstrate that AKAP12 is necessary for anchoring mRNA to the PM and show that in the absence of AKAP12, the translation efficiency of mRNA is reduced. Altogether, our work identified a unique post-transcriptional function for AKAP12 and sheds light into mechanisms of spatial control of gene expression.
Topics: A Kinase Anchor Proteins; RNA, Messenger; Humans; Animals; Protein Biosynthesis; Endothelial Cells; Pseudopodia; Mice; Cell Cycle Proteins; Cell Membrane; Cell Movement
PubMed: 38652739
DOI: 10.1073/pnas.2320609121 -
International Journal of Molecular... Apr 2024Breast cancer, particularly triple-negative breast cancer (TNBC), poses a global health challenge. Emerging evidence has established a positive association between...
Breast cancer, particularly triple-negative breast cancer (TNBC), poses a global health challenge. Emerging evidence has established a positive association between elevated levels of stearoyl-CoA desaturase 1 (SCD1) and its product oleate (OA) with cancer development and metastasis. SCD1/OA leads to alterations in migration speed, direction, and cell morphology in TNBC cells, yet the underlying molecular mechanisms remain elusive. To address this gap, we aim to investigate the impact of OA on remodeling the actin structure in TNBC cell lines, and the underlying signaling. Using TNBC cell lines and bioinformatics tools, we show that OA stimulation induces rapid cell membrane ruffling and enhances filopodia formation. OA treatment triggers the subcellular translocation of Arp2/3 complex and Cdc42. Inhibiting Cdc42, not the Arp2/3 complex, effectively abolishes OA-induced filopodia formation and cell migration. Additionally, our findings suggest that phospholipase D is involved in Cdc42-dependent filopodia formation and cell migration. Lastly, the elevated expression of Cdc42 in breast tumor tissues is associated with a lower survival rate in TNBC patients. Our study outlines a new signaling pathway in the OA-induced migration of TNBC cells, via the promotion of Cdc42-dependent filopodia formation, providing a novel insight for therapeutic strategies in TNBC treatment.
Topics: Humans; Oleic Acid; Triple Negative Breast Neoplasms; Pseudopodia; Cell Movement; Actins; Actin-Related Protein 2-3 Complex
PubMed: 38612766
DOI: 10.3390/ijms25073956 -
Journal of Autoimmunity May 2024Epidemiological studies show that cardiovascular events related to platelet hyperactivity remain the leading causes of death among multiple sclerosis (MS) patients....
Epidemiological studies show that cardiovascular events related to platelet hyperactivity remain the leading causes of death among multiple sclerosis (MS) patients. Quantitative or structural changes of platelet cytoskeleton alter their morphology and function. Here, we demonstrated, for the first time, the structural changes in MS platelets that may be related to their hyperactivity. MS platelets were found to form large aggregates compared to control platelets. In contrast to the control, the images of overactivated, irregularly shaped MS platelets show changes in the cytoskeleton architecture, fragmented microtubule rings. Furthermore, MS platelets have long and numerous pseudopodia rich in actin filaments. We showed that MS platelets and megakaryocytes, overexpress β1-tubulin and β-actin mRNAs and proteins and have altered post-translational modification patterns. Moreover, we identified two previously undisclosed mutations in the gene encoding β1-tubulin in MS. We propose that the demonstrated structural changes of platelet cytoskeleton enhance their ability to adhere, aggregate, and degranulate fueling the risk of adverse cardiovascular events in MS.
Topics: Humans; Multiple Sclerosis; Blood Platelets; Tubulin; Female; Cytoskeleton; Cytoskeletal Proteins; Adult; Male; Middle Aged; Actins; Megakaryocytes; Protein Processing, Post-Translational; Mutation
PubMed: 38520895
DOI: 10.1016/j.jaut.2024.103204 -
Open Biology Mar 2024Fascin-1-mediated actin-bundling activity is central to the generation of plasma membrane protrusions required for cell migration. Dysregulated formation of cellular...
Fascin-1-mediated actin-bundling activity is central to the generation of plasma membrane protrusions required for cell migration. Dysregulated formation of cellular protrusions is observed in metastatic cancers, where they are required for increased invasiveness, and is often correlated with increased Fascin-1 abundance. Therefore, there is interest in generating therapeutic Fascin-1 inhibitors. We present the identification of Nb 3E11, a nanobody inhibitor of Fascin-1 actin-bundling activity and filopodia formation. The crystal structure of the Fascin-1/Nb 3E11 complex reveals the structural mechanism of inhibition. Nb 3E11 occludes an actin-binding site on the third β-trefoil domain of Fascin-1 that is currently not targeted by chemical inhibitors. Binding of Nb 3E11 to Fascin-1 induces a conformational change in the adjacent domains to stabilize Fascin-1 in an inhibitory state similar to that adopted in the presence of small-molecule inhibitors. Nb 3E11 could be used as a tool inhibitor molecule to aid in the development of Fascin-1 targeted therapeutics.
Topics: Actins; Pseudopodia; Protein Binding; Cell Movement; Carrier Proteins; Microfilament Proteins
PubMed: 38503329
DOI: 10.1098/rsob.230376