Synaptic cell adhesion molecules contribute to the pathogenesis and progression of fragile X syndrome.

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and a monogenic cause of autism spectrum disorders. Deficiencies in the fragile X messenger ribonucleoprotein, encoded by the FMR1 gene, lead to various anatomical and pathophysiological abnormalities and behavioral deficits, such as spine dysmorphogenesis and learning and memory impairments. Synaptic cell adhesion molecules (CAMs) play crucial roles in synapse formation and neural signal transmission by promoting the formation of new synaptic contacts, accurately organizing presynaptic and postsynaptic protein complexes, and ensuring the accuracy of signal transmission. Recent studies have implicated synaptic CAMs such as the immunoglobulin superfamily, N-cadherin, leucine-rich repeat proteins, and neuroligin-1 in the pathogenesis of FXS and found that they contribute to defects in dendritic spines and synaptic plasticity in FXS animal models. This review systematically summarizes the biological associations between nine representative synaptic CAMs and FMRP, as well as the functional consequences of the interaction, to provide new insights into the mechanisms of abnormal synaptic development in FXS.

GAS6-AS1 drives bladder cancer progression by increasing MMP7 expression in a ceRNA- and RBP-dependent manner.

Numerous recent studies have underscored the indispensable roles of long non-coding RNAs (lncRNAs) in various diseases. However, their precise mechanisms in urinary bladder cancer (UBC) remain to be further elucidated. To delve into this inquiry, online databases were analyzed to identify differentially expressed lncRNAs in UBC, followed by the functional experiments in vivo and in vitro functional experiments. GAS6-AS1 exhibited high expression levels in UBC tissues and was shown to regulate the proliferation, migration, invasion, and cell cycle progression of UBC cells in vitro and in vivo. Then, a series of molecular biology experiments, including RNA pull-down, dual-luciferase reporter gene assays, RNA immunoprecipitation (RIP) assays, fluorescent in situ hybridization (FISH), and the triplex-capture assay demonstrated its interaction with miR-367-3p and PRC1. Mechanistically, GAS6-AS1 was found to enhance MMP7 expression by sequestering miR-367-3p. Moreover, GAS6-AS1 inhibited APC transcription by binding with PRC1, thereby activating several oncogenes downstream of the WNT pathway. To sum up, GAS6-AS1 promotes UBC progression through two distinct axes: the GAS6-AS1/miR-367-3p/MMP7 axis and the GAS6-AS1/PRC1/APC/Wnt/MMP7 axis, respectively. As a potential biomarker for UBC, GAS6-AS1 holds promising prospects for the diagnosis, treatment, and prognosis of UBC.

MicroRNAs Associated with IgLON Cell Adhesion Molecule Expression.

The IgLON family of cell adhesion molecules consists of five members (LSAMP, OPCML, neurotrimin, NEGR1, and IgLON5) discovered as supporters of neuronal development, axon growth and guidance, and synapse formation and maintenance. Tumour suppression properties have recently been emerging based on antiproliferative effects through the modulation of oncogenic pathways. Available evidence endorses a role for non-coding RNAs or microRNAs as relevant controllers of IgLON molecule expression that can impact their critical physiological and pathological roles. Current findings support a function for long non-coding RNAs and microRNAs in the modulation of LSAMP expression in cell senescence, cancer biogenesis, addiction, and pulmonary hypertension. For OPCML, data point to a role for several microRNAs in the control of tumorigenesis. MicroRNAs were detected in neurotrimin-mediated functions in cancer biogenesis and in Schwann cell responses to peripheral nerve injury. For NEGR1, studies have mainly investigated microRNA involvement in neuronal responses to ischaemic injury, although data also exist about tumorigenesis and endothelial cell dysfunction. For IgLON5, information is only available about microRNA involved in myocardial infarction. In conclusion, despite much information being still missing and further research needed, the emerging picture favours a model in which non-coding RNAs exert a crucial role in modulating IgLON expression, ultimately affecting their important physiological functions.

Functionalization of Alginate Hydrogels with a Multifunctional Peptide Supports Mesenchymal Stem Cell Adhesion and Reduces Bacterial Colonization.

Hydrogels with cell adhesive moieties stand out as promising materials to enhance tissue healing and regeneration. Nonetheless, bacterial infections of the implants represent an unmet major concern. In the present work, we developed an alginate hydrogel modified with a multifunctional peptide containing the RGD cell adhesive motif in combination with an antibacterial peptide derived from the 1-11 region of lactoferrin (LF). The RGD-LF branched peptide was successfully anchored to the alginate backbone by carbodiimide chemistry, as demonstrated by 1H NMR and fluorescence measurements. The functionalized hydrogel presented desirable physicochemical properties (porosity, swelling and rheological behavior) to develop biomaterials for tissue engineering. The viability of mesenchymal stem cells (MSCs) on the peptide-functionalized hydrogels was excellent, with values higher than 85% at day 1, and higher than 95% after 14 days in culture. Moreover, the biological characterization demonstrated the ability of the hydrogels to significantly enhance ALP activity of MSCs as well as to decrease bacterial colonization of both Gram-positive and Gram-negative models. Such results prove the potential of the functionalized hydrogels as novel biomaterials for tissue engineering, simultaneously displaying cell adhesive activity and the capacity to prevent bacterial contamination, a dual bioactivity commonly not found for these types of hydrogels.

Protective and curative effects of unconjugated bilirubin on gene expression of LOX-1 and iNOS in the heart of rats receiving high-fat diet and low dose streptozotocin: a histomorphometric approach.

BACKGROUND: Atherosclerosis is a chronic inflammatory condition affecting the large arteries and is a major cause of cardiovascular diseases (CVDs) globally. Increased levels of adhesion molecules in cardiac tissue serve as prognostic markers for coronary artery occlusion risk. Given the antioxidant properties of bilirubin and its inverse correlation with atherosclerosis, this study aimed to assess the beneficial effects of bilirubin on atherosclerotic indices and heart structure in high-fat diet-fed diabetic rats with atherosclerosis. METHODS: Atherosclerosis was induced in three out of five groups of adult male Sprague Dawley rats through a 14-week period of high-fat diet (HFD) consumption and a single low dose of streptozotocin (STZ) (35 mg/kg). The atherosclerotic rats were then treated with intraperitoneal administration of 10 mg/kg/day bilirubin for either 6 or 14 weeks (treated and protected groups, respectively), or the vehicle. Two additional groups served as the control and bilirubin-treated rats. Subsequently, the mRNA expression levels of vascular cell adhesion molecule 1 (VCAM-1), intercellular adhesion molecule 1 (ICAM-1), lectin-like LDL receptor 1 (LOX-1), and the inducible nitric oxide synthase (iNOS) were analyzed using quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). Histopathological and stereological analyses were performed to assess changes in the heart structure. RESULTS: Bilirubin significantly decreased the expression of VCAM-1, ICAM-1, LOX-1, and iNOS genes in the treated group. Moreover, bilirubin mitigated pathological damage in the left ventricle of the heart. Stereological analysis revealed a decrease in the left ventricle and myocardium volume, accompanied by an increase in vessel volume in rats treated with bilirubin. CONCLUSION: These findings demonstrate that mild hyperbilirubinemia can protect against the progression of atherosclerosis and heart failure by improving lipid profile, modulating adhesion molecules, LOX-1, and iNOS gene expression levels.

Long-Term In Vitro Culture Alters Gene Expression Pattern of Genes Involved in Ontological Groups Representing Cellular Processes.

The oviduct provides an optimal environment for the final preparation, transport, and survival of gametes, the fertilization process, and early embryonic development. Most of the studies on reproduction are based on in vitro cell culture models because of the cell's accessibility. It creates opportunities to explore the complexity of directly linked processes between cells. Previous studies showed a significant expression of genes responsible for cell differentiation, maturation, and development during long-term porcine oviduct epithelial cells (POECs) in vitro culture. This study aimed at establishing the transcriptomic profile and comprehensive characteristics of porcine oviduct epithelial cell in vitro cultures, to compare changes in gene expression over time and deliver information about the expression pattern of genes highlighted in specific GO groups. The oviduct cells were collected after 7, 15, and 30 days of in vitro cultivation. The transcriptomic profile of gene expression was compared to the control group (cells collected after the first day). The expression of COL1A2 and LOX was enhanced, while FGFBP1, SERPINB2, and OVGP1 were downregulated at all selected intervals of cell culture in comparison to the 24-h control (p-value < 0.05). Adding new detailed information to the reproductive biology field about the diversified transcriptome profile in POECs may create new future possibilities in infertility treatments, including assisted reproductive technique (ART) programmes, and may be a valuable tool to investigate the potential role of oviduct cells in post-ovulation events.

In Vivo PET Detection of Lung Micrometastasis in Mice by Targeting Endothelial VCAM-1 Using a Dual-Contrast PET/MRI Probe.

Current clinical diagnostic imaging methods for lung metastases are sensitive only to large tumours (1-2 mm cross-sectional diameter), and early detection can dramatically improve treatment. We have previously demonstrated that an antibody-targeted MRI contrast agent based on microparticles of iron oxide (MPIO; 1 µm diameter) enables the imaging of endothelial vascular cell adhesion molecule-1 (VCAM-1). Using a mouse model of lung metastasis, upregulation of endothelial VCAM-1 expression was demonstrated in micrometastasis-associated vessels but not in normal lung tissue, and binding of VCAM-MPIO to these vessels was evident histologically. Owing to the lack of proton MRI signals in the lungs, we modified the VCAM-MPIO to include zirconium-89 (89Zr, t1/2 = 78.4 h) in order to allow the in vivo detection of lung metastases by positron emission tomography (PET). Using this new agent (89Zr-DFO-VCAM-MPIO), it was possible to detect the presence of micrometastases within the lung in vivo from ca. 140 µm in diameter. Histological analysis combined with autoradiography confirmed the specific binding of the agent to the VCAM-1 expressing vasculature at the sites of pulmonary micrometastases. By retaining the original VCAM-MPIO as the basis for this new molecular contrast agent, we have created a dual-modality (PET/MRI) agent for the concurrent detection of lung and brain micrometastases.

The Role of Lutheran/Basal Cell Adhesion Molecule in Hematological Diseases and Tumors.

Cell adhesion is a dynamic process that plays a fundamental role in cell proliferation, maintenance, differentiation, and migration. Basal cell adhesion molecule (BCAM), also known as Lutheran (Lu), belongs to the immunoglobulin superfamily of cell adhesion molecules. Lu/BCAM, which is widely expressed in red blood cells, endothelial cells, smooth muscle cells and epithelial cells across various tissues, playing a crucial role in many cellular processes, including cell adhesion, cell motility and cell migration. Moreover, Lu/BCAM, dysregulated in many diseases, such as blood diseases and various types of cancer, may act as a biomarker and target for the treatment of these diseases. This review explores the significance of Lu/BCAM in cell adhesion and its potential as a novel target for treating hematological diseases and tumors.

An evaluation of inflammatory and endothelial dysfunction markers as determinants of peripheral arterial disease in those with diabetes mellitus.

The most serious long-term effects of diabetes is peripheral artery disease (PAD) which increases the chance of developing diabetic foot ulcers, gangrene and even lower limb amputation. The clinical manifestations of PAD which are typically not revealed until symptoms like intermittent claudication, rest pain and ischemic gangrene develop, are not present in majority of diabetes mellitus patients with PAD due to diabetic peripheral neuropathy. Therefore, current study is aimed to evaluate the inflammatory and endothelial dysfunction markers with their correlation to biomarkers that can help for in-time diagnosis and efficient prognosis of developing diabetes-associated PAD. Enzyme-linked immunosorbent assay was used to evaluate the interlukin-6, interlukin-8, intercellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM) in PAD with diabetes group, diabetic group and healthy individual group while biomarkers were measured by kit method. It was observed that serum IL-6, IL-8, ICAM and VCAM levels in type II diabetes mellitus (T2DM) with PAD patients were increased significantly (85.93, 597.08, 94.80 and 80.66) as compared to T2DM patients (59.52, 231.34, 56.88 and 50.19) and healthy individuals (4.81, 16.93, 5.55 and 5.16). The overall means for the parameters, IL-6, IL-8, ICAM, VCAM, urea, S/creatinine, CK-MB, AST, ALT, cholesterol, triglyceride, HDL, LDL, PT, aPTT, INR, HbA1C, and CRP within all groups were significantly (P < 0.05) different from each other. Therefore, it was concluded that the change in IL-6, IL-8, ICAM and VCAM can serve as an accurate diagnostic indicator and successful treatment.

Mechanisms of microbial co-aggregation in mixed anaerobic cultures.

Co-aggregation of anaerobic microorganisms into suspended microbial biofilms (aggregates) serves ecological and biotechnological functions. Tightly packed aggregates of metabolically interdependent bacteria and archaea play key roles in cycling of carbon and nitrogen. Additionally, in biotechnological applications, such as wastewater treatment, microbial aggregates provide a complete metabolic network to convert complex organic material. Currently, experimental data explaining the mechanisms behind microbial co-aggregation in anoxic environments is scarce and scattered across the literature. To what extent does this process resemble co-aggregation in aerobic environments? Does the limited availability of terminal electron acceptors drive mutualistic microbial relationships, contrary to the commensal relationships observed in oxygen-rich environments? And do co-aggregating bacteria and archaea, which depend on each other to harvest the bare minimum Gibbs energy from energy-poor substrates, use similar cellular mechanisms as those used by pathogenic bacteria that form biofilms? Here, we provide an overview of the current understanding of why and how mixed anaerobic microbial communities co-aggregate and discuss potential future scientific advancements that could improve the study of anaerobic suspended aggregates. KEY POINTS: • Metabolic dependency promotes aggregation of anaerobic bacteria and archaea • Flagella, pili, and adhesins play a role in the formation of anaerobic aggregates • Cyclic di-GMP/AMP signaling may trigger the polysaccharides production in anaerobes.

Following the Evolutionary Paths of Dscam1 Proteins toward Highly Specific Homophilic Interactions.

Many adhesion proteins, evolutionarily related through gene duplication, exhibit distinct and precise interaction preferences and affinities crucial for cell patterning. Yet, the evolutionary paths by which these proteins acquire new specificities and prevent cross-interactions within their family members remain unknown. To bridge this gap, this study focuses on Drosophila Down syndrome cell adhesion molecule-1 (Dscam1) proteins, which are cell adhesion proteins that have undergone extensive gene duplication. Dscam1 evolved under strong selective pressure to achieve strict homophilic recognition, essential for neuronal self-avoidance and patterning. Through a combination of phylogenetic analyses, ancestral sequence reconstruction, and cell aggregation assays, we studied the evolutionary trajectory of Dscam1 exon 4 across various insect lineages. We demonstrated that recent Dscam1 duplications in the mosquito lineage bind with strict homophilic specificities without any cross-interactions. We found that ancestral and intermediate Dscam1 isoforms maintained their homophilic binding capabilities, with some intermediate isoforms also engaging in promiscuous interactions with other paralogs. Our results highlight the robust selective pressure for homophilic specificity integral to the Dscam1 function within the process of neuronal self-avoidance. Importantly, our study suggests that the path to achieving such selective specificity does not introduce disruptive mutations that prevent self-binding but includes evolutionary intermediates that demonstrate promiscuous heterophilic interactions. Overall, these results offer insights into evolutionary strategies that underlie adhesion protein interaction specificities.

Molecular Crosstalk Between Adherens Junction Proteins, E-cadherin and Nectin-4.

Cell-cell junctions formed by the association of cell adhesion molecules facilitate physiological events necessary for growth and development of multicellular organisms. Among them, cadherins and nectins organize and assemble to form adherens junction, which thereby mechanically couples interacting cells. A detailed understanding of the crosstalk involving these cell adhesion molecules is fundamental to the study of the various developmental processes. Although, cadherins and nectins can recruit each other in the adherens junction through an interplay of cytoplasmic adaptor molecules, here, we report a direct interaction between N-terminal extracellular domains of E-cadherin and nectin-4 as demonstrated by surface plasmon resonance (SPR) and Atomic Force Microscopy (AFM)-based single molecule force spectroscopy (SMFS). Kinetic studies using SPR demonstrate the binding between the ectodomains of E-cadherin and nectin-4 with a KD of 3.7 ± 0.7 µM and KD of 5.4 ± 0.2 µM (reciprocal experiment). AFM-based SMFS experiments also support interaction between the ectodomains of E-cadherin and nectin-4 with the koff value of 31.48 ± 1.53 s-1 and the lifetime of the complex of 0.036 ± 0.0026 s. We thus propose a cell adhesion mechanism mediated by E-cadherin and nectin-4, which can have functional significance in early embryogenesis as evident from the expression pattern of both the proteins during early development.

E-cadherin tunes tissue mechanical behavior before and during morphogenetic tissue flows.

Adhesion between epithelial cells enables the remarkable mechanical behavior of epithelial tissues during morphogenesis. However, it remains unclear how cell-cell adhesion influences mechanics in both static and dynamically flowing confluent epithelial tissues. Here, we systematically modulate E-cadherin-mediated adhesion in the Drosophila embryo and study the effects on the mechanical behavior of the germband epithelium before and during dramatic tissue remodeling and flow associated with body axis elongation. Before axis elongation, we find that increasing E-cadherin levels produces tissue comprising more elongated cells and predicted to be more fluid-like, providing reduced resistance to tissue flow. During axis elongation, we find that the dominant effect of E-cadherin is tuning the speed at which cells proceed through rearrangement events. Before and during axis elongation, E-cadherin levels influence patterns of actomyosin-dependent forces, supporting the notion that E-cadherin tunes tissue mechanics in part through effects on actomyosin. Notably, the effects of ∼4-fold changes in E-cadherin levels on overall tissue structure and flow are relatively weak, suggesting that the system is tolerant to changes in absolute E-cadherin levels over this range where an intact tissue is formed. Taken together, these findings reveal dual-and sometimes opposing-roles for E-cadherin-mediated adhesion in controlling tissue structure and dynamics in vivo, which result in unexpected relationships between adhesion and flow in confluent tissues.

Preventing biofouling in microalgal photobioreactors.

Photobioreactors (PBRs) are used to grow the light-requiring microalgae in diverse commercial processes. Often, they are operated as continuous culture over months period. However, with time, biofouling layer develops on the inner surfaces of their walls. The fouling layer formation deteriorates the PBR performance as foulants reduce light penetration in it. Light is essential for photosynthetic cultures, and a deterioration in lighting adversely impacts algae growth and biomass productivity. Fouling requires a frequent shutdown to clean the PBR and add to the environmental impact of the operation by generating many wastewaters contaminated with the cleaning chemicals. Antibiofouling coatings could be used to modify the surfaces of existing and future PBRs. Therefore, transparent and non-toxic fouling-release coatings, produced using hydrogel technology, could transform the existing PBRs into efficient and enduring microalgae culture systems, requiring only the application of the coating to the inner walls, without additional investments in new PBRs.

Oxalate regulates crystal-cell adhesion and macrophage metabolism via JPT2/PI3K/AKT signaling to promote the progression of kidney stones.

Oxalate is an organic dicarboxylic acid that is a common component of plant foods. The kidneys are essential organs for oxalate excretion, but excessive oxalates may induce kidney stones. Jupiter microtubule associated homolog 2 (JPT2) is a critical molecule in Ca2+ mobilization, and its intrinsic mechanism in oxalate exposure and kidney stones remains unclear. This study aimed to reveal the mechanism of JPT2 in oxalate exposure and kidney stones. Genetic approaches were used to control JPT2 expression in cells and mice, and the JPT2 mechanism of action was analyzed using transcriptomics and untargeted metabolomics. The results showed that oxalate exposure triggered the upregulation of JPT2, which is involved in nicotinic acid adenine dinucleotide phosphate (NAADP)-mediated Ca2+ mobilization. Transcriptomic analysis revealed that cell adhesion and macrophage inflammatory polarization were inhibited by JPT2 knockdown, and these were dominated by phosphatidylinositol 3-kinase (PI3K)/AKT signaling, respectively. Untargeted metabolomics indicated that JPT2 knockdown inhibited the production of succinic acid semialdehyde (SSA) in macrophages. Furthermore, JPT2 deficiency in mice inhibited kidney stones mineralization. In conclusion, this study demonstrates that oxalate exposure facilitates kidney stones by promoting crystal-cell adhesion, and modulating macrophage metabolism and inflammatory polarization via JPT2/PI3K/AKT signaling.

Ultrasound molecular imaging for early detection of acute renal ischemia-reperfusion injury.

Background: Microcirculatory perfusion disorder and inflammatory response are critical links in acute kidney injury (AKI). We aim to construct anti-vascular cell adhesion molecule-1(VCAM-1) targeted microbubbles (TM) to monitor renal microcirculatory perfusion and inflammatory response. Methods: TM carrying VCAM-1 polypeptide was constructed by biological coupling. The binding ability of TM to human umbilical vein endothelial cells (HUVECs) was detected. Bilateral renal ischemia-reperfusion injury (IRI) models of mice were established to evaluate microcirculatory perfusion and inflammatory response using TM. Thirty-six mice were randomly divided into six groups according to the different reperfusion time (0.5, 2, 6, 12, and 24 h) and sham-operated group (Sham group). The correlation of TM imaging with serum and histopathological biomarkers was investigated. Results: TM has advantages such as uniform distribution, regular shape, high stability, and good biosafety. TM could bind specifically to VCAM-1 molecule expressed by tumor necrosis factor-alpha (TNF-α)-treated HUVECs. In the renal IRI-AKI model, the area under the curve (AUC) of TM significantly decreased both in the renal cortical and medullary after 2 h of reperfusion compared with the Sham group (p < 0.05). Normalized intensity difference (NID) of TM at different reperfusion time was all higher than that of blank microbubbles (BM) and the Sham group (p < 0.05). Ultrasound molecular imaging of TM could detect AKI early before commonly used renal function markers, histopathological biomarkers, and BM imaging. AUC of TM was negatively correlated with serum creatinine (Scr), blood urea nitrogen (BUN), and Cystatin C (Cys-C) levels, and NID of TM was linearly correlated with VCAM-1, TNF-α, and interleukin-6 (IL-6) expression (p < 0.05). Conclusions: Ultrasound molecular imaging based on TM carrying VCAM-1 polypeptide can accurately evaluate the changes in renal microcirculatory perfusion and inflammatory response, which might be a promising modality for early diagnosis of AKI.

Clinicopathological phenotype and outcomes of NCAM-1+ membranous lupus nephritis.

INTRODUCTION: No studies explored the long-term outcomes of neural cell adhesion molecule 1 (NCAM1) associated membranous lupus nephritis (MLN) patients. METHOD: We performed immunohistochemical studies on kidney biopsy specimens against NCAM1 in consecutive MLN patients. The clinical and histopathological characteristics and outcomes of cases of NCAM1 associated MLN patients are described and compared with NCAM1 negative patients. In addition, we detected serum circulating anti-NCAM1 antibodies through western blotting and indirect immunofluorescence assays. RESULTS: Among 361 MLN cases, 18 (5.0%) were glomerular NCAM1-positive. NCAM1 positive MLN patients were older [35 years (IQR 27-43) versus 28 (22-37); P = 0.050) and had lower systemic lupus erythematosus disease activity index [11 (IQR 8-12) versus 14 (10-18); P = 0.007], serum creatinine [60 µmol/L (IQR 50-70) versus 70 (54-114); P = 0.029], activity index [3 (IQR 2-6) versus 6 (3-9); P = 0.045] at kidney biopsy compared with NCAM1 negative patients. The percentage of positive anti-Sjogren's syndrome related antigen A antibodies in NCAM1 positive patients was significantly greater (83.3% versus 58.2%; P = 0.035) than in the NCAM1 negative patients. However, no evidence of neuropsychiatric disorders was found in these 18 patients. There were no significant differences in the treatment response and the risk of end stage renal diseases between NCAM1 positive and negative groups (P = 0.668 and P = 0.318, respectively). But the risk of death was much higher in the NCAM1 positive group than the NCAM1 negative group (27.8% vs. 8.1%, P = 0.007). Moreover, the risk of death was also much higher in the NCAM1 positive group than the matched NCAM1 negative group (Log-rank P = 0.013). Additionally, circulating anti-NCAM1 antibodies can be detected in 1/5 (20%) patients who had serum available. CONCLUSION: The prevalence of NCAM1 positivity was 5.0% in our cohort of MLN and the high mortality in these subgroup patients are needed to validate in future studies.

Impact of Composition and Autoclave Sterilization on the Mechanical and Biological Properties of ECM-Mimicking Cryogels.

Cryogels represent a valid strategy as scaffolds for tissue engineering. In order to adequately support adhesion and proliferation of anchorage-dependent cells, different polymers need to be combined within the same scaffold trying to mimic the complex features of a natural extracellular matrix (ECM). For this reason, in this work, gelatin (Gel) and chondroitin sulfate (CS), both functionalized with methacrylic groups to produce CSMA and GelMA derivatives, were selected to prepare cryogel networks. Both homopolymer and heteropolymer cryogels were produced, via radical crosslinking reactions carried out at -12 °C for 2 h. All the scaffolds were characterized for their mechanical, swelling and morphological properties, before and after autoclave sterilization. Moreover, they were evaluated for their biocompatibility and ability to support the adhesion of human gingival fibroblasts and tenocytes. GelMA-based homopolymer networks better withstood the autoclave sterilization process, compared to CSMA cryogels. Indeed, GelMA cryogels showed a decrease in stiffness of approximately 30%, whereas CSMA cryogels of approximately 80%. When GelMA and CSMA were blended in the same network, an intermediate outcome was observed. However, the hybrid scaffolds showed a general worsening of the biological performance. Indeed, despite their ability to withstand autoclave sterilization with limited modification of the mechanical and morphological properties, the hybrid cryogels exhibited poor cell adhesion and high LDH leakage. Therefore, not only do network components need to be properly selected, but also their combination and ability to withstand effective sterilization process should be carefully evaluated for the development of efficient scaffolds designed for tissue engineering purposes.

Quantum Dot-Based FRET Nanosensors for Talin-Membrane Assembly and Mechanosensing.

Understanding the mechanisms of assembly and disassembly of macromolecular structures in cells relies on solving biomolecular interactions. However, those interactions often remain unclear because tools to track molecular dynamics are not sufficiently resolved in time or space. In this study, we present a straightforward method for resolving inter- and intra-molecular interactions in cell adhesive machinery, using quantum dot (QD) based Förster resonance energy transfer (FRET) nanosensors. Using a mechanosensitive protein, talin, one of the major components of focal adhesions, we are investigating the mechanosensing ability of proteins to sense and respond to mechanical stimuli. First, we quantified the distances separating talin and a giant unilamellar vesicle membrane for three talin variants. These variants differ in molecular length. Second, we investigated the mechanosensing capabilities of talin, i.e., its conformational changes due to mechanical stretching initiated by cytoskeleton contraction. Our results suggest that in early focal adhesion, talin undergoes stretching, corresponding to a decrease in the talin-membrane distance of 2.5 nm. We demonstrate that QD-FRET nanosensors can be applied for the sensitive quantification of mechanosensing with a sub-nanometer accuracy.

Building Biomaterials to Mimic 3D Cell-Cell Junctions.

Cell-cell interactions typically occur in a 3D context that is distinct from conventional 2D cell-substrate interactions in a Petri dish. Here, we describe a benchtop method to combine a 2D extracellular matrix surface with a 3D, vertical boundary functionalized with the extracellular domain of E-cadherin. The methodology is suitable for any biology laboratory without requiring advanced microfabrication equipment or training. Overall, this cell-mimetic interface uniquely recapitulates key aspects of cell-cell adhesion and can serve as a versatile, reductionist technique to study general cell-cell interactions in a 3D context.