An introduction to proteoglycans and their localization

Selecting the Substantially Touched Vertebra as the Lowest Instrumented Vertebra in Spinal Surgeries for B3GALT6-Related Disorders: Clinical Experience and Literature Review

OBJECTIVES

B3GALT6-related disorders are characterized by severe early-onset spinal deformities requiring surgical corrections but are associated with increased risks of perioperative complications. This study reports the clinical experience and outcomes of selecting the substantially touched vertebra (STV) as the lowest instrumented vertebra (LIV) in spinal surgeries for patients with B3GALT6-related disorders, a group of extremely rare skeletal and connective tissue disorders.

METHODS

This retrospective study included patients who were molecularly diagnosed with B3GALT6-related disorders and received spinal surgeries for (kypho)scoliosis between 2017 and June 2023. Their medical records were reviewed. We also conducted a systematic literature review to identify (kypho)scoliosis management in patients with B3GALT6-related disorders.

RESULTS

We identified a total of four patients. Patient 1 presented with severe kyphoscoliosis and segmentation defects and received a pedicle subtraction osteotomy with short fusion and dual growing rods from T3 to L3. However, coronal imbalance was observed at the 18-month follow-up. Genetic testing revealed biallelic disease-causing variants in B3GALT6. A revision surgery was successfully performed, with the level of the LIV extended to the STV (L4). The LIV was similarly extended to the STV in the index surgery for subsequent Patients 2 and 3 who received preoperative genetic testing results, and no complication has been observed. Patient 4 underwent preoperative Halo-pelvic traction to minimize complications, followed by posterior spinal fusion. The curves were successfully reduced without complications. A systematic literature review identified 86 articles reporting (kypho) scoliosis management in 12 of the 63 patients with B3GALT6-related disorders. Limited surgical experience has been reported, with an increased rate of complications, including death.

CONCLUSIONS

Selecting the STV as the LIV is recommended in spinal surgeries for patients with B3GALT6-related disorders, considering the characteristic joint hypermobility associated with the condition. Additionally, preoperative Halo-pelvic traction may also be safe and effective. Furthermore, preoperative molecular diagnosis is essential for enabling precision medicine and minimizing complications.

Chondroitin sulfate: From bioactive molecule to versatile drug delivery system for advancing regenerative medicine

Regenerative medicine, a rapidly advancing field, holds immense promise for restoring and revitalizing damaged tissues and organs resulting from aging, diseases, or injuries, ultimately improving patient well-being. Chondroitin Sulfate (CS), a naturally occurring glycosaminoglycan, is a compelling biomaterial due to its natural origin, well-established biocompatibility, and structural complexity. Renowned for its biocompatibility, structural complexity, and varied bioactivities, CS provides significant applications beyond its recognized function in joint health and osteoarthritis treatment. Recent breakthroughs demonstrate its potential in treating complicated disorders such as interstitial cystitis, psoriasis, dry eye syndrome, and cardiovascular diseases by controlling inflammation, facilitating wound healing, and improving tissue repair. Notwithstanding its therapeutic potential, CS remains inadequately investigated in regenerative medicine and tissue engineering. Its capacity to modulate cellular signaling, promote extracellular matrix remodeling, and improve scaffold integration establishes it as a crucial facilitator of sophisticated therapeutic approaches. This review elucidates the progression of CS-based drug delivery systems, encompassing hydrogels, microparticles, nanoparticles, composites, and beads while underscoring their effectiveness in addressing conventional drug delivery obstacles such as non-specific targeting and off-target effects. Integrating CS into advanced platforms enables regulated drug release, accurate targeting, and enhanced cellular absorption while maintaining biodegradability and compatibility with tissue engineering scaffolds. Its inherent antioxidant, anti-inflammatory, and immune-modulating characteristics augment its attractiveness for individualized therapeutic applications. Recent studies highlight the adaptability of CS in developing multimodal drug delivery systems designed for regenerative medicine. Nonetheless, substantial deficiencies persist, especially in clinical validation and extensive applications. Overcoming these hurdles may fully realize CS's potential in transforming drug delivery, establishing a solid basis for the progression of regenerative therapies. By integrating biomaterial science with clinical medicine, CS-based systems are set to transform treatment approaches in regenerative medicine, providing precision, efficiency, and adaptability for individualized care.

Glycosaminoglycan Mass Spectrometry Imaging by Infrared Matrix-Assisted Laser Desorption Electrospray Ionization

Chondroitin sulfate (CS) is a type of glycosaminoglycan (GAG) that is abundant in cartilage and perineural networks (PNNs). Changes in the CS signature of PNNs have been implicated in several neurological diseases. Most CS-GAGs contain labile sulfate groups, which can be lost during ionization events that deposit large amounts of internal energy. Infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) is a soft ionization technique used for mass spectrometry imaging. In this work, we determine the spatial distribution of CS-GAG disaccharides within rodent brain using IR-MALDESI MSI. Non-, mono-, and disulfated disaccharides were detected with various adducts. All disaccharides colocalized to the PNNs, which are most abundant in the cortex and hippocampus regions of the brain. This is the first MSI study to spatially resolve CS-GAG disaccharides within brain, paving the way for IR-MALDESI to measure GAGs in neurological diseases.

Synthesis of Sulfated Carbohydrates - Glycosaminoglycans

Glycosaminoglycans (GAG) are polysaccharides that are ubiquitous on the surface of all mammalian cells, interacting with a multitude of proteins and orchestrating essential physiological and pathological processes. Among various GAG structures, heparan sulfate (HS) stands out for its intricate structure, positioning it as a significant cell-surface molecule capable of regulating wide range of cellular functions. Consequently, investigating the structure-activity relationships (SARs) with well-defined HS ligands emerges as an attractive avenue advancing drug discovery and biosensors. This chapter outlines a modular divergent strategy for synthesizing HS oligosaccharides to elucidate SARs. Here, we provide a literature overview on the synthesis of disaccharide building blocks, employing different orthogonal protecting groups, promoters, and optimization conditions to improve their suitability for subsequent oligosaccharide synthesis. Further, we highlight the synthesis of universal disaccharide building blocks derived from natural polysaccharides. We also provide insights of one-pot method and automated solid-phase synthesis of HS oligosaccharides. Finally, we review the status of SARs of popular heparan sulfate binding proteins (HSBPs).

Cerebellar infarction due to atlantoaxial subluxation in spondyloepimetaphyseal dysplasia-joint laxity type 1 case

INTRODUCTION

Spondyloepimetaphyseal dysplasia with joint laxity type 1 (SEMD-JL1) is an extremely rare skeletal dysplasia belonging to a group of disorders called linkeropathies. It is characterized by skeletal and connective tissue abnormalities. Biallelic variants in genes encoding enzymes that synthesize the tetrasaccharide linker region of glycosaminoglycans lead to linkeropathies, which exhibit clinical and phenotypic features that overlap with each other. SEMD-JL1 results in impaired growth and short stature, along with increased joint flexibility leading to limb joint dislocations and progressive spinal deformity.

METHODS AND RESULT

Whole exome sequencing was performed on the patient's genomic DNA. A novel variant in the B3GALT6 gene was detected as homozygous. During the patient's follow-up, signs of cerebellar infarction was observed due to atlantoaxial subluxation. Posterior circulation ischemic strokes have not been described with SEMD-JL1 and it was the second case in the skeletal dysplasia group to develop posterior circulation ischemic stroke due to atlantoaxial luxation.

CONCLUSION

Linkeropathies present with varying clinical manifestations and necessitate comprehensive genetic testing for accurate diagnosis of this complex patient group. Skeletal dysplasias, such as spondyloepimetaphyseal dysplasia, may be accompanied by atlantoaxial instability that can lead to serious spinal symptoms and even sudden death.

Proteoglycans Enhance the Therapeutic Effect of BMSC Transplantation on Osteoarthritis

BACKGROUND

The injection of bone mesenchymal stem cells (BMSCs) for osteoarthritis (OA) treatment fails to address the disrupted extracellular microenvironment, limiting the differentiation and paracrine functions of BMSCs and resulting in suboptimal therapeutic outcomes. Proteoglycans (PGs) promote cell differentiation, tissue repair, and microenvironment remodeling. This study investigated the potential of combining PGs with BMSCs to increase the efficacy of OA treatment.

METHODS

We evaluated the effects of PG on BMSC and chondrocyte functions by adding various PG concentrations to the culture media. Additionally, a Transwell system was used to assess the impact of PG on the communication between BMSCs and chondrocytes. The results of the in vitro experiment were verified by tissue staining and immunohistochemistry following the treatment of OA model rats.

RESULTS

Our findings indicate that PG effectively induces Col II expression in BMSCs and enhances the paracrine secretion of TGF-β1, thereby activating the TGF-β signaling pathway in chondrocytes and increasing PRG4 gene expression. Compared with the other groups, the BMSC/PG treatment group presented a smoother articular surface and more robust extracellular matrix than the other groups in vivo, with significantly increased expression and distribution of Smad2/3 and PRG4.

CONCLUSIONS

PG enhances BMSC differentiation into chondrocytes and stimulates paracrine TGF-β1 secretion. Proteoglycans not only promote chondrocyte differentiation and paracrine TGF-β1 signaling in BMSCs but also increase the sensitivity of chondrocytes to TGF-β1 secreted from BMSCs, leading to PRG4 expression through the TGFR/Smad2/3 pathway. Proteoglycans can enhance the therapeutic effect of BMSC treatment on OA and have the potential to delay the degeneration of OA cartilage.

Vascular Extracellular Matrix in Atherosclerosis

The extracellular matrix (ECM) plays a central role in the structural integrity and functionality of the cardiovascular system. Moreover, the ECM is involved in atherosclerotic plaque formation and stability. In fact, ECM remodeling affects plaque stability, cellular migration, and inflammatory responses. Collagens, fibronectin, laminin, elastin, and proteoglycans are crucial proteins during atherosclerosis development. This dynamic remodeling is driven by proteolytic enzymes such as matrix metalloproteinases (MMPs), cathepsins, and serine proteases. Exploring and investigating ECM dynamics is an important step to designing innovative therapeutic strategies targeting ECM remodeling mechanisms, thus offering significant advantages in the management of cardiovascular diseases. This review illustrates the structure and role of vascular ECM, presenting a new perspective on ECM remodeling and its potential as a therapeutic target in atherosclerosis treatments.

Extracellular Matrix Components and Mechanosensing Pathways in Health and Disease

Glycosaminoglycans (GAGs) and proteoglycans (PGs) are essential components of the extracellular matrix (ECM) with pivotal roles in cellular mechanosensing pathways. GAGs, such as heparan sulfate (HS) and chondroitin sulfate (CS), interact with various cell surface receptors, including integrins and receptor tyrosine kinases, to modulate cellular responses to mechanical stimuli. PGs, comprising a core protein with covalently attached GAG chains, serve as dynamic regulators of tissue mechanics and cell behavior, thereby playing a crucial role in maintaining tissue homeostasis. Dysregulation of GAG/PG-mediated mechanosensing pathways is implicated in numerous pathological conditions, including cancer and inflammation. Understanding the intricate mechanisms by which GAGs and PGs modulate cellular responses to mechanical forces holds promise for developing novel therapeutic strategies targeting mechanotransduction pathways in disease. This comprehensive overview underscores the importance of GAGs and PGs as key mediators of mechanosensing in maintaining tissue homeostasis and their potential as therapeutic targets for mitigating mechano-driven pathologies, focusing on cancer and inflammation.

Lentiviral vector determinants of anion-exchange chromatography elution heterogeneity

The demand for Lentiviral Vector (LV) drug substance is increasing. However, primary capture using convective anion-exchange chromatography remains a significant manufacturing challenge. This stems from a poor understanding of the complex adsorption behaviors linked to LVs intricate and variable structure, such as high binding heterogeneity which is typically characterized by a gradient elution profile consisting of two peaks. Understanding which LV structural components drive these phenomena is therefore crucial for rational process design. This work identifies the key LV envelope components responsible for binding to quaternary-amine membrane adsorbents. Eliminating the pseudotype protein (Vesicular Stomatitis Virus G glycoprotein [VSV-G]) did not impact the heterogenous two-peak elution profile, suggesting it is not a major binding species. Digestion of envelope glycosaminoglycans (GAGs), present on proteoglycans, leads to a dramatic reduction in the proportion of vector eluted in peak 2, decreasing from 50% to 3.1%, and a threefold increase in peak 1 maximum. Data from reinjection experiments point towards interparticle envelope heterogeneity from discrete LV populations, where the two-peak profile emerges from a subpopulation of LVs interacting via highly charged GAGs (peak 2) along with a weaker binding population likely interacting through the phospholipid membrane and envelope protein (peak 1).

Nerve-Glial antigen 2: unmasking the enigmatic cellular identity in the central nervous system

Chondroitin sulfate proteoglycans (CSPGs) are fundamental components of the extracellular matrix in the central nervous system (CNS). Among these, the Nerve-Glial antigen 2 (NG2) stands out as a transmembrane CSPG exclusively expressed in a different population of cells collectively termed NG2-expressing cells. These enigmatic cells, found throughout the developing and adult CNS, have been indicated with various names, including NG2 progenitor cells, polydendrocytes, synantocytes, NG2 cells, and NG2-Glia, but are more commonly referred to as oligodendrocyte progenitor cells. Characterized by high proliferation rates and unique morphology, NG2-expressing cells stand apart from neurons, astrocytes, and oligodendrocytes. Intriguingly, some NG2-expressing cells form functional glutamatergic synapses with neurons, challenging the long-held belief that only neurons possess the intricate machinery required for neurotransmission. In the CNS, the complexity surrounding NG2-expressing cells extends to their classification. Additionally, NG2 expression has been documented in pericytes and immune cells, suggesting a role in regulating brain innate immunity and neuro-immune crosstalk in homeostasis. Ongoing debates revolve around their heterogeneity, potential as progenitors for various cell types, responses to neuroinflammation, and the role of NG2. Therefore, this review aims to shed light on the enigma of NG2-expressing cells by delving into their structure, functions, and signaling pathways. We will critically evaluate the literature on NG2 expression across the CNS, and address the contentious issues surrounding their classification and roles in neuroinflammation and neurodegeneration. By unraveling the intricacies of NG2-expressing cells, we hope to pave the way for a more comprehensive understanding of their contributions to CNS health and during neurological disorders.

Unraveling neurovascular mysteries: the role of endothelial glycocalyx dysfunction in Alzheimer's disease pathogenesis

While cardiovascular disease, cancer, and human immunodeficiency virus (HIV) mortality rates have decreased over the past 20 years, Alzheimer's Disease (AD) deaths have risen by 145% since 2010. Despite significant research efforts, effective AD treatments remain elusive due to a poorly defined etiology and difficulty in targeting events that occur too downstream of disease onset. In hopes of elucidating alternative treatment pathways, now, AD is commonly being more broadly defined not only as a neurological disorder but also as a progression of a variety of cerebrovascular pathologies highlighted by the breakdown of the blood-brain barrier. The endothelial glycocalyx (GCX), which is an essential regulator of vascular physiology, plays a crucial role in the function of the neurovascular system, acting as an essential vascular mechanotransducer to facilitate ultimate blood-brain homeostasis. Shedding of the cerebrovascular GCX could be an early indication of neurovascular dysfunction and may subsequently progress neurodegenerative diseases like AD. Recent advances in in vitro modeling, gene/protein silencing, and imaging techniques offer new avenues of scrutinizing the GCX's effects on AD-related neurovascular pathology. Initial studies indicate GCX degradation in AD and other neurodegenerative diseases and have begun to demonstrate a possible link to GCX loss and cerebrovascular dysfunction. This review will scrutinize the GCX's contribution to known vascular etiologies of AD and propose future work aimed at continuing to uncover the relationship between GCX dysfunction and eventual AD-associated neurological deterioration.

Targeting Macrophage Polarization for Reinstating Homeostasis following Tissue Damage

Tissue regeneration and remodeling involve many complex stages. Macrophages are critical in maintaining micro-environmental homeostasis by regulating inflammation and orchestrating wound healing. They display high plasticity in response to various stimuli, showing a spectrum of functional phenotypes that vary from M1 (pro-inflammatory) to M2 (anti-inflammatory) macrophages. While transient inflammation is an essential trigger for tissue healing following an injury, sustained inflammation (e.g., in foreign body response to implants, diabetes or inflammatory diseases) can hinder tissue healing and cause tissue damage. Modulating macrophage polarization has emerged as an effective strategy for enhancing immune-mediated tissue regeneration and promoting better integration of implantable materials in the host. This article provides an overview of macrophages' functional properties followed by discussing different strategies for modulating macrophage polarization. Advances in the use of synthetic and natural biomaterials to fabricate immune-modulatory materials are highlighted. This reveals that the development and clinical application of more effective immunomodulatory systems targeting macrophage polarization under pathological conditions will be driven by a detailed understanding of the factors that regulate macrophage polarization and biological function in order to optimize existing methods and generate novel strategies to control cell phenotype.

Perception and response of skeleton to mechanical stress

Mechanical stress stands as a fundamental factor in the intricate processes governing the growth, development, morphological shaping, and maintenance of skeletal mass. The profound influence of stress in shaping the skeletal framework prompts the assertion that stress essentially births the skeleton. Despite this acknowledgment, the mechanisms by which the skeleton perceives and responds to mechanical stress remain enigmatic. In this comprehensive review, our scrutiny focuses on the structural composition and characteristics of sclerotin, leading us to posit that it serves as the primary structure within the skeleton responsible for bearing and perceiving mechanical stress. Furthermore, we propose that osteocytes within the sclerotin emerge as the principal mechanical-sensitive cells, finely attuned to perceive mechanical stress. And a detailed analysis was conducted on the possible transmission pathways of mechanical stress from the extracellular matrix to the nucleus.

Methyl α-D-galactopyranosyl-(1→3)-β-D-galactopyranoside and methyl β-D-galactopyranosyl-(1→3)-β-D-galactopyranoside: Glycosidic linkage conformation determined from MA'AT analysis

MA'AT analysis has been applied to two biologically-important O-glycosidic linkages in two disaccharides, α-D-Galp-(1→3)-β-D-GalpOMe (3) and β-D-Galp-(1→3)-β-D-GalpOMe (4). Using density functional theory (DFT) to obtain parameterized equations relating a group of trans-O-glycosidic NMR spin-couplings to either phi (ϕ') or psi (ψ'), and experimental 3JCOCH, 2JCOC, and 3JCOCC spin-couplings measured in aqueous solution in 13C-labeled isotopomers, probability distributions of ϕ' and ψ' in each linkage were determined and compared to those determined by aqueous 1-μs molecular dynamics (MD) simulation. Good agreement was found between the MA'AT and single-state MD conformational models of these linkages for the most part, with modest (approximately <15°) differences in the mean values of ϕ' and ψ', although the envelope of allowed angles (encoded in circular standard deviations or CSDs) is consistently larger for ϕ' determined from MA'AT analysis than from MD for both linkages. The MA'AT model of the α-Galp-(1→3)-β-Galp linkage agrees well with those determined previously using conventional NMR methods (3JCOCH values and/or 1H-1H NOEs), but some discrepancy was observed for the β-Galp-(1→3)-β-Galp linkage, which may arise from errors in the conventions used to describe the linkage torsion angles. Statistical analyses of X-ray crystal structures show ranges of ϕ' and ψ' for both linkages that include the mean angles determined from MA'AT analyses, although both angles adopt a wide range of values in the crystalline state, with ϕ' in β-Galp-(1→3)-β-Galp linkages showing greater-than-expected conformational variability.

Degradation of specific glycosaminoglycans improves transfection efficiency and vector production in transient lentiviral vector manufacturing processes

Both cell surface and soluble extracellular glycosaminoglycans have been shown to interfere with the exogenous nucleic acid delivery efficiency of non-viral gene delivery, including lipoplex and polyplex-mediated transfection. Most gene therapy viral vectors used commercially and in clinical trials are currently manufactured using transient transfection-based bioprocesses. The growing demand for viral vector products, coupled with a global shortage in production capability, requires improved transfection technologies and processes to maximise process efficiency and productivity. Soluble extracellular glycosaminoglycans were found to accumulate in the conditioned cell culture medium of suspension adapted HEK293T cell cultures, compromising transfection performance and lentiviral vector production. The enzymatic degradation of specific, chondroitin sulphate-based, glycosaminoglycans with chondroitinase ABC was found to significantly enhance transfection performance. Additionally, we report significant improvements in functional lentiviral vector titre when cultivating cells at higher cell densities than those utilised in a control lentiviral vector bioprocess; an improvement that was further enhanced when cultures were supplemented with chondroitinase ABC prior to transfection. A 71.2% increase in functional lentiviral vector titre was calculated when doubling the cell density prior to transfection compared to the existing process and treatment of the high-density cell cultures with 0.1 U/mL chondroitinase ABC resulted in a further 18.6% increase in titre, presenting a method that can effectively enhance transfection performance.

Comparison of Polypentenamer and Polynorbornene Bottlebrushes in Dilute Solution

Bottlebrush (BB) polymers were synthesized via grafting-from-atom transfer radical polymerization (ATRP) of styrene on polypentenamer and polynorbornene macroinitiators with matched grafting density (n g = 4) and backbone degrees of polymerization (122 ≥ N bb ≥ 61) to produce a comparative study on their respective dilute solution properties as a function of increasing side chain degree of polymerization (116 ≥ N sc ≥ 5). The grafting-from technique produced near quantitative grafting efficiency and narrow dispersity N sc as evidenced by spectroscopic analysis and ring closing metathesis depolymerization of the polypentenamer BBs. The versatility of this synthetic approach permitted a comprehensive survey of power law expressions that arise from monitoring intrinsic viscosity, hydrodynamic radius, and radius of gyration as a function of increasing the molar mass of the BBs by increasing N sc. These values were compared to a series of linear (nongrafted, N sc = 0) macroinitiators in addition to linear grafts. This unique study allowed elucidation of the onset of bottlebrush behavior for two different types of bottlebrush backbones with identical grafting density but inherently different flexibility. In addition, grafting-from ATRP of methyl acrylate on a polypentenamer macroinitiator allowed the observation of the effects of graft chemistry in comparison to polystyrene. Differences in the observed scaling relationships in dilute solution as a function of each of these synthetic variants are discussed.

Future proofing of chondroitin sulphate production: Importance of sustainability and quality for the end-applications

Chondroitin sulphates (CSs) are the most well-known glycosaminoglycans (GAGs) found in any living organism, from microorganisms to invertebrates and vertebrates (including humans), and provide several health benefits. The applications of CSs are numerous including tissue engineering, osteoarthritis treatment, antiviral, cosmetics, and skincare applications. The current commercial production of CSs mostly uses animal, bovine, porcine, and avian tissues as well as marine organisms, marine mammals, sharks, and other fish. The production process consists of tissue hydrolysis, protein removal, and purification using various methods. Mostly, these are chemical-dependent and are complex, multi-step processes. There is a developing trend for abandonment of harsh extraction chemicals and their substitution with different green-extraction technologies, however, these are still in their infancy. The quality of CSs is the first and foremost requirement for end-applications and is dependent on the extraction and purification methodologies used. The final products will show different bio-functional properties, depending on their origin and production methodology. This is a comprehensive review of the characteristics, properties, uses, sources, and extraction methods of CSs. This review emphasises the need for extraction and purification processes to be environmentally friendly and gentle, followed by product analysis and quality control to ensure the expected bioactivity of CSs.

The Tumor Stroma of Squamous Cell Carcinoma: A Complex Environment That Fuels Cancer Progression

The tumor microenvironment (TME), a complex assembly of cellular and extracellular matrix (ECM) components, plays a crucial role in driving tumor progression, shaping treatment responses, and influencing metastasis. This narrative review focuses on the cutaneous squamous cell carcinoma (cSCC) tumor stroma, highlighting its key constituents and their dynamic contributions. We examine how significant changes within the cSCC ECM-specifically, alterations in fibronectin, hyaluronic acid, laminins, proteoglycans, and collagens-promote cancer progression, metastasis, and drug resistance. The cellular composition of the cSCC TME is also explored, detailing the intricate interplay of cancer-associated fibroblasts (CAFs), mesenchymal stem cells (MSCs), endothelial cells, pericytes, adipocytes, and various immune cell populations. These diverse players modulate tumor development, angiogenesis, and immune responses. Finally, we emphasize the TME's potential as a therapeutic target. Emerging strategies discussed in this review include harnessing the immune system (adoptive cell transfer, checkpoint blockade), hindering tumor angiogenesis, disrupting CAF activity, and manipulating ECM components. These approaches underscore the vital role that deciphering TME interactions plays in advancing cSCC therapy. Further research illuminating these complex relationships will uncover new avenues for developing more effective treatments for cSCC.

Proteoglycans in Mechanobiology of Tissues and Organs: Normal Functions and Mechanopathology

Proteoglycans (PGs) are a diverse class of glycoconjugates that serve critical functions in normal mechanobiology and mechanopathology. Both the protein cores and attached glycosaminoglycan (GAG) chains function in mechanically-sensitive processes, and loss of either can contribute to development of pathological conditions. PGs function as key components of the extracellular matrix (ECM) where they can serve as mechanosensors in mechanosensitive tissues including bone, cartilage, tendon, blood vessels and soft organs. The mechanical properties of these tissues depend on the presence and function of PGs, which play important roles in tissue elasticity, osmolarity and pressure sensing, and response to physical activity. Tissue responses depend on cell surface mechanoreceptors that include integrins, CD44, voltage sensitive ion channels, transient receptor potential (TRP) and piezo channels. PGs contribute to cell and molecular interplay in wound healing, fibrosis, and cancer, where they transduce the mechanical properties of the ECM and influence the progression of various context-specific conditions and diseases. The PGs that are most important in mechanobiology vary depending on the tissue and its functions and functional needs. Perlecan, for example, is important in the mechanobiology of basement membranes, cardiac and skeletal muscle, while aggrecan plays a primary role in the mechanical properties of cartilage and joints. A variety of techniques have been used to study the mechanobiology of PGs, including atomic force microscopy, mouse knockout models, and in vitro cell culture experiments with 3D organoid models. These studies have helped to elucidate the tissue-specific roles that PGs play in cell-level mechanosensing and tissue mechanics. Overall, the study of PGs in mechanobiology is yielding fundamental new concepts in the molecular basis of mechanosensing that can open the door to the development of new treatments for a host of conditions related to mechanopathology.

Glycosaminoglycan modifications of betaglycan regulate ectodomain shedding to fine-tune TGF-β signaling responses in ovarian cancer

In pathologies including cancer, aberrant Transforming Growth Factor-β (TGF-β) signaling exerts profound tumor intrinsic and extrinsic consequences. Intense clinical endeavors are underway to target this pathway. Central to the success of these interventions is pinpointing factors that decisively modulate the TGF-β responses. Betaglycan/type III TGF-β receptor (TβRIII), is an established co-receptor for the TGF-β superfamily known to bind directly to TGF-βs 1-3 and inhibin A/B. Betaglycan can be membrane-bound and also undergo ectodomain cleavage to produce soluble-betaglycan that can sequester its ligands. Its extracellular domain undergoes heparan sulfate and chondroitin sulfate glycosaminoglycan modifications, transforming betaglycan into a proteoglycan. We report the unexpected discovery that the heparan sulfate glycosaminoglycan chains on betaglycan are critical for the ectodomain shedding. In the absence of such glycosaminoglycan chains betaglycan is not shed, a feature indispensable for the ability of betaglycan to suppress TGF-β signaling and the cells' responses to exogenous TGF-β ligands. Using unbiased transcriptomics, we identified TIMP3 as a key inhibitor of betaglycan shedding thereby influencing TGF-β signaling. Our results bear significant clinical relevance as modified betaglycan is present in the ascites of patients with ovarian cancer and can serve as a marker for predicting patient outcomes and TGF-β signaling responses. These studies are the first to demonstrate a unique reliance on the glycosaminoglycan chains of betaglycan for shedding and influence on TGF-β signaling responses. Dysregulated shedding of TGF-β receptors plays a vital role in determining the response and availability of TGF-βs', which is crucial for prognostic predictions and understanding of TGF-β signaling dynamics.

Phenotypic and genetic characteristics of 24 cases of early infantile epileptic encephalopathy in East China, including a rare case of biallelic UGDH mutations

BACKGROUND

Early infantile epileptic encephalopathy (EIEE) is a group of highly heterogeneous diseases, both phenotypically and genetically. Usually, it starts early on and manifests as intractable epilepsy, abnormal electroencephalogram, and growth retardation/intellectual impairment. With the advent of next-generation sequencing (NGS), its genetic etiology has attracted increasing clinical attention. This study aimed to investigate the genetic characteristics and clinical phenotypes of patients with EIEE from a central hospital in Eastern China.

METHODS

This study retrospectively included the gene variants from 24 EIEE-positive patients admitted between January 2021 and January 2022 to a hospital in Anhui Province, China. The genetic diagnosis was performed in all cases by trio-based whole-exome sequencing (WES). Additionally, Video electroencephalogram (VEEG) and neuroimaging examinations were performed.

RESULTS

A total of 24 children were included. The average age at the first seizure was approximately 5 months. About 42% of children had developmental retardation of varying degrees, 43% had brain structural abnormalities, and 64% had VEEG abnormalities. In addition, other phenotypes, including endocrine metabolism and cardiac structural abnormalities, have been independently reported. In total, fifteen pathogenic gene variants were identified in 24 patients. The main pathogenic genes identified were SCN1A (25%, 6/24), KCNQ2 (8.3%, 2/24), and TBC1D24 (8.3%, 2/24). We also found an extremely rare case of EIEE84 type caused by biallelic UGDH gene variants, predicting that this variant might affect the stability of the protein structure.

CONCLUSIONS

SCN1A pathogenic variants are the main factor leading to EIEE, similar to previously published cohort reports. NGS is useful for accurate clinical diagnoses and precise treatment choices. We also reported a rare case of EIEE84 caused by variants in the UGDH gene in a Chinese patient. This study further enriches the known spectrum of pathogenic EIEE genes.

Alkali-treated titanium dioxide promotes formation of proteoglycan layer and altered calcification and immunotolerance capacity in bone marrow stem cell

Introduction

In this study, we report that a proteoglycans (PGs)-layer between the bone and titanium dioxide (TiO2) surface after osseointegration improved the calcification capacity and immunotolerance of human bone marrow mesenchymal stem cells (hBMSCs) on TiO2. Alkaline treatment of TiO2 is a method for promoting osteogenesis in hBMSCs. We hypothesized that promotion of osteogenesis due to alkaline treatment was caused by changing PGs-layer on TiO2.

Objective

This study aimed to analyze whether alkaline treatment of TiO2 affects PGs-layer formation and immunotolerance in hBMSCs.

Methods

The topology and wettability of the alkaline-treated titanium (Ti-Al) and unprocessed titanium (Ti-MS) surfaces were characterized. Initial cell attachment, cell proliferation, calcification capacity, alkaline phosphatase activity, PGs-layer formation, PGs function, and the expression of osteogenic and immunotolerance-related genes were analyzed. The conditioned medium (CM) from hBMSCs grown on Ti-Al and Ti-MS was added to macrophages (hMps) and Jurkat cells, and immunotolerance gene expression in these cells was analyzed.

Results

hBMSCs cultured on Ti-Al showed increased initial cell attachment, cell proliferation, PG-layer formation, and osteogenic capacity compared with hBMSCs on Ti-MS. Gene expression of indoleamine 2,3-dioxygenase (IDO) in the hBMSCs cultured on Ti-Al was higher than that in the hBMSCs on Ti-MS. CM from hBMSCs did not affect markers of M1 and M2 macrophages in hMps. CM from hBMSCs cultured on Ti-Al altered the gene expression of Foxp3 in Jurkat cells compared to that of CM from hBMSCs on Ti-MS.

Significance

These results suggest that alkaline treatment of TiO2 altered PGs-layer formation, and changed the osteogenesis and immunotolerance of hBMSCs.

Heparan sulfate modifications of betaglycan promote TIMP3-dependent ectodomain shedding to fine-tune TGF-β signaling

In pathologies such as cancer, aberrant Transforming Growth Factor-β (TGF-β) signaling exerts profound tumor intrinsic and extrinsic consequences. Intense clinical endeavors are underway to target this pivotal pathway. Central to the success of these interventions is pinpointing factors that decisively modulate the TGF-β responses. Betaglycan/type III TGF-β receptor (TβRIII), is an established co-receptor for the TGF-β superfamily known to bind directly to TGF-βs 1-3 and inhibin A/B. While betaglycan can be membrane-bound, it can also undergo ectodomain cleavage to produce soluble-betaglycan that can sequester its ligands. The extracellular domain of betaglycan undergoes heparan sulfate and chondroitin sulfate glycosaminoglycan modifications, transforming betaglycan into a proteoglycan. Here we report the unexpected discovery that the heparan sulfate modifications are critical for the ectodomain shedding of betaglycan. In the absence of such modifications, betaglycan is not shed. Such shedding is indispensable for the ability of betaglycan to suppress TGF-β signaling and the cells' responses to exogenous TGF-β ligands. Using unbiased transcriptomics, we identified TIMP3 as a key regulator of betaglycan shedding and thereby TGF-β signaling. Our results bear significant clinical relevance as modified betaglycan is present in the ascites of patients with ovarian cancer and can serve as a marker for predicting patient outcomes and TGF-β signaling responses. These studies are the first to demonstrate a unique reliance on the glycosaminoglycan modifications of betaglycan for shedding and influence on TGF-β signaling responses. Dysregulated shedding of TGF-β receptors plays a vital role in determining the response and availability of TGF-βs', which is crucial for prognostic predictions and understanding of TGF-β signaling dynamics.

Proteoglycans in Articular Cartilage and Their Contribution to Chondral Injury and Repair Mechanisms

Proteoglycans are vital components of the extracellular matrix in articular cartilage, providing biomechanical properties crucial for its proper functioning. They are key players in chondral diseases, specifically in the degradation of the extracellular matrix. Evaluating proteoglycan molecules can serve as a biomarker for joint degradation in osteoarthritis patients, as well as assessing the quality of repaired tissue following different treatment strategies for chondral injuries. Despite ongoing research, understanding osteoarthritis and cartilage repair remains unclear, making the identification of key molecules essential for early diagnosis and effective treatment. This review offers an overview of proteoglycans as primary molecules in articular cartilage. It describes the various types of proteoglycans present in both healthy and damaged cartilage, highlighting their roles. Additionally, the review emphasizes the importance of assessing proteoglycans to evaluate the quality of repaired articular tissue. It concludes by providing a visual and narrative description of aggrecan distribution and presence in healthy cartilage. Proteoglycans, such as aggrecan, biglycan, decorin, perlecan, and versican, significantly contribute to maintaining the health of articular cartilage and the cartilage repair process. Therefore, studying these proteoglycans is vital for early diagnosis, evaluating the quality of repaired cartilage, and assessing treatment effectiveness.

Does Vitamin K2 Influence the Interplay between Diabetes Mellitus and Intervertebral Disc Degeneration in a Rat Model?

Intervertebral disc (IVD) degeneration is a common cause of low back pain in diabetes mellitus type 2 (T2DM) patients. Its pathogenesis and the vitamin (vit.) K2 influence on this disease remain unclear. Lumbar motion segments of male Zucker Diabetes Fatty (ZDF) rats (non-diabetic [control] and diabetic; fed without or with vit. K2) were used. Femur lengths and vertebral epiphyseal cross-section areas were measured. IVDs were histopathologically examined. Protein synthesis and gene expression of isolated IVD fibrochondrocytes were analyzed. T2DM rats showed histopathological IVD degeneration. Femur lengths and epiphyseal areas were smaller in T2DM rats regardless of vit. K2 feeding. Fibrochondrocytes synthesized interleukin (IL)-24 and IL-10 with no major differences between groups. Alpha smooth muscle actin (αSMA) was strongly expressed, especially in cells of vit. K2-treated animals. Gene expression of aggrecan was low, and that of collagen type 2 was high in IVD cells of diabetic animals, whether treated with vit. K2 or not. Suppressor of cytokine signaling (Socs)3 and heme oxygenase (Hmox)1 gene expression was highest in the cells of diabetic animals treated with vit. K2. Vit. K2 influenced the expression of some stress-associated markers in IVD cells of diabetic rats, but not that of IL-10 and IL-24.

Gellan gum-based hydrogels support the recreation of the dermal papilla microenvironment

The dermal papilla (DP), a specialized compartment within the hair follicle, regulates hair growth. However, human DP cells rapidly lose their inductivity in 2D-culture given the loss of positional and microenvironmental cues. Spheroids have been capable of recreating the 3D intercellular organization of DP cells, however, DP cell-matrix interactions are poorly represented. Considering the specific nature of the DP's extracellular matrix (ECM), we functionalized gellan gum (GG) with collagen IV-(HepIII) or fibronectin-(cRGDfC) derived peptide sequences to generate a 3D environment in which the phenotype and physiological functions of DP cells are restored. We further tuned the stiffness of the microenvironments by varying GG amount. Biomimetic peptides in stiffer hydrogels promoted the adhesion of DP cells, while each peptide and amount of polymer independently influenced the type and quantity of ECM proteins deposited. Furthermore, although peptides did not seem to have an influence, stiffer hydrogels improved the inductive capacity of DP cells after short term culture. Interestingly, independently of the peptide, these hydrogels supported the recapitulation of basic hair morphogenesis-like events when incorporated in an organotypic human skin in vitro model. Our work demonstrates that tailored GG hydrogels support the generation of a microenvironment in which both cell-ECM and cell-cell interactions positively influence DP cells towards the creation of an artificial DP.

Compositional Analysis of Glycosaminoglycans in Different Lung Cancer Types-A Pilot Study

Lung cancer is one of the most commonly diagnosed cancer types. Studying the molecular changes that occur in lung cancer is important to understand tumor formation and identify new therapeutic targets and early markers of the disease to decrease mortality. Glycosaminoglycan chains play important roles in various signaling events in the tumor microenvironment. Therefore, we have determined the quantity and sulfation characteristics of chondroitin sulfate and heparan sulfate in formalin-fixed paraffin-embedded human lung tissue samples belonging to different lung cancer types as well as tumor adjacent normal areas. Glycosaminoglycan disaccharide analysis was performed using HPLC-MS following on-surface lyase digestion. Significant changes were identified predominantly in the case of chondroitin sulfate; for example, the total amount was higher in tumor tissue compared to the adjacent normal tissue. We also observed differences in the degree of sulfation and relative proportions of individual chondroitin sulfate disaccharides between lung cancer types and adjacent normal tissue. Furthermore, the differences in the 6-O-/4-O-sulfation ratio of chondroitin sulfate were different between the lung cancer types. Our pilot study revealed that further investigation of the role of chondroitin sulfate chains and enzymes involved in their biosynthesis is an important aspect of lung cancer research.

Obesity Is Associated with Distorted Proteoglycan Expression in Adipose Tissue

Proteoglycans are central components of the extracellular matrix (ECM) and binding partners for inflammatory chemokines. Morphological differences in the ECM and increased inflammation are prominent features of the white adipose tissues in patients with obesity. The impact of obesity and weight loss on the expression of specific proteoglycans in adipose tissue is not well known. This study aimed to investigate the relationship between adiposity and proteoglycan expression. We analyzed transcriptomic data from two human bariatric surgery cohorts. In addition, RT-qPCR was performed on adipose tissues from female and male mice fed a high-fat diet. Both visceral and subcutaneous adipose tissue depots were analyzed. Adipose mRNA expression of specific proteoglycans, proteoglycan biosynthetic enzymes, proteoglycan partner molecules, and other ECM-related proteins were altered in both human cohorts. We consistently observed more profound alterations in gene expression of ECM targets in the visceral adipose tissues after surgery (among others VCAN (p = 0.000309), OGN (p = 0.000976), GPC4 (p = 0.00525), COL1A1 (p = 0.00221)). Further, gene analyses in mice revealed sex differences in these two tissue compartments in obese mice. We suggest that adipose tissue repair is still in progress long after surgery, which may reflect challenges in remodeling increased adipose tissues. This study can provide the basis for more mechanistic studies on the role of proteoglycans in adipose tissues in obesity.

Gua Lou Er Chen decoction attenuates atherosclerosis by reducing proteoglycans accumulation and inflammation

BACKGROUND

Proteoglycans (PGs) accumulation and inflammation are two interactional pathological processes of atherosclerosis (AS). Up to now, there is no ideal drug for decreasing these pathological changes. Gua Lou Er Chen decoction (GED) has been used to treat AS for several years. However, if GED could treat AS through reducing PGs accumulation and inflammation remains unknown.

PURPOSE

This study was designed to illustrate whether GED could attenuate AS by reducing chondroitin sulphate proteoglycan (CSPG) expressions and alleviating inflammation.

METHODS

In vivo study, apolipoprotein E-deficient mice were fed a high-fat diet to induce AS. In vitro study, oxidised low-density lipoprotein (ox-LDL) and tumour necrosis factor (TNF)-α were used to induce proteoglycans accumulation and inflammation changes of vascular smooth muscle cells (VSMCs) and RAW264.7 macrophages. Oil Red O was used to stain mouse aortic lipid plaque. Haematoxylin eosin staining was used to assess the pathological changes of aortic valve and thoracic aorta. Specialised kits were used to identify blood lipids and sGAGs. Immunofluorescence and immunohistochemistry was used to identify aortic valve CSPG and versican. Western blotting, enzyme-linked immunosorbent assay and quantitative reverse transcription-polymerase chain reaction were used to measure versican, interleukin (IL)-6, TNF-α, and chondroitin sulphate (CS) synthetase expressions. CCK-8 was used to measure the cells proliferation.

RESULTS

In vivo experiments revealed that GED significantly improved hyperlipidemia, lowered lipid plaque deposition in the aorta, and increased plaque stability of AS mice. In addition, further studies revealed that GED lowered the sGAGs, CSPG, and versican levels and down-regulated CS synthetase and inflammatory factor expressions. In vitro experiments revealed that GED decreased TNF-α expression in the RAW264.7 macrophage supernatant stimulated by ox-LDL; decreased versican, CS-related synthetase, and IL-6 expressions; reduced VSMC proliferation stimulated by ox-LDL; down-regulated sGAG and versican expressions of VSMCs stimulated by TNF-α.

CONCLUSION

Our results demonstrated that GED could attenuate AS by reducing hyperlipidemia, hyper-expression of CSPG, and inflammation. This study might provide a novel insight into the development of innovative drug for AS.

A sulphated glycosaminoglycan extract from Placopecten magellanicus inhibits the Alzheimer's disease β-site amyloid precursor protein cleaving enzyme 1 (BACE-1)

The clinically important anticoagulant heparin, a member of the glycosaminoglycan family of carbohydrates that is extracted predominantly from porcine and bovine tissue sources, has previously been shown to inhibit the β-site amyloid precursor protein cleaving enzyme 1 (BACE-1), a key drug target in Alzheimer's Disease. In addition, heparin has been shown to exert favourable bioactivities through a number of pathophysiological pathways involved in the disease processes of Alzheimer's Disease including inflammation, oxidative stress, tau phosphorylation and amyloid peptide generation. Despite the multi-target potential of heparin as a therapeutic option for Alzheimer's disease, the repurposing of this medically important biomolecule has to-date been precluded by its high anticoagulant potential. An alternative source to mammalian-derived glycosaminoglycans are those extracted from marine environments and these have been shown to display an expanded repertoire of sequence-space and heterogeneity compared to their mammalian counterparts. Furthermore, many marine-derived glycosaminoglycans appear to retain favourable bioactivities, whilst lacking the high anticoagulant potential of their mammalian counterparts. Here we describe a sulphated, marine-derived glycosaminoglycan extract from the Atlantic Sea Scallop, Placopecten magellanicus that displays high inhibitory potential against BACE-1 (IC₅₀ = 4.8 μg.mL^-1) combined with low anticoagulant activity; 25-fold less than that of heparin. This extract possesses a more favourable therapeutic profile compared to pharmaceutical heparin of mammalian provenance and is composed of a mixture of heparan sulphate (HS), with a high content of 6-sulphated N-acetyl glucosamine (64%), and chondroitin sulphate.

Heparan sulfate proteoglycans (HSPGs) of the ocular lens

Heparan sulfate proteoglycans (HSPGs) reside in most cells; on their surface, in the pericellular milieu and/or extracellular matrix. In the eye, HSPGs can orchestrate the activity of key signalling molecules found in the ocular environment that promote its development and homeostasis. To date, our understanding of the specific roles played by individual HSPG family members, and the heterogeneity of their associated sulfated HS chains, is in its infancy. The crystalline lens is a relatively simple and well characterised ocular tissue that provides an ideal stage to showcase and model the expression and unique roles of individual HSPGs. Individual HSPG core proteins are differentially localised to eye tissues in a temporal and spatial developmental- and cell-type specific manner, and their loss or functional disruption results in unique phenotypic outcomes for the lens, and other ocular tissues. More recent work has found that different HS sulfation enzymes are also presented in a cell- and tissue-specific manner, and that disruption of these different sulfation patterns affects specific HS-protein interactions. Not surprisingly, these sulfated HS chains have also been reported to be required for lens and eye development, with dysregulation of HS chain structure and function leading to pathogenesis and eye-related phenotypes. In the lens, HSPGs undergo significant and specific changes in expression and function that can drive pathology, or in some cases, promote tissue repair. As master signalling regulators, HSPGs may one day serve as valuable biomarkers, and even as putative targets for the development of novel therapeutics, not only for the eye but for many other systemic pathologies.

Human Xylosyltransferase I-An Important Linker between Acute Senescence and Fibrogenesis

The human xylosyltransferase isoform XT-I catalyzes the initial step in proteoglycan biosynthesis and represents a biomarker of myofibroblast differentiation. Furthermore, XT-I overexpression is associated with fibrosis, whereby a fibrotic process initially develops from a dysregulated wound healing. In a physiologically wound healing process, extracellular matrix-producing myofibroblasts enter acute senescence to protect against fibrosis. The aim of this study was to determine the role of XT-I in acute senescent proto-myofibroblasts. Normal human dermal fibroblasts were seeded in a low cell density to promote myofibroblast differentiation and treated with H₂O₂ to induce acute senescence. Initiation of the acute senescence program in human proto-myofibroblasts resulted in a suppression of XYLT mRNA expression compared to the control, whereby the isoform XYLT1 was more affected than XYLT2. Moreover, the XT-I protein expression and enzyme activity were also reduced in H₂O₂-treated cells compared to the control. The examination of extracellular matrix remodeling revealed reduced expression of collagen I, fibronectin and decorin. In summary, acute senescent proto-myofibroblasts formed an anti-fibrotic phenotype, and suppression of XT-I during the induction process of acute senescence significantly contributed to subsequent ECM remodeling. XT-I therefore plays an important role in the switch between physiological and pathological wound healing.

Alterations in glycosaminoglycan biosynthesis associated with the Ehlers-Danlos syndromes

Proteoglycans consist of a core protein substituted with one or more glycosaminoglycan (GAG) chains and execute versatile functions during many physiological and pathological processes. The biosynthesis of GAG chains is a complex process that depends on the concerted action of a variety of enzymes. Central to the biosynthesis of heparan sulfate (HS) and chondroitin sulfate/dermatan sulfate (CS/DS) GAG chains is the formation of a tetrasaccharide linker region followed by biosynthesis of HS or CS/DS-specific repeating disaccharide units, which then undergo modifications and epimerization. The importance of these biosynthetic enzymes is illustrated by several severe pleiotropic disorders that arise upon their deficiency. The Ehlers-Danlos syndromes (EDS) constitute a special group among these disorders. Although most EDS types are caused by defects in fibrillar types I, III, or V collagen, or their modifying enzymes, a few rare EDS types have recently been linked to defects in GAG biosynthesis. Spondylodysplastic EDS (spEDS) is caused by defective formation of the tetrasaccharide linker region, either due to β4GalT7 or β3GalT6 deficiency, whereas musculocontractural EDS (mcEDS) results from deficiency of D4ST1 or DS-epi1, impairing DS formation. This narrative review highlights the consequences of GAG deficiency in these specific EDS types, summarizes the associated phenotypic features and the molecular spectrum of reported pathogenic variants, and defines the current knowledge on the underlying pathophysiological mechanisms based on studies in patient-derived material, in vitro analyses, and animal models.

Structure of the human heparan sulfate polymerase complex EXT1-EXT2

Heparan sulfates are complex polysaccharides that mediate the interaction with a broad range of protein ligands at the cell surface. A key step in heparan sulfate biosynthesis is catalyzed by the bi-functional glycosyltransferases EXT1 and EXT2, which generate the glycan backbone consisting of repeating N-acetylglucosamine and glucuronic acid units. The molecular mechanism of heparan sulfate chain polymerization remains, however, unknown. Here, we present the cryo-electron microscopy structure of human EXT1-EXT2, which reveals the formation of a tightly packed hetero-dimeric complex harboring four glycosyltransferase domains. A combination of in vitro and in cellulo mutational studies is used to dissect the functional role of the four catalytic sites. While EXT1 can catalyze both glycosyltransferase reactions, our results indicate that EXT2 might only have N-acetylglucosamine transferase activity. Our findings provide mechanistic insight into heparan sulfate chain elongation as a nonprocessive process and lay the foundation for future studies on EXT1-EXT2 function in health and disease.

The role of proteoglycan form of DMP1 in cranial repair

Background

The cranial region is a complex set of blood vessels, cartilage, nerves and soft tissues. The reconstruction of cranial defects caused by trauma, congenital defects and surgical procedures presents clinical challenges. Our previous data showed that deficiency of the proteoglycan (PG) form of dentin matrix protein 1 (DMP1-PG) could lead to abnormal cranial development. In addition, DMP1-PG was highly expressed in the cranial defect areas. The present study aimed to investigate the potential role of DMP1-PG in intramembranous ossification in cranial defect repair.

Methods

Mouse cranial defect models were established by using wild- type (WT) and DMP1-PG point mutation mice. Microcomputed tomography (micro-CT) and histological staining were performed to assess the extent of repair. Immunofluorescence assays and real-time quantitative polymerase chain reaction (RT‒qPCR) were applied to detect the differentially expressed osteogenic markers. RNA sequencing was performed to probe the molecular mechanism of DMP1-PG in regulating defect healing.

Results

A delayed healing process and an abnormal osteogenic capacity of primary osteoblasts were observed in DMP1-PG point mutation mice. Furthermore, impaired inflammatory signaling pathways were detected by using RNA transcription analysis of this model.

Conclusions

Our data indicate that DMP1-PG is an indispensable positive regulator during cranial defect healing.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-022-00443-4.

A Beginner’s Guide to the Characterization of Hydrogel Microarchitecture for Cellular Applications

The extracellular matrix (ECM) is a three-dimensional, acellular scaffold of living tissues. Incorporating the ECM into cell culture models is a goal of cell biology studies and requires biocompatible materials that can mimic the ECM. Among such materials are hydrogels: polymeric networks that derive most of their mass from water. With the tuning of their properties, these polymer networks can resemble living tissues. The microarchitectural properties of hydrogels, such as porosity, pore size, fiber length, and surface topology can determine cell plasticity. The adequate characterization of these parameters requires reliable and reproducible methods. However, most methods were historically standardized using other biological specimens, such as 2D cell cultures, biopsies, or even animal models. Therefore, their translation comes with technical limitations when applied to hydrogel-based cell culture systems. In our current work, we have reviewed the most common techniques employed in the characterization of hydrogel microarchitectures. Our review provides a concise description of the underlying principles of each method and summarizes the collective data obtained from cell-free and cell-loaded hydrogels. The advantages and limitations of each technique are discussed, and comparisons are made. The information presented in our current work will be of interest to researchers who employ hydrogels as platforms for cell culture, 3D bioprinting, and other fields within hydrogel-based research.

The structure of EXTL3 helps to explain the different roles of bi-domain exostosins in heparan sulfate synthesis

Heparan sulfate is a highly modified O-linked glycan that performs diverse physiological roles in animal tissues. Though quickly modified, it is initially synthesised as a polysaccharide of alternating β-D-glucuronosyl and N-acetyl-α-D-glucosaminyl residues by exostosins. These enzymes generally possess two glycosyltransferase domains (GT47 and GT64)-each thought to add one type of monosaccharide unit to the backbone. Although previous structures of murine exostosin-like 2 (EXTL2) provide insight into the GT64 domain, the rest of the bi-domain architecture is yet to be characterised; hence, how the two domains co-operate is unknown. Here, we report the structure of human exostosin-like 3 (EXTL3) in apo and UDP-bound forms. We explain the ineffectiveness of EXTL3's GT47 domain to transfer β-D-glucuronosyl units, and we observe that, in general, the bi-domain architecture would preclude a processive mechanism of backbone extension. We therefore propose that heparan sulfate backbone polymerisation occurs by a simple dissociative mechanism.

Serglycin Is Involved in TGF-β Induced Epithelial-Mesenchymal Transition and Is Highly Expressed by Immune Cells in Breast Cancer Tissue

Serglycin is a proteoglycan highly expressed by immune cells, in which its functions are linked to storage, secretion, transport, and protection of chemokines, proteases, histamine, growth factors, and other bioactive molecules. In recent years, it has been demonstrated that serglycin is also expressed by several other cell types, such as endothelial cells, muscle cells, and multiple types of cancer cells. Here, we show that serglycin expression is upregulated in transforming growth factor beta (TGF-β) induced epithelial-mesenchymal transition (EMT). Functional studies provide evidence that serglycin plays an important role in the regulation of the transition between the epithelial and mesenchymal phenotypes, and it is a significant EMT marker gene. We further find that serglycin is more expressed by breast cancer cell lines with a mesenchymal phenotype as well as the basal-like subtype of breast cancers. By examining immune staining and single cell sequencing data of breast cancer tissue, we show that serglycin is highly expressed by infiltrating immune cells in breast tumor tissue.

Hyaluronic Acid: Known for Almost a Century, but Still in Vogue

Hyaluronic acid (HA) has a special position among glycosaminoglycans. As a major component of the extracellular matrix (ECM). This simple, unbranched polysaccharide is involved in the regulation of various biological cell processes, whether under physiological conditions or in cases of cell damage. This review summarizes the history of this molecule's study, its distinctive metabolic pathway in the body, its unique properties, and current information regarding its interaction partners. Our main goal, however, is to intensively investigate whether this relatively simple polymer may find applications in protecting against ionizing radiation (IR) or for therapy in cases of radiation-induced damage. After exposure to IR, acute and belated damage develops in each tissue depending upon the dose received and the cellular composition of a given organ. A common feature of all organ damage is a distinct change in composition and structure of the ECM. In particular, the important role of HA was shown in lung tissue and the variability of this flexible molecule in the complex mechanism of radiation-induced lung injuries. Moreover, HA is also involved in intermediating cell behavior during morphogenesis and in tissue repair during inflammation, injury, and would healing. The possibility of using the HA polymer to affect or treat radiation tissue damage may point to the missing gaps in the responsible mechanisms in the onset of this disease. Therefore, in this article, we will also focus on obtaining answers from current knowledge and the results of studies as to whether hyaluronic acid can also find application in radiation science.

Proteoglycans in Cancer: Friends or Enemies? A Special Focus on Hepatocellular Carcinoma

Simple Summary

Proteoglycans affect multiple molecular and cellular processes during the progression of solid tumors with a highly desmoplastic stroma, such as HCC. Due to their role in enhancing or limiting the traits of cancer cells underlying their aggressiveness, such as proliferation, angiogenesis, epithelial to mesenchymal transition (EMT), and stemness, these macromolecules could be exploited as molecular targets or therapeutic agents. Proteoglycans, such as biglycan, versican, syndecan-1, glypican-3, and agrin, promote HCC cell proliferation, EMT, and angiogenesis, while endostatin and proteoglycan 4 were shown to impair cancer neovascularization or to enhance the sensitivity of HCC cells to drugs, such as sorafenib and regorafenib. Based on this evidence, interventional strategies involving the use of humanized monoclonal antibodies, T cells engineered with chimeric antigen receptors, or recombinant proteins mimicking potentially curative proteoglycans, are being employed or may be adopted in the near future for the treatment of HCC.

Abstract

Proteoglycans are a class of highly glycosylated proteins expressed in virtually all tissues, which are localized within membranes, but more often in the pericellular space and extracellular matrix (ECM), and are involved in tissue homeostasis and remodeling of the stromal microenvironment during physiological and pathological processes, such as tissue regeneration, angiogenesis, and cancer. In general, proteoglycans can perform signaling activities and influence a range of physical, chemical, and biological tissue properties, including the diffusivity of small electrolytes and nutrients and the bioavailability of growth factors. While the dysregulated expression of some proteoglycans is observed in many cancers, whether they act as supporters or limiters of neoplastic progression is still a matter of controversy, as the tumor promoting or suppressive function of some proteoglycans is context dependent. The participation of multiple proteoglycans in organ regeneration (as demonstrated for the liver in hepatectomy mouse models) and in cancer suggests that these molecules actively influence cell growth and motility, thus contributing to key events that characterize neoplastic progression. In this review, we outline the main roles of proteoglycans in the physiology and pathology of cancers, with a special mention to hepatocellular carcinoma (HCC), highlighting the translational potential of proteoglycans as targets or therapeutic agents for the treatment of this disease.

Role of extracellular matrix proteoglycans in immune cell recruitment

Leucocyte recruitment is a critical component of the immune response and is central to our ability to fight infection. Paradoxically, leucocyte recruitment is also a central component of inflammatory-based diseases such as rheumatoid arthritis, atherosclerosis and cancer. The role of the extracellular matrix, in particular proteoglycans, in this process has been largely overlooked. Proteoglycans consist of protein cores with glycosaminoglycan sugar side chains attached. Proteoglycans have been shown to bind and regulate the function of a number of proteins, for example chemokines, and also play a key structural role in the local tissue environment/niche. Whilst they have been implicated in leucocyte recruitment and inflammatory disease, their mechanistic function has yet to be fully understood, precluding therapeutic targeting. This review summarizes what is currently known about the role of proteoglycans in the different stages of leucocyte recruitment and proposes a number of areas where more research is needed. A better understanding of the mechanistic role of proteoglycans during inflammatory disease will inform the development of next-generation therapeutics.

Characterization of Cortical Glial Scars in the Diisopropylfluorophosphate (DFP) Rat Model of Epilepsy

Glial scars have been observed following stab lesions in the spinal cord and brain but not observed and characterized in chemoconvulsant-induced epilepsy models. Epilepsy is a disorder characterized by spontaneous recurrent seizures and can be modeled in rodents. Diisopropylfluorophosphate (DFP) exposure, like other real-world organophosphate nerve agents (OPNAs) used in chemical warfare scenarios, can lead to the development of status epilepticus (SE). We have previously demonstrated that DFP-induced SE promotes epileptogenesis which is characterized by the development of spontaneous recurrent seizures (SRS), gliosis, and neurodegeneration. In this study, we report classical glial scars developed in the piriform cortex, but not in the hippocampus, by 8 days post-exposure. We challenged both male and female rats with 4–5 mg/kg DFP (s.c.) followed immediately by 2 mg/kg atropine sulfate (i.m.) and 25 mg/kg pralidoxime (i.m.) and one hour later by midazolam (i.m). Glial scars were present in the piriform cortex/amygdala region in 73% of the DFP treated animals. No scars were found in controls. Scars were characterized by a massive clustering of reactive microglia surrounded by hypertrophic reactive astrocytes. The core of the scars was filled with a significant increase of IBA1 and CD68 positive cells and a significant reduction in NeuN positive cells compared to the periphery of the scars. There was a significantly higher density of reactive GFAP, complement 3 (C3), and inducible nitric oxide synthase (iNOS) positive cells at the periphery of the scar compared to similar areas in controls. We found a significant increase in chondroitin sulfate proteoglycans (CS-56) in the periphery of the scars compared to a similar region in control brains. However, there was no change in TGF-β1 or TGF-β2 positive cells in or around the scars in DFP-exposed animals compared to controls. In contrast to stab-induced scars, we did not find fibroblasts (Thy1.1) in the scar core or periphery. There were sex differences with respect to the density of iNOS, CD68, NeuN, GFAP, C3 and CS-56 positive cells. This is the first report of cortical glial scars in rodents with systemic chemoconvulsant-induced SE. Further investigation could help to elucidate the mechanisms of scar development and mitigation strategies.

Managing Skin Ageing as a Modifiable Disorder—The Clinical Application of Nourella® Dual Approach Comprising a Nano-Encapsulated Retinoid, Retilex-A® and a Skin Proteoglycan Replacement Therapy, Vercilex®

Skin ageing is a progressive, but modifiable, multi-factorial disorder that involves all the skin’s tissues. Due to its wide range of physiological and psychosocial complications, skin ageing requires rigorous clinical attention. In this review, we aim to encourage clinicians to consider skin ageing as a disorder and suggest a novel, dual approach to its clinical treatment. Topical retinoids and per-oral proteoglycans are promising, non-invasive, therapeutic modalities. To overcome the low bioavailability of conventional free retinoids, Nourella® cream with Retilex-A® (Pharma Medico, Aarhus, Denmark) was developed using a proprietary nano-encapsulation technology. The nano-encapsulation is a sophisticated ‘permeation/penetration enhancer’ that optimises topical drug delivery by increasing the surface availability and net absorption ratio. Treatment adherence is also improved by minimising skin irritation. Interventional evidence suggests the greater efficacy of Retilex-A® in improving skin thickness and elasticity compared with conventional free forms. It is also reported that the rejuvenating efficacy of Retilex-A® and tretinoin are comparable. Another skin anti-ageing approach is proteoglycan replacement therapy (PRT) with Vercilex®. Vercilex® in Nourella® tablet form has the potential to ameliorate proteoglycan dysmetabolism in aged skin by activating skin cells and improving collagen/elastin turnover. Replicated clinical trials evidenced that PRT can significantly enhance the density, elasticity and thickness of both intrinsically aged and photoaged skin. Evidently, Vercilex® and Retilex-A® share a range of bioactivities that underlie their synergistic activity, as observed in a clinical trial. Dual therapy with Nourella® tablets and cream produced greater effects on skin characteristics than monotherapy with each of the two treatments. In conclusion, Nourella® cream and tablets are safe and effective treatments for skin ageing; however, combining the two in a ‘dual skin rejuvenation system’ significantly improves treatment outcomes.

An ultrastructural 3D reconstruction method for observing the arrangement of collagen fibrils and proteoglycans in the human aortic wall under mechanical load

An insight into changes of soft biological tissue ultrastructures under loading conditions is essential to understand their response to mechanical stimuli. Therefore, this study offers an approach to investigate the arrangement of collagen fibrils and proteoglycans (PGs), which are located within the mechanically loaded aortic wall. The human aortic samples were either fixed directly with glutaraldehyde in the load-free state or subjected to a planar biaxial extension test prior to fixation. The aortic ultrastructure was recorded using electron tomography. Collagen fibrils and PGs were segmented using convolutional neural networks, particularly the ESPNet model. The 3D ultrastructural reconstructions revealed a complex organization of collagen fibrils and PGs. In particular, we observed that not all PGs are attached to the collagen fibrils, but some fill the spaces between the fibrils with a clear distance to the collagen. The complex organization cannot be fully captured or can be severely misinterpreted in 2D. The approach developed opens up practical possibilities, including the quantification of the spatial relationship between collagen fibrils and PGs as a function of the mechanical load. Such quantification can also be used to compare tissues under different conditions, e.g., healthy and diseased, to improve or develop new material models. STATEMENT OF SIGNIFICANCE: The developed approach enables the 3D reconstruction of collagen fibrils and proteoglycans as they are embedded in the loaded human aortic wall. This methodological pipeline comprises the knowledge of arterial mechanics, imaging with transmission electron microscopy and electron tomography, segmentation of 3D image data sets with convolutional neural networks and finally offers a unique insight into the ultrastructural changes in the aortic tissue caused by mechanical stimuli.

Biglycan Interacts with Type I Insulin-like Receptor (IGF-IR) Signaling Pathway to Regulate Osteosarcoma Cell Growth and Response to Chemotherapy

Simple Summary

Osteosarcoma (OS) is an aggressive, primary bone cancer. OS cells produce altered osteoid whose components participate in signaling correlated to the development of this cancer. Biglycan (BGN), a proteoglycan, is correlated to aggressive OS type and resistance to chemotherapy. A constitutive signaling of insulin-like growth factor receptor I (IGF-IR) signaling in sarcoma progression was established. We showed that biglycan binds IGF-IR resulting in prolonged IGF-IR activation, nuclear translocation, and growth response of the poorly-differentiated MG63 cells correlated to increased aggressiveness markers expression and enhanced chemoresistance. This mechanism is not valid in moderately and well-differentiated, biglycan non-expressing U-2OS and Saos-2 OS cells.

Abstract

Osteosarcoma (OS) is a mesenchymally derived, aggressive bone cancer. OS cells produce an aberrant nonmineralized or partly mineralized extracellular matrix (ECM) whose components participate in signaling pathways connected to specific pathogenic phenotypes of this bone cancer. The expression of biglycan (BGN), a secreted small leucine-rich proteoglycan (SLRP), is correlated to aggressive OS phenotype and resistance to chemotherapy. A constitutive signaling of IGF-IR signaling input in sarcoma progression has been established. Here, we show that biglycan activates the IGF-IR signaling pathway to promote MG63 biglycan-secreting OS cell growth by forming a complex with the receptor. Computational models of IGF-IR and biglycan docking suggest that biglycan binds IGF-IR dimer via its concave surface. Our binding free energy calculations indicate the formation of a stable complex. Biglycan binding results in prolonged IGF-IR activation leading to protracted IGF-IR-dependent cell growth response of the poorly-differentiated MG63 cells. Moreover, biglycan facilitates the internalization (p ≤ 0.01, p ≤ 0.001) and sumoylation-enhanced nuclear translocation of IGF-IR (p ≤ 0.05) and its DNA binding in MG63 cells (p ≤ 0.001). The tyrosine kinase activity of the receptor mediates this mechanism. Furthermore, biglycan downregulates the expression of the tumor-suppressor gene, PTEN (p ≤ 0.01), and increases the expression of endothelial–mesenchymal transition (EMT) and aggressiveness markers vimentin (p ≤ 0.01) and fibronectin (p ≤ 0.01) in MG63 cells. Interestingly, this mechanism is not valid in moderately and well-differentiated, biglycan non-expressing U-2OS and Saos-2 OS cells. Furthermore, biglycan exhibits protective effects against the chemotherapeutic drug, doxorubicin, in MG63 OS cells (p ≤ 0.01). In conclusion, these data indicate a potential direct and adjunct therapeutical role of biglycan in osteosarcoma.

The Ehlers–Danlos Syndromes against the Backdrop of Inborn Errors of Metabolism

The Ehlers–Danlos syndromes are a group of multisystemic heritable connective tissue disorders with clinical presentations that range from multiple congenital malformations, over adolescent-onset debilitating or even life-threatening complications of connective tissue fragility, to mild conditions that remain undiagnosed in adulthood. To date, thirteen different EDS types have been recognized, stemming from genetic defects in 20 different genes. While initial biochemical and molecular analyses mainly discovered defects in genes coding for the fibrillar collagens type I, III and V or their modifying enzymes, recent discoveries have linked EDS to defects in non-collagenous matrix glycoproteins, in proteoglycan biosynthesis and in the complement pathway. This genetic heterogeneity explains the important clinical heterogeneity among and within the different EDS types. Generalized joint hypermobility and skin hyperextensibility with cutaneous fragility, atrophic scarring and easy bruising are defining manifestations of EDS; however, other signs and symptoms of connective tissue fragility, such as complications of vascular and internal organ fragility, orocraniofacial abnormalities, neuromuscular involvement and ophthalmological complications are variably present in the different types of EDS. These features may help to differentiate between the different EDS types but also evoke a wide differential diagnosis, including different inborn errors of metabolism. In this narrative review, we will discuss the clinical presentation of EDS within the context of inborn errors of metabolism, give a brief overview of their underlying genetic defects and pathophysiological mechanisms and provide a guide for the diagnostic approach.

A Glycoproteomic Approach to Identify Novel Proteoglycans

In this chapter, we describe a glycoproteomic approach for the identification of novel chondroitin sulfate proteoglycans (CSPGs) using a combination of biochemical enrichments, enzymatic digestions, and nanoscale liquid chromatography tandem mass spectrometry (nLC-MS/MS) analysis. The identification is achieved by trypsin digestion of CSPG-containing samples, followed by enrichment of chondroitin sulfate (CS) glycopeptides by strong anion exchange chromatography (SAX). The enriched CS glycopeptides are then digested with chondroitinase ABC to depolymerize the CS polysaccharides, generating a residual hexasaccharide structure, composed of the linkage region tetrasaccharide extended with a terminal dehydrated disaccharide, still attached to the peptide. The obtained CS glycopeptides are analyzed by nLC-MS/MS, and the generated data sets are evaluated through proteomic software with adjustment in the settings to allow for glycopeptide identification. This approach has enabled the identification of several novel core proteins in human samples and in Caenorhabditis elegans. Here we specifically describe the procedure for the enrichment and characterization of CS glycopeptides from human cerebrospinal fluid (CSF).

Revisiting the grammar of Tau aggregation and pathology formation: how new insights from brain pathology are shaping how we study and target Tauopathies

Converging evidence continues to point towards Tau aggregation and pathology formation as central events in the pathogenesis of Alzheimer's disease and other Tauopathies. Despite significant advances in understanding the morphological and structural properties of Tau fibrils, many fundamental questions remain about what causes Tau to aggregate in the first place. The exact roles of cofactors, Tau post-translational modifications, and Tau interactome in regulating Tau aggregation, pathology formation, and toxicity remain unknown. Recent studies have put the spotlight on the wide gap between the complexity of Tau structures, aggregation, and pathology formation in the brain and the simplicity of experimental approaches used for modeling these processes in research laboratories. Embracing and deconstructing this complexity is an essential first step to understanding the role of Tau in health and disease. To help deconstruct this complexity and understand its implication for the development of effective Tau targeting diagnostics and therapies, we firstly review how our understanding of Tau aggregation and pathology formation has evolved over the past few decades. Secondly, we present an analysis of new findings and insights from recent studies illustrating the biochemical, structural, and functional heterogeneity of Tau aggregates. Thirdly, we discuss the importance of adopting new experimental approaches that embrace the complexity of Tau aggregation and pathology as an important first step towards developing mechanism- and structure-based therapies that account for the pathological and clinical heterogeneity of Alzheimer's disease and Tauopathies. We believe that this is essential to develop effective diagnostics and therapies to treat these devastating diseases.