Pleiotrophin: Activity and mechanism

αMI-domain of integrin Mac-1 binds the cytokine pleiotrophin using multiple mechanisms

The integrin Mac-1 (αMβ2, CD11b/CD18, CR3) is an adhesion receptor expressed on macrophages and neutrophils. Mac-1 is also a promiscuous integrin that binds a diverse set of ligands through its αMI-domain. However, the binding mechanism of most ligands remains unclear. We have characterized the interaction of αMI-domain with the cytokine pleiotrophin (PTN), a protein known to bind αMI-domain and induce Mac-1-mediated cell adhesion and migration. Our data show that PTN's N-terminal domain binds a unique site near the N- and C-termini of the αMI-domain using a metal-independent mechanism. However, a stronger interaction is achieved when an acidic amino acid in a zwitterionic motif in PTN's C-terminal domain chelates the divalent cation in the metal ion-dependent adhesion site of active αMI-domain. These results indicate that αMI-domain can bind ligands using multiple mechanisms and that the active αMI-domain has a preference for motifs containing both positively and negatively charged amino acids.

CircRNAs in Pancreatic Cancer: New Tools for Target Identification and Therapeutic Intervention

We have reviewed the literature for circular RNAs (circRNAs) with efficacy in preclinical pancreatic-cancer related in vivo models. The identified circRNAs target chemoresistance mechanisms (n=5), secreted proteins and transmembrane receptors (n=15), transcription factors (n=9), components of the signaling- (n=11), ubiquitination- (n=2), autophagy-system (n=2), and others (n=9). In addition to identifying targets for therapeutic intervention, circRNAs are potential new entities for treatment of pancreatic cancer. Up-regulated circRNAs can be inhibited by antisense oligonucleotides (ASO), small interfering RNAs (siRNAs), short hairpin RNAs (shRNAs) or clustered regularly interspaced short-palindromic repeats-CRISPR associated protein (CRISPR-CAS)-based intervention. The function of down-regulated circRNAs can be reconstituted by replacement therapy using plasmids or virus-based vector systems. Target validation experiments and the development of improved delivery systems for corresponding agents were examined.

Medulloblastoma Spatial Transcriptomics Reveals Tumor Microenvironment Heterogeneity with High-Density Progenitor Cell Regions Correlating with High-Risk Disease

The tumor microenvironment (TME) of medulloblastoma (MB) influences progression and therapy response, presenting a promising target for therapeutic advances. Prior single-cell analyses have characterized the cellular components of the TME but lack spatial context. To address this, we performed spatial transcriptomic sequencing on sixteen pediatric MB samples obtained at diagnosis, including two matched diagnosis-relapse pairs. Our analyses revealed inter- and intra-tumoral heterogeneity within the TME, comprised of tumor-associated astrocytes (TAAs), macrophages (TAMs), stromal components, and distinct subpopulations of MB cells at different stages of neuronal differentiation and cell cycle progression. We identified dense regions of quiescent progenitor-like MB cells enriched in patients with high-risk (HR) features and an increase in TAAs, TAMs, and dysregulated vascular endothelium following relapse. Our study presents novel insights into the spatial architecture and cellular landscape of the medulloblastoma TME, highlighting spatial patterns linked to HR features and relapse, which may serve as potential therapeutic targets.

A Subpopulation of Luminal Progenitors Secretes Pleiotrophin to Promote Angiogenesis and Metastasis in Inflammatory Breast Cancer

Inflammatory breast cancer (IBC) is a highly aggressive subtype of breast cancer characterized by rapidly arising diffuse erythema and edema. Genomic studies have not identified consistent alterations and mechanisms that differentiate IBC from non-IBC tumors, suggesting that the microenvironment could be a potential driver of IBC phenotypes. Here, using single-cell RNA sequencing, multiplex staining, and serum analysis in patients with IBC, we identified enrichment of a subgroup of luminal progenitor (LP) cells containing high expression of the neurotropic cytokine pleiotrophin (PTN) in IBC tumors. PTN secreted by the LP cells promoted angiogenesis by directly interacting with the NRP1 receptor on endothelial tip cells located in both IBC tumors and the affected skin. NRP1 activation in tip cells led to recruitment of immature perivascular cells in the affected skin of IBC, which are correlated with increased angiogenesis and IBC metastasis. Together, these findings reveal a role for cross-talk between LPs, endothelial tip cells, and immature perivascular cells via PTN-NRP1 axis in the pathogenesis of IBC, which could lead to improved strategies for treating IBC.

SIGNIFICANCE

Nonmalignant luminal progenitor cells expressing pleiotrophin promote angiogenesis by activating NRP1 and induce a prometastatic tumor microenvironment in inflammatory breast cancer, providing potential therapeutic targets for this aggressive breast cancer subtype.

A Novel Mechanism of MSCs Responding to Occlusal Force for Bone Homeostasis

Alveolar bone, as tooth-supporting bone for mastication, is sensitive to occlusal force. However, the mechanism of alveolar bone loss after losing occlusal force remains unclear. Here, we performed single-cell RNA sequencing of nonhematopoietic (CD45-) cells in mouse alveolar bone after removing the occlusal force. Mesenchymal stromal cells (MSCs) and endothelial cell (EC) subsets were significantly decreased in frequency, as confirmed by immunofluorescence and flow cytometry. The osteogenic and proangiogenic abilities of MSCs were impaired, and the expression of mechanotransducers yes associated protein 1 (Yap) and WW domain containing transcription regulator 1 (Taz) in MSCs decreased. Conditional deletion of Yap and Taz from LepR+ cells, which are enriched in MSCs that are important for adult bone homeostasis, significantly decreased alveolar bone mass and resisted any further changes in bone mass induced by occlusal force changes. Interestingly, LepR-Cre; Yapf/f; Tazf/f mice showed a decrease in CD31hi endomucin (Emcn)hi endothelium, and the expression of some EC-derived signals acting on osteoblastic cells was inhibited in alveolar bone. Mechanistically, conditional deletion of Yap and Taz in LepR+ cells inhibited the secretion of pleiotrophin (Ptn), which impaired the proangiogenic capacity of LepR+ cells. Knockdown in MSC-derived Ptn repressed human umbilical vein EC tube formation in vitro. More important, administration of recombinant PTN locally recovered the frequency of CD31hiEmcnhi endothelium and rescued the low bone mass phenotype of LepR-Cre; Yapf/f; Tazf/f mice. Taken together, these findings suggest that occlusal force governs MSC-regulated endothelium to maintain alveolar bone homeostasis through the Yap/Taz/Ptn axis, providing a reference for further understanding of the relationship between dysfunction and bone homeostasis.

Deciphering Müller cell heterogeneity signatures in diabetic retinopathy across species: an integrative single-cell analysis

Diabetic retinopathy (DR), a leading cause of visual impairment, demands a profound comprehension of its cellular mechanisms to formulate effective therapeutic strategies. Our study presentes a comprehensive single-cell analysis elucidating the intricate landscape of Müller cells within DR, emphasizing their nuanced involvement. Utilizing scRNA-seq data from both Sprague-Dawley rat models and human patients, we delineated distinct Müller cell clusters and their corresponding gene expression profiles. These findings were further validated through differential gene expression analysis utilizing human transcriptomic data. Notably, certain Müller cell clusters displayed upregulation of the Rho gene, implying a phagocytic response to damaged photoreceptors within the DR microenvironment. This phenomenon was consistently observed across species. Additionally, the co-expression patterns of RHO and PDE6G within Müller cell clusters provided compelling evidence supporting their potential role in maintaining retinal integrity during DR. Our results offer novel insights into the cellular dynamics of DR and underscore Müller cells as promising therapeutic targets for preserving vision in retinal disorders induced by diabetes.

Schwann cell derived pleiotrophin stimulates fibroblast for proliferation and excessive collagen deposition in plexiform neurofibroma

Neurofibromatosis type 1 associated plexiform neurofibroma (pNF) is characterized by abundant fibroblasts and dense collagen, yet the intricate interactions between tumor-origin cells (Schwann cells) and neurofibroma-associated fibroblasts (NFAFs) remain elusive. Employing single-cell RNA sequencing on human pNF samples, we generated a comprehensive transcriptomics dataset and conducted cell-cell communication analysis to unravel the molecular dynamics between Schwann cells and NFAFs. Our focus centered on the pleiotrophin (PTN)/nucleolin (NCL) axis as a pivotal ligand-receptor pair orchestrating this interaction. Validation of PTN involvement was affirmed through coculture models and recombinant protein experiments. Functional and mechanistic investigations, employing assays such as CCK8, EdU, Western Blot, ELISA, Hydroxyproline Assay, and Human phospho-kinase array, provided critical insights. We employed siRNA or inhibitors to intercept the PTN/NCL/proline-rich Akt substrate of 40 kDa (PRAS40) axis, validating the associated molecular mechanism. Our analysis highlighted a subset of Schwann cells closely linked to collagen deposition, underscoring their significance in pNF development. The PTN/NCL axis emerged as a key mediator of the Schwann cell-NFAF interaction. Furthermore, our study demonstrated that elevated PTN levels enhanced NFAF proliferation and collagen synthesis, either independently or synergistically with TGF-β1 in vitro. Activation of the downstream molecule PRAS40 was noted in NFAFs upon PTN treatment. Crucially, by targeting NCL and PRAS40, we successfully reversed collagen synthesis within NFAFs. In conclusion, our findings unveil the pivotal role of the PTN/NCL/PRAS40 axis in driving pNF development by promoting NFAFs proliferation and function. Targeting this pathway emerges as a potential therapeutic strategy for pNF. This study contributes novel insights into the molecular mechanisms governing pNF pathogenesis.

MicroRNA-guided drug discovery for mitigating persistent pulmonary complications in critical COVID-19 survivors: A longitudinal pilot study

BACKGROUND AND PURPOSE

The post-acute sequelae of SARS-CoV-2 infection pose a significant global challenge, with nearly 50% of critical COVID-19 survivors manifesting persistent lung abnormalities. The lack of understanding about the molecular mechanisms and effective treatments hampers their management. Here, we employed microRNA (miRNA) profiling to decipher the systemic molecular underpinnings of the persistent pulmonary complications.

EXPERIMENTAL APPROACH

We conducted a longitudinal investigation including 119 critical COVID-19 survivors. A comprehensive pulmonary evaluation was performed in the short-term (median = 94.0 days after hospital discharge) and long-term (median = 358 days after hospital discharge). Plasma miRNAs were quantified at the short-term evaluation using the gold-standard technique, RT-qPCR. The analyses combined machine learning feature selection techniques with bioinformatic investigations. Two additional datasets were incorporated for validation.

KEY RESULTS

In the short-term, 84% of the survivors exhibited impaired lung diffusion (DLCO  < 80% of predicted). One year post-discharge, 54.4% of this patient subgroup still presented abnormal DLCO . Four feature selection methods identified two specific miRNAs, miR-9-5p and miR-486-5p, linked to persistent lung dysfunction. The downstream experimentally validated targetome included 1473 genes, with heterogeneous enriched pathways associated with inflammation, angiogenesis and cell senescence. Validation studies using RNA-sequencing and proteomic datasets emphasized the pivotal roles of cell migration and tissue repair in persistent lung dysfunction. The repositioning potential of the miRNA targets was limited.

CONCLUSION AND IMPLICATIONS

Our study reveals early mechanistic pathways contributing to persistent lung dysfunction in critical COVID-19 survivors, offering a promising approach for the development of targeted disease-modifying agents.

αMI-domain of Integrin Mac-1 Binds the Cytokine Pleiotrophin Using Multiple Mechanisms

The integrin Mac-1 (αMβ2, CD11b/CD18, CR3) is an important adhesion receptor expressed on macrophages and neutrophils. Mac-1 is also the most promiscuous member of the integrin family that binds a diverse set of ligands through its αMI-domain. However, the binding mechanism of most ligands is not clear. We have determined the interaction of αMI-domain with the cytokine pleiotrophin (PTN), a cationic protein known to bind αMI-domain and induce Mac-1-mediated cell adhesion and migration. Our data show that PTN's N-terminal domain binds a unique site near the N- and C-termini of the αMI-domain using a metal-independent mechanism. However, stronger interaction is achieved when an acidic amino acid in a zwitterionic motif in PTN's C-terminal domain chelates the divalent cation in the metal ion-dependent adhesion site of the active αMI-domain. These results indicate that αMI-domain can bind ligands using multiple mechanisms, and suggest that active αMI-domain prefers acidic amino acids in zwitterionic motifs.

Multi-omics analysis reveals cuproptosis and mitochondria-based signature for assessing prognosis and immune landscape in osteosarcoma

Background

Osteosarcoma (OSA), the most common primary mesenchymal bone tumor, is a health threat to children and adolescents with a dismal prognosis. While cuproptosis and mitochondria dysfunction have been demonstrated to exert a crucial role in tumor progression and development, the mechanisms by which they are regulated in OSA still await clarification.

Methods

Two independent OSA cohorts containing transcriptome data and clinical information were collected from public databases. The heterogeneity of OSA were evaluated by single cell RNA (scRNA) analysis. To identify a newly molecular subtype, unsupervised consensus clustering was conducted. Cox relevant regression methods were utilized to establish a prognostic gene signature. Wet lab experiments were performed to confirm the effect of model gene in OSA cells.

Results

We determined 30 distinct cell clusters and assessed OSA heterogeneity and stemness scRNA analysis. Then, univariate Cox analysis identified 24 candidate genes which were greatly associated with the prognosis of OSA. Based on these prognostic genes, we obtained two molecular subgroups. After conducting step Cox regression, three model genes were selected to construct a signature showing a favorable performance to forecast clinical outcome. Our proposed signature could also evaluate the response to chemotherapy and immunotherapy of OSA cases.

Conclusion

We generated a novel risk model based on cuproptosis and mitochondria-related genes in OSA with powerful predictive ability in prognosis and immune landscape.

The uterine secretory cycle: recurring physiology of endometrial outputs that setup the uterine luminal microenvironment

Conserved in female reproduction across all mammalian species is the estrous cycle and its regulation by the hypothalamic-pituitary-gonadal (HPG) axis, a collective of intersected hormonal events that are crucial for ensuring uterine fertility. Nonetheless, knowledge of the direct mediators that synchronously shape the uterine microenvironment for successive yet distinct events, such as the transit of sperm and support for progressive stages of preimplantation embryo development, remain principally deficient. Toward understanding the timed endometrial outputs that permit luminal events as directed by the estrous cycle, we used Bovidae as a model system to uniquely surface sample and study temporal shifts to in vivo endometrial transcripts that encode for proteins destined to be secreted. The results revealed the full quantitative profile of endometrial components that shape the uterine luminal microenvironment at distinct phases of the estrous cycle (estrus, metestrus, diestrus, and proestrus). In interpreting this comprehensive log of stage-specific endometrial secretions, we define the "uterine secretory cycle" and extract a predictive understanding of recurring physiological actions regulated within the uterine lumen in anticipation of sperm and preimplantation embryonic stages. This repetitive microenvironmental preparedness to sequentially provide operative support was a stable intrinsic framework, with only limited responses to sperm or embryos if encountered in the lumen within the cyclic time period. In uncovering the secretory cycle and unraveling realistic biological processes, we present novel foundational knowledge of terminal effectors controlled by the HPG axis to direct a recurring sequence of vital functions within the uterine lumen.NEW & NOTEWORTHY This study unravels the recurring sequence of changes within the uterus that supports vital functions (sperm transit and development of preimplantation embryonic stages) during the reproductive cycle in female Ruminantia. These data present new systems knowledge in uterine reproductive physiology crucial for setting up in vitro biomimicry and artificial environments for assisted reproduction technologies for a range of mammalian species.

RAPIDASH: A tag-free enrichment of ribosome-associated proteins reveals compositional dynamics in embryonic tissues and stimulated macrophages

Ribosomes are emerging as direct regulators of gene expression, with ribosome-associated proteins (RAPs) allowing ribosomes to modulate translational control. However, a lack of technologies to enrich RAPs across many sample types has prevented systematic analysis of RAP number, dynamics, and functions. Here, we have developed a label-free methodology called RAPIDASH to enrich ribosomes and RAPs from any sample. We applied RAPIDASH to mouse embryonic tissues and identified hundreds of potential RAPs, including DHX30 and LLPH, two forebrain RAPs important for neurodevelopment. We identified a critical role of LLPH in neural development that is linked to the translation of genes with long coding sequences. Finally, we characterized ribosome composition remodeling during immune activation and observed extensive changes post-stimulation. RAPIDASH has therefore enabled the discovery of RAPs ranging from those with neuroregulatory functions to those activated by immune stimuli, thereby providing critical insights into how ribosomes are remodeled.

The Role and Therapeutic Implications of Inflammation in the Pathogenesis of Brain Arteriovenous Malformations

Brain arteriovenous malformations (bAVMs) are focal vascular lesions composed of abnormal vascular channels without an intervening capillary network. As a result, high-pressure arterial blood shunts directly into the venous outflow system. These high-flow, low-resistance shunts are composed of dilated, tortuous, and fragile vessels, which are prone to rupture. BAVMs are a leading cause of hemorrhagic stroke in children and young adults. Current treatments for bAVMs are limited to surgery, embolization, and radiosurgery, although even these options are not viable for ~20% of AVM patients due to excessive risk. Critically, inflammation has been suggested to contribute to lesion progression. Here we summarize the current literature discussing the role of the immune system in bAVM pathogenesis and lesion progression, as well as the potential for targeting inflammation to prevent bAVM rupture and intracranial hemorrhage. We conclude by proposing that a dysfunctional endothelium, which harbors the somatic mutations that have been shown to give rise to sporadic bAVMs, may drive disease development and progression by altering the immune status of the brain.

Whole transcriptome analysis of canine pheochromocytoma and paraganglioma

Pheochromocytomas and paragangliomas (PPGLs) are neuroendocrine tumors arising from the chromaffin cells in the adrenal medulla and extra-adrenal paraganglia, respectively. Local invasion, concurrent disorders, and metastases prevent surgical removal, which is the most effective treatment to date. Given the current lack of effective medical treatment, there is a need for novel therapeutic strategies. To identify druggable pathways driving PPGL development, we performed RNA sequencing on PPGLs (n = 19) and normal adrenal medullas (NAMs; n = 10) of dogs. Principal component analysis (PCA) revealed that PPGLs clearly clustered apart from NAMs. In total, 4,218 genes were differentially expressed between PPGLs and NAMs. Of these, 232 had a log2 fold change of >3 or < -3, of which 149 were upregulated in PPGLs, and 83 were downregulated. Compared with NAMs, PPGLs had increased expression of genes related to the cell cycle, tumor development, progression and metastasis, hypoxia and angiogenesis, and the Wnt signaling pathway, and decreased expression of genes related to adrenal steroidogenesis. Our data revealed several overexpressed genes that could provide targets for novel therapeutics, such as Ret Proto-Oncogene (RET), Dopamine Receptor D2 (DRD2), and Secreted Frizzled Related Protein 2 (SFRP2). Based on the PCA, PPGLs were classified into 2 groups, of which group 1 had significantly higher Ki67 scores (p = 0.035) and shorter survival times (p = 0.04) than group 2. Increased expression of 1 of the differentially expressed genes between group 1 and 2, pleiotrophin (PTN), appeared to correlate with a more aggressive tumor phenotype. This study has shed light on the transcriptomic profile of canine PPGL, yielding new insights into the pathogenesis of these tumors in dogs, and revealed potential novel targets for therapy. In addition, we identified 2 transcriptionally distinct groups of PPGLs that had significantly different survival times.

Pleiotrophin ameliorates white matter injury of neonatal rats by activating the mTOR/YY1/Id4 signaling pathway

Brain white matter injury (WMI) is a serious disease of the central nervous system. Pleiotrophin (PTN) promotes the differentiation and myelination of oligodendrocytes (OLs) in vitro. However, the role of PTN in WMI remains unknown. Therefore, this study aimed to investigate the neuroprotective role and potential mechanisms of PTN function in neonatal rats with WMI. The PTN and mammalian target of rapamycin (mTOR) inhibitor everolimus was used to treat a WMI model in postnatal day 3 Sprague-Dawley rats, in which the right common carotid arteries of these rats were isolated, ligated, and exposed to a hypoxic environment (6% O₂  + 94% N₂ ) for 2 h. OL differentiation and myelination, as well as the spatial learning and memory abilities of the rats were evaluated to examine the effects of PTN. Two proteins of the mTOR signaling pathway, YingYang1 (YY1) and inhibitor of DNA binding 4 (Id4), were detected and were used to explore the potential mechanisms of PTN in rat WMI experiment and oxygen glucose deprivation (OGD) model. We found that the differentiation and myelination of OLs were impaired after WMI. PTN administration rescued this injury by activating mTOR/YY1 and inhibiting Id4. Everolimus administration inhibited mTOR/YY1 and activated Id4, which blocked the neuroprotective role of PTN in WMI. PTN plays a neuroprotective role in neonatal rats with WMI, which could be involved in the mTOR/YY1/Id4 signaling pathway.

Pleiotrophin Signals Through ALK Receptor to Enhance the Growth of Neurons in the Presence of Inhibitory Chondroitin Sulfate Proteoglycans

Chondroitin sulfate proteoglycans (CSPGs), one of the major extracellular matrix components of the glial scar that surrounds central nervous system (CNS) injuries, are known to inhibit the regeneration of neurons. This study investigated whether pleiotrophin (PTN), a growth factor upregulated during early CNS development, can overcome the inhibition mediated by CSPGs and promote the neurite outgrowth of neurons in vitro. The data showed that a CSPG matrix inhibited the outgrowth of neurites in primary cortical neuron cultures compared to a control matrix. PTN elicited a dose-dependent increase in the neurite outgrowth even in the presence of the growth inhibitory CSPG matrix, with optimal growth at 15 ng mL-1 of PTN (114.8% of neuronal outgrowth relative to laminin control). The growth-promoting effect of PTN was blocked by inhibition of the receptor anaplastic lymphoma kinase (ALK) by alectinib in a dose-dependent manner. Neurite outgrowth in the presence of this CSPG matrix was induced by activation of the protein kinase B (AKT) pathway, a key downstream mediator of ALK activation. This study identified PTN as a dose-dependent regulator of neurite outgrowth in primary cortical neurons cultured in the presence of a CSPG matrix and identified ALK activation as a key driver of PTN-induced growth.

Pleiotrophin and metabolic disorders: insights into its role in metabolism

Pleiotrophin (PTN) is a cytokine which has been for long studied at the level of the central nervous system, however few studies focus on its role in the peripheral organs. The main aim of this review is to summarize the state of the art of what is known up to date about pleiotrophin and its implications in the main metabolic organs. In summary, pleiotrophin promotes the proliferation of preadipocytes, pancreatic β cells, as well as cells during the mammary gland development. Moreover, this cytokine is important for the structural integrity of the liver and the neuromuscular junction in the skeletal muscle. From a metabolic point of view, pleiotrophin plays a key role in the maintenance of glucose and lipid as well as whole-body insulin homeostasis and favors oxidative metabolism in the skeletal muscle. All in all, this review proposes pleiotrophin as a druggable target to prevent from the development of insulin-resistance-related pathologies.

Single-cell RNA sequencing reveals the mediatory role of cancer-associated fibroblast PTN in hepatitis B virus cirrhosis-HCC progression

BACKGROUND

Cancer-associated fibroblasts (CAFs) are essential stromal components in the tumor microenvironment of hepatocellular carcinoma (HCC). Hepatitis B virus (HBV) infection induces pathological changes such as liver fibrosis/cirrhosis and HCC. The aim of this research was to explore the novel mediators of CAFs to modulate HBV cirrhosis-HCC progression.

METHODS

The single-cell transcriptome data of HCC were divided into subsets, and the significant subset related to fibrotic cells, along with biological function, and clinical information of HCC was revealed by integrated data analyses. The cell communication, cells communicated weight analysis of signaling pathways, and key genes in signaling pathways analysis of significant CAFs subclasses were conducted to discover the novel gene of CAFs. Bioinformatics, vitro and HBV transfection assays were used to verify the novel gene is an important target for promoting the progression HBV cirrhosis-HCC progression.

RESULTS

Fibroblasts derived from HCC single-cell data could be separated into three cell subclasses (CAF0-2), of which CAF2 was associated with the HCC clinical information. Fibroblasts have opposite developmental trajectories to immune B cells and CD8 + T cells. CAF0-2 had strong interaction with B cells and CD8 + T cells, especially CAF2 had the highest interaction frequency and weight with B cells and CD8 + T cells. Moreover, PTN participated in CAF2-related pathways involved in the regulation of cell communication, and the interactions among CAF2 and PTN contributed the most to B cells and CD8 + T cells. Furthermore, the genes of PTN, SDC1, and NCL from PTN signaling were highest expression in CAF2, B cells, and CD8 + T cells, respectively, and the interaction of PTN- SDC1 and PTN- NCL contributed most to the interaction of CAF2- B cells and CAF2-CD8 + T cells. Bioinformatics and vitro experiments confirm PTN was upregulated in HCC and promoted the proliferation of tumor cells, and HBV infection could initiate PTN to perform cirrhosis-HCC progression.

CONCLUSION

Our findings revealed CAF was associated with hepatocarcinogenesis, and the functional importance of B cells and CD8 + T cells in modulating CAF in HCC. Importantly, PTN maybe a novel mediator of CAF to mediate HBV cirrhosis-HCC progression.

Pleiotrophin drives a prometastatic immune niche in breast cancer

Metastatic cancer cells adapt to thrive in secondary organs. To investigate metastatic adaptation, we performed transcriptomic analysis of metastatic and non-metastatic murine breast cancer cells. We found that pleiotrophin (PTN), a neurotrophic cytokine, is a metastasis-associated factor that is expressed highly by aggressive breast cancers. Moreover, elevated PTN in plasma correlated significantly with metastasis and reduced survival of breast cancer patients. Mechanistically, we find that PTN activates NF-κB in cancer cells leading to altered cytokine production, subsequent neutrophil recruitment, and an immune suppressive microenvironment. Consequently, inhibition of PTN, pharmacologically or genetically, reduces the accumulation of tumor-associated neutrophils and reverts local immune suppression, resulting in increased T cell activation and attenuated metastasis. Furthermore, inhibition of PTN significantly enhanced the efficacy of immune checkpoint blockade and chemotherapy in reducing metastatic burden in mice. These findings establish PTN as a previously unrecognized driver of a prometastatic immune niche and thus represents a promising therapeutic target for the treatment of metastatic breast cancer.

The Active Role of Pericytes During Neuroinflammation in the Adult Brain

Microvessels in the central nervous system (CNS) have one of the highest populations of pericytes, indicating their crucial role in maintaining homeostasis. Pericytes are heterogeneous cells located around brain microvessels; they present three different morphologies along the CNS vascular tree: ensheathing, mesh, and thin-strand pericytes. At the arteriole-capillary transition ensheathing pericytes are found, while mesh and thin-strand pericytes are located at capillary beds. Brain pericytes are essential for the establishment and maintenance of the blood-brain barrier, which restricts the passage of soluble and potentially toxic molecules from the circulatory system to the brain parenchyma. Pericytes play a key role in regulating local inflammation at the CNS. Pericytes can respond differentially, depending on the degree of inflammation, by secreting a set of neurotrophic factors to promote cell survival and regeneration, or by potentiating inflammation through the release of inflammatory mediators (e.g., cytokines and chemokines), and the overexpression of cell adhesion molecules. Under inflammatory conditions, pericytes may regulate immune cell trafficking to the CNS and play a role in perpetuating local inflammation. In this review, we describe pericyte responses during acute and chronic neuroinflammation.

Pharmacological targeting of the receptor ALK inhibits tumorigenicity and overcomes chemoresistance in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive disease characterized by its metastatic potential and chemoresistance. These traits are partially attributable to the highly tumorigenic pancreatic cancer stem cells (PaCSCs). Interestingly, these cells show unique features in order to sustain their identity and functionality, some of them amenable for therapeutic intervention. Screening of phospho-receptor tyrosine kinases revealed that PaCSCs harbored increased activation of anaplastic lymphoma kinase (ALK). We subsequently demonstrated that oncogenic ALK signaling contributes to tumorigenicity in PDAC patient-derived xenografts (PDXs) by promoting stemness through ligand-dependent activation. Indeed, the ALK ligands midkine (MDK) or pleiotrophin (PTN) increased self-renewal, clonogenicity and CSC frequency in several in vitro local and metastatic PDX models. Conversely, treatment with the clinically-approved ALK inhibitors Crizotinib and Ensartinib decreased PaCSC content and functionality in vitro and in vivo, by inducing cell death. Strikingly, ALK inhibitors sensitized chemoresistant PaCSCs to Gemcitabine, as the most used chemotherapeutic agent for PDAC treatment. Consequently, ALK inhibition delayed tumor relapse after chemotherapy in vivo by effectively decreasing the content of PaCSCs. In summary, our results demonstrate that targeting the MDK/PTN-ALK axis with clinically-approved inhibitors impairs in vivo tumorigenicity and chemoresistance in PDAC suggesting a new treatment approach to improve the long-term survival of PDAC patients.

Single-cell RNA sequencing analysis of human chondrocytes reveals cell-cell communication alterations mediated by interactive signaling pathways in osteoarthritis

Objective: Osteoarthritis (OA) is a common joint disorder characterized by degenerative articular cartilage, subchondral bone remodeling, and inflammation. Increasing evidence suggests that the substantial crosstalk between cartilage and synovium is closely related to Osteoarthritis development, but the events that cause this degeneration remain unknown. This study aimed to explore the alterations in intercellular communication involved in the pathogenesis of Osteoarthritis using bioinformatics analysis. Methods: Single-cell transcriptome sequencing (scRNA-seq) profiles derived from articular cartilage tissue of patients with Osteoarthritis were downloaded from a public database. Chondrocyte heterogeneity was assessed using computational analysis, and cell type identification and clustering analysis were performed using the "FindClusters" function in the Seurat package. Intercellular communication networks, including major signaling inputs and outputs for cells, were predicted, and analyzed using CellChat. Results: Seven molecularly defined chondrocytes clusters (homeostatic chondrocytes, hypertrophic chondrocyte (HTC), pre-HTC, regulatory chondrocytes, fibro-chondrocytes (FC), pre-FC, and reparative chondrocyte) with different compositions were identified in the damaged cartilage. Compared to those in the intact cartilage, the overall cell-cell communication frequency and communication strength were remarkably increased in the damaged cartilage. The cellular communication among chondrocyte subtypes mediated by signaling pathways, such as PTN, VISFATIN, SPP1, and TGF-β, was selectively altered in Osteoarthritis. Moreover, we verified that SPP1 pathway enrichment scores increased, but VISFATIN pathway enrichment scores decreased based on the bulk rna-seq datasets in Osteoarthritis. Conclusion: Our results revealed alterations in cell-cell communication among OA-related chondrocyte subtypes that were mediated by specific signaling pathways, which might be a crucial underlying mechanism associated with Osteoarthritis progression.

Combined single-cell RNA-seq and bulk RNA-seq to analyze the expression and role of TREM2 in bladder cancer

Currently, reprogramming macrophages has emerged as one of the most promising therapeutic strategies in cancer treatment. Many studies have found that myeloid trigger receptor-2 (TREM2) is mainly expressed on tumor-associated macrophages (TAMs), and targeting TREM2 promotes reprogramming of TAMs and enhances the immunotherapeutic effect of tumors. Nevertheless, the expression and role of TREM2 in different tumor tissues are still controversial. For example, some studies have found that TREM2 can also be expressed on tumor cells and exert pro-tumor functions. It has also been found that TREM2 expression can inhibit tumorigenesis and progression. In fact, there are still no relevant studies on the expression and role of TREM2 in bladder cancer (BLCA). Therefore, the present study combined single-cell RNA-seq and bulk RNA-seq to analyze the expression, role, and molecular mechanism of TREM2 in BLCA. We found that TREM2 was predominantly expressed on TAMs in BLCA, followed by tumor epithelial cells. This finding could be useful for further exploration of the role and mechanism of TREM2. Moreover, TREM2 expression correlates with clinical progression and immunotherapy efficacy, and is an important predictor of prognosis for BLCA patients. Not only that, we also found that TREM2 may exert its effects by promoting epithelial mesenchymal transition (EMT) and T-cell exhaustion. TREM2⁺ TAMs may play an important pro-tumor role through PTN, ANGPTL, and VISFATIN pathways. In conclusion, our study found that TREM2 is not only a predictor of BLCA prognosis, but also a potential therapeutic target for BLCA.

Proteomic Analysis of Pleural Effusions from COVID-19 Deceased Patients: Enhanced Inflammatory Markers

Critically ill COVID-19 patients with pleural effusion experience longer hospitalization, multisystem inflammatory syndrome, and higher rates of mortality. Generally, pleural effusion can serve as a diagnostic value to differentiate cytokine levels. This study aimed to evaluate the pleural effusions of COVID-19 deceased patients for 182 protein markers. Olink^® Inflammation and Organ Damage panels were used to determine the level of 184 protein markers, e.g., ADA, BTC, CA12, CAPG, CD40, CDCP1, CXCL9, ENTPD2, Flt3L, IL-6, IL-8, LRP1, OSM, PD-L1, PTN, STX8, and VEGFA, which were raised significantly in COVID-19 deceased patients, showing over-stimulation of the immune system and ravaging cytokine storm. The rises of DPP6 and EDIL3 also indicate damage caused to arterial and cardiovascular organs. Overall, this study confirms the elevated levels of CA12, CD40, IL-6, IL-8, PD-L1, and VEGFA, proposing their potential either as biomarkers for the severity and prognosis of the disease or as targets for therapy. Particularly, this study reports upregulated ADA, BTC, DPP6, EDIL3, LIF, ENTPD2, Flt3L, and LRP1 in severe COVID-19 patients for the first time. Pearson's correlation coefficient analysis indicates the involvement of JAK/STAT pathways as a core regulator of hyperinflammation in deceased COVID-19 patients, suggesting the application of JAK inhibitors as a potential efficient treatment.

Multiplex protein profiling of bronchial aspirates reveals disease-, mortality- and respiratory sequelae-associated signatures in critically ill patients with ARDS secondary to SARS-CoV-2 infection

Introduction

Bronchial aspirates (BAS) obtained during invasive mechanical ventilation (IMV) constitutes a useful tool for molecular phenotyping and decision making.

Aim

To identify the proteomic determinants associated with disease pathogenesis, all-cause mortality and respiratory sequelae in BAS samples from critically ill patients with SARS-CoV-2-induced ARDS.

Methods

Multicenter study including 74 critically ill patients with COVID-19 and non-COVID-19 ARDS. BAS were obtained by bronchoaspiration after IMV initiation. Three hundred sixty-four proteins were quantified using proximity extension assay (PEA) technology. Random forest models were used to assess predictor importance.

Results

After adjusting for confounding factors, CST5, NADK, SRPK2 and TGF-α were differentially detected in COVID-19 and non-COVID-19 patients. In random forest models for COVID-19, CST5, DPP7, NADK, KYAT1 and TYMP showed the highest variable importance. In COVID-19 patients, reduced levels of ENTPD2 and PTN were observed in nonsurvivors of ICU stay, even after adjustment. AGR2, NQO2, IL-1α, OSM and TRAIL showed the strongest associations with in-ICU mortality and were used to construct a protein-based prediction model. Kaplan-Meier curves revealed a clear separation in mortality risk between subgroups of PTN, ENTPD2 and the prediction model. Cox regression models supported these findings. In survivors, the levels of FCRL1, NTF4 and THOP1 in BAS samples obtained during the ICU stay correlated with lung function (i.e., D_LCO levels) 3 months after hospital discharge. Similarly, Flt3L and THOP1 levels were correlated with radiological features (i.e., TSS). These proteins are expressed in immune and nonimmune lung cells. Poor host response to viral infectivity and an inappropriate reparative mechanism seem to be linked with the pathogenesis of the disease and fatal outcomes, respectively.

Conclusion

BAS proteomics identified novel factors associated with the pathology of SARS-CoV-2-induced ARDS and its adverse outcomes. BAS-based protein testing emerges as a novel tool for risk assessment in the ICU.

Antimicrobial Proteins and Peptides in Avian Eggshell: Structural Diversity and Potential Roles in Biomineralization

The calcitic avian eggshell provides physical protection for the embryo during its development, but also regulates water and gaseous exchange, and is a calcium source for bone mineralization. The calcified eggshell has been extensively investigated in the chicken. It is characterized by an inventory of more than 900 matrix proteins. In addition to proteins involved in shell mineralization and regulation of its microstructure, the shell also contains numerous antimicrobial proteins and peptides (AMPPs) including lectin-like proteins, Bacterial Permeability Increasing/Lipopolysaccharide Binding Protein/PLUNC family proteins, defensins, antiproteases, and chelators, which contribute to the innate immune protection of the egg. In parallel, some of these proteins are thought to be crucial determinants of the eggshell texture and its resulting mechanical properties. During the progressive solubilization of the inner mineralized eggshell during embryonic development (to provide calcium to the embryo), some antimicrobials may be released simultaneously to reinforce egg defense and protect the egg from contamination by external pathogens, through a weakened eggshell. This review provides a comprehensive overview of the diversity of avian eggshell AMPPs, their three-dimensional structures and their mechanism of antimicrobial activity. The published chicken eggshell proteome databases are integrated for a comprehensive inventory of its AMPPs. Their biochemical features, potential dual function as antimicrobials and as regulators of eggshell biomineralization, and their phylogenetic evolution will be described and discussed with regard to their three-dimensional structural characteristics. Finally, the repertoire of chicken eggshell AMPPs are compared to orthologs identified in other avian and non-avian eggshells. This approach sheds light on the similarities and differences exhibited by AMPPs, depending on bird species, and leads to a better understanding of their sequential or dual role in biomineralization and innate immunity.

Single-cell RNA sequencing of the Mongolia sheep testis reveals a conserved and divergent transcriptome landscape of mammalian spermatogenesis

Spermatogenesis is a highly coordinated and complex process, and is pivotal for transmitting genetic information between mammalian generations. In this study, we investigated the conservation, differences, and biological functions of homologous genes during spermatogenesis in Mongolia sheep, humans, cynomolgus monkey, and mice using single-cell RNA sequencing technology. We compared X chromosome meiotic inactivation events in Mongolia sheep, humans, cynomolgus monkey, and mice to uncover the concerted activity of X chromosome genes. Subsequently, we focused on the dynamics of gene expression, key biological functions, and signaling pathways at various stages of spermatogenesis in Mongolia sheep and humans. Additionally, the ligand-receptor networks of Mongolia sheep and humans in testicular somatic and germ cells at different developmental stages were mapped to reveal conserved germ cell-soma communication using single-cell resolution. These datasets provided novel information and insights to unravel the molecular regulatory mechanisms of Mongolia sheep spermatogenesis and highlight conservation in gene expression during spermatogenesis between Mongolia sheep and humans, providing a foundation for the establishment of a large mammalian disease model of male infertility.

Pleiotrophin Interaction with Synthetic Glycosaminoglycan Mimetics

Chondroitin sulfate (CS) E is the natural ligand for pleiotrophin (PTN) in the central nervous system (CNS) of the embryo. Some structures of PTN in solution have been solved, but no precise location of the binding site has been reported yet. Using ¹⁵N-labelled PTN and HSQC NMR experiments, we studied the interactions with a synthetic CS-E tetrasaccharide corresponding to the minimum binding sequence. The results agree with the data for larger GAG (glycosaminoglycans) sequences and confirm our hypothesis that a synthetic tetrasaccharide is long enough to fully interact with PTN. We hypothesize that the central region of PTN is an intrinsically disordered region (IDR) and could modify its properties upon binding. The second tetrasaccharide has two benzyl groups and shows similar effects on PTN. Finally, the last measured compound aggregated but beforehand, showed a behavior compatible with a slow exchange in the NMR time scale. We propose the same binding site and mode for the tetrasaccharides with and without benzyl groups.

Molecular Mechanisms and Clinical Challenges of Glioma Invasion

Glioma is the most common primary brain tumor, and its prognosis is poor. Glioma cells are highly invasive to the brain parenchyma. It is difficult to achieve complete resection due to the nature of the brain tissue, and tumors that invade the parenchyma often recur. The invasiveness of tumor cells has been studied from various aspects, and the related molecular mechanisms are gradually becoming clear. Cell adhesion factors and extracellular matrix factors have a strong influence on glioma invasion. The molecular mechanisms that enhance the invasiveness of glioma stem cells, which have been investigated in recent years, have also been clarified. In addition, it has been discussed from both basic and clinical perspectives that current therapies can alter the invasiveness of tumors, and there is a need to develop therapeutic approaches to glioma invasion in the future. In this review, we will summarize the factors that influence the invasiveness of glioma based on the environment of tumor cells and tissues, and describe the impact of the treatment of glioma on invasion in terms of molecular biology, and the novel therapies for invasion that are currently being developed.

Astrocyte-Derived Pleiotrophin Mitigates Late-Stage Autoimmune CNS Inflammation

Astrocytes are the most abundant glial cells in the central nervous system (CNS) with the capacity to sense and react to injury and inflammatory events. While it has been widely documented that astrocytes can exert tissue-degenerative functions, less is known about their protective and disease-limiting roles. Here, we report the upregulation of pleiotrophin (PTN) by mouse and human astrocytes in multiple sclerosis (MS) and its preclinical model experimental autoimmune encephalomyelitis (EAE). Using CRISPR-Cas9-based genetic perturbation systems, we demonstrate in vivo that astrocyte-derived PTN is critical for the recovery phase of EAE and limits chronic CNS inflammation. PTN reduces pro-inflammatory signaling in astrocytes and microglia and promotes neuronal survival following inflammatory challenge. Finally, we show that intranasal administration of PTN during the late phase of EAE successfully reduces disease severity, making it a potential therapeutic candidate for the treatment of progressive MS, for which existing therapies are limited.

Primary angle closure glaucoma is characterized by altered extracellular matrix homeostasis in the iris

PURPOSE

To characterize the proteome of the iris in primary angle closure glaucoma (PACG).

EXPERIMENTAL DESIGN

In this cross-sectional study, iris samples were obtained from surgical iridectomy of 48 adults with PACG and five normal controls. Peptides from iris were analysed using liquid chromatography-tandem mass spectrometry on an Orbitrap Q Exactive Plus mass spectrometer. Verification of proteins of interest was conducted using selected reaction monitoring on a triple quadrupole mass spectrometer. The main outcome was proteins with a log₂ two-fold difference in expression in iris between PACG and controls.

RESULTS

There were 3,446 non-redundant proteins identified in human iris, of which 416 proteins were upregulated and 251 proteins were downregulated in PACG compared with controls. Thirty-two upregulated proteins were either components of the extracellular matrix (ECM) (fibrillar collagens, EMILIN-2, fibrinogen, fibronectin, matrilin-2), matricellular proteins (thrombospondin-1), proteins involved in cell-matrix interactions (integrins, laminin, histidine-rich glycoprotein, paxillin), or protease inhibitors known to modulate ECM turnover (α-2 macroglobulin, tissue factor pathway inhibitor 2, papilin). Two giant proteins, titin and obscurin, were up- and down-regulated, respectively, in the iris in PACG compared with controls.

CONCLUSIONS AND CLINICAL RELEVANCE

This proteomic study shows that ECM composition and homeostasis are altered in the iris in PACG.

Pleiotrophin serum level is increased in Relapsing-Remitting Multiple Sclerosis and correlates with sex, BMI and treatment

BACKGROUND

Multiple Sclerosis (MS) is an immune-mediated demyelinating disease mainly affecting the Central Nervous System (CNS). 80% of MS patients present the Relapsing-Remitting form (RRMS). Pleiotrophin (PTN), a cytokine previously associated with other autoimmune and neurological diseases, could play a role in the pathophysiology of RRMS due to its neuro and immunomodulatory effect. However, PTN has never been explored in RRMS patients.

AIM OF THE STUDY

To determine PTN serum levels in patients with RRMS, treated with Glatiramer acetate (GA) or Interferon-beta (IFN-β), as well as in non-treated patients and healthy controls as a first attempt to explore PTN in RRMS.

METHODS

PTN serum levels were quantified by ELISA in 57 patients and 18 controls.

RESULTS

We demonstrated that PTN serum levels are significantly higher in RRMS patients. In IFN-β treated patients alone, PTN correlated positively with time of disease evolution and time of IFN-β use and correlated negatively with the MS severity score (MSSS). When comparing groups according to weight status, we observed that PTN is statistically increased in overweight female patients and that weight does not affect male patients. The Area Under the Curve (AUC) of the Receiver Operating Characteristic (ROC) curve analysis was higher for males compared to females.

CONCLUSION

PTN serum level is higher in RRMS patients and that is associated with sex, BMI and IFN-β treatment. Therefore, we propose that PTN could be playing a role in MS. Further studies must be performed to identify the exact role of PTN in this pathology.