The heparin-binding growth factor midkine: the biological activities and candidate receptors

Midkine is upregulated in the hippocampus following both spatial and olfactory reward association learning and enhances memory

Hippocampal neuronal plasticity is a fundamental process underpinning learning and memory formation and requiring elaborate molecular mechanisms that result in the dynamic remodelling of synaptic connectivity. The neurotrophic properties of midkine (Mdk) have been implicated in the development and repair of the nervous system, while Mdk knockout resulted in deficits in the formation of certain types of memory. The role of Mdk in the process of memory-associated neuronal plasticity, however, remains poorly understood. We investigated the learning-induced regulation of Mdk in spatial navigation and association learning using the water maze and the odour reward association learning paradigms, characterising a temporal profile of Mdk protein expression post-learning. Both learning events revealed similar patterns of upregulation of expression of the protein in the rat hippocampal dentate gyrus, which were rapid and transient. Moreover, administration of recombinant Mdk during the endogenous Mdk upregulation following learning enhanced memory in the water maze task revealing a pro-cognitive action of Mdk. We further show that, within the adult hippocampus, Mdk mRNA is predominantly expressed in granular and pyramidal neurons and that hippocampal neuronal Mdk expression is regulated by the canonical plasticity-associated neurotransmitter glutamate. Finally, we confirm that the positive action of Mdk on neurite outgrowth previously noted in cortical and cerebellar neurons extends to hippocampal neurons. Together, our findings suggest a role for Mdk in glutamate-mediated hippocampal neuronal plasticity important for long-term memory consolidation.

Spatiotemporal transcriptomic changes of human ovarian aging and the regulatory role of FOXP1

Limited understanding exists regarding how aging impacts the cellular and molecular aspects of the human ovary. This study combines single-cell RNA sequencing and spatial transcriptomics to systematically characterize human ovarian aging. Spatiotemporal molecular signatures of the eight types of ovarian cells during aging are observed. An analysis of age-associated changes in gene expression reveals that DNA damage response may be a key biological pathway in oocyte aging. Three granulosa cells subtypes and five theca and stromal cells subtypes, as well as their spatiotemporal transcriptomics changes during aging, are identified. FOXP1 emerges as a regulator of ovarian aging, declining with age and inhibiting CDKN1A transcription. Silencing FOXP1 results in premature ovarian insufficiency in mice. These findings offer a comprehensive understanding of spatiotemporal variability in human ovarian aging, aiding the prioritization of potential diagnostic biomarkers and therapeutic strategies.

Exploration of neuron heterogeneity in human heart failure with dilated cardiomyopathy through single-cell RNA sequencing analysis

OBJECTIVE

We aimed to explore the heterogeneity of neurons in heart failure with dilated cardiomyopathy (DCM).

METHODS

Single-cell RNA sequencing (scRNA-seq) data of patients with DCM and chronic heart failure and healthy samples from GSE183852 dataset were downloaded from NCBI Gene Expression Omnibus, in which neuron data were extracted for investigation. Cell clustering analysis, differential expression analysis, trajectory analysis, and cell communication analysis were performed, and highly expressed genes in neurons from patients were used to construct a protein-protein interaction (PPI) network and validated by GSE120895 dataset.

RESULTS

Neurons were divided into six subclusters involved in various biological processes and each subcluster owned its specific cell communication pathways. Neurons were differentiated into two branches along the pseudotime, one of which was differentiated into mature neurons, whereas another tended to be involved in the immune and inflammation response. Genes exhibited branch-specific differential expression patterns. FLNA, ITGA6, ITGA1, and MDK interacted more with other gene-product proteins in the PPI network. The differential expression of FLNA between DCM and control was validated.

CONCLUSION

Neurons have significant heterogeneity in heart failure with DCM, and may be involved in the immune and inflammation response to heart failure.

Elevated Midkine Serum Levels Are Associated with Long-Term Survival in Critically Ill Patients

Midkine (Mdk) is a multifunctional protein involved in inflammatory processes. Hence, circulating Mdk is increased in sepsis and has been previously suggested as a potential biomarker in these patients. The aim of this study was to elucidate the role of Mdk serum concentrations in critical illness and sepsis and to verify its value as a prognostic biomarker. Thus, we analyzed the Mdk serum concentrations of 192 critically ill patients on admission to the medical intensive care unit (ICU). While the serum levels of Mdk at admission were similar in septic and nonseptic critical illness (362 vs. 337 ng/L, p = 0.727), we found several interesting correlations of Mdk to laboratory and clinical markers associated with ischemia or hypoxia, e.g., to renal failure and hepatic injury. Mdk serum concentrations at admission did not differ between various causes of sepsis or other critical illness. Most noticeable, we observed upregulated Mdk serum concentrations at admission in patients surviving in the long-term, which was only seen in nonseptic critical illness but not in sepsis. Our study suggests a relevant role of Mdk in critically ill patients in general and highlights the possible protective features of Mdk in critical illness.

The role of midkine in health and disease

Midkine (MDK) is a neurotrophic growth factor highly expressed during embryogenesis with important functions related to growth, proliferation, survival, migration, angiogenesis, reproduction, and repair. Recent research has indicated that MDK functions as a key player in autoimmune disorders of the central nervous system (CNS), such as Multiple Sclerosis (MS) and is a promising therapeutic target for the treatment of brain tumors, acute injuries, and other CNS disorders. This review summarizes the modes of action and immunological functions of MDK both in the peripheral immune compartment and in the CNS, particularly in the context of traumatic brain injury, brain tumors, neuroinflammation, and neurodegeneration. Moreover, we discuss the role of MDK as a central mediator of neuro-immune crosstalk, focusing on the interactions between CNS-infiltrating and -resident cells such as astrocytes, microglia, and oligodendrocytes. Finally, we highlight the therapeutic potential of MDK and discuss potential therapeutic approaches for the treatment of neurological disorders.

Prognosis of Midkine and AT1R expression in resectable head and neck squamous cell carcinoma

BACKGROUND

Research studies have demonstrated that Midkine (MDK) can influence the expression and activity of Renin-angiotensin system (RAS) components. Angiotensin II is involved in tumor growth and angiogenesis in different cancers. We previously observed Angiotensin II receptor blockers (ARBs) improve the survival rates of patients with oral cancers. These findings have prompted us to investigate whether MDK can influence the RAS pathway, mainly through its association with angiotensin II type 1 receptor (AT1R), which contributes to the observed poor prognosis in head and neck squamous cell carcinoma (HNSCC) patients.

METHODS

MDK and AT1R expressions were examined in 150 HNSCC patients post-operation by immunohistochemical staining between 1 January 2010 and 31 December 2016. We tested the over-expression and silencing of MDK to evaluate the AT1R expression and functional biological assays in HNSCC cell lines HSC-3 and SAS.

RESULTS

Positive expression of MDK is correlated with positive AT1R expression. MDK predicted poor NSCC patients' survival. Silencing MDK could suppress AT1R and pAKT expression and reduce the growth, migration, and invasion of HNSCC cells. ARB also inhibits MDK stimulating HNSCC cell proliferation. Overexpression of MDK could upregulate AT1R and pAKT.

CONCLUSIONS

MDK is an independent prognostic factor of HNSCC post-operation, and AT1R regulates HNSCC cell growth, invasion, and migration. Positive MDK and AT1R expressions are highly correlated. Mechanistically, the interaction between MDK and AT1R is crucial for MDK-mediated cell viability, and inhibiting AT1R can effectively counteract or abolish these effects. Furthermore, MDK exerts a regulatory role in the expression of AT1R, as well as in the growth and motility of HNSCC cells. These findings highlight the involvement of the interaction between MDK, AT1R, and the pAkt signaling pathways in HNSCC cell viability growth.

The Glycosaminoglycan Side Chains and Modular Core Proteins of Heparan Sulphate Proteoglycans and the Varied Ways They Provide Tissue Protection by Regulating Physiological Processes and Cellular Behaviour

This review examines the roles of HS-proteoglycans (HS-PGs) in general, and, in particular, perlecan and syndecan as representative examples and their interactive ligands, which regulate physiological processes and cellular behavior in health and disease. HS-PGs are essential for the functional properties of tissues both in development and in the extracellular matrix (ECM) remodeling that occurs in response to trauma or disease. HS-PGs interact with a biodiverse range of chemokines, chemokine receptors, protease inhibitors, and growth factors in immune regulation, inflammation, ECM stabilization, and tissue protection. Some cell regulatory proteoglycan receptors are dually modified hybrid HS/CS proteoglycans (betaglycan, CD47). Neurexins provide synaptic stabilization, plasticity, and specificity of interaction, promoting neurotransduction, neurogenesis, and differentiation. Ternary complexes of glypican-1 and Robbo-Slit neuroregulatory proteins direct axonogenesis and neural network formation. Specific neurexin-neuroligin complexes stabilize synaptic interactions and neural activity. Disruption in these interactions leads to neurological deficits in disorders of functional cognitive decline. Interactions with HS-PGs also promote or inhibit tumor development. Thus, HS-PGs have complex and diverse regulatory roles in the physiological processes that regulate cellular behavior and the functional properties of normal and pathological tissues. Specialized HS-PGs, such as the neurexins, pikachurin, and Eyes-shut, provide synaptic stabilization and specificity of neural transduction and also stabilize the axenome primary cilium of phototoreceptors and ribbon synapse interactions with bipolar neurons of retinal neural networks, which are essential in ocular vision. Pikachurin and Eyes-Shut interactions with an α-dystroglycan stabilize the photoreceptor synapse. Novel regulatory roles for HS-PGs controlling cell behavior and tissue function are expected to continue to be uncovered in this fascinating class of proteoglycan.

Can maternal serum midkine level predict chorionicity in twin pregnancies?

Sometimes it can be difficult to chorionicity determination in twin pregnancies. This study aimed to compare maternal serum midkine levels between twin and singleton pregnancies. We also evaluated the relationship between chorionicity and maternal serum midkine level in twin pregnancies. The present prospective cohort study included 16 patients with monochorionic diamniotic twin pregnancies, 38 with dichorionic diamniotic twin pregnancies, and 66 healthy singleton pregnancies admitted to Ankara City Hospital Perinatology Clinic between June 2021 and June 2022. Demographic features, clinical characteristics, and serum midkine levels were compared between the groups. Additionally, a receiver operator characteristics (ROC) analysis was performed to assess the performance of midkine for detecting chorionicity. The median maternal serum midkine level was found to be 0.64 ng/ml in twin pregnancies and 0.26 ng/ml in singleton pregnancies (p < 0.001). When twin pregnancies were compared in terms of chorionicity, serum midkine level was determined as 1.20 ng/ml in the monochorionic diamniotic group and 0.50 ng/ml in the dichorionic diamniotic group (p = 0.034). An optimal cut-off value of 1.03 ng/ml was found for the determination of chorionicity (AUC: 0.68, p = 0.03, 95% CI: 0.53-0.83, %56.3 sensitivity, 76.3% specificity). In advanced weeks of pregnancy, biomarkers can be used as helpful parameters for ultrasonography in the diagnosis of twin pregnancies. Maternal serum midkine levels might be used to determine chorionicity in equivocal cases.

Intercellular crosstalk in adult dental pulp is mediated by heparin-binding growth factors Pleiotrophin and Midkine

BACKGROUND

In-depth knowledge of the cellular and molecular composition of dental pulp (DP) and the crosstalk between DP cells that drive tissue homeostasis are not well understood. To address these questions, we performed a comparative analysis of publicly available single-cell transcriptomes of healthy adult human DP to 5 other reference tissues: peripheral blood mononuclear cells, bone marrow, adipose tissue, lung, and skin.

RESULTS

Our analysis revealed that DP resident cells have a unique gene expression profile when compared to the reference tissues, and that DP fibroblasts are the main cell type contributing to this expression profile. Genes coding for pleiotrophin (PTN) and midkine (MDK), homologous heparin-binding growth-factors, possessed the highest differential expression levels in DP fibroblasts. In addition, we identified extensive crosstalk between DP fibroblasts and several other DP resident cells, including Schwann cells, mesenchymal stem cells and odontoblasts, mediated by PTN and MDK.

CONCLUSIONS

DP fibroblasts emerge as unappreciated players in DP homeostasis, mainly through their crosstalk with glial cells. These findings suggest that fibroblast-derived growth factors possess major regulatory functions and thus have a potential role as dental therapeutic targets.

Environmental enrichment improves declined cognition induced by prenatal inflammatory exposure in aged CD-1 mice: Role of NGPF2 and PSD-95

INTRODUCTION

Research suggests that prenatal inflammatory exposure could accelerate age-related cognitive decline that may be resulted from neuroinflammation and synaptic dysfunction during aging. Environmental enrichment (EE) may mitigate the cognitive and synaptic deficits. Neurite growth-promoting factor 2 (NGPF2) and postsynaptic density protein 95 (PSD-95) play critical roles in neuroinflammation and synaptic function, respectively.

METHODS

We examined whether this adversity and EE exposure can cause alterations in Ngpf2 and Psd-95 expression. In this study, CD-1 mice received intraperitoneal injection of lipopolysaccharide (50 μg/kg) or normal saline from gestational days 15-17. After weaning, half of the male offspring under each treatment were exposed to EE. The Morris water maze was used to assess spatial learning and memory at 3 and 15 months of age, whereas quantitative real-time polymerase chain reaction and Western blotting were used to measure hippocampal mRNA and protein levels of NGPF2 and PSD-95, respectively. Meanwhile, serum levels of IL-6, IL-1β, and TNF-α were determined by enzyme-linked immunosorbent assay.

RESULTS

The results showed that aged mice exhibited poor spatial learning and memory ability, elevated NGPF2 mRNA and protein levels, and decreased PSD-95 mRNA and protein levels relative to their young counterparts during natural aging. Embryonic inflammatory exposure accelerated age-related changes in spatial cognition, and in Ngpf2 and Psd-95 expression. Additionally, the levels of Ngpf2 and Psd-95 products were significantly positively and negatively correlated with cognitive dysfunction, respectively, particularly in prenatal inflammation-exposed aged mice. Changes in serum levels of IL-6, IL-1β, and TNF-α reflective of systemic inflammation and their correlation with cognitive decline during accelerated aging were similar to those of hippocampal NGPF2. EE exposure could partially restore the accelerated decline in age-related cognitive function and in Psd-95 expression, especially in aged mice.

DISCUSSION

Overall, the aggravated cognitive disabilities in aged mice may be related to the alterations in Ngpf2 and Psd-95 expression and in systemic state of inflammation due to prenatal inflammatory exposure, and long-term EE exposure may ameliorate this cognitive impairment by upregulating Psd-95 expression.

LABAMPsGCN: A framework for identifying lactic acid bacteria antimicrobial peptides based on graph convolutional neural network

Lactic acid bacteria antimicrobial peptides (LABAMPs) are a class of active polypeptide produced during the metabolic process of lactic acid bacteria, which can inhibit or kill pathogenic bacteria or spoilage bacteria in food. LABAMPs have broad application in important practical fields closely related to human beings, such as food production, efficient agricultural planting, and so on. However, screening for antimicrobial peptides by biological experiment researchers is time-consuming and laborious. Therefore, it is urgent to develop a model to predict LABAMPs. In this work, we design a graph convolutional neural network framework for identifying of LABAMPs. We build heterogeneous graph based on amino acids, tripeptide and their relationships and learn weights of a graph convolutional network (GCN). Our GCN iteratively completes the learning of embedded words and sequence weights in the graph under the supervision of inputting sequence labels. We applied 10-fold cross-validation experiment to two training datasets and acquired accuracy of 0.9163 and 0.9379 respectively. They are higher that of other machine learning and GNN algorithms. In an independent test dataset, accuracy of two datasets is 0.9130 and 0.9291, which are 1.08% and 1.57% higher than the best methods of other online webservers.

Midkine promotes metastasis and therapeutic resistance via mTOR/RPS6 in uveal melanoma

Uveal melanoma is a rare form of melanoma that originates in the eye, exerts widespread therapeutic resistance and displays an inherent propensity for hepatic metastases. Since metastatic disease is characterized by poor survival, there is an unmet clinical need to identify new therapeutic targets in uveal melanoma. Here, we show that the pleiotropic cytokine midkine is expressed in uveal melanoma. Midkine expression in primary uveal melanoma significantly correlates with poor survival and is elevated in patients that develop metastatic disease. Monosomy 3 and histopathological staging parameters are associated with midkine expression. In addition, we demonstrate that midkine promotes survival, migration across a barrier of hepatic sinusoid endothelial cells and resistance to AKT/mTOR inhibition. Furthermore, midkine is secreted and mediates mTOR activation by maintaining phosphorylation of the mTOR target RPS6 in uveal melanoma cells. Therefore, midkine is identified as a uveal melanoma cell survival factor that drives metastasis and therapeutic resistance, and could be exploited as a biomarker as well as a new therapeutic target. Implications: Midkine is identified as a survival factor that drives liver metastasis and therapeutic resistance in melanoma of the eye.

Midkine noncanonically suppresses AMPK activation through disrupting the LKB1-STRAD-Mo25 complex

Midkine (MDK), a secreted growth factor, regulates signal transduction and cancer progression by interacting with receptors, and it can be internalized into the cytoplasm by endocytosis. However, its intracellular function and signaling regulation remain unclear. Here, we show that intracellular MDK interacts with LKB1 and STRAD to disrupt the LKB1-STRAD-Mo25 complex. Consequently, MDK decreases the activity of LKB1 to dampen both the basal and stress-induced activation of AMPK by glucose starvation or treatment of 2-DG. We also found that MDK accelerates cancer cell proliferation by inhibiting the activation of the LKB1-AMPK axis. In human cancers, compared to other well-known growth factors, MDK expression is most significantly upregulated in cancers, especially in liver, kidney and breast cancers, correlating with clinical outcomes and inversely correlating with phosphorylated AMPK levels. Our study elucidates an inhibitory mechanism for AMPK activation, which is mediated by the intracellular MDK through disrupting the LKB1-STRAD-Mo25 complex.

Midkine release during hemodialysis is predictive of hypervolemia and associates with excess (cardiovascular) mortality in patients with end-stage renal disease: a prospective study

Background

In end-stage renal disease, a high cardiovascular risk profile and endothelial damage prevails. The heparin-binding growth factor midkine stimulates neo-angiogenesis in ischemic diseases, coordinates neutrophil influx, and raises blood pressure through stimulated angiotensin synthesis.

Methods

We determined changes of midkine serum levels during hemodialysis sessions under the assumption that endothelial cell-derived midkine is released. Periprocedural differences (∆midkine) were calculated and correlated with cardiovacular biomarkers and fluid status (clinical assessment, V. cava collapse, comet tail phenomenon), cardiovascular morbidities, mortality rates. Blood was collected before and after dialysis from hemodialysis patients (n = 171; diabetes: n = 70; hypervolemia: n = 83; both: n = 32).

Results

Baseline midkine levels were ~ fourfold elevated compared to healthy controls (n = 100). Further, on average a tenfold rise was detected during dialysis, the extent of which was partially related to non-fractionated heparin application (r² = 0.17). Inter-individual differences were highly reproducible. Hypervolemic patients responded with a less than average rise in midkine levels during dialysis (p < 0.02), this difference became more obvious with co-existing diabetes (p < 0.001 for long dialysis-free interval) and was confirmed in an independently enrolled dialysis cohort (n = 88). In Kaplan Meier survival curves, low delta midkine levels correlated with cardiovascular/overall mortality rates, similar to elevated uPAR levels, whereas other markers (NTproANP, galectin, tenascin-C) were less predictive. Following intervention with successful fluid removal in hypervolemic dialysis patients to optimize fluid homeostasis, midkine values increased (p < 0.002), which was not observed in patients that failed to decrease weight.

Conclusion

Thus, for dialysis patients inadequate periprocedural midkine upregulation is linked with hypervolemia and associates with cardiovascular events.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11255-022-03141-4.

Single-cell analysis reveals that cancer-associated fibroblasts stimulate oral squamous cell carcinoma invasion via the TGF-β/Smad pathway

Although substantial progress has been made in cancer biology and treatment, the prognosis of oral squamous cell carcinoma (OSCC) is still not satisfactory because of local tumor invasion and frequent lymph node metastasis. The tumor microenvironment (TME) is a potential target in which cancer-associated fibroblasts (CAFs) are of great significance due to their interactions with cancer cells. However, the exact mechanism is still unclear. Therefore, we focus on the crosstalk between cancer cells and CAFs and discover that CAFs are the main source of TGF-β1. Transwell assays and western blot analysis further prove that CAFs activate the TGF-β1/Smad pathway to promote OSCC invasion. Through survival analysis, we confirm that CAF overexpression is correlated with poor overall survival in OSCC. To further elucidate the origin and role of CAFs in OSCC, we analyze single-cell RNA sequencing (scRNA-seq) data from 14 OSCC tumor samples and identify four distinct cell types, including CAFs, in the TME, indicating high intratumoral heterogeneity. Then, two subtypes of CAFs, namely, myofibroblasts (mCAFs) and inflammatory CAFs (iCAFs), are further distinguished. Based on the differentially upregulated genes of mCAFs and iCAFs, GO enrichment analysis reveals their different roles in OSCC progression. Furthermore, the gene expression pattern is dynamically altered across pseudotime, potentially taking part in the transformation from epithelial to mCAFs or iCAFs through the epithelial to mesenchymal transition.

Heparin and Derivatives for Advanced Cell Therapies

Heparin and its derivatives are saving thousands of human lives annually, by successfully preventing and treating thromboembolic events. Although the mode of action during anticoagulation is well studied, their influence on cell behavior is not fully understood as is the risk of bleeding and other side effects. New applications in regenerative medicine have evolved supporting production of cell-based therapeutics or as a substrate for creating functionalized matrices in biotechnology. The currently resurgent interest in heparins is related to the expected combined anti-inflammatory, anti-thrombotic and anti-viral action against COVID-19. Based on a concise summary of key biochemical and clinical data, this review summarizes the impact for manufacturing and application of cell therapeutics and highlights the need for discriminating the different heparins.

Diagnostic performance of Midkine ratios in fine-needle aspirates for evaluation of Cytologically indeterminate thyroid nodules

Background

Fine-needle aspiration cytology (FNAC) is a basic diagnostic tool for thyroid nodules. However, 15–30% of nodules are cytologically indeterminate. Midkine (MK), a pleiotropic growth factor, is often upregulated in patients with cancers. This study aimed to evaluate the role of MK and its ratios in fine-needle aspirates (FNA) for predicting thyroid malignancy.

Methods

This retrospective study included patients with thyroid nodules who underwent preoperative FNA and/or thyroidectomy between April 2017 and September 2017. MK levels in FNA washout were measured by enzyme-linked immunosorbent assay, and thyroglobulin (TG) and free thyroxine (FT4) levels in FNA washout were measured by chemiluminescent immunometric assays.

Results

A total of 217 patients with 242 nodules were included in this study. The concentrations of TG, FT4, MK/TG, MK/FT4, and FT4/MK were significantly different between papillary thyroid carcinomas and benign thyroid nodules. Both MK/TG and MK/FT4 ratios were positively correlated with maximum tumor diameter, extrathyroidal extension, and T and N stages. The area under the curve for MK/TG was 0.719 with a cutoff value of 55.57 ng/mg, while the area under the curve for MK/FT4 was 0.677 with a cutoff value of 0.11 μg/pmol. FNAC in combination with MK/FT4 had a higher sensitivity (95% vs. 91%) and accuracy (96% vs. 92%) than FNAC alone for cytologically indeterminate specimens, those of unknown significance, or those suspected of malignancy.

Conclusions

MK/FT4 and MK/TG may have diagnostic utility for evaluation of papillary thyroid carcinomas, particularly for cytologically indeterminate thyroid nodules.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13000-021-01150-y.

Screening of novel Midkine binding protein by BioID2-based proximity labeling

Midkine (MK), a heparin-binding growth factor, is associated with the poor prognosis of the pediatric tumor, neuroblastoma. MK would be a druggable target as many studies showed inhibition of its function in various cancers suppressed tumor developments. To establish the therapy targeting MK, identification of its binding partners, and elucidation of its intracellular signaling are needed. It was reported that exogenous MK induced phosphorylation of ribosomal protein S6 (RPS6) downstream of mTOR signaling. Using RPS6 phosphorylation as a marker of MK response, we searched for MK reactive cell lines. We found that MK cell lines expressing less MK tended to respond better to MK. Next, using an MK reactive neuroblastoma cell line, MK-knocked down SH-SY5Y cells, we employed a proximity-dependent biotin identification method, which was invented to evaluate protein-protein interactions by biotinylation. We confirmed that secreted MK fused to the biotin ligase BioID2 (MK-BioID2) was able to biotinylate proteins from the cells. Biotinylated proteins were identified by liquid chromatography-mass spectrometry analyses. Twenty five proteins were found to be overlapped after three independent experiments, among which insulin-like growth binding protein 2 (IGFBP2) was further analyzed. IGFBP2 was indeed detected with immunoblotting after streptavidin pull down of MK-BioID2 labeled cell extract of MK-knocked down SH-SY5Y cells. Our study suggests that the BioID2 method is useful to identify binding partners of growth factors.

Midkine Interaction with Chondroitin Sulfate Model Synthetic Tetrasaccharides and Their Mimetics: The Role of Aromatic Interactions

Midkine (MK) is a neurotrophic factor that participates in the embryonic central nervous system (CNS) development and neural stem cell regulation, interacting with sulfated glycosaminoglycans (GAGs). Chondroitin sulfate (CS) is the natural ligand in the CNS. In this work, we describe the interactions between a library of synthetic models of CS-types and mimics. We did a structural study of this library by NMR and MD (Molecular Dynamics), concluding that the basic shape is controlled by similar geometry of the glycosidic linkages. Their 3D structures are a helix with four residues per turn, almost linear. We have studied the tetrasaccharide-midkine complexes by ligand observed NMR techniques and concluded that the shape of the ligands does not change upon binding. The ligand orientation into the complex is very variable. It is placed inside the central cavity of MK formed by the two structured beta-sheets domains linked by an intrinsically disordered region (IDR). Docking analysis confirmed the participation of aromatics residues from MK completed with electrostatic interactions. Finally, we test the biological activity by increasing the MK expression using CS tetrasaccharides and their capacity in enhancing the growth stimulation effect of MK in NIH3T3 cells.

Midkine: Utility as a Predictor of Early Diabetic Nephropathy in Children with Type 1 Diabetes Mellitus

Objective

This study aimed to assess the role of serum midkine (MK) as a biomarker for early detection of diabetic nephropathy in children with type 1 diabetes mellitus (T1DM) before microalbuminuria emerges.

Methods

A total of 120 children with T1DM, comprising 60 microalbuminuric patients (Group 1), 60 normoalbuminuric patients (Group 2), and 60 healthy participants as a control group (Group 3) were included. Detailed medical history, clinical examination, and laboratory assessment of high-sensitivity C-reactive protein (hs-CRP), hemoglobin A1c percentage (HbA1c%), lipid profile, urinary albumin to creatinine ratio (ACR), serum MK and estimated glomerular filtration rate based on serum creatinine were performed in all participants.

Results

Both Group 1 and Group 2 had significantly higher serum MK compared to controls (p<0.001). Additionally, significantly higher MK concentrations were present in Group 1 compared with Group 2 (p<0.001). Receiver operating characteristic curve analysis revealed that the MK concentration cutoff value of 1512 pg/mL was able to predict microalbuminuria with a sensitivity of 96% and specificity of 92%. Stepwise regression analysis revealed that HbA1c%, hs-CRP, and ACR were independently related to MK levels (p<0.001 for each).

Conclusion

The results of this study suggest that serum MK is a useful, novel, practical marker for the evaluation of renal involvement in children with T1DM, especially in normoalbuminuric children.

Midkine: A multifaceted driver of atherosclerosis

Atherosclerosis constitutes the pathological basis of life-threatening events, including heart attack and stroke. Midkine is a heparin-binding growth factor and forms a small protein family with pleiotrophin. Under inflammatory or hypoxic conditions, midkine expression is up-regulated. Upon binding to its receptors, midkine can activate multiple signal pathways to regulate cell survival and migration, epithelial-to-mesenchymal transition, and oncogenesis. Circulating midkine levels are significantly increased in patients with essential hypertension, obesity or severe peripheral artery disease. Importantly, midkine exerts a proatherogenic effect by altering multiple pathophysiological processes involving atherogenesis, including macrophage lipid accumulation, vascular inflammation, neointima formation, insulin resistance and macrophage apoptosis. Midkine represents a potential therapeutic target for atherosclerosis-associated diseases. This review described the structure characteristics, expression patterns and signal transduction pathways of midkine with an emphasis on its role in atherosclerosis.

Synthesis, structure and midkine binding of chondroitin sulfate oligosaccharide analogues

The preparation of chondroitin sulfate (CS) oligosaccharide mimetics, more easily synthesized than natural sequences, is a highly interesting task because these compounds pave the way for modulation of the biological processes in which CS is involved. Herein, we report the synthesis of CS type E analogues which present easily accessible glucose units instead of glucuronic acid (GlcA) moieties. NMR experiments and molecular dynamics simulations showed that the 3D structure of these compounds is similar to the structure of the natural CS-E oligosaccharides. In addition, fluorescence polarization (FP) and saturation transfer difference NMR (STD-NMR) experiments revealed that the synthesized CS-like derivatives were able to interact with midkine, a model heparin-binding growth factor, suggesting that the presence of the GlcA carboxylate groups is not essential for the binding. Overall, our results indicate that the synthesized glucose-containing oligosaccharides can be considered as functional and structural CS mimetics.

Experimental agents to improve fracture healing: utilizing the WNT signaling pathway

The process of bone healing largely recapitulates bone development in the embryo and ideally achieves complete restoration of bone shape and structure. However, because successful fracture healing requires tight interactions of numerous cell types and signaling molecules, any disruption of this highly coordinated processes can result in delayed healing or even non-union formation. The rate of fracture healing complications in orthopedic patients is reported to be 5-20%. Therefore, there is a need for new therapeutic strategies to improve fracture healing in patients with healing complications. One treatment strategy would include the easy and safe application of a pharmacological agent inducing osteoanabolic effects during fracture healing. One potential promising molecular target is the osteoanabolic WNT signaling pathway. This pathway plays an important role during embryonic bone development, homeostasis, mechanotransduction, development of osteoporosis and bone regeneration. This review focuses on preclinical studies targeting WNT signaling molecules to accelerate fracture healing. The three main investigated antagonists of the WNT signaling pathway, which can be blocked experimentally by antibodies, are Sclerostin, Dickkopf-1 and Midkine. Treating animals with antibodies against these proteins enhanced bone formation in the fracture callus. This indicates a therapeutic potential for these antibodies to accelerate fracture healing in patients with orthopedic complications.

Spatiotemporal single-cell RNA sequencing of developing chicken hearts identifies interplay between cellular differentiation and morphogenesis

Single-cell RNA sequencing is a powerful tool to study developmental biology but does not preserve spatial information about tissue morphology and cellular interactions. Here, we combine single-cell and spatial transcriptomics with algorithms for data integration to study the development of the chicken heart from the early to late four-chambered heart stage. We create a census of the diverse cellular lineages in developing hearts, their spatial organization, and their interactions during development. Spatial mapping of differentiation transitions in cardiac lineages defines transcriptional differences between epithelial and mesenchymal cells within the epicardial lineage. Using spatially resolved expression analysis, we identify anatomically restricted expression programs, including expression of genes implicated in congenital heart disease. Last, we discover a persistent enrichment of the small, secreted peptide, thymosin beta-4, throughout coronary vascular development. Overall, our study identifies an intricate interplay between cellular differentiation and morphogenesis.

Physiology of Midkine and Its Potential Pathophysiological Role in COVID-19

SARS-CoV2 infection not only causes abnormal severe pneumonia but also induces other relevant pathophysiological effects on several tissues and organs. In this regard, the clinical complications observed in COVID-19 include acute coronary syndrome, pulmonary thromboembolism, myocarditis and, in the severe cases, the occurrence of disseminated intravascular coagulation. Literature on COVID-19 highlighted the central role of the Renin Angiotensin Aldosterone System in the determinism of SARS-CoV2 cellular internalization in the target tissues. Lung degeneration and respiratory distress appear to be dependent on the perturbance of physiological mechanisms, such as the uncontrolled release of pro-inflammatory cytokines, a dysregulation of the fibrinolytic coagulative cascade and the hyperactivation of immune effector cells. In this mini review, we address the physiology of Midkine, a growth factor able to bind heparin, and its pathophysiological potential role in COVID-19 determinism. Midkine increases in many inflammatory and autoimmune conditions and correlates with several dysfunctional immune-inflammatory responses that appear to show similarities with the pathophysiological elicited by SARS-CoV2. Midkine, together with its receptor, could facilitate the virus entry, fostering its accumulation and increasing its affinity with Ace2 receptor. We also focus on Netosis, a particular mechanism of pathogen clearance exerted by neutrophils, which under certain pathological condition becomes dysfunctional and can cause tissue damage. Moreover, we highlight the mechanism of autophagy that the new coronavirus could try to escape in order to replicate itself, as well as on pulmonary fibrosis induced by hypoxia and on the release of cytokines and mediators of inflammation, correlating the interplay between Midkine and SARS-CoV2.

PTN-PTPRZ signalling is involved in deer antler stem cell regulation during tissue regeneration

A growing deer antler contains a stem cell niche that can drive endochondral bone regeneration at up to 2 cm/day. Pleiotrophin (PTN), as a multifunctional growth factor, is found highly expressed at the messenger RNA level within the active antler stem cell tissues. This study aims to map the expression patterns of PTN protein and its receptors in a growing antler and investigate the effects of PTN on antler stem cells in vitro. Immunohistochemistry was employed to localise PTN/midkine (MDK) and their functional receptors, protein tyrosine phosphatase receptor type Z (PTPRZ), anaplastic lymphoma kinase (ALK), NOTCH2, and integrin α_V β_3, on serial slides of the antler growth centre. PTN was found to be the dominantly expressed growth factor in the PTN/MDK family. High expression of PTPRZ and ALK co-localised with PTN was found suggesting a potential interaction. The high levels of PTN and PTPRZ reflected the antler stem cell activation status during the regenerative process. When antler stem cells were cultured in vitro under the normoxic condition, no PTN protein was detected and exogenous PTN did not induce differentiation or proliferation but rather stem cell maintenance. Collectively, the antler stem cell niche appears to upregulate PTN and PTPRZ in vivo, and PTN-PTPRZ signalling may be involved in regulating antler stem cell behaviour during rapid antler regeneration.

Growth Factor Midkine Aggravates Pulmonary Arterial Hypertension via Surface Nucleolin

Pulmonary arterial hypertension (PAH) is a progressive fatal disease caused by pulmonary arterial remodeling. Midkine regulates cell proliferation and migration, and it is induced by hypoxia, but its roles in pulmonary arterial remodeling remain unclear. Serum midkine levels were significantly increased in PAH patients compared with control patients. Midkine expression was increased in lungs and sera of hypoxia-induced PAH mice. Hypoxia-induced pulmonary arterial remodeling and right ventricular hypertrophy were attenuated in midkine-knockout mice. Midkine-induced proliferation and migration of pulmonary arterial smooth muscle cells (PASMC) and epidermal growth factor receptor (EGFR) signaling were significantly increased under hypoxia, which also induced cell-surface translocation of nucleolin. Nucleolin siRNA treatment suppressed midkine-induced EGFR activation in vitro, and nucleolin inhibitor AS1411 suppressed proliferation and migration of PASMC induced by midkine. Furthermore, AS1411 significantly prevented the development of PAH in Sugen hypoxia rat model. Midkine plays a crucial role in PAH development through interaction with surface nucleolin. These data define a role for midkine in PAH development and suggest midkine-nucleolin-EGFR axis as a novel therapeutic target for PAH.

Saturation Transfer Difference in Characterization of Glycosaminoglycan-Protein Interactions

Novel methods in nuclear magnetic resonance (NMR) spectroscopy have recently been developed to investigate the binding properties of intermolecular complexes endowed with biomedical functions. Among these methods is the saturation transfer difference (STD), which enables the mapping of specific binding motifs of functional ligands. STD can efficiently uncover the specific and preferential binding sites of these ligands in their intermolecular complexes. This is particularly useful in the case of glycosaminoglycans (GAGs), a group of sulfated polysaccharides that play pivotal roles in various biological and pathological processes. The activity of GAGs is ultimately mediated through molecular interactions with key functional proteins, namely, GAG-binding proteins (GBPs). The quality of the GAG-GBP interactions depends on sulfation patterns, oligosaccharide length, and the composing monosaccharides of GAGs. Through STD NMR, information about the atoms of the GAG ligands involved in the complexes is provided. Here we highlight the latest achievements of the literature using STD NMR on GAG oligosaccharide-GBP complexes. Interestingly, most of the GBPs studied so far by STD NMR belong to one of the three major classes: coagulation factors, growth factors, or chemokine/cytokines. Unveiling the structural requirements of GAG ligands in bindings with their protein partners is a crucial step to understand the biochemical and medical actions of GAGs. This process is also a requirement in GAG-based drug discovery and development.

Midkine signaling maintains the self-renewal and tumorigenic capacity of glioma initiating cells

Glioblastoma (GBM) is one of the most aggressive forms of cancer. It has been proposed that the presence within these tumors of a population of cells with stem-like features termed Glioma Initiating Cells (GICs) is responsible for the relapses that take place in the patients with this disease. Targeting this cell population is therefore an issue of great therapeutic interest in neuro-oncology. We had previously found that the neurotrophic factor MIDKINE (MDK) promotes resistance to glioma cell death. The main objective of this work is therefore investigating the role of MDK in the regulation of GICs.

Methods: Assays of gene and protein expression, self-renewal capacity, autophagy and apoptosis in cultures of GICs derived from GBM samples subjected to different treatments. Analysis of the growth of GICs-derived xenografts generated in mice upon blockade of the MDK and its receptor the ALK receptor tyrosine kinase (ALK) upon exposure to different treatments.

Results: Genetic or pharmacological inhibition of MDK or ALK decreases the self-renewal and tumorigenic capacity of GICs via the autophagic degradation of the transcription factor SOX9. Blockade of the MDK/ALK axis in combination with temozolomide depletes the population of GICs in vitro and has a potent anticancer activity in xenografts derived from GICs.

Conclusions: The MDK/ALK axis regulates the self-renewal capacity of GICs by controlling the autophagic degradation of the transcription factor SOX9. Inhibition of the MDK/ALK axis may be a therapeutic strategy to target GICs in GBM patients.

Pharmacokinetics of midkine with different N-terminal structures in rats

Midkine (MK) is a heparin-binding growth factor that functions in multiple physiological processes, making it a promising drug target for treating various diseases including osteoarthritis (OA). However, the lack of pharmacokinetic studies on MK limits further clinical research. As the N-domain of MK protein appears to be more important for its stability, this study aimed to investigate the pharmacokinetic profiles of recombinant human (rh)MK with different structures at the N-terminus via different administration routes in rats and guinea pigs. A single intramuscular (IM) injection of 1 mg/kg rhMK with or without extended sequences at the N-terminus expressed by E. coli or Pichia was administered to six male SD rats. rhMK concentrations in sequential tail blood samples were measured by ELISA. rhMK without extended N-terminal sequences expressed by Pichia had a greater area under the curve (AUC), slower clearance, and longer half-life in rats following a single IM injection than those of the other rhMK proteins. The AUC values for rhMK after IM and intra-articular (IA) administration were 1523.3 ± 35.2 h × ng/mL and 872.0 ± 36.1 h × ng/mL, whereas the apparent volumes of distribution (Vd/f) were 0.184 ± 0.067 L/kg and 11.6 ± 0.8 L/kg, respectively, suggesting that rhMK was distributed more locally after IA injection than after IM injection as Vd/f magnitude gives a general idea of extent distribution in the body and higher Vd/f represents more locally distribution. rhMK concentration in the articular cartilage was markedly higher than that in serum and reached the highest level at 3 days after a single IA injection in Hartley guinea pigs. As the dose increased from 10 to 50 mg/kg, the AUC increased in a greater-than-dose-proportional manner, suggesting that rhMK exhibits non-linear pharmacokinetics in rats after a single IM injection in this dose range. These results indicated that the N-terminal structure and administration route have substantial effects on the pharmacokinetics of rhMK in rats. Furthermore, rhMK was maintained in articular cartilage with minimal diffusion into the blood following IA injection in Hartley guinea pigs, providing a foundation for clinical research on the use of rhMK for OA treatment via IA delivery.

Association of Midkine and Pleiotrophin Gene Polymorphisms With Systemic Lupus Erythematosus Susceptibility in Chinese Han Population

In a previous study, we have reported an increased plasma midkine (MK) and pleiotrophin (PTN) concentrations in patients with systemic lupus erythematosus (SLE) and the increase in MK and PTN associated with inflammatory cytokines interleukin (IL)-17 level and some clinical manifestations, suggesting the underlying association of MK and PTN with SLE. This study was conducted to investigate the association between common single-nucleotide polymorphisms (SNPs) in the MK and PTN gene and SLE susceptibility. A total of 989 subjects (496 SLE patients and 493 healthy controls) were included and genotyped for three MK SNPs and seven PTN SNPs in using improved multiple ligase detection reaction (iMLDR). Results have demonstrated no significant differences for genotype and allele frequencies in all 10 SNPs between SLE patients and healthy controls. Case-only analysis in SLE revealed that, in MK gene, the genotype frequency of AA/AG (rs35324223) was significantly lower in patients with photosensitivity than those without; the allele frequency of A/G (rs20542) was significantly higher in patients without serositis. In PTN gene, the A/G allele frequency (rs322236), C/T allele frequency, and TT/CT genotype frequency (rs6970141) showed significantly increased results in patients with immunological disorder compared to those without. Furthermore, no significant differences in plasma MK and PTN concentrations with its SNPs genotypes were found. MK and PTN SNPs showed no associations with SLE genetic susceptibility, but it may be associated with the course of this disease; further studies are needed to focus on the mechanism of MK and PTN genes in the pathogenesis of SLE.

Disruption of Midkine gene reduces traumatic brain injury through the modulation of neuroinflammation

Background

Midkine (MK) is a multifunctional cytokine found upregulated in the brain in the presence of different disorders characterized by neuroinflammation, including neurodegenerative disorders and ischemia. The neuroinflammatory response to traumatic brain injury (TBI) represents a key secondary injury factor that can result in further neuronal injury. In the present study, we investigated the role of endogenous MK in secondary injury, including neuroinflammation, immune response, and neuronal apoptosis activity, after TBI.

Methods

Wild type (Mdk^+/+) and MK gene deficient (Mdk^−/−) mice were subjected to fluid percussion injury for TBI models and compared at 3, 7, and 14 days after TBI, in terms of the following: brain tissue loss, neurological deficits, microglia response, astrocytosis, expression of proinflammatory M1 and anti-inflammatory M2 microglia/macrophage phenotype markers, and apoptotic activity.

Results

As opposed to Mdk^+/+ mice, Mdk^−/− mice reported a significantly reduced area of brain tissue loss and an improvement in their neurological deficits. The ratios of the Iba1-immunoreactive microglia/macrophages in the perilesional site were significantly decreased in Mdk^−/− than in the Mdk^+/+ mice at 3 days after TBI. However, the ratios of the glial fibrillary acidic protein immunoreactive area were similar between the two groups. The M1 phenotype marker (CD16/32) immunoreactive areas were significantly reduced in Mdk^−/− than in the Mdk^+/+ mice. Likewise, the mRNA levels of the M1 phenotype markers (TNF-α, CD11b) were significantly decreased in Mdk^−/− mice than in Mdk^+/+ mice. Furthermore, flow cytometry analysis identified the M2 markers, i.e., CD163⁺ macrophages cells and arginase-1⁺ microglia cells, to be significantly higher in Mdk^−/− than in Mdk^+/+ mice. Finally, the ratios of apoptotic neurons were significantly decreased in the area surrounding the lesion in Mdk^−/− than in Mdk^+/+ mice following TBI.

Conclusion

Our findings suggest that MK-deficiency reduced tissue infiltration of microglia/macrophages and altered their polarization status thereby reducing neuroinflammation, neuronal apoptosis, and tissue loss and improving neurological outcomes after TBI. Therefore, targeting MK to modulate neuroinflammation may represent a potential therapeutic strategy for TBI management.

Midkine promotes articular chondrocyte proliferation through the MK-LRP1-nucleolin signaling pathway

Osteoarthritis (OA) is the most common disease of joint tissues; unfortunately, there are currently no curative therapies available for OA. Chondrocytes, the only cell type residing in cartilage, secrete many types of collagen (the mainly one is type II collagen) and aggrecan, which are the main components of the cartilage matrix. Chondrocyte apoptosis can lead to OA degenerative progression. We previously indicated that recombinant human midkine (rhMK), as a chondrocyte growth factor has a significant reparative effect on cartilage injury animal models. However, the molecular mechanism of this restorative function remains under investigation. Herein, we focused on the molecular mechanism underlying the role of MK in promoting the proliferation of chondrocytes cultured in vitro. Chondrocytes from rats and OA patients were successfully isolated by the digestion of articular cartilage using type II collagenase, and their proliferation was evaluated by a CCK8 assay and flow cytometry. rhMK stimulated the proliferation of chondrocytes from both OA patients and rats. Furthermore, qRT-PCR, shRNA-mediated knockdown, Western blot and immunoprecipitation (IP) assays were performed to identify the receptor and key elements responsible for the role of MK in promoting chondrocyte proliferation. Low-density lipoprotein receptor-related protein 1 (LRP1) was identified as the dominant MK receptor in chondrocytes that, as a translocator, mediates the endocytosis of MK. After being transferred into chondrocytes, MK was shown to form a complex with nucleolin that interacts with the active form of K-Ras. Upon the activation of ERK1/2, cyclin D1 expression was upregulated, promoting the chondrocyte cell cycle. Our data reveal for the first time the role of the MK-LRP1-nucleolin signaling pathway in facilitating MK-induced chondrocyte proliferation, thus providing a strong theoretical foundation for the further use of MK in OA clinical therapy.

Midkine (MDK) growth factor: a key player in cancer progression and a promising therapeutic target

Midkine is a heparin-binding growth factor, originally reported as the product of a retinoic acid-responsive gene during embryogenesis, but currently viewed as a multifaceted factor contributing to both normal tissue homeostasis and disease development. Midkine is abnormally expressed at high levels in various human malignancies and acts as a mediator for the acquisition of critical hallmarks of cancer, including cell growth, survival, metastasis, migration, and angiogenesis. Several studies have investigated the role of midkine as a cancer biomarker for the detection, prognosis, and management of cancer, as well as for monitoring the response to cancer treatment. Moreover, several efforts are also being made to elucidate its underlying mechanisms in therapeutic resistance and immunomodulation within the tumor microenvironment. We hereby summarize the current knowledge on midkine expression and function in cancer development and progression, and highlight its promising potential as a cancer biomarker and as a future therapeutic target in personalized cancer medicine.

Inhibition of midkine by metformin can contribute to its anticancer effects in malignancies: A proposal mechanism of action of metformin in context of endometrial cancer prevention and therapy

Metformin, a drug widely used in the treatment of type II diabetes mellitus (T2DM), has been the focus of interest as a potential therapeutic agent for certain types of malignancies, including gynaecological cancers [i.e. endometrial cancer (EC)]. Although the exact mechanism behind the potential anticancer activity of metformin is still not completely understood, certain studies have suggested that different effects on cell functions, such as inhibition of cell migration, apoptosis and tumor cell proliferation, are involved in its preventive and therapeutic effects in certain types of malignancies, including EC. In contrast, midkine (MK), a heparin-binding growth factor and cytokine, which induces carcinogenesis and chemoresistance, promotes the development and progression of many malignant tumours by increasing diverse cell functions such as cell proliferation, cell survival and antiapoptotic activities via mainly the activation of phosphatidyl inositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways. The same pathways are also subject to certain therapeutic effects of metformin, although this cytokine and this drug have some different mechanism of action pathways as well. Taken together, MK and metformin appear to have opposite effects in various biological processes such as apoptosis, cell proliferation, cell survival, cell migration, and angiogenesis. On the other hand, MK activates PI3K and MAPK cell signal pathways, whereas metformin inhibits these two pathways. It seems likely that almost all the pathways and cell functions, which play important roles in malignancies, are inhibited by metformin and activated by MK. Given the opposite relationship between the actions of metformin and MK, we hypothesize that metformin may act like a novel MK inhibitor in some malignancies. We also discuss the possible relationship between metformin and MK in the context of EC, the most common gynecological cancer worldwide, which incidence is rising rapidly, in parallel with the increase in obesity, T2DM and insulin resistance. In this respect, the therapeutic use of metformin may improve the survival of EC or other cancers, via inhibiting or overcoming the unwanted effects of MK in carcinogenesis.

Pleiotrophin increases neurite length and number of spiral ganglion neurons in vitro

Acoustic trauma, aging, genetic defects or ototoxic drugs are causes for sensorineural hearing loss involving sensory hair cell death and secondary degeneration of spiral ganglion neurons. Auditory implants are the only available therapy for severe to profound sensorineural hearing loss when hearing aids do not provide a sufficient speech discrimination anymore. Neurotrophic factors represent potential therapeutic candidates to improve the performance of cochlear implants (CIs) by the support of spiral ganglion neurons (SGNs). Here, we investigated the effect of pleiotrophin (PTN), a well-described neurotrophic factor for different types of neurons that is expressed in the postnatal mouse cochlea. PTN knockout mice exhibit severe deficits in auditory brainstem responses, which indicates the importance of PTN in inner ear development and function and makes it a promising candidate to support SGNs. Using organotypic explants and dissociated SGN cultures, we investigated the influence of PTN on the number of neurons, neurite number and neurite length. PTN significantly increased the number and neurite length of dissociated SGNs. We further verified the expression of important PTN-associated receptors in the SG. mRNA of anaplastic lymphoma kinase, α_v integrin, β₃ integrin, receptor protein tyrosine phosphatase β/ζ, neuroglycan C, low-density lipoprotein receptor-related protein 1 and syndecan 3 was detected in the inner ear. These results suggest that PTN may be a novel candidate to improve sensorineural hearing loss treatment in the future.

Diagnostic value of the serum Midkine in patients with rheumatoid arthritis

Early diagnosis and detection of rheumatoid arthritis (RA) activity which is a potential therapeutic target, depends mainly on clinical presentation. However, laboratory tests may contribute to diagnosis and disease activity assessment of RA. This study aims to evaluate the accuracy of serum Midkine as serological marker for RA diagnosis and its activity detection. All patients with RA were recruited during the period from January 2016 to August 2018 in addition to healthy subjects as control. Serum Midkine level was estimated using enzyme immunoassay. The accuracy was determined for serum Midkine against the used American College of Rheumatology/European League Against Rheumatism 2010 classification criteria for RA diagnosis and disease activity score derivative for 28 joints-erythrocyte sedimentation rate (ESR) score for assessment of RA disease activity. A total of 211 of patients with RA (group I) were enrolled in this study with 112 healthy subjects (group II). Patients with RA were divided into two subgroups according to the disease activity; patients with active RA (group IA) and RA in remission (group IB). We detected that the area under curve (AUC) of serum Midkine level (AUC=0.851) was significantly lower than that of rheumatoid factor IgM and anti-cyclic citrullinated peptide IgG for RA diagnosis. However, Midkine presents a significantly higher diagnostic accuracy (AUC=0.939) in detecting RA activity than that offered by C reactive protein (CRP) or ESR. Our study suggested that serum Midkine is a potential serological marker for detection of active inflammatory state with higher diagnostic accuracy than other inflammatory markers as CRP or ESR. Therefore, it can be used as an inflammatory marker for detection of disease activity rather than diagnosis of RA.

Plasma Midkine Is Associated With 28-Day Mortality and Organ Function in Sepsis

BACKGROUND

Midkine has been reported to play a crucial role in inflammatory, hypoxia, and tissue injury processes. We aimed to investigate plasma midkine in septic patients and its association with 28-day mortality and organ function.

METHODS

Septic patients admitted to the Department of Critical Care Medicine, Zhongda Hospital, a tertiary hospital, from November 2017 to March 2018 were enrolled in the study. The baseline characteristics of the septic patients were recorded at admission. A peripheral blood sample was obtained at admission, and plasma midkine levels were evaluated with an immunoassay. All patients were followed up with for 28 days, with all-cause mortality being recorded.

RESULTS

A total of 26 septic patients were enrolled, which included 18 survivors and 8 nonsurvivors at day 28. Plasma midkine levels were significantly elevated in the nonsurvivor group compared with the survivors (ng/L, 763.6 [404.7-1305], 268.5 [147.8-511.4]; P = .0387]. Plasma midkine levels were elevated in septic patients with moderate/severe acute respiratory distress syndrome (ARDS) compared with patients with non/mild ARDS (ng/L, 522.3 [336.6-960.1] vs 243.8 [110.3-478.9]; P = .0135) and in those with acute kidney injury compared with those without (ng/L, 489.8 [259.2-1058] vs 427.9 [129.6-510.3]; P = .0973). Changes in plasma midkine levels were also associated with extravascular lung water index (P = .063) and pulmonary vascular permeability index (P = .049).

CONCLUSIONS

Plasma midkine was associated with 28-day mortality, as well as pulmonary and kidney injury, in septic patients.

Synthesis of a Fluorous-Tagged Hexasaccharide and Interaction with Growth Factors Using Sugar-Coated Microplates

Here, we report the synthesis of a sulfated, fully protected hexasaccharide as a glycosaminoglycan mimetic and the study of its interactions with different growth factors: midkine, basic fibroblast growth factor (FGF-2) and nerve growth factor (NGF). Following a fluorous-assisted approach, monosaccharide building blocks were successfully assembled and the target oligosaccharide was prepared in excellent yield. The use of more acid stable 4,6-O-silylidene protected glucosamine units was crucial for the efficiency of this strategy because harsh reaction conditions were needed in the glycosylations to avoid the formation of orthoester side products. Fluorescence polarization experiments demonstrated the strong interactions between the synthesized hexamer, and midkine and FGF-2. In addition, we have developed an alternative assay to analyse these molecular recognition events. The prepared oligosaccharide was non-covalently attached to a fluorous-functionalized microplate and the direct binding of the protein to the sugar-immobilized surface was measured, affording the corresponding K_D,surf value.

Connecting Metainflammation and Neuroinflammation Through the PTN-MK-RPTPβ/ζ Axis: Relevance in Therapeutic Development

Inflammation is a common factor of pathologies such as obesity, type 2 diabetes or neurodegenerative diseases. Chronic inflammation is considered part of the pathogenic mechanisms of different disorders associated with aging. Interestingly, peripheral inflammation and the associated metabolic alterations not only facilitate insulin resistance and diabetes but also neurodegenerative disorders. Therefore, the identification of novel pathways, common to the development of these diseases, which modulate the immune response and signaling is key. It will provide highly relevant information to advance our knowledge of the multifactorial process of aging, and to establish new biomarkers and/or therapeutic targets to counteract the underlying chronic inflammatory processes. One novel pathway that regulates peripheral and central immune responses is triggered by the cytokines pleiotrophin (PTN) and midkine (MK), which bind its receptor, Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ, and inactivate its phosphatase activity. In this review, we compile a growing body of knowledge suggesting that PTN and MK modulate the immune response and/or inflammation in different pathologies characterized by peripheral inflammation associated with insulin resistance, such as aging, and in central disorders characterized by overt neuroinflammation, such as neurodegenerative diseases and endotoxemia. Evidence strongly suggests that regulation of the PTN and MK signaling pathways may provide new therapeutic opportunities particularly in those neurological disorders characterized by increased PTN and/or MK cerebral levels and neuroinflammation. Importantly, we discuss existing therapeutics, and others being developed, that modulate these signaling pathways, and their potential use in pathologies characterized by overt neuroinflammation.

The Expression, Functions, Interactions and Prognostic Values of PTPRZ1: A Review and Bioinformatic Analysis

Available studies demonstrate that receptor-type tyrosine-protein phosphatase zeta (PTPRZ1) is expressed in different tumor tissues, and functions in cell proliferation, cell adhesion and migration, epithelial-to-mesenchymal transition, cancer stem cells and treatment resistance by interacting with or binding to several molecules. These included pleiotrophin (PTN), midkine, interleukin-34, β-catenin, VEGF, NF-κB, HIF-2, PSD-95, MAGI-3, contactin and ErbB4. PTPRZ1 was involved in survival signaling and could predict the prognosis of several tumors. This review discusses: the current knowledge about PTPRZ1, its expression, co-receptors, ligands, functions, signaling pathway, prognostic values and therapeutic agents that target PTPRZ1.

Pleiotropic Effects of Heparins: From Clinical Applications to Molecular Mechanisms in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a major health problem worldwide and most cases are incurable because of late presentation. It is the most common primary neoplasm of the liver and often arises in the context of a chronic liver disease that impairs coagulation. Portal vein thrombosis (PVT) is a common complication of HCC that is associated with a poor prognosis. Heparin derivatives are widely used in the management of venous thromboembolism (VTE). Among them low molecular weight heparin (LMWH) favorably influences the survival in patients with advanced cancer, including HCC. Due to their pleiotropic function, heparins affect tumorigenesis in many ways and may promote or hamper tumorigenic transformation depending on the cancer type and cancer stage along with their structural properties and concentration. Thus, their application as an antithrombotic along with the conventional therapy regime should be carefully planned to develop the best management strategies. In this review, we first will briefly review clinical applications of heparin derivatives in the management of cancer with a particular focus on HCC. We then summarize the state of knowledge whereby heparin can crosstalk with molecules playing a role in hepatocarcinogenesis. Lastly, we highlight new experimental and clinical research conducted with the aim of moving towards personalized therapy in cancer patients at risk of thromboembolism.

Midkine promotes hepatocellular carcinoma metastasis by elevating anoikis resistance of circulating tumor cells

Midkine is overexpressed in hepatocellular carcinoma (HCC) and plays a role in tumor progression, but less is known about its role in resistance of circulating tumor cells (CTCs) to anoikis which leading to recurrence and metastasis. The aim of the present study was to analyze whether midkine was associated with HCC progression with anoikis resistance. We found that cultured HCC cells were more resistant to anoikis, which paralleled midkine expression, and midkine treatment significantly inhibited anoikis in a dose-dependent manner. Furthermore, in in vitro and in vivo assays, knockdown of midkine resulted in significant sensitivity to anoikis, decreased cell survival and significantly decreased tumor occurrence rate. Patients with midkine-elevated HCC had higher CTC counts and less apoptotic CTCs, as well as significantly higher recurrence rate and shorter recurrence-free interval. To understand the molecular mechanism underlying the midkine with HCC progression, we performed in vitro and in vivo studies. We found that midkine plays an important role in enhancement of HCC cell resistance to anoikis, thereby promoting subsequent metastasis. Activation of PI3K/Akt/NF-κB/TrkB signaling by midkine-activated anaplastic lymphomakinase (ALK) is responsible for anoikis resistance.

Positive expression of Midkine predicts early recurrence and poor prognosis of initially resectable combined hepatocellular cholangiocarcinoma

Background

Post-surgical prognosis is usually poor for combined hepatocellular cholangiocarcinoma (CHCC-CC), a rare primary liver cancer. Although midkine (MK) is a prognostic biomarker for several known cancers, it is not known whether it can be used as such in resectable CHCC-CC. This study examined whether MK expression can predict recurrence and survival in patients with resectable CHCC-CC.

Methods

We retrospectively enrolled 52 patients with resectable CHCC-CC who had received curative hepatic resections. MK expression was assessed in post-surgical immunohistochemical studies of specimens in paraffin blocks. Clinical outcomes were analyzed from medical records.

Results

Two-year disease-free and three-year overall survival rates were 42.1% and 44.6%. MK was expressed in 30 patients. Univariate analysis showed patients positively expressing MK had a significantly poorer 2-year disease free and three-year overall survival. Multivariate analysis found positive MK expression independently predicted recurrence.

Conclusions

Positive expression of MK predicts poor prognosis in patients with resectable CHCC-CC.

Bioactive polysaccharides from natural resources including Chinese medicinal herbs on tissue repair

BACKGROUND

Functional polysaccharides can be derived from plants (including herbs), animals and microorganisms. They have been widely used in a broad of biomedical applications, such as immunoregulatory agents or drug delivery vehicles. In the past few years, increasing studies have started to develop natural polysaccharides-based biomaterials for various applications in tissue engineering and regenerative medicine.

MAIN BODY

We discuss in this article the emerging applications of natural polysaccharides-particularly those derived from Chinese medicine-for wound healing. First, we introduce natural polysaccharides of three natural sources and their biological activities. Then, we focus on certain natural polysaccharides with growth factor-binding affinities and their inspired polymeric tools, with an emphasis on how these polysaccharides could possibly benefit wound healing. Finally, we report the latest progress in the discovery of polysaccharides from Chinese medicinal herbs with identified activities favouring tissue repair.

CONCLUSION

Natural polysaccharides with clearly elucidated compositions/structures, identified cellular activities, as well as desirable physical properties have shown the potential to serve as therapeutic tools for tissue regeneration.

Prognostic value of Midkine expression in patients with solid tumors: a systematic review and meta-analysis

Background

Accumulated studies have shown the important role of Midkine (MDK) protein in various solid tumors and indicated its correlation with patients' survival. This meta-analysis was performed to further explore the prognostic value of MDK expression in solid tumors.

Materials and Methods

We collected the literatures through searching PubMed, Embase and the Cochrane Library (last up to April 10, 2017) to assess the effect of MDK on survival in solid tumor patients. The STATA 12.0 software was used for the meta-analysis. Fixed-effects models or random-effects models were used to estimate the pooled hazard ratios (HRs) for overall survival (OS).

Results

A total of 2097 patients from 17 observational studies were summarized. High expression of MDK was notably associated with worse OS in solid tumor patients. (pooled HR = 1.96; 95% CI = 1.67-2.31). The subgroup analysis of tumor type demonstrated negative impact of elevated MDK on OS in most solid tumor patients (P < 0.05), while MDK had no relevance with OS in the patients with OSCC (pooled HR = 1.68; 95% CI = 0.84-3.36; P = 0.145) or HNSCC (pooled HR = 1.56; 95% CI = 0.96-2.51; P = 0.075).

Conclusions

The present meta-analysis clarifies that MDK is a potential prognostic biomarker in solid tumor patients. Future large-scale prospective clinical trials are needed to determine the prognostic value of MDK in solid tumor patients.

Increased serum midkine levels in autism spectrum disorder patients

BACKGROUND

Midkine (MK) is a heparin binding growth factor and is involved in neurogenesis, neural development and neuroprotection. Additionally, MK may contribute to cancer development and pathogenesis of neurodegenerative disorders and schizophrenia. Considering these effects of MK, this study researched whether MK is involved in autism spectrum disorders (ASD) pathogenesis.

METHODS

We evaluated serum MK levels of 38 patients with ASD and 32 healthy control group. MK levels were measured with ELISA, while ASD severity was assessed with Childhood Autism Rating Scale.

RESULTS

Our data showed that the serum MK concentration in ASD patients (mean ± SD, 11.51 ± 8.53 pg/ml) is significantly higher than healthy controls (mean ± SD, 6.19 ± 3.94 pg/ml) (p = 0.007).

CONCLUSIONS

According to these results, MK may play a role in ASD pathogenesis.