Mechanism of Action of Mesenchymal Stem Cell-Derived Exosomes in the Intervertebral Disc Degeneration Treatment and Bone Repair and Regeneration

Exosomes are extracellular vesicles formed by various donor cells that regulate gene expression and cellular function in recipient cells. Exosomes derived from mesenchymal stem cells (MSC-Exos) perform the regulatory function of stem cells by transporting proteins, nucleic acids, and lipids. Intervertebral disc degeneration (IDD) is one of the main causes of low back pain, and it is characterized by a decreased number of nucleus pulposus cells, extracellular matrix decomposition, aging of the annulus fibrosus, and cartilage endplate calcification. Besides, nutrient transport and structural repair of intervertebral discs depend on bone and cartilage and are closely related to the state of the bone. Trauma, disease and aging can all cause bone injury. However, there is a lack of effective drugs against IDD and bone injury. Recent MSC-Exos fine tuning has led to significant progress in the IDD treatment and bone repair and regeneration. In this review, we looked at the uniqueness of MSC-Exos, and the potential treatment mechanisms of MSC-Exos with respect to IDD, bone defects and injuries.

SH3-domain mutations selectively disrupt Csk homodimerization or PTPN22 binding

The kinase Csk is the primary negative regulator of the Src-family kinases (SFKs, i.e., Lck, Fyn, Lyn, Hck, Fgr, Blk, Src, Yes), phosphorylating a tyrosine on the SFK C-terminal tail that nucleates an autoinhibitory complex. Csk also binds phosphatases, including PTPN12 (PTP-PEST) and immune-cell PTPN22 (Pep/LYP), which dephosphorylate the SFK activation loop to promote autoinhibition. High local concentrations of Csk are required to promote its negative-regulatory function, and Csk-binding proteins (e.g., CBP/PAG1) oligomerize within membrane microdomains. Purified Csk also homodimerizes in solution through an interface that overlaps the phosphatase binding site. Here we demonstrate that Csk can homodimerize in Jurkat T cells, in competition with PTPN22 binding. We designed SH3-domain mutations in Csk that selectively impair homodimerization (H21I) or PTPN22 binding (K43D) and verified their kinase activity in solution. Csk W47A, an SH3-domain mutant commonly used to block PTPN22 binding, also impairs homodimerization. Csk H21I and K43D will be useful tools for dissecting the protein-specific drivers of autoimmunity mediated by the human polymorphism PTPN22 R620W, which impairs interaction with both Csk and with the E3 ubiquitin ligase TRAF3. Future investigations of Csk homodimer activity and phosphatase interactions may reveal new facets of SFK regulation in hematopoietic and non-hematopoietic cells.

B cell receptor antigen receptor expression and phosphatidylinositol 3-kinase signaling regulate genesis and maintenance of mouse chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a frequent lymphoproliferative disorder of B cells. Although inhibitors targeting signal proteins involved in B cell antigen receptor (BCR) signaling constitute an important part of the current therapeutic protocols for CLL patients, the exact role of BCR signaling, as compared to genetic aberration, in the development and progression of CLL is controversial. To investigate whether BCR expression per se is pivotal for the development and maintenance of CLL B cells, we used the TCL1 mouse model. By ablating the BCR in CLL cells from TCL1 transgenic mice, we show that CLL cells cannot survive without BCR signaling and are lost within eight weeks in diseased mice. Furthermore, we tested whether mutations augmenting B cell signaling influence the course of CLL development and its severity. The Phosphatidylinositol-3-kinase (PI3K) signaling pathway is an integral part of the BCR signaling machinery and its activity is indispensable for B cell survival. It is negatively regulated by the lipid phosphatase PTEN, whose loss mimics PI3K pathway activation. Herein, we show that PTEN has a key regulatory function in the development of CLL, as deletion of the Pten gene resulted in greatly accelerated onset of the disease. By contrast, deletion of the gene TP53, which encodes the tumor suppressor p53 and is highly mutated in CLL, did not accelerate disease development, confirming that development of CLL was specifically triggered by augmented PI3K activity through loss of PTEN and suggesting that CLL driver consequences most likely affect BCR signaling. Moreover, we could show that in human CLL patient samples, 64% and 81% of CLL patients with a mutated and unmutated IgH VH, respectively, show downregulated PTEN protein expression in CLL B cells if compared to healthy donor B cells. Importantly, we found that B cells derived from CLL patients had higher expression levels of the miRNA-21 and miRNA-29, which suppresses PTEN translation, compared to healthy donors. The high levels of miRNA-29 might be induced by increased PAX5 expression of the B-CLL cells. We hypothesize that downregulation of PTEN by increased expression levels of miR-21, PAX5 and miR-29 could be a novel mechanism of CLL tumorigenesis that is not established yet. Together, our study demonstrates the pivotal role for BCR signaling in CLL development and deepens our understanding of the molecular mechanisms underlying the genesis of CLL and for the development of new treatment strategies.

Accentuating CircRNA-miRNA-Transcription Factors Axis: A Conundrum in Cancer Research

Circular RNAs (circRNAs) are the newly uncovered class of non-coding RNAs being cognized as profound regulators of gene expression in developmental and disease biology. These are the covalently closed RNAs synthesized when the pre-mRNA transcripts undergo a back-splicing event. In recent years, circRNAs are gaining special attention in the scientific world and are no longer considered as “splicing noise” but rather structurally stable molecules having multiple biological functions including acting as miRNA sponges, protein decoys/scaffolds, and regulators of transcription and translation. Further, emerging evidence suggests that circRNAs are also differentially expressed in multiple cancers where they play oncogenic roles. In addition, circRNAs in association with miRNAs change the expression patterns of multiple transcription factors (TFs), which play important roles in cancer. Thus, the circRNA-miRNA-TFs axis is implicated in the progression or suppression of various cancer types and plays a role in cell proliferation, invasion, and metastasis. In this review article, we provide an outline of the biogenesis, localization, and functions of circRNAs specifically in cancer. Also, we highlight the regulatory function of the circRNA-miRNA-TFs axis in the progression or suppression of cancer and the targeting of this axis as a potential therapeutic approach for cancer management. We anticipate that our review will contribute to expanding the knowledge of the research community about this recent and rapidly growing field of circRNAs for further thorough investigation which will surely help in the management of deadly disease cancer.

Single-nucleus chromatin accessibility identifies a critical role for TWIST1 in idiopathic pulmonary fibrosis myofibroblast activity

In idiopathic pulmonary fibrosis (IPF) myofibroblasts are key effectors of fibrosis and architectural distortion by excessive deposition of extracellular matrix and their acquired contractile capacity. Single-cell RNA-sequencing has precisely defined the IPF myofibroblast transcriptome, but identifying critical transcription factor activity by this approach is imprecise. We performed and integrated snATAC-seq and scRNA-seq from human IPF and donor control explants to identify differentially accessible chromatin regions and enriched transcription factor motifs within lung cell populations. TWIST1 and other E-box transcription factor motifs were significantly enriched in IPF myofibroblasts compared to both IPF non-myogenic and control fibroblasts. TWIST1 expression was also selectively upregulated in IPF myofibroblasts. Overexpression of Twist1 in lung COL1A2-expressing fibroblasts in bleomycin-injured mice was associated with increased collagen synthesis. Our studies utilizing human multiomic single-cell analyses combined with in vivo murine disease models confirm a critical regulatory function for TWIST1 in IPF myofibroblast activity in the fibrotic lung. Understanding the global process of opening TWIST1 and other E-box TF motifs that govern myofibroblast differentiation may identify new therapeutic interventions for fibrotic pulmonary diseases.

Effect of astrocyte on synchronization of thermosensitive neuron-astrocyte minimum system

Astrocytes have a regulatory function on the central nervous system (CNS), especially in the temperature sensitive hippocampal region. In order to explore the thermosensitive dynamic mechanism of astrocytes in CNS, we establish a neuron-astrocyte minimum system to analyze the synchronization change characteristics based on Hodgkin-Huxley model, in which a pyramidal cell and an interneuron are connected by an astrocyte. Besides, the temperature range set 0°C-40°C to juggle theoretical calculation and reality of brain environment. It is represented that the synchronization of thermosensitive neurons exhibits nonlinear behavior with change of astrocyte parameters. At temperature range of 0°C-18°C, the effects of astrocyte can provide tremendous influence to neurons in synchronization. We found existence of a value for inositol triphosphate (IP3) production rate and feedback intensities of astrocyte to neurons, which can ensure the weak synchronization of two neurons. In addition, it is revealed that the regulation of astrocyte to pyramidal cell is more sensitive than that to interneuron. Finally, it is shown that the synchronization and phase transition of neurons depend on the change of Ca2+ concentration at the temperature of weak synchronization. The results in this paper would provide some enlightenment in mechanism of cognitive dysfunction and neurological disorders with astrocytes.

FORMATION OF MORAL CONSCIOUSNESS PRIMARY SCHOOL CHILDREN BASED ON COMPETENCE APPROACH

The article examines some aspects of the formation of the moral consciousness of modern schoolchildren on the basis of one of the leading methodological principles - the competence-based approach. Large-scale changes taking place in various spheres of society, new social and economic reality, developing market relations, digitalization, modernization of Russian education require a revision of the strategy and tactics of educating the younger generation in terms of solving the problems of forming high moral qualities of the personality of students, including primary school age. But is a modern teacher competent enough to successfully cope with the multitasking of real pedagogical reality, including the moral education of schoolchildren? The study of the problem under consideration in theory and in practice shows that moral education is significant, first of all, because it permeates all aspects of education: mental, aesthetic, physical, labor, environmental, etc. Hence, its backbone nature is obvious. Any human action presupposes a moral aspect, including the regulatory function of morality. All of the above served as the basis for choosing the topic of the article. According to the authors, the results and conclusion of this article can, to a certain extent, actualize the problem of the formation of the moral consciousness of primary schoolchildren from the standpoint of the competence-based approach and outline ways to solve it.

Function and constraint in enhancers with multiple evolutionary origins

Motivation: Thousands of human gene regulatory enhancers are composed of sequences with multiple evolutionary origins. These evolutionarily "complex" enhancers consist of older "core" sequences and younger "derived" sequences. However, the functional relationship between the sequences of different evolutionary origins within complex enhancers is poorly understood. Results: We evaluated the function, selective pressures, and sequence variation across core and derived components of human complex enhancers. We find that both components are older than expected from the genomic background, and cores are enriched for derived sequences of similar evolutionary ages. Both components show strong evidence of biochemical activity in massively parallel report assays (MPRAs). However, core and derived sequences have distinct transcription factor (TF) binding preferences that are largely stable across evolutionary origins. Given these signatures of function, both core and derived sequences have substantial evidence of purifying selection. Nonetheless, derived sequences exhibit weaker purifying selection than adjacent cores. Derived sequences also tolerate more common genetic variation and are enriched compared to cores for eQTL associated with gene expression variability in human populations. Conclusions: Both core and derived sequences have strong evidence of gene regulatory function, but derived sequences have distinct constraint profiles, TF binding preferences, and tolerance to variation compared with cores. We propose that the step-wise integration of younger derived and older core sequences has generated regulatory substrates with robust activity and the potential for functional variation. Our analyses demonstrate that synthesizing study of enhancer evolution and function can aid interpretation of regulatory sequence activity and functional variation across human populations.

circ_0035277 Promotes Gastric Cancer Proliferation and Metastasis via miR-576-3p/LIN28B Axis

Circular RNAs (circRNAs) regulate biological processes of human tumours. Gastric cancer is a prevalent disease that presents tumours with high metastasis. This study aimed to understand regulatory function and mechanism of circ_0035277 in gastric cancer development. circ_0035277 level in tissues and cells was assessed using RT-qPCR assay. Function of circ_0035277 was evaluated via CCK-8, colony formation and Transwell assays. Location of circ_0035277 was verified with FISH assay. Potential mechanism of circ_0035277 was examined using bioinformatics and luciferase reporter assays. BALB/c nude mice were utilised to construct the gastric cancer metastasis model with subcutaneous injection. Haematoxylin–eosin staining was performed to measure visible tumour nodules in lung tissues. Results showed that circ_0035277 is significantly up-regulated in tissues and cell lines of gastric cancer, accelerates the deterioration of gastric cancer, is significantly located in the cytoplasm and serves as a sponge to participate in gastric cancer by targeting miR-576-3p. Furthermore, lin-28 homolog B (LIN28B) was a direct target of miR-576-3p and reversed the role of circ_0035277/miR-576-3p on gastric cancer metastasis. In vivo studies have shown that knockdown of circ_0035277 suppresses gastric cancer metastasis. Overall, circ_0035277 accelerated gastric cancer progression and metastasis by regulating miR-576-3p/LIN28B axis. These findings can provide a potential target for the treatment of gastric cancer.