CXCL12 secretion by bone marrow stromal cells is dependent on cell contact and mediated by connexin-43 and connexin-45 gap junctions

Piezoelectric Heterojunctions as Bacteria-Killing Bone-Regenerative Implants

Heterojunctions are widely used in energy conversion, environmental remediation, and photodetection, but have not been fully explored in regenerative medicine. In particular, piezoelectric heterojunctions have never been examined in tissue regeneration. Here the development of piezoelectric heterojunctions is shown to promote bone regeneration while eradicating pathogenic bacteria through light-cellular force-electric coupling. Specifically, an array of heterojunctions (TiO2/Bi2WO6), made of piezoelectric nanocrystals (Bi2WO6) decorating TiO2 nanowires, is fabricated as a biocompatible implant. Upon exposure to near-infrared light, the piezoelectric heterojunctions generate reactive oxygen species and heat to kill bacteria through photodynamic and photothermal therapy, respectively. Meanwhile, the mechanical forces of the stem cells grown on the implant trigger the heterojunctions to produce electric fields that further promote osteogenesis to achieve osteointegration. The heterojunctions effectively suppress postoperative recurrent infections while promoting osseointegration through the local electric fields induced by cells. Therefore, the piezoelectric heterojunctions represent a promising antibacterial tissue-regenerative implant.

A Dual-Function LipoAraN-E5 Coloaded with N4-Myristyloxycarbonyl-1-β-d-arabinofuranosylcytosine (AraN) and a CXCR4 Antagonistic Peptide (E5) for Blocking the Dissemination of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a hematological malignancy with a high recurrence rate. The interaction of chemokine receptor 4/chemokine ligand 12 (CXCR4/CXCL12) mediates homing and adhesion of AML cells in bone marrow, leading to minimal residual disease in patients, which brings a hidden danger for future AML recurrence. Ara-C is a nonselective chemotherapeutic agent against AML. Due to its short half-life and severe side effects, a lipid-like Ara-C derivative (AraN) was synthesized and a dual-function LipoAraN-E5 (135 nm, encapsulation efficiency 99%) was developed, which coloaded AraN and E5, a peptide of the CXCR4 antagonist. LipoAraN-E5 effectively improved the uptake, enhanced the inhibition of leukemia cell proliferation, migration, and adhesion to stromal cells in bone marrow, and mobilized the leukemia cells from bone marrow to peripheral blood via interfering with the CXCR4/CXCL12 axis. LipoAraN-E5 prolonged the plasma half-life of AraN (8.31 vs 0.56 h) and was highly enriched in peripheral blood (3.67 vs 0.05 μmol/g at 8 h) and bone marrow (379 vs 148 μmol/g at 24 h). LipoAraN-E5 effectively prevented the infiltration of leukemia cells in peripheral blood, bone marrow, spleen, and liver, prolonged the mice survival, and showed outstanding antineoplastic efficacy with negligible toxicity, which were attributed to the ingenious design of AraN, the use of a liposomal delivery carrier, and the introduction of E5. Our work revealed that LipoAraN-E5 may be a promising nanocandidate against AML.

Silencing endomucin in bone marrow sinusoids improves hematopoietic stem and progenitor cell homing during transplantation

Efficient homing of infused hematopoietic stem and progenitor cells (HSPCs) into the bone marrow (BM) is the prerequisite for successful hematopoietic stem cell transplantation. However, only a small part of infused HSPCs find their way to the BM niche. A better understanding of the mechanisms that facilitate HSPC homing will help to develop strategies to improve the initial HSPC engraftment and subsequent hematopoietic regeneration. Here, we show that irradiation upregulates the endomucin expression of endothelial cells in vivo and in vitro. Furthermore, depletion of endomucin in irradiated endothelial cells with short-interfering RNA (siRNA) increases the HSPC-endothelial cell adhesion in vitro. To abrogate the endomucin of BM sinusoidal endothelial cells (BM-SECs) in vivo, we develop a siRNA-loaded bovine serum albumin nanoparticle for targeted delivery. Nanoparticle-mediated siRNA delivery successfully silences endomucin expression in BM-SECs and improves HSPC homing during transplantation. These results reveal that endomucin plays a critical role in HSPC homing during transplantation and that gene-based manipulation of BM-SEC endomucin in vivo can be exploited to improve the efficacy of HSPC transplantation.

Establishment of Early Blood Perfusion Promotes CXCL12 Expression and Recruits Monocytes/Macrophages in Damaged Adipose Tissue in Mice Model

BACKGROUND

Blood perfusion in the recipient site is important for adipose tissue repair after fat grafting. It delivers host-derived macrophages derived from monocytes in bone marrow to initiate inflammatory reactions and regenerative responses. According to the ability of CXCL12, a stromal cell-derived factor, to recruit monocytes/macrophages, we studied its effect on adipose tissue repair and regeneration under ischemic and normal conditions.

METHODS

Each inguinal fat pad was crushed for 30 seconds with a clamp in mice (n = 35). The left inguinal vessels were divided and cut off (ischemic group), while the right inguinal vessels were kept patent (control group). Seven animals were sacrificed at 1, 3, 7, 14, and 30 days after surgery, and macrophages (Mac2 and CD206) and adipocytes (perilipin) were assessed. Levels of inflammatory factors (interleukin (IL)-1β, IL-6, and tumor necrosis factor-α) and CXCL12 were measured by quantitative PCR.

RESULTS

The number of macrophages was higher in the control group than in the ischemic group at day 3 (10.33 ± 2.40 vs. 1.33 ± 0.33, p = 0.021). The percentage of M2 macrophages was higher in the control group than in the ischemic group at day 7 (p<0.05). The levels of inflammatory factors and CXCL12 were higher in the control group than in the ischemic group at the early stage (p = 0.038).

CONCLUSIONS

Established blood perfusion leads to up-regulation of CXCL12 during adipose tissue repair and regeneration, which may increase recruitment of monocytes to damaged adipose tissue. These findings increase understanding of the cellular events involved in fat graft survival after grafting.

NO LEVEL ASSIGNED

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Proteogenomic characterization identifies clinical subgroups in EGFR and ALK wild-type never-smoker lung adenocarcinoma

Patients with lung adenocarcinoma who have never smoked (NSLA) and lack key driver mutations, such as those in the EGFR and ALK genes, face limited options for targeted therapies. They also tend to have poorer outcomes with immune checkpoint inhibitors than lung cancer patients who have a history of smoking. The proteogenomic profile of nonsmoking lung adenocarcinoma patients without these oncogenic driver mutations is poorly understood, which complicates the precise molecular classification of these cancers and highlights a significant area of unmet clinical need. This study analyzed the genome, transcriptome, and LC‒MS/MS-TMT-driven proteome data of tumors obtained from 99 Korean never-smoker lung adenocarcinoma patients. NSLA tumors without EGFR or ALK driver oncogenes were classified into four proteogenomic subgroups: proliferation, angiogenesis, immune, and metabolism subgroups. These 4 molecular subgroups were strongly associated with distinct clinical outcomes. The proliferation and angiogenesis subtypes were associated with a poorer prognosis, while the immune subtype was associated with the most favorable outcome, which was validated in an external lung cancer dataset. Genomic-wide impacts were analyzed, and significant correlations were found between copy number alterations and both the transcriptome and proteome for several genes, with enrichment in the ERBB, neurotrophin, insulin, and MAPK signaling pathways. Proteogenomic analyses suggested several targetable genes and proteins, including CDKs and ATR, as potential therapeutic targets in the proliferation subgroup. Upregulated cytokines, such as CCL5 and CXCL13, in the immune subgroup may serve as potential targets for combination immunotherapy. Our comprehensive proteogenomic analysis revealed the molecular subtypes of EGFR- and ALK-wild-type NSLA with significant unmet clinical needs.

A subpopulation of human bone marrow erythroid cells displays a myeloid gene expression signature similar to that of classic monocytes

Erythroid cells, serving as progenitors and precursors to erythrocytes responsible for oxygen transport, were shown to exhibit an immunosuppressive and immunoregulatory phenotype. Previous investigations from our research group have revealed an antimicrobial gene expression profile within murine bone marrow erythroid cells which suggested a role for erythroid cells in innate immunity. In the present study, we focused on elucidating the characteristics of human bone marrow erythroid cells through comprehensive analyses, including NanoString gene expression profiling utilizing the Immune Response V2 panel, a BioPlex examination of chemokine and TGF-beta family proteins secretion, and analysis of publicly available single-cell RNA-seq data. Our findings demonstrate that an erythroid cell subpopulation manifests a myeloid-like gene expression signature comprised of antibacterial immunity and neutrophil chemotaxis genes which suggests an involvement of human erythroid cells in the innate immunity. Furthermore, we found that human erythroid cells secreted CCL22, CCL24, CXCL5, CXCL8, and MIF chemokines. The ability of human erythroid cells to express these chemokines might facilitate the restriction of immune cells in the bone marrow under normal conditions or contribute to the ability of erythroid cells to induce local immunosuppression by recruiting immune cells in their immediate vicinity in case of extramedullary hematopoiesis.

Self-Stimulated Photodynamic Nanoreactor in Combination with CXCR4 Antagonists for Antileukemia Therapy

The treatment of acute myeloid leukemia (AML) remains unsatisfactory, owing to the absence of efficacious therapy regimens over decades. However, advances in molecular biology, including inhibiting the CXCR4/CXCL12 biological axis, have introduced novel therapeutic options for AML. Additionally, self-stimulated phototherapy can solve the poor light penetration from external sources, and it will overcome the limitation that traditional phototherapy cannot be applied to the treatment of AML. Herein, we designed and manufactured a self-stimulated photodynamic nanoreactor to enhance antileukemia efficacy and suppress leukemia recurrence and metastasis in AML mouse models. To fulfill our design, we utilized the CXCR4/CXCL12 biological axis and biomimetic cell membranes in conjunction with self-stimulated phototherapy. This nanoreactor possesses the capability to migrate into the bone marrow cavity, inhibit AML cells from infiltrating into the visceral organ, significantly enhance the antileukemia effect, and prolong the survival time of leukemic mice. Therefore, this nanoreactor has significant potential for achieving high success rates and low recurrence rates in leukemia treatment.

Mesenchymal stromal cells, metabolism, and mitochondrial transfer in bone marrow normal and malignant hematopoiesis

Hematopoietic stem cell (HSC) transplantation-based treatments are in different phases of clinical development, ranging from current therapies to a promise in the repair and regeneration of diseased tissues and organs. Mesenchymal stromal/stem cells (MSCs), which are fibroblast-like heterogeneous progenitors with multilineage differentiation (osteogenic, chondrogenic, and adipogenic) and self-renewal potential, and exist in the bone marrow (BM), adipose, and synovium, among other tissues, represent one of the most widely used sources of stem cells in regenerative medicine. MSCs derived from bone marrow (BM-MSCs) exhibit a variety of traits, including the potential to drive HSC fate and anti-inflammatory and immunosuppressive capabilities via paracrine activities and interactions with the innate and adaptive immune systems. The role of BM-MSC-derived adipocytes is more controversial and may act as positive or negative regulators of benign or malignant hematopoiesis based on their anatomical location and functional crosstalk with surrounding cells in the BM microenvironment. This review highlights the most recent clinical and pre-clinical findings on how BM-MSCs interact with the surrounding HSCs, progenitors, and immune cells, and address some recent insights on the mechanisms that mediate MSCs and adipocyte metabolic control through a metabolic crosstalk between BM microenvironment cells and intercellular mitochondrial transfer in normal and malignant hematopoiesis.

Glial Cells of the Central Nervous System: A Potential Target in Chronic Prostatitis/Chronic Pelvic Pain Syndrome

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is one of the most common diseases of the male urological system while the etiology and treatment of CP/CPPS remain a thorny issue. Cumulative research suggested a potentially important role of glial cells in CP/CPPS. This narrative review retrospected literature and grasped the research process about glial cells and CP/CPPS. Three types of glial cells showed a crucial connection with general pain and psychosocial symptoms. Microglia might also be involved in lower urinary tract symptoms. Only microglia and astrocytes have been studied in the animal model of CP/CPPS. Activated microglia and reactive astrocytes were found to be involved in both pain and psychosocial symptoms of CP/CPPS. The possible mechanism might be to mediate the production of some inflammatory mediators and their interaction with neurons. Glial cells provide a new insight to understand the cause of complex symptoms of CP/CPPS and might become a novel target to develop new treatment options. However, the activation and action mechanism of glial cells in CP/CPPS needs to be further explored.

Cx43 can form functional channels at the nuclear envelope and modulate gene expression in cardiac cells

Classically associated with gap junction-mediated intercellular communication, connexin43 (Cx43) is increasingly recognized to possess non-canonical biological functions, including gene expression regulation. However, the mechanisms governing the localization and role played by Cx43 in the nucleus, namely in transcription modulation, remain unknown. Using comprehensive and complementary approaches encompassing biochemical assays, super-resolution and immunogold transmission electron microscopy, we demonstrate that Cx43 localizes to the nuclear envelope of different cell types and in cardiac tissue. We show that translocation of Cx43 to the nucleus relies on Importin-β, and that Cx43 significantly impacts the cellular transcriptome, likely by interacting with transcriptional regulators. In vitro patch-clamp recordings from HEK293 and adult primary cardiomyocytes demonstrate that Cx43 forms active channels at the nuclear envelope, providing evidence that Cx43 can participate in nucleocytoplasmic shuttling of small molecules. The accumulation of nuclear Cx43 during myogenic differentiation of cardiomyoblasts is suggested to modulate expression of genes implicated in this process. Altogether, our study provides new evidence for further defining the biological roles of nuclear Cx43, namely in cardiac pathophysiology.

Mitochondrial transfer in hematological malignancies

Mitochondria are energy-generated organelles and take an important part in biological metabolism. Mitochondria could be transferred between cells, which serves as a new intercellular communication. Mitochondrial transfer improves mitochondrial defects, restores the biological functions of recipient cells, and maintains the high metabolic requirements of tumor cells as well as drug resistance. In recent years, it has been reported mitochondrial transfer between cells of bone marrow microenvironment and hematological malignant cells play a critical role in the disease progression and resistance during chemotherapy. In this review, we discuss the patterns and mechanisms on mitochondrial transfer and their engagement in different pathophysiological contexts and outline the latest knowledge on intercellular transport of mitochondria in hematological malignancies. Besides, we briefly outline the drug resistance mechanisms caused by mitochondrial transfer in cells during chemotherapy. Our review demonstrates a theoretical basis for mitochondrial transfer as a prospective therapeutic target to increase the treatment efficiency in hematological malignancies and improve the prognosis of patients.

Consequences of HIV infection in the bone marrow niche

Dysregulation of the bone marrow niche resulting from the direct and indirect effects of HIV infection contributes to haematological abnormalities observed in HIV patients. The bone marrow niche is a complex, multicellular environment which functions primarily in the maintenance of haematopoietic stem/progenitor cells (HSPCs). These adult stem cells are responsible for replacing blood and immune cells over the course of a lifetime. Cells of the bone marrow niche support HSPCs and help to orchestrate the quiescence, self-renewal and differentiation of HSPCs through chemical and molecular signals and cell-cell interactions. This narrative review discusses the HIV-associated dysregulation of the bone marrow niche, as well as the susceptibility of HSPCs to infection by HIV.

Inflammatory abrasion of hematopoietic stem cells: a candidate clue for the post-CAR-T hematotoxicity?

Chimeric antigen receptor T-cell (CAR-T) therapy has shown remarkable effects in treating various hematological malignancies. However, hematotoxicity, specifically neutropenia, thrombocytopenia, and anemia, poses a serious threat to patient prognosis and remains a less focused adverse effect of CAR-T therapy. The mechanism underlying lasting or recurring late-phase hematotoxicity, long after the influence of lymphodepletion therapy and cytokine release syndrome (CRS), remains elusive. In this review, we summarize the current clinical studies on CAR-T late hematotoxicity to clarify its definition, incidence, characteristics, risk factors, and interventions. Owing to the effectiveness of transfusing hematopoietic stem cells (HSCs) in rescuing severe CAR-T late hematotoxicity and the unignorable role of inflammation in CAR-T therapy, this review also discusses possible mechanisms of the harmful influence of inflammation on HSCs, including inflammatory abrasion of the number and the function of HSCs. We also discuss chronic and acute inflammation. Cytokines, cellular immunity, and niche factors likely to be disturbed in CAR-T therapy are highlighted factors with possible contributions to post-CAR-T hematotoxicity.

Functional Roles of Connexins and Gap Junctions in Osteo-Chondral Cellular Components

Gap junctions (GJs) formed by connexins (Cxs) play an important role in the intercellular communication within most body tissues. In this paper, we focus on GJs and Cxs present in skeletal tissues. Cx43 is the most expressed connexin, participating in the formation of both GJs for intercellular communication and hemichannels (HCs) for communication with the external environment. Through GJs in long dendritic-like cytoplasmic processes, osteocytes embedded in deep lacunae are able to form a functional syncytium not only with neighboring osteocytes but also with bone cells located at the bone surface, despite the surrounding mineralized matrix. The functional syncytium allows a coordinated cell activity through the wide propagation of calcium waves, nutrients and anabolic and/or catabolic factors. Acting as mechanosensors, osteocytes are able to transduce mechanical stimuli into biological signals that spread through the syncytium to orchestrate bone remodeling. The fundamental role of Cxs and GJs is confirmed by a plethora of investigations that have highlighted how up- and downregulation of Cxs and GJs critically influence skeletal development and cartilage functions. A better knowledge of GJ and Cx mechanisms in physiological and pathological conditions might help in developing therapeutic approaches aimed at the treatment of human skeletal system disorders.

Robo4 inhibits gamma radiation-induced permeability of a murine microvascular endothelial cell by regulating the junctions

BACKGROUND

Hematopoietic stem cell transplantation involves irradiation preconditioning which causes bone marrow endothelial cell dysfunction. While much emphasis is on the reconstitution of hematopoietic stem cells in the bone marrow microenvironment, endothelial cell preservation is indispensable to overcome the preconditioning damages. This study aims to ascertain the role of Roundabout 4 (Robo4) in regulating irradiation-induced damage to the endothelium.

METHODS

Microvascular endothelial cells were treated with γ-radiation to establish an endothelial cell injury model. Robo4 expression in the endothelial cells was manipulated employing lentiviral-mediated RNAi and gene overexpression technology before irradiation treatment. The permeability of endothelial cells was measured using qPCR, immunocytochemistry, and immunoblotting to analyze the effect on the expression and distribution of junctional molecules, adherens junctions, tight junctions, and gap junctions. Using Transwell endothelial monolayer staining, FITC-Dextran permeability, and gap junction-mediated intercellular communication (GJIC) assays, we determined the changes in endothelial functions after Robo4 gene manipulation and irradiation. Moreover, we measured the proportion of CD31 expression in endothelial cells by flow cytometry. We analyzed variations between two or multiple groups using Student's t-tests and ANOVA.

RESULTS

Ionizing radiation upregulates Robo4 expression but disrupts endothelial junctional molecules. Robo4 deletion causes further degradation of endothelial junctions hence increasing the permeability of the endothelial cell monolayer. Robo4 knockdown in microvascular endothelial cells increases the degradation and delocalization of ZO-1, PECAM-1, occludin, and claudin-5 molecules after irradiation. Conversely, connexin 43 expression increases after silencing Robo4 in endothelial cells to induce permeability but are readily destroyed when exposed to 10 Gy of gamma radiation. Also, Robo4 knockdown enhances Y731-VE-cadherin phosphorylation leading to the depletion and destabilization of VE-cadherin at the endothelial junctions following irradiation. However, Robo4 overexpression mitigates irradiation-induced degradation of tight junctional proteins and stabilizes claudin-5 and ZO-1 distribution. Finally, the enhanced expression of Robo4 ameliorates the irradiation-induced depletion of VE-cadherin and connexin 43, improves the integrity of microvascular endothelial cell junctions, and decreases permeability.

CONCLUSION

This study reveals that Robo4 maintains microvascular integrity after radiation preconditioning treatment by regulating endothelial permeability and protecting endothelial functions. Our results also provided a potential mechanism to repair the bone marrow vascular niche after irradiation by modulating Robo4 expression.

A biomimetic nanocomposite with enzyme-like activities and CXCR4 antagonism efficiently enhances the therapeutic efficacy of acute myeloid leukemia

Despite the progress made to improve therapeutic outcomes for acute myeloid leukemia (AML), many unmet clinical needs remain to be resolved. Unlike existing anti-AML strategies, here we developed a biomimetic nanocomposite to efficiently eliminate the leukemia cells in the bone marrow and prevent the homing of AML. To fulfill our design, the ultra-small nanozyme was conjugated onto the surface of an oxygen-carrying nanoparticle, which was further coated with bone marrow stromal cell membrane. After entering the blood, this biomimetic nanocomposite got actively internalized by the leukemia cells in the blood and released the loaded chemotherapeutics and nanozyme inside the leukemia cells to achieve a synergistic antitumor efficacy. Meanwhile, the adhesive properties of the stromal cell membrane enabled the nanocomposite to home to the bone marrow, where the nanocomposite effectively killed the retained leukemia cells. More importantly, the biomimetic cell membrane also acted as a CXCR4 antagonism to block the CXCR4/CXCL12-mediated homing of leukemia cells to the bone marrow and infiltration to other organs like the liver and spleen. In conclusion, this proof-of-concept study demonstrated that our designed platform effectively kills leukemia cells while preventing their infiltration, thus providing a promising prospect for resolving the clinical challenges in current AML treatment.

The role of astrocytes in neuropathic pain

Neuropathic pain, whose symptoms are characterized by spontaneous and irritation-induced painful sensations, is a condition that poses a global burden. Numerous neurotransmitters and other chemicals play a role in the emergence and maintenance of neuropathic pain, which is strongly correlated with common clinical challenges, such as chronic pain and depression. However, the mechanism underlying its occurrence and development has not yet been fully elucidated, thus rendering the use of traditional painkillers, such as non-steroidal anti-inflammatory medications and opioids, relatively ineffective in its treatment. Astrocytes, which are abundant and occupy the largest volume in the central nervous system, contribute to physiological and pathological situations. In recent years, an increasing number of researchers have claimed that astrocytes contribute indispensably to the occurrence and progression of neuropathic pain. The activation of reactive astrocytes involves a variety of signal transduction mechanisms and molecules. Signal molecules in cells, including intracellular kinases, channels, receptors, and transcription factors, tend to play a role in regulating post-injury pain once they exhibit pathological changes. In addition, astrocytes regulate neuropathic pain by releasing a series of mediators of different molecular weights, actively participating in the regulation of neurons and synapses, which are associated with the onset and general maintenance of neuropathic pain. This review summarizes the progress made in elucidating the mechanism underlying the involvement of astrocytes in neuropathic pain regulation.

Arteannuin B Enhances the Effectiveness of Cisplatin in Non-Small Cell Lung Cancer by Regulating Connexin 43 and MAPK Pathway

Cisplatin (DDP)-based chemotherapy is the first-line regimen for advanced non-small cell lung cancer (NSCLC) patients. However, advanced NSCLC patients may have innate resistance to DDP or develop resistance during DDP treatment. We investigated a natural compound, arteannuin B (Art B), for its potential effects on DDP resistance in NSCLC. Art B was isolated from Artemisia annua by chromatographic purification and spectral elucidation. The activities of Art B on DDP-mediated effects were examined using in vitro and in vivo assays. We observed significant correlations in T stage, clinical stage, chemotherapy resistance and poor survival of NSCLC patients with low Cx43 expression. Art B enhanced the effectiveness of cisplatin by increasing Cx43 expression in normal and DDP-resistant NSCLC cells. Art B also increased DDP uptake through up-regulating Cx43. The combination of DDP and Art B showed better therapeutic effect than individual treatments both in vitro and in vivo. Art B increased intracellular Fe[Formula: see text] level, promoted calcium influx, and activated gap junction and MAPK pathways, which might contribute to Art B-mediated effects. Art B may serve as a new drug candidate to enhance the antitumor effect of DDP on NSCLC.

Correlations Between the Expression of Stromal Cell Activation Related Biomarkers, L-NGFR, Phospho-ERK1-2 and CXCL12, and Primary Myelofibrosis Progression

In myelofibrosis, pathologically enhanced extracellular matrix production due to aberrant cytokine signalling and clonal megakaryocyte functions result(s) in impaired hemopoiesis. Disease progression is still determined by detecting reticulin and collagen fibrosis with Gomori’s silver impregnation. Here, we tested whether the expression growth related biomarkers L-NGFR/CD271, phospho-ERK1-2 and CXCL12 can be linked to the functional activation of bone marrow stromal cells during primary myelofibrosis progression. Immunoscores for all tested biomarkers showed varying strength of positive statistical correlation with the silver impregnation based myelofibrosis grades. The intimate relationship between spindle shaped stromal cells positive for all three markers and aberrant megakaryocytes was likely to reflect their functional cooperation. L-NGFR reaction was restricted to bone marrow stromal cells and revealed the whole length of their processes. Also, L-NGFR positive cells showed the most intersections, the best statistical correlations with myelofibrosis grades and the strongest interrater agreements. CXCL12 reaction highlighted stromal cell bodies and a weak extracellular staining in line with its constitutive release. Phospho-ERK1-2 reaction showed a similar pattern to CXCL12 in stromal cells with an additional nuclear staining in agreement with its role as a transcription factor. Both p-ERK1-2 and CXCL12 were also expressed at a moderate level in sinus endothelial cells. Connexin 43 gap junction communication channels, known to be required for CXCL12 release to maintain stem cell niche, were also expressed progressively in the myelofibrotic stromal network as a support of compartmental functions. Our results suggest that, diverse growth related pathways are activated in the functionally coupled bone marrow stromal cells during myelofibrosis progression. L-NGFR expression can be a useful biological marker of stromal cell activation which deserves diagnostic consideration for complementing Gomori’s silver impregnation.

Molecular Systems Architecture of Interactome in the Acute Myeloid Leukemia Microenvironment

A molecular systems architecture is presented for acute myeloid leukemia (AML) to provide a framework for organizing the complexity of biomolecular interactions. AML is a multifactorial disease resulting from impaired differentiation and increased proliferation of hematopoietic precursor cells involving genetic mutations, signaling pathways related to the cancer cell genetics, and molecular interactions between the cancer cell and the tumor microenvironment, including endothelial cells, fibroblasts, myeloid-derived suppressor cells, bone marrow stromal cells, and immune cells (e.g., T-regs, T-helper 1 cells, T-helper 17 cells, T-effector cells, natural killer cells, and dendritic cells). This molecular systems architecture provides a layered understanding of intra- and inter-cellular interactions in the AML cancer cell and the cells in the stromal microenvironment. The molecular systems architecture may be utilized for target identification and the discovery of single and combination therapeutics and strategies to treat AML.

Specialized Intercellular Communications via Tunnelling Nanotubes in Acute and Chronic Leukemia

Simple Summary

Tunneling nanotubes (TNTs) are cytoplasmic channels which regulate the contacts between cells and allow the transfer of several elements, including ions, mitochondria, microvesicles, exosomes, lysosomes, proteins, and microRNAs. Through this transport, TNTs are implicated in different physiological and pathological phenomena, such as immune response, cell proliferation and differentiation, embryogenesis, programmed cell death, and angiogenesis. TNTs can promote cancer progression, transferring substances capable of altering apoptotic dynamics, modifying the metabolism and energy balance, inducing changes in immunosurveillance, or affecting the response to chemotherapy. In this review, we evaluated their influence on hematologic malignancies’ progression and resistance to therapies, focusing on acute and chronic myeloid and acute lymphoid leukemia.

Abstract

Effectual cell-to-cell communication is essential to the development and differentiation of organisms, the preservation of tissue tasks, and the synchronization of their different physiological actions, but also to the proliferation and metastasis of tumor cells. Tunneling nanotubes (TNTs) are membrane-enclosed tubular connections between cells that carry a multiplicity of cellular loads, such as exosomes, non-coding RNAs, mitochondria, and proteins, and they have been identified as the main participants in healthy and tumoral cell communication. TNTs have been described in numerous tumors in in vitro, ex vivo, and in vivo models favoring the onset and progression of tumors. Tumor cells utilize TNT-like membranous channels to transfer information between themselves or with the tumoral milieu. As a result, tumor cells attain novel capabilities, such as the increased capacity of metastasis, metabolic plasticity, angiogenic aptitude, and chemoresistance, promoting tumor severity. Here, we review the morphological and operational characteristics of TNTs and their influence on hematologic malignancies’ progression and resistance to therapies, focusing on acute and chronic myeloid and acute lymphoid leukemia. Finally, we examine the prospects and challenges for TNTs as a therapeutic approach for hematologic diseases by examining the development of efficient and safe drugs targeting TNTs.

CXCL12/CXCR4 axis supports mitochondrial trafficking in tumor myeloma microenvironment

Mesenchymal stromal cells (MSCs) within the protective microenvironment of multiple myeloma (MM) promote tumor growth, confer chemoresistance and support metabolic needs of plasma cells (PCs) even transferring mitochondria. In this scenario, heterocellular communication and dysregulation of critical signaling axes are among the major contributors to progression and treatment failure. Here, we report that myeloma MSCs have decreased reliance on mitochondrial metabolism as compared to healthy MSCs and increased tendency to deliver mitochondria to MM cells, suggesting that this intercellular exchange between PCs and stromal cells can be consider part of MSC pro-tumorigenic phenotype. Interestingly, we also showed that PCs promoted expression of connexin 43 (CX43) in MSCs leading to CXCL12 activation and stimulation of its receptor CXCR4 on MM cells favoring protumor mitochondrial transfer. Consistently, we observed that selective inhibition of CXCR4 by plerixafor resulted in a significant reduction of mitochondria trafficking. Moreover, intracellular expression of CXCR4 in myeloma PCs from BM biopsy specimens demonstrated higher CXCR4 colocalization with CD138+ cells of non-responder patients to bortezomib compared with responder patients, suggesting that CXCR4 mediated chemoresistance in MM. Taken together, our data demonstrated that CXCL12/CXCR4 axis mediates intercellular coupling thus suggesting that the myeloma niche may be exploited as a target to improve and develop therapeutic approaches.

TGF-β1 potentiates Vγ9Vδ2 T cell adoptive immunotherapy of cancer

Despite its role in cancer surveillance, adoptive immunotherapy using γδ T cells has achieved limited efficacy. To enhance trafficking to bone marrow, circulating Vγ9Vδ2 T cells are expanded in serum-free medium containing TGF-β1 and IL-2 (γδ[T2] cells) or medium containing IL-2 alone (γδ[2] cells, as the control). Unexpectedly, the yield and viability of γδ[T2] cells are also increased by TGF-β1, when compared to γδ[2] controls. γδ[T2] cells are less differentiated and yet display increased cytolytic activity, cytokine release, and antitumor activity in several leukemic and solid tumor models. Efficacy is further enhanced by cancer cell sensitization using aminobisphosphonates or Ara-C. A number of contributory effects of TGF-β are described, including prostaglandin E2 receptor downmodulation, TGF-β insensitivity, and upregulated integrin activity. Biological relevance is supported by the identification of a favorable γδ[T2] signature in acute myeloid leukemia (AML). Given their enhanced therapeutic activity and compatibility with allogeneic use, γδ[T2] cells warrant evaluation in cancer immunotherapy.

Connexin channels modulation in pathophysiology and treatment of immune and inflammatory disorders

Connexin-mediated intercellular communication mechanisms include bidirectional cell-to-cell coupling by gap junctions and release/influx of molecules by hemichannels. These intercellular communications have relevant roles in numerous immune system activities. Here, we review the current knowledge about the function of connexin channels, mainly those formed by connexin-43, on immunity and inflammation. Focusing on those evidence that support the design and development of therapeutic tools to modulate connexin expression and/or channel activities with treatment potential for infections, wounds, cancer, and other inflammatory conditions.

Quantitative Evaluation of Cardiac Cell Interactions and Responses to Cyclic Strain

The heart has a dynamic mechanical environment contributed by its unique cellular composition and the resultant complex tissue structure. In pathological heart tissue, both the mechanics and cell composition can change and influence each other. As a result, the interplay between the cell phenotype and mechanical stimulation needs to be considered to understand the biophysical cell interactions and organization in healthy and diseased myocardium. In this work, we hypothesized that the overall tissue organization is controlled by varying densities of cardiomyocytes and fibroblasts in the heart. In order to test this hypothesis, we utilized a combination of mechanical strain, co-cultures of different cell types, and inhibitory drugs that block intercellular junction formation. To accomplish this, an image analysis pipeline was developed to automatically measure cell type-specific organization relative to the stretch direction. The results indicated that cardiac cell type-specific densities influence the overall organization of heart tissue such that it is possible to model healthy and fibrotic heart tissue in vitro. This study provides insight into how to mimic the dynamic mechanical environment of the heart in engineered tissue as well as providing valuable information about the process of cardiac remodeling and repair in diseased hearts.

Patient-Derived Bone Marrow Spheroids Reveal Leukemia-Initiating Cells Supported by Mesenchymal Hypoxic Niches in Pediatric B-ALL

B-cell acute lymphoblastic leukemia (B-ALL) results from the expansion of malignant lymphoid precursors within the bone marrow (BM), where hematopoietic niches and microenvironmental signals provide leukemia-initiating cells (LICs) the conditions to survive, proliferate, initiate disease, and relapse. Normal and malignant lymphopoiesis are highly dependent on the BM microenvironment, particularly on CXCL12-abundant Reticular (CAR) cells, which provide a niche for maintenance of primitive cells. During B-ALL, leukemic cells hijack BM niches, creating a proinflammatory milieu incompetent to support normal hematopoiesis but favoring leukemic proliferation. Although the lack of a phenotypic stem cell hierarchy is apparent in B-ALL, LICs are a rare and quiescent population potentially responsible for chemoresistance and relapse. Here, we developed novel patient-derived leukemia spheroids (PDLS), an ex vivo avatar model, from mesenchymal stromal cells (MSCs) and primary B-ALL cells, to mimic specialized niche structures and cell-to-cell intercommunication promoting normal and malignant hematopoiesis in pediatric B-ALL. 3D MSC spheroids can recapitulate CAR niche-like hypoxic structures that produce high levels of CXCL10 and CXCL11. We found that PDLS were preferentially enriched with leukemia cells displaying functional properties of LICs, such as quiescence, low reactive oxygen species, drug resistance, high engraftment in immunodeficient mice, and long-term leukemogenesis. Moreover, the combination of PDLS and patient-derived xenografts confirmed a microenvironment-driven hierarchy in their leukemic potential. Importantly, transcriptional profiles of MSC derived from primary patient samples revealed two unique signatures (1), a CXCL12low inflammatory and leukemia expansion (ILE)-like niche, that likely supports leukemic burden, and (2) a CXCL11hi immune-suppressive and leukemia-initiating cell (SLIC)-like niche, where LICs are likely sustained. Interestingly, the CXCL11+ hypoxic zones were recapitulated within the PDLS that are capable of supporting LIC functions. Taken together, we have implemented a novel PDLS system that enriches and supports leukemia cells with stem cell features driven by CXCL11+ MSCs within hypoxic microenvironments capable of recapitulating key features, such as tumor reemergence after exposure to chemotherapy and tumor initiation. This system represents a unique opportunity for designing ex vivo personalized avatars for B-ALL patients to evaluate their own LIC pathobiology and drug sensitivity in the context of the tumor microenvironment.

New insights into neuropeptides regulation of immune system and hemopoiesis: effects on hematologic malignancies

Several neurotransmitters and neuropeptides were reported to join to or to cooperate with different cells of the immune system, bone marrow, and peripheral cells and numerous data support that neuroactive molecules might control immune system activity and hemopoiesis operating on lymphoid organs, and the primary hematopoietic unit, the hematopoietic niche. Furthermore, many compounds seem to be able to take part to the leukemogenesis and lymphomagenesis process, and in the onset of multiple myeloma. In this review, we will assess the possibility that neurotransmitters and neuropeptides may have a role in the onset of haematological neoplasms, may affect the response to treatment or may represent a useful starting point for a new therapeutic approach. More in vivo investigations are needed to evaluate neuropeptide's role in haematological malignancies and the possible utilization as an antitumor therapeutic target. Comprehending the effect of the pharmacological administration of neuropeptide modulators on hematologic malignancies opens up new possibilities in curing clonal hematologic diseases to achieve more satisfactory outcomes.

Connexins in the development and physiology of stem cells

Connexins (Cxs) form gap junction (GJ) channels linking vertebrate cells. During embryogenesis, Cxs are expressed as early as the 4-8 cell stage. As cells differentiate into pluripotent stem cells (PSCs) and during gastrulation, the Cx expression pattern is adapted. Knockdown of Cx43 and Cx45 does not interfere with embryogenic development until the blastula stage, questioning the role of Cxs in PSC physiology and development. Studies in cultivated and induced PSCs (iPSCs) showed that Cx43 is essential for the maintenance of self-renewal and the expression of pluripotency markers. It was found that the role of Cxs in PSCs is more related to regulation of transcription or cell-cell adherence than to formation of GJ channels. Furthermore, a crucial role of Cxs for the self-renewal and differentiation was shown in cultivated adult mesenchymal stem cells. This review aims to highlight aspects that link Cxs to the function and physiology of stem cell development.

Bone fracture healing: perspectives according to molecular basis

Fractures have a great impact on health all around the world and with fracture healing optimization; this problem could be resolved partially. To make a practical contribution to this issue, the knowledge of bone tissue, cellularity, and metabolism is essential, especially cytoskeletal architecture and its transformations according to external pressures. Special physical and chemical characteristics of the extracellular matrix (ECM) allow the transmission of mechanical stimuli from outside the cell to the plasmatic membrane. The osteocyte cytoskeleton is conformed by a complex network of actin and microtubules combined with crosslinker proteins like vinculin and fimbrin, connecting and transmitting outside stimuli through EMC to cytoplasm. Herein, critical signaling pathways like Cx43-depending ones, MAPK/ERK, Wnt, YAP/TAZ, Rho-ROCK, and others are activated due to mechanical stimuli, resulting in osteocyte cytoskeletal changes and ECM remodeling, altering the tissue and, therefore, the bone. In recent years, the osteocyte has gained more interest and value in relation to bone homeostasis as a great coordinator of other cell populations, thanks to its unique functions. By integrating the latest advances in relation to intracellular signaling pathways, mechanotransmission system of the osteocyte and bone tissue engineering, there are promising experimental strategies, while some are ready for clinical trials. This work aims to show clearly and precisely the integration between cytoskeleton and main molecular pathways in relation to mechanotransmission mechanism in osteocytes, and the use of this theoretical knowledge in therapeutic tools for bone fracture healing.

Bone marrow regeneration requires mitochondrial transfer from donor Cx43-expressing hematopoietic progenitors to stroma

The fate of hematopoietic stem and progenitor cells (HSPC) is tightly regulated by their bone marrow (BM) microenvironment (ME). BM transplantation (BMT) frequently requires irradiation preconditioning to ablate endogenous hematopoietic cells. Whether the stromal ME is damaged and how it recovers after irradiation is unknown. We report that BM mesenchymal stromal cells (MSC) undergo massive damage to their mitochondrial function after irradiation. Donor healthy HSPC transfer functional mitochondria to the stromal ME, thus improving mitochondria activity in recipient MSC. Mitochondrial transfer to MSC is cell-contact dependent and mediated by HSPC connexin-43 (Cx43). Hematopoietic Cx43-deficient chimeric mice show reduced mitochondria transfer, which was rescued upon re-expression of Cx43 in HSPC or culture with isolated mitochondria from Cx43 deficient HSPCs. Increased intracellular adenosine triphosphate levels activate the purinergic receptor P2RX7 and lead to reduced activity of adenosine 5'-monophosphate-activated protein kinase (AMPK) in HSPC, dramatically increasing mitochondria transfer to BM MSC. Host stromal ME recovery and donor HSPC engraftment were augmented after mitochondria transfer. Deficiency of Cx43 delayed mesenchymal and osteogenic regeneration while in vivo AMPK inhibition increased stromal recovery. As a consequence, the hematopoietic compartment reconstitution was improved because of the recovery of the supportive stromal ME. Our findings demonstrate that healthy donor HSPC not only reconstitute the hematopoietic system after transplantation, but also support and induce the metabolic recovery of their irradiated, damaged ME via mitochondria transfer. Understanding the mechanisms regulating stromal recovery after myeloablative stress are of high clinical interest to optimize BMT procedures and underscore the importance of accessory, non-HSC to accelerate hematopoietic engraftment.

CXCR4 promotes B cell viability by the cooperation of nuclear factor (erythroid-derived 2)-like 2 and hypoxia-inducible factor-1α under hypoxic conditions

B cells that interact with T cells play a role in regulating the defense function by producing antibodies and inflammatory cytokines. C-X-C chemokine receptor type 4 (CXCR4) is a specific receptor for stromal cell-derived factor 1 (SDF-1) that controls various B cell functions. Here, we investigated whether CXCR4 regulates B cell viability by inducing hypoxia-inducible factor (HIF)-1α and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) under a hypoxic condition in WiL2-NS human B cells. Nrf2 and CXCR4 expressions increased significantly when WiL2-NS cells were incubated under a hypoxic condition. Interfering with CXCR4 expression using CXCR4-siRNA inhibited cell viability. CXCR4 expression also decreased after treatment with a HIF inhibitor under the hypoxic condition, leading to inhibited cell viability. Increased reactive oxygen species (ROS) levels and the expression of HIF-1α and Nrf2 decreased under the hypoxic condition following incubation with N-acetylcysteine, a ROS scavenger, which was associated with a decrease in CXCR4 expression. CXCR4 expression was augmented by overexpressing Nrf2 after transfecting the pcDNA3.1-Nrf2 plasmid. CXCR4 expression decreased and HIF-1α accumulation decreased when Nrf2 was inhibited by doxycycline in tet-shNrf2-expressed stable cells. Nrf2 or HIF-1α bound from -718 to -561 of the CXCR4 gene promoter as judged by a chromatin immunoprecipitation assay. Taken together, these data show that B cell viability under a hypoxic condition could be regulated by CXCR4 expression through binding of HIF-1α and Nrf2 to the CXCR4 gene promoter cooperatively. These results suggest that CXCR4 could be an additional therapeutic target to control B cells with roles at disease sites under hypoxic conditions.

Mitochondria Transfer in Bone Marrow Hematopoietic Activity

Purpose of Review

The well-established crosstalk between hematopoietic stem cells (HSC) and bone marrow (BM) microenvironment is critical for the homeostasis and hematopoietic regeneration in response to blood formation emergencies. Past decade has witnessed that the intercellular communication mediated by the transfer of cytoplasmic material and organelles between cells can regenerate and/or repair the damaged cells. Mitochondria have recently emerged as a potential regulator of HSC fate. This review intends to discuss recent advances in the understanding of the mitochondrial dynamics, specifically focused on the role of mitochondrial transfer, in the maintenance of HSC activity with clear implications in stem cell transplantation and regenerative medicine.

Recent Findings

HSC are highly heterogeneous in their mitochondrial metabolism, and the quiescence and potency of HSC depend on the status of mitochondrial dynamics and the clearance of damaged mitochondria. Recent evidence has shown that in stress response, BM stromal cells transfer healthy mitochondria to HSC, facilitate HSC bioenergetics shift towards oxidative phosphorylation, and subsequently stimulate leukocyte expansion. Furthermore, metabolic rewiring following mitochondria transfer from HSPC to BM stromal cells likely to repair the damaged BM niche and accelerate limiting HSC transplantation post myeloablative conditioning.

Alterations of 5-hydroxymethylation in circulating cell-free DNA reflect molecular distinctions of subtypes of non-Hodgkin lymphoma

The 5-methylcytosines (5mC) have been implicated in the pathogenesis of diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL). However, the role of 5-hydroxymethylcytosines (5hmC) that are generated from 5mC through active demethylation, in lymphomagenesis is unknown. We profiled genome-wide 5hmC in circulating cell-free DNA (cfDNA) from 73 newly diagnosed patients with DLBCL and FL. We identified 294 differentially modified genes between DLBCL and FL. The differential 5hmC in the DLBCL/FL-differentiating genes co-localized with enhancer marks H3K4me1 and H3K27ac. A four-gene panel (CNN2, HMG20B, ACRBP, IZUMO1) robustly represented the overall 5hmC modification pattern that distinguished FL from DLBCL with an area under curve of 88.5% in the testing set. The median 5hmC modification levels in signature genes showed potential for separating patients for risk of all-cause mortality. This study provides evidence that genome-wide 5hmC profiles in cfDNA differ between DLBCL and FL and could be exploited as a non-invasive approach.

Decreased blood vessel density and endothelial cell subset dynamics during ageing of the endocrine system

Age-associated alterations of the hormone-secreting endocrine system cause organ dysfunction and disease states. However, the cell biology of endocrine tissue ageing remains poorly understood. Here, we perform comparative 3D imaging to understand age-related perturbations of the endothelial cell (EC) compartment in endocrine glands. Datasets of a wide range of markers highlight a decline in capillary and artery numbers, but not of perivascular cells in pancreas, testis and thyroid gland, with age in mice and humans. Further, angiogenesis and β-cell expansion in the pancreas are coupled by a distinct age-dependent subset of ECs. While this EC subpopulation supports pancreatic β cells, it declines during ageing concomitant with increased expression of the gap junction protein Gja1. EC-specific ablation of Gja1 restores β-cell expansion in the aged pancreas. These results provide a proof of concept for understanding age-related vascular changes and imply that therapeutic targeting of blood vessels may restore aged endocrine tissue function. This comprehensive data atlas offers over > 1,000 multicolour volumes for exploration and research in endocrinology, ageing, matrix and vascular biology.

Cytochrome P4501B1 in bone marrow is co-expressed with key markers of mesenchymal stem cells. BMS2 cell line models PAH disruption of bone marrow niche development functions

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants that are metabolized to carcinogenic dihydrodiol epoxides (PAHDE) by cytochrome P450 1B1 (CYP1B1). This metabolism occurs in bone marrow (BM) mesenchymal stem cells (MSC), which sustain hematopoietic stem and progenitor cells (HSPC). In BM, CYP1B1-mediated metabolism of 7, 12-dimethylbenz[a]anthracene (DMBA) suppresses HSPC colony formation within 6 h, whereas benzo(a)pyrene (BP) generates protective cytokines. MSC, enriched from adherent BM cells, yielded the bone marrow stromal, BMS2, cell line. These cells express elevated basal CYP1B1 that scarcely responds to Ah receptor (AhR) inducers. BMS2 cells exhibit extensive transcriptome overlap with leptin receptor positive mesenchymal stem cells (Lepr+ MSC) that control the hematopoietic niche. The overlap includes CYP1B1 and the expression of HSPC regulatory factors (Ebf3, Cxcl12, Kitl, Csf1 and Gas6). MSC are large, adherent fibroblasts that sequester small HSPC and macrophage in the BM niche (Graphic abstract). High basal CYP1B1 expression in BMS2 cells derives from interactions between the Ah-receptor enhancer and proximal promoter SP1 complexes, boosted by autocrine signaling. PAH effects on BMS2 cells model Lepr+MSC niche activity. CYP1B1 metabolizes DMBA to PAHDE, producing p53-mediated mRNA increases, long after the in vivo HSPC suppression. Faster, direct p53 effects, favored by stem cells, remain possible PAHDE targets. However, HSPC regulatory factors remained unresponsive. BP is less toxic in BMS2 cells, but, in BM, CYP1A1 metabolism stimulates macrophage cytokines (Il1b > Tnfa> Ifng) within 6 h. Although absent from BMS2 and Lepr+MSC, their receptors are highly expressed. The impact of this cytokine signaling in MSC remains to be determined.

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BMS2 and Lepr+MSC cells co-express CYP1B1 and 12 functional niche activity markers.

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CYP1B1 mRNA in BMS2 cells depends on activation of SP1 coupled to an AhR enhancer unit.

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DMBA metabolism by CYP1B1 activates p53 gene targets in BMS2 cells far more than BP.

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HSPC suppression by CYP1B1 generation of PAHDE requires rapid, non-genomic targets.

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BMS2 and Lepr+MSC share receptors activated by BP stimulation of macrophage cytokines.

Connexin-Mediated Signaling at the Immunological Synapse

The immunological synapse (IS) is an intercellular communication platform, organized at the contact site of two adjacent cells, where at least one is an immune cell. Functional IS formation is fundamental for the modulation of the most relevant immune system activities, such as T cell activation by antigen presenting cells and T cell/natural killer (NK) cell-mediated target cell (infected or cancer) killing. Extensive evidence suggests that connexins, in particular connexin-43 (Cx43) hemichannels and/or gap junctions, regulate signaling events in different types of IS. Although the underlying mechanisms are not fully understood, the current evidence suggests that Cx43 channels could act as facilitators for calcium ions, cyclic adenosine monophosphate, and/or adenosine triphosphate uptake and/or release at the interface of interacting cells. These second messengers have relevant roles in the IS signaling during dendritic cell-mediated T and NK cell activation, regulatory T cell-mediated immune suppression, and cytotoxic T lymphocyte or NK cell-mediated target tumor cell killing. Additionally, as the cytoplasmic C-terminus domain of Cx43 interacts with a plethora of proteins, Cx43 may act as scaffolds for integration of various regulatory proteins at the IS, as suggested by the high number of Cx43-interacting proteins that translocate at these cell-cell interface domains. In this review, we provide an updated overview and analysis on the role and possible underlying mechanisms of Cx43 in IS signaling.

Gap Junctions in the Bone Marrow Lympho-Hematopoietic Stem Cell Niche, Leukemia Progression, and Chemoresistance

Abstract: The crosstalk between hematopoietic stem cells (HSC) and bone marrow (BM) microenvironment is critical for homeostasis and hematopoietic regeneration in response to blood formation emergencies after injury, and has been associated with leukemia transformation and progression. Intercellular signals by the BM stromal cells in the form of cell-bound or secreted factors, or by physical interaction, regulate HSC localization, maintenance, and differentiation within increasingly defined BM HSC niches. Gap junctions (GJ) are comprised of arrays of membrane embedded channels formed by connexin proteins, and control crucial signaling functions, including the transfer of ions, small metabolites, and organelles to adjacent cells which affect intracellular mechanisms of signaling and autophagy. This review will discuss the role of GJ in both normal and leukemic hematopoiesis, and highlight some of the most novel approaches that may improve the efficacy of cytotoxic drugs. Connexin GJ channels exert both cell-intrinsic and cell-extrinsic effects on HSC and BM stromal cells, involved in regenerative hematopoiesis after myelosuppression, and represent an alternative system of cell communication through a combination of electrical and metabolic coupling as well as organelle transfer in the HSC niche. GJ intercellular communication (GJIC) in the HSC niche improves cellular bioenergetics, and rejuvenates damaged recipient cells. Unfortunately, they can also support leukemia proliferation and survival by creating leukemic niches that provide GJIC dependent energy sources and facilitate chemoresistance and relapse. The emergence of new strategies to disrupt self-reinforcing malignant niches and intercellular organelle exchange in leukemic niches, while at the same time conserving normal hematopoietic GJIC function, could synergize the effect of chemotherapy drugs in eradicating minimal residual disease. An improved understanding of the molecular basis of connexin regulation in normal and leukemic hematopoiesis is warranted for the re-establishment of normal hematopoiesis after chemotherapy.

Dynamic responses of the haematopoietic stem cell niche to diverse stresses

Adult haematopoietic stem cells (HSCs) mainly reside in the bone marrow, where stromal and haematopoietic cells regulate their function. The steady state HSC niche has been extensively studied. In this Review, we focus on how bone marrow microenvironment components respond to different insults including inflammation, malignant haematopoiesis and chemotherapy. We highlight common and unique patterns among multiple cell types and their environment and discuss current limitations in our understanding of this complex and dynamic tissue.

Activated spinal astrocytes contribute to the later phase of carrageenan-induced prostatitis pain

Background

Prostatodynia is the main symptom of chronic prostatitis and the main reason that patients go to the hospital for treatment. Although a variety of factors, including inflammatory immune response, nervous system sensitization, and psychological factors, have been shown to play important roles in the induction and development of chronic pain in prostatitis, the underlying cause of chronic prostatodynia maintenance in prostatitis patients remains unclear.

Methods

A mouse model of chronic prostatitis induced by carrageenan injection was used. The von Frey test was used to measure pain behavior. The microglial and astrocyte activations were immunohistochemically demonstrated with antibodies against Iba1 and GFAP. The expression of cytokine or signaling pathway was detected by enzyme-linked immunosorbent assay (ELISA) and Western blotting.

Results

In this study, we provide several lines of evidence to demonstrate that activated spinal astrocytes contribute to the later phase (5 weeks after carrageenan injection) of carrageenan-induced prostatitis pain. First, activation of spinal astrocytes but not microglia was found in the spinal cord dorsal horn at 5 weeks. Second, intrathecal injection of the astroglial toxin L-2-Aminoadipate acid (L-AA) but not microglial inhibitor minocycline reduced mechanical allodynia at 5 weeks. Third, chronic prostatitis induced a profound and persistent upregulation of connexin-43 hemichannels in spinal astrocytes, and spinal injection of the connexin-43 inhibitor carbenoxolone (CBX) effectively reduced pain symptoms. Fourth, increased expression and release of chemokine C-X-C motif ligand 1 (CXCL1) in the spinal dorsal horn and intrathecal injection of a CXCL1 neutralizing antibody or the CXCR2 (a major receptor of CXCL1) antagonist SB225002 significantly reduced mechanical allodynia at 5 weeks.

Conclusions

In this study, we found that a novel mechanism of activated spinal astrocytes plays a crucial role in maintaining chronic prostatitis-induced persistent pain via connexin-43-regulated CXCL1 production and secretion.

Single-cell RNA sequencing reveals chemokine self-feeding of myeloma cells promotes extramedullary metastasis

In this study, we aimed to determine the mechanisms underlying the initial extramedullary translocation of myeloma cells from bone marrow into peripheral blood. We found that clonal circulating plasma cells (cPCs) are more frequently detected by flow cytometry in extramedullary plasmacytoma (EMP) patients and worsen their prognosis. It is technically much easier to collect single cPCs using FACS than it is to perform EMP biopsy. Therefore, combining EMP imaging with cPC detection may be a promising strategy for prognostic stratification. Here, using single-cell transcriptome analysis, we found that the chemokine CXCL12, a key molecule involved in CXCR4-dependent cell retention in the bone marrow, is abnormally upregulated in cPCs and might initially enable cPCs to evade bone marrow retention and translocate into the bloodstream.

Connexin43 is Dispensable for Early Stage Human Mesenchymal Stem Cell Adipogenic Differentiation But is Protective against Cell Senescence

In the last couple of decades, there has been a growing optimism surrounding the potential transformative use of human mesenchymal stem cells (MSCs) and human-induced pluripotent stem cells (iPSCs) for regenerative medicine and disease treatment. In order for this to occur, it is first essential to understand the mechanisms underpinning their cell-fate specification, which includes cell signaling via gap junctional intercellular communication. Here, we investigated the role of the prototypical gap junction protein, connexin43 (Cx43), in governing the differentiation of iPSCs into MSCs and MSC differentiation along the adipogenic lineage. We found that control iPSCs, as well as iPSCs derived from oculodentodigital dysplasia patient fibroblasts harboring a GJA1 (Cx43) gene mutation, successfully and efficiently differentiated into LipidTox and perilipin-positive cells, indicating cell differentiation along the adipogenic lineage. Furthermore, the complete CRISPR-Cas9 ablation of Cx43 from iPSCs did not prevent their differentiation into bona fide MSCs or pre-adipocytes, strongly suggesting that even though Cx43 expression is upregulated during adipogenesis, it is expendable. Interestingly, late passage Cx43-ablated MSCs senesced more quickly than control cells, resulting in failure to properly differentiate in vitro. We conclude that despite being upregulated during adipogenesis, Cx43 plays no detectable role in the early stages of human iPSC-derived MSC adipogenic differentiation. However, Cx43 may play a more impactful role in protecting MSCs from premature senescence.

Role of stem cells in fertility preservation: current insights

While improvements made in the field of cancer therapy allow high survival rates, gonadotoxicity of chemo- and radiotherapy can lead to infertility in male and female pre- and postpubertal patients. Clinical options to preserve fertility before starting gonadotoxic therapies by cryopreserving sperm or oocytes for future use with assisted reproductive technology (ART) are now applied worldwide. Cryopreservation of pre- and postpubertal ovarian tissue containing primordial follicles, though still considered experimental, has already led to the birth of healthy babies after autotransplantation and is performed in an increasing number of centers. For prepubertal boys who do not produce gametes ready for fertilization, cryopreservation of immature testicular tissue (ITT) containing spermatogonial stem cells may be proposed as an experimental strategy with the aim of restoring fertility. Based on achievements in nonhuman primates, autotransplantation of ITT or testicular cell suspensions appears promising to restore fertility of young cancer survivors. So far, whether in two- or three-dimensional culture systems, in vitro maturation of immature male and female gonadal cells or tissue has not demonstrated a capacity to produce safe gametes for ART. Recently, primordial germ cells have been generated from embryonic and induced pluripotent stem cells, but further investigations regarding efficiency and safety are needed. Transplantation of mesenchymal stem cells to improve the vascularization of gonadal tissue grafts, increase the colonization of transplanted cells, and restore the damaged somatic compartment could overcome the current limitations encountered with transplantation.

Biological Functions of Connexin43 Beyond Intercellular Communication

Connexin43 (Cx43) is commonly associated with direct cell-cell communication through gap junctions (GJs). However, recent groundbreaking studies have challenged this dogma, implicating Cx43 in other biological processes, such as transcription, metabolism, autophagy, and ion channel trafficking. How Cx43 participates in these processes remains largely unknown, although its high turnover rate, capacity to bind to myriad proteins, and the discovery of truncated isoforms of Cx43, ascribe to this protein unanticipated roles in chief processes that require fine-tuned regulation. Accordingly, Cx43 can be regarded as a central integrative hub to which diverse cues converge to be processed in a concerted manner. In this review, we examine the noncanonical roles of Cx43 and discuss the implications of these functions in human diseases and future therapeutic strategies.

The role of connexin43 in neuropathic pain induced by spinal cord injury

Neuropathic pain is caused by the damage or dysfunction of the nervous system. In many neuropathic pain models, there is an increase in the number of gap junction (GJ) channels, especially the upregulation of the expression of connexin43 (Cx43), leading to the secretion of various types of cytokines and involvement in the formation of neuropathic pain. GJs are widely distributed in mammalian organs and tissues, and Cx43 is the most abundant connexin (Cx) in mammals. Astrocytes are the most abundant glial cell type in the central nervous system (CNS), which mainly express Cx43. More importantly, GJs play an important role in regulating cell metabolism, signaling, and function. Many existing literatures showed that Cx43 plays an important role in the nervous system, especially in the CNS under normal and pathological conditions. However, many internal mechanisms have not yet been thoroughly explored. In this review, we summarized the current understanding of the role and association of Cx and pannexin channels in neuropathic pain, especially after spinal cord injury, as well as some of our own insights and thoughts which suggest that Cx43 may become an emerging therapeutic target for future neuropathic pain, bringing new hope to patients.

CCL22 controls immunity by promoting regulatory T cell communication with dendritic cells in lymph nodes

Rapp et al. demonstrate that dendritic cells in the lymph node secrete CCL22 to build cell–cell contacts with CCR4-expressing regulatory T cells, leading to immune suppression. Conversely, CCL22 deficiency results in enhanced T cell immunity, shown here in the setting of vaccination, cancer, and inflammatory disease.

Chemokines have crucial roles in organ development and orchestration of leukocyte migration. The chemokine CCL22 is expressed constitutively at high levels in the lymph node, but the functional significance of this expression is so far unknown. Studying a newly established CCL22-deficient mouse, we demonstrate that CCL22 expression by dendritic cells (DCs) promotes the formation of cell–cell contacts and interaction with regulatory T cells (T reg) through their CCR4 receptor. Vaccination of CCL22-deficient mice led to excessive T cell responses that were also observed when wild-type mice were vaccinated using CCL22-deficient DCs. Tumor-bearing mice with CCL22 deficiency showed prolonged survival upon vaccination, and further, CCL22-deficient mice had increased susceptibility to inflammatory disease. In conclusion, we identify the CCL22–CCR4 axis as an immune checkpoint that is crucial for the control of T cell immunity.

PI3K activation increases SDF-1 production and number of osteoclast precursors, and enhances SDF-1-mediated osteoclast precursor migration

Our previous studies showed that in a mouse model in which PI3K-AKT activation was increased (YF mice), osteoclast numbers and levels of SDF-1, a chemokine, were augmented. The purpose of this study was to delineate the role of PI3K activation in regulating SDF-1 production and examine whether SDF-1 can stimulate differentiation and/or migration of osteoclast precursors. Using flow cytometric analysis, we demonstrated that compared to wild type mice, bone marrow of YF mice had increased numbers of CXCL12 abundant reticular (CAR) cells, that are a major cell type responsible for producing SDF-1. At the molecular level, transcription factor specificity protein 1 (Sp1) induced an increased transcription of SDF-1 that was dependent on PI3K/AKT activation. YF mice also contained an increased number of osteoclast precursors, in which expression of CXCR4, a major receptor for SDF-1, was increased. SDF-1 did not induce differentiation of osteoclast precursors into mature osteoclasts; compared to cells derived from WT mice, cells obtained from YF mice were more responsive to SDF-1. In conclusion, we demonstrate that PI3K activation resulted in increased SDF-1, increased the number of osteoclast precursors, and enhanced osteoclast precursor migration in response to SDF-1.

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PI3K activation regulates the number of CAR cells in mouse bone marrow.

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PI3K activation regulates SDF-1/CXCL12 production by CAR cells in bone marrow.

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PI3K/AKT activation mediates transcription of SDF-1 by regulating transcription factor Sp1.

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SDF-1 enhances migration of osteoclast precursors via CXCR4.

Mesenchymal stem/stromal cell function in modulating cell death

Mesenchymal stem/stromal cells (MSCs) delivered as cell therapy to individuals with degenerative and/or inflammatory disorders can help improve organ features and resolve inflammation, as demonstrated in preclinical studies and to some extent in clinical studies. MSCs have trophic, homing/migration, and immunosuppression functions, with many benefits in therapeutics. MSC functions are thought to depend on the paracrine action of soluble factors and/or the expression of membrane-bound molecules, mostly belonging to the molecular class of adhesion molecules, chemokines, enzymes, growth factors, and interleukins. Cutting-edge studies underline bioactive exchanges, including that of ions, nucleic acids, proteins, and organelles transferred from MSCs to stressed cells, thereby improving the cells' survival and function. From this aspect, MSC death modulation function appears as a decisive biological function that could carry a significant part of the therapeutic effects of MSCs. Identifying the function and modes of actions of MSCs in modulating cell death may be exploited to enhance consistency and efficiency of cell therapy that is based on MSCs as medical treatment for degenerative and/or inflammatory diseases. Here, we review the essentials of MSC functions in modulating cell death in unfit cells, and its modes of actions based on current advances and outline the clinical implications.

Connexin Hemichannels in Astrocytes: Role in CNS Disorders

In the central nervous system (CNS), astrocytes form networks interconnected by gap junctions made from connexins of the subtypes Cx30 and Cx43. When unopposed by an adjoining hemichannel, astrocytic connexins can act as hemichannels to control the release of small molecules such as ATP and glutamate into the extracellular space. Accruing evidence indicates that astrocytic connexins are crucial for the coordination and maintenance of physiologic CNS activity. Here we provide an update on the role of astrocytic connexins in neurodegenerative disorders, glioma, and ischemia. In addition, we address the regulation of Cx43 in chronic pain.

The Role of Connexin-43 in the Inflammatory Process: A New Potential Therapy to Influence Keratitis

The studies outlined in this review highlight the relationship between inflammatory signaling molecules and connexin-43 (Cx43). Gap junction (GJ) channels and hemichannels (HCs) participate in the metabolic activity between intra- and extracellular space. Some ions and small molecules are exchanged from cell to cell or cell to extracellular space to affect the process of inflammation via GJ. We analyzed the effects of signaling molecules, such as innate immunity messengers, transcription factors, LPS, cytokine, inflammatory chemokines, and MMPs, on Cx43 expression during the inflammatory process. At the same time, we found that these signaling molecules play a critical role in the pathogenesis of keratitis. Thus, we assessed the function of Cx43 during inflammatory corneal disease. Corneal healing plays an essential role in the late stage of keratitis. We found that Cx43 is involved in wound healing. Studies have shown that the decrease of Cx43 can decrease the time of healing. We also report several Cx43 mimic peptides which can inhibit the activity of Cx43 Hc to mediate the releasing of adenosine triphosphate (ATP), which may in turn influence the inflammatory process.

Dual cholinergic signals regulate daily migration of hematopoietic stem cells and leukocytes

Hematopoietic stem and progenitor cells (HSPCs) and leukocytes circulate between the bone marrow (BM) and peripheral blood following circadian oscillations. Autonomic sympathetic noradrenergic signals have been shown to regulate HSPC and leukocyte trafficking, but the role of the cholinergic branch has remained unexplored. We have investigated the role of the cholinergic nervous system in the regulation of day/night traffic of HSPCs and leukocytes in mice. We show here that the autonomic cholinergic nervous system (including parasympathetic and sympathetic) dually regulates daily migration of HSPCs and leukocytes. At night, central parasympathetic cholinergic signals dampen sympathetic noradrenergic tone and decrease BM egress of HSPCs and leukocytes. However, during the daytime, derepressed sympathetic noradrenergic activity causes predominant BM egress of HSPCs and leukocytes via β3-adrenergic receptor. This egress is locally supported by light-triggered sympathetic cholinergic activity, which inhibits BM vascular cell adhesion and homing. In summary, central (parasympathetic) and local (sympathetic) cholinergic signals regulate day/night oscillations of circulating HSPCs and leukocytes. This study shows how both branches of the autonomic nervous system cooperate to orchestrate daily traffic of HSPCs and leukocytes.