'Green mice' as a source of ubiquitous green cells

Loss of mouse Y chromosome gene Zfy1 and Zfy2 leads to spermatogenesis impairment, sperm defects, and infertility

Using mice with Y chromosome deficiencies and supplementing Zfy transgenes, we, and others, have previously shown that the loss of Y chromosome Zfy1 and Zfy2 genes is associated with infertility and spermiogenic defects and that the addition of Zfy transgenes rescues these defects. In these past studies, the absence of Zfy was linked to the loss of other Y chromosome genes, which might have contributed to spermiogenic phenotypes. Here, we used CRISPR/Cas9 to specifically remove open reading frame of Zfy1, Zfy2, or both Zfy1 and Zfy2, and generated Zfy knockout (KO) and double knockout (DKO) mice. Zfy1 KO and Zfy2 KO mice were both fertile, but the latter had decreased litters size and sperm number, and sperm headshape abnormalities. Zfy DKO males were infertile and displayed severe spermatogenesis defects. Postmeiotic arrest largely prevented production of sperm and the few sperm that were produced all displayed gross headshape abnormalities and structural defects within head and tail. Infertility of Zfy DKO mice could be overcome by injection of spermatids or sperm directly to oocytes, and the resulting male offspring had the same spermiogenic phenotype as their fathers. The study is the first describing detailed phenotypic characterization of mice with the complete Zfy gene loss. It provides evidence supporting that the presence of at least one Zfy homolog is essential for male fertility and development of normal sperm functional in unassisted fertilization. The data also show that while the loss of Zfy1 is benign, the loss of Zfy2 is mildly detrimental for spermatogenesis.

Combined treatment of graft versus host disease using donor regulatory T cells and ruxolitinib

Donor derived regulatory T lymphocytes and the JAK1/2 kinase inhibitor ruxolitinib are currently being evaluated as therapeutic options in the treatment of chronic graft versus host disease (cGvHD). In this work, we aimed to determine if the combined use of both agents can exert a synergistic effect in the treatment of GvHD. For this purpose, we studied the effect of this combination both in vitro and in a GvHD mouse model. Our results show that ruxolitinib favors the ratio of thymic regulatory T cells to conventional T cells in culture, without affecting the suppressive capacity of these Treg. The combination of ruxolitinib with Treg showed a higher efficacy as compared to each single treatment alone in our GvHD mouse model in terms of GvHD incidence, severity and survival without hampering graft versus leukemia effect. This beneficial effect correlated with the detection in the bone marrow of recipient mice of the infused donor allogeneic Treg after the adoptive transfer.

Molecular and functional heterogeneity in dorsal and ventral oligodendrocyte progenitor cells of the mouse forebrain in response to DNA damage

In the developing mouse forebrain, temporally distinct waves of oligodendrocyte progenitor cells (OPCs) arise from different germinal zones and eventually populate either dorsal or ventral regions, where they present as transcriptionally and functionally equivalent cells. Despite that, developmental heterogeneity influences adult OPC responses upon demyelination. Here we show that accumulation of DNA damage due to ablation of citron-kinase or cisplatin treatment cell-autonomously disrupts OPC fate, resulting in cell death and senescence in the dorsal and ventral subsets, respectively. Such alternative fates are associated with distinct developmental origins of OPCs, and with a different activation of NRF2-mediated anti-oxidant responses. These data indicate that, upon injury, dorsal and ventral OPC subsets show functional and molecular diversity that can make them differentially vulnerable to pathological conditions associated with DNA damage.

Rasa3 deficiency minimally affects thrombopoiesis but promotes severe thrombocytopenia due to integrin-dependent platelet clearance

Platelet homeostasis is dependent on a tight regulation of both platelet production and clearance. The small GTPase Rap1 mediates platelet adhesion and hemostatic plug formation. However, Rap1 signaling is also critical for platelet homeostasis as both Rap1 deficiency and uninhibited Rap1 signaling lead to marked thrombocytopenia in mice. Here, we investigated the mechanism by which deficiency in Rasa3, a critical negative regulator of Rap1, causes macrothrombocytopenia in mice. Despite marked morphological and ultrastructural abnormalities, megakaryocytes in hypomorphic Rasa3hlb/hlb (R3hlb/hlb) or Rasa3-/- mice demonstrated robust proplatelet formation in vivo, suggesting that defective thrombopoiesis is not the main cause of thrombocytopenia. Rather, we observed that R3hlb/hlb platelets became trapped in the spleen marginal zone/red pulp interface, with evidence of platelet phagocytosis by macrophages. Clearance of mutant platelets was also observed in the liver, especially in splenectomized mice. Platelet count and platelet life span in Rasa3-mutant mice were restored by genetic or pharmacological approaches to inhibit the Rap1/talin1/αIIbβ3 integrin axis. A similar pattern of splenic clearance was observed in mice injected with anti-αIIbβ3 but not anti-glycoprotein Ibα platelet-depleting antibodies. In summary, we describe a potentially novel, integrin-based mechanism of platelet clearance that could be critical for our understanding of select inherited and acquired thrombocytopenias.

Transplantation of human iPSC-derived muscle stem cells in the diaphragm of Duchenne muscular dystrophy model mice

Duchenne muscular dystrophy (DMD) is an intractable genetic muscular disorder characterized by the loss of DYSTROPHIN. The restoration of DYSTROPHIN is expected to be a curative therapy for DMD. Because muscle stem cells (MuSCs) can regenerate damaged myofibers with full-length DYSTROPHIN in vivo, their transplantation is being explored as such a therapy. As for the transplanted cells, primary satellite cells have been considered, but donor shortage limits their clinical application. We previously developed a protocol that differentiates induced pluripotent stem cells (iPSCs) to MuSCs (iMuSCs). To ameliorate the respiratory function of DMD patients, cell transplantation to the diaphragm is necessary but difficult, because the diaphragm is thin and rapidly moves. In the present study, we explored the transplantation of iMuSCs into the diaphragm. First, we show direct cell injection into the diaphragm of mouse was feasible. Then, to enhance the engraftment of the transplanted cells in a rapidly moving diaphragm, we mixed polymer solutions of hyaluronic acid, alginate and gelatin to the cell suspension, finding a solution of 20% dissolved hyaluronic acid and 80% dissolved gelatin improved the engraftment. Thus, we established a method for cell transplantation into mouse diaphragm and show that an injectable hyaluronic acid-gelatin solution enables the engraftment of iMuSCs in the diaphragm.

The ischemic time window of ectopic endometrial tissue crucially determines its ability to develop into endometriotic lesions

Endometriosis develop from shed endometrial fragments via retrograde menstruation. This affects the survival, proliferation and vascularization of the tissue and its final ability to form endometriotic lesions. Within this study, uterine tissue samples from donor mice were precultivated for 24 h or 72 h to simulate avascular periods. Their morphology, microvessel density, apoptotic activity and expression of angiogenesis-related proteins were analyzed in vitro. The formation of endometriotic lesions in vivo was assessed after transplantation of precultivated uterine tissue samples to the abdominal wall and dorsal skinfold chambers by means of high-resolution ultrasound, intravital fluorescence microscopy, histology and immunohistochemistry. In vitro, 72-h-precultivated uterine tissue samples exhibit extensive areas of tissue necrosis and high numbers of apoptotic cells as well as a significantly reduced cell and microvessel density. These samples failed to develop into endometriotic lesions. In contrast, the 24-h-precultivated samples showed, that their early vascularization and growth in vivo was improved when compared to controls. This indicates that avascular periods have a strong impact on the survival of ectopic endometrial tissue and the chance for the development of endometriosis.

Better Outcomes with Intranigral versus Intrastriatal Cell Transplantation: Relevance for Parkinson’s Disease

Intrastriatal embryonic ventral mesencephalon grafts have been shown to integrate, survive, and reinnervate the host striatum in clinical settings and in animal models of Parkinson’s disease. However, this ectopic location does not restore the physiological loops of the nigrostriatal pathway and promotes only moderate behavioral benefits. Here, we performed a direct comparison of the potential benefits of intranigral versus intrastriatal grafts in animal models of Parkinson’s disease. We report that intranigral grafts promoted better survival of dopaminergic neurons and that only intranigral grafts induced recovery of fine motor skills and normalized cortico-striatal responses. The increase in the number of toxic activated glial cells in host tissue surrounding the intrastriatal graft, as well as within the graft, may be one of the causes of the increased cell death observed in the intrastriatal graft. Homotopic localization of the graft and the subsequent physiological cell rewiring of the basal ganglia may be a key factor in successful and beneficial cell transplantation procedures.

A phenotypic analysis of involucrin-mOVA mice following adoptive transfer of OVA-specific CD8+ T cells

To investigate the mechanism of autoimmunity and peripheral tolerance in the skin, several transgenic mouse strains expressing membrane-bound ovalbumin (mOVA) as an epidermal self-antigen under the control of keratinocyte-specific promotors, such as keratin 5 and keratin 14, were employed in combination with adoptive transfer of CD8⁺ T cells from OT-I mice (OT-I T cells) that recognize an ovalbumin-derived peptide. However, these strains showed bodyweight loss and required additional inflammatory stimuli, such as γ-irradiation and tape-stripping, to induce skin inflammation. In this study, we generated a mouse strain expressing mOVA under the control of human involucrin promoter (involucrin-mOVA mice). In contrast to previous strains, involucrin-mOVA mice spontaneously developed skin inflammation after the transfer of OT-I T cells in the absence of external stimuli without significant bodyweight loss. We focused on the skin infiltration process of OT-I T cells and found that transferred OT-I T cells accumulated around the hair follicles in the early phase of skin inflammation, and in the later phase, the skin inflammation spontaneously resolved despite the remaining OT-I T cells in the skin. Our involucrin-mOVA mice will provide a promising tool to investigate the pathogenesis and the tolerance mechanisms of cytotoxic skin autoimmunity.

Chronic spinal cord injury functionally repaired by direct implantation of encapsulated hair-follicle-associated pluripotent (HAP) stem cells in a mouse model: Potential for clinical regenerative medicine

Chronic spinal cord injury (SCI) is a highly debilitating and recalcitrant disease with limited treatment options. Although various stem cell types have shown some clinical efficacy for injury repair they have not for SCI. Hair-follicle-associated pluripotent (HAP) stem cells have been shown to differentiate into neurons, Schwan cells, beating cardiomyocytes and many other type of cells, and have effectively regenerated acute spinal cord injury in mouse models. In the present report, HAP stem cells from C57BL/6J mice, encapsulated in polyvinylidene fluoride membranes (PFM), were implanted into the severed thoracic spinal cord of C57BL/6J or athymic nude mice in the early chronic phase. After implantation, HAP stem cells differentiated to neurons, astrocytes and oligodendrocytes in the regenerated thoracic spinal cord of C57BL/6J and nude mice. Quantitative motor function analysis, with the Basso Mouse Scale for Locomotion (BMS) score, demonstrated a significant functional improvement in the HAP-stem-cell-implanted mice, compared to non-implanted mice. HAP stem cells have critical advantages over other stem cells: they do not develop teratomas; do not loose differentiation ability when cryopreserved and thus are bankable; are autologous, readily obtained from anyone; and do not require genetic manipulation. HAP stem cells therefore have greater clinical potential for SCI repair than induced pluripotent stem cells (iPSCs), neuronal stem cells (NSCs)/neural progenitor cells (NPCs) or embryonic stem cells (ESCs). The present report demonstrates future clinical potential of HAP-stem-cell repair of chronic spinal cord injury, currently a recalcitrant disease.

Integrative analysis of the 3D genome structure reveals that CTCF maintains the properties of mouse female germline stem cells

The three-dimensional configuration of the genome ensures cell type-specific gene expression profiles by placing genes and regulatory elements in close spatial proximity. Here, we used in situ high-throughput chromosome conformation (in situ Hi-C), RNA sequencing (RNA-seq) and chromatin immunoprecipitation sequencing (ChIP-seq) to characterize the high-order chromatin structure signature of female germline stem cells (FGSCs) and identify its regulating key factor based on the data-driven of multiple omics data. By comparison with pluripotent stem cells (PSCs), adult stem cells (ASCs), and somatic cells at three major levels of chromatin architecture, A/B compartments, topologically associating domains, and chromatin loops, the chromatin architecture of FGSCs was most similar to that of other ASCs and largely different from that of PSCs and somatic cells. After integrative analysis of the three-dimensional chromatin structure, active compartment-associating loops (aCALs) were identified as a signature of high-order chromatin organization in FGSCs, which revealed that CCCTC-binding factor was a major factor to maintain the properties of FGSCs through regulation of aCALs. We found FGSCs belong to ASCs at chromatin structure level and characterized aCALs as the high-order chromatin structure signature of FGSCs. Furthermore, CTCF was identified to play a key role in regulating aCALS to maintain the biological functions of FGSCs. These data provide a valuable resource for future studies of the features of chromatin organization in mammalian stem cells and further understanding of the fundamental characteristics of FGSCs.

EphA2 Affects Development of the Eye Lens Nucleus and the Gradient of Refractive Index

Purpose

Our studies in mouse eye lenses demonstrate that ephrin-A5 and EphA2 are needed for normal epithelial cells and lens transparency. We sought to determine whether EphA2 and ephrin-A5 are important for lens morphometrics, nucleus formation, and refractive index.

Methods

We performed tissue morphometric measurements, electron microscopy, Western blots, and interferometric measurements using an X-ray synchrotron beam source to measure the gradient of refractive index (GRIN) to compare mouse lenses with genetic disruption of EphA2 or ephrin-A5.

Results

Morphometric analysis revealed that although there is no change in the overall lens volume, there is a change in lens shape in both EphA2-/- lenses and ephrin-A5-/- lenses. Surprisingly, EphA2-/- lenses had small and soft lens nuclei different from hard lens nuclei of control lenses. SEM images revealed changes in cell morphology of EphA2-/- fiber cells close to the center of the lens. Inner EphA2-/- lens fibers had more pronounced tongue-and-groove interdigitations and formed globular membrane morphology only in the deepest layers of the lens nucleus. We did not observe nuclear defects in ephrin-A5-/- lenses. There was an overall decrease in magnitude of refractive index across EphA2-/- lenses, which is most pronounced in the nucleus.

Conclusions

This work reveals that Eph-ephrin signaling plays a role in fiber cell maturation, nuclear compaction, and lens shape. Loss of EphA2 disrupts the nuclear compaction resulting in a small lens nucleus. Our data suggest that Eph-ephrin signaling may be required for fiber cell membrane reorganization and compaction and for establishing a normal GRIN.

Shock wave and mesenchymal stem cells as treatment in the acute phase of spinal cord injury: A pilot study

INTRODUCTION

Spinal cord injury (SCI) is a complex pathology with thousands of patients worldwide. During the acute early phase, neural tissue shows some regenerative properties that disappear at the chronic phase. Shock Waves and Stem Cells have been proposed as a possible therapy.

METHODS

Here, we analyse Shock Waves' immediate effect over spinal cord genetic response in the injured and healthy spinal cord and the effect of Shock Waves and combined Shock Waves plus Stem Cells distally grafted to treat the first month after spinal cord injury.

RESULTS

The immediate application of shock waves increases VEGF (Vascular Endothelial Growth Factor) but reduces the BDNF (Brain-Derived Growth Factor) RNA (Ribonucleic acid) response. Shock wave therapy increases GFAP (Glial fibrillary acidic protein) positive cells and vascularity during the treatment's acute phase.

CONCLUSION

Shock wave treatment seems to be enough to produce benefits in the acute phase of spinal cord injury, with no accumulative positive effects when mesenchymal stem cell graft is applied together.

Adipose tissue-derived microvascular fragments promote lymphangiogenesis in a murine lymphedema model

Chronic lymphedema after cancer treatment is common and there is still no cure for this disease. We herein investigated the lymphangiogenic capacity of adipose tissue-derived microvascular fragments (MVF), which contain stem cells and lymphatic vessel fragments. Secondary lymphedema was induced in the hindlimbs of C57BL/6J mice. Green fluorescence protein (GFP)+ MVF were isolated from transgenic C57BL/6Tg (CAG-EGFP)1Osb/J mice, suspended in collagen hydrogel, and injected in the lymphadenectomy defect of wild-type animals. This crossover model allowed the detection of MVF-derived blood and lymphatic vessels after transplantation. The MVF group was compared with animals receiving collagen hydrogel only or a sham intervention. Lymphangiogenic effects were analyzed using volumetry, magnetic resonance (MR) lymphography, histology, and immunohistochemistry. MVF injection resulted in reduced hindlimb volumes when compared to non-treated controls. MR lymphography revealed lymphatic regeneration with reduced dermal backflow after MVF treatment. Finally, MVF transplantation promoted popliteal angiogenesis and lymphangiogenesis associated with a significantly increased microvessel and lymphatic vessel density. These findings indicate that MVF transplantation represents a promising approach to induce therapeutic lymphangiogenesis.

Whole embryonic detection of maternal microchimeric cells highlights significant differences in their numbers among individuals

During pregnancy in placental mammals, small numbers of maternal cells (maternal microchimeric cells, or MMc cells) migrate into the fetus and persist decades, or perhaps for the rest of their lives, and higher frequencies of MMc cells are reported to correlate with variety of phenomena, such as immune tolerance, tissue repair, and autoimmune diseases. While detection of these MMc cells is considered in all pregnancies, their frequency differs largely according to tissue type and disease cases, and it remains unclear whether the number of MMc cells differs significantly among embryos in normal pregnancies. Here, for the first time, we developed a whole embryonic detection method for MMc cells using transgenic mice and counted live MMc cells in each individual embryo. Using this technique, we found that the number of MMc cells was comparable in most of the analyzed embryos; however, around 500 times higher number of MMc cells was detected in one embryo at the latest stage. This result suggests that the number of MMc cells could largely differ in rare cases with unknown underlying mechanisms. Our methodology provides a basis for testing differences in the numbers of MMc cells among individual embryos and for analyzing differences in MMc cell type repertoires in future studies. These data could provide a hint toward understanding the mechanisms underlying the variety of apparently inconsistent MMc-related phenomena.

Fibrocytes: A Critical Review and Practical Guide

Fibrocytes are hematopoietic-derived cells that directly contribute to tissue fibrosis by producing collagen following injury, during disease, and with aging. The lack of a fibrocyte-specific marker has led to the use of multiple strategies for identifying these cells in vivo. This review will detail how past studies were performed, report their findings, and discuss their strengths and limitations. The motivation is to identify opportunities for further investigation and promote the adoption of best practices during future study design.

Eph-ephrin Signaling Affects Eye Lens Fiber Cell Intracellular Voltage and Membrane Conductance

The avascular eye lens generates its own microcirculation that is required for maintaining lifelong lens transparency. The microcirculation relies on sodium ion flux, an extensive network of gap junction (GJ) plaques between lens fiber cells and transmembrane water channels. Disruption of connexin proteins, the building blocks of GJs, or aquaporins, which make up water and adhesion channels, lead to lens opacification or cataracts. Recent studies have revealed that disruption of Eph-ephrin signaling, in particular the receptor EphA2 and the ligand ephrin-A5, in humans and mice lead to congenital and age-related cataracts. We investigated whether changes in lens transparency in EphA2 or ephrin-A5 knockout (^–/–) mice is related to changes in GJ coupling and lens fluid and ion homeostasis. Immunostaining revealed changes in connexin 50 (Cx50) subcellular localization in EphA2^–/– peripheral lens fibers and alteration in aquaporin 0 (Aqp0) staining patterns in ephrin-A5^–/– and EphA2^–/– inner mature fiber cells. Surprisingly, there was no obvious change in GJ coupling in knockout lenses. However, there were changes in fiber cell membrane conductance and intracellular voltage in knockout lenses from 3-month-old mice. These knockout lenses displayed decreased conductance of mature fiber membranes and were hyperpolarized compared to control lenses. This is the first demonstration that the membrane conductance of lens fibers can be regulated. Together these data suggest that EphA2 may be needed for normal Cx50 localization to the cell membrane and that conductance of lens fiber cells requires normal Eph-ephrin signaling and water channel localization.

CD62L expression level determines the cell fate of myeloid progenitors

Hematopoietic cells differentiate through several progenitors in a hierarchical manner, and recent single-cell analyses have revealed substantial heterogeneity within each progenitor. Although common myeloid progenitors (CMPs) are defined as a multipotent cell population that can differentiate into granulocyte-monocyte progenitors (GMPs) and megakaryocyte-erythrocyte progenitors (MEPs), and GMPs generate neutrophils and monocytes, these myeloid progenitors must contain some lineage-committed progenitors. Through gene expression analysis at single-cell levels, we identified CD62L as a marker to reveal the heterogeneity. We confirmed that CD62L-negative CMPs represent "bona fide" CMPs, whereas CD62L-high CMPs are mostly restricted to GMP potentials both in mice and humans. In addition, we identified CD62L-negative GMPs as the most immature subsets in GMPs and Ly6C+CD62L-intermediate and Ly6C+CD62L-high GMPs are skewed to neutrophil and monocyte differentiation in mice, respectively. Our findings contribute to more profound understanding about the mechanism of myeloid differentiation.

EphA2 and Ephrin-A5 Guide Eye Lens Suture Alignment and Influence Whole Lens Resilience

Purpose

Fine focusing of light by the eye lens onto the retina relies on the ability of the lens to change shape during the process of accommodation. Little is known about the cellular structures that regulate elasticity and resilience. We tested whether Eph–ephrin signaling is involved in lens biomechanical properties.

Methods

We used confocal microscopy and tissue mechanical testing to examine mouse lenses with genetic disruption of EphA2 or ephrin-A5.

Results

Confocal imaging revealed misalignment of the suture between each shell of newly added fiber cells in knockout lenses. Despite having disordered sutures, loss of EphA2 or ephrin-A5 did not affect lens stiffness. Surprisingly, knockout lenses were more resilient and recovered almost completely after load removal. Confocal microscopy and quantitative image analysis from live lenses before, during, and after compression revealed that knockout lenses had misaligned Y-sutures, leading to a change in force distribution during compression. Knockout lenses displayed decreased separation of fiber cell tips at the anterior suture at high loads and had more complete recovery after load removal, which leads to improved whole-lens resiliency.

Conclusions

EphA2 and ephrin-A5 are needed for normal patterning of fiber cell tips and the formation of a well-aligned Y-suture with fiber tips stacked on top of previous generations of fiber cells. The misalignment of lens sutures leads to increased resilience after compression. The data suggest that alignment of the Y-suture may constrain the overall elasticity and resilience of the lens.

RNA Profiling of Mouse Ependymal Cells after Spinal Cord Injury Identifies the Oncostatin Pathway as a Potential Key Regulator of Spinal Cord Stem Cell Fate

Ependymal cells reside in the adult spinal cord and display stem cell properties in vitro. They proliferate after spinal cord injury and produce neurons in lower vertebrates but predominantly astrocytes in mammals. The mechanisms underlying this glial-biased differentiation remain ill-defined. We addressed this issue by generating a molecular resource through RNA profiling of ependymal cells before and after injury. We found that these cells activate STAT3 and ERK/MAPK signaling post injury and downregulate cilia-associated genes and FOXJ1, a central transcription factor in ciliogenesis. Conversely, they upregulate 510 genes, seven of them more than 20-fold, namely Crym, Ecm1, Ifi202b, Nupr1, Rbp1, Thbs2 and Osmr—the receptor for oncostatin, a microglia-specific cytokine which too is strongly upregulated after injury. We studied the regulation and role of Osmr using neurospheres derived from the adult spinal cord. We found that oncostatin induced strong Osmr and p-STAT3 expression in these cells which is associated with reduction of proliferation and promotion of astrocytic versus oligodendrocytic differentiation. Microglial cells are apposed to ependymal cells in vivo and co-culture experiments showed that these cells upregulate Osmr in neurosphere cultures. Collectively, these results support the notion that microglial cells and Osmr/Oncostatin pathway may regulate the astrocytic fate of ependymal cells in spinal cord injury.

Tracing location by applying Emerald luciferase in an early phase of murine endometriotic lesion formation

The pathogenesis of endometriosis has not been fully elucidated. We focused on the behavior of the ectopic endometrium, that is, the origin of the endometriotic lesion, before adhering to the peritoneal cavity. To observe lesion formation in the very early phase, we developed a novel endometriosis animal model using bioluminescence technology. We established a new transgenic mouse that expressed Emerald luciferase (ELuc) under the control of the CAG promoter. This transgenic mouse, called the CAG-ELuc mouse, showed strong bioluminescence emission; we succeeded in tracing the lesion location by the emission of ELuc. The accuracy of tracing by ELuc was high (57.7-100% of correspondence) and depended on the dosage of E2 administration. In the very early phase after transplantation, the process of lesion formation can be observed non-invasively and chronologically. We have verified that the preferred location of the uterus (transplanted grafts) was fixed immediately after the transplantation of the grafts.

Adipose Tissue-Derived Microvascular Fragments From Male and Female Fat Donors Exhibit a Comparable Vascularization Capacity

Adipose tissue-derived microvascular fragments (MVF) represent effective vascularization units for tissue engineering. Most experimental studies exclusively use epididymal fat tissue of male donor mice as a source for MVF isolation. However, in future clinical practice, MVF-based approaches may be applied in both male and female patients. Therefore, we herein compared the vascularization capacity of MVF isolated from the epididymal and peri-ovarian fat tissue of male and female donor mice. Freshly isolated MVF from male and female donors did not differ in their number, length distribution, viability and cellular composition. After their assembly into spheroids, they also exhibited a comparable in vitro sprouting activity. Moreover, they could be seeded onto collagen-glycosaminoglycan matrices, which were implanted into full-thickness skin defects within mouse dorsal skinfold chambers. Repetitive intravital fluorescence microscopy as well as histological and immunohistochemical analyses revealed a comparable vascularization and incorporation of implants seeded with MVF of male and female origin. Taken together, these findings demonstrate that the vascularization capacity of MVF is not gender-specific.

Hematopoietic stem cell-derived functional osteoblasts exhibit therapeutic efficacy in a murine model of osteogenesis imperfecta

Currently, there is no cure for osteogenesis imperfecta (OI)-a debilitating pediatric skeletal dysplasia. Herein we show that hematopoietic stem cell (HSC) therapy holds promise in treating OI. Using single-cell HSC transplantation in lethally irradiated oim/oim mice, we demonstrate significant improvements in bone morphometric, mechanics, and turnover parameters. Importantly, we highlight that HSCs cause these improvements due to their unique property of differentiating into osteoblasts/osteocytes, depositing normal collagen-an attribute thus far assigned only to mesenchymal stem/stromal cells. To confirm HSC plasticity, lineage tracing was done by transplanting oim/oim with HSCs from two specific transgenic mice-VavR, in which all hematopoietic cells are GFP+ and pOBCol2.3GFP, where GFP is expressed only in osteoblasts/osteocytes. In both models, transplanted oim/oim mice demonstrated GFP+ HSC-derived osteoblasts/osteocytes in bones. These studies unequivocally establish that HSCs differentiate into osteoblasts/osteocytes, and HSC transplantation can provide a new translational approach for OI.

PDGFRα-lineage origin directs monocytes to trafficking proficiency to support peripheral immunity

Multiple embryonic precursors give rise to leukocytes in adults while the lineage‐based functional impacts are underappreciated. Mesodermal precursors expressing PDGFRα appear transiently during E7.5‐8.5 descend to a subset of Lin^–Sca1⁺Kit⁺ hematopoietic progenitors found in adult BM. By analyzing a PDGFRα‐lineage tracing mouse line, we here report that PDGFRα‐lineage BM F4/80⁺SSC^lo monocytes/macrophages are solely Ly6C⁺LFA‐1^hiMac‐1^hi monocytes enriched on the abluminal sinusoidal endothelium while Ly6C^–LFA‐1^loMac‐1^lo macrophages are mostly from non‐PDGFRα‐lineage in vivo. Monocytes with stronger integrin profiles outcompete macrophages for adhesion on an endothelial monolayer or surfaces coated with ICAM‐1‐Fc or VCAM‐1‐Fc. Egress of PDGFRα‐lineage‐rich monocytes and subsequent differentiation to peripheral macrophages spatially segregates them from non‐PDGFRα‐lineage BM‐resident macrophages and allows functional specialization since macrophages derived from these egressing monocytes differ in morphology, phenotype, and functionality from BM‐resident macrophages in culture. Extravasation preference for blood PDGFRα‐lineage monocytes varies by tissues and governs the local lineage composition of macrophages. More PDGFRα‐lineage classical monocytes infiltrated into skin and colon but not into peritoneum. Accordingly, transcriptomic analytics indicated augmented inflammatory cascades in dermatitis skin of BM‐chimeric mice harbouring only PDGFRα‐lineage leukocytes. Thus, the PDGFRα‐lineage origin biasedly generates monocytes predestined for BM exit to support peripheral immunity following extravasation and macrophage differentiation.

Clonal hematopoiesis with JAK2V617F promotes pulmonary hypertension with ALK1 upregulation in lung neutrophils

Pulmonary hypertension (PH) is a progressive cardiopulmonary disease characterized by pulmonary arterial remodeling. Clonal somatic mutations including JAK2V617F, the most frequent driver mutation among myeloproliferative neoplasms, have recently been identified in healthy individuals without hematological disorders. Here, we reveal that clonal hematopoiesis with JAK2V617F exacerbates PH and pulmonary arterial remodeling in mice. JAK2V617F-expressing neutrophils specifically accumulate in pulmonary arterial regions, accompanied by increases in neutrophil-derived elastase activity and chemokines in chronic hypoxia-exposed JAK2V617F transgenic (JAK2^V617F) mice, as well as recipient mice transplanted with JAK2^V617F bone marrow cells. JAK2V617F progressively upregulates Acvrl1 (encoding ALK1) during the differentiation from bone marrow stem/progenitor cells peripherally into mature neutrophils of pulmonary arterial regions. JAK2V617F-mediated STAT3 phosphorylation upregulates ALK1-Smad1/5/8 signaling. ALK1/2 inhibition completely prevents the development of PH in JAK2^V617F mice. Finally, our prospective clinical study identified JAK2V617F-positive clonal hematopoiesis is more common in PH patients than in healthy subjects. These findings indicate that clonal hematopoiesis with JAK2V617F causally leads to PH development associated with ALK1 upregulation.

A multistate stem cell dynamics maintains homeostasis in mouse spermatogenesis

In mouse testis, a heterogeneous population of undifferentiated spermatogonia (Aundiff) harbors spermatogenic stem cell (SSC) potential. Although GFRα1+ Aundiff maintains the self-renewing pool in homeostasis, the functional basis of heterogeneity and the implications for their dynamics remain unresolved. Here, through quantitative lineage tracing of SSC subpopulations, we show that an ensemble of heterogeneous states of SSCs supports homeostatic, persistent spermatogenesis. Such heterogeneity is maintained robustly through stochastic interconversion of SSCs between a renewal-biased Plvap+/GFRα1+ state and a differentiation-primed Sox3+/GFRα1+ state. In this framework, stem cell commitment occurs not directly but gradually through entry into licensed but uncommitted states. Further, Plvap+/GFRα1+ cells divide slowly, in synchrony with the seminiferous epithelial cycle, while Sox3+/GFRα1+ cells divide much faster. Such differential cell-cycle dynamics reduces mitotic load, and thereby the potential to acquire harmful de novo mutations of the self-renewing pool, while keeping the SSC density high over the testicular open niche.

3D tumor angiogenesis models: recent advances and challenges

The development of blood vessels, referred to as angiogenesis, is an intricate process regulated spatially and temporally through a delicate balance between the qualitative and quantitative expression of pro and anti-angiogenic molecules. As angiogenesis is a prerequisite for solid tumors to grow and metastasize, a variety of tumor angiogenesis models have been formulated to better understand the underlying mechanisms and associated clinical applications. Studies have demonstrated independent mechanisms inducing angiogenesis in tumors such as (a) HIF-1/VEGF mediated paracrine interactions between a cancer cell and endothelial cells, (b) recruitment of progenitor endothelial cells, and (c) vasculogenic mimicry. Moreover, single-cell sequencing technologies have indicated endothelial cell heterogeneity among organ systems including tumor tissues. However, existing angiogenesis models often rely upon normal endothelial cells which significantly differ from tumor endothelial cells exhibiting distinct (epi)genetic and metabolic signatures. Besides, the existence of intra-individual variations necessitates the development of improved tumor vascular model systems for personalized medicine. In the present review, we summarize recent advancements of 3D tumor vascular model systems which include (a) tissue engineering-based tumor models; (b) vascular organoid models, and (c) organ-on-chips and their importance in replicating the tumor angiogenesis along with the associated challenges to design improved models.

Irbesartan, an angiotensin II type 1 receptor blocker, inhibits colitis-associated tumourigenesis by blocking the MCP-1/CCR2 pathway

The introduction of anti-inflammatory therapies has enabled substantial improvement of disease activity in patients with inflammatory bowel diseases (IBD). However, IBD can lead to serious complications such as intestinal fibrosis and colorectal cancer. Therefore, novel therapies reducing the development of these complications are needed. Angiotensin II (Ang II) promotes tissue inflammation by stimulating the production of monocyte chemoattractant protein-1 (MCP-1) or proinflammatory cytokines. It plays a pivotal role in IBD progression. Although blockade of Ang II has been reported to ameliorate experimental colitis and reduce colorectal cancer risk, the cellular and molecular mechanisms remain poorly understood. Our previous work showed that irbesartan, an Ang II type 1 receptor blocker, reduced the number of C-C chemokine receptor 2-positive (CCR2+) monocytic cells in the inflamed pancreas. This study aimed to investigate the possible antifibrotic and antitumour effects of irbesartan using the azoxymethane/dextran sodium sulphate mouse model. Irbesartan suppressed MCP-1 production and the accumulation of Ly6C+CCR2+ monocytes and fibrocytes in the inflamed colon, downregulated the expression of type 1 collagen and matrix metalloproteinase 9 and inhibited the development of intestinal fibrosis and tumours. Our observations suggest that blocking the MCP-1/CCR2 pathway using irbesartan might be beneficial in preventing colitis-associated colon tumours.

Delayed administration of ixazomib modifies the immune response and prevents chronic graft-versus-host disease

In this study, we aimed to modify the immune response in the long term after allogeneic bone marrow transplantation (allo-BMT) by using the proteasome inhibitor ixazomib (IXZ) at the late stages of the post-transplant period. This approach facilitated the immune reconstitution after transplantation. IXZ significantly prolonged survival and decreased the risk of chronic graft-versus-host disease (cGvHD) in two different murine models without hampering the graft-versus-leukemia (GvL) effect, as confirmed by bioluminescence assays. Remarkably, the use of IXZ was related to an increase of regulatory T cells both in peripheral blood and in the GvHD target organs and a decrease of effector donor T cells. Regarding B cells, IXZ treated mice had faster recovery of B cells in PB and of pre-pro-B cells in the bone marrow. Mice receiving ixazomib had a lower number of neutrophils in the GvHD target organs as compared to the vehicle group. In summary, delayed administration of IXZ ameliorated cGvHD while preserving GvL and promoted a pro-tolerogenic immune response after allo-BMT.

Vascularization of Microvascular Fragment Isolates from Visceral and Subcutaneous Adipose Tissue of Mice

Background:

Adipose tissue-derived microvascular fragments (MVF) represent effective vascularization units for tissue engineering. Most experimental studies in rodents exclusively use epididymal adipose tissue as a visceral fat source for MVF isolation. However, in future clinical practice, MVF may be rather isolated from liposuctioned subcutaneous fat tissue of patients. Therefore, we herein compared the vascularization characteristics of MVF isolates from visceral and subcutaneous fat tissue of murine origin.

Methods:

MVF isolates were generated from visceral and subcutaneous fat tissue of donor mice using two different enzymatic procedures. For in vivo analyses, the MVF isolates were seeded onto collagen-glycosaminoglycan scaffolds and implanted into full-thickness skin defects within dorsal skinfold chambers of recipient mice.

Results:

By means of the two isolation procedures, we isolated a higher number of MVF from visceral fat tissue when compared to subcutaneous fat tissue, while their length distribution, viability and cellular composition were comparable in both groups. Intravital fluorescence microscopy as well as histological and immunohistochemical analyses revealed a significantly reduced vascularization of implanted scaffolds seeded with subcutaneous MVF isolates when compared to implants seeded with visceral MVF isolates. Light and scanning electron microscopy showed that this was due to high amounts of undigested connective tissue within the subcutaneous MVF isolates, which clogged the scaffold pores and prevented the interconnection of individual MVF into new microvascular networks.

Conclusion:

These findings indicate the need for improved protocols to generate connective tissue-free MVF isolates from subcutaneous fat tissue for future translational studies.

Pantothenate kinase activation relieves coenzyme A sequestration and improves mitochondrial function in mice with propionic acidemia

[Figure: see text].

Sites of Cre-recombinase activity in mouse lines targeting skeletal cells

The Cre/Lox system is a powerful tool in the biologist's toolbox, allowing loss-of-function and gain-of-function studies, as well as lineage tracing, through gene recombination in a tissue-specific and inducible manner. Evidence indicates, however, that Cre transgenic lines have a far more nuanced and broader pattern of Cre activity than initially thought, exhibiting "off-target" activity in tissues/cells other than the ones they were originally designed to target. With the goal of facilitating the comparison and selection of optimal Cre lines to be used for the study of gene function, we have summarized in a single manuscript the major sites and timing of Cre activity of the main Cre lines available to target bone mesenchymal stem cells, chondrocytes, osteoblasts, osteocytes, tenocytes, and osteoclasts, along with their reported sites of "off-target" Cre activity. We also discuss characteristics, advantages, and limitations of these Cre lines for users to avoid common risks related to overinterpretation or misinterpretation based on the assumption of strict cell-type specificity or unaccounted effect of the Cre transgene or Cre inducers. © 2021 American Society for Bone and Mineral Research (ASBMR).

High levels of TFAM repress mammalian mitochondrial DNA transcription in vivo

Mitochondrial transcription factor A (TFAM) is compacting mitochondrial DNA (dmtDNA) into nucleoids and directly controls mtDNA copy number. Here, we show that the TFAM-to-mtDNA ratio is critical for maintaining normal mtDNA expression in different mouse tissues. Moderately increased TFAM protein levels increase mtDNA copy number but a normal TFAM-to-mtDNA ratio is maintained resulting in unaltered mtDNA expression and normal whole animal metabolism. Mice ubiquitously expressing very high TFAM levels develop pathology leading to deficient oxidative phosphorylation (OXPHOS) and early postnatal lethality. The TFAM-to-mtDNA ratio varies widely between tissues in these mice and is very high in skeletal muscle leading to strong repression of mtDNA expression and OXPHOS deficiency. In the heart, increased mtDNA copy number results in a near normal TFAM-to-mtDNA ratio and maintained OXPHOS capacity. In liver, induction of LONP1 protease and mitochondrial RNA polymerase expression counteracts the silencing effect of high TFAM levels. TFAM thus acts as a general repressor of mtDNA expression and this effect can be counterbalanced by tissue-specific expression of regulatory factors.

Tesmin, Metallothionein-Like 5, is Required for Spermatogenesis in Mice†

In mammals, more than 2000 genes are specifically or abundantly expressed in testis, but gene knockout studies revealed several are not individually essential for male fertility. Tesmin (Metallothionein-like 5; Mtl5) was originally reported as a testis-specific transcript that encodes a member of the cysteine-rich motif containing metallothionein family. Later studies showed that Tesmin has two splicing variants and both are specifically expressed in male and female germ cells. Herein, we clarified that the long (Tesmin-L) and short (Tesmin-S) transcript forms start expressing from spermatogonia and the spermatocyte stage, respectively, in testis. Furthermore, while Tesmin-deficient female mice are fertile, male mice are infertile due to arrested spermatogenesis at the pachytene stage. We were able to rescue the infertility with a Tesmin-L transgene, where we concluded that TESMIN-L is critical for meiotic completion in spermatogenesis and indispensable for male fertility.

Differences in growth and vascularization of ectopic menstrual and non-menstrual endometrial tissue in mouse models of endometriosis

STUDY QUESTION

Is there a difference in the growth and vascularization between murine endometriotic lesions originating from menstrual or non-menstrual endometrial fragments?

SUMMARY ANSWER

Endometriotic lesions developing from menstrual and non-menstrual tissue fragments share many similarities, but also exhibit distinct differences in growth and vascularization, particularly under exogenous estrogen stimulation.

WHAT IS KNOWN ALREADY

Mouse models are increasingly used in endometriosis research. For this purpose, menstrual or non-menstrual endometrial fragments serve for the induction of endometriotic lesions. So far, these two fragment types have never been directly compared under identical experimental conditions.

STUDY DESIGN, SIZE, DURATION

This was a prospective experimental study in a murine peritoneal and dorsal skinfold chamber model of endometriosis. Endometrial tissue fragments from menstruated (n = 15) and non-menstruated (n = 21) C57BL/6 mice were simultaneously transplanted into the peritoneal cavity or dorsal skinfold chamber of non-ovariectomized (non-ovx, n = 17), ovariectomized (ovx, n = 17) and ovariectomized, estrogen-substituted (ovx+E2, n = 17) recipient animals and analyzed throughout an observation period of 28 and 14 days, respectively.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The engraftment, growth and vascularization of the newly developing endometriotic lesions were analyzed by means of high-resolution ultrasound imaging, intravital fluorescence microscopy, histology and immunohistochemistry.

MAIN RESULTS AND THE ROLE OF CHANCE

Menstrual and non-menstrual tissue fragments developed into peritoneal endometriotic lesions without differences in growth, microvessel density and cell proliferation in non-ovx mice. Lesion formation out of both fragment types was markedly suppressed in ovx mice. In case of non-menstrual tissue fragments, this effect could be reversed by estrogen supplementation. In contrast, endometriotic lesions originating from menstrual tissue fragments exhibited a significantly smaller volume in ovx+E2 mice, which may be due to a reduced hormone sensitivity. Moreover, menstrual tissue fragments showed a delayed vascularization and a reduced blood perfusion after transplantation into dorsal skinfold chambers when compared to non-menstrual tissue fragments, indicating different vascularization modes of the two fragment types. To limit the role of chance, the experiments were conducted under standardized laboratory conditions. Statistical significance was accepted for a value of P < 0.05.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Endometriotic lesions were induced by syngeneic tissue transplantation into recipient mice without the use of pathological endometriotic tissue of human nature. Therefore, the results obtained in this study may not fully relate to human patients with endometriosis.

WIDER IMPLICATIONS OF THE FINDINGS

The present study significantly contributes to the characterization of common murine endometriosis models. These models represent important tools for studies focusing on the basic mechanisms of endometriosis and the development of novel therapeutic strategies for the treatment of this frequent gynecological disease. The presented findings indicate that the combination of different experimental models and approaches may be the most appropriate strategy to study the pathophysiology and drug sensitivity of a complex disease such as endometriosis under preclinical conditions.

STUDY FUNDING/COMPETING INTEREST(S)

There was no specific funding of this study. The authors have no conflicts of interest to declare.

Skeletal stem and progenitor cells maintain cranial suture patency and prevent craniosynostosis

Cranial sutures are major growth centers for the calvarial vault, and their premature fusion leads to a pathologic condition called craniosynostosis. This study investigates whether skeletal stem/progenitor cells are resident in the cranial sutures. Prospective isolation by FACS identifies this population with a significant difference in spatio-temporal representation between fusing versus patent sutures. Transcriptomic analysis highlights a distinct signature in cells derived from the physiological closing PF suture, and scRNA sequencing identifies transcriptional heterogeneity among sutures. Wnt-signaling activation increases skeletal stem/progenitor cells in sutures, whereas its inhibition decreases. Crossing Axin2LacZ/+ mouse, endowing enhanced Wnt activation, to a Twist1+/- mouse model of coronal craniosynostosis enriches skeletal stem/progenitor cells in sutures restoring patency. Co-transplantation of these cells with Wnt3a prevents resynostosis following suturectomy in Twist1+/- mice. Our study reveals that decrease and/or imbalance of skeletal stem/progenitor cells representation within sutures may underlie craniosynostosis. These findings have translational implications toward therapeutic approaches for craniosynostosis.

Crucial role of hematopoietic JAK2 V617F in the development of aortic aneurysms

JAK2 V617F is the most frequent driver mutation in myeloproliferative neoplasms (MPN) and is associated with vascular complications. However, the impact of hematopoietic JAK2 V617F on aortic aneurysms (AA) remains unknown. Our cross-sectional study indicated that nine (23%) of 39 MPN patients with JAK2 V617F exhibited the presence of AA. In order to clarify whether the hematopoietic JAK2 V617F contributes to the AA, we applied bone marrow transplantation (BMT) with the donor cells from Jak2 V617F transgenic (JAK2^V617F) mice or control wild-type (WT) mice into lethally irradiated apolipoprotein E-deficient mice. Five weeks after BMT, the JAK2^V617F-BMT mice and WT-BMT mice were subjected to continuous angiotensin II infusion to induce AA formation. Four weeks after angiotensin II infusion, the abdominal aorta diameter in the JAK2^V617F-BMT mice was significantly enlarged compared to that in the WT-BMT mice. Additionally, the abdominal AA-free survival rate was significantly lower in the JAK2^V617F-BMT mice. Hematopoietic JAK2 V617F accelerated aortic elastic lamina degradation as well as activation of matrix metalloproteinase (MMP)-2 and MMP-9 in the abdominal aorta. The numbers of infiltrated macrophages were significantly upregulated in the abdominal aorta of the JAK2^V617F-BMT mice accompanied by STAT3 phosphorylation. The accumulation of BM-derived hematopoietic cells carrying JAK2 V617F in the abdominal aorta was confirmed by use of the reporter green fluorescent proteintransgene. BM-derived macrophages carrying JAK2 V617F showed increases in mRNA expression levels of Mmp2, Mmp9, and Mmp13. Ruxolitinib decreased the abdominal aorta diameter and the incidence of abdominal AA in the JAK2^V617F-BMT mice. Our findings provide a novel feature of vascular complications of AA in MPN with JAK2 V617F.

Blastocyst complementation reveals that NKX2-1 establishes the proximal-peripheral boundary of the airway epithelium

BACKGROUND

Distinct boundaries between the proximal conducting airways and more peripheral-bronchial regions of the lung are established early in foregut embryogenesis, demarcated in part by the distribution of SOX family and NKX2-1 transcription factors along the cephalo-caudal axis of the lung. We used blastocyst complementation to identify the role of NKX2-1 in the formation of the proximal-peripheral boundary of the airways in mouse chimeric embryos.

RESULTS

While Nkx2-1-/- mouse embryos form primordial tracheal cysts, peripheral pulmonary structures are entirely lacking in Nkx2-1-/- mice. Complementation of Nkx2-1-/- embryos with NKX2-1-sufficient embryonic stem cells (ESCs) enabled the formation of all tissue components of the peripheral lung but did not enhance ESC colonization of the most proximal regions of the airways. In chimeric mice, a precise boundary was formed between NKX2-1-deficient basal cells co-expressing SOX2 and SOX9 in large airways and ESC-derived NKX2-1+ SOX9+ epithelial cells of smaller airways. NKX2-1-sufficient ESCs were able to selectively complement peripheral, rather than most proximal regions of the airways. ESC complementation did not prevent ectopic expression of SOX9 but restored β-catenin signaling in Nkx2-1-/- basal cells of large airways.

CONCLUSIONS

NKX2-1 and β-catenin function in an epithelial cell-autonomous manner to establish the proximal-peripheral boundary along developing airways.

Relevance of circulating hybrid cells as a non-invasive biomarker for myriad solid tumors

Metastatic progression defines the final stages of tumor evolution and underlies the majority of cancer-related deaths. The heterogeneity in disseminated tumor cell populations capable of seeding and growing in distant organ sites contributes to the development of treatment resistant disease. We recently reported the identification of a novel tumor-derived cell population, circulating hybrid cells (CHCs), harboring attributes from both macrophages and neoplastic cells, including functional characteristics important to metastatic spread. These disseminated hybrids outnumber conventionally defined circulating tumor cells (CTCs) in cancer patients. It is unknown if CHCs represent a generalized cancer mechanism for cell dissemination, or if this population is relevant to the metastatic cascade. Herein, we detect CHCs in the peripheral blood of patients with cancer in myriad disease sites encompassing epithelial and non-epithelial malignancies. Further, we demonstrate that in vivo-derived hybrid cells harbor tumor-initiating capacity in murine cancer models and that CHCs from human breast cancer patients express stem cell antigens, features consistent with the potential to seed and grow at metastatic sites. Finally, we reveal heterogeneity of CHC phenotypes reflect key tumor features, including oncogenic mutations and functional protein expression. Importantly, this novel population of disseminated neoplastic cells opens a new area in cancer biology and renewed opportunity for battling metastatic disease.

Altered Induction of Reactive Oxygen Species by X-rays in Hematopoietic Cells of C57BL/6-Tg (CAG-EGFP) Mice

Previous work pointed to a critical role of excessive production of reactive oxygen species (ROS) in increased radiation hematopoietic death in GFP mice. Meanwhile, enhanced antioxidant capability was not demonstrated in the mouse model of radio-induced adaptive response (RAR) using rescue of radiation hematopoietic death as the endpoint. ROS induction by ex vivo X-irradiation at a dose ranging from 0.1 to 7.5 Gy in the nucleated bone marrow cells was comparatively studied using GFP and wild type (WT) mice. ROS induction was also investigated in the cells collected from mice receiving a priming dose (0.5 Gy) efficient for RAR induction in WT mice. Significantly elevated background and increased induction of ROS in the cells from GFP mice were observed compared to those from WT mice. Markedly lower background and decreased induction of ROS were observed in the cells collected from WT mice but not GFP mice, both receiving the priming dose. GFP overexpression could alter background and induction of ROS by X-irradiation in hematopoietic cells. The results provide a reasonable explanation to the previous study on the fate of cells and mice after X-irradiation and confirm enhanced antioxidant capability in RAR. Investigations involving GFP overexpression should be carefully interpreted.

Rapid methods for the evaluation of fluorescent reporters in tissue clearing and the segmentation of large vascular structures

Light sheet fluorescence microscopy (LSFM) of large tissue samples does not require mechanical sectioning and allows efficient visualization of spatially complex or rare structures. Therefore, LSFM has become invaluable in developmental and biomedical research. Because sample size may limit whole-mount staining, LSFM benefits from transgenic reporter organisms expressing fluorescent proteins (FPs) and, however, requires optical clearing and computational data visualization and analysis. The former often interferes with FPs, while the latter requires massive computing resources. Here, we describe 3D-polymerized cell dispersions, a rapid and straightforward method, based on recombinant FP expression in freely selectable tester cells, to evaluate and compare fluorescence retention in different tissue-clearing protocols. For the analysis of large LSFM data, which usually requires huge computing resources, we introduce a refined, interactive, hierarchical random walker approach that is capable of efficient segmentation of the vasculature in data sets even on a consumer grade PC.

Targeted delivery of regulatory macrophages to lymph nodes interferes with T cell priming by preventing the formation of stable immune synapses

Immunosuppressive myeloid cells are frequently induced in tumors and attenuate anti-tumor effector functions. In this study, we differentiate immunosuppressive regulatory macrophages (Mregs) from hematopoietic progenitors and test their potential to suppress adaptive immune responses in lymph nodes. Targeted delivery of Mregs to lymph nodes is facilitated by retroviral overexpression of the chemokine receptor CCR7 and intra-lymphatic cell application. Delivery of Mregs completely abolishes the priming of cognate CD8 cells and strongly reduces delayed-type hypersensitivity reactions. Mreg-mediated T cell suppression requires cell-cell contact-regulated nitric oxide production. Two-photon microscopy reveals that nitric oxide produced by Mregs reduces the interaction duration between dendritic cells and T cells. Exposure of activated T cells to nitric oxide strongly reduces their binding to ICAM-1, indicating that nitrosylation of proteins involved in cell adhesion affects synapse formation. Thus, this study identifies a mechanism of myeloid cell-mediated immune suppression and provides an approach for its therapeutic use.

Protection of Antigen-Primed Effector T Cells From Glucocorticoid-Induced Apoptosis in Cell Culture and in a Mouse Model of Multiple Sclerosis

Induction of T cell apoptosis constitutes a major mechanism by which therapeutically administered glucocorticoids (GCs) suppress inflammation and associated clinical symptoms, for instance in multiple sclerosis (MS) patients suffering from an acute relapse. The sensitivity of T cells to GC action depends on their maturation and activation status, but the precise effect of antigen-priming in a pathological setting has not been explored. Here we used transgenic and congenic mouse models to compare GC-induced apoptosis between naïve and antigen-specific effector T cells from mice immunized with a myelin peptide. Antigen-primed effector T cells were protected from the pro-apoptotic activity of the synthetic GC dexamethasone in a dose-dependent manner, which resulted in their accumulation relative to naïve T cells in vitro and in vivo. Notably, the differential sensitivity of T cells to GC-induced apoptosis correlated with their expression level of the anti-apoptotic proteins Bcl-2 and Bcl-X_L and a loss of the mitochondrial membrane potential. Moreover, accumulation of antigen-primed effector T cells following GC treatment in vitro resulted in an aggravated disease course in an adoptive transfer mouse model of MS in vivo, highlighting the clinical relevance of the observed phenomenon. Collectively, our data indicate that antigen-priming influences the T cells’ sensitivity to therapeutically applied GCs in the context of inflammatory diseases.

ACSA-2 and GLAST classify subpopulations of multipotent and glial-restricted cerebellar precursors

The formation of the cerebellum is highly coordinated to obtain its characteristic morphology and all cerebellar cell types. During mouse postnatal development, cerebellar progenitors with astroglial‐like characteristics generate mainly astrocytes and oligodendrocytes. However, a subset of astroglial‐like progenitors found in the prospective white matter (PWM) produces astroglia and interneurons. Characterizing these cerebellar astroglia‐like progenitors and distinguishing their developmental fates is still elusive. Here, we reveal that astrocyte cell surface antigen‐2 (ACSA‐2), lately identified as ATPase, Na+/K+ transporting, beta 2 polypeptide, is expressed by glial precursors throughout postnatal cerebellar development. In contrast to common astrocyte markers, ACSA‐2 appears on PWM cells but is absent on Bergmann glia (BG) precursors. In the adult cerebellum, ACSA‐2 is broadly expressed extending to velate astrocytes in the granular layer, white matter astrocytes, and to a lesser extent to BG. Cell transplantation and transcriptomic analysis revealed that marker staining discriminates two postnatal progenitor pools. One subset is defined by the co‐expression of ACSA‐2 and GLAST and the expression of markers typical of parenchymal astrocytes. These are PWM precursors that are exclusively gliogenic. They produce predominantly white matter and granular layer astrocytes. Another subset is constituted by GLAST positive/ACSA‐2 negative precursors that express neurogenic and BG‐like progenitor genes. This population displays multipotency and gives rise to interneurons besides all glial types, including BG. In conclusion, this work reports about ACSA‐2, a marker that in combination with GLAST enables for the discrimination and isolation of multipotent and glia‐committed progenitors, which generate different types of cerebellar astrocytes.

Two populations of self-maintaining monocyte-independent macrophages exist in adult epididymis and testis

Macrophages are the principal immune cells of the epididymis and testis, but their origins, heterogeneity, development, and maintenance are not well understood. Here, we describe distinct populations of epididymal and testicular macrophages that display an organ-specific cellular identity. Combining in vivo fate-mapping, chimeric and parabiotic mouse models with in-depth cellular analyses, we found that CD64^hiMHCII^lo and CD64^loMHCII^hi macrophage populations of epididymis and testis arise sequentially from yolk sac erythro-myeloid progenitors, embryonic hematopoiesis, and nascent neonatal monocytes. While monocytes were the major developmental source of both epididymal and testicular macrophages, both populations self-maintain in the steady-state independent of bone marrow hematopoietic precursors. However, after radiation-induced macrophage ablation or during infection, bone marrow-derived circulating monocytes are recruited to the epididymis and testis, giving rise to inflammatory macrophages that promote tissue damage. These results define the layered ontogeny, maintenance and inflammatory response of macrophage populations in the male reproductive organs.

Mouse Bone Marrow-derived Microglia-like Cells Secrete Transforming Growth Factor-β1 and Promote Microglial Aβ Phagocytosis and Reduction of Brain Aβ

Accumulation of amyloid-β (Aβ) in brain tissue contributes to the pathophysiology of Alzheimer's disease (AD). We recently reported that intrahippocampal transplantation of mouse bone marrow-derived microglia-like (BMDML) cells suppresses brain amyloid pathology and cognitive impairment in a mouse model of AD. How these transplanted cells interact with resident microglia remains unknown. In the present study, we evaluated the effects of cytokines secreted from mouse BMDML cells on cultured mouse microglia. Conditioned medium from BMDML cells increased microglial Aβ phagocytosis. High levels of transforming growth factor-β1 (TGF-β1) were present in the conditioned medium, and BMDML cells and microglia expressed Tgf-β1 mRNA and TGF-β receptor type 1 (TGF-βR1) protein, respectively. BMDML conditioned medium also induced microglial Smad2/3 phosphorylation. A TGF-βR1 inhibitor suppressed Smad2/3 phosphorylation and promotion of microglial Aβ phagocytosis induced by conditioned medium. Recombinant mouse TGF-β1 similarly increased microglial Aβ phagocytosis and induced Smad2/3 phosphorylation, which were suppressed by the TGF-βR1 inhibitor. Brain TGF-β1 levels and resident microglial TGF-β1R expression were increased by intrahippocampal injection of BMDML cells in a mouse model of AD. Cotreatment with the TGF-βR1 inhibitor suppressed the ability of transplanted BMDML cells to increase microglial TGF-β1R expression and decrease hippocampal Aβ levels. Taken together, these findings suggested that transplanted BMDML cells secreted TGF-β1 to stimulate Aβ phagocytosis by resident microglia and decrease brain Aβ pathology.

Group 2 innate lymphoid cells support hematopoietic recovery under stress conditions

The cell-cycle status of hematopoietic stem and progenitor cells (HSPCs) becomes activated following chemotherapy-induced stress, promoting bone marrow (BM) regeneration; however, the underlying molecular mechanism remains elusive. Here we show that BM-resident group 2 innate lymphoid cells (ILC2s) support the recovery of HSPCs from 5-fluorouracil (5-FU)-induced stress by secreting granulocyte-macrophage colony-stimulating factor (GM-CSF). Mechanistically, IL-33 released from chemo-sensitive B cell progenitors activates MyD88-mediated secretion of GM-CSF in ILC2, suggesting the existence of a B cell-ILC2 axis for maintaining hematopoietic homeostasis. GM-CSF knockout mice treated with 5-FU showed severe loss of myeloid lineage cells, causing lethality, which was rescued by transferring BM ILC2s from wild-type mice. Further, the adoptive transfer of ILC2s to 5-FU-treated mice accelerates hematopoietic recovery, while the reduction of ILC2s results in the opposite effect. Thus, ILC2s may function by "sensing" the damaged BM spaces and subsequently support hematopoietic recovery under stress conditions.

The effects of reducing the root length by apicoectomy on dental pulp revascularization following tooth replantation in mice

BACKGROUND/AIM

Root length is a critical factor for dental pulp regeneration following tooth replantation. The aim of this study was to analyze the effects of reducing the root length by apicoectomy on the pulp healing process using a model for tooth replantation.

MATERIAL AND METHODS

After extraction of the upper first molars (M1) of 3-week-old mice, the roots from the experimental group (EG) were shortened to half to two-thirds of their length before replantation, whereas in the control group (CG) the extracted teeth were immediately repositioned into their alveolar sockets. To determine the effects of root resection on the survival of inherent pulp cells, this study included tooth transplantation with root resection using wild-type (WT) and green fluorescent protein (GFP) transgenic mice. The M1 of GFP transgenic mice were transplanted into the alveolar socket of the M1 of WT mice. The roots of the right M1 were shortened (EG), whereas the left M1 remained untreated (CG).

RESULTS

Apoptotic cells in the EG significantly decreased in number compared with the CG at day 3. Cell proliferative activity in the EG was significantly higher than that in the CG in the root pulp during days 3-5, and nestin-positive odontoblast-like cells began to arrange themselves along the pulp-dentin border in the cusp area at day 5 in the EG but not in the CG. At week 2, tertiary dentin had formed throughout the pulp in the EG, whereas the combined tissue of dentin and bone occupied the pulp space in 60% of the CG. Root resection also positively affected the survival of inherent pulp cells to differentiate into odontoblast-like cells as demonstrated by transplantation using GFP transgenic mice.

CONCLUSIONS

Reducing the root length accelerated pulp regeneration following tooth replantation due to the better environment for revascularization.

Inflammation rapidly recruits mammalian GMP and MDP from bone marrow into regional lymphatics

Innate immune cellular effectors are actively consumed during systemic inflammation, but the systemic traffic and the mechanisms that support their replenishment remain unknown. Here, we demonstrate that acute systemic inflammation induces the emergent activation of a previously unrecognized system of rapid migration of granulocyte-macrophage progenitors and committed macrophage-dendritic progenitors, but not other progenitors or stem cells, from bone marrow (BM) to regional lymphatic capillaries. The progenitor traffic to the systemic lymphatic circulation is mediated by Ccl19/Ccr7 and is NF-κB independent, Traf6/IκB-kinase/SNAP23 activation dependent, and is responsible for the secretion of pre-stored Ccl19 by a subpopulation of CD205+/CD172a+ conventional dendritic cells type 2 and upregulation of BM myeloid progenitor Ccr7 signaling. Mature myeloid Traf6 signaling is anti-inflammatory and necessary for lymph node myeloid cell development. This report unveils the existence and the mechanistic basis of a very early direct traffic of myeloid progenitors from BM to lymphatics during inflammation.

Identification of PDGFRα-positive interstitial cells in the distal segment of the murine vas deferens

Platelet-derived growth factor receptor-α (PDGFRα)-positive interstitial cells (ICs) are widely distributed in various organs and may be involved in the motility of various tubular organs. We, for the first time, aimed to investigate the distribution, immunohistochemical characteristics, and ultrastructure of PDGFRα-positive ICs in murine vas deferens, using confocal laser scanning microscopy, transmission electron microscopy (TEM), and immuno-electron microscopy (immuno-EM). For immunofluorescence, we used antibodies against PDGFRα and other markers of ICs. PDGFRα-positive ICs were distributed widely in the lamina propria, smooth muscles, and serosal layers. Although most PDGFRα-positive ICs labeled CD34, they did not label CD34 in the subepithelial layers. Additionally, PDGFRα-positive ICs were in close proximity to each other, as also to the surrounding cells. TEM and immuno-EM findings revealed that PDGFRα-positive ICs established close physical interactions with adjacent ICs. Extracellular vesicles were also detected around the PDGFRα-positive ICs. Our morphological findings suggest that PDGFRα-positive ICs may have several subpopulations, which can play an important role in intercellular signaling via direct contact with the IC network and the extracellular vesicles in the murine vas deferens. Further investigation on PDGFRα-positive ICs in the vas deferens may lead to understanding the vas deferens mortility.

Intracerebral Transplantation of Neural Stem Cells Restores Manganese-Induced Cognitive Deficits in Mice

Manganese (Mn) is a potent neurotoxin known to cause long-lasting structural damage and progressive cognitive deficits in the brain. However, new therapeutic approaches are urgently needed since current treatments only target symptoms of Mn exposure. Recent studies have suggested a potential role for multipotent neural stem cells (NSCs) in the etiology of Mn-induced cognitive deficits. In this study, we evaluated the effect of direct intracerebral transplantation of NSCs on cognitive function of mice chronically exposed to MnCl₂, and further explored the distribution of transplanted NSCs in brain tissues. NSCs were isolated and bilaterally injected into the hippocampal regions or lateral ventricles of Mn-exposed mice. The results showed that many transplanted cells migrated far away from the injection sites and survived in vivo in the Mn-exposed mouse brain, implying enhanced neurogenesis in the host brain. We found that NSCs transplanted into either the hippocampal regions or the lateral ventricles significantly improved spatial learning and memory function of the Mn-exposed mice in the Morris water maze. Immunofluorescence analyses indicated that some surviving NSCs differentiated into neurons or glial cells, which may have become functionally integrated into the impaired local circuits, providing a possible cellular basis for the improvement of cognitive function in NSC-transplanted mice. Taken together, our findings confirm the Mn-induced impairment of neurogenesis in the brain and underscore the potential of treating Mn exposure by NSC transplantation, providing a practical therapeutic strategy against this type of neurotoxicity.