VEGFR1 TK signaling protects the lungs against LPS-induced injury by suppressing the activity of alveolar macrophages and enhancing the anti-inflammatory function of monocyte-derived macrophages.

Acute lung injury (ALI) is characterized by hyperinflammation followed by vascular leakage and respiratory failure. Vascular endothelial growth factor (VEGF)-A is critical for capillary permeability; however, the role of VEGF receptor 1 (VEGFR1) signaling in ALI progression remains unclear. Here, we show that deletion of VEGFR1 tyrosine kinase (TK) signaling in mice exacerbates lipopolysaccharide (LPS)-induced ALI as evidenced by excessive pro-inflammatory cytokine production and interleukin(IL)-1ß-producing neutrophil recruitment to inflamed lung tissues. ALI development involves reduced alveolar macrophage (AM) levels and recruitment of monocyte-derived macrophages (MDMs) in a VEGFR1 TK-dependent manner. VEGFR1 TK signaling reduced pro-inflammatory cytokine levels in cultured AMs. VEGFR1 TK-expressing MDMs displayed an anti-inflammatory macrophage phenotype. Additionally, the transplantation of VEGFR1 TK-expressing bone marrow (BM)-derived macrophages into VEGFR1 TK-deficient mice reduced lung inflammation. Treatment with placental growth factor (PlGF), an agonist for VEGFR1, protected the lung against LPS-induced ALI associated with increased MDMs. These results suggest that VEGFR1 TK signaling prevents LPS-induced ALI by suppressing the pro-inflammatory activity of AMs and enhancing the anti-inflammatory function of MDMs.

Geometric Morphometric Study on Distinguishing Metopic Craniosynostosis from Metopic Ridging.

Background: Craniosynostosis, a common congenital anomaly, results from premature fusion of the cranial sutures. One of the forms of craniosynostosis is premature fusion of the metopic suture, referred to as trigonocephaly, but the diagnosis of metopic suture synostosis remains controversial. The purpose of this study was to clarify, using geometric morphometric analysis, if a metopic ridge alone observed in cases of mild trigonocephaly represents a pathological phenomenon. Methods: Three different cranial morphologies were compared among patients up to 2 years old who were categorized into the true group, the mild group, and the normal group, based on the presence or absence of specific symptoms, history of cranioplasty for trigonocephaly, or lack of any abnormality on computed tomography. Using the obtained computed tomography images, 235 anatomical landmarks and semi-landmarks were plotted on the entire cranial surface for analysis of neurocranial morphology, and the cranial shapes represented by landmarks were analyzed using geometric morphometrics. Principal components of shape variations among specimens were then computed, based on the variance-covariance matrix of the Procrustes residuals of all specimens, and statistically analyzed. Results: The principal component analyses of the variations in endocranial shape, frontal bone shape, and occipital bone shape did not show any significant differences in cranial morphology between mild trigonocephaly and normal skulls; however, true trigonocephaly was found to differ significantly from mild trigonocephaly and normal skulls. Conclusions: These findings suggest that in assessments of cranial morphology, the presence of a ridge alone cannot be diagnosed as fundamentally pathological, and may represent normal morphology.

Lack of RAMP1 Signaling Suppresses Liver Regeneration and Angiogenesis Following Partial Hepatectomy in Mice.

BACKGROUND/AIM: The liver effectively restores both size and function following partial hepatectomy (PHx). Angiogenesis is crucial for the repair and regeneration of liver tissue post-PHx. Calcitonin gene-related peptide (CGRP) released from sensory nerves and its receptor-receptor activity-modifying protein 1 (RAMP1) are involved in angiogenesis. This study aimed to assess the role of RAMP1 signaling in angiogenesis during liver regeneration following PHx. MATERIALS AND METHODS: RAMP1 deficient (RAMP1-/-) and wild-type (WT) mice were subjected to PHx. RESULTS: RAMP1-/- mice demonstrated delayed liver regeneration, indicated by lower liver-to-body weight ratios compared to WT mice. This was associated with lower levels of Ki67+ hepatocytes and hepatic trophic growth factors. Additionally, RAMP1-/- mice exhibited lower levels of endothelial cell markers, including CD31, compared to WT mice. This reduction was associated with reduced levels of vascular endothelial growth factor (VEGF)-C, VEGF-D, and VEGF receptor 3 (VEGFR3). In WT mice with PHx, the administration of a VEGFR3 inhibitor reduced the liver-to-body weight ratio, Ki67+ hepatocytes, and VEGF-C/VEGFR3 expression levels in the liver compared to those in the vehicle-treated group. CONCLUSION: The deletion of RAMP1 signaling suppresses liver regeneration and angiogenesis through VEGFR3. Specific activation of RAMP1 signaling may represent a potential therapeutic strategy for liver regeneration following PHx.

Prostanoids Regulate Angiogenesis and Lymphangiogenesis in Pathological Conditions.

Angiogenesis, the formation of new blood vessels from the preexistent microvasculature, is an essential component of wound repair and tumor growth. Nonsteroidal anti-inflammatory drugs that suppress prostanoid biosynthesis are known to suppress the incidence and progression of malignancies including colorectal cancers, and also to delay the wound healing. However, the precise mechanisms are not fully elucidated. Accumulated results obtained from prostanoid receptor knockout mice indicate that a prostaglandin E-type receptor signaling EP3 in the host microenvironment is critical in tumor angiogenesis inducing vascular endothelial growth factor A (VEGF-A). Further, lymphangiogenesis was also enhanced by EP signaling via VEGF-C/D inductions in pathological settings. These indicate the importance of EP receptor to facilitate angiogenesis and lymphangiogenesis in vivo. Prostanoids act beyond their commonly understood activities in smooth muscle contraction and vasoactivity, both of which are quick responses elicited within several seconds on stimulations. Prostanoid receptor signaling will be a potential therapeutic target for disease conditions related to angiogenesis and lymphangiogenesis.

Deletion of RAMP1 Signaling Enhances Diet-induced Obesity and Fat Absorption via Intestinal Lacteals in Mice.

BACKGROUND/AIM: Intestinal lymphatic vessels (lacteals) play a critical role in the absorption and transport of dietary lipids into the circulation. Calcitonin gene-related peptide and receptor activity-modifying protein 1 (RAMP1) are involved in lymphatic vessel growth. This study aimed to examine the role of RAMP1 signaling in lacteal morphology and function in response to a high-fat diet (HFD). MATERIALS AND METHODS: RAMP1 deficient (RAMP1-/-) or wild-type (WT) mice were fed a normal diet (ND) or HFD for 8 weeks. RESULTS: RAMP1-/- mice fed a HFD had increased body weights compared to WT mice fed a HFD, which was associated with high levels of total cholesterol, triglycerides, and glucose. HFD-fed RAMP1-/- mice had shorter and wider lacteals than HFD-fed WT mice. HFD-fed RAMP1-/- mice had lower levels of lymphatic endothelial cell gene markers including vascular endothelial growth factor receptor 3 (VEGFR3) and lymphatic vascular growth factor VEGF-C than HFD-fed WT mice. The concentration of an absorbed lipid tracer in HFD-fed RAMP1-/- mice was higher than that in HFD-fed WT mice. The zipper-like continuous junctions were predominant in HFD-fed WT mice, while the button-like discontinuous junctions were predominant in HFD-fed RAMP1-/- mice. CONCLUSION: Deletion of RAMP1 signaling suppressed lacteal growth and VEGF-C/VEGFR3 expression but accelerated the uptake and transport of dietary fats through discontinuous junctions of lacteals, leading to excessive obesity. Specific activation of RAMP1 signaling may represent a target for the therapeutic management of diet-induced obesity.

Inhibition of TP signaling promotes endometriosis growth and neovascularization.

Endometriosis is highly dependent on angiogenesis and lymphangiogenesis. Prostaglandin E2, an arachidonic acid metabolite, has been shown to promote the formation of new blood and lymphatic vessels. However, the role of another arachidonic acid metabolite, thromboxane A2 (TXA2) in angiogenesis and lymphangiogenesis during endometriosis remains largely unexplored. Using a murine model of ectopic endometrial transplantation, fragments from the endometrium of WT donor mice were transplanted into the peritoneal walls of recipient WT mice (WT→WT), resulting in an increase in both the area and density of blood and lymphatic vessels. Upon transplantation of endometrial tissue from thromboxane prostanoid (TP) receptor (TXA2 receptor)­deficient (TP­/­) mice into TP­/­ mice (TP­/­â†’TP­/­), an increase in implant growth, angiogenesis, and lymphangiogenesis were observed along with upregulation of pro­angiogenic and lymphangiogenic factors, including vascular endothelial growth factors (VEGFs). Similar results were obtained using a thromboxane synthase (TXS) inhibitor in WT→WT mice. Furthermore, TP­/­â†’TP­/­ mice had a higher number of F4/80+ cells than that of WT→WT mice, with increased expression of genes related to the anti­inflammatory macrophage phenotype in endometrial lesions. In cultured bone marrow (BM)­derived macrophages, the levels of VEGF­A, VEGF­C, and VEGF­D decreased in a TP­dependent manner. Furthermore, TP signaling affected the polarization of cultured BM­derived macrophages to the anti­inflammatory phenotype. These findings imply that inhibition of TP signaling promotes endometrial implant growth and neovascularization.

Thromboxane prostanoid signaling in macrophages attenuates lymphedema and facilitates lymphangiogenesis in mice : TP signaling and lymphangiogenesis.

BACKGROUND: Accumulating evidence suggests that prostaglandin E2, an arachidonic acid (AA) metabolite, enhances lymphangiogenesis in response to inflammation. However, thromboxane A2 (TXA2), another AA metabolite, is not well known. Thus, this study aimed to determine the role of thromboxane prostanoid (TP) signaling in lymphangiogenesis in secondary lymphedema. METHODS AND RESULTS: Lymphedema was induced by the ablation of lymphatic vessels in mouse tails. Compared with wild-type mice, tail lymphedema in Tp-deficient mice was enhanced, which was associated with suppressed lymphangiogenesis as indicated by decreased lymphatic vessel area and pro-lymphangiogenesis-stimulating factors. Numerous macrophages were found in the tail tissues of Tp-deficient mice. Furthermore, the deletion of TP in macrophages increased tail edema and decreased lymphangiogenesis and pro-lymphangiogenic cytokines, which was accompanied by increased numbers of macrophages and gene expression related to a pro-inflammatory macrophage phenotype in tail tissues. In vivo microscopic studies revealed fluorescent dye leakage in the lymphatic vessels in the wounded tissues. CONCLUSIONS: The results suggest that TP signaling in macrophages promotes lymphangiogenesis and prevents tail lymphedema. TP signaling may be a therapeutic target for improving lymphedema-related symptoms by enhancing lymphangiogenesis.

A biologically active lipid, thromboxane, as a regulator of angiogenesis and lymphangiogenesis.

Thromboxane (TX) and prostaglandins are metabolites of arachidonic acid, a twenty-carbon unsaturated fatty acid, and have a variety of actions that are exerted via specific receptors. Angiogenesis is defined as the formation of new blood vessels from pre-existing vascular beds and is a critical component of pathological conditions, including inflammation and cancer. Lymphatic vessels play crucial roles in the regulation of interstitial fluid, immune surveillance, and the absorption of dietary fat from the intestine; and they are also involved in the pathogenesis of various diseases. Similar to angiogenesis, lymphangiogenesis, the formation of new lymphatic vessels, is a critical component of pathological conditions. The TP-dependent accumulation of platelets in microvessels has been reported to enhance angiogenesis under pathological conditions. Although the roles of some growth factors and cytokines in angiogenesis and lymphangiogenesis have been well characterized, accumulating evidence suggests that TX induces the production of proangiogenic and prolymphangiogenic factors through the activation of adenylate cyclase, and upregulates angiogenesis and lymphangiogenesis under disease conditions. In this review, we discuss the role of TX as a regulator of angiogenesis and lymphangiogenesis, and its emerging importance as a therapeutic target.

Responses of hepatic sinusoidal cells to liver ischemia-reperfusion injury.

The liver displays a remarkable regenerative capacity in response to acute liver injury. In addition to the proliferation of hepatocytes during liver regeneration, non-parenchymal cells, including liver macrophages, liver sinusoidal endothelial cells (LSECs), and hepatic stellate cells (HSCs) play critical roles in liver repair and regeneration. Liver ischemia-reperfusion injury (IRI) is a major cause of increased liver damage during liver resection, transplantation, and trauma. Impaired liver repair increases postoperative morbidity and mortality of patients who underwent liver surgery. Successful liver repair and regeneration after liver IRI requires coordinated interplay and synergic actions between hepatic resident cells and recruited cell components. However, the underlying mechanisms of liver repair after liver IRI are not well understood. Recent technological advances have revealed the heterogeneity of each liver cell component in the steady state and diseased livers. In this review, we describe the progress in the biology of liver non-parenchymal cells obtained from novel technological advances. We address the functional role of each cell component in response to liver IRI and the interactions between diverse immune repertoires and non-hematopoietic cell populations during the course of liver repair after liver IRI. We also discuss how these findings can help in the design of novel therapeutic approaches. Growing insights into the cellular interactions during liver IRI would enhance the pathology of liver IRI understanding comprehensively and further develop the strategies for improvement of liver repair.

The microsomal prostaglandin E synthase-1/prostaglandin E2 axis induces recovery from ischaemia via recruitment of regulatory T cells.

AIMS: Microsomal prostaglandin E synthase-1 (mPGES-1)/prostaglandin E2 (PGE2) induces angiogenesis through the prostaglandin E2 receptor (EP1-4). Among immune cells, regulatory T cells (Tregs), which inhibit immune responses, have been implicated in angiogenesis, and PGE2 is known to modulate the function and differentiation of Tregs. We hypothesized that mPGES-1/PGE2-EP signalling could contribute to recovery from ischaemic conditions by promoting the accumulation of Tregs. METHODS AND RESULTS: Wild-type (WT), mPGES-1-deficient (mPges-1-/-), and EP4 receptor-deficient (Ep4-/-) male mice, 6-8 weeks old, were used. Hindlimb ischaemia was induced by femoral artery ligation. Recovery from ischaemia was suppressed in mPges-1-/- mice and compared with WT mice. The number of accumulated forkhead box protein P3 (FoxP3)+ cells in ischaemic muscle tissue was decreased in mPges-1-/- mice compared with that in WT mice. Expression levels of transforming growth factor-ß (TGF-ß) and stromal cell derived factor-1 (SDF-1) in ischaemic tissue were also suppressed in mPges-1-/- mice. The number of accumulated FoxP3+ cells and blood flow recovery were suppressed when Tregs were depleted by injecting antibody against folate receptor 4 in WT mice but not in mPges-1-/- mice. Recovery from ischaemia was significantly suppressed in Ep4-/- mice compared with that in WT mice. Furthermore, mRNA levels of Foxp3 and Tgf-ß were suppressed in Ep4-/- mice. Moreover, the number of accumulated FoxP3+ cells in ischaemic tissue was diminished in Ep4-/- mice compared with that in Ep4+/+ mice. CONCLUSION: These findings suggested that mPGES-1/PGE2 induced neovascularization from ischaemia via EP4 by promoting the accumulation of Tregs. Highly selective EP4 agonists could be useful for the treatment of peripheral artery disease.

Expansion of iNKT Cells Promotes Liver Repair Following Hepatic Ischemia Reperfusion Injury.

BACKGROUND/AIM: Invariant natural killer T (iNKT) cells are involved in the initiation and resolution of inflammatory responses. We previously reported that activated iNKT cells facilitate liver repair after hepatic ischemia reperfusion (I/R) injury by accelerating macrophage polarization during the early phase of hepatic I/R injury. Upon activation with α-galactosylceramide (α-GalCer), iNKT cell numbers transiently decrease before increasing within 72 h of stimulation. In the present study, we examined the role of expanded hepatic iNKT cells in the late phase of hepatic I/R injury. MATERIALS AND METHODS: iNKT cells were activated by intraperitoneal injection of α-GalCer in male C57/BL6 mice at the induction of hepatic ischemia followed by reperfusion. RESULTS: Numbers of activated hepatic iNKT cells immediately diminished after hepatic I/R and reached minimal levels at 24 h and 48 h post-reperfusion. Numbers of hepatic iNKT cells then increased at 72 h and 96 h post-reperfusion to levels approximately 2-fold higher than in mice that underwent a sham operation. Liver repair as demonstrated by decreased necrotic area and increased expression of proliferating cell nuclear antigen (PCNA) was enhanced in α-GalCer-treated mice at 96 h post-reperfusion. Interleukin (IL)-13 production by proliferating iNKT cells was observed at 96 h post-reperfusion, which was associated with enhanced liver repair and increased numbers of reparative macrophages. CONCLUSION: Repopulation of hepatic iNKT cells promotes liver repair by stimulating macrophage phenotype switching in the late phase of hepatic I/R injury.

The Role of mPGES-1 in Promoting Granulation Tissue Angiogenesis Through Regulatory T-cell Accumulation.

BACKGROUND/AIM: Microsomal prostaglandin E synthase-1 (mPGES-1) is an enzyme, which catalyzes the final step of prostaglandin E2 (PGE2) synthesis. PGE2 in involved in wound-induced angiogenesis. Regulatory T cells (Tregs) regulate not only immune tolerance but also tissue repair and angiogenesis. We examined whether the mPGES-1/PGE2 axis contributes to wound-induced angiogenesis and granulation tissue formation through Treg accumulation. MATERIALS AND METHODS: The dorsal subcutaneous tissues of male mPGES-1-deficient (mPGES-1-/-) and C57BL/6 wild-type (WT) mice were implanted with polyurethane sponge disks. Angiogenesis was estimated by determining the wet weight of sponge tissues and the expression of proangiogenic factors including CD31, vascular endothelial growth factor (VEGF), and transforming growth factor ß (TGF-ß) in granulation tissues. RESULTS: Angiogenesis was suppressed in mPGES-1-/- mice compared with WT mice, which was associated with attenuated forkhead box P3 (Foxp3) expression and Foxp3+ Treg accumulation. The number of cells double-positive for Foxp3/TGFß and Foxp3/VEGF were lower in mPGES-1-/- mice than in WT mice. Neutralizing Tregs with antibodies (Abs) against CD25 or folate receptor 4 (FR4) inhibited the Foxp3+ Treg angiogenesis and accumulation in WT mice, but not in mPGES-1-/- mice. The topical application of PGE2 into the implanted sponge enhanced angiogenesis and accumulation of Tregs expressing TGFß and VEGF in WT and mPGES-1-/- mice. CONCLUSION: Tregs producing TGFß and VEGF accumulate in wounds and contribute to angiogenesis through mPGES-1-derived PGE2 mPGES-1 induction may control angiogenesis in skin wounds by recruiting Tregs.

Biologically active lipids in the regulation of lymphangiogenesis in disease states.

Lymphatic vessels have crucial roles in the regulation of interstitial fluids, immune surveillance, and the absorption of dietary fat in the intestine. Lymphatic function is also closely related to the pathogenesis of various disease states such as inflammation, lymphedema, endometriosis, liver dysfunction, and tumor metastasis. Lymphangiogenesis, the formation of new lymphatic vessels from pre-existing lymphatic vessels, is a critical determinant in the above conditions. Although the effect of growth factors on lymphangiogenesis is well-characterized, and biologically active lipids are known to affect smooth muscle contractility and vasoaction, there is accumulating evidence that biologically active lipids are also important inducers of growth factors and cytokines that regulate lymphangiogenesis. This review discusses recent advances in our understanding of biologically active lipids, including arachidonic acid metabolites, sphingosine 1-phosphate, and lysophosphatidic acid, as regulators of lymphangiogenesis, and the emerging importance of the lymphangiogenesis as a therapeutic target.

Morphological invariant of the midsagittal deep brain anatomy between humans and African great apes.

OBJECTIVES: Efforts have been made to mathematically reconstruct the brain morphology from human fossil crania to clarify the evolutionary changes in the brain that are associated with the emergence of human cognitive ability. However, because conventional reconstruction methods are based solely on the endocranial shape, deep brain structures cannot be estimated with sufficient accuracy. Our study aims to investigate the possible morphological correspondence between the cranial and deep brain morphologies based on humans and African great apes, with the goal of a more precise reconstruction of fossil brains. MATERIALS AND METHODS: Midsagittal endocranial and deep brain landmarks were obtained from magnetic resonance images of humans and three species of African great apes. The average midsagittal endocranial profile of all four species was calculated after Procrustes registration. The spatial deformation function from each of the endocranial profiles to the average endocranial profile was defined, and the brain landmarks enclosed in the endocranium were transformed using the deformation function to evaluate the interspecific variabilities of the positions of the brain landmarks on the average endocranial profile. RESULTS: The interspecific differences in the shape-normalized positions of the corpus callosum, anterior commissure, thalamus center, and brainstem were approximately within the range of 2% of the human cranial length, indicating that the interspecific variabilities of the positions of these deep brain structures were relatively small among the four species. DISCUSSION: Such an invariant relationship of the deep brain structure and the endocranium that encloses the brain can potentially be utilized to reconstruct the brains of fossil hominins.

The role of thromboxane prostanoid receptor signaling in gastric ulcer healing.

The process of gastric ulcer healing includes cell migration, proliferation, angiogenesis and re-epithelialization. Platelets contain angiogenesis stimulating factors that induce angiogenesis. Thromboxane A2 (TXA2 ) not only induces platelet activity but also angiogenesis. This study investigated the role of TXA2 in gastric ulcer healing using TXA2 receptor knockout (TPKO) mice. Gastric ulcer healing was suppressed by treatment with the TXA2 synthase inhibitor OKY-046 and the TXA2 receptor antagonist S-1452 compared with vehicle-treated mice. TPKO showed delayed gastric ulcer healing compared with wild-type mice (WT). The number of microvessels and CD31 expression were lower in TPKO than in WT mice, and TPKO suppressed the expression of transforming growth factor beta (TGF-ß) and vascular endothelial growth factor A (VEGF-A) in areas around gastric ulcers. Immunofluorescence assays showed that TGF-ß and VEGF-A co-localized with platelets. Gastric ulcer healing was significantly reduced in WT mice transplanted with TPKO compared with WT bone marrow. These results suggested that TP signalling on platelets facilitates gastric ulcer healing through TGF-ß and VEGF-A.

Morphological differences in the calcaneus among extant great apes investigated by three-dimensional geometric morphometrics.

Investigating the morphological differences of the calcaneus in humans and great apes is crucial for reconstructing locomotor repertories of fossil hominins. However, morphological variations in the calcaneus of the great apes (chimpanzees, gorillas, and orangutans) have not been sufficiently studied. This study aims to clarify variations in calcaneal morphology among great apes based on three-dimensional geometric morphometrics. A total of 556 landmarks and semilandmarks were placed on the calcaneal surface to calculate the principal components of shape variations among specimens. Clear interspecific differences in calcaneal morphology were extracted, corresponding to the degree of arboreality of the three species. The most arboreal orangutans possessed comparatively more slender calcaneal tuberosity and deeper pivot region of the cuboid articular surface than chimpanzees and gorillas. However, the most terrestrial gorillas exhibited longer lever arm of the triceps surae muscle, larger peroneal trochlea, more concave plantar surface, more inverted calcaneal tuberosity, more everted cuboid articular surface, and more prominent plantar process than the orangutans and chimpanzees. These interspecific differences possibly reflect the functional adaptation of the calcaneus to locomotor behavior in great apes. Such information might be useful for inferring foot functions and reconstructing the locomotion of fossil hominoids and hominids.

Activation of iNKT Cells Facilitates Liver Repair After Hepatic Ischemia Reperfusion Injury Through Acceleration of Macrophage Polarization.

Macrophage polarization is critical for liver tissue repair following acute liver injury. However, the underlying mechanisms of macrophage phenotype switching are not well defined. Invariant natural killer T (iNKT) cells orchestrate tissue inflammation and tissue repair by regulating cytokine production. Herein, we examined whether iNKT cells played an important role in liver repair after hepatic ischemia-reperfusion (I/R) injury by affecting macrophage polarization. To this end, we subjected male C57BL/6 mice to hepatic I/R injury, and mice received an intraperitoneal (ip) injection of α-galactosylceramide (α-GalCer) or vehicle. Compared with that of the vehicle, α-GalCer administration resulted in the promotion of liver repair accompanied by acceleration of macrophage differentiation and by increases in the numbers of Ly6Chigh pro-inflammatory macrophages and Ly6Clow reparative macrophages. iNKT cells activated with α-GalCer produced interleukin (IL)-4 and interferon (IFN)-γ. Treatment with anti-IL-4 antibodies delayed liver repair, which was associated with an increased number of Ly6Chigh macrophages and a decreased number of Ly6Clow macrophages. Treatment with anti-IFN-γ antibodies promoted liver repair, associated with reduced the number of Ly6Chigh macrophages, but did not change the number of Ly6Clow macrophages. Bone marrow-derived macrophages up-regulated the expression of genes related to both a pro-inflammatory and a reparative phenotype when co-cultured with activated iNKT cells. Anti-IL-4 antibodies increased the levels of pro-inflammatory macrophage-related genes and decreased those of reparative macrophage-related genes in cultured macrophages, while anti-IFN-γ antibodies reversed the polarization of macrophages. Cd1d-deficient mice showed delayed liver repair and suppressed macrophage switching, compared with that in wild-type mice. These results suggest that the activation of iNKT cells by α-GalCer facilitated liver repair after hepatic I/R injury by both IL-4-and IFN-γ-mediated acceleration of macrophage polarization. Therefore, the activation of iNKT cells may represent a therapeutic tool for liver repair after hepatic I/R injury.

Recovery of Liver Sinusoidal Endothelial Cells Following Monocrotaline-induced Liver Injury.

BACKGROUND/AIM: Although the pathology of sinusoidal obstruction syndrome (SOS) is characterized by damage to liver sinusoidal endothelial cells (LSECs), the processes underlying LSEC repair are incompletely understood. The angiopoietin (Ang)/Tie system contributes to angiogenesis. The present study aimed to examine the processes of LSEC repair and the involvement of the Ang/Tie pathway in LSEC recovery. MATERIALS AND METHODS: Experimentally, SOS was induced by intraperitoneal injection of monocrotaline (MCT) to C57/BL6 mice. RESULTS: Levels of LSEC markers were up-regulated during the repair phase of MCT-induced hepatotoxicity. The damaged LSECs recovered from the injury by expanding LSECs expressing lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1) in the peri-central area of MCT-injured livers, while LSECs in the same area of uninjured livers lacked LYVE-1 expression. Bone marrow (BM)-derived cells did not incorporate into the restored LSECs. Tie2 expression was related to LSEC recovery in MCT-injured liver tissue. CONCLUSION: The resident LSECs neighboring uninjured tissue replace damaged LSECs in MCT-injured livers. Tie2 is involved in LSEC recovery from MCT-induced hepatotoxicity.

VEGFR1-tyrosine kinase signaling in pulmonary fibrosis.

Vascular endothelial growth factor (VEGF) is not only an important factor for angiogenesis but also lung development and homeostasis. VEGF-A binds three tyrosine kinase (TK) receptors VEGFR1-3. Idiopathic pulmonary fibrosis (IPF) is one of the poor prognoses of lung diseases. The relationship of VEGF and IPF remains to be clarified. Treatment with nintedanib used for the treatment of IPF reduced fibroblast proliferation, inhibited TK receptors, platelet-derived growth factor receptor (PDGFR), fibroblast growth factor receptor (FGFR), and VEGFR. Because the effect of that treatment is still not satisfactory, the emergence of new therapeutic agents is needed. This review describes the enhancement of pulmonary fibrosis by VEGFR1-TK signal and suggests that the blocking of the VEGFR1-TK signal may be useful for the treatment of pulmonary fibrosis.

Macrophages contribute to liver repair after monocrotaline-induced liver injury via SDF-1/CXCR4.

Monocrotaline (MCT) administration induces liver injury in rodents that mimics the pathology of human sinusoidal obstruction syndrome. MCT-induced SOS models are used to investigate the mechanism of injury and optimize treatment strategies. However, the processes underlying liver repair are largely unknown. Specifically, the role of macrophages, the key drivers of liver repair, has not been elucidated. The current study aimed to examine the role of macrophages in the repair of MCT-induced liver injury in male C57/BL6 mice. Maximal liver injury occurred at 48 h post-MCT treatment, followed by repair at 120 h post-treatment. Immunofluorescence analysis revealed that CD68+ macrophages were recruited to the injured regions after MCT treatment. This was associated with the decreased expression of genes related to a pro-inflammatory macrophage phenotype and the increased expression of those associated with a reparative macrophage phenotype during the repair phase. The results also revealed that stromal cell-derived factor-1 (SDF-1) and its receptor C-X-C chemokine receptor-4 (CXCR4) were upregulated, and CD68+ macrophages were co-localized with CXCR4 expression. Treatment of mice with AMD3100, a CXCR4 antagonist, delayed liver repair and increased the expression of genes related to a pro-inflammatory macrophage phenotype. In contrast, SDF-1 treatment stimulated liver repair and increased the expression of genes related to a reparative macrophage phenotype. The results suggested that macrophages accumulate in the liver and repair damaged tissue after MCT treatment, and that the SDF-1-CXCR4 axis is involved in this process.