KAI1(CD82) is a key molecule to control angiogenesis and switch angiogenic milieu to quiescent state

BACKGROUND

Little is known about endogenous inhibitors of angiogenic growth factors. In this study, we identified a novel endogenous anti-angiogenic factor expressed in pericytes and clarified its underlying mechanism and clinical significance.

METHODS

Herein, we found Kai1 knockout mice showed significantly enhanced angiogenesis. Then, we investigated the anti-angiogenic roll of Kai1 in vitro and in vivo.

RESULTS

KAI1 was mainly expressed in pericytes rather than in endothelial cells. It localized at the membrane surface after palmitoylation by zDHHC4 enzyme and induced LIF through the Src/p53 pathway. LIF released from pericytes in turn suppressed angiogenic factors in endothelial cells as well as in pericytes themselves, leading to inhibition of angiogenesis. Interestingly, KAI1 had another mechanism to inhibit angiogenesis: It directly bound to VEGF and PDGF and inhibited activation of their receptors. In the two different in vivo cancer models, KAI1 supplementation significantly inhibited tumor angiogenesis and growth. A peptide derived from the large extracellular loop of KAI1 has been shown to have anti-angiogenic effects to block the progression of breast cancer and retinal neovascularization in vivo.

CONCLUSIONS

KAI1 from PC is a novel molecular regulator that counterbalances the effect of angiogenic factors.

Priming mobilized peripheral blood mononuclear cells with the "activated platelet supernatant" enhances the efficacy of cell therapy for myocardial infarction of rats

AIM

Various methods are used to augment the efficacy of cell therapy in myocardial infarction (MI). In this study, we used the "activated platelet supernatant (APS)" to prime autologous "granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cells ((mob) PBMCs)" and investigated the efficacy of cell-based therapy in MI.

METHOD

Rat (mob) PBMCs were isolated after daily subcutaneous injections of G-CSF at 100 μg/kg for 3 days. APS was isolated separately after activating rat platelets with thrombin 0.5 U/mL for 2 hours. Priming was performed with APS for 6 hours. To check the paracrine effect of primed (mob) PBMCs, we used the 36-hour culture supernatant of the primed cells. A rat MI model was used for an in vivo model.

RESULT

Cytokines such as IL-1β, IL-10, and TGFβ were 3.7±0.9-fold, 3.4±1.2-fold, and 1.2±0.1-fold higher in APS, respectively, compared with naïve platelet supernatant. By APS priming, (mob) PBMCs showed M2 polarization and upregulation of angiogenic molecules (i.e., TEK, IL-10, CXCL1, and CX3CR1). APS-primed (mob) PBMCs had a 2.3-fold increased adhesion ability, induced by upregulated integrins. Rat endothelial cells cultured in the 36-hour culture supernatant of APS-primed (mob) PBMCs showed a 1.6-fold augmented proliferation and capillary network formation. In vivo transplantation of APS-primed (mob) PBMCs into rat MI models showed a significant trend of reduction in fibrosis area (P=.001) and wall thinning (P=.030), which lead to improvement in cardiac function measured by echocardiography.

CONCLUSION

Our data reveal that APS priming can enhance the wound-healing potential of (mob) PBMCs. APS priming may be a promising method for cell-based therapy of MI.

CD82/KAI1 Maintains the Dormancy of Long-Term Hematopoietic Stem Cells through Interaction with DARC-Expressing Macrophages

Hematopoiesis is regulated by crosstalk between long-term repopulating hematopoietic stem cells (LT-HSCs) and supporting niche cells in the bone marrow (BM). Here, we examine the role of CD82/KAI1 in niche-mediated LT-HSC maintenance. We found that CD82/KAI1 is expressed predominantly on LT-HSCs and rarely on other hematopoietic stem-progenitor cells (HSPCs). In Cd82(-/-) mice, LT-HSCs were selectively lost as they exited from quiescence and differentiated. Mechanistically, CD82-based TGF-β1/Smad3 signaling leads to induction of CDK inhibitors and cell-cycle inhibition. The CD82 binding partner DARC/CD234 is expressed on macrophages and stabilizes CD82 on LT-HSCs, promoting their quiescence. When DARC(+) BM macrophages were ablated, the level of surface CD82 on LT-HSCs decreased, leading to cell-cycle entry, proliferation, and differentiation. A similar interaction appears to be relevant for human HSPCs. Thus, CD82 is a functional surface marker of LT-HSCs that maintains quiescence through interaction with DARC-expressing macrophages in the BM stem cell niche.

Abstract P120: Improving the Angiogenic Abilities of Mobilized Peripheral Blood Stem Cells Achieved by Priming with Activated Platelet Supernatant for Regenerative Cell Therapy

Platelets play a critical role in hemostasis and also have ability to promote angiogenesis and tissue repair by secreting of numerous cytokine and making angiogenic condition. We investigated whether autologous ‘activated platelet supernatant (APS)’ has effect on enhancing pro-angiogenic potential of peripheral blood stem cells (PBSC) for stem cell-based therapy for ischemic diseases. Granulocyte-colony stimulating factor (G-CSF) mobilized peripheral blood stem cells (mobPBSC) were isolated from healthy volunteers, while APS was collected from platelet rich plasma by thrombin activation. mobPBSCs were primed with APS (APS primed mobPBSCs) for 6 hours, and APS primed mobPBSCs characterized their angiogenic ability. For the safety analysis, we estimated the thrombogenicity of platelets in whole blood mixed with APS primed mobPBSCs by expression of glycoprotein IIb and IIIa on platelets. APS had a higher level of various cytokines, such as IL8, IL17, PDGF and VEGF than naïve platelet supernatants. And APS primed mobPBSCs had more expression of angiogenic factors, surface markers (i.e. CD34, CD31, and CXCR4) and integrins (integrin α5, β1 and β2) than Veh primed and Pre primed mobPBSC. Also APS primed mobPBSCs were polarized toward CD14++/CD16+ pro-angiogenic monocytes. And result in adhesion to endothelial cells and fibronectin which represents cell to cell and cell to extracellular matrix adhesion, respectively. The culture supernatant of APS-primed mobPBSCs contained high levels of IL8, IL10, IL17 and TNFα, and augmented proliferation and capillary network formation of HUVEC. In-vivo transplantation of APS-primed mobPBSC into athymic mice ischemic hindlimbs and Matrigel plugs elicited vessel differentiation and tissue repair. In thrombogenicity test, platelet activity increased after mixing whole blood with mobPBSC regardless of the priming agent. However, this was reduced by pretreatment of aspirin, which is an antiplatelet agent prescribed to patients with ischemic diseases. Our data demonstrate that mobPBSCs primed with APS improve angiogenic potential, and that can be adjunctive strategy to enhance the efficiency of stem cell therapy for ischemic diseases.

Erythropoietin priming improves the vasculogenic potential of G-CSF mobilized human peripheral blood mononuclear cells

AIMS

From our previous clinical trials, intracoronary infusion of granulocyte-colony stimulating factor (G-CSF)-mobilized peripheral blood mononuclear cells ((mob)PBMCs) proved to be effective in improving myocardial contractility and reducing infarct volume in acute myocardial infarction. We tested the effect of priming (mob)PBMCs with erythropoietin (EPO) to augment its therapeutic efficacy.

METHODS AND RESULTS

(mob)PBMCs were obtained from healthy volunteers after a 3-day subcutaneous injection of G-CSF (10 μg/kg). About 40% of (mob)PBMCs were EPO receptor (EPOR) (+) and responded to 6 h EPO-priming (10 IU/mL) by increasing the expression of vasculogenic factors (i.e. IL8, IL10, bFGF, PDGF, MMP9) and adhesion molecules (i.e. integrin αV, β1, β2, β8) through the JAK2 and Akt pathway. These responses were also observed in PBMCs from elderly patients with coronary disease. The conditioned media from EPO-primed (mob)PBMCs contained various cytokines such as IL8, IL10, TNFα, and PDGF, which enhanced the migration and tube formation capability of endothelial cells. EPO-primed (mob)PBMCs also showed increased adhesion on endothelial cells or fibronectin. Augmented vasculogenic potential of EPO-primed (mob)PBMCs was confirmed in a Matrigel plug assay, ischaemic hindlimb, and myocardial infarction models of athymic nude mice. There were two action mechanisms: (i) cellular effects confirmed by direct incorporation of human (mob)PBSCs into mouse vasculature and (ii) indirect humoral effects confirmed by the therapeutic effect of the supernatant of EPO-primed (mob)PBMCs.

CONCLUSION

Brief ex vivo EPO-priming is a novel method to augment the vasculogenic potential of human (mob)PBMCs, which would help to achieve better results after intracoronary infusion in myocardial infarction patients.

Activated platelet supernatant can augment the angiogenic potential of human peripheral blood stem cells mobilized from bone marrow by G-CSF

Platelets not only play a role in hemostasis, but they also promote angiogenesis and tissue recovery by releasing various cytokines and making an angiogenic milieu. Here, we examined autologous 'activated platelet supernatant (APS)' as a priming agent for stem cells; thereby enhance their pro-angiogenic potential and efficacy of stem cell-based therapy for ischemic diseases. The mobilized peripheral blood stem cells ((mob)PBSCs) were isolated from healthy volunteers after subcutaneous injection of granulocyte-colony stimulating factor. APS was collected separately from the platelet rich plasma after activation by thrombin. (mob)PBSCs were primed for 6h before analysis. Compared to naive platelet supernatants, APS had a higher level of various cytokines, such as IL8, IL17, PDGF and VEGF. APS-priming for 6h induced (mob)PBSCs to express key angiogenic factors, surface markers (i.e. CD34, CD31, and CXCR4) and integrins (integrins α5, β1 and β2). Also (mob)PBSCs were polarized toward CD14(++)/CD16(+) pro-angiogenic monocytes. The priming effect was reproduced by an in vitro reconstruction of APS. Through this phenotype, APS-priming increased cell-cell adhesion and cell-extracellular matrix adhesion. The culture supernatant of APS-primed (mob)PBSCs contained high levels of IL8, IL10, IL17 and TNFα, and augmented proliferation and capillary network formation of human umbilical vein endothelial cells. In vivo transplantation of APS-primed (mob)PBSCs into athymic mice ischemic hindlimbs and Matrigel plugs elicited vessel differentiation and tissue repair. In safety analysis, platelet activity increased after mixing with (mob)PBSCs regardless of priming, which was normalized by aspirin treatment. Collectively, our data identify that APS-priming can enhance the angiogenic potential of (mob)PBSCs, which can be used as an adjunctive strategy to improve the efficacy of cell therapy for ischemic diseases.

Highly angiogenic CXCR4(+)CD31(+) monocyte subset derived from 3D culture of human peripheral blood

Ex vivo expansion of human circulating angiogenic cells is a major challenge in autologous cell therapy for ischemic diseases. Here, we demonstrate that hematosphere-derived CXCR4(+)CD31(+) myeloid cells using peripheral blood possess robust proangiogenic capacity such as formation of vessel-like structures and tip cell-like morphology in Matrigel. We also found that CD31 positive myeloid cells are principal cellular component of hematospheres by magnetic cell sorting. Flow cytometry analysis showed that fresh peripheral blood contained 40.3 ± 15.2% of CXCR4(+)CD31(+) myeloid cells, but at day 5 of hematosphere culture, most of myeloid cells were CXCR4(+)CD31(+) by 86.9 ± 5.4%. Hematosphere culture significantly increased the production of angiogenic niche-supporting cytokines. Moreover, CD31-homophilic interaction and VEGF-VEGF receptor loop signaling were essential for sphere formation and acquisition of angiogenic capacity in hematospheres. Matrigel plug and ischemic hindlimb model provide in vivo evidence that hematosphere-derived myeloid cells have highly vasculogenic capacities, participate in new and mature vessel formation, and exert therapeutic effects on ischemic hindlimb. In conclusion, our strategy for ex vivo expansion of human CXCR4(+)CD31(+) angiogenic cells using hematospheres provides an autologous therapeutic cell source for ischemic diseases and a new model for investigating the microenvironment of angiogenesis.

Alteration of the CNS pathway to the hippocampus in a mouse model of Niemann-Pick, type C disease

Niemann-Pick type C disease (NPC) is an autosomal recessive disorder that results in premature death due to progressive neurodegeneration including dementia. To understand neuronal pathways connecting to the hippocampus, retrograde transneuronal labeling method with Bartha strain of pseudorabies virus (PRV) was employed in 40 NPC+/+, NPC+/- and NPC-/- mice. Immunohistochemistry using polyclonal antibody against PRV and streological counting were used. The number of neurons and synapse in CA2&3 regions of the hippocampus decreased dramatically in the NPC-/- mouse compared to the NPC+/+ or +/- mouse. The number of PRV positive cell was significantly decreased in several regions including the entorhinal and piriform cortex in the NPC-/- mouse. More severely, lateral septal dorsal nucleus, dorsal entorhinal cortex and medial geniculate body showed no positive labeling in the NPC-/- mouse. However, the hippocampus, medial septal and supramammilary nuclei showed increased immunoreactivity in the NPC-/- mouse. Our data suggest that the synaptic loss and discontinuity of the CNS hippocampal pathway may contribute to understanding the mechanism of symptoms and functional disabilities such as memory and learning disturbance in NPC patients.

Clonal expansion of infiltrating T cells in the spinal cords of SJL/J mice infected with Theiler's virus

Intracerebral infection of susceptible mice with Theiler's murine encephalomyelitis virus results in immune-mediated inflammatory demyelination in the white matter and consequent clinical symptoms. This system has been utilized as an important virus model for human multiple sclerosis. Although the potential involvement of virus-specific Th cells has been studied extensively, very little is known about the nature of T cells infiltrating the CNS during viral infection and their role in the development of demyelinating disease. In this study, the clonal nature of T cells in the spinal cord during the disease course was analyzed using size spectratyping and sequencing of the TCR beta-chain CDR3 region. These studies clearly indicate that T cells are clonally expanded in the CNS after viral infection, although the overall TCR repertoire appears to be diverse. The clonal expansion appears to be Ag-driven in that it includes Th cells specific for known viral epitopes. Interestingly, such restricted accumulation of T cells was not detectable in the infiltrates of mice with proteolipid protein peptide-induced experimental autoimmune encephalomyelitis. The initial T cell repertoire (7-9 days postinfection) seems to be more diverse than that observed in the later stage (65 days) of virally induced demyelination, despite the more restricted utilization of Vbeta subfamilies. These results strongly suggest continuous stimulation and clonal expansion of virus-specific T cells in the CNS of Theiler's murine encephalomyelitis virus-infected mice during the entire course of demyelinating disease.

Diverse fine specificity and receptor repertoire of T cells reactive to the major VP1 epitope (VP1230-250) of Theiler's virus: V beta restriction correlates with T cell recognition of the c-terminal residue

Theiler's murine encephalomyelitis virus induces chronic demyelinating disease in genetically susceptible mice. The histopathological and immunological manifestation of the disease closely resembles human multiple sclerosis, and, thus, this system serves as a relevant infectious model for multiple sclerosis. The pathogenesis of demyelination appears to be mediated by the inflammatory Th1 response to viral epitopes. In this study, T cell repertoire reactive to the major pathogenic VP1 epitope region (VP1233-250) was analyzed. Diverse minimal T cell epitopes were found within this region, and yet close to 50% of the VP1-reactive T cell hybridomas used V beta 16. The majority (8/11) of the V beta 16+ T cells required the C-terminal amino acid residue on the epitope, valine at position 245, and every T cell hybridoma recognizing this C-terminal residue expressed V beta 16. However, the complementarity-determining region 3 sequences of the V beta 16+ T cell hybridomas were markedly heterogeneous. In contrast, such a restriction was not found in the V alpha usage. Only restricted residues at this C-terminal position allowed for T cell activation, suggesting that V beta 16 may recognize this terminal residue. Further functional competition analysis for TCR and MHC class II-contacting residues indicate that many different residues can be involved in the class II and/or TCR binding depending on the T cell population, even if they recognize the identical minimal epitope region. Thus, recognition of the C-terminal residue of a minimal T cell epitope may associate with a particular V beta (but not V alpha) subfamily-specific sequence, resulting in a highly restricted V beta repertoire of the epitope-specific T cells.

Susceptibility of penicillin-susceptible and -resistant pneumococci to CFC-222, a new fluoroquinolone

The in-vitro activity of 12 antibacterial agents against 98 clinical isolates of Streptococcus pneumoniae, including 54 penicillin-resistant strains, was determined by a standardized broth microdilution method. CFC-222, vancomycin and imipenem were the most active agents, with an MIC90 of 0.5 mg/L for the test strains. CFC-222 was 16-fold more potent than ciprofloxacin and ofloxacin against all strains tested, including both penicillin-susceptible and -resistant strains. The anti-pneumococcal activity of fluoroquinolones was not affected by penicillin susceptibility. These results indicate that CFC-222 is potentially useful for treating infection caused by penicillin-resistant strains of S. pneumoniae.

A spontaneous low-pathogenic variant of Theiler's virus contains an amino acid substitution within the predominant VP1(233-250) T-cell epitope

Theiler's murine encephalomyelitis virus (TMEV) induces immune-mediated demyelination after intracerebral inoculation of the virus into susceptible mouse strains. We isolated from a TMEV BeAn 8386 viral stock, a low-pathogenic variant which requires greater than a 10,000-fold increase in viral inoculation for the manifestation of detectable clinical signs. Intracerebral inoculation of this variant virus induced a strong, long-lasting, protective immunity from the demyelinating disease caused by pathogenic TMEV. The levels of antibodies to the whole virus as well as to the major linear epitopes were similar in mice infected with either the variant or wild-type virus. However, persistence of the variant virus in the central nervous system (CNS) of mice was significantly lower than that of the pathogenic virus. In addition, the T-cell response to the predominant VP1 (VP1(233-250)) epitope in mice infected with the variant virus was significantly weaker than that in mice infected with the parent virus, while similar T-cell responses were induced against another predominant epitope (VP2(74-86)). Further analyses indicated that a change of lysine to arginine at position 244 of VP1, which is the only amino acid difference in the P1 region, is responsible for such differential T-cell recognition. Thus, the difference in the T-cell reactivity to this VP1 region as well as the low level of viral persistence in the CNS may account for the low pathogenicity of this spontaneous variant virus.

In vitro and in vivo antibacterial efficacies of CFC-222, a new fluoroquinolone

CFC-222 is a novel fluoroquinolone containing a C-7 bicyclic amine moiety with potent antibacterial activities against gram-positive, gram-negative, and anaerobic organisms. We compared the in vitro and in vivo activities of CFC-222 with those of ciprofloxacin, ofloxacin, and lomefloxacin. CFC-222 was more active than the other fluoroquinolones tested against gram-positive bacteria. CFC-222 was particularly active against Streptococcus pneumoniae (MIC at which 90% of isolates are inhibited [MIC90], 0.2 microg/ml), Staphylococcus aureus (MIC90, 0.2 microg/ml for ciprofloxacin-susceptible strains), and Enterococcus faecalis (MIC90, 0.39 microg/ml). Against Escherichia coli and other members of the family Enterobacteriaceae, CFC-222 was slightly less active than ciprofloxacin (MIC90s for E. coli, 0.1 and 0.025 microg/ml, respectively). The in vitro activity of CFC-222 was not influenced by inoculum size, medium composition, or the presence of horse serum. However, its activity was decreased significantly by a change in the pH of the medium from 7.0 to 6.0, as was the case for the other quinolones tested. The in vivo protective efficacy of CFC-222 by oral administration was greater than those of the other quinolones tested in a mouse model of intraperitoneally inoculated systemic infection caused by S. aureus. CFC-222 exhibited efficacy comparable to that of ciprofloxacin in the same model of infection caused by gram-negative organisms, such as E. coli and Klebsiella pneumoniae. In this infection model, CFC-222 was slightly less active than ciprofloxacin against Pseudomonas aeruginosa. These results suggest that CFC-222 may be a promising therapeutic agent in various bacterial infections.

Expression of TJ6 during pregnancy

PROBLEM

TJ6 will be one of the molecules involved in fetal-specific immune suppression during pregnancy. In the mouse and human decidua, the regulation of uterine natural killer (uNK) cells is important during pregnancy.

METHOD OF STUDY

To further understand the possible functions of TJ6 during pregnancy, syngeneic, allogeneic, and mutant mice were examined for TJ6 expression.

RESULTS

Immunoblotting showed that TJ6 protein was expressed on most of the placenta-associated mononuclear cells, and the size was 70-72 kDa at all stages of pregnancy. The expression of TJ6 mRNA was studied by a ribonuclease protection assay in syngeneic and allogeneic matings, and in immune-deficient mice of genotypes scid/scid and scid/scid.bg/bg.

CONCLUSIONS

Genetic disparity, lack of T and B lymphocytes, and loss of NK lytic function had no significant effect on the expression of TJ6 mRNA.

Expression of a membrane form of the pregnancy-associated protein TJ6 on lymphocytes

TJ6 is a novel protein which has immunosuppressive activity and may have a functional role in fetal allograft survival during pregnancy. Initial studies indicated that when mice were treated with an anti-TJ6 binding mAb early in pregnancy, the pregnancies were completely ablated and that TJ6 expression is enhanced dramatically during pregnancy. In addition we have cloned the cDNA for TJ6 which encodes a possible transmembrane domain that may include six to seven transmembrane regions. Therefore, we examined TJ6 expression on PBL of pregnant and non-pregnant women and found that TJ6 is expressed primarily on CD19+ B cells from pregnant but not nonpregnant women. TJ6 was not expressed on CD3+ lymphocytes from either group but was expressed on CD56+ cells from a small population of pregnant women which preliminary data indicate may correlate with the occurrence of spontaneous abortion in these women. Here we also show that TJ6 transcripts are highly expressed in the developing fetoplacental unit as well as in the developing thymus. We also begin to characterize the expression of TJ6 isoforms in an acute lymphocytic leukemia cell line (SB), murine thymus, and the developing murine fetoplacental unit, as well as the expression of a membrane form of TJ6 present on human lymphocytes during pregnancy. All of these cells and tissues expressed TJ6 proteins which were smaller than predicted based on either the cDNA sequence or the in vitro translation even though they expressed mRNA similar in size. The TJ6 isoforms varied in size from the 45-kDa isoform in SB cells to the 52-kDa isoform of the fetoplacental unit to a 70-kDa isoform in murine thymus. Flow cytometric analysis also demonstrated that similar to the CD19+ B cells from pregnant women, TJ6 is expressed on the surface of SB cells.