Luciana Vieira de Moraes

SJL Dystrophic Mice Express a Significant Amount of Human Muscle Proteins Following Systemic Delivery of Human Adipose‐Derived Stromal Cells Without Immunosuppression

Limb‐girdle muscular dystrophies (LGMDs) are a heterogeneous group of disorders characterized by progressive degeneration of skeletal muscle caused by the absence of or defective muscular proteins. The murine model for limb‐girdle muscular dystrophy 2B (LGMD2B), the SJL mice, carries a deletion in the dysferlin gene that causes a reduction in the protein levels to 15% of normal. The mice show muscle weakness that begins at 4–6 weeks and is nearly complete by 8 months of age. The possibility of restoring the defective muscle protein and improving muscular performance by cell therapy is a promising approach for the treatment of LGMDs or other forms of progressive muscular dystrophies. Here we have injected human adipose stromal cells (hASCs) into the SJL mice, without immunosuppression, aiming to assess their ability to engraft into recipient dystrophic muscle after systemic delivery; form chimeric human/mouse muscle fibers; express human muscle proteins in the dystrophic host and improve muscular performance. We show for the first time that hASCs are not rejected after systemic injection even without immunosuppression, are able to fuse with the host muscle, express a significant amount of human muscle proteins, and improve motor ability of injected animals. These results may have important applications for future therapy in patients with different forms of muscular dystrophies.

Intravital Placenta Imaging Reveals Microcirculatory Dynamics Impact on Sequestration and Phagocytosis of Plasmodium-Infected Erythrocytes

Malaria in pregnancy is exquisitely aggressive, causing a range of adverse maternal and fetal outcomes prominently linked to Plasmodium-infected erythrocyte cytoadherence to fetal trophoblast. To elucidate the physiopathology of infected erythrocytes (IE) sequestration in the placenta we devised an experimental system for intravital placental examination of P. berghei-infected mice. BALB/c females were mated to C57Bl/6 CFP+ male mice and infected with GFP+ P. berghei IE, and at gestational day 18, placentas were exposed for time-lapse imaging acquisition under two-photon microscopy. Real-time images and quantitative measurements revealed that trophoblast conformational changes transiently restrain blood flow in the mouse placental labyrinth. The complex dynamics of placental microcirculation promotes IE accumulation in maternal blood spaces with low blood flow and allows the establishment of stable IE-trophoblast contacts. Further, we show that the fate of sequestered IE includes engulfment by both macrophagic and trophoblastic fetal-derived cells. These findings reinforce the current paradigm that IE interact with the trophoblast and provide definitive evidence on two novel pathogenesis mechanisms: (1) trophoblast layer controls placental microcirculation promoting IE sequestration; and (2) fetal-derived placental cells engulf sequestered IE.

Expansion of CD4+ CD25+ Foxp3+ T cells by bone marrow-derived dendritic cells

Dendritic cells (DCs) are the most important antigen‐presenting cells of the immune system and have a crucial role in T‐lymphocyte activation and adaptive immunity initiation. However, DCs have also been implicated in maintaining immunological tolerance. In this study, we evaluated changes in the CD4+ CD25+ Foxp3+ T‐cell population after co‐culture of lymph node cells from BALB/c mice with syngeneic bone marrow‐derived DCs. Our results showed an increase in CD4+ CD25+ Foxp3+ T cells after co‐culture which occurred regardless of the activation state of DCs and the presence of allogeneic apoptotic cells; however, it was greater when DCs were immature and were pulsed with the alloantigen. Interestingly, syngeneic apoptotic thymocytes were not as efficient as allogeneic apoptotic cells in expanding the CD4+ CD25+ Foxp3+ T‐cell population. In all experimental settings, DCs produced high amounts of transforming growth factor (TGF)‐β. The presence of allogeneic apoptotic cells induced interleukin (IL)‐2 production in immature and mature DC cultures. This cytokine was also detected in the supernatants under all experimental conditions and enhanced when immature DCs were pulsed with the alloantigen. CD4+ CD25+ Foxp3+ T‐cell expansion during co‐culture of lymph node cells with DCs strongly suggested that the presence of alloantigen enhanced the number of regulatory T cells (Tregs) in vitro. Our data also suggest a role for both TGF‐β and IL‐2 in the augmentation of the CD4+ CD25+ Foxp3+ population.

Administration of M. leprae Hsp65 Interferes with the Murine Lupus Progression

The heat shock protein [Hsp] family guides several steps during protein synthesis, are abundant in prokaryotic and eukaryotic cells, and are highly conserved during evolution. The Hsp60 family is involved in assembly and transport of proteins, and is expressed at very high levels during autoimmunity or autoinflammatory phenomena. Here, the pathophysiological role of the wild type [WT] and the point mutated K409A recombinant Hsp65 of M. leprae in an animal model of Systemic Lupus Erythematosus [SLE] was evaluated in vivo using the genetically homogeneous [NZBxNZW]F1 mice. Anti-DNA and anti-Hsp65 antibodies responsiveness was individually measured during the animals life span, and the mean survival time [MST] was determined. The treatment with WT abbreviates the MST in 46%, when compared to non-treated mice [p<0.001]. An increase in the IgG2a/IgG1 anti-DNA antibodies ratio was also observed in animals injected with the WT Hsp65. Incubation of BALB/c macrophages with F1 serum from WT treated mice resulted in acute cell necrosis; treatment of these cells with serum from K409A treated mice did not cause any toxic effect. Moreover, the involvement of WT correlates with age and is dose-dependent. Our data suggest that Hsp65 may be a central molecule intervening in the progression of the SLE, and that the point mutated K409A recombinant immunogenic molecule, that counteracts the deleterious effect of WT, may act mitigating and delaying the development of SLE in treated mice. This study gives new insights into the general biological role of Hsp and the significant impact of environmental factors during the pathogenesis of this autoimmune process.

Analysis of the activation profile of dendritic cells derived from the bone marrow of interleukin-12/interleukin-23-deficient mice

We have previously shown that macrophages from interleukin (IL)‐12p40 gene knockout (IL‐12/IL‐23–/–) mice have a bias towards the M2 activation profile, spontaneously secreting large quantities of transforming growth factor‐β1 (TGF‐β1) and producing low levels of nitric oxide (NO) in response to lipopolysaccharide (LPS) and interferon‐γ (IFN‐γ). To verify whether the activation profile of dendritic cells (DCs) is also influenced by the absence of IL‐12/IL‐23, bone marrow‐derived DCs from IL‐12/IL‐23–/– and C57BL/6 mice were evaluated. At first we noticed that ≈ 50% of the C57BL/6 DCs were dead after LPS‐induced maturation, whereas the mortality of IL‐12/IL‐23–/– DCs was < 10%, a protective effect that diminished when recombinant IL‐12 (rIL‐12) was added during maturation. Similarly to macrophages, mature IL‐12/IL‐23–/– DCs (mDCs) produced higher levels of TGF‐β1 and lower levels of NO than C57BL/6 mDCs. NO release was IFN‐γ‐dependent, as evidenced by the poor response of IFN‐γ–/– and IL‐12/IL‐23–/–IFN‐γ–/– mDCs. Nevertheless, IFN‐γ deficiency was not the sole reason for the weak NO response observed in the absence of IL‐12/IL‐23. The high level of TGF‐β1 secretion by IL‐12/IL‐23–/– mDCs could explain why exogenous IFN‐γ partially restored the NO production of IFN‐γ–/– mDCs, while IL‐12/IL‐23–/– IFN‐γ–/– mDCs remained unresponsive. We also showed that CD4+ T‐cell proliferation was inhibited by C57BL/6 mDCs, but not by IL‐12/IL‐23–/– mDCs. IFN‐γ and NO appear to mediate this antiproliferative effect because this effect was not observed in the presence of mDCs from IFN‐γ–/– or IL‐12/IL‐23–/– IFN‐γ–/– mice and it was attenuated by aminoguanidine. We conclude that the presence of IL‐12/IL‐23 during LPS‐induced maturation influences the activation profile of DCs by a mechanism that is, only in part, IFN‐γ dependent.

Distinct placental malaria pathology caused by different Plasmodium berghei lines that fail to induce cerebral malaria in the C57BL/6 mouse

BackgroundPlacental malaria (PM) is one major feature of malaria during pregnancy. A murine model of experimental PM using BALB/c mice infected with Plasmodium berghei ANKA was recently established, but there is need for additional PM models with different parasite/host combinations that allow to interrogate the involvement of specific host genetic factors in the placental inflammatory response to Plasmodium infection.MethodsA mid-term infection protocol was used to test PM induction by three P. berghei parasite lines, derived from the K173, NK65 and ANKA strains of P. berghei that fail to induce experimental cerebral malaria (ECM) in the susceptible C57BL/6 mice. Parasitaemia course, pregnancy outcome and placenta pathology induced by the three parasite lines were compared.ResultsThe three P. berghei lines were able to evoke severe PM pathology and poor pregnancy outcome features. The results indicate that parasite components required to induce PM are distinct from ECM. Nevertheless, infection with parasites of the ANKAΔpm4 line, which lack expression of plasmepsin 4, displayed milder disease phenotypes associated with a strong innate immune response as compared to infections with NK65 and K173 parasites.ConclusionsInfection of pregnant C57BL/6 females with K173, NK65 and ANKAΔpm4 P. berghei parasites provide experimental systems to identify host molecular components involved in PM pathogenesis mechanisms.

TREM2 governs Kupffer cell activation and explains belr1 genetic resistance to malaria liver stage infection

Significance Current efforts in malaria therapeutics and vaccine development include strategies aimed at deterring infection at the liver stage, preventing subsequent clinical complications and malaria transmission. To elucidate response mechanisms operating during liver stage infection, we searched for host genetic factors that control parasite expansion in a mouse model of malaria liver stage resistance. Here we report that the cell surface receptor TREM2 is expressed in innate immune cell types residing in the liver and takes part in a mechanism enabling such cells to control the yield of hepatocyte infection. This work highlights the relevance of innate immunity mechanisms in controlling expansion of the malaria parasite in the liver. Plasmodium liver stage infection is a target of interest for the treatment of and vaccination against malaria. Here we used forward genetics to search for mechanisms underlying natural host resistance to infection and identified triggering receptor expressed on myeloid cells 2 (TREM2) and MHC class II molecules as determinants of Plasmodium berghei liver stage infection in mice. Locus belr1 confers resistance to malaria liver stage infection. The use of newly derived subcongenic mouse lines allowed to map belr1 to a 4-Mb interval on mouse chromosome 17 that contains the Trem2 gene. We show that Trem2 expression in the nonparenchymal liver cells closely correlates with resistance to liver stage infection, implicating TREM2 as a mediator of the belr1 genetic effect. Trem2-deficient mice are more susceptible to liver stage infection than their WT counterparts. We found that Kupffer cells are the principle cells expressing TREM2 in the liver, and that Trem2−/− Kupffer cells display altered functional activation on exposure to P. berghei sporozoites. TREM2 expression in Kupffer cells contributes to the limitation of parasite expansion in isolated hepatocytes in vitro, potentially explaining the increased susceptibility of Trem2−/− mice to liver stage infection. The MHC locus was also found to control liver parasite burden, possibly owing to the expression of MHC class II molecules in hepatocytes. Our findings implicate unexpected Kupffer–hepatocyte cross-talk in the control Plasmodium liver stage infection and demonstrate that TREM2 is involved in host responses against the malaria parasite.

Administration of Mycobacterium leprae rHsp65 Aggravates Experimental Autoimmune Uveitis in Mice

The 60kDa heat shock protein family, Hsp60, constitutes an abundant and highly conserved class of molecules that are highly expressed in chronic-inflammatory and autoimmune processes. Experimental autoimmune uveitis [EAU] is a T cell mediated intraocular inflammatory disease that resembles human uveitis. Mycobacterial and homologous Hsp60 peptides induces uveitis in rats, however their participation in aggravating the disease is poorly known. We here evaluate the effects of the Mycobacterium leprae Hsp65 in the development/progression of EAU and the autoimmune response against the eye through the induction of the endogenous disequilibrium by enhancing the entropy of the immunobiological system with the addition of homologous Hsp. B10.RIII mice were immunized subcutaneously with interphotoreceptor retinoid-binding protein [IRBP], followed by intraperitoneally inoculation of M. leprae recombinant Hsp65 [rHsp65]. We evaluated the proliferative response, cytokine production and the percentage of CD4+IL-17+, CD4+IFN-γ+ and CD4+Foxp3+ cells ex vivo, by flow cytometry. Disease severity was determined by eye histological examination and serum levels of anti-IRBP and anti-Hsp60/65 measured by ELISA. EAU scores increased in the Hsp65 group and were associated with an expansion of CD4+IFN-γ+ and CD4+IL-17+ T cells, corroborating with higher levels of IFN-γ. Our data indicate that rHsp65 is one of the managers with a significant impact over the immune response during autoimmunity, skewing it to a pathogenic state, promoting both Th1 and Th17 commitment. It seems comprehensible that the specificity and primary function of Hsp60 molecules can be considered as a potential pathogenic factor acting as a whistleblower announcing chronic-inflammatory diseases progression.

Supplementation of CXCL12 (CXCL12) induces homing of CD11c+ dendritic cells to the spleen and enhances control of Plasmodium berghei malaria in BALB/c mice

In malaria, parasitaemia is controlled in the spleen, a multicomponent organ that undergoes changes in its cellular constituents to control the parasite. During this process, dendritic cells (DCs) orchestrate the positioning of effector cells in a timely manner for optimal parasite clearance. We have recently demonstrated that CXCL12 [stromal cell‐derived factor‐1 (CXCL12)] supplementation partially restores the ability to control parasitaemia in Plasmodium berghei‐infected mice. In the present study, we investigated the nature of the DCs involved by flow cytometry and immunohistochemistry of CD11c+ cells. Flow cytometry of bone marrow cells showed that infection with P. berghei did not alter the proportion of CD11c+ cells present in this haematopoietic compartment, while CXCL12 supplementation of naïve uninfected mice induced only minor increases in the population of CD11c+ cells. In the spleen, P. berghei infection alone resulted in an increase in CD11c+ cells as compared with naïve animals. Exogenously administered CXCL12 in the absence of infection resulted in a significant expansion of the splenic CD11c+ population, and this effect was even more pronounced in infected and supplemented mice. Immunohistochemistry revealed that CD11c+ cells infiltrated the perivascular areas and marginal zone of the spleen in infected animals treated with CXCL12, suggesting that this chemokine induces homing of CD11c+ dendritic cells to the splenic compartment. Our results show that small amounts of CXCL12 supplementation are effective in recruiting DCs to the spleens of both uninfected and infected mice, suggesting the participation of CXCL12 and CD11c+ cells in the establishment of an adequate environment in the spleen for malaria control.

Iron overload in Plasmodium berghei-infected placenta as a pathogenesis mechanism of fetal death.

Plasmodium infection during gestation may lead to severe clinical manifestations including abortion, stillbirth, intrauterine growth retardation, and low birth weight. Mechanisms underlying such poor pregnancy outcomes are still unclear. In the animal model of severe placental malaria (PM), in utero fetal death frequently occurs and mothers often succumb to infection before or immediately after delivery. Plasmodium berghei-infected erythrocytes (IEs) continuously accumulate in the placenta, where they are then phagocytosed by fetal-derived placental cells, namely trophoblasts. Inside the phagosomes, disruption of IEs leads to the release of non-hemoglobin bound heme, which is subsequently catabolized by heme oxygenase-1 into carbon monoxide, biliverdin, and labile iron. Fine-tuned regulatory mechanisms operate to maintain iron homeostasis, preventing the deleterious effect of iron-induced oxidative stress. Our preliminary results demonstrate that iron overload in trophoblasts of P. berghei-infected placenta is associated with fetal death. Placentas which supported normally developing embryos showed no iron accumulation within the trophoblasts. Placentas from dead fetuses showed massive iron accumulation, which was associated with parasitic burden. Here we present preliminary data suggesting that disruption of iron homeostasis in trophoblasts during the course of PM is a consequence of heme accumulation after intense IE engulfment. We propose that iron overload in placenta is a pathogenic component of PM, contributing to fetal death. The mechanism through which it operates still needs to be elucidated.