Project description:Induction of the inhibitory Smad, Smad7 serves as a negative feedback mechanism that restrains TGF-b-mediated actions in injured tissues. In inflammatory cells, Smad7 has been suggested to exert both pro-inflammatory actions attributed to inhibition of TGF-b-induced suppression of inflammation, and anti-inflammatory effects due to disruption of the TAK-1/NF-kB system. Myocardial infarction triggers a macrophage-driven inflammatory response that plays a central role in cardiac repair, but also contributes to adverse remodeling and fibrosis. We hypothesized that Smad7 upregulation in infarct macrophages may play a modulatory role in cardiac repair, by restraining effects of TGF-b. To test the hypothesis, we investigated the response of Myeloid cell-specific Smad7 knockout mice (MyS7KO) following myocardial infarction protocols, and we examined the in vitro effects of Smad7 in isolated macrophages. Smad7 was upregulated in a subset of infarct macrophages, peaking 7 days after infarction. Myeloid cell-specific Smad7 loss did not affect baseline macrophage gene expression and had no significant effects on homeostatic functions. Although RNA-seq analysis predicted that, in the absence of Smad7, infarct macrophages may have attenuated activation of inflammatory pathways and suppressed TREM1 signaling, myeloid cell-specific Smad7 loss had no significant effects on ventricular dysfunction, adverse remodeling, scar remodeling and collagen deposition after myocardial infarction. In isolated macrophages, TGF-b attenuated pro-inflammatory cytokine and chemokine expression, modulated synthesis of matrix remodeling genes, and had profound effects on macrophage profile, inducing genes associated with activation of sphingosine-1 phosphate and integrin signaling pathways, and inhibiting cholesterol biosynthesis genes. However, RNA-seq and PCR array experiments showed that Smad7 loss has minimal effects on TGF-b-mediated macrophage responses, restraining synthesis of only a small fraction of TGF-b-induced genes, such as Itga5, Olfml3 and Fabp7. Smad7 absence did not affect the anti-inflammatory actions of TGF-b in TNF-stimulated cells. In conclusion, our findings suggest a limited role for macrophage Smad7 in regulation of post-infarction inflammation and repair, and demonstrate that the anti-inflammatory effects of TGF-b in macrophages are not restrained by endogenous Smad7 induction.

Project description:Rationale: Expansion and activation of cardiac fibroblasts contributes to adverse remodeling, fibrosis and dysfunction in the pressure-overloaded heart. Although early fibroblast TGF-β/Smad3 activation protects the pressure overloaded heart by preserving the matrix, sustained TGF-β activation may be deleterious, accentuating fibrosis and dysfunction. Thus, endogenous mechanisms that negatively regulate the TGF- response in fibroblasts may be required to protect from progressive fibrosis and adverse remodeling. Objective: To study the role of fibroblast-specific induction of Smad7, an inhibitory Smad that restrains TGF-β signaling, in regulation of fibrosis, remodeling and dysfunction of the pressure-overloaded heart. Methods and Results: In a mouse model of pressure overload induced through transverse aortic constriction (TAC), Smad7 was upregulated in cardiac myofibroblasts. Mice with myofibroblast-specific loss of Smad7 (MFS7KO) had increased mortality, accentuated systolic dysfunction and dilative remodeling, and accelerated diastolic dysfunction in response to TAC. Increased dysfunction in MFS7KO hearts was associated with accentuated fibrosis and increased collagen denaturation, in the absence of effects on cardiomyocyte death. Secretomic analysis showed that Smad7 loss accentuates secretion of structural collagens and matricellular proteins, and markedly increases secretion of matrix metalloproteinase-2 (MMP2). In a 3D model of fibroblasts populating collagen lattices the effects of Smad7 on fibroblast-induced collagen denaturation and pad contraction were partly mediated via MMP2 downregulation. Surprisingly, MFS7KO mice also exhibited significant macrophage expansion caused by paracrine actions of Smad7 null fibroblasts that stimulate macrophage proliferation and fibrogenic activation. Secretomic analysis and in vitro experiments suggested that macrophage activation involves the combined effects of the fibroblast-derived matricellular proteins CD5L, SPARC, CTGF, ECM1 and TGFBI. Conclusions: The anti-fibrotic effects of Smad7 in the pressure-overloaded heart protect from dysfunction and involve not only reduction in collagen deposition, but also suppression of MMP2-mediated matrix denaturation and paracrine effects that suppress macrophage activation through inhibition of matricellular proteins.

Project description:Rationale: Expansion and activation of cardiac fibroblasts contributes to adverse remodeling, fibrosis and dysfunction in the pressure-overloaded heart. Although early fibroblast TGF-β/Smad3 activation protects the pressure overloaded heart by preserving the matrix, sustained TGF-β activation may be deleterious, accentuating fibrosis and dysfunction. Thus, endogenous mechanisms that negatively regulate the TGF- response in fibroblasts may be required to protect from progressive fibrosis and adverse remodeling. Objective: To study the role of fibroblast-specific induction of Smad7, an inhibitory Smad that restrains TGF-β signaling, in regulation of fibrosis, remodeling and dysfunction of the pressure-overloaded heart. Methods and Results: In a mouse model of pressure overload induced through transverse aortic constriction (TAC), Smad7 was upregulated in cardiac fibroblasts and myofibroblasts. Mice with myofibroblast-specific loss of Smad7 (MFS7KO) had increased mortality, accentuated systolic dysfunction and dilative remodeling, and accelerated diastolic dysfunction in response to TAC. Increased dysfunction in MFS7KO hearts was associated with accentuated fibrosis and increased collagen denaturation, in the absence of effects on cardiomyocyte death. Secretomic analysis showed that Smad7 loss accentuates secretion of structural collagens and matricellular proteins, and markedly increases secretion of matrix metalloproteinase-2 (MMP2). In a 3D model of fibroblasts populating collagen lattices the effects of Smad7 on fibroblast-induced collagen denaturation and pad contraction were partly mediated via MMP2 downregulation. Surprisingly, MFS7KO mice also exhibited significant macrophage expansion caused by paracrine actions of Smad7 null fibroblasts that stimulate macrophage proliferation and fibrogenic activation. Secretomic analysis and in vitro experiments suggested that macrophage activation involves the combined effects of the fibroblast-derived matricellular proteins CD5L, SPARC, CTGF, ECM1 and TGFBI. Conclusions: The anti-fibrotic effects of Smad7 in the pressure-overloaded heart protect from dysfunction and involve not only reduction in collagen deposition, but also suppression of MMP2-mediated matrix denaturation and paracrine effects that suppress macrophage activation through inhibition of matricellular proteins.

Project description:The inflammatory response after spinal cord injury (SCI) is an important contributor to secondary damage. Infiltrating macrophages can acquire a spectrum of activation states, however, the microenvironment at the SCI site favors macrophage polarization into a pro-inflammatory phenotype, which is one of the reasons why macrophage transplantation has failed. In this study, we investigated the therapeutic potential of the macrophage secretome for SCI recovery. We investigated the effect of the secretome in vitro using peripheral and CNS-derived neurons and human neural stem cells. Moreover, we perform a pre-clinical trial using a SCI compression mice model and analyzed the recovery of motor, sensory and autonomic functions. Instead of transplanting the cells, we injected the paracrine factors and extracellular vesicles that they secrete, avoiding the loss of the phenotype of the transplanted cells due to local environmental cues. We demonstrated that different macrophage phenotypes have a distinct effect on neuronal growth and survival, namely, the alternative activation with IL-10 and TGF-β1 (M(IL-10+TGF-β1)) promotes significant axonal regeneration. We also observed that systemic injection of soluble factors and extracellular vesicles derived from M(IL-10+TGF-β1) macrophages promotes significant functional recovery after compressive SCI and leads to higher survival of spinal cord neurons. Additionally, the M(IL-10+TGF-β1) secretome supported the recovery of bladder function and decreased microglial activation, astrogliosis and fibrotic scar in the spinal cord. Proteomic analysis of the M(IL-10+TGF-β1)-derived secretome identified clusters of proteins involved in axon extension, dendritic spine maintenance, cell polarity establishment, and regulation of astrocytic activation. Overall, our results demonstrated that macrophages-derived soluble factors and extracellular vesicles might be a promising therapy for SCI with possible clinical applications.

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Macrophage Smad1 contributes to post-infarction dysfunction, suppressing angiogenic chemokine expression, and stimulating extracellular matrix remodeling

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