Transforming growth factor-β induces microRNA-29b to promote murine alveolar macrophage dysfunction after bone marrow transplantation

Extracellular vesicles secreted by equine adipose mesenchymal stem cells preconditioned with transforming growth factor β-1 are enriched in anti-fibrotic miRNAs and inhibit the expression of fibrotic genes in an in vitro system of endometrial stromal cells fibrosis

Mare endometrosis is a major reproductive problem associated with low fertility and is characterized by persistent inflammation, TGFβ-1 signaling, and consequently, extracellular matrix deposition, which compromises endometrial glands. Mesenchymal stem cell-based products (MSCs), such as extracellular vesicles (EVs), have gained attention due to the regulatory effects exerted by their miRNA cargo. Here, we evaluated the impact of preconditioning equine adipose mesenchymal stem cells with TGFβ-1 for short or long periods on the anti-fibrotic properties of secreted extracellular vesicles. MSCs were isolated from six healthy horses and exposed to TGFβ-1 for 4, 24, and 0 h. The expression of anti-fibrotic and pro-fibrotic miRNAs and mRNAs in treated cells and miRNAs in the cargo of secreted extracellular vesicles was measured. The resulting EVs were added for 48 h to endometrial stromal cells previously induced to a fibrotic status. The expression of anti-fibrotic and pro-fibrotic genes and miRNAs was evaluated in said cells using qPCR and next-generation sequencing. Preconditioning MSCs with TGFβ-1 for 4 h enriched the anti-fibrotic miRNAs (mir29c, mir145, and mir200) in cells and EVs. Conversely, preconditioning the cells for 24 h leads to a pro-fibrotic phenotype overexpressing mir192 and mir433. This finding might have implications for developing an EV-based protocol to treat endometrial fibrosis in mares.

Dysbiosis and diabetic foot ulcers: A metabolic perspective of Staphylococcus aureus infection

Staphylococcus aureus (S. aureus) infection is the most prevalent and resistant bacterial infection, posing a worldwide health risk. Compared with healthy people, diabetes patients with weak immune function and abnormal metabolism are more vulnerable to bacterial infection, which aggravates the intensity of infection and causes a series of common and dangerous complications, such as diabetes foot ulcer (DFU). Due to metabolic abnormalities of diabetic patients, S. aureus on the skin surface of DFU transitions from a commensal to an invasive infection. During this process, S. aureus resists a series of unfavorable conditions for bacterial growth by altering energy utilization and metabolic patterns, and secretes various virulence factors, causing persistent infection. With the emergence of multiple super-resistant bacteria, antibiotic treatment is no longer the only treatment option, and developing new drugs and therapies is urgent. Regulating the metabolic signaling pathway of S. aureus plays a decisive role in regulating its virulence factors and impacts adjuvant therapy for DFU. This article focuses on studying the impact of regulating metabolic signals on the virulence of S. aureus from a metabolism perspective. It provides an outlook on the future direction of the novel development of antimicrobial therapy.

Wounds under diabetic milieu: The role of immune cellar components and signaling pathways

A major challenge in the field of diabetic wound healing is to confirm the body's intrinsic mechanism that could sense the immune system damage promptly and protect the wound from non-healing. Accumulating literature indicates that macrophage, a contributor to prolonged inflammation occurring at the wound site, might play such a role in hindering wound healing. Likewise, other immune cell dysfunctions, such as persistent neutrophils and T cell infection, may also lead to persistent oxidative stress and inflammatory reaction during diabetic wound healing. In this article, we discuss recent advances in the immune cellular components in wounds under the diabetic milieu, and the role of key signaling mechanisms that compromise the function of immune cells leading to persistent wound non-healing.

Bidirectional cytokine-microRNA control: A novel immunoregulatory framework in leishmaniasis

As effector innate immune cells and as a host to the protozoan parasite Leishmania, macrophages play a dual role in antileishmanial immunoregulation. The 2 key players in this immunoregulation are the macrophage-expressed microRNAs (miRNAs) and the macrophage-secreted cytokines. miRNAs, as small noncoding RNAs, play vital roles in macrophage functions including cytokines and chemokines production. In the reverse direction, Leishmania-regulated cytokines alter miRNAs expression to regulate the antileishmanial functions of macrophages. The miRNA patterns vary with the time and stage of infection. The cytokine-regulated macrophage miRNAs not only help parasite elimination or persistence but also regulate cytokine production from macrophages. Based on these observations, we propose a novel immunoregulatory framework as a scientific rationale for antileishmanial therapy.

Experimental Models of Infectious Pulmonary Complications Following Hematopoietic Cell Transplantation

Pulmonary infections remain a major cause of morbidity and mortality in hematopoietic cell transplantation (HCT) recipients. The prevalence and type of infection changes over time and is influenced by the course of immune reconstitution post-transplant. The interaction between pathogens and host immune responses is complex in HCT settings, since the conditioning regimens create periods of neutropenia and immunosuppressive drugs are often needed to prevent graft rejection and limit graft-versus-host disease (GVHD). Experimental murine models of transplantation are valuable tools for dissecting the procedure-related alterations to innate and adaptive immunity. Here we review mouse models of post-HCT infectious pulmonary complications, primarily focused on three groups of pathogens that frequently infect HCT recipients: bacteria (often P. aeruginosa), fungus (primarily Aspergillus fumigatus), and viruses (primarily herpesviruses). These mouse models have advanced our knowledge regarding how the conditioning and HCT process negatively impacts innate immunity and have provided new potential strategies of managing the infections. Studies using mouse models have also validated clinical observations suggesting that prior or occult infections are a potential etiology of noninfectious pulmonary complications post-HCT as well.

A Comprehensive miRNome Analysis of Macrophages Isolated from db/db Mice and Selected miRNAs Involved in Metabolic Syndrome-Associated Cardiac Remodeling

Cardiac macrophages are known from various activities, therefore we presume that microRNAs (miRNAs) produced or released by macrophages in cardiac tissue have impact on myocardial remodeling in individuals with metabolic syndrome (MetS). We aim to assess the cardiac macrophage miRNA profile by selecting those miRNA molecules that potentially exhibit regulatory functions in MetS-related cardiac remodeling. Cardiac tissue macrophages from control and db/db mice (an animal model of MetS) were counted and sorted with flow cytometry, which yielded two populations: CD45+CD11b+CD64+Ly6Chi and CD45+CD11b+CD64+Ly6Clow. Total RNA was then isolated, and miRNA expression profiles were evaluated with Next Generation Sequencing. We successfully sequenced 1400 miRNAs in both macrophage populations: CD45+CD11b+CD64+Ly6Chi and CD45+CD11b+CD64+Ly6Clow. Among the 1400 miRNAs, about 150 showed different expression levels in control and db/db mice and between these two subpopulations. At least 15 miRNAs are possibly associated with MetS pathology in cardiac tissue due to direct or indirect regulation of the expression of miRNAs for proteins involved in angiogenesis, fibrosis, or inflammation. In this paper, for the first time we describe the miRNA transcription profile in two distinct macrophage populations in MetS-affected cardiac tissue. Although the results are preliminary, the presented data provide a foundation for further studies on intercellular cross-talk/molecular mechanism(s) involved in the regulation of MetS-related cardiac remodeling.

Bone Marrow Mesenchymal Stem Cell-Derived Small Extracellular Vesicles Promote Periodontal Regeneration

Bone marrow mesenchymal stem cell-derived small extracellular vesicles (BMSC-sEVs) can be used as a potential cell-free strategy for periodontal tissue regeneration, and we aim to investigate the effect and possible mechanism of BMSC-sEV in periodontal tissue regeneration in this study. The BMSC-sEV was isolated by the Exosome Isolation™ reagent and identified by transmission electron microscopy, nanoparticle tracking analysis, and Western blotting. The human periodontal ligament cells (hPDLCs) were cocultured with BMSC-sEV in vitro to detect the effects of BMSC-sEV on hPDLC migration, proliferation, and differentiation. The BMSC-sEV loaded by hydrogel was injected into experimental periodontitis rats to verify the therapeutic effect and possible mechanism. The results showed that BMSC-sEVs were 30-150 nm vesicles and expressed the exosome protein CD63 and tumor susceptibility 101 (TSG101), which could promote the migration, proliferation, osteogenic differentiation of hPDLCs. The BMSC-sEV-hydrogel had a therapeutic effect on periodontitis rats. After administration for 4-8 weeks, microcomputed tomography and histological analysis showed that alveolar bone loss, inflammatory infiltration, and collagen destruction in the BMSC-sEV-hydrogel group were less than that in the phosphate-buffered saline (PBS)-hydrogel group and periodontitis group. Further immunohistochemical and immunofluorescent staining revealed that the number of tartrate-resistant acid phosphatase-positive cells and the expression ratio of osteoprotegerin (OPG) and receptor-activator of nuclear factor kappa beta ligand (RANKL) in the BMSC-sEV-hydrogel group were lower than that in the PBS-hydrogel group and periodontitis group, while the expression of transforming growth factor-beta 1 (TGF-β1) and the ratio of macrophage type 2 and macrophage type 1 (M2/M1) were opposite. Therefore, BMSC-sEV can promote the regeneration of periodontal tissues, and that may be partly due to BMSC-sEV involvement in the OPG-RANKL-RANK signaling pathway to regulate the function of osteoclasts and affect the macrophage polarization and TGF-β1 expression to modulate the inflammatory immune response, thereby inhibiting the development of periodontitis and immune damage of periodontal tissue. Impact statement Bone marrow mesenchymal stem cell-derived small extracellular vesicles (BMSCs-sEVs) have been proven to have similar functions to BMSCs, such as promoting the regeneration of heart, liver, kidney, and bone tissue and regulating immune responses. BMSCs are candidate seed cells of periodontal regeneration, but it is unclear about the role of BMSC-sEV on periodontal regeneration. In this study, we explored the effects and possible mechanism of BMSC-sEV on periodontal regeneration. The results of this study provide the evidence of BMSC-sEV as a cell-free strategy for periodontal regeneration.

Mesenchymal stem cells negatively regulate CD4⁺ T cell activation in patients with primary Sjögren syndrome through the miRNA‑125b and miRNA‑155 TCR pathway

Treatment with mesenchymal stem cells (MSCs) has been revealed to suppress CD4⁺ T cells and autoimmunity in both mouse models and patients with primary Sjögren syndrome (pSS); however, the underlying mechanism remains unclear. MicroRNAs (miRNAs or miRs) mediate CD4⁺ T cell activation, but the mechanism is not understood, particularly for CD4⁺ T cells treated with MSCs. Characterization of miRNAs may reveal pSS pathogenesis, guide MSC treatment and provide more personalized management options. The present study aimed to perform an miRNome analysis of quiescent and T cell receptor (TCR)‑activated CD4⁺ T cells treated with MSCs via miRNA profiles and bioinformatics. Following 72 h of co‑culture, MSCs inhibited TCR‑induced CD4⁺ T cell activation and decreased IFN‑γ levels. The numbers of aberrant miRNAs in pSS naïve (vs. healthy naïve), pSS activation (vs. pSS naïve), MSC treatment and pre‑IFN‑γ MSC treatment (vs. pSS activation) groups were 42, 55, 27 and 32, respectively. Gene enrichment analysis revealed that 259 pathways were associated with CD4⁺ T cell stimulation, and 240 pathways were associated with MSC treatment. Increased miRNA‑7150 and miRNA‑5096 and decreased miRNA‑125b‑5p and miRNA‑22‑3p levels in activated CD4⁺ T cells from patients with pSS were reversed by MSC treatment. Notably, the proliferation of CD4⁺ T cells and CD4⁺ IFN‑γ⁺ cells, expression levels of miRNA‑125b‑5p and miRNA‑155 in CD4⁺ T cells and supernatant IFN‑γ secretion were associated with disease activity. miRNA may play a vital role in MSC treatment for activated CD4⁺ T cells. The results indicated that the expression levels of miRNA‑125b‑5p and miRNA‑155 in TCR‑activated CD4⁺ T cells from patients with pSS may provide insight regarding autoimmune diseases and offer a novel target for prospective treatment. Therefore, these results may be crucial in providing MSC treatment for pSS.

Epigenetic regulation of the PGE2 pathway modulates macrophage phenotype in normal and pathologic wound repair

Macrophages are a primary immune cell involved in inflammation, and their cell plasticity allows for transition from an inflammatory to a reparative phenotype and is critical for normal tissue repair following injury. Evidence suggests that epigenetic alterations play a critical role in establishing macrophage phenotype and function during normal and pathologic wound repair. Here, we find in human and murine wound macrophages that cyclooxygenase 2/prostaglandin E2 (COX-2/PGE2) is elevated in diabetes and regulates downstream macrophage-mediated inflammation and host defense. Using single-cell RNA sequencing of human wound tissue, we identify increased NF-κB-mediated inflammation in diabetic wounds and show increased COX-2/PGE2 in diabetic macrophages. Further, we identify that COX-2/PGE2 production in wound macrophages requires epigenetic regulation of 2 key enzymes in the cytosolic phospholipase A2/COX-2/PGE2 (cPLA2/COX-2/PGE2) pathway. We demonstrate that TGF-β-induced miRNA29b increases COX-2/PGE2 production via inhibition of DNA methyltransferase 3b-mediated hypermethylation of the Cox-2 promoter. Further, we find mixed-lineage leukemia 1 (MLL1) upregulates cPLA2 expression and drives COX-2/PGE2. Inhibition of the COX-2/PGE2 pathway genetically (Cox2fl/fl Lyz2Cre+) or with a macrophage-specific nanotherapy targeting COX-2 in tissue macrophages reverses the inflammatory macrophage phenotype and improves diabetic tissue repair. Our results indicate the epigenetically regulated PGE2 pathway controls wound macrophage function, and cell-targeted manipulation of this pathway is feasible to improve diabetic wound repair.

miRNAs reshape immunity and inflammatory responses in bacterial infection

Pathogenic bacteria cause various infections worldwide, especially in immunocompromised and other susceptible individuals, and are also associated with high infant mortality rates in developing countries. MicroRNAs (miRNAs), small non-coding RNAs with evolutionarily conserved sequences, are expressed in various tissues and cells that play key part in various physiological and pathologic processes. Increasing evidence implies roles for miRNAs in bacterial infectious diseases by modulating inflammatory responses, cell penetration, tissue remodeling, and innate and adaptive immunity. This review highlights some recent intriguing findings, ranging from the correlation between aberrant expression of miRNAs with bacterial infection progression to their profound impact on host immune responses. Harnessing of dysregulated miRNAs in bacterial infection may be an approach to improving the diagnosis, prevention and therapy of infectious diseases.

Changes in production of tiny cellular RNAs in response to bacterial infection could guide the development of better diagnostics and therapies. MicroRNAs regulate other genes by binding to messenger RNA strands and controlling their translation into proteins. Xikun Zhou, Min Wu and colleagues of the University of North Dakota have now reviewed current knowledge about how microRNA levels shift during infection with various bacterial pathogens. These microRNAs can modulate the immune response as well as pathways that influence metabolic activity and cell survival. Increasing studies have indicated that shifts in microRNA levels in response to different infections could provide a potential bacterial ‘fingerprint’ for achieving accurate diagnosis. With deeper insight into how different microRNAs influence infection, it might one day day become possible to target these molecules with ‘antisense’ or ‘agonist’ drugs that modulate their activity.

Prostaglandin E2 as a Regulator of Immunity to Pathogens

The body is exposed to foreign pathogens every day, but remarkably, most pathogens are effectively cleared by the innate immune system without the need to invoke the adaptive immune response. Key cellular components of the innate immune system include macrophages and neutrophils and the recruitment and function of these cells are tightly regulated by chemokines and cytokines in the tissue space. Innate immune responses are also known to regulate development of adaptive immune responses often via the secretion of various cytokines. In addition to these protein regulators, numerous lipid mediators can also influence innate and adaptive immune functions. In this review, we cover one particular lipid regulator, prostaglandin E2 (PGE2) and describe its synthesis and signaling and what is known about the ability of this lipid to regulate immunity and host defense against viral, fungal and bacterial pathogens.

Bone marrow transplant-induced alterations in Notch signaling promote pathologic Th17 responses to γ-herpesvirus infection

Idiopathic pneumonia syndrome (IPS) is a common, often fatal, complication following hematopoietic stem cell transplantation (HSCT) characterized by severe pneumonitis and interstitial fibrosis. Fully reconstituted syngeneic bone marrow transplant (BMT) mice infected with murine γ-herpesvirus-68 develop interleukin-17 (IL-17)-driven pneumonitis and fibrosis, which mimics clinical manifestations of IPS. We found CD103+ and CD11b+ dendritic cells (DCs) are selectively deficient for the Notch ligand, DLL4, following BMT and CD4+ T cells isolated from lungs and spleens of infected BMT mice display Notch signaling defects. Mice transplanted with CD4-Cre-driven dominant-negative Notch transcriptional regulator Mastermind-Like (CD4-Cre-DNMAML (CCD) mice) bone marrow displayed elevated IL-17 and transforming growth factor-β (TGF β) in the lungs, a further expansion of T-helper type 17 (Th17) cells, and developed more fibrosis than wild-type (WT)-BMT mice. Culture of BMT lung leukocytes with recombinant Notch ligand, DLL4, restored Notch signaling and decreased production of IL-17. Adoptive transfer of CD11c+ DCs could restore Th1 and limit Th17 in WT-BMT but not CCD-BMT mice, indicating that a specific DC/CD4+ T-cell Notch interaction modulates IL-17 production following reconstitution in syngeneic BMT mice. Given recent clinical observations showing that patients with pulmonary complications post-transplant harbor occult herpesvirus infections, these data provide mechanistic insight and suggest potential therapies for these devastating conditions.

Elevated prostaglandin E2 post-bone marrow transplant mediates interleukin-1β-related lung injury

Hematopoietic stem cell transplant (HSCT) treats or cures a variety of hematological and inherited disorders. Unfortunately, patients who undergo HSCT are susceptible to infections by a wide array of opportunistic pathogens. Pseudomonas aeruginosa bacteria can have life-threatening effects in HSCT patients by causing lung pathology that has been linked to high levels of the potent pro-inflammatory cytokine, interleukin-1β (IL-1β). Using a murine bone marrow transplant (BMT) model, we show that overexpression of prostaglandin E₂ (PGE₂) post-BMT signals via EP2 or EP4 to induce cyclic adenosine monophosphate (cAMP), which activates protein kinase A or the exchange protein activated by cAMP (Epac) to induce cAMP response element binding-dependent transcription of IL-1β leading to exacerbated lung injury in BMT mice. Induction of IL-1β by PGE₂ is time and dose dependent. Interestingly, IL-1β processing post-P. aeruginosa infection occurs via the enzymatic activity of either caspase-1 or caspase-8. Furthermore, PGE₂ can limit autophagy-mediated killing of P. aeruginosa in alveolar macrophages, yet autophagy does not have a role in PGE₂-mediated upregulation of IL-1β. Reducing PGE₂ levels with indomethacin improved bacterial clearance and reduced IL-1β-mediated acute lung injury in P. aeruginosa-infected BMT mice.

MicroRNA: Dynamic Regulators of Macrophage Polarization and Plasticity

The ability of a healthy immune system to clear the plethora of antigens it encounters incessantly relies on the enormous plasticity displayed by the comprising cell types. Macrophages (MΦs) are crucial member of the mononuclear phagocyte system (MPS) that constantly patrol the peripheral tissues and are actively recruited to the sites of injury and infection. In tissues, infiltrating monocytes replenish MΦ. Under the guidance of the local micro-milieu, MΦ can be activated to acquire specialized functional phenotypes. Similar to T cells, functional polarization of macrophage phenotype viz., inflammatory (M1) and reparative (M2) is proposed. Equipped with diverse toll-like receptors (TLRs), these cells of the innate arm of immunity recognize and phagocytize antigens and secrete cytokines that activate the adaptive arm of the immune system and perform key roles in wound repair. Dysregulation of MΦ plasticity has been associated with various diseases and infection. MicroRNAs (miRNAs) have emerged as critical regulators of transcriptome output. Their importance in maintaining health, and their contribution toward disease, encompasses virtually all aspects of human biology. Our understanding of miRNA-mediated regulation of MΦ plasticity and polarization can be utilized to modulate functional phenotypes to counter their role in the pathogenesis of numerous disease, including cancer, autoimmunity, periodontitis, etc. Here, we provide an overview of current knowledge regarding the role of miRNA in shaping MΦ polarization and plasticity through targeting of various pathways and genes. Identification of miRNA biomarkers of diagnostic/prognostic value and their therapeutic potential by delivery of miRNA mimics or inhibitors to dynamically alter gene expression profiles in vivo is highlighted.

Alveolar-like Stem Cell-derived Myb(-) Macrophages Promote Recovery and Survival in Airway Disease

RATIONALE

Abnormal alveolar macrophages (AM) are found in chronic obstructive pulmonary disease, asthma, cystic fibrosis, and adenosine deaminase deficiency (ADA(-/-)). There is no specific treatment strategy to compensate for these innate immune abnormalities. Recent findings suggest AMs are of early embryonic or fetal origin. Pluripotent stem cells (PSCs) as a source of embryonic-derived AMs for therapeutic use in acute and chronic airway diseases has yet to be investigated.

OBJECTIVES

To determine if embryonic Myb(-/-) alveolar-like macrophages have therapeutic value on pulmonary transplantation in acute and chronic airway diseases.

METHODS

Directed differentiation of murine PSCs was used in factor-defined media to produce expandable embryonic macrophages conditioned to an alveolar-like phenotype with granulocyte-macrophage colony-stimulating factor. AMs were partially depleted in mice to create an acute lung injury. To model a chronic lung disease, ADA(-/-) mice were used. Alveolar-like macrophages were intratracheally transplanted to the injured animals and therapeutic potential was determined.

MEASUREMENTS AND MAIN RESULTS

The differentiation protocol is highly efficient and adaptable to human PSCs. The PSC macrophages are phenotypically like AMs both functionally and by ligand marker characterization. They engulf bacteria and apoptotic cells and are better phagocytes than bone marrow-derived macrophages. In vivo, these macrophages remain in healthy airways for at least 4 weeks, can engulf neutrophils during acute lung injury, enhance pulmonary tissue repair, and promote survival in ADA(-/-) mice. Animals receiving the macrophages do not develop abnormal pathology or teratomas.

CONCLUSIONS

PSCs are a reliable source to produce therapeutically active alveolar-like macrophages to treat airway disease.

Emerging concepts in smooth muscle contributions to airway structure and function: implications for health and disease

Airway structure and function are key aspects of normal lung development, growth, and aging, as well as of lung responses to the environment and the pathophysiology of important diseases such as asthma, chronic obstructive pulmonary disease, and fibrosis. In this regard, the contributions of airway smooth muscle (ASM) are both functional, in the context of airway contractility and relaxation, as well as synthetic, involving production and modulation of extracellular components, modulation of the local immune environment, cellular contribution to airway structure, and, finally, interactions with other airway cell types such as epithelium, fibroblasts, and nerves. These ASM contributions are now found to be critical in airway hyperresponsiveness and remodeling that occur in lung diseases. This review emphasizes established and recent discoveries that underline the central role of ASM and sets the stage for future research toward understanding how ASM plays a central role by being both upstream and downstream in the many interactive processes that determine airway structure and function in health and disease.

Transforming Growth Factor-β1 Increases DNA Methyltransferase 1 and 3a Expression through Distinct Post-transcriptional Mechanisms in Lung Fibroblasts

DNA methylation is a fundamental epigenetic mark that plays a critical role in differentiation and is mediated by the actions of DNA methyltransferases (DNMTs). TGF-β1 is one of the most potent inducers of fibroblast differentiation, and although many of its actions on fibroblasts are well described, the ability of TGF-β1 to modulate DNA methylation in mesenchymal cells is less clear. Here, we examine the ability of TGF-β1 to modulate the expression of various DNMTs in primary lung fibroblasts (CCL210). TGF-β1 increased the protein expression, but not RNA levels, of both DNMT1 and DNMT3a. The increases in DNMT1 and DNMT3a were dependent on TGF-β1 activation of focal adhesion kinase and PI3K/Akt. Activation of mammalian target of rapamycin complex 1 by Akt resulted in increased protein translation of DNMT3a. In contrast, the increase in DNMT1 by TGF-β1 was not dependent on new protein synthesis and instead was due to decreased protein degradation. TGF-β1 treatment led to the phosphorylation and inactivation of glycogen synthase kinase-3β, which resulted in inhibition of DNMT1 ubiquitination and proteosomal degradation. The phosphorylation and inactivation of glycogen synthase kinase-3β was dependent on mammalian target of rapamycin complex 1. These results demonstrate that TGF-β1 increases expression of DNMT1 and DNMT3a through different post-transcriptional mechanisms. Because DNA methylation is critical to many processes including development and differentiation, for which TGF-β1 is known to be crucial, the ability of TGF-β1 to increase expression of both DNMT1 and DNMT3a demonstrates a novel means by which TGF-β1 may regulate DNA methylation in these cells.