Activin Pathway Research Articles

Abstract Tu053: Activin Signaling Inhibition Enhances Cardiac Functional Recovery After Aortic Debanding

Background: Human aortic stenosis (AS) induces adverse cardiac remodeling and heart failure by pressure overload. Reducing pressure overload (e.g., Trans-catheter aortic valve replacement (TAVR) mitigates or reverses adverse remodeling but these benefits are limited in many TAVR patients. Here we established a murine transverse-aortic-constriction (TAC)-debanding model to mimic TAVR and identify ways to enhance reverse remodeling. Methods: 10-week-old wild-type C57BL/6 mice were subjected to TAC surgery and debanding by suture removal, or sham-debanding, between 4 (short duration) and 10 weeks (long duration) after TAC. Echocardiography was performed to assess cardiac function. RNA sequencing (RNAseq) of TAC and debanded hearts demonstrated activation of activin signaling with TAC that was relieved by debanding. Based on this, TAC-debanded animals were treated with an investigational modified activin receptor type IIB ligand trap, RKER-012 (10 mg/kg IP, bi-weekly), to inhibit signaling downstream of activin and related ligands. Results: Serial echocardiography of TAC-debanded animals showed greater dysfunction with longer duration TAC (Fractional shortening [FS]=39.2±3.84 for 4 weeks-TAC vs Sham: 61.2±0.94, p<0.05; FS=18.2±1.80 for 10 weeks-TAC vs Sham-TAC: 64.7±0.43, p<0.05). Cardiac functional recovery was slower and less complete in animals with longer duration TAC (10 weeks after debanding with TAC for 4 weeks, FS=57.8±1.41 vs 46.6±3.4 TAC for 10 weeks). RNAseq analysis of hearts post-debanding (10 weeks TAC+10 weeks debanding) showed a 5.73-fold decrease (p=2.57x10 -16 ) in FSTL3 expression, a biomarker of activin pathway signaling, suggesting a decrease in activin signaling accompanied functional recovery. To assess functional contribution of activin signaling to incomplete recovery and therapeutic potential of pathway inhibitors, we treated debanded animals (debanded 8 weeks post-TAC) with RKER-012 or placebo (TBS) for 4 weeks. RKER-012-treated mice showed significantly increased ejection fraction (54.12±1.50 vs placebo control 42.88±3.21; p=0.001) and reduced heart weight (p=0.01). Conclusions: Debanding after TAC mitigates adverse remodeling that is slower and less complete with longer duration TAC. A ligand trap (RKER-012) that was designed to inhibit signaling downstream of activin enhanced recovery after debanding and warrants further study as a potential therapeutic intervention in patients with incomplete functional recovery after TAVR.

370-OR: Optimized Weight Loss with Bimagrumab—Reduced Fat Mass with Increased Muscle Mass by Appetite-Independent Mechanisms

Background: Obesity is managed with lifestyle changes or incretin Tx to produce wt loss that is challenging to maintain long-term, perhaps because lean mass loss accounts for 20-40% of total wt loss. Semaglutide Tx results in rapid wt loss with 35% lower caloric intake, no further wt loss after 1 yr and rapid wt regain post-Tx. Bimagrumab (bima), a mAb to ActRIIA/ActRIIB, blocks activin pathways, leading to increased lean mass/decreased fat mass in numerous clinical studies (N=1561). Effects of bima IV or SC on fat and muscle were evaluated by DXA and MRI. Results: In a Ph2 study of bima 10 mg/kg IV q4wks vs placebo (respectively) in persons with overweight/obesity and T2DM (N=75), LS mean change at Wk 48 in body wt was −5.9 vs −0.8 kg (p<0.001; −7.5% vs −1.1%), with minimal change in daily caloric intake. DXA: LS mean change at Wk48 in total body (TB) fat mass was −7.5 vs −0.2 kg (p<0.001; −22.2% vs −0.3%), TB lean mass +1.7 vs −0.4 kg (p<0.001; +3.6% vs -0.9%), and appendicular lean mass +0.5 vs −0.3 kg (p=0.009; +2.5% vs −1.1%); fat mass loss was maintained 12 wks post-last dose. MRI: LS mean change at Wk24 in visceral adipose tissue was −1.5 vs +0.2 L (p<0.001; −36.1% vs +3.6%), absolute hepatic fat fraction (FF, %) −4.6 vs +0.2 (p=0.006; -23.6% vs +14.3%), and paravertebral muscle (PVM) mass +363.3 vs −331.0 mm2 (p=0.003; +6.4% vs -4.6%); a trend for decreased PVM fat fraction and intermuscular adipose tissue was observed (p=NS). Bima improved HbA1c (%) by -0.76 vs +0.04. AEs included diarrhea, muscle spasms. In a Ph1 study comparing bima 525 mg SC (N=12) and 700 mg IV (N=8), q4wks X3, fat mass loss and lean mass (total body and appendicular) increase were similar, with fat mass loss maintained 12 wks post-last dose; SC arm had fewer AEs than IV arm. Conclusions: Bimagrumab Tx results in decreased fat deposition in tissues and increased muscle mass despite minimal change in caloric intake, which could lead to durable, high quality wt loss. A study of bima in obesity without T2DM is ongoing (NCT05616013). Disclosure K.M.Attie: Employee; Versanis Bio. S.B.Heymsfield: None. L.Mindeholm: Consultant; Versanis Bio, Novartis AG, Stock/Shareholder; Novartis AG, Alcon Research, LLC, Novo Nordisk A/S. S.Spruill: None. M.Pruzanski: None. L.Klickstein: None.

KMT2D links TGF-β signaling to noncanonical activin pathway and regulates pancreatic cancer cell plasticity.

Although KMT2D, also known as MLL2, is known to play an essential role in development, differentiation, and tumor suppression, its role in pancreatic cancer development is not well understood. Here, we discovered a novel signaling axis mediated by KMT2D, which links TGF-β to the activin A pathway. We found that TGF-β upregulates a microRNA, miR-147b, which in turn leads to post-transcriptional silencing of KMT2D. Loss of KMT2D induces the expression and secretion of activin A, which activates a noncanonical p38 MAPK-mediated pathway to modulate cancer cell plasticity, promote a mesenchymal phenotype, and enhance tumor invasion and metastasis in mice. We observed a decreased KMT2D expression in human primary and metastatic pancreatic cancer. Furthermore, inhibition or knockdown of activin A reversed the protumoral role of KMT2D loss. These findings support a tumor-suppressive role of KMT2D in pancreatic cancer and identify miR-147b and activin A as novel therapeutic targets.

Serum and Pulmonary Expression Profiles of the Activin Signaling System in Pulmonary Arterial Hypertension.

Activins are novel therapeutic targets in pulmonary arterial hypertension (PAH). We therefore studied whether key members of the activin pathway could be used as PAH biomarkers. Serum levels of activin A, activin B, α-subunit of inhibin A and B proteins, and the antagonists follistatin and follistatin-like 3 (FSTL3) were measured in controls and in patients with newly diagnosed idiopathic, heritable, or anorexigen-associated PAH (n=80) at baseline and 3 to 4 months after treatment initiation. The primary outcome was death or lung transplantation. Expression patterns of the inhibin subunits, follistatin, FSTL3, Bambi, Cripto, and the activin receptors type I (ALK), type II (ACTRII), and betaglycan were analyzed in PAH and control lung tissues. Death or lung transplantation occurred in 26 of 80 patients (32.5%) over a median follow-up of 69 (interquartile range, 50-81) months. Both baseline (hazard ratio, 1.001 [95% CI, 1.000-1.001]; P=0.037 and 1.263 [95% CI, 1.049-1.520]; P=0.014, respectively) and follow-up (hazard ratio, 1.003 [95% CI, 1.001-1.005]; P=0.001 and 1.365 [95% CI, 1.185-1.573]; P<0.001, respectively) serum levels of activin A and FSTL3 were associated with transplant-free survival in a model adjusted for age and sex. Thresholds determined by receiver operating characteristic analyses were 393 pg/mL for activin A and 16.6 ng/mL for FSTL3. When adjusted with New York Heart Association functional class, 6-minute walk distance, and N-terminal pro-B-type natriuretic peptide, the hazard ratios for transplant-free survival for baseline activin A <393 pg/mL and FSTL3 <16.6 ng/mL were, respectively, 0.14 (95% CI, 0.03-0.61; P=0.009) and 0.17 (95% CI, 0.06-0.45; P<0.001), and for follow-up measures, 0.23 (95% CI, 0.07-0.78; P=0.019) and 0.27 (95% CI, 0.09-0.78, P=0.015), respectively. Prognostic values of activin A and FSTL3 were confirmed in an independent external validation cohort. Histological analyses showed a nuclear accumulation of the phosphorylated form of Smad2/3, higher immunoreactivities for ACTRIIB, ALK2, ALK4, ALK5, ALK7, Cripto, and FSTL3 in vascular endothelial and smooth muscle layers, and lower immunostaining for inhibin-α and follistatin. These findings offer new insights into the activin signaling system in PAH and show that activin A and FSTL3 are prognostic biomarkers for PAH.

KDM6A Regulates Cell Plasticity and Pancreatic Cancer Progression by Noncanonical Activin Pathway.

Background & AimsInactivating mutations of KDM6A, a histone demethylase, were frequently found in pancreatic ductal adenocarcinoma (PDAC). We investigated the role of KDM6A (lysine demethylase 6A) in PDAC development.MethodsWe performed a pancreatic tissue microarray analysis of KDM6A protein levels. We used human PDAC cell lines for KDM6A knockout and knockdown experiments. We performed bromouridine sequencing analysis to elucidate the effects of KDM6A loss on global transcription. We performed studies with Ptf1aCre; LSL-KrasG12D; Trp53R172H/+; Kdm6afl/fl or fl/Y, Ptf1aCre; Kdm6afl/fl or fl/Y, and orthotopic xenograft mice to investigate the impacts of Kdm6a deficiency on pancreatic tumorigenesis and pancreatitis.ResultsLoss of KDM6A was associated with metastasis in PDAC patients. Bromouridine sequencing analysis showed up-regulation of the epithelial–mesenchymal transition pathway in PDAC cells deficient in KDM6A. Loss of KDM6A promoted mesenchymal morphology, migration, and invasion in PDAC cells in vitro. Mechanistically, activin A and subsequent p38 activation likely mediated the role of KDM6A loss. Inhibiting either activin A or p38 reversed the effect. Pancreas-specific Kdm6a-knockout mice pancreata showed accelerated PDAC progression, developed a more aggressive undifferentiated type of PDAC, and increased metastases in the background of Kras and p53 mutations. Kdm6a-deficient pancreata in a pancreatitis model had a delayed recovery with increased PDAC precursor lesions compared with wild-type pancreata.ConclusionsLoss of KDM6A accelerates PDAC progression and metastasis, most likely by a noncanonical p38-dependent activin A pathway. KDM6A also promotes pancreatic tissue recovery from pancreatitis. Activin A might be used as a therapeutic target for KDM6A-deficient PDACs.

The effect of Activin pathway modulation on the expression of both pluripotency and differentiation markers during early zebrafish development compared with other vertebrates.

Activin-like factors control many developmental processes, including pluripotency maintenance and differentiation. Although Activin-like factors' action in mesendoderm induction has been demonstrated in zebrafish, their involvement in preserving the stemness remains unknown. To investigate the role of maternal Activin-like factors, their effects were promoted or blocked using synthetic human Activin A or SB-431542 treatments respectively until the maternal to zygotic transition. To study the role of zygotic Activin-like factors, SB-431542 treatment was also applied after the maternal to zygotic transition. The effect of the pharmacological modulations of the Activin/Smad pathway was then studied on the mRNA expressions of the ndr1, ndr2, tbxta (no tail/ntl) as the differentiation index, mych, nanog, and oct4 (pou5f3) as the pluripotency markers of the zebrafish embryonic cells as well as sox17 as a definitive endoderm marker. Expression of the target genes was measured at the 16-cell, 256-cell, 1K-cell, oblong, dome, and shield stages using the real-time quantitative polymerase chain reaction (RT-qPCR). Activation of the maternal Activin signaling pathway led to an increase in zygotic expression of the tbxta, particularly marked at the oblong stage. In other words, promotion of the maternal Activin/Smad pathway induced differentiation by advancing the major peaks of ndr1 and nanog, thereby eliciting tbxta expression. Whereas suppression of the maternal or zygotic Activin/Smad pathway sustained the pluripotency by preventing the major peaks of ndr1 and nanog as well as tbxta encoding.

Abstract 2657: Sex differences in pancreatic cancer cachexia manifestations and mechanisms in mice and humans: Role of activin

Abstract Introduction: Cachexia is a metabolic syndrome leading to weight loss and muscle wasting. Pancreatic ductal adenocarcinoma (PDAC) frequently associates with cachexia, which contributes to its high mortality rate. Sex differences have been observed in cancer cachexia (Zhong and Zimmers, Curr Osteopor Rep 2020); however, the underlying molecular mechanisms are mostly unknown. We studied this here in both humans and mouse models. Because Activin is an important mediator of PDAC cachexia (Zhong et al., J Cachexia Sarcopenia Muscle 2019); thus, we also evaluated how sex affects anti-Activin treatment response. Design: Mice: Male and female mice with autochthonic PDAC (KPC mice) were evaluated for cachexia phenotype and anti-Activin treatment response. Muscles were subjected to molecular and transcriptome/proteome analyses. Patients: Longitudinal change in body composition was measured retrospectively from CT scans of &amp;gt;130 patients with PDAC treated with first-line gemcitabine/nab-paclitaxel and compared by sex. TCGA was queried for Activin gene expression versus mortality. Rectus abdominus muscles from PDAC patients were profiled for Activin pathway gene expression. Results: Despite identical tumor latency and size, male KPC mice experienced earlier and more severe muscle wasting and responded positively to treatment with the Activin trap, ACVR2B/Fc, exhibiting muscle preservation, while female mice did not. Mediators and markers of muscle catabolism were increased in male KPC mice. RNAseq revealed increased muscle-specific E3 ligases, decreased myosin heavy chains, and inhibited canonical pathways in males with early cachexia, with fewer alterations in females. ACVR2B/Fc prevented many of these changes in late cachexia in males, but not in females, despite increased plasma Activin concentration in both sexes. Pathway analysis revealed sex-specific upstream regulators and mediators of muscle function. Muscle proteomics revealed impaired mitochondrial function in males only. Inhibitors of Activin-related ligands were upregulated in the muscle of female KPC mice only. Like mice, men with PDAC demonstrated greater loss of skeletal muscle area and index, and greater rate of muscle loss versus women. TCGA query revealed high tumor INHBA expression correlated with mortality, but only in men. Muscle from female patients with PDAC showed increased expression of Activin inhibitors, FSTL1, FSTL3, and WFIKKN2. Conclusions: Male mice and cancer patients have higher prevalence of cachexia and greater muscle wasting compared with females. Furthermore, the Activin pathway mediates cachexia in a sex-specific fashion, potentially through muscle-specific expression of Activin inhibitors. These results demonstrate sex as the first premise for cachexia precision therapy. Citation Format: Xiaoling Zhong, Ashok Narasimhan, Andrew R. Young, Libbie M. Silverman, Jianguo Liu, Sheng Liu, Emma H. Doud, Jun Wan, Yunlong Liu, Amber L. Mosley, Leonidas G. Koniaris, Teresa A. Zimmers. Sex differences in pancreatic cancer cachexia manifestations and mechanisms in mice and humans: Role of activin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2657.

Pressure Overload-Mediated Sustained PKR2 (Prokineticin-2 Receptor) Signaling in Cardiomyocytes Contributes to Cardiac Hypertrophy and Endotheliopathies.

[Figure: see text].

Regulatory expression of uncoupling protein 1 and its related genes by endogenous activity of the transforming growth factor-β family in bovine myogenic cells.

Uncoupling protein 1 (UCP1) is responsible for non-shivering thermogenesis, with restricted expression in brown/beige adipocytes in humans and rodents. We have previously shown an unexpected expression of UCP1 in bovine skeletal muscles. This study evaluated factors affecting Ucp1 gene expression in cultured bovine myogenic cells. Myosatellite cells, which were isolated from the bovine musculus longissimus cervicis, were induced to differentiate into myotubes in the presence of 2% horse serum. Previous studies using murine brown/beige adipocytes revealed that Ucp1 expression levels are directly increased by forskolin and all-trans retinoic acid (RA). The transforming growth factor-β (TGF-β)/activin pathway negatively regulated Ucp1 expression, whereas activation of the bone morphogenetic protein (BMP) pathway indirectly increases Ucp1 expression through the stimulation of brown/beige adipogenesis. Neither forskolin nor RA significantly affected Ucp1 mRNA levels in bovine myogenic cells. A-83-01, an inhibitor of the TGF-β/activin pathway, stimulated myogenesis in these cells. A-83-01 significantly increased the expression of some brown fat signature genes such as Pgc-1α, Cox7a1, and Dio2, with a quantitative but not significant increase in the expression of Ucp1. Treatment with LDN-193189, an inhibitor of the BMP pathway, did not affect the differentiation of bovine myosatellite cells. Rather, LDN-193189 increased Ucp1 mRNA levels without modulating the levels of other brown/beige adipocyte-related genes. The current results indicate that the regulation of Ucp1 expression in bovine myogenic cells is distinct from that in murine brown/beige adipocytes, which has been more intensely characterized. SIGNIFICANCE OF THE STUDY: We previously reported unexpected expression of Ucp1 in bovine muscle tissues; Ucp1 expression has been known to be detected predominantly in brown/beige adipocytes. This study examined regulatory expression of bovine Ucp1 in myogenic cells. Consistent with the changes in expression levels of brown/beige adipocyte-selective genes, Ucp1 expression tended to be increased by inhibition of endogenous TGF-β activity. In contrast, inhibition of endogenous BMP significantly increased Ucp1 expression without affecting brown/beige adipocyte-selective gene expression. The current results indicate that regulatory expression of Ucp1 in bovine myogenic cells is distinct from that in murine brown/beige adipocytes that is more intensely characterized.

Recapitulation of Neural Crest Specification and EMT via Induction from Neural Plate Border-like Cells

SummaryNeural crest cells (NCCs) contribute to several tissues during embryonic development. NCC formation depends on activation of tightly regulated molecular programs at the neural plate border (NPB) region, which initiate NCC specification and epithelial-to-mesenchymal transition (EMT). Although several approaches to investigate NCCs have been devised, these early events of NCC formation remain largely unknown in humans, and currently available cellular models have not investigated EMT. Here, we report that the E6 neural induction protocol converts human induced pluripotent stem cells into NPB-like cells (NBCs), from which NCCs can be efficiently derived. NBC-to-NCC induction recapitulates gene expression dynamics associated with NCC specification and EMT, including downregulation of NPB factors and upregulation of NCC specifiers, coupled with other EMT-associated cell-state changes, such as cadherin modulation and activation of TWIST1 and other EMT inducers. This strategy will be useful in future basic or translational research focusing on these early steps of NCC formation.

Drosophila Activin signaling promotes muscle growth through InR/TORC1-dependent and -independent processes.

The Myostatin/Activin branch of the TGF-β superfamily acts as a negative regulator of vertebrate skeletal muscle size, in part, through downregulation of insulin/insulin-like growth factor 1 (IGF-1) signaling. Surprisingly, recent studies in Drosophila indicate that motoneuron-derived Activin signaling acts as a positive regulator of muscle size. Here we demonstrate that Drosophila Activin signaling promotes the growth of muscle cells along all three axes: width, thickness and length. Activin signaling positively regulates the insulin receptor (InR)/TORC1 pathway and the level of Myosin heavy chain (Mhc), an essential sarcomeric protein, via increased Pdk1 and Akt1 expression. Enhancing InR/TORC1 signaling in the muscle of Activin pathway mutants restores Mhc levels close to those of the wild type, but only increases muscle width. In contrast, hyperactivation of the Activin pathway in muscles increases overall larval body and muscle fiber length, even when Mhc levels are lowered by suppression of TORC1. Together, these results indicate that the Drosophila Activin pathway regulates larval muscle geometry and body size via promoting InR/TORC1-dependent Mhc production and the differential assembly of sarcomeric components into either pre-existing or new sarcomeric units depending on the balance of InR/TORC1 and Activin signals.

The activin signaling transcription factor Smox is an essential regulator of appendage size during regeneration after autotomy in the crayfish.

Members of the phylum Arthropoda, comprising over 80% of total animal species, have evolved regenerative abilities, but little is known about the molecular mechanisms mediating this process. Transforming growth factor β (TGF-β) signaling mediates a diverse set of essential processes in animals and is a good candidate pathway for regulation of regeneration in arthropods. In this study we investigated the role of activin signaling, a TGF-β superfamily pathway, in limb regeneration in the crayfish. We identified and cloned a downstream transcription factor in the activin pathway, Smox, and characterized its function with regard to other elements of the activin signaling pathway. Gene knockdown of Smox by RNAi induced regeneration of complete but smaller pereopods after autotomy. This indicates that activin signaling via Smox functions in regulation of pereopod growth and size. The expression levels of both Smox and the activin receptor babo were closely correlated with molting. The expression level of Smox increased when babo was knocked down by RNAi, indicating that Smox and babo transcription are linked. Our study suggests that the Babo-Smox system in activin signaling is conserved in decapods, and supports an evolutionary conservation of this aspect of molecular signaling during regeneration between protostomes and deuterostomes.

Transcriptional up-regulation of the TGF-β intracellular signaling transducer Mad of Drosophila larvae in response to parasitic nematode infection.

The common fruit fly Drosophila melanogaster is an exceptional model for dissecting innate immunity. However, our knowledge on responses to parasitic nematode infections still lags behind. Recent studies have demonstrated that the well-conserved TGF-β signaling pathway participates in immune processes of the fly, including the anti-nematode response. To elucidate the molecular basis of TGF-β anti-nematode activity, we performed a transcript level analysis of different TGF-β signaling components following infection of D. melanogaster larvae with the nematode parasite Heterorhabditis gerrardi. We found no significant changes in the transcript level of most extracellular ligands in both bone morphogenic protein (BMP) and activin branches of the TGF-β signaling pathway between nematode-infected larvae and uninfected controls. However, extracellular ligand, Scw, and Type I receptor, Sax, in the BMP pathway as well as the Type I receptor, Babo, in the activin pathway were substantially up-regulated following H. gerrardi infection. Our results suggest that receptor up-regulation leads to transcriptional up-regulation of the intracellular component Mad in response to H. gerrardi following changes in gene expression of intracellular receptors of both TGF-β signaling branches. These findings identify the involvement of certain TGF-β signaling pathway components in the immune signal transduction of D. melanogaster larvae against parasitic nematodes.

Blocking activin actively treats cancer

Cancer Platinum-based chemotherapy is a mainstay of treatment for lung cancer. However, resistance to this therapy is common, as are dose-limiting side effects, particularly kidney toxicity. To search for mechanisms contributing to treatment resistance, Marini et al. performed a whole-genome RNA interference screen, which implicated the activin pathway. Inhibition of this pathway offered a dual benefit by potentiating the effects of platinum drugs in mouse models of cancer and protecting the animals from kidney damage. Thus, activin inhibitors could be a valuable addition to platinum chemotherapy, enhancing the efficacy of treatment while also allowing higher doses or longer periods of drug use. Sci. Transl. Med. 10 , eaat3504 (2018).

Adenovirus‑mediated knockdown of activin A receptor type2A attenuates immune‑induced hepatic fibrosis in mice and inhibits interleukin‑17‑induced activation of primary hepatic stellate cells.

Fibrosis induces a progressive loss of liver function, thus leading to organ failure. Activins are secreted proteins that belong to the transforming growth factor (TGF)-β superfamily, which initiate signaling by binding to their two type II receptors: Activin A receptor type 2A (ACVR2A) and activin A receptor type 2B. Previous studies that have explored the mechanisms underlying immune-induced hepatic fibrosis have mainly focused on TGF-β signaling, not activin signaling. To investigate the role of the activin pathway in this disease, adenovirus particles containing short hairpin (sh)RNA targeting ACVR2A mRNA (Ad-ACVR2A shRNA) were administered to mice, which were chronically treated with concanavalin A (Con A). The pathological changes in the liver were evaluated with hematoxylin/eosin staining, Masson trichrome staining and immunohistochemical assay. The results detected an increase in serum activin A and liver ACVR2A in Con A-treated animals. Conversely, liver function was partially restored and fibrotic injury was attenuated when activin signaling was blocked. In addition, the activation of hepatic stellate cells (HSCs) in response to Con A was suppressed by Ad-ACVR2A shRNA, as evidenced by decreased α-smooth muscle actin, and type I and IV collagen expression. Furthermore, primary mouse HSCs (mHSCs) were activated when exposed to interleukin (IL)-17A or IL-17F, which are two major cytokines produced by cluster of differentiation 4+ T helper 17 cells. The levels of activin A, type I and IV collagen were determined with ELISA kits and the expression of fibrotic molecules was determined with western blot analysis. Conversely, blocking activin/ACVR2A impaired the potency of HSCs to produce collagens in response to IL-17s. In addition, C terminus phosphorylation of Smad2 on Ser465 and Ser467, induced by either Con A in the liver or by IL-17s in mHSCs, was partly inhibited when activin A/ACVR2A signaling was suppressed. Collectively, the present study demonstrated an involvement of activated activin A/ACVR2A/Smad2 signaling in immune-induced hepatic fibrosis.

MiR‑203‑3p participates in the suppression of diabetes‑associated osteogenesis in the jaw bone through targeting Smad1.

Certain microRNAs (miRs) have important roles in the maintenance of bone development and metabolism, and a variety of miRs are known to be deregulated in diabetes. The present study investigated the role of miR-203-3p in the regulation of bone loss by assessing jaw bones of a rat model of type 2 diabetes. The results indicated that miR-203-3p inhibited osteogenesis in the jaws of diabetic rats and in rat bone marrow mesenchymal stem cells cultured in high-glucose medium. A luciferase re porter assay was used to verify the bioinformatics prediction that miR-203-3p targets the 3′-untranslated region of Smad1, which is an important mediator of the bone morphogenetic protein (BMP)/Smad pathway. Overexpression of Smad1 attenuated the miR-203-3p-mediated suppres sion of osteogenic differentiation. It was therefore indicated that the BMP/Smad pathway is attenuated and the transforming growth factor-β/activin pathway is promoted by Smad1 reduction. Taken together, it was indicated that miR-203-3p inhibits osteogenesis in jaw bones of diabetic rats by targeting Smad1 to inhibit the BMP/Smad pathway.

Blood-testis barrier integrity depends on Pin1 expression in Sertoli cells

The conformation and function of a subset of serine and threonine-phosphorylated proteins are regulated by the prolyl isomerase Pin1 through isomerization of phosphorylated Ser/Thr-Pro bonds. Pin1 is intensely expressed in Sertoli cells, but its function in this post mitotic cell remains unclear. Our aim was to investigate the role of Pin1 in the Sertoli cells. Lack of Pin1 caused disruption of the blood-testis barrier. We next investigated if the activin pathways in the Sertoli cells were affected by lack of Pin1 through immunostaining for Smad3 protein in testis tissue. Indeed, lack of Pin1 caused reduced Smad3 expression in the testis tissue, as well as a reduction in the level of N-Cadherin, a known target of Smad3. Pin1−/− testes express Sertoli cell marker mRNAs in a pattern similar to that seen in Smad3+/− mice, except for an increase in Wt1 expression. The resulting dysregulation of N-Cadherin, connexin 43, and Wt1 targets caused by lack of Pin1 might affect the mesenchymal–epithelial balance in the Sertoli cells and perturb the blood-testis barrier. The effect of Pin1 dosage in Sertoli cells might be useful in the study of toxicant-mediated infertility, gonadal cancer, and for designing male contraceptives.

Nodal/Activin Pathway is a Conserved Neural Induction Signal in Chordates.

Neural induction is the process through which pluripotent cells are committed to a neural fate. This first step of Central Nervous System formation is triggered by the "Spemann organizer" in amphibians and by homologous embryonic regions in other vertebrates. Studies in classical vertebrate models have produced contrasting views about the molecular nature of neural inducers and no unifying scheme could be drawn. Moreover, how this process evolved in the chordate lineage remains an unresolved issue. In this work, by using graft and micromanipulation experiments, we definitively establish that the dorsal blastopore lip of the cephalochordate amphioxus is homologous to the vertebrate organizer and is able to trigger the formation of neural tissues in a host embryo. In addition, we demonstrate that Nodal/Activin is the main signal eliciting neural induction in amphioxus, and that it also functions as a bona fide neural inducer in the classical vertebrate model Xenopus. Altogether, our results allow us to propose that Nodal/Activin was a major player of neural induction in the ancestor of chordates. This study further reveals the diversity of neural inducers deployed during chordate evolution and advocates against a universally conserved molecular explanation for this process.

The syndrome of central hypothyroidism and macroorchidism: IGSF1 controls TRHR and FSHB expression by differential modulation of pituitary TGF\u03b2 and Activin pathways

IGSF1 (Immunoglobulin Superfamily 1) gene defects cause central hypothyroidism and macroorchidism. However, the pathogenic mechanisms of the disease remain unclear. Based on a patient with a full deletion of IGSF1 clinically followed from neonate to adulthood, we investigated a common pituitary origin for hypothyroidism and macroorchidism, and the role of IGSF1 as regulator of pituitary hormone secretion. The patient showed congenital central hypothyroidism with reduced TSH biopotency, over-secretion of FSH at neonatal minipuberty and macroorchidism from 3 years of age. His markedly elevated inhibin B was unable to inhibit FSH secretion, indicating a status of pituitary inhibin B resistance. We show here that IGSF1 is expressed both in thyrotropes and gonadotropes of the pituitary and in Leydig and germ cells in the testes, but at very low levels in Sertoli cells. Furthermore, IGSF1 stimulates transcription of the thyrotropin-releasing hormone receptor (TRHR) by negative modulation of the TGFβ1-Smad signaling pathway, and enhances the synthesis and biopotency of TSH, the hormone secreted by thyrotropes. By contrast, IGSF1 strongly down-regulates the activin-Smad pathway, leading to reduced expression of FSHB, the hormone secreted by gonadotropes. In conclusion, two relevant molecular mechanisms linked to central hypothyroidism and macroorchidism in IGSF1 deficiency are identified, revealing IGSF1 as an important regulator of TGFβ/Activin pathways in the pituitary.

Activin A-induced signalling controls hair follicle neogenesis.

Acquisition of potent human dermal papilla (DP) cells that can induce hair follicle neogenesis is an overarching concern, and various approaches have been tried. In an attempt to solve the problem, we previously introduced the three-dimensional (3D) culture of human DP cells and observed de novo formation of hair follicles when conducting a patch hair reconstitution assay using 3D cultured DP spheres with mouse epidermal cells. In this study, we have subsequently focused our attention on activin A, one of the notably upregulated proteins in DP spheres compared with 2D cultured DP cells. We then adopted a small interfering RNA-mediated gene knock-down approach and hair reconstitution assay to investigate the role of activin A. We observed that human DP spheres with activin A knock-down are severely impaired in hair follicle neogenesis when combined with mouse epidermal cells. In addition, activin receptor 2B (ActvR2B) knock-down mouse epidermal cells showed severe impairment of hair follicle neogenesis when combined with human DP spheres. Moreover, recombinant activin A treatment of mouse epidermal cells increased the expression of downstream genes of the activin pathway. Taken together, our data strongly suggest that activin A-induced signalling plays a critical role in hair follicle neogenesis, which has not been previously reported.