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Ligands of the transforming growth factor-β (TGF-β) superfamily are important targets for therapeutic intervention but present challenges because they signal combinatorially and exhibit overlapping activities in vivo. To obtain agents capable of sequestering multiple TGF-β superfamily ligands with novel selectivity, we generated soluble, heterodimeric ligand traps by pairing the extracellular domain (ECD) of the native activin receptor type IIB (ActRIIB) alternately with the ECDs of native type I receptors activin receptor-like kinase 4 (ALK4), ALK7, or ALK3. Systematic analysis of these heterodimeric constructs by surface plasmon resonance, and comparison with their homodimeric counterparts, revealed that each type I receptor partner confers a distinct ligand-binding profile to the heterodimeric construct. Additional characterization in cell-based reporter gene assays confirmed that the heterodimeric constructs possessed different profiles of signaling inhibition in vitro, which translated into altered patterns of pharmacological activity when constructs were administered systemically to wild-type mice. Our results detail a versatile platform for the modular recombination of naturally occurring receptor domains, giving rise to inhibitory ligand traps that could aid in defining the physiological roles of TGF-β ligand sets or be directed therapeutically to human diseases arising from dysregulated TGF-β superfamily signaling., (© 2021. The Author(s).)

The need for an autologous cell source for bone tissue engineering and medical applications has led researchers to explore multipotent mesenchymal stromal cells (MSC), which show stem cell plasticity, in various human tissues. However, MSC with different tissue origins vary in their biological properties and their capability for osteogenic differentiation. Furthermore, MSC-based therapies require large-scale ex vivo expansion, accompanied by cell type-specific replicative senescence, which affects osteogenic differentiation. To elucidate cell type-specific differences in the osteogenic differentiation potential and replicative senescence, we analysed the impact of BMP and TGF-β signaling in adipose-derived stromal cells (ASC), fibroblasts (FB), and dental pulp stromal cells (DSC). We used inhibitors of BMP and TGF-β signaling, such as SB431542, dorsomorphin and/or a supplemental addition of BMP-2. The expression of high-affinity binding receptors for BMP-2 and calcium deposition with alizarin red S were evaluated to assess osteogenic differentiation potential. Our study demonstrated that TGF-β signaling inhibits osteogenic differentiation of ASC, DSC and FB in the early cell culture passages. Moreover, DSC had the best osteogenic differentiation potential and an activation of BMP signaling with BMP-2 could further enhance this capacity. This phenomenon is likely due to an increased expression of activin receptor-like kinase-3 and -6. However, in DSC with replicative senescence (in cell culture passage 10), osteogenic differentiation sharply decreased, and the simultaneous use of BMP-2 and SB431542 did not result in further improvement of this process. In comparison, ASC retain a similar osteogenic differentiation potential regardless of whether they were in the early (cell culture passage 3) or later (cell culture passage 10) stages. Our study elucidated that ASC, DSC, and FB vary functionally in their osteogenic differentiation, depending on their tissue origin and replicative senescence. Therefore, our study provides important insights for cell-based therapies to optimize prospective bone tissue engineering strategies.

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a widespread disease causing obstruction of the nasal cavity. Its cause remains unclear. The transforming growth-factor beta (TGF-β) superfamily and their receptors, termed Activin receptor-like kinases (ALKs), have recently been suggested to play a role in local airway inflammation, but have so far not been evaluated in human nasal epithelial cells (HNECs) from CRSwNP patients. We demonstrated that ALK1-7 were expressed in the nasal polyp epithelium, and the expression of ALK1-6 was markedly elevated in polyps compared to nasal mucosa from healthy controls. Stimulation with the ALK ligand TGF-β1 decreased Ki67 expression in HNECs from CRSwNP patients, not evident in controls. Likewise, TGF-β1, Activin A and Activin B, all ALK ligands, decreased IL-8 release and Activin A and Activin B reduced ICAM1 expression on HNECs from CRSwNP patients, not seen in controls. Pre-stimulation with TGF-β1, Activin A, BMP4 and Activin B attenuated a TNF-α-induced ICAM1 upregulation on HNECs of CRSwNP. No effect was evident in controls. In conclusion, an increased expression of ALK1-6 was found on polyp epithelial cells and ligand stimulation appeared to reduce proliferation and local inflammation in polyps.

Taeniids exhibit a great adaptive plasticity, which facilitates their establishment, growth, and reproduction in a hostile inflammatory microenvironment. Transforming Growth Factor-β (TGFβ), a highly pleiotropic cytokine, plays a critical role in vertebrate morphogenesis, cell differentiation, reproduction, and immune suppression. TGFβ is secreted by host cells in sites lodging parasites. The role of TGFβ in the outcome of T. solium and T. crassiceps cysticercosis is herein explored. Homologues of the TGFβ family receptors (TsRI and TsRII) and several members of the TGFβ downstream signal transduction pathway were found in T. solium genome, and the expression of Type-I and -II TGFβ receptors was confirmed by RT-PCR. Antibodies against TGFβ family receptors recognized cysticercal proteins of the expected molecular weight as determined by Western blot, and different structures in the parasite external tegument. In vitro, TGFβ promoted the growth and reproduction of T. crassiceps cysticerci and the survival of T. solium cysticerci. High TGFβ levels were found in cerebrospinal fluid from untreated neurocysticercotic patients who eventually failed to respond to the treatment (P = 0.03) pointing to the involvement of TGFβ in parasite survival. These results indicate the relevance of TGFβ in the infection outcome by promoting cysticercus growth and treatment resistance.