sFRPs: a declaration of (Wnt) independence

PI3K/mTOR Inhibitor VS-5584 Alters Expression of WNT Signaling Genes and Induces Apoptosis in Lung Adenocarcinoma Cells: In Vitro and In Silico Insight

Lung cancer (LC) accounts for approximately 25% of all cancer cases, with 80-85% of these being non-small cell lung cancer (NSCLC). VS-5584 is a novel anti-cancer agent that specifically inhibits mTORC1/2 and class I PI3K isoforms. There is cross-talk between the PI3K-Akt-mTOR and WNT signaling pathways that are abnormally activated in NSCLC. In this study, we aimed to evaluate the anti-cancer effects of VS-5584 on A549 lung adenocarcinoma cells and changes in WNT signaling gene expression in vitro, while also correlating differentially expressed genes in silico. The effect of VS-5584 on A549 cell viability was assessed by the MTT assay. Apoptosis and cell cycle profiles were analyzed by flow cytometry, while WNT signaling gene expression was measured by quantitative RT-PCR. Differentially expressed genes (DEGs) in the TCGA LUAD and LUSC datasets were identified using the GEPIA2 platform. VS-5584 treatment induced apoptosis and caused cell cycle arrest at the G0/G1 phase in A549 cells. The mRNA expression levels of WNT signaling genes significantly decreased in treated cells. The expression of some upregulated DEGs in the datasets decreased in A549 cells treated with VS-5584. VS-5584 shows promise as an anti-cancer agent in the treatment of NSCLC by downregulating the expression of WNT signaling genes.

Chronic Wound Initiation: Single-Cell RNAseq of Cutaneous Wound Tissue and Contributions of Oxidative Stress to Initiation of Chronicity

Chronic wounds (CWs) in humans affect millions of people in the US alone, cost billions of dollars, cause much suffering, and still there are no effective treatments. Patients seek medical care when wound chronicity is already established, making it impossible to investigate factors that initiate chronicity. In this study, we used a diabetic mouse model of CWs that mimics many aspects of chronicity in humans. We performed scRNAseq to compare the cell composition and function during the first 72 h post-injury and profiled 102,737 cells into clusters of all major cell types involved in healing. We found two types of fibroblasts. Fib 1 (pro-healing) was enriched in non-CWs (NCWs) whereas Fib 2 (non-healing) was in CWs. Both showed disrupted proliferation and migration, and extracellular matrix (ECM) deposition in CWs. We identified several subtypes of keratinocytes, all of which were more abundant in NCWs, except for Channel-related keratinocytes, and showed altered migration, apoptosis, and response to oxidative stress (OS) in CWs. Vascular and lymphatic endothelial cells were both less abundant in CWs and both had impaired migration affecting the development of endothelial and lymphatic microvessels. Study of immune cells showed that neutrophils and mast cells are less abundant in CWs and that NCWs contained more proinflammatory macrophages (M1) whereas CWs were enriched in anti-inflammatory macrophages (M2). Also, several genes involved in mitochondrial function were abnormally expressed in CWs, suggesting impaired mitochondrial function and/or higher OS. Heat shock proteins needed for response to OS were downregulated in CWs, potentially leading to higher cellular damage. In conclusion, the initiation of chronicity is multifactorial and involves various cell types and cellular functions, indicating that one type of treatment will not fix all problems, unless the root cause is fundamental to the cell and molecular mechanisms of healing. We propose that such a fundamental process is high OS and its association with wound infection/biofilm.

Secreted Frizzled-Related Protein 1a regulates hematopoietic development in a dose-dependent manner

Hematopoietic stem and progenitor cells (HSPCs) arise only during embryonic development, and their identity specification, emergence from the floor of the dorsal aorta, and proliferation are all tightly regulated by molecular mechanisms such as signaling cues. Among these, Wnt signaling plays an important role in HSPC specification, differentiation, and self-renewal, requiring precise modulation for proper development and homeostasis. Wnt signaling is initiated when a Wnt ligand binds to cell surface receptors such as those encoded by the frizzled gene family, activating intracellular signaling pathways that regulate gene expression. Secreted frizzled-related proteins (Sfrps) are known modulators of Wnt signaling, acting as both agonists and antagonists of this pathway. Yet, in vivo functions of Sfrps in HSPC development remain incompletely understood. Here, we demonstrate that Sfrp1a regulates zebrafish HSPC development and differentiation in a dose-dependent manner. In Sfrp1a loss of function animals, we observe an increase in HSPCs, an upregulation of canonical Wnt signaling, and a decrease in differentiation into both lymphoid and myeloid lineages. Conversely, at low-dose sfrp1a overexpression, there is a decrease in HSPCs and an increase in lymphoid differentiation. High-dose sfrp1a overexpression phenocopies the loss of function animals, with an increase in HSPCs, increased canonical Wnt signaling, and decreased lymphoid and myeloid differentiation. These findings highlight the importance of dose-dependent modulation of Sfrps, paralleling what is observed in hematopoietic cancers where SFRP1 loss-of-function and gain-of-function variants can drive tumorigenesis.

The pericardium forms as a distinct structure during heart formation

The heart integrates diverse cell lineages into a functional unit, including the pericardium, a mesothelial sac that supports heart movement, homeostasis, and immune responses. However, despite its critical roles, the developmental origins of the pericardium remain uncertain due to disparate models. Here, using live imaging, lineage tracking, and single-cell transcriptomics in zebrafish, we find the pericardium forms within the lateral plate mesoderm from dedicated anterior mesothelial progenitors and distinct from the classic heart field. Imaging of transgenic reporters in zebrafish documents lateral plate mesoderm cells that emerge lateral of the classic heart field and among a continuous mesothelial progenitor field. Single-cell transcriptomics and trajectories of hand2-expressing lateral plate mesoderm reveal distinct populations of mesothelial and cardiac precursors, including pericardial precursors that are distinct from the cardiomyocyte lineage. The mesothelial gene expression signature is conserved in mammals and carries over to post-natal development. Light sheet-based live-imaging and machine learning-supported cell tracking documents that during heart tube formation, pericardial precursors that reside at the anterior edge of the heart field migrate anteriorly and medially before fusing, enclosing the embryonic heart to form a single pericardial cavity. Pericardium formation proceeds even upon genetic disruption of heart tube formation, uncoupling the two structures. Canonical Wnt/β-catenin signaling modulates pericardial cell number, resulting in a stretched pericardial epithelium with reduced cell number upon canonical Wnt inhibition. We connect the pathological expression of secreted Wnt antagonists of the SFRP family found in pediatric dilated cardiomyopathy to increased pericardial stiffness: sFRP1 in the presence of increased catecholamines causes cardiomyocyte stiffness in neonatal rats as measured by atomic force microscopy. Altogether, our data integrate pericardium formation as an independent process into heart morphogenesis and connect disrupted pericardial tissue properties such as pericardial stiffness to pediatric cardiomyopathies.

The concept of Sfrp1+ transitional fibroblasts: the key to dissociating lineage heterogeneity and fate of invasive fibroblasts in pulmonary fibrosis?

One of the significant advances in the biology of idiopathic pulmonary fibrosis (IPF) has been the recognition of fibroblast heterogeneity in the lung. Fibroblast heterogeneity can be interpreted as fibroblast subtypes, probably derived from distinct mesenchymal lineages, as well as various activation states, such as proliferation, matrix production and invasiveness. With great interest, we read the original work by Mayr et al. [1] presenting a concept that the Sfrp1+ transitional fibroblasts with low invasive capacity emerge early after bleomycin-induced injury and ultimately transit to Spp1/Cthrc1+ matrix-producing (myo)fibroblasts with the driving force of transforming growth factor (TGF)β1 signalling from myeloid and epithelial lineages. This study largely aligns with our recent publication proposing that multiple fibroblast subtypes from IPF lungs contribute to the invasive phenotype of fibroblasts and the matrix deposition in pulmonary fibrosis [2].

The novel concept of Sfrp1+ transitional fibroblasts has sparked novel points of interest: the mechanisms under which the Sfrp1+ transitional fibroblasts emerge and the in vivo functions of Sfrp1 and Sfrp1+ transitional fibroblasts in pulmonary fibrosis https://bit.ly/4aq6iAI

Non-muscle-invasive bladder cancer molecular subtypes predict differential response to intravesical Bacillus Calmette-Guérin

The recommended treatment for patients with high-risk non-muscle-invasive bladder cancer (HR-NMIBC) is tumor resection followed by adjuvant Bacillus Calmette-Guérin (BCG) bladder instillations. However, only 50% of patients benefit from this therapy. If progression to advanced disease occurs, then patients must undergo a radical cystectomy with risks of substantial morbidity and poor clinical outcome. Identifying tumors unlikely to respond to BCG can translate into alternative treatments, such as early radical cystectomy, targeted therapies, or immunotherapies. Here, we conducted molecular profiling of 132 patients with BCG-naive HR-NMIBC and 44 patients with recurrences after BCG (34 matched), which uncovered three distinct BCG response subtypes (BRS1, 2 and BRS3). Patients with BRS3 tumors had a reduced recurrence-free and progression-free survival compared with BRS1/2. BRS3 tumors expressed high epithelial-to-mesenchymal transition and basal markers and had an immunosuppressive profile, which was confirmed with spatial proteomics. Tumors that recurred after BCG were enriched for BRS3. BRS stratification was validated in a second cohort of 151 BCG-naive patients with HR-NMIBC, and the molecular subtypes outperformed guideline-recommended risk stratification based on clinicopathological variables. For clinical application, we confirmed that a commercially approved assay was able to predict BRS3 tumors with an area under the curve of 0.87. These BCG response subtypes will allow for improved identification of patients with HR-NMIBC at the highest risk of progression and have the potential to be used to select more appropriate treatments for patients unlikely to respond to BCG.

The diagnostic, prognostic role and molecular mechanism of miR-328 in human cancer

MicroRNA are non-coding small RNAs that bind to their target mRNA and cause mRNA degradation or translation inhibition. MiRNA dysregulation is linked to a variety of human cancers and has a role in the genesis and development of cancer pathology. MiR-328 has been reported to be involved in various human cancers. And miR-328 is considered a key regulator in human cancer. It participates in biological processes such as proliferation, apoptosis, invasion, migration, and EMT. The present review will combine the basic and clinical studies to find that miR-328 promotes tumorigenesis and metastasis in human cancer. And we will describe the diagnostic, prognostic, and therapeutic value of miR-328 in various human cancers.

SFRP1 Negatively Modulates Pyroptosis of Fibroblast-Like Synoviocytes in Rheumatoid Arthritis: A Review

Secreted frizzled-related protein 1 (SFRP1) is a member of secretory glycoprotein SFRP family. As a primitive gene regulating cell growth, development and transformation, SFRP1 is widely expressed in human cells, including various cancer cells and fibroblast-like synoviocytes (FLS) of rheumatoid arthritis (RA). Deletion or silencing of SFRP1 involves epigenetic and other mechanisms, and participates in biological behaviors such as cell proliferation, migration and cell pyroptosis, which leads to disease progression and poor prognosis. In this review, we discuss the role of SFRP1 in the pathogenesis of RA-FLS and summarize different experimental platforms and recent research results. These are helpful for understanding the biological characteristics of SFRP1 in RA, especially the mechanism by which SFRP1 regulates RA-FLS pyroptosis through Wnt/β-catenin and Notch signaling pathways. In addition, the epigenetic regulation of SFRP1 in RA-FLS is emphasized, which may be considered as a promising biomarker and therapeutic target of RA.

WNT Signalling in Osteoarthritis and Its Pharmacological Targeting

Osteoarthritis (OA) is a highly disabling musculoskeletal condition affecting millions of people worldwide. OA is characterised by progressive destruction and irreversible morphological changes of joint tissues and architecture. At molecular level, de-regulation of several pathways contributes to the disruption of tissue homeostasis in the joint. Overactivation of the WNT/β-catenin signalling pathway has been associated with degenerative processes in OA. However, the multiple layers of complexity in the modulation of the signalling and the still insufficient knowledge of the specific molecular drivers of pathogenetic mechanisms have made difficult the pharmacological targeting of this pathway for therapeutic purposes. This review aims to provide an overview of the WNT/β-catenin signalling in OA with a particular focus on its role in the articular cartilage. Pathway components whose targeting showed therapeutic potential will be highlighted and described. A specific section will be dedicated to Lorecivivint, the first inhibitor of the β-catenin-dependent pathway currently in phase III clinical trial as OA-modifying agent.

Opposite Roles of Wnt7a and Sfrp1 in Modulating Proper Development of Neural Progenitors in the Mouse Cerebral Cortex

The Wingless (Wnt)-mediated signals are involved in many important aspects of development of the mammalian cerebral cortex. How Wnts interact with their modulators in cortical development is still unclear. Here, we show that Wnt7a and secreted frizzled-related protein 1 (Sfrp1), a soluble modulator of Wnts, are co-expressed in mouse embryonic cortical neural progenitors (NPs). Knockout of Wnt7a in mice causes microcephaly due to reduced NP population and neurogenesis, and Sfrp1 has an opposing effect compared to Wnt7a. Similar to Dkk1, Sfrp1 decreases the Wnt1 and Wnt7a activity in vitro. Our results suggest that Wnt7a and Sfrp1 play opposite roles to ensure proper NP progeny in the developing cortex.

Matricellular proteins in cancer: a focus on secreted Frizzled-related proteins

Tumours are complex entities, wherein cancer cells interact with myriad soluble, insoluble and cell associated factors. These microenvironmental mediators regulate tumour growth, progression and metastasis, and are produced by cancer cells and by stromal components such as fibroblast, adipocytes and immune cells. Through their ability to bind to extracellular matrix proteins, cell surface receptors and growth factors, matricellular proteins enable a dynamic reciprocity between cancer cells and their microenvironment. Hence, matricellular proteins play a critical role in tumour progression by regulating where and when cancer cells are exposed to key growth factors and regulatory proteins. Recent studies suggest that, in addition to altering Wingless (Wnt) signalling, certain members of the Secreted Frizzled Related Protein (sFRP) family are matricellular in nature. In this review, we outline the importance of matricellular proteins in cancer, and discuss how sFRPs may function to both inhibit and promote cancer progression in a context-dependent manner. By considering the matricellular functionality of sFRPs, we may better understand their apparently paradoxical roles in cancers.

Methylation-mediated loss of SFRP2 enhances invasiveness of non-small cell lung cancer cells

The malignancy of non-small cell lung cancer (NSCLC) largely results from its invasive manner. Secreted frizzled-related proteins (SFRPs) have been recently found to suppress the invasiveness of some cancers. On the other hand, the methylation of SFRPs increases protein degradation to reduce the activity of SFRPs, resulting in increased tumor cell invasion and cancer metastasis. However, the role of SFRPs in the invasion of NSCLC has not been reported. Here we analyzed the regulation of SFRPs in NSCLC cells and its effects on cell invasion. We found that SFRP2 mRNA was significantly decreased and methylation of SFRP2 gene was significantly increased in NSCLC tissue, compared to the paired adjacent nontumor tissue. Moreover, SFRP2 expression was significantly decreased in NSCLC cell lines. In NSCLC cell lines, the SFRP2 expression would be restored by the demethylation of SFRP2 gene with 5'-aza-deoxycytidine in NSCLC cell lines, at the levels of both mRNA and protein. Thus, the cell invasion would be suppressed. Furthermore, the demethylation of SFRP2 gene appeared to inhibit Zinc Finger E-Box Binding Homeobox 1 (ZEB1) and matrix metallopeptidase 9 (MMP9), two key factors that enhance NSCLC cell invasion. Thus, SFRP2 may inhibit NSCLC invasion by suppressing ZEB1 and MMP9, while its methylation promotes NSCLC invasion.

Enhanced Wnt signaling by methylation-mediated loss of SFRP2 promotes osteosarcoma cell invasion

Wnt signaling is essential for the initiation and progression of osteosarcoma (OS) tumors and is suppressed by the secreted frizzled-related proteins (SFRPs). The methylation-induced protein degradation reduces the activity of SFRPs and subsequently increases the activity of Wnt signaling. However, whether the methylation of SFRP2, a member of SFRPs, may be involved in the pathogenesis of OS is not known. Here, we investigated the expression levels of SFRP2 in OS specimens. We found that SFRP2 mRNA was significantly decreased and methylation of SFRP2 gene was significantly increased in malignant OS tumors as compared to the paired adjacent non-tumor tissue. Moreover, SFRP2 expression was significantly decreased in the malignant OS cell lines, SAOS2, MG63, and U2OS, but not in the primary osteoblast cells. The demethylation of SFRP2 gene by 5'-aza-deoxycytidine (5-aza-dCyd) in OS cell lines restored SFRP2 expression, at both mRNA and protein levels, and suppressed cell invasion. Furthermore, the demethylation of SFRP2 gene appeared to inhibit nuclear retention of a key Wnt signaling factor, β-catenin, in OS cell lines. Together, these data suggest that SFRP2 may function as an OS invasion suppressor by interfering with Wnt signaling, and the methylation of SFRP2 gene may promote pathogenesis of OS.

Tissue-nonspecific alkaline phosphatase as a target of sFRP2 in cardiac fibroblasts

Recent studies of myocardial infarction in secreted Frizzled-related protein 2 (sFRP2) knockout mice and our hamster heart failure therapy based on sFRP2 blockade have established sFRP2 as a key profibrotic cytokine in the heart. The failing hamster heart is marked by prominent fibrosis and calcification with elevated expression of sFRP2. Noting the involvement of tissue-nonspecific alkaline phosphatase (TNAP) in bone mineralization and vascular calcification, we determined whether sFRP2 might be an upstream regulator of TNAP. Biochemical assays revealed an approximately twofold increase in the activity of TNAP and elevated levels of inorganic phosphate (Pi) in the failing heart compared with the normal heart. Neither was this change detected in the liver or hamstring muscle nor was it associated with systemic hyperphosphatemia. TNAP was readily cloned from the hamster heart and upon overexpression increased the level of extracellular but not intracellular Pi, which is consistent with the cell surface location of the ectoenzyme. In line with the previous demonstration that sFRP2 blockade attenuated fibrosis, we show here that the therapy downregulated TNAP. This in vivo finding is corroborated by the in vitro study showing that cultured cardiac fibroblasts treated with recombinant sFRP2 protein exhibited progressive increase in the expression and activity of TNAP, which was completely abrogated by cycloheximide or tunicamycin. Induction of TNAP by sFRP2 is restricted to cardiac fibroblasts among the multiple cell types examined, and was not observed with sFRP4. The current work indicates that sFRP2 may promote cardiac fibrocalcification through coordinate activation of tolloid-like metalloproteinases and TNAP.

The non-canonical BMP and Wnt/β-catenin signaling pathways orchestrate early tooth development

BMP and Wnt signaling pathways play a crucial role in organogenesis, including tooth development. Despite extensive studies, the exact functions, as well as if and how these two pathways act coordinately in regulating early tooth development, remain elusive. In this study, we dissected regulatory functions of BMP and Wnt pathways in early tooth development using a transgenic noggin (Nog) overexpression model (K14Cre;pNog). It exhibits early arrested tooth development, accompanied by reduced cell proliferation and loss of odontogenic fate marker Pitx2 expression in the dental epithelium. We demonstrated that overexpression of Nog disrupted BMP non-canonical activity, which led to a dramatic reduction of cell proliferation rate but did not affect Pitx2 expression. We further identified a novel function of Nog by inhibiting Wnt/β-catenin signaling, causing loss of Pitx2 expression. Co-immunoprecipitation and TOPflash assays revealed direct binding of Nog to Wnts to functionally prevent Wnt/β-catenin signaling. In situ PLA and immunohistochemistry on Nog mutants confirmed in vivo interaction between endogenous Nog and Wnts and modulation of Wnt signaling by Nog in tooth germs. Genetic rescue experiments presented evidence that both BMP and Wnt signaling pathways contribute to cell proliferation regulation in the dental epithelium, with Wnt signaling also controlling the odontogenic fate. Reactivation of both BMP and Wnt signaling pathways, but not of only one of them, rescued tooth developmental defects in K14Cre;pNog mice, in which Wnt signaling can be substituted by transgenic activation of Pitx2. Our results reveal the orchestration of non-canonical BMP and Wnt/β-catenin signaling pathways in the regulation of early tooth development.

Secreted frizzled related proteins inhibit fibrosis in vitro but appear redundant in vivo

BACKGROUND

The pathogenesis of pulmonary fibrosis remains poorly understood. The Wnt signaling pathway regulates fibrogenesis in different organs. Here, we studied the role of two extracellular Wnt antagonists, secreted frizzled-related protein-1 (SFRP1) and frizzled-related protein (FRZB) on lung fibrosis in vitro and in vivo. For this purpose, we used an alveolar epithelial cell line and a lung fibroblast cell line, and the bleomycin-induced lung fibrosis model, respectively.

RESULTS

During the course of bleomycin-induced lung fibrosis, Sfrp1 and Frzb expression are upregulated. Expression of Sfrp1 appears much higher than that of Frzb. In vitro, recombinant SFRP1, but not FRZB, counteracts the transforming growth factor β1 (TGFβ1)-induced upregulation of type I collagen expression both in pulmonary epithelial cells and fibroblasts. Both SFRP1 and FRZB inhibit the TGFβ1-induced increase of active β-catenin, but do not influence the TGFβ1-induced phosphorylation levels of SMAD3, positioning Wnt signaling activity downstream of the active TGFβ signal in lung fibroblasts, but not in alveolar epithelial cells. In vivo, Sfrp1 (-/-) and Frzb (-/-) mice showed identical responses to bleomycin in the lung compared to wild-type controls.

CONCLUSIONS

Although SFRP1 counteracts the effect of TGFβ1 in pulmonary cells in vitro; loss of neither SFRP1 nor FRZB alters fibrotic outcomes in the lungs in vivo. The lack of in vivo effect in the absence of specific SFRPs suggests functional redundancy within this family of Wnt antagonists.

Secreted Frizzled-related protein 2 as a target in antifibrotic therapeutic intervention

Progressive fibrosis is a pathological hallmark of many chronic diseases responsible for organ failure. Although there is currently no therapy on the market that specifically targets fibrosis, the dynamic fibrogenic process is known to be regulated by multiple soluble mediators that may be therapeutically intervened. The failing hamster heart exhibits marked fibrosis and increased expression of secreted Frizzled-related protein 2 (sFRP2) amenable to reversal by mesenchymal stem cell (MSC) therapy. Given the previous demonstration that sFRP2-null mice subjected to myocardial infarction exhibited reduced fibrosis and improved function, we tested whether antibody-based sFRP2 blockade might counteract the fibrogenic pathway and repair cardiac injury. Cardiomyopathic hamsters were injected intraperitoneally twice a week each with 20 μg of sFRP2 antibody. Echocardiography, histology, and biochemical analyses were performed after 1 mo. sFRP2 antibody increased left ventricular ejection fraction from 40 ± 1.2 to 49 ± 6.5%, whereas saline and IgG control exhibited a further decline to 37 ± 0.9 and 31 ± 3.2%, respectively. Functional improvement is associated with a ∼ 50% reduction in myocardial fibrosis, ∼ 65% decrease in apoptosis, and ∼ 75% increase in wall thickness. Consistent with attenuated fibrosis, both MSC therapy and sFRP2 antibody administration significantly increased the activity of myocardial matrix metalloproteinase-2. Gene expression analysis of the hamster heart and cultured fibroblasts identified Axin2 as a downstream target, the expression of which was activated by sFRP2 but inhibited by therapeutic intervention. sFRP2 blockade also increased myocardial levels of VEGF and hepatocyte growth factor (HGF) along with increased angiogenesis. These findings highlight the pathogenic effect of dysregulated sFRP2, which may be specifically targeted for antifibrotic therapy.

The Wnt inhibitor secreted Frizzled-Related Protein 1 (sFRP1) promotes human Th17 differentiation

Wnt/β-catenin signaling plays a crucial role during embryogenesis and tumorigenesis, and in T cells, promotes the differentiation of Th2 cells. However, the role of Wnt signals in the differentiation and maintenance of human Th17 cells remains poorly understood. We found that the higher levels of IL-17 in the synovial fluid of rheumatoid arthritis (RA) patients compared with that of osteoarthritis (OA) patients were associated with a higher concentration of sFRP1 (secreted Frizzled-Related Protein 1), an inhibitor of the Wnt/β-catenin pathway. The addition of sFRP1 during TCR-mediated stimulation induced a significant increase in IL-17 production by both naïve and memory CD4(+) T cells. Moreover, under Th17-differentiation conditions, the addition of sFRP1 significantly reduced the requirement for TGF-β. Mechanistically, we observed that sFRP1 significantly enhanced the phosphorylation of Smad2/3 in CD4(+) T cells upon TGF-β stimulation and that blocking TGF-β signaling abolished the Th17-promoting activity of sFRP1. Our findings reveal a novel function for sFRP1 as a potent inducer of human Th17-cell differentiation. Consequently, sFRP1 may represent a promising target for the treatment of Th17-mediated disease in humans.

SOST and DKK: Antagonists of LRP Family Signaling as Targets for Treating Bone Disease

The study of rare human genetic disorders has often led to some of the most significant advances in biomedical research. One such example was the body of work that resulted in the identification of the Low Density Lipoprotein-Related Protein (LRP5) as a key regulator of bone mass. Point mutations were identified that encoded forms of LRP5 associated with very high bone mass (HBM). HBM patients live to a normal age and do not appear to have increased susceptibility to carcinogenesis or other disease. Thus, devising methods to mimic the molecular consequences of this mutation to treat bone diseases associated with low bone mass is a promising avenue to pursue. Two groups of agents related to putative LRP5/6 functions are under development. One group, the focus of this paper, is based on antagonizing the functions of putative inhibitors of Wnt signaling, Dickkopf-1 (DKK1), and Sclerostin (SOST). Another group of reagents under development is based on the observation that LRP5 may function to control bone mass by regulating the secretion of serotonin from the enterrochromaffin cells of the duodenum.