The Hedgehog Signaling Pathway in Ischemic Tissues

Comparison of Three Antagonists of Hedgehog Pathway to Promote Skeletal Muscle Regeneration after High Dose Irradiation

The current geopolitical context has brought the radiological nuclear risk to the forefront of concerns. High-dose localized radiation exposure leads to the development of a musculocutaneous radiation syndrome affecting the skin and subcutaneous muscles. Despite the implementation of a gold standard treatment based on an invasive surgical procedure coupled with autologous cell therapy, a muscular defect frequently persists. Targeting the modulation of the Hedgehog (Hh) signaling pathway appears to be a promising therapeutic approach. Activation of this pathway enhances cell survival and promotes proliferation after irradiation, while inhibition by Cyclopamine facilitates differentiation. In this study, we compared the effects of three antagonists of Hh, Cyclopamine (CA), Vismodegib (VDG) and Sonidegib (SDG) on differentiation. A stable cell line of murine myoblasts, C2C12, was exposed to X-ray radiation (5 Gy) and treated with CA, VDG or SDG. Analysis of proliferation, survival (apoptosis), morphology, myogenesis genes expression and proteins production were performed. According to the results, VDG does not have a significant impact on C2C12 cells. SDG increases the expression/production of differentiation markers to a similar extent as CA, while morphologically, SDG proves to be more effective than CA. To conclude, SDG can be used in the same way as CA but already has a marketing authorization with an indication against basal cell cancers, facilitating their use in vivo. This proof of concept demonstrates that SDG represents a promising alternative to CA to promotes differentiation of murine myoblasts. Future studies on isolated and cultured satellite cells and in vivo will test this proof of concept.

Cerebral Perfusion Characteristics and Dynamic Brain Structural Changes in Stroke-Prone Renovascular Hypertensive Rats: A Preclinical Model for Cerebral Small Vessel Disease

Hypertension is a leading cause of cerebral small vessel disease (CSVD) and vascular dementia in elderly individuals. We aimed to assess cerebral perfusion and dynamic changes in brain structure in stroke-prone renovascular hypertensive rats (RHRSPs) with different durations of hypertension and to investigate whether they have pathophysiological features similar to those of humans with CSVD. The RHRSP model was established using the two-kidney, two-clip (2k2c) method, and the Morris water maze (MWM) test, MRI, immunohistochemistry, and biochemical analysis were performed at multiple time points for up to six months following the 2k2c operation. Systolic blood pressure was significantly greater in the RHRSP group than in the sham-operated group at week 4 post-surgery and continued to increase over time, leading to cognitive decline by week 20. Arterial spin labeling revealed cerebral hypoperfusion in the RHRSP group at 8 weeks, accompanied by vascular remodeling and decreased vessel density. Diffusion tensor imaging and Luxol fast blue staining indicated that white matter disintegration and demyelination gradually progressed in the corpus callosum and that myelin basic protein levels decreased. Eight weeks after surgery, blood-brain barrier (BBB) leakage into the corpus callosum was observed. The albumin leakage area was negatively correlated with the myelin sheath area (r=-0.88, p<0.001). RNA-seq analysis revealed downregulation of most angiogenic genes and upregulation of antiangiogenic genes in the corpus callosum of RHRSPs 24 weeks after surgery. RHRSPs developed cerebral hypoperfusion, BBB disruption, spontaneous white matter damage, and cognitive impairment as the duration of hypertension increased. RHRSPs share behavioral and neuropathological characteristics with CSVD patients, making them suitable animal models for preclinical trials related to CSVD.

Manipulation of Sonic Hedgehog Signaling Pathway in Maintenance, Differentiation, and Endocrine Activity of Insulin-Producing Cells: A Systematic Review

Background

Some studies have evaluated the manipulation of the sonic hedgehog (Shh) signaling pathway to generate more efficient insulin-producing cells (IPCs). In a systematic review, we evaluated in vitro and in vivo studies on the effect of inhibition or activation of the Shh pathway on the production, differentiation, maintenance, and endocrine activity of IPCs.

Methods

A systematic review was conducted using all available experimental studies published between January 2000 and November 2022. The review aimed at determining the effect of Shh manipulation on the differentiation of stem cells (SCs) into IPCs. Keywords and phrases using medical subject headings were extracted, and a complete search was performed in Web of Science, Embase, ProQuest, PubMed, Scopus, and Cochrane Library databases. The inclusion criteria were manipulation of Shh in SCs, SCs differentiation into IPCs, and endocrine activity of mature IPCs. Articles with incomplete data and duplications were excluded.

Results

A total of 208 articles were initially identified, out of which 11 articles were included in the study. The effect of Shh inhibition in the definitive endoderm stage to produce functional IPCs were confirmed. Some studies showed the importance of Shh re-activation at late-stage differentiation for the generation of efficient IPCs. It is proposed that baseline concentrations of Shh in mature pancreatic β-cells affect insulin secretion and endocrine activities of the cells. However, Shh overexpression in pancreatic β-cells ultimately leads to improper endocrine function and inadequate glucose-sensing insulin secretion.

Conclusion

Accurate manipulation of the Shh signaling pathway can be an effective approach in the production and maintenance of functional IPCs.

Therapeutic implication of Sonic Hedgehog as a potential modulator in ischemic injury

Sonic Hedgehog (SHh) is a homology protein that is involved in the modeling and development of embryonic tissues. As SHh plays both protective and harmful roles in ischemia, any disruption in the transduction and regulation of the SHh signaling pathway causes ischemia to worsen. The SHh signal activation occurs when SHh binds to the receptor complex of Ptc-mediated Smoothened (Smo) (Ptc-smo), which initiates the downstream signaling cascade. This article will shed light on how pharmacological modifications to the SHh signaling pathway transduction mechanism alter ischemic conditions via canonical and non-canonical pathways by activating certain downstream signaling cascades with respect to protein kinase pathways, angiogenic cytokines, inflammatory mediators, oxidative parameters, and apoptotic pathways. The canonical pathway includes direct activation of interleukins (ILs), angiogenic cytokines like hepatocyte growth factor (HGF), platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), and hypoxia-inducible factor alpha (HIF-), which modulate ischemia. The non-canonical pathway includes indirect activation of certain pathways like mTOR, PI3K/Akt, MAPK, RhoA/ROCK, Wnt/-catenin, NOTCH, Forkhead box protein (FOXF), Toll-like receptors (TLR), oxidative parameters such as GSH, SOD, and CAT, and some apoptotic parameters such as Bcl2. This review provides comprehensive insights that contribute to our knowledge of how SHh impacts the progression and outcomes of ischemic injuries.

Insight into the transcription factors regulating Ischemic Stroke and Glioma in Response to Shared Stimuli

Cerebral ischemic stroke and glioma are the two leading causes of patient mortality globally. Despite physiological variations, 1 in 10 people who have an ischemic stroke go on to develop brain cancer, most notably gliomas. In addition, glioma treatments have also been shown to increase the risk of ischemic strokes. Stroke occurs more frequently in cancer patients than in the general population, according to traditional literature. Unbelievably, these events share multiple pathways, but the precise mechanism underlying their co-occurrence remains unknown. Transcription factors (TFs), the main components of gene expression programmes, finally determine the fate of cells and homeostasis. Both ischemic stroke and glioma exhibit aberrant expression of a large number of TFs, which are strongly linked to the pathophysiology and progression of both diseases. The precise genomic binding locations of TFs and how TF binding ultimately relates to transcriptional regulation remain elusive despite a strong interest in understanding how TFs regulate gene expression in both stroke and glioma. As a result, the importance of continuing efforts to understand TF-mediated gene regulation is highlighted in this review, along with some of the primary shared events in stroke and glioma.

Blocking chondrocyte hypertrophy in conditional Evc knockout mice does not modify cartilage damage in osteoarthritis

Chondrocytes in osteoarthritic (OA) cartilage acquire a hypertrophic-like phenotype, where Hedgehog (Hh) signaling is pivotal. Hh overexpression causes OA-like cartilage lesions, whereas its downregulation prevents articular destruction in mouse models. Mutations in EVC and EVC2 genes disrupt Hh signaling, and are responsible for the Ellis-van Creveld syndrome skeletal dysplasia. Since Ellis-van Creveld syndrome protein (Evc) deletion is expected to hamper Hh target gene expression we hypothesized that it would also prevent OA progression avoiding chondrocyte hypertrophy. Our aim was to study Evc as a new therapeutic target in OA, and whether Evc deletion restrains chondrocyte hypertrophy and prevents joint damage in an Evc tamoxifen induced knockout (Evc^cKO ) model of OA. For this purpose, OA was induced by surgical knee destabilization in wild-type (WT) and Evc^cKO adult mice, and healthy WT mice were used as controls (n = 10 knees/group). Hypertrophic markers and Hh genes were measured by qRT-PCR, and metalloproteinases (MMP) levels assessed by western blot. Human OA chondrocytes and cartilage samples were obtained from patients undergoing knee joint replacement surgery. Cyclopamine (CPA) was used for Hh pharmacological inhibition and IL-1 beta as an inflammatory insult. Our results showed that tamoxifen induced inactivation of Evc inhibited Hh overexpression and partially prevented chondrocyte hypertrophy during OA, although it did not ameliorate cartilage damage in DMM-Evc^cKO mice. Hh pathway inhibition did not modify the expression of proinflammatory mediators induced by IL-1 beta in human OA chondrocytes in culture. We found that hypertrophic-IHH-and inflammatory-COX-2-markers co-localized in OA cartilage samples. We concluded that tamoxifen induced inactivation of Evc partially prevented chondrocyte hypertrophy in DMM-Evc^cKO mice, but it did not ameliorate cartilage damage. Overall, our results suggest that chondrocyte hypertrophy per se is not a pathogenic event in the progression of OA.

Muscle regeneration after high-dose radiation exposure: therapeutic potential of Hedgehog pathway modulation?

Purpose: Intentional or accidental exposure of relatively large as well as localized areas of the skin to ionizing radiation can lead to severe damage of many of its cellular components and cutaneous radiation syndrome. Patients can be treated with an invasive surgical procedure coupled with autologous cell therapy. However, this approach remains perfectible, especially for muscle repair. Indeed, a severe underlying muscle defect persists, in particular because of the damage to the satellite cells which ensure muscle regeneration. To overcome these shortcomings, a solution could be to develop new therapeutic strategies based on pharmacological treatments to improve post-irradiation muscle regeneration. In this study, we focus on the Hedgehog signaling pathway as a target, due to its involvement in myogenesis.Materials and methods: To evaluate the benefit of the pro-myogenic Hedgehog signaling pathway modulation, recombinant Sonic Hedgehog (rShh; agonist) or Cyclopamine (antagonist) were used in a stable cell line of mouse C2C12 myoblasts exposed to radiation (X-rays; 5 Gy). Our in vitro studies were carried out under either proliferation or differentiation conditions. Proliferation, migration, survival (apoptosis) and expression of myogenic genes/proteins were evaluated.Results: A high dose of radiation was shown to exert a serious negative impact in our in vitro model of mouse muscle progenitors after irradiation in proliferation or differentiation conditions. Interestingly, Hh pathway stimulation by rShh promotes the proliferation of myoblasts and their survival while its blockade by Cyclopamine significantly increases cell differentiation toward mature myotubes.Conclusion: These data suggest that, after irradiation, the sequence of activation and inhibition of the Hh pathway could allow rescue and proliferation of satellite cells, followed by their differentiation to regenerate new fibers. On the basis of these encouraging in vitro results, the second phase of our study will involve the in vivo validation of this treatment in a new murine model of ultra-localized muscle irradiation.

Placental Angiogenesis in Mammals: A Review of the Regulatory Effects of Signaling Pathways and Functional Nutrients

Normal placental development and proper angiogenesis are essential for fetal growth during pregnancy. Angiogenesis involves the regulatory action of many angiogenic factors and a series of signal transduction processes inside and outside the cell. The obstruction of placental angiogenesis causes fetal growth restriction and serious pregnancy complications, even leading to fetal loss and pregnancy cessation. In this review, the effects of placental angiogenesis on fetal development are described, and several signaling pathways related to placental angiogenesis and their key regulatory mediators are summarized. These factors, which include vascular endothelial growth factor (VEGF)-VEGF receptor, delta-like ligand 4 (DLL-4)-Notch, Wnt, and Hedgehog, may affect the placental angiogenesis process. Moreover, the degree of vascularization depends on cell proliferation, migration, and differentiation, which is affected by the synthesis and secretion of metabolites or intermediates and mutual coordination or inhibition in these pathways. Furthermore, we discuss recent advances regarding the role of functional nutrients (including amino acids and fatty acids) in regulating placental angiogenesis. Understanding the specific mechanism of placental angiogenesis and its influence on fetal development may facilitate the establishment of new therapeutic strategies for the treatment of preterm birth, pre-eclampsia, or intrauterine growth restriction, and provide a theoretical basis for formulating nutritional regulation strategies during pregnancy.

Pericardial fluid proteomic label-free quantification of differentially expressed proteins in ischemic heart disease patients with systolic dysfunction by nano-LC-ESI-MS/MS analysis

Left ventricular systolic dysfunction (LVSD) is common in patients with pre-existing ischemic heart disease (IHD) and myocardial infarction. An untargeted proteomic approach is used to improve the understanding of the molecular mechanisms associated with LVSD and to find out potential proteomic signatures in pericardial fluid. The pericardial fluid of IHD (n = 45) patients was grouped into two categories according to the left ventricular ejection fraction, LVEF ≥45 (n = 33) and LVEF <45 (n = 12), and analyzed by using nano-liquid chromatography-mass spectrometry (nano-LC-MS/MS) technique. The nano-LC-MS/MS analysis resulted in the identification of 709 pericardial fluid (PF) proteins in both normal and impaired systolic functional groups (LVEF ≥45 vs. LVEF <45). Sixteen proteins were found to be differentially expressed (p < 0.05, fold change >2) including 12 down-regulated and 4 up-regulated in the impaired systolic functional group (LVEF <45) compared to the normal group (LVEF ≥45). Among the differentially expressed proteins the inflammatory marker albumin, atherosclerosis marker apolipoprotein A-IV and hedgehog-interacting protein marker of angiogenesis were predominantly associated with the impaired LVEF <45 group. KEGG pathway analysis revealed that the hedgehog (Hh) signalling pathway is up-regulated in LVSD reflecting the underlying molecular and pathophysiological processes.