Hypoxia-Inducible Factor-1α (HIF-1α) as a Biomarker for Changes in Microcirculation in Individuals with Systemic Sclerosis

The Genetic and Biological Basis of Pseudoarthrosis in Fractures: Current Understanding and Future Directions

Pseudoarthrosis-the failure of normal fracture healing-remains a significant orthopedic challenge affecting approximately 10-15% of long bone fractures, and is associated with significant pain, prolonged disability, and repeated surgical interventions. Despite extensive research into the pathophysiological mechanisms of bone healing, diagnostic approaches remain reliant on clinical findings and radiographic evaluations, with little innovation in tools to predict or diagnose non-union. The present review evaluates the current understanding of the genetic and biological basis of pseudoarthrosis and highlights future research directions. Recent studies have highlighted the potential of specific molecules and genetic markers to serve as predictors of unsuccessful fracture healing. Alterations in mesenchymal stromal cell (MSC) function, including diminished osteogenic potential and increased cellular senescence, are central to pseudoarthrosis pathogenesis. Molecular analyses reveal suppressed bone morphogenetic protein (BMP) signaling and elevated levels of its inhibitors, such as Noggin and Gremlin, which impair bone regeneration. Genetic studies have uncovered polymorphisms in BMP, matrix metalloproteinase (MMP), and Wnt signaling pathways, suggesting a genetic predisposition to non-union. Additionally, the biological differences between atrophic and hypertrophic pseudoarthrosis, including variations in vascularity and inflammatory responses, emphasize the need for targeted approaches to management. Emerging biomarkers, such as circulating microRNAs (miRNAs), cytokine profiles, blood-derived MSCs, and other markers (B7-1 and PlGF-1), have the potential to contribute to early detection of at-risk patients and personalized therapeutic approaches. Advancing our understanding of the genetic and biological underpinnings of pseudoarthrosis is essential for the development of innovative diagnostic tools and therapeutic strategies.

Association Between Hypoxia-Inducible Factor-1α and Neurological Diseases: A Bidirectional Two-Sample Mendelian Randomization Analysis

BACKGROUND

Previous studies have suggested that hypoxia-inducible factor 1-α (HIF-1α) exerted multiple effects on different central nervous system disorders. However, it is still uncertain whether plasma HIF-1α can be a causal indicator for the relevant diseases. This study aimed to test the causality relationship between plasma HIF-1α and neurological diseases, including cerebrovascular diseases, migraines, and neurodegenerative diseases with a Mendelian randomization (MR) method.

METHODS

Single-nucleotide polymorphisms (SNPs) genetically representing plasma HIF-1α were screened as instrumental variables (IVs). Summary-level data for neurological disorder from genome-wide association studies (GWAS) were identified as outcomes. The causal effects between the IVs and outcomes were determined via the major analysis of inverse-variance-weighted (IVW) method. The reverse causal direction was also performed to investigate the possibility of reverse causation.

RESULTS

The findings revealed that plasma HIF-1α was identified to be genetically associated with cardioembolic stroke (CES) (OR = 0.885; 95% confidence interval [CI] = 0.796-0.985, p = 0.026), migraine (OR = 0.941, 95% CI = 0.888-0.998, p = 0.041), and drug-induced migraine without aura (MOA) (OR = 0.586, 95% CI = 0.375-0.916, p = 0.019). There was no association identified in plasma HIF-1α with subarachnoid hemorrhage (SAH), other stroke and migraine subtype, and neurodegenerative disorders. The reverse-MR analysis revealed that the above-stated neurological diseases did not have a causal effect on plasma HIF-1α levels. Sensitivity and validation analyses support that the above results are stable.

CONCLUSIONS

Our research indicated that plasma HIF-1α may have a causal effect on the risk of CES, migraine and drug-induced MOA, providing new insights for those disease prevention and therapeutic approaches.

Elevated serum levels of HIF-1α and VEGF as potential biomarkers in connective tissue disease-associated pulmonary arterial hypertension

We to measure the serum levels of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) in patients diagnosed with connective tissue disease (CTD)-associated pulmonary arterial hypertension (PAH) (CTD-PAH) and to analyze their clinical implications. Thirty patients who were diagnosed with CTD-PAH via right heart catheterization (RHC) were enrolled in the observation group. Additionally, twenty CTD patients without PAH (CTD-non-PAH) were enrolled in the CTD-non-PAH group, and twenty healthy participants were enrolled in the healthy control group. Additional data on CTD-PAH patients, including demographic characteristics, laboratory parameters, and hemodynamic measurements, were obtained. The serum levels of HIF-1α and VEGF in all participants were measured using an enzyme-linked immunosorbent assay (ELISA). Pearson correlation was utilized to determine the correlation between the expression levels of these factors and clinical data. Receiver operating characteristic (ROC) curves were constructed, and the area under the curve (AUC) was calculated to evaluate the diagnostic efficacy of expression of HIF-1α and VEGF for diagnosing CTD-PAH. Participants in the three groups were age-matched. The CTD-PAH group included 29 females and 1 male, and systemic lupus erythematosus (SLE) was the most prevalent CTD diagnosis (17/30). Serum levels of VEGF and HIF-1α were significantly greater in both CTD-PAH and CTD-non-PAH patients compared to the healthy controls (P < 0.01). In addition, the serum concentration of HIF-1α in the CTD-PAH group was significantly greater than that in the CTD-non-PAH group (248.86 ± 18.85 and 224.64 ± 12.22, respectively, P = 0.0022). Similarly, the serum concentration of VEGF in the CTD-PAH group was significantly greater than that in the CTD-non-PAH group (251.11 ± 48.37 and 222.120 ± 18.57, respectively, P = 0.0026). In patients with CTD-PAH, the concentrations of HIF-1α and VEGF are significantly positively correlated with mPAP (r = 0.81, r = 0.88). Both HIF-1α and VEGF concentrations were positively correlated with BNP levels (r = 0.5340, r = 0.6472) and negatively correlated with the 6-Minute Walk Distance (6MWD) (r=-0.46, r=-0.47, respectively, P < 0.01). When VEGF and HIF-1α were combined, the diagnostic ROC curve yielded an AUC of 0.933. Increased serum levels of HIF-1α and VEGF were observed in CTD-PAH patients compared to CTD-non-PAH patients and healthy controls, which, along with their positive correlations with mPAP and BNP levels and negative correlations with the 6MWD, indicate their potential as biomarkers for diagnosing CTD-PAH.

Comparative transcriptomic analysis validates iPSC derived in-vitro progressive fibrosis model as a screening tool for drug discovery and development in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by vasculopathy, immune dysregulation, and systemic fibrosis. Research on SSc has been hindered largely by lack of relevant models to study the progressive nature of the disease and to recapitulate the cell plasticity that is observed in this disease context. Generation of models for fibrotic disease using pluripotent stem cells is important for recapitulating the heterogeneity of the fibrotic tissue and are a potential platform for screening anti-fibrotic drugs. We previously reported a novel in-vitro model for fibrosis using induced pluripotent stem cell-derived mesenchymal cells (iSCAR). Here we report the generation of a "scar-like phenotype" when iPSC derived mesenchymal cells are cultured on hydrogel that mimicks a wound healing/scarring response (iSCAR). First, we performed RNA sequencing (RNA-seq) based transcriptome profiling of iSCAR culture at 48 h and 13 days to characterize early and latestage scarring phenotypes. The next generation RNA-seq of these iSCAR culture at different timepoints detected expression 92% of early "scar associated" genes and 85% late "scar associated" genes, respectively. Comparative transcriptomic analysis of a gene level SSc compendium matrix to the iSCAR wound associated model revealed genes common in both data sets. Early scar formation genes showed biological processes of hypoxia (27.5%), vascular development (13.7%) and glycolysis (27.5), while late scar formation showed genes associated with senescence (22.6%). Next we show the effects of two different antifibrotic compounds to validate the utility of the model as a screening tool to study early and late-stagelate-stage fibrosis. An autotaxin inhibitor was used to validate the iSCAR late stage fibrotic model (iSCAR-T) and an antifibrotic tool screening compound of unknown mechanism (EX00015097) was used to study and validate both early (iSCAR-P) and late-stage (iSCAR-T) fibrosis in the iSCAR model.

Systemic Sclerosis-Associated Pulmonary Arterial Hypertension: From Bedside to Bench and Back Again

Systemic sclerosis (SSc) is a heterogeneous disease characterized by autoimmunity, vasculopathy, and fibrosis which affects the skin and internal organs. One key aspect of SSc vasculopathy is pulmonary arterial hypertension (SSc-PAH) which represents a leading cause of morbidity and mortality in patients with SSc. The pathogenesis of pulmonary hypertension is complex, with multiple vascular cell types, inflammation, and intracellular signaling pathways contributing to vascular pathology and remodeling. In this review, we focus on shared molecular features of pulmonary hypertension and those which make SSc-PAH a unique entity. We highlight advances in the understanding of the clinical and translational science pertinent to this disease. We first review clinical presentations and phenotypes, pathology, and novel biomarkers, and then highlight relevant animal models, key cellular and molecular pathways in pathogenesis, and explore emerging treatment strategies in SSc-PAH.

Cholesterol Exacerbates the Pathophysiology of Non-Alcoholic Steatohepatitis by Upregulating Hypoxia-Inducible Factor 1 and Modulating Microcirculatory Dysfunction

Cholesterol is a pivotal lipotoxic molecule that contributes to the progression of Non-Alcoholic Steatohepatitis NASH). Additionally, microcirculatory changes are critical components of Non-Alcoholic Fatty Liver Disease (NAFLD) pathogenesis. This study aimed to investigate the role of cholesterol as an insult that modulates microcirculatory damage in NAFLD and the underlying mechanisms. The experimental model was established in male C57BL/6 mice fed a high-fat high-carbohydrate (HFHC) diet for 39 weeks. Between weeks 31-39, 2% cholesterol was added to the HFHC diet in a subgroup of mice. Leukocyte recruitment and hepatic stellate cells (HSC) activation in microcirculation were assessed using intravital microscopy. The hepatic microvascular blood flow (HMBF) was measured using laser speckle flowmetry. High cholesterol levels exacerbated hepatomegaly, hepatic steatosis, inflammation, fibrosis, and leukocyte recruitment compared to the HFHC group. In addition, cholesterol decreased the HMBF-cholesterol-induced activation of HSC and increased HIF1A expression in the liver. Furthermore, cholesterol promoted a pro-inflammatory cytokine profile with a Th1-type immune response (IFN-γ/IL-4). These findings suggest cholesterol exacerbates NAFLD progression through microcirculatory dysfunction and HIF1A upregulation through hypoxia and inflammation. This study highlights the importance of cholesterol-induced lipotoxicity, which causes microcirculatory dysfunction associated with NAFLD pathology, thus reinforcing the potential of lipotoxicity and microcirculation as therapeutic targets for NAFLD.

Lymphatic Endothelial-to-Myofibroblast Transition: A Potential New Mechanism Underlying Skin Fibrosis in Systemic Sclerosis

At present, only a few reports have addressed the possible contribution of the lymphatic vascular system to the pathogenesis of systemic sclerosis (SSc). Based on the evidence that blood vascular endothelial cells can undertake the endothelial-to-myofibroblast transition (EndMT) contributing to SSc-related skin fibrosis, we herein investigated whether the lymphatic endothelium might represent an additional source of profibrotic myofibroblasts through a lymphatic EndMT (Ly-EndMT) process. Skin sections from patients with SSc and healthy donors were immunostained for the lymphatic endothelial cell-specific marker lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1) in combination with α-smooth muscle actin (α-SMA) as the main marker of myofibroblasts. Commercial human adult dermal lymphatic microvascular endothelial cells (HdLy-MVECs) were challenged with recombinant human transforming growth factor-β1 (TGFβ1) or serum from SSc patients and healthy donors. The expression of lymphatic endothelial cell/myofibroblast markers was measured by quantitative real-time PCR, Western blotting and immunofluorescence. Collagen gel contraction assay was performed to assess myofibroblast-like cell contractile ability. Lymphatic endothelial cells in intermediate stages of the Ly-EndMT process (i.e., coexpressing LYVE-1 and α-SMA) were found exclusively in the fibrotic skin of SSc patients. The culturing of HdLy-MVECs with SSc serum or profibrotic TGFβ1 led to the acquisition of a myofibroblast-like morphofunctional phenotype, as well as the downregulation of lymphatic endothelial cell-specific markers and the parallel upregulation of myofibroblast markers. In SSc, the Ly-EndMT might represent a previously overlooked pathogenetic process bridging peripheral microlymphatic dysfunction and skin fibrosis development.