Activation Of HIF-1α Signaling Pathway Research Articles

DLP-printed GelMA-PMAA scaffold for bone regeneration through endochondral ossification.

Intramembranous ossification (IMO) and endochondral ossification (ECO) are two pathways of bone regeneration. The regeneration of most bone, such as limb bone, trunk bone, and skull base bone, mainly occurs in the form of endochondral ossification, which has also become one of the effective ways for bone tissue engineering. In this work, we prepared a well-structured and biocompatible methacrylated gelatin/polymethacrylic acid (GelMA/PMAA) hydrogel by digital light processing (DLP) printing technology, which could effectively chelate iron ions and continuously activate the hypoxia-inducible factor-1 alpha (HIF-1α) signaling pathway to promote the process of endochondral ossification and angiogenesis. The incorporation of PMAA endowed the hydrogel with remarkable viscoelasticity and high efficacy in chelation of iron ions, giving rise to the activation of HIF-1α signaling pathway, improving chondrogenic differentiation in the early stage, and facilitating vascularization in the later stage and bone remodeling. Therefore, the findings have significant implications on DLP printing technology of endochondral osteogenesis induced by the iron-chelating property of biological scaffold, which will provide an effective way in the development of novel bone regeneration.

Activation of Hypoxia-Inducible Factor-1α Signaling Pathway Has the Protective Effect of Intervertebral Disc Degeneration.

Intervertebral discs (IVDs) have poor nutrient diffusion, because the nucleus pulposus (NP) lacks direct vascular supply and likely generates adenosine triphosphate by anaerobic glycolysis. Regulation of glycolysis is mediated by hypoxia-inducible factor-1α (HIF-1α), a transcription factor that responds to local oxygen tension. Constitutively active HIF-1α (CA HIF-1α) was created by point mutation and determined the protective role of HIF-1α in IVD degeneration. Under fluoroscopy, rat caudal IVD segments were stabbed by a needle puncture, and pcDNA3- HIF-1α wild-type (WT) or pcDNA3-CA HIF-1α was transfected into NP cell lines. The constitutive activity of CA HIF-1α was analyzed using a luciferase assay after cell lysis. Next, IVD tissue samples were retrieved from five patients with degenerative lumbar spinal stenosis at the time of surgery, and NP cells were cultured. NP cells were transfected with CA HIF-1α, and relevant gene expression was measured. HIF-1α protein levels in the nucleus were significantly higher, and transcriptional activity was 10.3-fold higher in NP cells with CA HIF-1α than in those with HIF-1α WT. Gene transfer of CA HIF-1α into NP cells enhanced the expression of Glut-1, Glut-3, aggrecan, type II collagen, and Sox9. Moreover, CA HIF-1α reduced the apoptosis of NP cells induced by the Fas ligand. The HIF-1α and collagen 2 expression levels were notably increased in the NP cells of the CA HIF-1α transfected segments in histology and immunohistochemistry study. Collectively, these results suggest that activation of HIF-1α signaling pathway may play a protective role against IVD degeneration and could be used as a future therapeutic agent.

Nestin Promotes Peritoneal Fibrosis by Protecting HIF1-α From Proteasomal Degradation.

BackgroundPeritoneal dialysis (PD) is a treatment for end stage renal disease patients, but it can also cause peritoneal fibrosis. Nestin is known as a neural stem cell marker and it has many functions. The hypoxia induced factor (HIF) signaling pathway can be activated under hypoxia conditions, leading to the overexpression of some angiogenesis related genes. The aim of our study is to demonstrate Nestin’s role in the development of peritoneal fibrosis (PF), and to provide a new target (Nestin) to treat PF.MethodsPD mice models were constructed by an intraperitoneal administration of PDS at 10 ml/100g/d for 4 weeks. Nestin-positive cells were isolated from peritonea of Nestin-GFP mice by flow cytometry. The relationship of Nestin and HIF1-α-VEGFA pathway was detected by Nestin knockdown, Co-immunoprecipitation and immunofluorescence. Also, proteasomal activity was demonstrated by CHX and MG132 application, followed by Western blotting and Co-immunoprecipitation.ResultsIn our experiments, we found that Nestin expression resulted in PF. Also, HIF1-α/VEGFA pathway was activated in PF. Nestin knockdown reduced the level of HIF1-α. Nestin directly bound to HIF1-α and protected HIF1-α from proteasomal degradation. Overexpression of HIF1-α reverts the fibrosis levels in Nestin-knockdown cells. In brief, Nestin inhibited the degradation of HIF1-α by mitigating its ubiquitination level, leading to the activation of HIF1-α signaling pathway, and eventually promoted PF.ConclusionWe found a novel mechanism of PF that Nestin promotes by protecting HIF1-α from proteasomal degradation. Taken together, our key findings highlight a novel mechanism by which the silencing of Nestin hinders HIF1- α -induced PF.

Chromobox Homolog 4 is Positively Correlated to Tumor Growth, Survival and Activation of HIF-1α Signaling in Human Osteosarcoma under Normoxic Condition.

Objectives: The clinical significance and tumorigenesis of Chromobox homolog 4 (CBX4) have been reported in hepatocellular carcinoma. The purpose of this study is to confirm the expression, elucidate the biological function and investigate the potential mechanism of CBX4 in osteosarcoma (OS). Methods: The expression of CBX4 in OS samples and cell lines was measured by RT-PCR and western blot test. Cell cycle, CCK8 and colony-forming assays were used to detect changes of cells growth. Cell apoptosis assay was used to measure cell survival capacity. Trans-well assay was used to test the activities of migration and invasion. The expression of genes regulated by CBX4 was detected by qRT-PCT test. Results: The expression of CBX4 was up-regulated in multiple OS cell lines and clinical samples. Overexpression of CBX4 was correlated with advanced clinical stage, high degree of malignancy and low tumor necrosis rate. Moreover, knockdown of CBX4 resulted in significant inhibition of cell growth and cell survival in OS cells under normoxic condition. In addition, we found that knockdown of CBX4 lead to down-regulating of HIF-1α-targeted genes without changing HIF-1α expression itself. Conclusion: Taken together, CBX4 is up-regulated and has a pro-tumor effect in OS with an activation of HIF-1α signaling pathway under normoxic condition. Therefore, targeting CBX4 may provide a new therapeutic method for OS.