ZEB1 regulates bone metabolism in osteoporotic rats through inducing POLDIP2 transcription

The decrease in zinc-finger E-box-binding homeobox-1 could accelerate steroid-induced osteonecrosis of the femoral head by repressing type-H vessel formation via Wnt/β-catenin pathway

BACKGROUND

Zinc-finger E-box-binding homeobox-1 (ZEB1) is predominantly found in type-H vessels. However, the roles of ZEB1 and type-H vessels in steroid-induced osteonecrosis of the femoral head (SONFH) are unclear.

METHODS

Human femoral heads were collected to detect the expression of ZEB1 and the levels of type-H vessels. Then, the SONFH model was developed by injecting C57BL/6 mice with lipopolysaccharide and methylprednisolone. Micro-computed tomography, angiography, double calcein labeling, immunofluorescence, immunohistochemistry, quantitative real-time polymerase chain reaction, and Western blotting were performed to detect the expression of ZEB1, the Wnt/β-catenin pathway, type-H vessels, and the extent to which ZEB1 mediates angiogenesis and osteogenesis. Human umbilical vein endothelial cells were also used to explore the relationship between ZEB1 and the Wnt/β-catenin pathway.

RESULTS

We found that ZEB1 expression and the formation of type-H vessels decreased in SONFH patients and in a mouse model. The number of vascular endothelial growth factors in the femoral heads also decreased. Moreover, the bone mineral density, trabecular number, mineral apposition rate, and expression of genes related to osteogenesis decreased. After ZEB1 knockdown, angiogenesis and osteogenesis decreased. However, the numbers of type-H vessels and the extent of angiogenesis and osteogenesis improved after activation of the Wnt/β-catenin pathway.

CONCLUSIONS

The ZEB1 expression decreased in SONFH, causing a decrease in type-H vessel, and it mediated angiogenesis and osteogenesis by regulating the Wnt/β-catenin pathway, ultimately accelerating the process of SONFH.

Homeostatic Regulation of Pro-Angiogenic and Anti-Angiogenic Proteins via Hedgehog, Notch Grid, and Ephrin Signaling in Tibial Dyschondroplasia

Precise coupling of two fundamental mechanisms, chondrogenesis and osteogenesis via angiogenesis, plays a crucial role during rapid proliferation of growth plates, and alteration in their balance might lead to pathogenic conditions. Tibial dyschondroplasia (TD) is characterized by an avascular, non-mineralized, jade-white "cartilaginous wedge" with impaired endochondral ossification and chondrocyte proliferation at the proximal end of a tibial bone in rapidly growing poultry birds. Developing vascular structures are dynamic with cartilage growth and are regulated through homeostatic balance among pro and anti-angiogenic proteins and cytokines. Pro-angiogenic factors involves a wide spectrum of multifactorial mitogens, such as vascular endothelial growth factors (VEGF), platelet-derived growth factors (PDGF), basic fibroblast growth factor (bFGF), placental growth factors, transforming growth factor-β (TGF-β), and TNF-α. Considering their regulatory role via the sonic hedgehog, notch-gridlock, and ephrin-B2/EphB4 pathways and inhibition through anti-angiogenic proteins like angiostatin, endostatin, decoy receptors, vasoinhibin, thrombospondin, PEX, and troponin, their possible role in persisting inflammatory conditions like TD was studied in the current literature review. Balanced apoptosis and angiogenesis are vital for physiological bone growth. Any homeostatic imbalance among apoptotic, angiogenetic, pro-angiogenic, or anti-angiogenic proteins ultimately leads to pathological bone conditions like TD and osteoarthritis. The current review might substantiate solid grounds for developing innovative therapeutics for diseases governed by the disproportion of angiogenesis and anti-angiogenesis proteins.

Genetic Engineered Ultrasound-Triggered Injectable Hydrogels for Promoting Bone Reconstruction

Genetic engineering technology can achieve specific gene therapy for a variety of diseases, but the current strategy still has some flaws, such as a complex system, single treatment, and large implantation trauma. Herein, the genetic engineering injectable hydrogels were constructed by ultrasonic technology for the first time to realize in vivo ultrasound-triggered in situ cross-linking and cell gene transfection, and finally complete in situ gene therapy to promote bone reconstruction. First, ultrasound-triggered calcium release was used to activate transglutaminase and catalyze the transamidation between fibrinogen. Simultaneously, liposome loaded with Zinc-finger E-box-binding homeobox 1 (ZEB1) gene plasmid (Lip-ZEB1) was combined to construct an ultrasound-triggered in situ cross-linked hydrogels that can deliver Lip-ZEB1. Second, ultrasound-triggered injectable hydrogel introduced ZEB1 gene plasmid into endothelial cell genome through Lip-ZEB1 sustained release, and then acted on the ZEB1/Notch signal pathway of cells, promoting angiogenesis and local bone reconstruction of osteoporosis through genetic engineering. Overall, this strategy provides an advanced gene delivery system through genetic engineered ultrasound-triggered injectable hydrogels.

A Zeb1/MtCK1 metabolic axis controls osteoclast activation and skeletal remodeling

Osteoclasts are bone-resorbing polykaryons responsible for skeletal remodeling during health and disease. Coincident with their differentiation from myeloid precursors, osteoclasts undergo extensive transcriptional and metabolic reprogramming in order to acquire the cellular machinery necessary to demineralize bone and digest its interwoven extracellular matrix. While attempting to identify new regulatory molecules critical to bone resorption, we discovered that murine and human osteoclast differentiation is accompanied by the expression of Zeb1, a zinc-finger transcriptional repressor whose role in normal development is most frequently linked to the control of epithelial-mesenchymal programs. However, following targeting, we find that Zeb1 serves as an unexpected regulator of osteoclast energy metabolism. In vivo, Zeb1-null osteoclasts assume a hyperactivated state, markedly decreasing bone density due to excessive resorptive activity. Mechanistically, Zeb1 acts in a rheostat-like fashion to modulate murine and human osteoclast activity by transcriptionally repressing an ATP-buffering enzyme, mitochondrial creatine kinase 1 (MtCK1), thereby controlling the phosphocreatine energy shuttle and mitochondrial respiration. Together, these studies identify a novel Zeb1/MtCK1 axis that exerts metabolic control over bone resorption in vitro and in vivo.