Antagonism Between PEDF and TGF-β Contributes to Type VI Osteogenesis Imperfecta Bone and Vascular Pathogenesis

Abstract

Osteogenesis imperfecta (OI) is a heterogeneous genetic disorder of bone and connective tissue, also known as brittle bone disease. Null mutations in SERPINF1, which encodes pigment epithelium-derived factor (PEDF), cause severe type VI OI, characterized by accumulation of unmineralized osteoid and a fish-scale pattern of bone lamellae. Although the potent anti-angiogenic activity of PEDF has been extensively studied, the disease mechanism of type VI OI is not well understood. Using Serpinf1 (À/À) mice and primary osteoblasts, we demonstrate that loss of PEDF delays osteoblast maturation as well as extracellular matrix (ECM) mineralization. Barium sulfate perfusion reveals significantly increased vessel density in the tibial periosteum of Serpinf1 (À/À) mouse compared with wildtype littermates. The increased bone vascularization in Serpinf1 (À/À) mice correlated with increased number of CD31(+)/Endomucin(+) endothelial cells, which are involved in the coupling angiogenesis and osteogenesis. Global transcriptome analysis by RNA-Seq of Serpinf1 (À/À) mouse osteoblasts reveals osteogenesis and angiogenesis as the biological processes most impacted by loss of PEDF. Intriguingly, TGF-β signaling is activated in type VI OI cells, and Serpinf1 (À/À) osteoblasts are more sensitive to TGF-β stimulation than wild-type osteoblasts. TGF-β stimulation and PEDF deficiency showed additive effects on transcription suppression of osteogenic markers and stimulation of pro-angiogenic factors. Furthermore, PEDF attenuated TGF-β-induced expression of proangiogenic factors. These data suggest that functional antagonism between PEDF and TGF-β pathways controls osteogenesis and bone vascularization and is implicated in type VI OI pathogenesis. This antagonism may be exploited in developing therapeutics for type VI OI utilizing PEDF and TGF-β antibody.

Impact of Bone Morphogenetic Protein 7 and Prostaglandin receptors on osteoblast healing and organization of collagen

“…After the incubation, the cells were washed twice with distilled water and the stained nodules were captured using the Olympus cell Sens imaging software (Olympus Life Science, Tokyo, Japan). For quantification, 800 μL of 10% acetic acid was added to the stained cells and the plate was incubated for 30 minutes at room temperature with shaking [ 29 ]. The cells were then collected using a cell scraper, transferred into 1.5 mL microcentrifuge tubes, and vortexed vigorously.…”

Emerging Landscape of Osteogenesis Imperfecta Pathogenesis and Therapeutic Approaches

“…Type VI OI is characterized by abnormal bone mineralization and the presence of ichthyosis-like bone buildup in the bone tissue. − Patients with type VII OI are more likely to exhibit short humerus and femurs, brittle bones, and skeletal abnormalities, while those with type VIII OI face significant challenges in bone formation and mineralization. , Type IX may manifest bowed limbs, spinal curvature, and other progressive bone abnormalities. A distinctive characteristic of this subtype is the presence of white sclera, often observed in individuals with type IX. − The exceptionally rare type X presents clinical symptoms such as hydrocephalus, widespread bone loss leading to diminished muscular strength, and thoracic scoliosis …”

“…The TGF–β signaling pathway has been linked to bone mass ,, and fragility , in OI. Inhibiting this pathway using TGF–β inhibitory antibodies has shown promise in enhancing bone mass in OI mice, but more research is needed to assess the safety and effectiveness of these medications.…”

VEGF-C overexpression in kidney progenitor cells is a model of renal lymphangiectasia

“…Cortical vascular density was determined by inverting the segmented images within the cortex boundaries. Representative images were generated as previously shown 32,33 using a heat-map representation of vascular diameter. Vascular Density Quantification.…”