Deciphering The Role And Mechanism Of STAT3 In Skeletal Development

BACKGROUDAutosomal Dominant Hyperimmunoglobulin-E Syndrome(AD-HIES)is a rare genetic disease that is characterized by low immune function and concurrent skeletal dysplasia,including osteoporosis,long bone fractures,Scoliosis and hypermobility of the joints.HIES is associated with heterozygous mutations in the Signal Transducer and Activator of Transcription 3(STAT3)gene.The mechanism of action of Stat3 in skeletal tissues is poorly understood,and so far,the treatment has been limited to symptomatic treatment.Therefore,an in-depth study of the celluar and molecular mechanism of Stat3 in the development and mineralization of bone tissue is important for the clinical diagnosis and treatment of HIES.In this study,a gene knockout mouse model was used to specifically knock out Stat3 in long bone marrow mesenchymal stem cells and osteoblast precursor cells.The celluar and molecular mechanism of Stat3 in HIES was investigated in order to clarify the pathogenesis of HIES-related bone phenotype to provide potential targets for its clinical treatment.OBJECTIVE2.1 Determine the expression pattern of Stat3 in long bones.Use the Cre-LoxP system to construct long bone marrow mesenchymal stem cell-specific Stat3 knockout mice and analyze their phenotypes.2.2 Exploring the cellular and molecular mechanism of fractures led by a loss of function in Stat3.METHODS3.1 Use Prrx1Cre to generate a Stat3 gene knockout mouse in bone marrow mesenchymal stem cells(Prrx1CreStat3fl/fl)In this study,Prrx1Cre transgenic mice were combined with Stat3fl/fl mice,and the Cre-LoxP system was used to establish a bone marrow mesenchymal stem cellspecific Stat3 knockout mouse model(Prrx1CreStat3fl/fl)Whole body bone staining and microCT technology were used to observe the bone phenotype of knockout mice.2.2 Exploring the cellular mechanism of fractures led by a loss of function in Stat3Using in situ hybridization,immunofluorescence staining,histological staining,microCT,qPCR,and western blotting to analyze the functional changes of different cells in bone marrow mesenchymal stem cells and osteoblast precursor cells Stat3 knockout mice.RESULTSAfter knocking out BMSCs with Stat3 using Prrx1Cre,mice developed a limb fracture phenotype.Fractures may be due to increased apoptosis in the bone marrow.The loss of Stat3 function in bone marrow mesenchymal stem cells affects osteoblast differentiation and matrix mineralization,while the number and activity of osteoclasts increase,but chondrocyte proliferation is not affected.Specific knockout Stat3 in osteoblast precursor cells can phenocopy the fracture phenotype.CONCLUSIONStat3 plays a vital role in skeletal development.The loss of function of Stat3 is the cause of skeletal system symptoms in HIES patients.