Intervertebral disc degeneration is rescued by TGFβ/BMP signaling modulation in an ex vivo filamin B mouse model

Spondylocarpotarsal syndrome (SCT) is a rare musculoskeletal disorder characterized by short stature and vertebral, carpal, and tarsal fusions resulting from biallelic nonsense mutations in the gene encoding filamin B (FLNB). Utilizing a FLNB knockout mouse, we showed that the vertebral fusions in SCT evolved from intervertebral disc (IVD) degeneration and ossification of the annulus fibrosus (AF), eventually leading to full trabecular bone formation. This resulted from alterations in the TGFβ/BMP signaling pathway that included increased canonical TGFβ and noncanonical BMP signaling. In this study, the role of FLNB in the TGFβ/BMP pathway was elucidated using in vitro, in vivo, and ex vivo treatment methodologies. The data demonstrated that FLNB interacts with inhibitory Smads 6 and 7 (i-Smads) to regulate TGFβ/BMP signaling and that loss of FLNB produces increased TGFβ receptor activity and decreased Smad 1 ubiquitination. Through the use of small molecule inhibitors in an ex vivo spine model, TGFβ/BMP signaling was modulated to design a targeted treatment for SCT and disc degeneration. Inhibition of canonical and noncanonical TGFβ/BMP pathway activity restored Flnb-/- IVD morphology. These most effective improvements resulted from specific inhibition of TGFβ and p38 signaling activation. FLNB acts as a bridge for TGFβ/BMP signaling crosstalk through i-Smads and is key for the critical balance in TGFβ/BMP signaling that maintains the IVD. These findings further our understanding of IVD biology and reveal new molecular targets for disc degeneration as well as congenital vertebral fusion disorders.

Novel short peripheral catheter design for prevention of thrombophlebitis

Essentials Phlebitis is one of the most frequent complications related to short peripheral catheters (SPC). A new SPC design, aimed for minimizing mechanical phlebitis, was tested in vivo in swine. MRI analysis revealed 40% less inflammation with the new SPC design compared to commercial SPC. The results confirm that our SPC biomechanical design approach can minimize phlebitis rates. SUMMARY: Background Short peripheral catheters (SPCs) are the most common intravenous device in today's medical practice. Short peripheral catheter thrombophlebitis (SPCT) occurs in up to 80% of hospitalized patients. Symptoms appear on average 3 days after catheter insertion and can lead to extended hospitalization and increased related costs. Here we introduce a novel SPC, named very short peripheral catheter (VSPC), that was designed to minimize biomechanical irritation and improve blood flow. Objective The goal was to test the performance of the novel catheter in vivo for reduction of thrombophlebitis. Methods Very short peripheral catheter prototypes were inserted into swine ear veins (n = 12). Verification of the catheter conformation in situ and blood perfusion was performed using Echo-Doppler. The SPCT development rate was measured using magnetic resonance imaging (MRI), 4 and 12 days after catheter insertion, and analyzed by means of edema and inflammation intensities. Blind histopathology analysis was performed on the veins postmortem. Clinically available SPC was used as a reference. Results Operation of the VSPC devices did not require any special skills over those used for the clinically available SPC. Echo-Doppler imaging confirmed that in contrast to the traditional SPC, the VSPC avoided contact with the vein wall and allowed better blood perfusion. The MRI analysis revealed 2-fold inflammation and edema rates (~80%) in the veins cannulated with the commercial SPC, whereas rates of only ~40% were seen with the novel VSPC. A similar trend was noticed in the histopathology analysis. Conclusions The results indicate that the novel catheter design significantly reduced SPCT rates and demonstrated proof of concept for our biomechanical approach.

Altered mRNA Splicing, Chondrocyte Gene Expression and Abnormal Skeletal Development due to SF3B4 Mutations in Rodriguez Acrofacial Dysostosis

The acrofacial dysostoses (AFD) are a genetically heterogeneous group of inherited disorders with craniofacial and limb abnormalities. Rodriguez syndrome is a severe, usually perinatal lethal AFD, characterized by severe retrognathia, oligodactyly and lower limb abnormalities. Rodriguez syndrome has been proposed to be a severe form of Nager syndrome, a non-lethal AFD that results from mutations in SF3B4, a component of the U2 small nuclear ribonucleoprotein particle (U2 snRNP). Furthermore, a case with a phenotype intermediate between Rodriguez and Nager syndromes has been shown to have an SF3B4 mutation. We identified heterozygosity for SF3B4 mutations in Rodriguez syndrome, confirming that the phenotype is a dominant disorder that is allelic with Nager syndrome. The mutations led to reduced SF3B4 synthesis and defects in mRNA splicing, primarily exon skipping. The mutations also led to reduced expression in growth plate chondrocytes of target genes, including the DLX5, DLX6, SOX9, and SOX6 transcription factor genes, which are known to be important for skeletal development. These data provide mechanistic insight toward understanding how SF3B4 mutations lead to the skeletal abnormalities observed in the acrofacial dysostoses.

The acrofacial dysostoses (AFD) are inherited disorders with abnormalities of the facial and limb bones. Rodriguez syndrome is a severe type of AFD that is usually lethal in the immediate perinatal period. Rodriguez syndrome has been proposed to be a severe form of Nager syndrome, a non-lethal AFD that results from mutations in SF3B4, a component of mRNA splicing machinery needed for proper maturation of primary transcripts. Furthermore, a case with a phenotype intermediate between Rodriguez and Nager syndromes has been shown to have an SF3B4 mutation. We found that mutations in SF3B4 produce Rodriguez syndrome, further demonstrating that it is allelic with Nager syndrome. The consequences of the mutations include abnormal splicing and reduced expression in growth plate chondrocytes of genes that are important for proper development of the skeleton, providing mechanistic insight toward understanding how SF3B4 mutations lead to the skeletal abnormalities observed in the acrofacial dysostoses.