Mechanisms and timing of injury to the thoracic, lumbar and sacral spine in simulated underbody blast PMHS impact tests.

During an underbody blast (UBB) event, mounted occupants are exposed to high rate loading of the spine via the pelvis. The objective of this study was to simulate UBB loading conditions and examine mechanisms of injury in the thoracic, lumbar and sacral spine. Fourteen instrumented, whole-body, postmortem human subject (PMHS) experiments were performed using the WSU-decelerative horizontal sled system. The specimens were positioned supine on a decelerative sled, which then impacted an energy absorbing system mounted to a concrete barrier. Variables included the peak velocity and time-to-peak velocity for seat and floor, and the presence or absence of personal protective equipment (PPE) and seat padding. Post-test CT scans and autopsies were performed to identify the presence and severity of injuries. Acceleration and angular rate data collected at vertebra T1, T5, T8, T12, and S1 were used to assess injury timing and mechanisms. Additionally, joint time-frequency analysis (JTFA) of the spinal Z acceleration of the sacrum and vertebrae was developed with the aim of verifying spinal fracture timing. Injuries observed in the spine were attributed to axial compression applied through the pelvis, together with flexion moment due to the offset in the center of gravity of the torso, and are consistent with UBB-induced combat injuries reported in the literature. The injury timing estimation techniques discussed in this study provide a time interval when the fractures are predicted to have occurred. Furthermore, this approach serves as an alternative to the estimation methods using acoustic sensors, force and acceleration traces, and strain gauges.

Transcriptome analysis of psoriasis in a large case-control sample: RNA-seq provides insights into disease mechanisms.

To increase our understanding of psoriasis, we used high-throughput complementary DNA sequencing (RNA-seq) to assay the transcriptomes of lesional psoriatic and normal skin. We sequenced polyadenylated RNA-derived complementary DNAs from 92 psoriatic and 82 normal punch biopsies, generating an average of ∼38 million single-end 80-bp reads per sample. Comparison of 42 samples examined by both RNA-seq and microarray revealed marked differences in sensitivity, with transcripts identified only by RNA-seq having much lower expression than those also identified by microarray. RNA-seq identified many more differentially expressed transcripts enriched in immune system processes. Weighted gene coexpression network analysis (WGCNA) revealed multiple modules of coordinately expressed epidermal differentiation genes, overlapping significantly with genes regulated by the long noncoding RNA TINCR, its target gene, staufen-1 (STAU1), the p63 target gene ZNF750, and its target KLF4. Other coordinately expressed modules were enriched for lymphoid and/or myeloid signature transcripts and genes induced by IL-17 in keratinocytes. Dermally expressed genes were significantly downregulated in psoriatic biopsies, most likely because of expansion of the epidermal compartment. These results show the power of WGCNA to elucidate gene regulatory circuits in psoriasis, and emphasize the influence of tissue architecture in both differential expression and coexpression analysis.

Alteration of the EphA2/Ephrin-A signaling axis in psoriatic epidermis.

EphA2 is a receptor tyrosine kinase (RTK) that triggers keratinocyte differentiation upon activation and subsequent downregulation by ephrin-A1 ligand. The objective of this study was to determine whether the EphA2/ephrin-A1 signaling axis was altered in psoriasis, an inflammatory skin condition in which keratinocyte differentiation is abnormal. Microarray analysis of skin biopsies from psoriasis patients revealed increased mRNA transcripts for several members of this RTK family in plaques, including the EphA1, EphA2, and EphA4 subtypes prominently expressed by keratinocytes. Of these, EphA2 showed the greatest upregulation, a finding that was confirmed by quantitative reverse-transcriptase-PCR, immunohistochemistry (IHC), and ELISA. In contrast, psoriatic lesions exhibited reduced ephrin-A ligand immunoreactivity. Exposure of primary keratinocytes induced to differentiate in high calcium or a three-dimensional (3D) raft culture of human epidermis to a combination of growth factors and cytokines elevated in psoriasis increased EphA2 mRNA and protein expression while inducing S100A7 and disrupting differentiation. Pharmacological delivery of a soluble ephrin-A1 peptidomimetic ligand led to a reduction in EphA2 expression and ameliorated proliferation and differentiation in raft cultures exposed to EGF and IL-1α. These findings suggest that ephrin-A1-mediated downregulation of EphA2 supports keratinocyte differentiation in the context of cytokine perturbation.

Evidence for altered Wnt signaling in psoriatic skin.

The Wnt gene family encodes a set of highly conserved secreted signaling proteins that have major roles in embryogenesis and tissue homeostasis. Yet the expression of this family of important mediators in psoriasis, a disease characterized by marked changes in keratinocyte growth and differentiation, is incompletely understood. We subjected 58 paired biopsies from lesional and uninvolved psoriatic skin and 64 biopsies from normal skin to global gene expression profiling. WNT5A transcripts were upregulated fivefold in lesional skin, accompanied by increased Wnt-5a protein levels. Notably, WNT5A mRNA was markedly induced by IL-1alpha, tumor necrosis factor-alpha, IFN-gamma, and transforming growth factor-alpha in cultured keratinocytes. Frizzled 2 (FZD2) and FZD5, which encode receptors for Wnt5A, were also increased in lesional psoriatic skin. In contrast, expression of WIF1 mRNA, encoding a secreted antagonist of the Wnt proteins, was downregulated >10-fold in lesional skin, along with decreased WNT inhibitory factor (WIF)-1 immunostaining. Interestingly, pathway analysis along with reduced AXIN2 expression and lack of nuclear translocation of beta-catenin indicated a suppression of canonical Wnt signaling in lesional skin. The results of our study suggest a shift away from canonical Wnt signaling toward noncanonical pathways driven by interactions between Wnt-5a and its cognate receptors in psoriasis, accompanied by impaired homeostatic inhibition of Wnt signaling by WIF-1 and dickkopf.