Understanding COVID-19-associated coagulopathy

COVID-19-associated coagulopathy (CAC) is a life-threatening complication of SARS-CoV-2 infection. However, the underlying cellular and molecular mechanisms driving this condition are unclear. Evidence supports the concept that CAC involves complex interactions between the innate immune response, the coagulation and fibrinolytic pathways, and the vascular endothelium, resulting in a procoagulant condition. Understanding of the pathogenesis of this condition at the genomic, molecular and cellular levels is needed in order to mitigate thrombosis formation in at-risk patients. In this Perspective, we categorize our current understanding of CAC into three main pathological mechanisms: first, vascular endothelial cell dysfunction; second, a hyper-inflammatory immune response; and last, hypercoagulability. Furthermore, we pose key questions and identify research gaps that need to be addressed to better understand CAC, facilitate improved diagnostics and aid in therapeutic development. Finally, we consider the suitability of different animal models to study CAC

Platelet necrosis mediates ischemic stroke outcome in mice

Dysregulated platelet functions contribute to the development and progression of ischemic stroke. Utilizing mice with a platelet-specific deletion of cyclophilin D (CypD), a mediator of necrosis, we found that platelet necrosis regulates tissue damage and outcomes during ischemic stroke in vivo. Mice with loss of CypD in platelets (CypD(plt−/−)mice) exhibited significantly enhanced cerebral blood flow, improved neurological and motor functions, and reduced ischemic stroke infarct volume after cerebral ischemia-reperfusion injury. These effects were attributable, at least in part, to platelet-neutrophil interactions. Twenty-four hours after stroke, significantly more circulating platelet-neutrophil aggregates (PNAs) were found in CypD(plt+/+) mice. Underscoring the role of platelet necrosis in PNA formation, we observed a significant number of phosphatidylserine (PS)⁺ platelets in PNAs in CypD(plt+/+) mice. In contrast, significantly fewer platelets in PNAs were PS+ in CypD(plt−/−) counterparts. Accordingly, mice with CypD-deficient platelets had fewer neutrophils and PNAs recruited to their brain following stroke relative to wild-type counterparts. Neutrophil depletion in wild-type mice conferred protection from ischemic stroke to a similar degree as observed in mice with CypD-deficient platelets. Neutrophil depletion in CypD(plt−/−) mice did not further reduce infarct size. Transmission electron microscopy of ex vivo–formed PNAs revealed a propensity of necrotic platelets to interact with neutrophils. These results suggest that necrotic platelets interact with neutrophils to exacerbate brain injury during ischemic stroke. Because inhibiting platelet necrosis does not compromise hemostasis, targeting platelet CypD may be a potential therapeutic strategy to limit brain damage following ischemic stroke.Frederik Denorme, Bhanu Kanth Manne, Irina Portier, Alicia S. Eustes, Yasuhiro Kosaka, Benjamin T. Kile, Matthew T. Rondina, and Robert A. Campbel

Reproductive responses and progesterone levels of postpartum oestrus synchronization in goats with different body reserves

Thirty adult goats were classified at parturition into two body condition score (BCS) groups: BCI (n=16) with a score of 2.7 and BCII (n=14) with a score of 2.0. On the fiftieth day <em>postpartum</em>, oestrus was synchronized by CIDR for 5 days. Upon CIDR removal (Day 0), they received 1 mL of PGF2α IM and mated for 72 hours. Kids were kept with does and weaned at 40 days of age. Blood samples were taken at 0, 1, 4, 8 and 21 days after CIDR removal for progesterone assay. The BCI group showed a greater weight loss compared to the BCII group, and BCS before synchronization was 1.9±0.08 and 1.6±0.07 for the BCI and BCII groups, respectively (P<0.05). The weaning weight of BCI kids was greater when compared to BCII (P<0.001). After CIDR removal, all females were marked and mated. Pregnancy rate was higher in BCI goats (87% <em>vs</em> 36%; P<0.05), as well as prolificacy (1.65 <em>vs</em> 1.25; P<0.05) and twinning rate (0.62 <em>vs</em> 0.25; P<0.05). Progesterone concentration was higher in pregnant does in BCI. A positive relationship was found between progesterone level at CIDR removal and BCS at parturition (0.57; P<0.01), also between progesterone level at 21 days after CIDR removal and BCS at parturition (0.47; P<0.05), or BCS before synchronization (0.51; P<0.05). We conclude that oestrus response to postpartum CIDR synchronization appeared to be slightly dependent on BCS. However, goats with low BCS at oestrus synchronization exhibited a reduction in pregnancy rate

Longitudinal RNA-Seq analysis of the reeatability of gene expression and splicing in human platelets identifies a platelet <em>SELP</em> splice QTL.

Rationale:Longitudinal studies are required to distinguish within versus between-individual variation and repeatability of gene expression. They are uniquely positioned to decipher genetic signal from environmental noise, with potential application to gene variant and expression studies. However, longitudinal analyses of gene expression in healthy individuals-especially with regards to alternative splicing-are lacking for most primary cell types, including platelets.Objective:To assess repeatability of gene expression and splicing in platelets and use repeatability to identify novel platelet expression quantitative trait loci (QTLs) and splice QTLs.Methods and Results:We sequenced the transcriptome of platelets isolated repeatedly up to 4 years from healthy individuals. We examined within and between individual variation and repeatability of platelet RNA expression and exon skipping, a readily measured alternative splicing event. We find that platelet gene expression is generally stable between and within-individuals over time-with the exception of a subset of genes enriched for the inflammation gene ontology. We show an enrichment among repeatable genes for associations with heritable traits, including known and novel platelet expression QTLs. Several exon skipping events were also highly repeatable, suggesting heritable patterns of splicing in platelets. One of the most repeatable was exon 14 skipping of SELP. Accordingly, we identify rs6128 as a platelet splice QTL and define an rs6128-dependent association between SELP exon 14 skipping and race. In vitro experiments demonstrate that this single nucleotide variant directly affects exon 14 skipping and changes the ratio of transmembrane versus soluble P-selectin protein production.Conclusions:We conclude that the platelet transcriptome is generally stable over 4 years. We demonstrate the use of repeatability of gene expression and splicing to identify novel platelet expression QTLs and splice QTLs. rs6128 is a platelet splice QTL that alters SELP exon 14 skipping and soluble versus transmembrane P-selectin protein production