Neuroplasticity and regeneration after spinal cord injury

Spinal cord injury (SCI) is a debilitating condition with significant personal, societal, and economic burden. The highest proportion of traumatic injuries occur at the cervical level, which results in severe sensorimotor and autonomic deficits. Following the initial physical damage associated with traumatic injuries, secondary pro-inflammatory, excitotoxic, and ischemic cascades are initiated further contributing to neuronal and glial cell death. Additionally, emerging evidence has begun to reveal that spinal interneurons undergo subtype specific neuroplastic circuit rearrangements in the weeks to months following SCI, contributing to or hindering functional recovery. The current therapeutic guidelines and standards of care for SCI patients include early surgery, hemodynamic regulation, and rehabilitation. Additionally, preclinical work and ongoing clinical trials have begun exploring neuroregenerative strategies utilizing endogenous neural stem/progenitor cells, stem cell transplantation, combinatorial approaches, and direct cell reprogramming. This review will focus on emerging cellular and noncellular regenerative therapies with an overview of the current available strategies, the role of interneurons in plasticity, and the exciting research avenues enhancing tissue repair following SCI.

Endothelial ACKR1 is induced by neutrophil contact and down-regulated by secretion in extracellular vesicles

Atypical chemokine receptor-1 (ACKR1), previously known as the Duffy antigen receptor for chemokines, is a widely conserved cell surface protein that is expressed on erythrocytes and the endothelium of post-capillary venules. In addition to being the receptor for the parasite causing malaria, ACKR1 has been postulated to regulate innate immunity by displaying and trafficking chemokines. Intriguingly, a common mutation in its promoter leads to loss of the erythrocyte protein but leaves endothelial expression unaffected. Study of endothelial ACKR1 has been limited by the rapid down-regulation of both transcript and protein when endothelial cells are extracted and cultured from tissue. Thus, to date the study of endothelial ACKR1 has been limited to heterologous over-expression models or the use of transgenic mice. Here we report that exposure to whole blood induces ACKR1 mRNA and protein expression in cultured primary human lung microvascular endothelial cells. We found that contact with neutrophils is required for this effect. We show that NF-κB regulates ACKR1 expression and that upon removal of blood, the protein is rapidly secreted by extracellular vesicles. Finally, we confirm that endogenous ACKR1 does not signal upon stimulation with IL-8 or CXCL1. Our observations define a simple method for inducing endogenous endothelial ACKR1 protein that will facilitate further functional studies.