Pericytes Make Spinal Cord Breathless after Injury

Abstract

Traumatic spinal cord injury is a devastating condition that leads to significant neurological deficits and reduced quality of life. Therapeutic interventions after spinal cord lesions are designed to address multiple aspects of the secondary damage. However, the lack of detailed knowledge about the cellular and molecular changes that occur after spinal cord injury restricts the design of effective treatments. Li and colleagues using a rat model of spinal cord injury and in vivo microscopy reveal that pericytes play a key role in the regulation of capillary tone and blood flow in the spinal cord below the site of the lesion. Strikingly, inhibition of specific proteins expressed by pericytes after spinal cord injury diminished hypoxia and improved motor function and locomotion of the injured rats. This work highlights a novel central cellular population that might be pharmacologically targeted in patients with spinal cord trauma. The emerging knowledge from this research may provide new approaches for the treatment of spinal cord injury.

Keywords: blood flow; microenvironment; pericytes; scar; spinal cord injury.

Figure 1.

Pericytes’ role in the control of spinal cord blood flow below the site of injury. Pericytes are present around the spinal cord blood vessels. The study of Li and colleagues now suggests a novel very important function for pericytes after spinal cord injury (Li and others 2017). After the loss of neuron-derived monoamines due to spinal cord injury, there is increased expression of the enzyme aromatic L-amino acid decarboxylase (AADC) and, consequently, trace amines (TAs) synthesis in medullar pericytes. Trace amines can bind to monoamine receptors on pericytes, thus causing capillary constriction and reducing blood flow to ischemic levels.

Figure 2.

Hypotheses about the control of blood flow in the injured spinal cord after the loss of neuron-derived monoamines. Li and colleagues suggest that the increase in trace amine synthesis, due to the presence of AADC and monoamine receptors in pericytes, leads to capillary constriction (Li and others 2017). However, AADC could be expressed in the perivascular region by other cell types, such as macrophages and glial cells. In addition, it is possible that monoamine receptors are expressed by several other cell populations. Pericyte heterogeneity also needs to be taken into account, as other roles have been already suggested for pericytes. It should also be taken into consideration the possible presence of NG2-non-expressing pericytes in the spinal cord.