Characterization of the microvascular glycocalyx in normal and injured spinal cord in the rat

Abstract

The glycocalyx of microvasculature in normal and injured spinal cord was characterized by using cationized ferritin to define anionic sites and the lectins concanavalin agglutinin (Con A) and Ricinus communis agglutinin I (RCA) to delineate carbohydrate moities. Binding of cationized ferritin was evaluated at the ultrastructural level in control animals and at 3 hours after spinal cord injury. Horseradish peroxidase (HRP) was administered intravenously before euthanasia. In control spinal cord, there was continuous even binding of cationized ferritin along the luminal front of microvasculature and no evidence of barrier permeability to HRP. After spinal cord injury, there was a reduction in binding of cationized ferritin in those regions of spinal cord that exhibited barrier breakdown to HRP. Lectin binding in the spinal cord was evaluated at 3 hours and 3 days postinjury. At the light microscopic level, there appeared to be increased binding of Con A and RCA in microvessels by 3 days postinjury as compared with the control spinal cord. At the ultrastructural level, a significant increase in RCA binding was noted along luminal fronts in the injured spinal cord. This increased binding coincided with a significant elaboration of the endothelial glycocalyx. These findings demonstrate that the charge, structure, and carbohydrate composition of the endothelial glycocalyx in microvessels in the spinal cord may be dramatically altered after spinal cord injury. Furthermore, there is an association between the loss of charge and disruption of the barrier, suggesting that anionic sites may contribute to maintenance of the blood-spinal cord barrier.

Vascular Pathology as a Potential Therapeutic Target in SCI

“…Even if ECs survive or become angiogenic, such as happens in the penumbra, BSCB dysfunction is present, and contributes to secondary degeneration (bottom right). Recent experimental efforts have started to gain traction on therapeutically targeting these pathological events perturbation of the integrity and charge of the glycocalyx in microvessels affected in acute SCI was correlated with increased extravasation of blood products [111], demonstrating the critical role of the negatively charged glycocalyx in the maintenance of the BScB. This result was more recently corroborated in our own laboratories.…”

“…As early as 1911, Alfred Allen showed rapid degenerative changes in the epicenter vasculature after a contusive injury in dogs [2,3]. Many others followed (e.g., [9,27,38,83,95,111,152,162]), helping to develop the insight that ECs detach from their basement membrane and show degenerative changes as early as 15 min following injury. This is followed by a largely necrotic and oncotic form of cell death of many ECs and development of pathological permeability in the surviving blood vessels [26,114,139].…”

The endothelial surface layer

“…Similar results were obtained in vivo: in a discordant cardiac xenograft model, about 50% of the glycosaminoglycans were lost in the first 5 min after reperfusion, and interventions that inhibited loss of heparan sulfate also prolonged the survival of the xenografts [105]. It was also shown for the spinal cord [70] that changes in the charge, structure and composition of the glycocalyx may be elicited by tissue trauma. These changes were accompanied by a partial loss of the blood-spinal cord barrier and may thus lead to aggravation of the tissue damage.…”

Spinal Cord Injury

“…The restrictive nature of the barrier is mainly attributed to a complex negatively charged glycocalyx, able to repulse circulating proteins. 22 SCI triggers microvascular damage involving endothelial cell death and breakdown of the blood-brain/spinal cord barrier. The primary insult causes hemorrhage starting from the center of the injury and spreading to both the gray and white matter.…”