A new model of spinal cord injury by cryoapplication:Morphodynamics of histological changes of the spinal cord lesion

Up to 500,000 people worldwide suffer from spinal cord injuries (SCI) annually, according to the WHO. Animal models are essential for searching novel methodological guidelines and therapeutic agents for SCI treatment. We developed an original model of posttraumatic spinal cord glial scar in rats using cryoapplication. The method is based on cryodestruction of spinal cord tissue with liquid nitrogen. Thirty six male SD linear rats of SPF category were included in this experimental study. A T13 unilateral hemilaminectomy was performed with an operating microscope, as it was extremely important not to penetrate the dura mater, and liquid nitrogen was applied into the bone defect for one minute. The animals were euthanized at various intervals ranging from 1 to 60 days after inducing cryogenic trauma, their Th12-L1 vertebrae were removed "en bloc" and the segment of the spinal cord exposed to the cryoapplicator was carefully separated for histological examination. The study results demonstrated that cryoapplication of liquid nitrogen, provoking a local temperature of approximately minus 20{degrees}C, produced a highly standardized transmural defect which extended throughout the dorsoventral arrangement of the spinal cord and had an "hour-glass" shape. During the entire study period (1-60 post-injury days), the glial scarring process and the spinal cord defect were located within the surgically approached vertebral space (Th13). Unlike other available experimental models of SCI (compression, contusion, chemical, etc.), the present option is characterized by a minimal invasiveness (the hemilaminectomy is less than 1 mm wide), high precision and consistency. Also, there was a low interanimal variability in histological lesions and dimensions of the produced defect. The original design of cryoapplicator used in the study played a major role in achieving these results. The original technique of high-precision cryoapplication for inducing consistent morphodynamic glial scarring could facilitate a better understanding of the self-recovery processes of injured spinal cord and would be helpful for proposing new platforms for the development of therapeutic strategies.