Expression of Lymphatic Markers in the Adult Rat Spinal Cord

Frontiers in Cellular Neuroscience, 2016 · DOI: 10.3389/fncel.2016.00023 · Published: February 9, 2016

Simple Explanation

This study investigates the presence of cells expressing lymphatic markers within the spinal cord of rats using immunohistochemistry. The researchers looked for the co-expression of lymphatic markers PROX1 and LYVE-1 with cell type markers like Iba1, CD68, PGP9.5, and OLIG2. The study found PROX1-immunoreactivity in many nuclei throughout the spinal cord, while LYVE-1 expression was mainly detected in cells at the spinal cord surface and those near blood vessels, co-expressing Iba1, a macrophage and microglia marker. Following spinal cord injury, LYVE-1-expressing cells were observed to assemble and reorganize into what appeared to be pre-vessel structures, suggesting a potential lymphatic response to injury.

Study Duration

Not specified

Participants

Female Fisher 344 rats of approximately 3 months of age

Evidence Level

Original Research

Key Findings

1
PROX1-immunoreactivity was detected in numerous nuclei evenly distributed throughout the gray and white matter of the rat adult spinal cord.
2
LYVE-1-expressing cells were found on the surface of the spinal cord and closely located to spinal cord blood vessels, co-localizing with Iba1, suggesting they represent macrophages.
3
Following spinal cord injury, LYVE-1+ cells assembled in structures that were not observed in the unlesioned tissue, resembling putative pre-vessels.

Research Summary

This study challenges the dogma that the CNS is an alymphatic environment by investigating the expression of lymphatic markers LYVE-1 and PROX1 in the adult rat spinal cord. The research identified numerous cells expressing either LYVE-1 or PROX1, but not both together, under physiological conditions, and found that LYVE-1+ cells likely represent a macrophage subpopulation while PROX1+ cells belong to the oligodendrocytic lineage. Following spinal cord injury, the study observed a re-organization and redistribution of LYVE-1-expressing cells within the lesioned parenchyma, forming structures resembling putative pre-vessels, suggesting a potential lymphatic response to injury.

Practical Implications

Understanding Spinal Cord Inflammation

Further research is needed to elucidate the response of LYVE-1+ and PROX1+ cell subpopulations to pathological conditions, especially in spinal cord inflammatory conditions.

Rethinking CNS Lymphatics

The findings contribute to a growing body of evidence that challenges the traditional view of the CNS as an alymphatic environment, opening new avenues for understanding immune responses and drainage in the spinal cord.

Targeting Macrophages after SCI

The identification of a LYVE-1+ macrophage subpopulation and its reorganization following spinal cord injury suggests potential therapeutic targets for modulating the inflammatory response and promoting tissue repair.

Study Limitations

1
The study focuses on the rat spinal cord, and findings may not directly translate to humans.
2
The functional roles of the identified LYVE-1+ and PROX1+ cell subpopulations in the spinal cord remain to be fully elucidated.
3
The mechanisms driving the reorganization of LYVE-1+ cells into vessel-like structures after spinal cord injury require further investigation.

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