Innervation patterns of PGP 9.5-positive nerve fibers within the human lumbar vertebra.

Intervertebral disc injury or degeneration is a common cause of low back pain, and yet the specific source of pain remains ambiguous in many cases. Previous research indicates that the central vertebral endplate is highly innervated and can elicit pain responses to pressure. In effort to trace the origin of nerves located at the endplate, we used protein gene product 9.5 (PGP 9.5) to stain neurofibers and then quantified the spatial pattern of nerve distribution within a human L4 lumbar vertebra. The majority of nerves were adjacent to blood vessel walls, and consequently the nerve distribution closely resembled previously established vascularity patterns. We observed that the majority of nerves enter the vertebral body posteriorly, via the basivertebral foramen, and cluster in the vertebral center. These nerves follow the course of the nutrient artery, which enters the vertebral body through the basivertebral foramen, then branches toward the superior and inferior endplates. Our observations support the notion that nerves found at the central endplate could originate from sinuvertebral nerves accompanying the nutrient artery into the vertebral body. We also stained neighboring histological sections with calcitonin gene-related protein and noted significant co-localization with PGP 9.5, substantiating a nociceptive role for the nerves constituting our distribution pattern.