Murine Sciatic Nerve Model of Perineural Invasion or PNI: Extraction and Processing of Sciatic Nerve to Understand Invasion by Cancer Cells

Cancer cells can move from their site of origin and invade the surrounding nerves in a process called perineural invasion or PNI. PNI is observed in an animal model by injecting cancer cells into a major nerve such as the sciatic nerve, which is then extracted to examine the extent of invasion.

To begin, prep a euthanized mouse previously injected with cancer cells in the prone position. Remove the sutures from the hindlimb - the site of tumor cell injection to expose the sciatic nerve that innervates the hindlimb muscles.

Use scissors to separate the muscles and expose the underlying sciatic nerve. Dissect the nerve ends to isolate it from the body. Now, use a caliper to measure and record the macroscopic extent of cancer cell invasion.

Next, place the dissected nerve in an embedding medium to enable sample preparation at low temperatures. Using a cryostat microtome, cut thin sections of the embedded nerve and place them on a slide. Stain the slide with a hematoxylin-eosin histological stain.

Hematoxylin - a basic dye - stains acidic components like the nuclei, while eosin - an acidic dye - stains basic components like the cytoplasm. Observe the slide under a microscope to measure the length and area of neural invasion.