The experimental production of Renaut bodies.

Renaut bodies are loosely-textured whorled, cell-sparse structures found in the subperineurial space of peripheral nerves. Although described in 1881, their significance is still debated. Rats were placed in wire-mesh cages for 4 days to 6 weeks and the lateral and medial plantar nerves were sequentially removed. The initial change was the presence of endoneurial edema which dissected and displaced nerve fibers producing an endoneurial cleft. With the influx of fibroblasts, these clefts became discretely separated by circumferentially oriented processes. Over time the clefts enlarged and became filled with loosely-textured amorphous and fibrillar material as well as collagen. The Renaut bodies ranged from 15 to 80 microns in diameter. In this model the Renaut bodies formed at the maximum site of compression of the lateral plantar nerve. The fibroblasts appeared to be derived from the endoneurial connective tissue and were not the result of degenerating endoneurial structures. Renaut body formation was independent of axonal degeneration. The present study strongly suggests that Renaut bodies are a response to repeated mechanical stress.