ABSTRACT
Peripheral neuropathy can be produced by several diseases, the most common of which is diabetes mellitus. Diabetic neuropathy is a degenerative complication of diabetes mellitus. It is a disease reversible with treatment and is characterized by attacks of degeneration of the peripheral nerves alternating with nerve regeneration but its mechanisms remain poorly understood. A variety of mechanisms have been implicated in the pathogenesis and progression of peripheral diabetic neuropathy. The epineurium and the endoneurium of the peripheral nerves contain fibroblasts which form the collagen fibrils. It was recorded that theses fibroblasts showed several structural and morphological changes in different types of nerve injuries and peripheral neuropathy. Was to study the ultrastructural changes in the epineurial and endoneurial fibroblasts in diabetic neuropathy. Twelve albino rats with streptozotocin-induced diabetes and six control rats were used. The sciatic nerves were processed and examined using transmission electron microscope. The epineurial fibroblasts were increased in number and possessed cytoplasmic processes which were in direct contact with each other and with the epineurial mast cells stimulating these cells to release their granules with increased epineurial vascular permeability and macrophage infiltration with the release of cytokines that participate at nerve damage and others that promote nerve regeneration. The epineurial fibroblasts showed interruptions of their membranes indicating the sites of exocytosis of the newly formed collagen fibrils into the epineurium. The endoneurial fibroblasts showed branching cytoplasmic processes which may be used in the phagocytosis of the degenerated myelin in the diabetic nerves and also to separate the newly formed nerve fibers from the endoneurial edema. These fibroblasts also released ciliary neurotropic factor that improves nerve conduction and regeneration. They also showed cytoplasmic vacuoles of different sizes or shapes. Some of these vacuoles contained electron lucent substances suggested to be nerve growth factors to promote regeneration while others contained electron dense membrane suggested to be degenerated myelin. The endoneurial fibroblasts formed several parallel layers in the subperineurial space to separate the nerve fibers from the endoneurial edema. The increase in the epineurial and endoneurial fibroblasts in the diabetic nerves could be beneficial in nerve fibers regeneration