The extracellular matrix of peripheral nerve in diabetic polyneuropathy

The pattern of collagenisation in peripheral nerve in diabetic polyneuropat hy was examined in nerve biopsy specimens from patients with diabetic polyn europathy in comparison with organ donor control nerves and disease control s (other neuropathies). There was increased endoneurial collagenisation bot h in the diabetic polyneuropathy cases and the disease controls, this predo minantly involving types I and III. Type II collagen was not detected in or gan donor control nerves or in the diabetic and the disease control nerves. There was a relative increase in type VI collagen in the endoneurium in th e diabetic nerves immediately surrounding groups of Schwann cells. This was not a feature in the other neuropathies. The quantity of types IV, V and V I collagen was increased around the endoneurial microvessels in the diabeti c patients and, to a lesser extent, in those with hereditary motor and sens ory neuropathy (HMSN). Increased deposition of types IV and V collagen was observed in the perineurium in the diabetic nerves, the latter being most e vident in the innermost lamellae where the amount of laminin was possibly a lso increased. The diameter of the general endoneurial collagen fibrils was greater in the diabetic nerves, although this was not more than in a disea se control (HMSN). The collagen fibrils that were present within the basal laminal tubes that had surrounded degenerated myelinated fibres in the diab etic nerves, and those within the onion bulbs of the HMSN cases, were of th e normal endoneurial calibre. The expression of laminin by Bungner bands in diabetic neuropathy did not differ from that in disease control nerves, no r were any differences detected for fibronectin. Whether the changes observ ed are important for the impaired regenerative capacity in diabetic neuropa thy requires further investigation.