Figure 3.

Endoneurial blood vessel structure is altered by traumatic nerve injury causing painful peripheral neuropathy. A, Toluidine blue staining of uninjured contralateral nerve shows that endoneurial blood vessels are small and capillary like. B, After PSNL, blood vessels proximal to the nerve injury site look similar to those in uninjured nerves. C, Distal to the nerve injury site, abnormally sized blood vessels with unusually large lumens are observed. High-magnification photographs of blood vessels in uninjured contralateral nerve (D) and proximal to the nerve injury site (E) demonstrate that endoneurial blood vessels are thin and small. F, High-magnification photographs of endoneurial blood vessels distal to the injury site show enlarged blood vessels, some of which have multiple endothelial cell bodies observable within cross-sections. The cell bodies of the endothelial cells were hypertrophic. G, Lumen sizes of blood vessels were measured in uninjured nerve and distal injured nerve. A histogram of data collected from five contralateral and five distal ipsilateral nerves is shown and clearly demonstrates an altered distribution in blood vessel luminal areas after nerve injury. H, Average luminal area of ipsilateral nerves was significantly increased when compared with contralateral nerve (n = 5 per group; *p < 0.05). I, Electron microscopy of endoneurial capillaries in contralateral uninjured nerve demonstrates that microvessels have a thin basal lamina. The interfaces of the basal lamina are denoted with red arrows. J, Electron microscopy of endoneurial capillaries distal to the injury site demonstrate that blood vessels have a thickened basal lamina, as denoted by the red arrows. K, Intravenously injected FITC–dextran can be used to examine the functionality of blood vessels within the endoneurium. L, The large vascular structures are filled with FITC–dextran, demonstrating that they are functional blood vessels.