Abnormal expression of hemidesmosome-like structures by junctional epidermolysis bullosa keratinocytes in vitro

Hemidesmosomes are frequently rudimentary in junctional epidermolysis bullosa (JEB), and JEB keratinocytes display abnormal attachment to the substrate in culture. Our aim was to determine whether this abnormality reflects defective hemidesmosome synthesis in vitro. Keratinocytes from five JEB patients were cultured under standard conditions. Control cultures, from four healthy males, three patients with dystrophic EB (DEB), and one patient with the simplex variant (EBS), were also examined. Post-confluent cultures were processed for transmission electron microscopy. Hemidesmosome-like structures were counted in electron micrograph montages. The number of hemidesmosome-like structures in JEB cultures (0.97 +/- 0.57, per 10 microns of basal cell membrane) was approximately 17% of the value for normal controls (5.81 +/- 3.08, P less than 0.02). The values for EBS (3.72) and DEB (3.28 +/- 1.44) were not statistically different from normal controls. In addition hemidesmosome-like structures in JEB cultures were morphologically ill-defined, compared with those from controls. This correlated with the loose apposition between JEB keratinocytes and the substrate, which appeared tight in controls. JEB keratinocytes continue to express in vitro a major phenotypic abnormality which characterizes the disease in vivo. Therefore, this model should prove useful in studies determining the pathogenesis and possible new treatments of JEB.