Microfilaments in preretinal membrane cells of proliferative vitreoretinopathy.

Electron microscopy was carried out on 8 preretinal membranes surgically obtained from 8 patients after vitrectomy and on primary culture cell outgrowths from 6 preretinal membranes from 6 patients, with particular attention to the presence of actin. Actin was detected as microfilaments in the cultured cells and in the preretinal membrane cells as well, as confirmed by the arrowhead formation seen after heavy meromyosin treatment. The cultured cells and preretinal membranes were glycerinated, and exposed to ATP and Mg2+. With the ATP treatment the cultured cells were observed to contract, and intracellular microfilaments aggregated and formed contraction bands, which are known to be the product of interaction between actin and myosin. Parts of the preretinal membranes were also observed to contract after treatment; in the cells of the preretinal membranes the contraction bands were observed. It was concluded that the intracellular microfilaments in the cells of the preretinal membranes contain actin capable of contraction, thereby inducing contraction of the membrane which exerts traction on the retina.