Histochemical analysis of extracellular matrix material during embryonic mouse lens morphogenesis in an aphakic strain of mice

Extracellular matrix material (ECM) present during early lens morphogenesis was analyzed histochemically in normal CFW mice and mutant strain aphakia by the Alcian blue 8GX, pH 2.5, Alcian blue 8GX, pH 2.5/periodic acid-Schiff combined, high-iron diamine, and van Gieson methods. At lens placode formation, the optic vesicle basal lamina in both strains was higher in sulfated glycosaminoglycan content than was the ectodermal basal lamina. In the aphakia strain, ECM components were observed intercellularly in the presumptive neural retina and lens rudiment of some specimens. This observation was peculiar to the aphakia strain. At the lens cup stage (10.5 days), the interface ECM became less uniformly dense in the CFW strain, resulting in the formation of a fibrillar structure in the widening interspace area. In contrast, the interface ECM in the mutant strain stained solidly and continuously for acidic materials, particularly sulfated glycosaminoglycans, for a full 2 days longer than in the normal strain. The optic cup and lens rudiment remained closely apposed and intercellular ECM components were observed in these tissues in most mutant specimens throughout these stages. The exact mechanism resulting in these intercellular deposits is unknown, although it is possible that they are either pulled along on the cell surface away from the interface ECM during cell shape changes related to the cell cycle or that they are secreted abnormally due to some disturbed cellular polarity. It is unclear at this time if these abnormalities of the ECM in the aphakia strain play a role in the pathogenesis of the multiple eye anomalies, or if they are a secondary effect of the gene mutation.