Comparative histogenesis of Bruch's membrane (complexus basalis)

We documented the comparative histogenesis and timing of development of Bruch's membrane (complexus basalis) in five mammalian models with different lengths of gestation. Retinas with attached choroid from the central posterior pole of the eye were obtained from hamster, vole, rabbit, ferret and cat, from mid-gestation onward until the time at which all components of Bruch's membrane could be detected. The sequence of events in the development of Bruch's membrane was similar among species, however the time of appearance of the components varied. At mid-gestation, the basement membrane of the retinal pigment epithelium (RPE) was present to some degree in all species and microfibrils were developing in the connective tissue space external to the RPE basement membrane. The appearance of an initially scant endothelial basement membrane around the choriocapillaries occurred on post-natal (P) day 1 (P1) in hamster, pre-natal (E) day 20 (E20) in vole, E16 in rabbit, P2 in ferret, and E48 in cat. Among the microfibrils within the connective tissue space external to the RPE, electron-dense islands presumed to be elastin were detected on P7 in hamster, P9 in vole, E24 in rabbit, P19 in ferret, and P1 in cat. Relative to birth date and eye opening, the components of Bruch's membrane in the ferret were detected at a later date than that of the other species studied. However, relative to the interval from conception to the appearance of the components of Bruch's membrane, the ferret and cat are similar, paralleling their similar intervals from conception to eye opening.