Neuroglial Relationships in the Human Retinal Capillary Network

Abstract

THE investigation described in this paper was designed to throw light on one aspect of the vascular relationships in the human posterior retina; such investigations contribute to the more ambitious attempts to solve the difficult and obscure problem presented by the vascular changes in diabetic retinopathy. New and fruitful ideas on retinal structure, function, and pathology have been put forward in the studies of this serious disorder by Ashton (1959), Bloodworth (1962), and Cogan, Toussaint, andKuwabara (1961). In particular, Cogan has emphasized the important functional relationships of Muller's cells; in the retina these modified astrocytes provide a clear example of the supporting function of neuroglia; their interrelationship with the capillary circulation in glucose metabolism has been shown to be crucial for retinal function.Special interest therefore attaches to detailed studies on the intimate structural relationships of the capillary endothelium in the posterior retina and to regional differences in glial distribution in relation to the capillary networks. In retinal research, the numerous cell types, complex interrelationships, and differences in characteristics from many central nervous cells, make new methods or modifications of standard techniques for nerve tissue of special importance in the determination of glial cell type and relationships and indicate the need for caution in interpretation. Material and MethodsExamination of sample sections was undertaken in a selection of eleven enucleated human eyes to find normal retinae and to determine satisfactory fixation; three of these specimens were suitable for detailed examination for their neurogliavascular relationships. The study was confined to typical capillary areas of the posterior retina by the use of two main methods and their modifications; systematic examination of the whole retina was not attempted. Control sections were provided by reference series of whole normal human retinae at various ages.Fixation was carried out for 2 days and for 10 days in isotonic formol saline (as recommended for central neurons by Cammermeyer) and in formalin ammonium bromide for Cajal's gold sublimate method for astrocytes.Standard Methods (1) Serial sections at 2, were made from paraffin blocks of 4-5 mm.2 pieces of posterior polar retina out to 200 from the nerve head; sections were mounted in aqueous glycerine for phase contrast photomicrography.

The retina’s neurovascular unit: Müller glial sheaths and neuronal contacts

“…In the brain, the endfeet derive from astrocytes (Mathiisen et al, 2010), but in the retina astrocytes are confined to the SVP, where they, together with radial Müller glia, wrap vessels (Albargothy et al, 2023) (Figure 1, S1). In the IVP and DVP, only Müller glia wrap capillaries, as shown in cat (Hollander et al, 1991), tree shrew (Ochs et al, 2000;Reichenbach et al, 1995), and human (Erskine, 1963). Müller cells span nearly the entire depth of the retina, extending fine processes laterally in all synaptic and vascular layers (Figure 1, 2A-D).…”