Abstract
Purpose :
Much of what is known about individual astrocyte morphology in the lamina is based on rodents. Rodents, however, have a glial lamina (GL) without the collagenous beams existing in primates. Our goal was to quantify individual astrocyte morphology of the monkey collagenous lamina cribrosa (CL) and test the hypothesis that astrocyte morphology is different between CL and GL
Methods :
Coronal vibratome sections were obtained through the CL of 7 monkey eyes at 150µm thickness. Gold microcarriers coated in cell membrane dyes were ballistically delivered into sections for Multicolor DiOlistic labeling. Confocal microscopy and second harmonic generation (SHG) imaging were used to visualize dyed astrocytes and collagen beams, respectively. 3D models of 28 dyed CL astrocytes were constructed for automated quantification of morphological features. GL astrocyte morphological features were collected from the literature
Results :
Mean ± SD CL astrocyte branch number, length, thickness, hierarchy, and straightness were 86.5 ± 45.7, 14.0 ± 13.5µm, 2.1 ± 1.4µm, 6.1 ± 3.7, and 0.9 ± 0.1. Sholl analysis of CL astrocyte models revealed higher branching complexity than mouse GL astrocytes, indicated by area under Sholl curves (p < 0.001). Diameter of CL first and second order astrocyte branches was 3.1± 0.15µm (mean ± SEM), significantly thicker than comparable GL astrocyte branches (1.3 ± 0.04μm, p < 0.001). SHG revealed CL astrocytes encircling beams and spanning multiple pores
Conclusions :
CL astrocytes display significant morphological differences from those in the GL. Greater branching complexity in CL astrocytes supports potentially more complex interactions of these astrocytes with retinal ganglion cell axons and blood vessels, resulting in possible functional differences. Low-order branch thickness in healthy CL astrocytes was more similar to that of the thickened astrocyte branches in mouse glaucoma models than healthy mouse controls. The ability of CL astrocytes to span multiple pores and interact with CL beams may result in differences in signaling compared to the GL, in which all astrocytes exist within a single pore-like canal. The implications of these differences should be investigated to better understand astrocyte physiology in the CL and their role in health and disease
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.