Abstract
Abstract: :
Purpose: To determine the relationship between the astrocytic and vascular lineages during development of the human retina and to further evaluate evidence for the presence of vascular precursor cells in the developing human retina. Methods: To determine the relationship between astrocytes, astrocyte precursor cells (APCs), and patent blood vessels, Pax-2/GFAP/CD-34 triple label immunohistochemistry was applied to 3 retinae aged 12, 14 and 20 weeks gestation (WG). Adenosine diphosphatase (ADPase) enzyme histochemistry, which identifies endothelial cells and vascular precursors (angioblasts) was applied to human retinae aged 12, 16 and 20 WG. Nissl stain, a non-specific cell soma marker, was applied to a 15 and 18WG human retina. Established lumens were visualized with CD34 and ADPase. Results: Topographical analysis of the distribution of Nissl stained spindle shaped, vascular precursor cells and ADPase+ vascular cells showed these two populations to have similar distributions at corresponding ages. ADPase+ vascular precursor cells preceded the leading edge of patent vessels by more than 1 mm. In contrast, Pax-2+/GFAP- APCs preceded the leading edge of CD34+ blood vessels by only a few microns. Two populations of ADPase+ cells were evident, a spindle shaped population located superficially within the NFL and a round population located predominantly in the GCL. The outer limits of these populations remain static with maturation; however, the relative numbers of round cells decline with maturation. Conclusion:Utilizing a combination of Pax-2/GFAP/CD34 immunohistochemistry, Nissl staining and ADPase enzyme histochemistry, we have shown that the vascular precursor cells identified using ADPase and Nissl (presumed angioblasts) represent a distinct population to Pax-2+/GFAP- astrocyte precursor cells in human retina. Our observations lead us to conclude that formation of the initial human retinal vasculature takes place via vasculogenesis with the prior invasion of vascular precursor cells and provides in vivo evidence that association with vascular endothelial cells induces astrocyte differentiation.
Keywords: 614 vascular cells • 565 retinal glia • 564 retinal development