Glial fibrillary acidic protein, an early and sustained indicator of retinopathy progression.

Macroglial cells, particularly astrocytes and Müller glial cells (MGCs), are crucial for maintaining retinal health and function. Both cell types express glial fibrillary acidic protein (GFAP), although their expression levels and patterns differ. In a healthy retina, astrocytes constitutively express GFAP, whereas MGCs typically show low or undetectable levels. In response to retinal insults, macroglial cells are activated through a process known as gliosis to preserve retinal homeostasis. The gliotic response includes cellular hypertrophy and the upregulation of intermediate filaments -primarily GFAP- as a protective mechanism. However, when harmful stimuli persist, both astrocytes and MGCs may contribute to pathology, becoming associated with ongoing damage and loss of retinal function. Changes in GFAP expression have been described in conditions like diabetic retinopathy, sickle-cell retinopathy, and age-related macular degeneration, indicating retinal stress and dysfunction. A deeper understanding of GFAP's dual role in retinal diseases is critical for developing effective treatments for these conditions and for identifying its potential as a biofluid-based biomarker.