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Aby Joseph, Colin Chu, Kosha Dholakia, Guanping Feng, Andres Guevara-Torres, Jesse Schallek; Label-free tracking of single blood cells in the retinal immune response. Journal of Vision 2019;19(15):20. doi: https://doi.org/10.1167/19.15.20.
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© ARVO (1962-2015); The Authors (2016-present)
Leukocytes within the circulation are recruited to the central nervous system (CNS) in response to injury. However, imaging the immune response in the CNS is challenging due to a dearth of approaches that provide label-free study of leukocyte recruitment, surveillance and motility at the cellular level. Recently, adaptive optics scanning light ophthalmoscopy has enabled detailed study of single cell blood flow1, as well as imaged immune cell motility in the healthy retina. Here we deploy adaptive optics to study long- and short-term dynamics of the immune response. Healthy C57BL/6J mice were imaged in baseline state and were subsequently given an intravitreal injection of lipopolysaccharide, to induce an acute inflammation2. We tracked single red and white blood cells using phase contrast using 796 nm light to visualize blood cell dynamics label-free. Imaging the same mice over minutes to weeks revealed remarkable vascular and immune cell changes happening over 10-5 to 101 mm/s.
Venules and arterioles showed heterogenous changes in diameter and blood cell velocity at 6–24 hours in response to insult. Over hours, venules dilated by as much as 25.6%. While, arterioles did not appreciably dilate, blood cell velocity increased by as much as 103.1%. Total blood flow increased arterial and venular branches showing commensurate conservation of flow that increased by as much as 98.4%. Within 3–10 days, leukocyte recruitment and blood flow returned to near baseline activity as inflammation subsided2. Label-free adaptive optics ophthalmoscopy provides a new window to study the interplay of the vascular and immune systems in vivo.
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