In Vitro Monitoring of a Cultured Human Retinal Pigment Epithelium Using 1375-nm Spectral-Domain Optical Coherence Tomography

Measurement of cell number is important in cell-based in vitro screenings for therapeutic drugs and tissue engineering such as cell culture maintenance, cell plating, and cell growth, as well as monitoring of cell viability, proliferation, and cytotoxicity. We performed cell counting using intensity-based in vitro spectral-domain optical coherence tomography (SD-OCT). Adult retinal pigment epithelium cells were cultured on a glass dish to prevent diffuse reflection from the surface, and the dish was tilted by 15° during OCT imaging to reduce coherence noise from specular reflection. Rasterized scanning was performed to generate a three-dimensional volume image with an en face image of the retinal pigment epithelium cell layers. Cell counting was achieved by measuring the density of bright spots after layer extraction and thresholding. Two other cell counting methods were also performed for the purpose of comparison, one using a hemocytometer and the other using water-soluble tetrazolium-1; cell counting by in vitro OCT yielded results better than those from the hemocytometer. Our results showed that in vitro OCT systems can be a powerful tool for estimating and analyzing cell density in a cultured sample without the need for dyeing the sample or causing cell death.