Suspension-type cells, which do not require scaffold adhesion during their culture, is commonly regarded as cells derived from blood cells. In bio-pharmaceutical researches, antibody-production cells are also another major cell known as suspension-type cells. However, by the recent tissue engineering advancements, more and more types of suspension-type cells are required for cell therapy. Chimeric antigen receptor (CAR) T-cells are one of the cutting-edge cellular products that are expanding worldwide and therefore expected to be manufactured in high quality as medicinal products. Furthermore, suspension-type culture is another important cell culture technique to efficiently scale up the cells for therapy, therefore various types of cells are trying to be cultured in a suspension manner (including the usage of microcarriers or special density medium). However, compared to the adhesion-type cells, their daily quality monitoring had been difficult by conventional microscopies, since suspension-type cells float and move even during the imaging process. Therefore, although there had been numerous image-based analysis techniques that reported effective non-invasive analysis performances to evaluate the culturing cells, there are rare cases reported to apply label-free image-based analysis techniques for suspension-type cells. Our group has been investigating the use of microscopic images to non-invasively evaluate, record, and monitor cellular quality during their culture process for evaluating cell profiles or screening for adhesion cells [1,2]. In this study, we investigated the possibility and effectiveness of applying our method for analyzing suspension-type cells.
[Method] By optimizing the microscopy type and imaging condition, we determined a stable protocol to obtain their morphological features in the micro-well plates. Furthermore, we developed the exhaustive focusing algorithm to obtain “sharp contrast” for every cell in the field of view, to obtain robust and reproducible morphological feature parameters. We intentionally prepared suspension-type cells under culture stress (lactic acid, ammonia), and created cell quality variations. Using multiple morphological feature parameters extracted from the bright-field microscopic images, we analyzed the correlation between the stress condition and their morphological profiles using statistical methods and machine learning models.
[Results and conclusions] From our data, we found that the selection and creation of effective morphological feature parameters for suspension-type cells enable to detect of stress-triggered cell growth arrest only from their morphological profiles. Moreover, we applied our image analysis tools for several suspension-type cells to evaluate the robustness of our analysis technique and found that time-course morphological transition information is important not only for the adhesion-type cells but also the suspension-type cells.
- Ishikawa, K., et al., SLAS discovery, 24, 47-56 (2018)
- Imai, Y., et al., Regen. Therapy, 9, 15-23 (2018)