Observation of individual cell behaviors to analyze mitogenic effects of sericin

Abstract

Mammalian cell cultures are used in many fields. Various biologically active agents are produced in mammalian cell cultures because of bioactivity derived from glycosylation. Ex vivo cultures of various cells including chondrocytes and immunocytes are performed for regenerative medicine and cell therapy. Currently, most of mammalian cell cultures require supplementation of fetal bovine serum (FBS). However, FBS should be avoided due to concerns related to bovine spongiform encephalopathy (BSE) or other infections including viruses that may occur. Therefore, we investigated sericin as an alternative to FBS, and found that sericin could promote proliferation of hybridoma cells. However, mechanisms whereby sericin promotes cell proliferation are still unknown. Microscopic observations indicated that hybridoma cells in the presence of sericin tended to be cohered, implying that sericin might allow cells to aggregate to each other, and interactions between these aggregated cells might induce proliferation, or suggesting that aggregation might be due to proliferation without detachment of cells after cell division. In this study, we attempted to determine whether aggregation of cells in the presence of sericin was due to migration or post-cell divisional detachment. Towards this aim, we used a computer-controlled observation system associated with image analysis. Consequently, results indicated that sericin strengthened attachment between cells after cell division to induce cohesion between cells.