398 DIFFERENTIATION OF MOUSE EMBRYONIC STEM CELLS INTO CARDIOMYOCYTES BY USING SLOW TURNING LATERAL VESSEL (STLV/BIOREACTOR)

Abstract

Cardiomyocytes derived from embryonic stem (ES) cells are anticipated to be valuable for cardiovascular drug testing and disease therapies. The overall efficiency and quantity of cardiomyocytes obtained by differentiation of ES cells is still low. To enable a large-scale culture of ES-derived cells, we have tested a scalable bioprocess that allows direct embryoid body (EB) formation in a fully controlled, bioreactor/STLV (slow turning lateral vessel, Synthecon, Inc., Houston, TX, USA) following inoculation with a single cell suspension of mouse ES cells. Technical parameters for optimal cell expansion and efficient ES cell differentiation were compared, such as ES cell seeding density (3 × 10⁵ and 5 × 10⁵ cells mL^-1) into the bioreactor and day of transfer and plating of EB on gelatinated petri dishes (Day 2, Day 3, Day 4, and Day 5). The quantity and quality of EB production including the yield and size of EB, as well as viability and apoptosis of cells, were analyzed. Furthermore, after cultivation, well-developed contracting EB with functional cardiac muscle were obtained in which the percentage of EB beating/well and several specific cardiac genes [cardiac Troponin T (cTnT) and α-actinin] expression were also determined. Data are expressed as mean ± SEM of at least 3 independent experiments. Statistical analyses included one-way ANOVA and Student’s t-test Statistical significance was set at P < 0.05. The results showed that 5 × 10⁵ ES cells mL^-1 seeded into the STLV significantly improved the homogeneity of size of EB formed compared with 3 × 10⁵ ES cells mL^-1. The EB derived from Days 2 or 3 culturing in STLV had less necrotic cells than Days 4 and 5 groups. Furthermore, plating these EB on Days 2 and 3 resulted in significantly more EB beating/well than that of Days 4 and 5 groups. For cardiac differentiation, the group with 5 × 10⁵ ES cells mL^-1 seeded into STLV and transferred and plated on Day 3 expressed more cardiac markers than other groups. In conclusion, the optimized rotary suspension culture method can produce a highly uniform population of efficiently differentiating EB in large quantities in a manner that can be easily implemented by basic research laboratories. This method provides a technological platform for the controlled large-scale generation of ES cell-derived cells for clinical and industrial applications.

This work was financed by The Thailand Commission on Higher Education (CHE-PhD-SW-2005-100), EUFP6 CLONET (MRTN-CT-2006-035468), NKFP_07_1-ES2HEART-HU (OM-00202-2007), and EUFP7 (PartnErS, PIAP-GA-2008-218205).