Condensation of feline adipose tissue-derived mesenchymal stem cells by electrical stimulation

Abstract

Background & Aim There are many studies that induce differentiation into cartilage cells by treating the growth factors in mesenchymal stem cells (MSCs) or alter the properties of MSCs by genetic modification. However, studies on cartilage differentiation are still insufficient. Recently, many studies have been reported that stem cells can differentiate into various cells by electrical stimulation (ES). An important step in the process of cartilage differentiation is pre-chondrogenic condensation, which is the stage where cartilage formation begins by condensation of stem cells and cartilage cells in the microenvironment of the joint. Methods, Results & Conclusion ES was applied to feline adipose tissue-derived MSCs (fAD-MSCs) using an electrical stimulator, which is a multi-channel stimulator designed for chronic stimulation of bulk quantities of cells in culture. This instrument emits bipolar pulses to culture media immersed carbon electrodes of a 35 mm dishes. ES was applied to fAD-MSCs cultured under conditions of high-density micro-mass (2 × 105 cells/10 μL) under ES of 1∼20 V/cm, with a duration of 8 ms and a frequency of 5.0 Hz. At indicated time points, we observed size of micro-mass, density and shapes. To induce cell to cell communication, make fAD-MSCs into micromass (2 × 105 cells/10 μL), a mass of cells in a small space, and induce condensation through ES. Condensation behaviors of fAD-MSCs in micro-mass culture were examined using phase contrast images during culture for 3 days under ES. Consistently, micro-mass caused compact condensation by ES at specific condition. Time-course observations of condensation behaviors of fAD-MSCs in micro-mass culture were examined with phase contrast images during culture for 3 days in maintenance medium only (control), and maintenance medium under ES, respectively. As a result, time-dependent observations showed that ES induced gradual aggregation of fAD-MSCs into compact structures within 3 days. This study might contribute to the differentiation of MSCs cells into cartilage cells by inducing pre-chondrogenic condensation under specific ES.