In vitro growth of bovine articular cartilage chondrocytes in various capacitively coupled electrical fields

Abstract

Isolated articular cartilage chondrocytes from 1- to 3-week-old male Holstein calf knee joints were formed into pellets containing 4 × 10⁶ isolated cells and were grown in tissue culture medium (minimum essential medium/NCTC 135) containing either 1 or 10% newborn calf serum (NBCS) in plastic Petri dishes in 5% CO₂ and air at 37°C in saturation humidity. On the 4th postisolation day either [³⁵S]sulfate or [³H]thymidine was added to the medium, and the pellets were exposed for 24 h to capacitively coupled electrical fields (10, 100, 250, and 1,000 V peak-to-peak, 60 kHz, sine wave signals). The pellets were then harvested, dialyzed, hydrolyzed, and assayed for DNA, protein, [³⁵S]sulfate incorporation, and [³H]thymidine incorporation. Results indicated that at 250 V peak-to-peak there was a statistically significant increase in [³⁵S]sulfate in 1% NBCS and a statistically significant increase in [³H]thymidine in 10% NBCS. At potentials above or below 250 V no changes were noted. Thus, articular cartilage chondrocytes grown in pellet form can be stimulated to increase glycosaminoglycan synthesis or to increase cell proliferation by an appropriate capacitively coupled electrical field. The importance of the serum concentration in the medium in evaluation of biosynthesis in vitro is noted.