Electric stimulation has long been used as a tool to promote connective tissue healing, but the mechanism(s) by which this is accomplished are not yet known. We have previously determined, using mass cultures of fetal bovine articular chondrocytes, a specific set of capacitively coupled electrical stimulation parameters (e.g., duration of stimulation, response time, amplitude, frequency, and duty cycle) that significantly elevated production of collagen and proteoglycan, and up-regulated type II collagen and aggrecan mRNA expression in vitro. In the present study, we applied our best signal parameters (30-min continuous stimulation (100% duty cycle) followed by a pulsed (I h on, 5 h off, 4x/day) 50% (1 min on, 1 min off) duty cycle) to cultures of adult bovine articular cartilage explants and obtained similar results. Since the latter system more closely mimics the in vivo chondrocyte environment, these data argue for the utility of electric stimulation for the maintenance of adult cartilage matrix in situ. (c) 2006 Elsevier Inc. All rights reserved.