Bioreactors and components of bioreactors are described as may be beneficially utilized in development and conditioning of cellular materials for study or implant. The bioreactors are modular, and components of the bioreactors can be easily assembled with alternatives provided to develop specific, predetermined conditioning environments for cellular materials (e.g., implantable tissue). By selection of one of multiple alternative compliance chambers, a bioreactor can be utilized to condition tissue in a low-pressure circuit (e.g., a pulmonary heart circuit), and by utilization of an alternative compliance chamber, the bioreactor can instead condition tissue in a high-pressure circuit (e.g., an aortic heart circuit).