Xenogeneic liver support systems

Liver support systems (LSS) incorporating living xenogeneic (porcine) cells are currently in clinical use. However, their efficacy remains uncertain, and there are concerns regarding possible disease transmission. A key component of LSS is a semipermeable membrane (SPM) that separates the patient's circulation from the xenogeneic cells, and it is the pore sizes of the SPM that determine the size of molecules passing between the patient's circulation and the foreign cells. To achieve effective detoxification of the blood of patients with liver failure, it is probable that pore sizes must be of a size that could allow passage of viruses potentially infective to humans. We review the current state of clinical exogeneic LSS and discuss the major issues surrounding their use. With approximately 40 patients treated over the past 9 years, we conclude that LSS presently in use produce effective short-term benefits with no reports of immunological, physiological, or pathological complications. Nevertheless, with the pore sizes of SPM in use, disease transmission seems possible, and further advances are required. Our results support the establishment of the controlled clinical trials presently underway.