Transduction of anti-apoptotic proteins into chondrocytes in cartilage slice culture.

Peptides of the protein transduction domain (PTD) mediate the introduction of passenger proteins into cells in vitro and in vivo, where the domains are positively charged. This unusual ability can be exploited for medical applications in protein therapeutics. Chondrocytes are embedded in a dense extracellular matrix, whose components are highly negatively charged. We examined whether PTD mediates the delivery of functional proteins into chondrocytes through the matrix using the super anti-apoptotic protein FNK fused with Tat/PTD peptide (PTD-FNK), the FNK protein being constructed from anti-apoptotic Bcl-xL to enhance its activity. The PTD-FNK protein labeled with a fluorescent dye was incorporated into chondrocytes through the matrix and immunostaining confirmed the transduction into the cells. The PTD-FNK protein protected chondrocytes from cell death induced by Fas antibody and nitrogen oxide (NO). Thus, the PTD peptide has the ability to deliver passenger proteins into chondrocytes by penetrating the extracellular matrix of cartilage.