Corneal stromal cells (keratocytes) express thrombospondins 2 and 3 in wound repair phenotype

Members of the thrombospondin (TSP) family of proteins have been implicated in wound healing. The cells of the corneal stroma (keratocytes) are capable of synthesising TSP-1 in a wound repair phenotype, but do not appear to produce the protein in the normal human adult cornea. We employed reverse-transcriptase polymerase chain reaction (RT-PCR) to determine whether human corneal stromal cells can express TSPs other than TSP-1. Cultured keratocytes contained messenger RNA (mRNA) for TSP-2 and TSP-3 (in addition to TSP-1), but not for TSP-4 or cartilage oligomeric matrix protein (COMP; TSP-5). Keratocytes in the normal cornea contained mRNA for TSP-1 but not for other TSPs. The distribution of keratocyte TSP-2 and TSP-3 immunoreactivity had some similarities to that of TSP-1 and, like TSP-1, neither protein could be detected in the cells of the normal corneal stroma. The observations suggest that keratocytes in wound repair phenotype produce TSP-2 and TSP-3 in addition to TSP-1. TSPs may play a pivotal role in corneal stromal repair and, since TSP-1 and TSP-2 have anti-angiogenic properties, may also have a function in regulating the avascularity of the central cornea.