Proteins having substantially the same biological activity as PDGF are provided. In one aspect, a protein homodimer having two polypeptide chains is disclosed, each of the chains being a mosaic of amino acid sequences substantially identical to portions of the A- and B-chains of PDGF, the protein being chemotactic or mitogenic for fibroblasts. Therapeutic compositions comprising such proteins in combination with a physiologically acceptable carrier or diluent are also provided. Such therapeutic compositions may be used within methods for enhancing the wound-healing process in warm-blooded animals.