ABSTRACT
<i>Background:</i> Enamel matrix derivative placed in the backs of rats induces numerous eosinophilic round bodies (ERBs) and hard tissue. ERBs were analyzed by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and by database analysis. Subsequently, a seven-amino-acid sequence was identified, and an artificial oligopeptide was synthesized with its sequence. The present experiment was carried out to clarify whether or not the peptide induces hard tissue formation <i>in vivo</i>.<i>Methods:</i> Synthetic oligopeptide was injected into the backs of 15 rats. After injection, the tissues were excised at various times and prepared for light and immune-light microscopy.<i>Results:</i> A white lump was macroscopically observed in each rat back 14 days after injection of 7.5 and 15 mg/mL synthetic oligopeptide, and endochondral ossification and bone formation were microscopically observed in one rat back 14 days after injection of 15 mg/mL synthetic oligopeptide.<i>Conclusions:</i> The synthetic oligopeptide is pure, 1,118 dalton, and apparently low-toxicity. It seems to produce hard tissues, such as cartilage and bone tissue.