MGF- and myostatin-mRNA regulation in masseter muscle after orthognathic surgery.

Patients with prognathism and retrognathism show extensive morphologic changes after orthognathic surgery. The inability of muscles to adapt adequately might be one reason for observed relapses. The aim of this prospective study was to analyze the regulation of functional genes after surgery and changes in myosin heavy chain (MyHC) isoform expression, a potential molecular marker profile for inadequate muscle adaptation. 29 adult patients with prognathic and retrognathic mandibles were involved. A total of 232 muscle biopsies were taken from both masseter muscles presurgically and 6 months later. The mRNA expression of "mechano growth factor" (MGF), myostatin, and 3 MyHC isoforms were quantified by real-time polymerase chain reaction. The MGF mRNA was significantly up-regulated (P < .005), whereas myostatin mRNA showed no significant regulation. There was a shift in MyHC isoform expression. The MyHC-I mRNA was decreased (P < .005), whereas MyHC-IIa mRNA was increased (P < .005). The coherence of increased MGF expression and MyHC isoform shift 6 months after orthognatic surgery indicates an adequate muscle adaptation and higher mastication activity.