Regulation of alpha v beta 3 and alpha 5 beta 1 integrin receptors by basic fibroblast growth factor and platelet-derived growth factor-BB in intrasynovial flexor tendon cells

Integrins are important players in soft tissue healing as molecules that me diate communication between cells and extracellular matrix. Thus, the regul ation of the expression of these molecules would be important during wound repair. To explore the regulatory roles of specific growth factors on integ rin expression by intrasynovial flexor tendon cells, the present study asse ssed the in vitro effects of basic fibroblast growth factor and platelet de rived growth factor-BB on expression of the alpha 5 beta 1 and alpha v beta 3 integrins in these cells. Analyses were carried out at the transcription al (reverse transcription-polymerase chain reaction) and translational (imm unohistochemistry) levels of cellular metabolism. Both types of analyses re vealed increased expression of alpha 5 beta 1 and alpha v beta 3 by tendon cells exposed to either basic fibroblast growth factor or platelet-derived growth factor-BB over a wide range of growth factor concentrations employed in the study. Semiquantitative reverse transcription-polymerase chain reac tion showed that, relative to control, basic fibroblast growth factor and p latelet-derived growth factor-BB increased the expression of alpha v mRNA b y 2- and 3-fold, respectively. Alpha 5 mRNA expression was also increased 3 -fold by basic fibroblast growth factor, and 2-fold by platelet-derived gro wth factor-BB. We believe the results of this study are significant because the specific integrins affected are intimately involved in two events that have been shown to be important to intrasynovial flexor tendon healing, na mely fibronectin deposition (alpha 5 beta 1) as part of the provisional mat rix and angiogenesis/revascularization (alpha v beta 3).