These observations are consistent with those seen in murine fibroblasts [7]. However our current work also indicated that the forced expression of P311 was associated with increased levels of TGF-b1 and COL1A1 mRNA in both normal skin-derived and hypertrophic scar-derived fibroblast-like cells (Fig. 2A2 and 2B) relative to the corresponding control transductants. Conversely inhibition of P311 gene expression resulted in a reduction in the expression of TGF-b1. In addition, after P311 gene transduction, more fibroblasts entered into the S phase of cell cycle (Fig. 2D), which implies that P311 can stimulate the proliferation of fibroblasts. Our results indicate that P311 promotes the produc- tion of TGF-b and COL1A1 in human fibroblasts, and stimulates their proliferation and differentiation to myofibroblasts. We tested the role of P311 in the contraction of fibroblasts in FPCL model in vitro, as myofibroblasts are believed to be responsible for the contraction of hypertrophic scar [24] and a– SMA positive myofibroblasts can cause the contraction of FPCL in vitro [13,15]. Expression of P311 gene was associated with an enhanced level of contraction in normal and hypertrophic scar- derived fibroblasts (Fig. 3). On the other hand, suppression of P311 expression in hypertrophic scar-derived fibroblasts-like cells inhibited the capacity of these cells to mediated collagen contraction (Fig. 4C). These data indicate that P311 gene might be also involved in the contraction of hypertrophic scar. TGF-b1 is considered as the key paracrine/autocrine growth factor in induction and maintenance of the hypertrophic scar. In addition the signaling pathway of TGF-b1 initiates a mechanistic cascade involving activation of fibroblast differentiation which promotes the synthesis of a–SMA and the extracellular matrix, mainly collagen I, with enhanced the contractile ability [1]. Therefore, we hypothesize that P311 induces fibroblast differen- tiation via enhancing the TGF-b1 signaling pathway in human hypertrophic scar. Our results do not seem to be consistent with those of Pan et al which suggested that P311 induced TGF-b1-independent myofi- References 1. Martin P (1997) Wound healing–aiming for perfect skin regeneration. Science 276: 75–81. 2. Singer AJ, Clark RA (1999) Cutaneous wound healing. N Engl J Med 341: 738–746. 3. Wu J, Ma B, Yi S, Wang Z, He W, et al. (2004) Gene expression of early hypertrophic scar tissue screened by means of cDNA microarrays. J Trauma 57: 1276–1286. 4. Fujitani M, Yamagishi S, Che YH, Hata K, Kubo T, et al. (2004) P311 accelerates nerve regeneration of the axotomized facial nerve. J Neurochem 91: 737–744. 5. Taylor GA, Hudson E, Resau JH, Vande Woude GF (2000) Regulation of P311 expression by Met-hepatocyte growth factor/scatter factor and the ubiquitin/ proteasome system. J Biol Chem 275: 4215–4219. 6. Taylor GA, Rodriguiz RM, Greene RI, Daniell X, Henry SC, et al. (2008) Behavioral characterization of P311 knockout mice. Genes Brain Behav 7: 786–795. 7. Pan D, Zhe X, Jakkaraju S, Taylor GA, Schuger L (2002) P311 induces a TGF- beta1-independent, nonfibrogenic myofibroblast phenotype. J Clin Invest 110: 1349–1358. 8. English RS, Shenefelt PD (1999) Keloids and hypertrophic scars. Dermatol Surg 25: 631–638. 9. Mutalik S (2005) Treatment of keloids and hypertrophic scars. Indian J Dermatol Venereol Leprol 71: 3–8. 10. Brown JJ, Bayat A (2009) Genetic susceptibility to raised dermal scarring. Br J Dermatol 161: 8–18. 11. Baryza MJ, Baryza GA (1995) The Vancouver Scar Scale: an administration tool and its interrater reliability. J Burn Care Rehabil 16: 535–538. 12. Cheng B, Liu HW, Fu XB, Sheng ZY, Li JF (2008) Coexistence and upregulation of three types of opioid receptors, mu, delta and kappa, in human hypertrophic scars. Br J Dermatol 158: 713–720. 13. Shin D, Minn KW (2004) The effect of myofibroblast on contracture of hypertrophic scar. Plast Reconstr Surg 113: 633–640. The Role of Human P311 Gene broblast transformation. We do observe myofibroblast transfor- mation but this occurs in the presence of up regulation of TGF-b1 and collagen. The former results were based on data obtained with murine fibroblasts. Hypertrophic scars appear to be unique to humans as no animals are known to form these lesions [8,9,10]. Furthermore, animal models including athymic mice, rats, hamster cheek pouch, guinea pigs and rabbit ear models present significant differences when compared with human hypertrophic scars suggesting that these may have different pathogenic mechanisms than human hypertrophic scar [25]. In our study, we employed human fibroblasts from normal skin and hypertro- phic scar as the target cells which is consistent with the pathogenesis of human hypertrophic scar. The results of our study suggest that P311 may have different regulatory functions in fibroblasts of human origin compared with in murine fibroblasts. In summary, our work for the first time shows the function of P311 gene in human fibroblasts, i.e., P311 gene can stimulate human fibroblast proliferation, induce myofibroblast phenotype, promote the expression of TGF-b1 and COL1A1, and enhance the contraction of human fibroblasts in FCPL. These data strongly indicate that P311 may be involved in the hypertrophic scar pathogenesis and contraction via enhancing the expression of TGF-b1. Further studies of P311 function may provide new insights into the molecular events of hypertrophic scar formation and possibly provide new approaches for the control of hypertrophic scar formation. Author Contributions Conceived and designed the experiments: BM JW. Performed the experiments: JT XP GL WH SY. Analyzed the data: JT XP GL JW JW. Contributed reagents/materials/analysis tools: CC SL. Wrote the paper: BM JW JW. 14. Phan TT, Sun L, Bay BH, Chan SY, Lee ST (2003) Dietary compounds inhibit proliferation and contraction of keloid and hypertrophic scar-derived fibroblasts in vitro: therapeutic implication for excessive scarring. J Trauma 54: 1212–1224. 15. Grinnell F (1994) Fibroblasts, myofibroblasts, and wound contraction. J Cell Biol 124: 401–404. 16. van der Veer WM, Bloemen MC, Ulrich MM, Molema G, van Zuijlen PP, et al. (2009) Potential cellular and molecular causes of hypertrophic scar formation. Burns 35: 15–29. 17. Wang J, Jiao H, Stewart TL, Shankowsky HA, Scott PG, et al. (2007) Improvement in postburn hypertrophic scar after treatment with IFN-alpha2b is associated with decreased fibrocytes. J Interferon Cytokine Res 27: 921–930. 18. Lee JY, Yang CC, Chao SC, Wong TW (2004) Histopathological differential diagnosis of keloid and hypertrophic scar. Am J Dermatopathol 26: 379–384. 19. Li F, Fan C, Cheng T, Jiang C, Zeng B (2009) Efficient inhibition of fibroblast proliferation and collagen expression by ERK2 siRNAs. Biochem Biophys Res Commun 382: 259–263. 20. Wynn TA (2008) Cellular and molecular mechanisms of fibrosis. J Pathol 214: 199–210. 21. Dabiri G, Tumbarello DA, Turner CE, Van de Water L (2008) TGF-beta1 slows the growth of pathogenic myofibroblasts through a mechanism requiring the focal adhesion protein, Hic-5. J Invest Dermatol 128: 280–291. 22. Dabiri G, Tumbarello DA, Turner CE, Van de Water L (2008) Hic-5 promotes the hypertrophic scar myofibroblast phenotype by regulating the TGF-beta1 autocrine loop. J Invest Dermatol 128: 2518–2525. 23. Desmouliere A, Geinoz A, Gabbiani F, Gabbiani G (1993) Transforming growth factor-beta 1 induces alpha-smooth muscle actin expression in granulation tissue myofibroblasts and in quiescent and growing cultured fibroblasts. J Cell Biol 122: 103–111. 24. Gabbiani G, Ryan GB, Majne G (1971) Presence of modified fibroblasts in granulation tissue and their possible role in contraction. Cellular and Molecular Life Sciences 27: 549–550. 25. Ramos ML, Gragnani A, Ferreira LM (2008) Is there an ideal animal model to study hypertrophic scarring? J Burn Care Res 29: 363–368. PLoS ONE | www.plosone.org 6 April 2010 | Volume 5 | Issue 4 | e9995