The synergistic effect of TGF-b and 1,25-dihydroxyvitamin D 3 on SPARC synthesis and alkaline phosphatase activity in human pulp fibroblasts Prasit Pavasant*, Tussanee Yongchaitrakul, Kassara Pattamapun, Mansuang Arksornnukit Department of Anatomy, Faculty of Dentistry, Chulalongkorn University, Henri Dunant Road, Pathumwan, Bangkok 10330, Thailand Accepted 8 May 2003 Introduction Pulp fibroblasts have been suggested to play roles in dental pulp tissue healing and repair. It is widely accepted that these cells can differentiate into odontoblast-like cells and form reparative dentine. 1 However, factors that control the process of pulp tissue healing and repair are not clearly clarified. Transforming growth factor beta (TGF-b), a multi- functional growth factor, and 1,25-dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ], an active metabolite of Vitamin D, are two of the candidate factors. TGF-b has been implicated to function as an inducer of dentine matrix formation during dentinogenesis. 2 Moreover, TGF-b influenced the differentiation of pulp fibro- blasts and the formation of reparative dentine in vivo. 3,4 It had been demonstrated in vitro that TGF- b could stimulate cell proliferation and protein synthesis, such as type I collagen and secreted osteonectin/SPARC (secreted protein, acidic and rich in cysteine) in pulp fibroblasts. 5—7 The effect of Vitamin D on dentinogenesis has also been reported. Insufficient level of Vitamin D in man results in the hypocalcification of dentine while high level of Vitamin D disturbs the arrangement of dentinal tubule. 8,9 It was shown that 1,25(OH) 2 D 3 could increase alkaline phosphatase activity and osteopontin synthesis in bovine and rat pulp fibroblasts in vitro. 10,11 These results suggest the Archives of Oral Biology (2003) 48, 717—722 KEYWORDS Pulp fibroblast; TGF-b; 1,25(OH) 2 D 3 ; SPARC; Alkaline phosphatase Summary 1,25(OH) 2 D 3 and TGF-b can influence the function and differentiation of dental pulp fibroblasts. In this study, we examined the effect of 1,25(OH) 2 D 3 and TGF-b on the synthesis of SPARC and ALP activity in human pulp fibroblasts. Two isoforms of SPARC, the 43 and 38 kDa, were detected in this cell type. TGF-b increased the synthesis of SPARC about 2.5-fold after 3 days of treatment but had no effect on the ALP activity. On the contrary, 1,25(OH) 2 D 3 increased ALP activity 2-fold but had no effect on SPARC. The combination of TGF-b and 1,25(OH) 2 D 3 significantly induced SPARC synthesis and ALP activity by 5 and 9 folds, respectively (P < 0:05). This finding suggested the synergistic effect between TGF-b and 1,25(OH) 2 D 3 in dental pulp fibroblasts on the synthesis of SPARC and ALP activity. This interaction could influence the function and differentiation of dental pulp fibroblasts. ß 2003 Elsevier Science Ltd. All rights reserved. Abbreviations: PBS, phosphate-buffered saline; DMEM, Dulbecco’s modified Eagle’s medium; FBS, fetal bovine serum  Corresponding author. Tel.: þ66-2-218-8885; fax: þ66-2-218-8870. E-mail address: prasit.pav@chula.ac.th (P. Pavasant). 0003–9969/$ — see front matter ß 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0003-9969(03)00134-1