Platelet-rich plasma increases proliferation of tendon cells by modulating Stat3 and p27 to up-regulate expression of cyclins and cyclin-dependent kinases.

OBJECTIVES: To investigate effects of platelet-rich plasma on tendon cell proliferation and the underlying molecular mechanisms. MATERIALS AND METHODS: Platelet-rich plasma was prepared manually by two-step centrifugation. Proliferation was evaluated in cultured rat tendon cells by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. Cell cycle progression was assessed by flow cytometry. Messenger RNA expression of proliferating cell nuclear antigen (PCNA), cyclin E1, A2 and B1, and cyclin-dependent kinases (Cdks) 1 and 2 was assessed by real-time polymerase chain reaction. Protein expression of the above cyclins and Cdks and of signal transducer and activator of transcription (Stat) 3 and p27 was evaluated by western blotting. RESULTS: Platelet-rich plasma used in the present study had concentrations of platelets, TGF-ß1 and PDGF over 3-fold higher than normal whole blood. Platelet-rich plasma enhanced tendon cell proliferation (P = 0.008) by promoting G1 /S phase transition in the cell cycle, and increased expression of PCNA, cyclin E1, A2 and B1, Cdks1 and 2, and phosphorylated Stat3, while inhibiting p27 expression. CONCLUSIONS: Platelet-rich plasma contains high concentrations of TGF-ß1 and PDGF that increase tendon cell proliferation by modulating Stat3/p27(Kip1), which enhances expression of cyclin-Cdk complexes that promote cell cycle progression. These results provide molecular evidence for positive effects of platelet-rich plasma on tendon cell proliferation, which can be useful in clinical applications of tendon injury.

IFI27, a novel epidermal growth factor-stabilized protein, is functionally involved in proliferation and cell cycling of human epidermal keratinocytes.

OBJECTIVES: IFI27 is highly expressed in psoriatic lesions but its function has not been known. The present study aimed to explore its role in proliferation of epidermal keratinocytes. MATERIALS AND METHODS: IFI27 knockdown and over-expression in keratinocytes were used to compare their proliferation, by MTT assay, apoptosis (by annexin V binding) and cell cycle progression by flow cytometry. Formation of cyclin A/CDK1 complex was examined by a co-immunoprecipitaion method. Anti-proliferation effects of IFI27 were also examined in vivo by topical application of IFI27 siRNA on imiquimod-induced psoriatic lesions, in a mouse model. RESULTS: Epidermal growth factor was demonstrated to increase IFI27 expression by prolonging half-life of IFI27 protein. The IFI27 knockdown in keratinocytes reduced the proliferation rate, but had no effect on apoptosis nor on apoptosis-related genes. Interestingly, IFI27 knockdown resulted in S-phase arrest that was found to be associated with increased Tyr15 phosphorylation of CDK1, reduced CDC25B and reduced formation of cyclin A/CDK1 complex. In addition, IFI27 knockdown was also shown to activate p53 by Ser15 phosphorylation and increase p21 expression. Topical application of IFI27 siRNA on imiquimod-induced psoriatic lesion in a mouse model reduced epidermal thickness, formation of rete ridges and PCNA expression. CONCLUSIONS: Our study demonstrates for the first time, that cell function of IFI27 is involved in proliferation of skin keratinocytes both in vitro and in vivo. It suggests that IFI27 might be a suitable target for development of a novel anti-psoriasis therapy.

Berberine reduces leukocyte adhesion to LPS-stimulated endothelial cells and VCAM-1 expression both in vivo and in vitro.

Leukocyte adhesion to endothelium plays a critical initiating role in inflammation. Berberine, an anti-inflammatory natural compound, is known to attenuate lipopolysaccharide (LPS)-induced lung injury and improve survival of endotoxemic animals with mechanism not fully clarified. This study investigated the effects of berberine on the LPS-induced leukocyte-endothelial cell adhesion both in vivo and in vitro. We first established an animal model to observe the in vivo LPS-induced adhesion of leukocytes to the endothelium of venules in the lung tissue dose-dependently. Pretreatment of LPS-stimulated rats with berberine for 1 h reduced the leukocyte-endothelium adhesion and vascular cell adhesion molecule-1 (VCAM-1) expression in lung. Pretreatment of LPS-stimulated vascular endothelial cells with berberine also dose-dependently decreased the number of adhered THP-1 cells and VCAM-1 expression at both RNA and protein levels. Berberine was further confirmed to inhibit the nuclear translocation and DNA binding activity of LPS-activated nuclear factor-kappa B (NF-kappa B). These data demonstrated an additional molecular mechanism for the profound anti-inflammatory effect of berberine.