Transforming growth factor-β (TGF-β) plays a key role during corneal stroma scarring.It is a critical regulator in abnormal deposition of extracellular matrix (ECM) and construction of collagen fibers.TGF-β is a family cytokines secreted by a variety of cells.It has multiple effects only when it is activated.The major signaling pathway of TGF-β is Smad,which is activated by the binding of TGF-β and its receptors.TGF-β stimulates the synthesis and secretion of collagen and proteoglycan,which results in disbalance of synthesis and degradation of ECM.The mechanism of TGF-β on promoting corneal fibrosis includes upregulating connective tissue growth factor (CTGF),downregulating keratin sulfate proteoglycans(KSPGs) and inhibiting the degradation of ECM by regulating matrix metalloproteinases(MMPs).Recently,TGF-β has been a promoting growth factor of scar-free wound healing because of its extensive biological effects.This review summarized biological characteristics of TGF-β,its receptors and Smads signal pathway and the molecular mechanism that accelerates corneal stroma scarring.

Background Transforming growth factor-β1(TGF-β1) plays an important role in corneal woundhealing.The effects of TGF-β1 on the synthesis of extra cellular matrix (ECM) vary upon different concentrations.Previous studies focused on the effects of high concentration of TGF-β1 on keratocytes under the two-dimensional culture condition,and the effect of low concentration of TGF-β1 on the synthesis of ECM in keratocytes remains unclear.Objective This study was to investigate the growth of Pellet,a three-dimensional model of corneal stroma cells in vitro,and its ECM synthesis under a low concentration of TGF-β1.Methods Bovine corneal stromal cells were isolated from fresh bovine eyeballs by two-step digestion by collagenase and cultured using DMEM/F12 medium with 10％ fetal bovine serum (FBS).Pellets derived fresh bovine keratocytes with culture medium containing 0.25 ng/ml TGF-β1 +5％ FBS and 0.50 ng/ml TGF-β1 +5％ FBS were established,respectively.The morphology of Pellets was observed under the natural light at 48 hours,1 week,2 weeks and 3 weeks after culture.In 3 weeks after culture,the cell structures was observed by hematoxylin-eosin staining,and Calcein-AM/propidium (Calcein-AM/PI) staining was used to assay the cell viability.Real-time flurorescence quantitative PCR and immunofluorescence technology were applied to analyze the expressions of α-smooth muscle actin (α-SMA),fibronectin (FN),type Ⅰ collagen (Col Ⅰ) and type Ⅲ collagen (Col Ⅲ) mRNA and proteins.RT-PCR was employed to detect the expressions of lumican (LUM) mRNA and keratocan (KERA) mRNA in the cells.Results Cells in Pellet clustered throughout the culture duration.Hematoxylin-eosin staining showed the mass red-dyed collagen fibers in both 0.25 ng/ml TGF-β1 +5％ FBS group and 0.50 ng/ml TGF-β1 +5％ FBS group,and most cells possessed complete structures.The death rate of the cells was (33.60±1.65)％ in the 0.25 ng/ml TGF-β1 +5％ FBS group and (30.90±0.78) ％ in the 0.50 ng/ml TGF-β1 +5％ FBS group,showing an insignificant difference between them (t =0.144,P=0.887).The expressions of α-SMA,FN and Col Ⅲ proteins in 0.25 ng/ml TGF-β1 +5％ FBS group were lower than those in the 0.50 ng/ml TGF-β1 + 5 ％ FBS group (tα-SMA =4.622,P =0.010;tFN =2.973,P =0.040;tCol Ⅲ =7.845,P＜0.001),but the expression of Col Ⅰ in 0.25 ng/ml TGF-β1 +5％ FBS group was higher than that in 0.50 ng/ml TGF-β1+5％ FBS group (tColⅠ =4.022,P=0.016).The ratio of Col Ⅲ/Col Ⅰ in 0.25 ng/ml TGF-β1+5％ FBS group was lower than that in the 0.50 ng/ml TGF-β1 +5％ FBS group in both mRNA and protein level (tmRNA =-3.039,P =0.038;tprotein =3.215,P =0.032).The expression of LUM mRNA and KERA mRNA were detected in Pellet at different time points.The expression of LUM mRNA in 0.25 ng/ml TGF-β1 +5％ FBS group increased over time.While in 0.50 ng/ml TGF-β1 +5％ FBS group,the expression of LUM mRNA peaked at 1 week but declined at 2 weeks.The expression of KERA mRNA in two groups were all peaked at 1 week but declined at 2 weeks.Conclusions Low-dose TGF-β1 in Pellet can maintain the normal growth of keratocytes and synthesize ECM.The expression of ECM tends to the normal condition after reducing the concentration of TGF-β1,implying a scarless expression.

Background Extracellular matrix (ECM) fibrosis leads to corneal scaring during the process of cornea wound healing.Transforming growth factor-β1 (TGF-β1) is known to mediate overproduce of ECM components.Our previous study developed a three-dimensional model for corneal stromal cells culture in vitro.Objective The hypothesis of this study was to apply TGF-β1 in the three-dimensional culture system to establish a corneal stroma ECM fibrosis model.Methods Fresh bovine corneas were extracted for the culture of bovine keratocytes in constructed three-dimension culture system.The Pellets were cultured in the DMEM/F12+ 10％ fetal bovine serum (FBS) medium with 0.5 ng/ml or 1.0 ng/ml TGF-β1 or without TGF-β1,respectively.Calcein AM/(propidium iodide) PI staining was employed to assay the cell viability 2 weeks after culture.The expressions of α-smooth muscle actin (α-SMA),type Ⅰ collagen (Col Ⅰ) and Col Ⅲ mRNA and protein in the cells were detected by real-time PCR and Western blot respectively 48 hours,1 week and 2 weeks after cultured.The results were statistically analyzed.Results Cultured for 48 hours in the Pellet system,corneal stromal cells clustered and was identified alive by Calcein-AM/PI staining in 2 weeks.The relative expression levels of α-SMA,Col Ⅰ and Col m mRNA were elevated in both the 0.5 ng/ml and 1.0 ng/ml TGF-β1 supplement groups in comparison with the only DMEM/F12+10％ FBS group,with marked difference among the three groups (Fgroup =696.745,P＜0.001;Fgroup =35.166,P＜0.001;Fgroup =33.677,P＜0.001),and the expression levels increased with the lapse of culture time (Ftime =5.863,P＜0.05;Ftime =298.614,P＜0.001;Ftime =607.472,P＜0.001).The synthetic rate of Col Ⅲ mRNA was obviously faster than that of Col Ⅰ mRNA.Western blot showed that only a trace of α-SMA,Col Ⅰ and Col Ⅲ were detected 48 hours and 1 week after culture.The expression levels of α-SMA,Col Ⅰ and Col Ⅲ in Pellet system in 0.5 ng/ml TGF-β1 medium were 0.395±0.208,1.060±0.175 and 0.629±0.382,and in 1.0 ng/ml TGF-β1 medium were 0.758±0.228,1.201 ±0.187 and 0.753±0.468,respectively 2 weeks after culture,significant differences were shown among the three groups (α-SMA:F=10.691,P＜0.05;Col Ⅰ:F=14.094,P＜0.05;Col Ⅲ:F=10.995,P＜0.05).Conclusions Addition of TGF-β1 and serum enhance the assembly and fibrosis of ECM,showing the higher expressions of specific fibrotic markers in bovine keratocytes Pellet.This culture systerm can be used as a candidate three-dimensional model for corneal stroma ECM fibrosis.

Precisely delivering combinational therapeutic agents has become a crucial challenge for anti-tumor treatment. In this study, a novel redox-responsive polymeric prodrug (molecular weight, MW: 93.5 kDa) was produced by reversible addition-fragmentation chain transfer (RAFT) polymerization. The amphiphilic block polymer-doxorubicin (DOX) prodrug was employed to deliver a hydrophobic photosensitizer (PS), chlorin e6 (Ce6), and the as-prepared nanoscale system [NPs(Ce6)] was investigated as a chemo-photodynamic anti-cancer agent. The glutathione (GSH)-cleavable disulfide bond was inserted into the backbone of the polymer for biodegradation inside tumor cells, and DOX conjugated onto the polymer with a disulfide bond was successfully released intracellularly. NPs(Ce6) released DOX and Ce6 with their original molecular structures and degraded into segments with low MWs of 41.2 kDa in the presence of GSH. NPs(Ce6) showed a chemo-photodynamic therapeutic effect to kill 4T1 murine breast cancer cells, which was confirmed from a collapsed cell morphology, a lifted level in the intracellular reactive oxygen species, a reduced viability and induced apoptosis. Moreover, ex vivo fluorescence images indicated that NPs(Ce6) retained in the tumor, and exhibited a remarkable in vivo anticancer efficacy. The combinational therapy showed a significantly increased tumor growth inhibition (TGI, 58.53%). Therefore, the redox-responsive, amphiphilic block polymeric prodrug could have a great potential as a chemo-photodynamic anti-cancer agent.