ABSTRACT
The fibrovascular membrane of proliferative diabetic retinopathy(PDR)cause severe damage to the structure and function of eye.The pathogenesis and development of fibrovascular membrane are associated with muhipie cellular factors,such as transforming growth factor(TGF),connective tissue growth factor(CTGF),basic fibroblast growth factor(bFGF),vascular endothelial growth factor(VEGF),platelet-derived growth factor(PDGF),tumor necrosis factor(TNF),extracellular matrix(ECM),matrix metalloproteinases(MMPs),endothelin and chemotactic factor,etc..So,the molecular mechanism of fibrovascular membrane of PDR is extremely complex.The relationship of pathogenesis on the fibrosis of PDR to cytokines,extracellular matrix,MMPs and other factors were summarized.
ABSTRACT
Background The tissue-engineered cornea is becoming the hot spot in the ophthalmologic field,while the research of corneal substitute is in the ascendant,because it is more similar to the corneal morpha and easy to survive in vivo.Objective This study was to investigate the biocompatibility of recombinant human type-Ⅲ collagen/poly9 ( 3-( methacryloylamino ) propyl dimethyl ( 3-sulfopropyl ) ammonium hydroxide ) ( PMPDSAH ) interpenetrating polymer network (IPN) (RHC-Ⅲ/PMPDSAH IPN) hydrogel as a tissue-engineered cornea in rabbit eye and its feasibility as the corneal substitute.Methods One hundred and eight rabbits were randomly divided into experimental group( 90 rabbits) and normal control group ( 3 rabbits),and 15 rabbits ( 30 eyes ) used as the donor corneas.RHC-Ⅲ/PMPDSAH IPN,NGF PMPDSAH IPN and corneal grafts were lamellarly transplanted into the right eyes in RHC-Ⅲ/PMPDSAH IPN group,NGF PMPDSAH IPN group and allograft group respectively.The corneal transparency and neovascularization were examined and scored under the slim lamp and compared among three groups using Kraskal-Wallis H test.The corneal epithelization time was observed and compared among these three groups using one way analysis of variance and LSD-t test.The histological examination of corneas was performed at the 3rd day,1st and 2nd week,1 st,3rd and 6th month after the surgery.The immunohistochemistry was used to detect the expression of K3 in cornea at the 6th month.Results The grafts were well attached in RHC-Ⅲ/PMPDSAH IPN group,NGF PMPDSAH IPN group and allograft group,and no rejection reaction was found throughout 6-month following up.Compared with normal control group,no significant differences were found in the scores of corneal opacification and neovescularization in these three groups (x2 =4.34,P =0.23 ;x2 =2.60,P =0.46 ) at the 6th month.NGF PMPDSAH IPN group achieved reepithelialization in (4.97±0.63) days and was obviously shorted than that in RHC-Ⅲ/PMPDSAH IPN group and allograft group ( t =11.97,P =0.00; t =5.80,P =0.00).The re-epithelialization time in RHC-Ⅲ/PMPDSAH IPN was (6.86±0.71) days,and that of allograft group was (5.87±0.43 ) days,showing a significant difference ( t =6.32,P =0.00).Hematoxylin-eosin staining results demonstrated that implanted materials integrated into the host corneal tissue well and support corneal epithelialization.Part of the material degraded at the 2nd week and degraded completely 1 month later.Regular alignment and distribution of collagen fibers were seen in the regenerated cornea and were similar to those of the normal stroma in 6 months.Immunohistochemistry showed the positive expression of keratin-3 in corneal epithelial cells.Conclusions RHC-Ⅲ/PMPDSAH IPN has a good biocompatibility without toxicity to corneal tissue.Furthermore,NGF can promote the corneal wound-healing and re-epithelialization.The material can be used as safe and reliable corneal substitute after improving the mechanical strength.