Effect Of PH On The Efficacy Of Fibroblast Growth Factor In Wound Repair

Background and Purpose:The pH value in the wound microenvironment directly or indirectly affects all the biochemical reactions that occur during skin wound healing.Currently,it is generally believed that lower pH levels,such as those found in normal skin,are beneficial for wound regeneration,while some studies have shown that alkaline microenvironments are,in fact,necessary for certain healing processes.The role of growth factors in promoting wound healing requires a specific microenvironment.In wound microenvironment of different pH,growth factors with different isoelectric points may have different effects.In this study,different GelMA hydrogels were synthesized to provide a specific pH and a slow and sustained release environment for acid-base fibroblast growth factors on acute full-thickness skin defect wounds of C57BL/6 mice.To explore the difference of acid-base FGF in wound repair under different ph conditions.Method and process:1.GelMA hydrogels containing aFGF or bFGF with different pH6.4,7.4 and 8.4 were synthesized,and their structures were observed by electron microscope,and their properties were evaluated by expansion ratio experiment and drug release experiment.2.Acute full-thickness skin defect wound of C57BL/6 mice was established,and the wound was treated with drugs and control.HE staining,Masson staining and immunohistochemical staining were used to evaluate the effect of a/bFGF on the healing speed and quality of acute wound in mice at different pH values.And on reepithelialization,collagen deposition,inflammation regulation,and angiogenesis.3.RNA-seq was used to analyze the differences of expression genes and signaling pathways in wounds treated with AFGF-loaded GelMA hydrogel with pH of 6.4 and 7.4,respectively.Results:1.Electron microscopy showed that the surface and interior of the freeze-dried hydrogel scaffold showed porous structure;The swelling ratio experiment showed that the hydrogel reached swelling equilibrium at about 3h,and the swelling rate was between 521%-548%,with no significant difference between the groups.The cumulative release curve showed that all the six hydrogels maintained a relatively long release time after a period of sudden release.The release amount of acid fibroblast growth factor in acidic environment was higher than that in neutral and alkaline environment,while the total release amount of basic fibroblast growth factor in hydrogels with different pH values showed no statistical difference.2.Animal experiments showed that aFGF had a better effect on wound reepithelialization than bFGF,and had a stronger effect on weakly acidic wound microenvironment.The density of collagen in acidic and alkaline environments was higher than that in neutral group,and 6.4-GelMA/bFGF was better than 6.4-GelMA/aFGF group.Immunohistochemistry showed that the effect of bFGF in promoting angiogenesis was better than that in aFGF group,and the inflammatory reaction in the six experimental groups appeared earlier and subsided earlier than that in the control group.aFGF has a good inhibitory effect on the inflammatory reaction of weak acid wound.3.RNAseq results showed that differentially expressed genes included Gpdl,Apold1,Kcne4,Epx,Sp7,Ucma,Gm12258,F830016B08Rik,Tnfsfl4,Gm15056,Gm12250,Gm12185 and lfitlbl1.These genes regulate endothelial cell differentiation,protein autoubiquitination and defense response,and their underlying signaling pathways are involved in wound healing.Conclusion:In this study,we found that aFGF and bFGF played similar roles in promoting wound healing under neutral and alkaline conditions.However,aFGF was significantly more stimulative than bFGF when the local pH at the wound site was adjusted to acidic conditions.Local acidic pH helps fibroblast growth factors play an important role in promoting wound contraction,granulation tissue formation,vascularization,and re-epithelialization.