Improvement Approaches On Gelatin Scaffold And Bmscs Targeting Bone Tissue Engineering

Cell scaffolds and seed cells are two very important parts in bone tissue engineering.For the cell scaffold part,a cell scaffold that could be firmly combined with in-situ tissue,could realize rapid regeneration of bone tissue,and could maintain good mechanical properties during bone repair is now required for bone tissue repair.Therefore,this paper improves the commonly used hydrogel scaffolds in bone tissue engineering.Methacrylated gelatin(GelMA)and hydroxyapatite nanowires(HANW)were combined to obtain the GelMA/HANW composite cryogel and hydrogel.These two kinds of scaffolds were used to compare the surface topography,cell compatibility,mechanical properties,and bone repair ability in vivo to identify if they meet the needs of bone regeneration.For the seed cell BMSCs part,electrical stimulation(ES)is a method that can promote osteogenic differentiation of BMSCs.In order to better understand the effect of electrical stimulation on BMSCs differentiation,in this study,the electrical stimulation device was improved,and two conductive substrates were prepared by compounding poly-L-lactic acid(PLLA)with multi-walled carbon nanotubes(MWCNTs)and polymerizing polypyrrole(PPy)on the surface of polyethylene terephthalate(PET).The electrical stimulation device and the conductive substrate were combined to select the appropriate electrical stimulation parameters.The effects of electrical stimulation,conductive substrate and differentiation induction medium on the differentiation behaviors of BMSCs were systematically explored.Main achievements are summarized as follows:(1)As a bone tissue engineering scaffold,compared with GelMA/HANW composite hydrogels,the improved GelMA/HANW cryogels show unique advantages.The internal pore size of the GelMA/HANW composite hydrogel is only 36.4±8.1 ?m,at the meantime,the composite hydrogel is brittle and fragile in compression test.However,the GelMA/HANW composite cryogel has a interconnected porous structure,with its internal pore size reaching 143.7±32.1 ?m.Moreover,the cryogels can withstand 60%strain compression deformation,has good cyclic compression stability and excellent shape recovery ability.The results of cell culture and rat calvarial defects regeneration experiments show that the GelMA/HANW hydrogel hinders the migration and spreading of cells due to its small pore size.In addition,the hydrogel is not conducive to the growth of neo-bone,and the hydrogel scaffold breaks up alongside longer implantation time.In contrast,the GelMA/HANW composite cryogel facilitates the expansion and growth of cells and tissues,and can form a tight bond with the surrounding bone tissue.After 12 weeks of implantation,the cryogel scaffold can still maintain a stable 3D porous structure,and provide mechanical support and a suitable microenvironment for bone regeneration.(2)As for the study of seed cells,compared with traditional subcultured BMSCs,the BMSCs pretreated with electrical stimulation and subsequently being subcultured,show enhanced osteogenic differentiation potential.Under the optimized electrical stimulation parameters(on PPy/PET conductive substrate,10 Hz,50 mV/mm,1 h/day),BMSCs are incubated in regular medium,osteogenic induction medium and chondrogenic induction medium,respectively.After electrical stimulation,passage was performed to detect the expression levels of genes related to osteogenic differentiation and chondrogenic differentiation.The results show that BMSCs pretreated with electrical stimulation in regular medium have been enhanced on their osteogenic differentiation potential after passage.Likewise,BMSCs pretreated with electrical stimulation in osteogenic induction medium demonstrate reduced osteogenic differentiation potential after passage.The effect of electrical stimulation on the cartilage differentiation potential of BMSCs was not significant,but the BMSCs cultured in chondrogenic induction medium display improved chondrogenci differentiation potential after passage.The above results show that the improvements of gelatin scaffold and seed cell BMSCs have been achieved,which would like to promote osteogenic differentiation and bone tissue regeneration.The combination of the improved scaffold and BMSCs is expected to significantly accelerate the regeneration and functional reconstruction of bone defects...