Study On Injectable Granular Hydrogel Loaded Platelet Rich Plasma To Repair Rabbit Knee Joint Cartilage Injury

PurposeStudy on the effect of tannic acid cross-linked gelatin microspheres granular hydrogel scaffold(Gel/TA-PRP)loaded with platelet rich plasma(PRP)on rabbit knee joint cartilage injury,and to verify the injectable,adhesive and antioxidant properties of the scaffoldand.The gross observation and histological evaluation of rabbit knee cartilage injury were carried out.MethodsGranular hydrogel materials were prepared by hydrogen bonding between tannic acid and gelatin microspheres.The microstructure,rheological properties,extrusion properties,adhesion and oxidation resistance of the granular hydrogel were evaluated.PRP was prepared by double centrifugation from the blood of New Zealand white rabbits.PRP was loaded onto granular hydrogel and Gel/TA-PRP was prepared.Thirty six healthy New Zealand white rabbits were randomly divided into four groups:control group A(blank group),control group B(Gel/TA group),control group C(PRP group)and experimental group D(Gel/TAPRP group),with 9 rabbits in each group.All experimental animals underwent left femoral trochlear cartilage injury modeling surgery.At the 4th,8th and 12th weeks after operation,three experimental animals in each group were killed by air embolism.The newborn cartilage was evaluated by gross observation,hematoxylin eosin staining(HE),safranin Ofast green(SO)and immunohistochemistry(IHC).ResultsThe microstructures of granular hydrogel were observed by scanning electron microscope.It was found that the hydrogel was indeed assembled by microsphere aggregation.After introducing PRP,we can still find a large number of pores inside the hydrogel,which provide good protection for material exchange and cell migration.The relationship between frequency and modulus is evaluated by rheology,and it is confirmed that the hydrogel system is a flexible granular hydrogel system.The higher the TA concentration is,the higher the storage modulus of the hydrogel is,and it is confirmed that the hydrogel is an extruded hydrogel system.With the increase of shear rate,the viscosity of the system continues to decrease,showing a typical shear thinning performance.This characteristic shows that the viscosity of the system decreases during injection,which is conducive to the injection operation.Macroscopic adhesion test and lap shear test showed that the hydrogel had good adhesion properties.With the increase of TA concentration,the adhesive strength of the hydrogel has been increased.Quantitative detection of fluorescence intensity further indicated that TA introduced by granular hydrogel can clear ROS.In animal experiments,The gross observation and scoring system(ICRs)score was showed at 4 weeks,8 weeks and 12 weeks that(4 weeks:blank group:0.33±0.33,Gel/TA:0.56 ± 0.19,PRP group:2.00± 0.33,Gel/TA-PRP group:2.11 ± 0.19,8 weeks:blank group:0.78 ± 0.39;Gel/TA group:2.78 ± 0.51;PRP group:3.33 ± 0.33;Gel/TA-PRPgroup:4.33 ±0.67,12 weeks:blank group:1.44 ± 0.51;Gel/TA group:4.67 ± 0.67;PRP group:6.22 ±0.51;Gel/TA-PRP group:10.11 ± 0.39),Gel/TA-PRP scaffold has the strongest ability to repair cartilage defects in vivo,Better than the other three groups.Gel/TA scaffold has a positive effect on the repair of cartilage injury.Loading PRP can enhance its cartilage regeneration ability.The modified O’Driscoll histologic score was showed at 4 weeks,8 weeks and 12weeks that(4 weeks:blank group:1.22 ± 0.19;Gel/TA group:2.78 ± 0.69;PRP group:7.33 ± 0.33;Gel/TA-PRP group:10.11 ± 0.69;8 weeks:blank group:1.89 ± 0.69;Gel/TA group:7.78 ±0.96;PRP group:10.56 ± 1.07;Gel/TA-PRP group:14.11 ± 0.69;12 weeks:blank group:3.78 ± 0.39;Gel/TA group:12.22 ± 0.69;PRP group:14.78±0.69;Gel/TA-PRP group:20.89± 0.509)Gel/TA-PRP scaffold promoted more powerful hyaline cartilage regeneration compared with the other three groups.Gel/TA scaffold has a positive effect on hyaline cartilage regeneration.Loading PRP can enhance its hyaline cartilage regeneration ability,which further shows that PRP placed in Gel/TA scaffold t enhances the repair ability of cartilage injury.ConclusionPRP composite tannic acid cross-linked gelatin microsphere granular hydrogel is a potential ideal material for repairing cartilage damage.The experimental results show that the system has stable antioxidant,tissue adhesion and injectable properties.Animal experiments in vivo,HE staining,SO staining and IHC results confirm that the scaffold can promote regeneration of cartilage in cartilage injury.