BACKGROUND:The absence of blood vessels in tendon tissue makes tendon repair challenging.Therefore,improving tendon healing and raising the efficacy of stem cell and other therapeutic cell transplantation after tendon damage have become hotspots for research in both clinical and scientific contexts. OBJECTIVE:The stem cells and gelatin microcarrier scaffold were joined to form tissue engineered stem cells.Human umbilical cord mesenchymal stem cells cultured in gelatin microcarriers were used to investigate the therapeutic impact and mode of action on tendinopathy healing in rats in vitro and In vivo. METHODS:(1)In vitro cell experiments:After seeding human umbilical cord mesenchymal stem cells with three-dimensional gelatin microcarriers,the cell vitality and survival were assessed.Human umbilical cord mesenchymal stem cells conventionally cultured were cultured as controls.(2)In vivo experiment:Adult SD rats were randomly assigned to normal group,tendinopathy group,2D group(tendinopathy+conventional culture of human umbilical cord mesenchymal stem cells),and 3D group(tendinopathy+gelatin microcarrier three-dimensional culture of human umbilical cord mesenchymal stem cells),with 6 rats in each group.Four weeks after therapy,animal behavior tests and histopathologic morphology of the Achilles tendon was examined. RESULTS AND CONCLUSION:(1)In vitro cell experiments:the seeded human umbilical cord mesenchymal stem cells on gelatin microcarriers showed high viability and as time went on,the stem cell proliferation level grew.Compared with the control group,3D stem cell culture preserved cell viability.(2)In vivo experiment:Following a 4-week treatment,the 3D stem cell culture group showed a significant improvement in both functional recovery of the lower limbs and histopathological scores when compared to the tendinopathy group.The 2D stem cell culture group also showed improvement in tendinopathy injury,but its effect is not as much as the 3D stem cell culture group.(3)The outcomes demonstrate that human umbilical cord mesenchymal stem cells cultured with three-dimensional gelatin microcarrier can promote the repair and regeneration of tendon injury tissue,and the repair effect is better than that of conventional human umbilical cord mesenchymal stem cells.

BACKGROUND:Most rotator cuff injuries occur in the supraspinatus tendon.Clinical treatment of rotator cuff injuries is very limited due to the lack of blood vessels and the complex anatomical structure of the rotator cuff.The rapid development of tissue engineering technology and stem cell biology has brought new hope for improving the quality of tendon repair.OBJECTIVE:To prepare human umbilical cord mesenchymal stem cells/gelatin methacrylate composite scaffolds by bio-3D printing technology to observe the effect of this scaffold on repairing rotator cuff injury.METHODS:(1)In vitro cell assay:The gelatin microcarrier was prepared.The tissue engineered stem cells were constructed by inoculating human umbilical cord mesenchymal stem cells on the surface of gelatin microcarrier.Gelatin methacrylate hydrogel printing ink was prepared.Tissue engineered stem cells were re-suspended with gelatin methacrylate hydrogel printing ink and put into the bio-ink container of 3D printer for printing.Human umbilical cord mesenchymal stem cells/gelatin methacrylate composite scaffold was obtained after 5 minutes of blue light irradiation and curing.The activity of human umbilical cord mesenchymal stem cells in scaffolds was detected by dead/alive staining and CCK-8 assay.(2)In vivo animal experiments:A random block design method was used to randomly assign 24 SD rats to 4 groups with 6 rats in each group.No treatment was given in the normal group.The rotator cuff injury model of supratinatus tendon tear was established in the rotator cuff injury group,the simple scaffold group,and the cellular scaffold group.The gelatin methacrylate scaffold and human umbilical cord mesenchymal stem cell/gelatin methacrylatecomposite scaffold were implanted into the tendon injury after the model was made in the simple scaffold group and the cellular scaffold group,respectively.Four weeks after operation,behavioral tests and histopathological morphology observation of supraspinatus tendon of rotator cuff were performed.RESULTS AND CONCLUSION:(1)In vitro cellular assay:The dead/alive staining showed that gelatin microcarrier could reduce the damage of human umbilical cord mesenchymal stem cells caused by 3D printing process.With the extension of culture time,the survival rate of human umbilical cord mesenchymal stem cells increased in the scaffold.The results of CCK-8 assay showed that with the extension of culture time,the activity of human umbilical cord mesenchymal stem cells in the scaffold did not change significantly.(2)In vivo animal experiments:Behavioral test results showed that compared with rotator cuff injury group and simple scaffold group,cellular scaffold group significantly improved limb motor function.The results of hematoxylin-eosin and Masson staining of rotator cuff supraspinatus tendon showed that compared with rotator cuff injury group and simple scaffold group,the muscle fiber arrangement in the cellular scaffold group was more regular;there was no obvious inflammatory cell infiltration,and the percentage of collagen volume decreased.The results of immunofluorescence staining showed that the expression levels of interleukin 6 and tumor necrosis factor α in the rotator cuff supraspinatus tendon were significantly decreased in the cellular scaffold group compared with the rotator cuff injury group and the simple scaffold group.(3)The results showed that bio-3D-printed cell scaffolds encapsulating human umbilical cord mesenchymal stem cells/gelatin methacrylate could promote tissue repair and regeneration of rotator cuff injuries.

BACKGROUND:Most rotator cuff injuries occur in the supraspinatus tendon.Clinical treatment of rotator cuff injuries is very limited due to the lack of blood vessels and the complex anatomical structure of the rotator cuff.The rapid development of tissue engineering technology and stem cell biology has brought new hope for improving the quality of tendon repair.OBJECTIVE:To prepare human umbilical cord mesenchymal stem cells/gelatin methacrylate composite scaffolds by bio-3D printing technology to observe the effect of this scaffold on repairing rotator cuff injury.METHODS:(1)In vitro cell assay:The gelatin microcarrier was prepared.The tissue engineered stem cells were constructed by inoculating human umbilical cord mesenchymal stem cells on the surface of gelatin microcarrier.Gelatin methacrylate hydrogel printing ink was prepared.Tissue engineered stem cells were re-suspended with gelatin methacrylate hydrogel printing ink and put into the bio-ink container of 3D printer for printing.Human umbilical cord mesenchymal stem cells/gelatin methacrylate composite scaffold was obtained after 5 minutes of blue light irradiation and curing.The activity of human umbilical cord mesenchymal stem cells in scaffolds was detected by dead/alive staining and CCK-8 assay.(2)In vivo animal experiments:A random block design method was used to randomly assign 24 SD rats to 4 groups with 6 rats in each group.No treatment was given in the normal group.The rotator cuff injury model of supratinatus tendon tear was established in the rotator cuff injury group,the simple scaffold group,and the cellular scaffold group.The gelatin methacrylate scaffold and human umbilical cord mesenchymal stem cell/gelatin methacrylatecomposite scaffold were implanted into the tendon injury after the model was made in the simple scaffold group and the cellular scaffold group,respectively.Four weeks after operation,behavioral tests and histopathological morphology observation of supraspinatus tendon of rotator cuff were performed.RESULTS AND CONCLUSION:(1)In vitro cellular assay:The dead/alive staining showed that gelatin microcarrier could reduce the damage of human umbilical cord mesenchymal stem cells caused by 3D printing process.With the extension of culture time,the survival rate of human umbilical cord mesenchymal stem cells increased in the scaffold.The results of CCK-8 assay showed that with the extension of culture time,the activity of human umbilical cord mesenchymal stem cells in the scaffold did not change significantly.(2)In vivo animal experiments:Behavioral test results showed that compared with rotator cuff injury group and simple scaffold group,cellular scaffold group significantly improved limb motor function.The results of hematoxylin-eosin and Masson staining of rotator cuff supraspinatus tendon showed that compared with rotator cuff injury group and simple scaffold group,the muscle fiber arrangement in the cellular scaffold group was more regular;there was no obvious inflammatory cell infiltration,and the percentage of collagen volume decreased.The results of immunofluorescence staining showed that the expression levels of interleukin 6 and tumor necrosis factor α in the rotator cuff supraspinatus tendon were significantly decreased in the cellular scaffold group compared with the rotator cuff injury group and the simple scaffold group.(3)The results showed that bio-3D-printed cell scaffolds encapsulating human umbilical cord mesenchymal stem cells/gelatin methacrylate could promote tissue repair and regeneration of rotator cuff injuries.