Objective:To explore the repair effect of nucleus pulposus spherical cell clusters in the process of intervertebral disc degeneration and its potential therapeutic application.Methods:The degradation and rheological properties of SupraGel hydrogel were characterized, and the biocompatibility of spherical nucleus pulposus cell clusters in SupraGel hydrogel was tested by live-dead cytological staining. A caudal disc puncture degeneration model was established in 20 SD rats, and the rats were divided into groups and intervention measures: puncture of degenerated segment without intervention (positive control group), puncture of degenerated segment injection of SupraGel hydrogel (hydrogel group), puncture of degenerated segment injection of spherical cell clusters (cell cluster group), puncture of degenerated segment injection of SupraGel hydrogel loaded with spherical cell clusters (hydrogel + cell cluster group) and healthy segment (negative control group). X-rays and MRI examinations were performed at the 4th and 8th weeks after intervention, and the disc degeneration was evaluated according to the disc height index and Pfirrmann grading. HE staining, safranin O-fast green staining and COL-2 immunohistochemical staining were used to evaluate the changes in the disc structure and extracellular matrix.Results:The degradation residual rate of SupraGel hydrogel was 73.7% after 10 h, which showed excellent shear thinning and self-recovery properties. Nucleus pulposus cells could spontaneously aggregate in SupraGel hydrogel to form stable spherical cell clusters, which remained active on the 7th day. In the in vivo experiment, the intervertebral height index of the hydrogel + cell cluster group was 88.12%±4.55% and 74.13%±4.09% at 4 and 8 weeks after intervention, which were higher than those of the positive control group and hydrogel group, and lower than those of the negative control group, with statistically significant differences ( P<0.05); the Pfirrmann grades were 2.40±0.55 and 2.60±0.89, which were lower than those of the positive control group and hydrogel group at 4 weeks, and lower than those of the positive control group, hydrogel group and cell cluster group at 8 weeks, and higher than those of the negative control group, with statistically significant differences ( P<0.05); the morphological scores were 6.60±0.55 and 9.40±1.14, which were lower than those of the positive control group, hydrogel group and cell cluster group at 4 weeks, at the 8th week, the levels of collagen type II were lower than those of the positive control group, hydrogel group and cell cluster group, but higher than those of the negative control group, and the difference was statistically significant ( P<0.05). The optical density of type II collagen was 0.12±0.01 and 0.10±0.01, respectively, which were higher than those of the positive control group, hydrogel group and cell cluster group at the 4th week, and higher than those of the positive control group and hydrogel group at the 8th week, and the difference was statistically significant ( P<0.05). Conclusion:Nucleus pulposus spherical cell clusters can be successfully constructed and have been shown to have the effect of delaying degeneration in the rat intervertebral disc degeneration model.

Objective:To explore the repair effect of nucleus pulposus spherical cell clusters in the process of intervertebral disc degeneration and its potential therapeutic application.Methods:The degradation and rheological properties of SupraGel hydrogel were characterized, and the biocompatibility of spherical nucleus pulposus cell clusters in SupraGel hydrogel was tested by live-dead cytological staining. A caudal disc puncture degeneration model was established in 20 SD rats, and the rats were divided into groups and intervention measures: puncture of degenerated segment without intervention (positive control group), puncture of degenerated segment injection of SupraGel hydrogel (hydrogel group), puncture of degenerated segment injection of spherical cell clusters (cell cluster group), puncture of degenerated segment injection of SupraGel hydrogel loaded with spherical cell clusters (hydrogel + cell cluster group) and healthy segment (negative control group). X-rays and MRI examinations were performed at the 4th and 8th weeks after intervention, and the disc degeneration was evaluated according to the disc height index and Pfirrmann grading. HE staining, safranin O-fast green staining and COL-2 immunohistochemical staining were used to evaluate the changes in the disc structure and extracellular matrix.Results:The degradation residual rate of SupraGel hydrogel was 73.7% after 10 h, which showed excellent shear thinning and self-recovery properties. Nucleus pulposus cells could spontaneously aggregate in SupraGel hydrogel to form stable spherical cell clusters, which remained active on the 7th day. In the in vivo experiment, the intervertebral height index of the hydrogel + cell cluster group was 88.12%±4.55% and 74.13%±4.09% at 4 and 8 weeks after intervention, which were higher than those of the positive control group and hydrogel group, and lower than those of the negative control group, with statistically significant differences ( P<0.05); the Pfirrmann grades were 2.40±0.55 and 2.60±0.89, which were lower than those of the positive control group and hydrogel group at 4 weeks, and lower than those of the positive control group, hydrogel group and cell cluster group at 8 weeks, and higher than those of the negative control group, with statistically significant differences ( P<0.05); the morphological scores were 6.60±0.55 and 9.40±1.14, which were lower than those of the positive control group, hydrogel group and cell cluster group at 4 weeks, at the 8th week, the levels of collagen type II were lower than those of the positive control group, hydrogel group and cell cluster group, but higher than those of the negative control group, and the difference was statistically significant ( P<0.05). The optical density of type II collagen was 0.12±0.01 and 0.10±0.01, respectively, which were higher than those of the positive control group, hydrogel group and cell cluster group at the 4th week, and higher than those of the positive control group and hydrogel group at the 8th week, and the difference was statistically significant ( P<0.05). Conclusion:Nucleus pulposus spherical cell clusters can be successfully constructed and have been shown to have the effect of delaying degeneration in the rat intervertebral disc degeneration model.