Fabrication of the composite scaffolds for bone regeneration and verification of their value in muscle pouch osteogenic activity in rats
10.3760/cma.j.cn501098-20240308-00197
- VernacularTitle:复合骨再生支架的构建及其促大鼠肌袋成骨活性的价值
- Author:
Ming ZHENG
1
;
Qiang ZHOU
;
Jixing YE
;
Zongxin LI
;
Yaopeng ZHANG
;
Xiang YAO
;
Xueping WEN
;
Nan WANG
;
Dianming JIANG
Author Information
1. 重庆医科大学附属第三医院骨与创伤中心，重庆 401120
- Keywords:
Silk fibroin;
Bone morphogenetic proteins;
Tissue scaffolds;
Bone regeneration
- From:
Chinese Journal of Trauma
2024;40(7):635-646
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To fabricate the composite scaffolds for bone regeneration with silk fibroin (SF), bacterial cellulose nanofibers (BCNR) and hydroxyapatite (HAp) and evaluate their osteogenic activity.Methods:HAp particles, BCNR and bone morphogenetic protein-2 (BMP2) were added into SF aqueous solution in turn, poured into molds of different sizes after being mixed evenly and processed at -25 ℃ for 24 hours to obtain frozen molds, and the composite scaffolds were frozen-dried by freezing-drying machine. The composite scaffolds with different mass ratios of SF and BCNR were divided into groups A (2∶1), B (4∶1) and C (6∶1), and the inactive composite scaffolds without BMP2 fell into group D. The surface morphology and pore structure of the scaffolds were detected by scanning electron microscopy. The porosity of the scaffolds was measured by mercury intrusion porosimeter. The stress-strain curve was obtained by using the universal material testing machine to compress the scaffolds, with which their compressive strength and Young′s modulus were analyzed. Immortalized mouse embryonic fibroblasts (iMEF) were inoculated on the composite scaffolds of group A, B, C and D. At 4 and 8 days after cell inoculation, the proportion of alive and dead cells in each group was detected by cell survival/death staining; the cell counting kit-8 (CCK-8) was used to detect cell proliferation activity in each group; the positive staining cells were detected in each group by alkaline phosphatase (ALP) staining; the ALP activity was observed in each group with ALP activity detection. A total of 15 female SD rats were selected to establish osteogenesis models with ectopic muscle bag. The composite scaffolds implanted with different SF/BCNR mass ratios and the inactive composite scaffolds without BMP2 fell into group A′ (2∶1), B′ (4∶1), C′ (6∶1) and D′ respectively, and a sham operation group was set at the same time, with 3 rats in each groups. In the sham operation group, the muscle bag and skin were sutured without scaffold implantation after the incision of skin, the blunt separation of the quadriceps muscle, and the formation of muscle bag in the muscle. In the other four groups, the corresponding scaffolds were implanted in the muscle bag and the muscle bag and skin were sutured. X-ray examination was performed at 2 and 4 weeks after operation to observe the osteogenesis in each group. At 4 weeks after operation, the implanted scaffolds and tissue complexes were collected by pathological tissue sectioning, HE staining and Masson staining, and for observing the osteogenesis by in each group. Immunohistochemical staining was also performed on the tissue sections to observe the expression of osteogenic markers type I collagen (COL1) and osteopontin (OPN) in each group.Results:Scanning electron microscopy showed that the lamellar and micropore structures of group B were more regular and uniform than those of groups A and C. The porosity rate analysis showed that the porosity rates of groups B and C were (89.752±1.866)% and (84.257±1.013)% respectively, higher than that of group A [(81.171±1.268)%] ( P<0.05 or 0.01), with the porosity rate of group C lower than that of group B ( P<0.01). The mechanical property test showed that the compressive strengths of groups B and C were (0.373±0.009)MPa and (0.403±0.017)MPa respectively, higher than that of group A [(0.044±0.003)MPa] ( P<0.01), and the Young′s moduli of groups B and C were (7.413±0.094)MPa and (9.515±0.615)MPa respectively, higher than that of group A [(1.881±0.036)MPa] ( P<0.01), with the compressive strength and Young′s modulus of group C higher than those of group B ( P<0.05 or 0.01). The cell survival/death staining showed that the number of dead cells of group B was significantly smaller than that of groups A, C and D at 4 days after cell inoculation, and that group B had the most living cells and the fewest dead cells at 8 days after cell inoculation. The results of CCK-8 experiment showed that at 4 days after cell inoculation, the cell proliferation activity of groups A and B was 0.474±0.009 and 0.545±0.018 respectively, higher than 0.394±0.016 of group D ( P<0.01); the cell proliferation activity of group C was 0.419±0.005, with no significant difference from that of group D ( P>0.05), while the cell proliferation activity of groups A and C were both lower than that of group B ( P<0.01). At 8 days after cell inoculation, the cell proliferation activity of group B was 1.290±0.021, higher than 1.047±0.011 of group D ( P<0.01); the cell proliferation activity of group C was 0.794±0.032, lower than that of group D ( P<0.01); the cell proliferation activity of group A was 1.086±0.020, with no significant difference from that of group D ( P>0.05); the cell proliferation activity of groups A and C was lower than that of group B ( P<0.01). At 4 and 8 days after cell inoculation, ALP staining showed that more positive cells were found in groups A, B and C when compared with group D, and more positive cells were found in group B than in groups A and C. At 4 days after cell inoculation, the ALP activity detection showed that the ALP activity of groups A, B and C was 1.399±0.071, 1.934±0.011 and 1.565±0.034 respectively, higher than 0.082±0.003 of group D ( P<0.01), while the ALP activity of groups A and C was lower than that of group B ( P<0.01). At 8 days after cell inoculation, the cell activity of groups A, B and C was 2.602±0.055, 3.216±0.092 and 2.145±0.170 respectively, higher than 0.101±0.001 of group D ( P<0.01), while the ALP activity of groups A and C was lower than that of group B ( P<0.01). X-ray examination results showed that at 2 weeks after operation, no obvious osteogenesis was observed in the sham operation group, group D′, A′ and C′, while it was observed in group B′. At 4 weeks after operation, obvious osteogenesis was observed in group A′, B′ and C′, with significantly more osteogenesis in group B′ than in the other two groups, while there was no obvious osteogenesis in the sham operation group and group D′. At 4 weeks after operation, the HE staining and Masson staining showed that a large number of uniformly distributed new bone tissue was formed in group B′, while only a small amount of new bone tissue was found locally in groups A′ and C′, and only part of new tissue was found to grow in group D′ with no obvious new bone tissue observed. The maturity of new bone tissue formed in group B′ was higher than that in group A′ and C′. Immunohistochemical staining showed more COL1 and OPN positive staining in group B′ when compared with groups A′ and C′. The expression intensity analysis of COL1 and OPN showed that in groups A′, B′ and C′, the expression intensity of COL1 was 2.822±0.384, 22.810±2.435 and 12.480±0.912 respectively and the expression intensity of OPN was 1.545±0.081, 5.374±0.121 and 2.246±0.116 respectively, with higher expression intensity of COL1 and OPN in groups B′ and C′ than that in group A′ ( P<0.01) and lower expression intensity of COL1 and OPN in group C′ than that in B′ group ( P<0.01). Conclusions:The composite scaffold for bone regeneration is successfully fabricated with SF, BCNR and HAp. The composite scaffold with a mass ratio of SF to BCNR of 4∶1 has uniform pore structure, high porosity, good mechanical properties and biocompatibility, excellent pro-osteogenic properties in vitro, as well as excellent osteo-inductivity and osteo-conductivity.
