Abstract
目的
制备负载威灵仙总皂苷(clematis total saponins,CTS)丝素蛋白微载体,探讨其复合软骨细胞后促进兔膝关节软骨缺损修复的效果。
方法
取5%丝素蛋白溶液与10 mg/mL CTS溶液、甘油混匀后,利用高压静电场结合冷冻干燥方法制备负载CTS丝素蛋白微载体,扫描电镜对样本表征并检测CTS累积释放量;同时制备丝素蛋白微载体。取6只4周龄新西兰大白兔膝关节软骨,分离培养软骨细胞并传代。取第3代细胞分别与两种微载体在微重力条件下共培养7 d,期间倒置相差显微镜及扫描电镜观察软骨细胞在微载体上黏附情况,细胞计数试剂盒8(cell counting kit 8,CCK-8)检测细胞增殖活性,并与正常培养细胞比较。取30只3月龄新西兰大白兔制备双侧膝关节软骨缺损模型后随机分为3组(n=20),A组膝关节软骨缺损不作任何处理,B、C组分别采用丝素蛋白微载体-软骨细胞复合物、负载CTS丝素蛋白微载体-软骨细胞复合物填充关节软骨缺损。术后12周取材,ELISA检测关节液基质金属蛋白酶9(matrix metalloproteinase 9,MMP-9)、MMP-13、MMP组织抑制因子1(tissue inhibitor of MMP 1,TIMP-1)水平;大体观察及组织学观察(HE、甲苯胺蓝染色)评估软骨缺损修复情况;Western blot检测Ⅱ型胶原及蛋白聚糖表达;组织学及诱导型一氧化氮合酶(inducible nitric oxide synthase,iNOS)免疫组织化学染色观察关节滑膜炎症程度。
结果
负载CTS丝素蛋白微载体呈类球形,直径主要在300~500 μm 之间,表面呈多孔结构,孔隙率达35.63%±3.51%;药物缓释检测示微载体中CTS可长期缓慢释放。微重力条件下随培养时间延长,两种微载体表面黏附的软骨细胞逐渐增多,培养24 h时软骨细胞增殖活性均较正常培养细胞提高(P<0.05),两种微载体间差异无统计学意义(P>0.05)。动物体内实验观察,与A、B组相比,C组关节液中MMP-9、MMP-13含量均降低(P<0.05),TIMP-1含量上调(P<0.05)。与A组相比,B、C组软骨缺损均有组织填充,且C组修复表面更完整,与周围软骨结合较好;组织学观察及Western blot检测显示B、C组国际软骨修复评分准则(ICRS)评分以及Ⅱ型胶原、蛋白聚糖相对表达量均优于A组,C组优于B组,差异均有统计学意义(P<0.05)。关节滑膜组织学观察显示,与A、B组相比,C组滑膜炎症细胞浸润及小血管增生减少,免疫组织化学染色示C组iNOS表达水平降低(P<0.05)。
结论
负载CTS丝素蛋白微载体具有良好的CTS缓释效果及生物相容性,在微重力条件下能促进共培养的软骨细胞增殖,植入体内后能促进兔膝关节软骨缺损修复。
Keywords: 软骨组织工程, 软骨修复, 丝素蛋白, 威灵仙总皂苷, 微重力, 细胞培养, 兔
Abstract
Objective
To prepare the silk fibroin microcarrier loaded with clematis total saponins (CTS) (CTS-silk fibroin microcarrier), and to investigate the effect of microcarrier combined with chondrocytes on promoting rabbit knee articular cartilage defects repair.
Methods
CTS-silk fibroin microcarrier was prepared by high voltage electrostatic combined with freeze drying method using the mixture of 5% silk fibroin solution, 10 mg/mL CTS solution, and glycerin. The samples were characterized by scanning electron microscope and the cumulative release amount of CTS was detected. Meanwhile, unloaded silk fibroin microcarrier was also prepared. Chondrocytes were isolated from knee cartilage of 4-week-old New Zealand rabbits and cultured. The 3rd generation of chondrocytes were co-cultured with the two microcarriers respectively for 7 days in microgravity environment. During this period, the adhesion of chondrocytes to microcarriers was observed by inverted phase contrast microscope and scanning electron microscope, and the proliferation activity of cells was detected by cell counting kit 8 (CCK-8), and compared with normal cells. Thirty 3-month-old New Zealand rabbits were selected to make bilateral knee cartilage defects models and randomly divided into 3 groups (n=20). Knee cartilage defects in group A were not treated, and in groups B and C were filled with the unloaded silk fibroin microcarrier-chondrocyte complexes and CTS-silk fibroin microcarrier-chondrocyte complexes, respectively. At 12 weeks after operation, the levels of matrix metalloproteinase 9 (MMP-9), MMP-13, and tissue inhibitor of MMP 1 (TIMP-1) in articular fluid were detected by ELISA. The cartilage defects were collected for gross observation and histological observation (HE staining and toluidine blue staining). Western blot was used to detect the expressions of collagen type Ⅱ and proteoglycan. The inflammatory of joint synovium was observed by histological staining and inducible nitric oxide synthase (iNOS) immunohistochemical staining.
Results
The CTS-silk fibroin microcarrier was spherical, with a diameter between 300 and 500 μm, a porous surface, and a porosity of 35.63%±3.51%. CTS could be released slowly in microcarrier for a long time. Under microgravity, the chondrocytes attached to the surface of the two microcarriers increased gradually with the extension of culture time, and the proliferation activity of chondrocytes at 24 hours after co-culture was significantly higher than that of normal chondrocytes (P<0.05). There was no significant difference in proliferation activity of chondrocytes between the two microcarriers (P>0.05).In vivo experiment in animals showed that the levels of MMP-9 and MMP-13 in group C were significantly lower than those in groups A and B (P<0.05), and the level of TIMP-1 in group C was significantly higher (P<0.05). Compared with group A, the cartilage defects in groups B and C were filled with repaired tissue, and the repaired surface of group C was more complete and better combined with the surrounding cartilage. Histological observation and Western blot analysis showed that the International Cartilage Repair Scoring (ICRS) and the relative expression levels of collagen type Ⅱ and proteoglycan in groups B and C were significantly better than those in group A, and group C was significantly better than group B (P<0.05). The histological observation showed that the infiltration of synovial inflammatory cells and hyperplasia of small vessels significantly reduced in group C compared with groups A and B. iNOS immunohistochemical staining showed that the expression of iNOS in group C was significantly lower than that in groups A and B (P<0.05).
Conclusion
CTS-silk fibroin microcarrier has good CTS sustained release effect and biocompatibility, and can promote the repair of rabbit cartilage defect by carrying chondrocyte proliferation in microgravity environment.
Keywords: Cartilage tissue engineering, cartilage repair, silk fibroin protein, clematis total saponins, microgravity, cell culture, rabbit
膝关节软骨是透明的无血管组织,一旦损伤难以自行修复[1]。目前膝关节软骨损伤治疗方式较多,但疗效均不理想[2]。以非甾体类抗炎药物为主的对症治疗,远期疗效不佳;以微骨折术等手术治疗后,修复组织以瘢痕组织、纤维软骨为主,失去了原生软骨特性且易发生退行性改变[3-4]。组织工程技术是一种具有应用潜力的软骨缺损修复方法[5]。设计并控制构建组织工程软骨的生物支架、生长因子等关键要素,以保持软骨细胞活性、增强支架软骨再生效率,是组织工程技术用于软骨修复的关键。
威灵仙为毛莨科植物威灵仙、棉团铁线莲或东北铁线莲的干燥根和根茎,能治疗骨关节炎[6]。威灵仙总皂苷(clematis total saponins,CTS)为威灵仙提取物,能促进软骨组织损伤修复,改善膝关节骨关节炎症状,发挥类生长因子作用[7-8]。丝素蛋白是从蚕茧中提取的天然蛋白,具有良好生物相容性,可作为软骨组织工程支架材料[9]。研究显示通过自交联方法,可以将丝素蛋白中不稳定的α-螺旋结构转化为β-折叠结构,使其具有不溶于水以及较高机械性能的优势,近年来已被广泛应用于构建药物缓释系统,而且低温条件下丝素蛋白的自组装对自身给药活性和生物相容性影响较小[10-12]。此外,丝素蛋白降解产物为多种氨基酸,可以作为细胞生长营养物质[13]。我们前期研究制备了负载CTS丝素蛋白微球,并在体外实验中搭载软骨细胞培养,结果显示其能维持软骨细胞表型[14]。本次研究在制备负载CTS丝素蛋白微载体基础上,于体外微重力条件下搭载软骨细胞进行扩增培养,而后植入兔膝关节软骨缺损处,探讨负载CTS丝素蛋白微载体复合软骨细胞修复软骨缺损的效果。
1. 材料与方法
1.1. 实验动物及主要试剂、仪器
4周龄雄性新西兰大白兔6只,体质量为(500±50) g;3月龄新西兰大白兔30只,雌雄各半,体质量(3.0±0.5)kg。实验动物均由南京市江宁区青龙山动物繁殖场提供。
FBS、L-DMEM培养基(BioInd公司,以色列);丝素蛋白溶液(Sigma-Aldrich公司,德国);Ⅱ型胶原酶(大连美仑生物技术有限公司);CTS提取物(西安奥晶科技发展有限公司);HE、甲苯胺蓝染色液(北京索莱宝科技有限公司);细胞计数试剂盒8(cell counting kit 8,CCK-8;南京诺唯赞生物科技股份有限公司);GAPDH、TGF-β、基质金属蛋白酶13(matrix metalloproteinase 13, MMP-13)抗体、诱导型一氧化氮合酶(inducible nitric oxide synthase,iNOS)抗体(武汉三鹰生物技术有限公司);Ⅱ型胶原抗体(Novus公司,美国);蛋白聚糖抗体(Thermo公司,美国);兔抗小鼠二抗(Affinity公司,美国);MMP-9、MMP-13、MMP组织抑制因子1(tissue inhibitor of MMP 1,TIMP-1)ELISA试剂盒(南京翼飞雪生物科技有限公司);DAB显色试剂盒(福州迈新生物技术开发有限公司)。
液动力聚焦细胞培养系统(Celltech公司,美国);微量注射泵(浙江史密斯医学仪器有限公司);冷冻干燥机(Labconco公司,美国);化学发光成像仪(上海天能科技有限公司);多功能酶标仪(PerkinElmer公司,美国);扫描电镜 (Hitachi公司,日本)。
1.2. 负载CTS丝素蛋白微载体的制备及观察
1.2.1. 微载体制备方法
参照本课题组既往采用方法,以高压静电场结合冷冻干燥方法制备负载CTS丝素蛋白微载体[14]。取5%丝素蛋白溶液,加入等体积10 mg/mL CTS溶液、甘油(丝素蛋白质量的30%)混匀后,转入微量注射泵中。将高压电发生器正、负极分别连接微量注射泵的注射器针头和液氮收集池。打开高压电发生器、微量注射泵,使混合液在静电场作用下逐滴滴入液氮收集池;制备参数:电压12~15 kV,注射针头直径0.45 mm,滴速1 mL/h。收集固化液滴并冷冻干燥,即获得不溶于水的负载CTS丝素蛋白微载体[15]。取5%丝素蛋白溶液、甘油(丝素蛋白质量的30%)制备混合液,同上法制备单纯丝素蛋白微载体。
1.2.2. 微载体形态观察
取负载CTS丝素蛋白微载体样本,体式显微镜观察后,喷金处理并扫描电镜观察微载体形态、大小及微观形貌。利用Image J软件计算微载体表面孔隙率。
1.2.3. 药物缓释测定
将负载CTS丝素蛋白微载体样本置于pH7.4 PBS中,密封置于37℃恒温震荡箱中缓慢摇动,分别于1、2、4、6、8、12、14、16、18 h及1、2、3、4、5、6、7、8、9、10 d 收集上清液0.1 mL,利用香草醛-高氯酸显色方法[16]检测CTS缓释浓度,计算累积释放量。
1.3. 微重力条件下负载CTS丝素蛋白微载体复合软骨细胞培养及观测
1.3.1. 软骨细胞培养及传代
取6只4周龄新西兰大白兔,空气栓塞法处死后无菌条件下分离膝关节,取关节透明软骨,剪碎至1 mm×1 mm×1 mm;置于0.2%Ⅱ型胶原酶37℃消化6 h,200 μm滤网过滤后,以300×g离心5 min,获得软骨细胞。将细胞接种至培养皿,以含10%FBS以及1%青霉素、链霉素混合液的L-DMEM培养基培养,隔2 d换液1次,待细胞长满瓶底70%~80%后传代,取第3代细胞用于实验。
1.3.2. 微重力条件下微载体复合软骨细胞培养及观测
① 培养方法:将5×106个软骨细胞分别与50 mg丝素蛋白微载体、负载CTS丝素蛋白微载体,置于液动力聚焦细胞培养系统培养仓中,调整转速为12 r/min,使培养仓内微载体既不接触培养仓壁,又在旋转过程中呈自由落体状态[17]。
② 观测指标:培养期间于倒置相差显微镜下观察两种微载体表面软骨细胞黏附情况;7 d时于扫描电镜下观察细胞黏附情况,然后收集两种微载体-软骨细胞复合物,经0.25%胰蛋白酶消化后收集软骨细胞;将细胞按1×105个/孔接种至96孔板,于37℃、5%CO2条件下培养24 h后,采用CCK-8法检测细胞增殖活性,以吸光度(A)值表示。以在培养皿中正常培养的软骨细胞作为对照。实验重复3次。
1.4. 负载CTS丝素蛋白微载体复合软骨细胞修复软骨缺损观测
1.4.1. 兔膝关节软骨缺损模型制备及分组
参照1.3方法于体外微重力条件下培养两种微载体-软骨细胞复合物,待培养12 d观察到软骨细胞贴满微载体表面时用于动物体内实验。
取30只3月龄新西兰大白兔,耳缘静脉注射戊巴比妥钠(30 mg/kg)麻醉后,在双后肢膝关节滑车表面用眼科环钻钻取直径3 mm、深3~4 mm圆孔,制备膝关节软骨缺损模型。将模型随机分为3组(n=20),分别为空白对照组(A组)、丝素蛋白微载体-软骨细胞复合物组(B组)、负载CTS丝素蛋白微载体-软骨细胞复合物组(C组)。A组:膝关节软骨缺损不作任何处理;B组:采用丝素蛋白微载体-软骨细胞复合物填充关节软骨缺损;C组:采用负载CTS丝素蛋白微载体-软骨细胞复合物填充关节软骨缺损。B、C组植入量以填满缺损处为标准。
术后兔单笼饲养,膝关节不固定。12周时采用耳缘静脉空气栓塞法处死全部动物,按照原切口入路获取膝关节样本进行以下观测。
1.4.2. 观测指标
① 关节液ELISA检测及大体观察:首先,在不打开膝关节腔条件下注入0.5 mL生理盐水,充分屈伸活动关节后,抽吸关节液,以300×g离心10 min,去除残留细胞;按照ELISA试剂盒说明书检测MMP-9、MMP-13、TIMP-1含量。然后打开关节腔,观察样本软骨缺损修复情况,根据国际软骨修复评分准则(ICRS)从膝关节软骨缺损填充度、表面光滑度、再生组织质地、完整性等方面进行评分[18]。
② 软骨组织学观察:将膝关节股骨远端部分置于4%多聚甲醛溶液固定48 h,然后置于10% EDTA中脱钙至少2周;梯度乙醇脱水,二甲苯透明,石蜡包埋,切取6 μm厚切片。常规HE及甲苯胺蓝染色,光镜下观察软骨缺损修复情况。
③ 软骨 Western blot检测:利用环钻按软骨缺损痕迹钻取样本软骨缺损处新生组织,加入RIPA裂解液球磨裂解,提取细胞总蛋白,经BCA法定量后,取等量蛋白稀释为同体积,加入上样缓冲液,混匀,沸水浴10 min,进行SDS-PAGE凝胶电泳,再经电转印,5%脱脂奶粉室温封闭2 h,一抗4℃孵育过夜,PBS漂洗后二抗室温孵育2 h,滴加ECL化学发光液,利用凝胶成像系统检测Ⅱ型胶原、蛋白聚糖表达,利用Image J软件测定条带灰度值,以目的蛋白与GAPDH比值作为其相对表达量。
④ 关节滑膜组织学及iNOS免疫组织化学染色观察:将膝关节滑膜置于4%多聚甲醛固定,石蜡包埋、切片。部分切片行HE染色观察组织炎症细胞浸润、血管增生等滑膜炎病理改变。其余部分切片经过水化、0.5%Triton X-100透化、3%H2O2灭活内源性过氧化物酶、10%BSA室温封闭 2 h;iNOS抗体(1∶100)4℃孵育过夜,二抗孵育后,按照DAB显色试剂盒说明进行显色,苏木素复染后封片,于光镜下观察并利用Image J软件计算积分吸光度(IA)值,作为iNOS表达水平。
1.5. 统计学方法
采用SPSS20.0统计软件进行分析。计量资料均符合正态分布,数据以均数±标准差表示。组间比较采用单因素方差分析,两两比较采用SNK检验;检验水准α=0.05。
2. 结果
2.1. 负载CTS丝素蛋白微载体表征观察
负载CTS丝素蛋白微载体呈类球形,直径主要在300~500 μm之间,占77.4%,形态较稳定、均一;微载体表面呈多孔结构,测量其孔隙率达35.63%±3.51%(图1a、b)。药物缓释检测显示CTS在 24 h内释放较快,24 h后释放速度减缓且稳定,10 d内每天释放量平均为0.307 mg,累积释放量见图1c。
图 1.
Characterization of CTS-silk fibroin microcarrier
负载CTS丝素蛋白微载体表征观察
a. 体式显微镜观察(×10);b. 扫描电镜观察(×1 000);c. CTS累积释放量
a. Stereomicroscope observation (×10); b. Scanning electron microscope observation (×1 000); c. Cumulative release amount of CTS from CTS-silk fibroin microcarrier
2.2. 微重力条件下微载体复合软骨细胞培养观察
随培养时间延长,两种微载体表面黏附的软骨细胞逐渐增多,且软骨细胞相互接触生长(图2)。CCK-8法检测微重力条件下培养24 h 后,丝素蛋白微载体及负载CTS丝素蛋白微载体上的软骨细胞增殖活性A值分别为2.06±0.13、2.09±0.13,较正常培养细胞(1.84±0.16)提高,差异有统计学意义(P<0.05);两种微载体间差异无统计学意义(P>0.05)。
图 2.
Observation of adhesion of chondrocytes to CTS-silk fibroin microcarrier under microgravity
微重力条件下软骨细胞在负载CTS丝素蛋白微载体上黏附情况观察
a、b. 共培养3、7 d倒置相差显微镜观察(×100); c. 共培养7 d扫描电镜观察(×400)
a, b. Observation under inverted phase contrast microscope after 3 and 7 days of co-culture, respectively (×100); c. Observation under scanning electron microscopy (×400)
2.3. 动物体内实验
2.3.1. 大体观察及关节液ELISA检测
与A、B组相比,C组MMP-9、MMP-13含量均降低,TIMP-1含量上调,差异均有统计学意义(P<0.05)。见表1。
表 1.
Comparison of MMP-9, MMP-13, and TIMP-1 contents between groups (n=20,
)
各组膝关节液MMP-9、MMP-13及TIMP-1含量比较(n=20,
)
| 组别
Group |
MMP-9
(μg/mL) |
MMP-13
(μg/mL) |
TIMP-1
(pg/mL) |
|
*与C组比较P<0.05
*Compared with group C, P<0.05 | |||
| A | 1.27±0.18* | 4.89±1.37* | 49.56±19.02* |
| B | 1.01±0.07* | 2.95±0.58* | 52.45±22.19* |
| C | 0.74±0.07 | 1.34±0.10 | 91.52±18.49 |
| 统计值
Statistic |
F=14.73
P<0.001 |
F=12.81
P=0.01 |
F=4.27
P=0.01 |
术后12周,A组膝关节软骨缺损未修复;B组软骨缺损有组织填充,但未完全修复,且修复表面不平整;C组软骨缺损修复表面更平整、与周围正常软骨组织界限模糊、结合紧密。见图3。A、B、C组ICRS评分分别为(2.0±0.7)、(8.0±0.6)、(10.4±1.1)分,组间比较差异均有统计学意义(P<0.05)。
图 3.
Gross observation of cartilage defect in each group at 12 weeks after operation
术后12周各组软骨缺损大体观察
a. A组;b. B组;c. C组
a. Group A; b. Group B; c. Group C
2.3.2. 软骨组织学观察
A组软骨缺损区域仅有少量疏松组织填充,几乎未形成新生软骨。B组可见明显组织填充软骨缺损区域,但软骨基质生成有限。C组可见软骨缺损中的新生组织含有大量软骨细胞,但细胞排列较紊乱;软骨基质沉积明显,与周边组织较一致。见图4。
图 4.
Histological observation of cartilage tissue in each group (×100)
各组软骨组织学观察(×100)
从左至右分别为A、B、C组 a. HE染色;b. 甲苯胺蓝染色
From left to right for groups A, B, and C, respectively a. HE staining; b. Toluidine blue staining
2.3.3. 软骨Western blot检测
A、B、C组Ⅱ型胶原蛋白相对表达量分别为0.521±0.081、0.833±0.099、1.139±0.136,蛋白聚糖分别为0.437±0.055、0.705±0.021、1.027±0.157。B、C组两种蛋白相对表达量均高于A组,C组高于B组,差异均有统计学意义(P<0.05)。见图5。
图 5.
Target protein expressions detected by Western blot assay
Western blot检测各组目的蛋白表达
1~3分别为A~C组
1-3 for groups A-C, respectively
2.3.4. 关节滑膜组织学及iNOS免疫组织化学染色观察
HE染色示A组滑膜炎症细胞浸润及小血管增生明显;与A组比较,B、C 组滑膜炎症细胞浸润与小血管增生均减轻,其中C组减轻程度更显著。iNOS免疫组织化学染色示A、B、C组iNOS表达水平分别为0.22±0.015、0.20±0.021、0.15±0.013,C组低于A、B组,差异有统计学意义(P<0.05)。见图6。
图 6.
Histological and iNOS immunohistochemical staining observations of synovial tissue in each group (×100)
各组关节滑膜组织学及iNOS免疫组织化学染色观察(×100)
从左至右分别为A、B、C 组 a. HE染色;b. iNOS免疫组织化学染色
From left to right for groups A, B, and C, respectively a. HE staining; b. iNOS immunohistochemical staining
3. 讨论
在构建组织工程软骨过程中,理想的生物支架除了能为软骨细胞提供黏附、生长、交互作用的三维结构环境外,还需要提供适当的生长因子来维持软骨细胞活性,这是软骨再生的关键[19]。
中药威灵仙具有“祛风湿,通经络”的作用,临床广泛用于膝关节骨关节炎治疗中。CTS为威灵仙主要活性成分,可以通过多种途径影响软骨细胞活性,多方面改善软骨修复微环境,包括降低氧化应激损伤防止关节软骨退化,靶向线粒体凋亡途径抑制软骨细胞凋亡等[20-22]。我们前期研究结果也显示威灵仙能够上调TGF-β表达,发挥类生长因子作用,促进软骨细胞基质分泌,提高细胞增殖活性[23]。本研究中,我们通过制备负载CTS丝素蛋白微载体,在微重力条件下搭载软骨细胞扩增培养,再将此复合物植入兔膝关节软骨缺损处,以实现CTS持续缓慢释放,提高组织工程软骨修复效率。
丝素蛋白已被证明是一种适用于软骨组织工程的生物材料,具备优良的生物安全性、可降解性,同时也可以用来递送脂溶性药物[24-26]。既往研究中丝素蛋白药物递送载体的制备多采用乳化法、脱溶法,制备过程中多种化学试剂的处理可能会造成药效活性的改变,且药物包封率很低[27-28]。本研究中,我们利用冻干技术结合丝素蛋白自交联方法制备载药微载体。该方法无需过多使用有机溶剂,避免了化学试剂毒性残留,能够更大程度保持CTS药效活性。同时为了给软骨细胞黏附生长提供三维结构,制备更加稳定、均一的丝素蛋白微载体,我们参照Drachuk等[11]的方法,利用微量注射泵在高压静电场作用下将包封有CTS的丝素蛋白溶液逐滴滴入液氮收集池固化。由此制备的负载CTS丝素蛋白微载体呈规则类球形,直径主要在300~500 μm范围,表面多孔隙,能够在至少10 d内缓慢释放CTS,提示其植入体内后能对软骨细胞产生长期影响。
相关研究显示软骨细胞在微重力环境下会进入悬浮状态并聚集成细胞簇,在微载体存在情况下会促进细胞自发黏附于微载体表面增殖[29]。利用此特点,我们将软骨细胞与制备的微载体在微重力条件下共培养。与平面皿培养方式相比,两种微载体不仅无细胞毒性,还能显著提高软骨细胞增殖活性,在体外成功构建了负载CTS丝素蛋白微载体-软骨细胞复合物。
最后,本研究通过兔膝关节软骨缺损模型来验证负载CTS丝素蛋白微载体促进软骨缺损修复的作用。结果显示植入12周后,B组软骨缺损获得一定程度修复,但修复表面不完整,软骨基质沉积有限,这可能与体外培养的软骨细胞移植入体内后表型退变相关。而C组软骨缺损区均形成致密有序的软骨样组织,并与周围组织融合较好,表面也较完整,提示CTS长期缓慢释放能够持续促进移植软骨细胞的表型维持,发挥了类生长因子作用,增强了支架-软骨细胞复合物体内软骨构建效率。
软骨损伤后原生软骨内稳态被打破,其中MMP与TIMP之间的动态平衡破坏是导致膝关节骨关节炎发生、发展的重要原因。MMP是一种能够降解细胞外基质的内肽酶,在软骨基质降解中发挥重要作用,而TIMP是阻断细胞外基质降解、抑制 MMP活性的分泌糖蛋白,它参与组织结构的建立与维持[30-31]。本研究结果显示与A、B组相比,C组MMP-9、MMP-13含量明显降低、TIMP-1含量提高,表明CTS有助于调节MMP与TIMP-1平衡,促进软骨损伤修复。此外,兔膝关节滑膜组织观测结果显示,植入12周后A、B组滑膜仍有明显炎症细胞浸润和血管增生,C组滑膜炎症细胞浸润减少,但仍有微血管增生;iNOS免疫组织化学染色显示,与A、B组相比,C组iNOS表达水平显著降低。这些结果均表明缓慢释放的CTS能够降低关节软骨损伤后滑膜炎症状态,改善软骨修复微环境,促进软骨损伤修复。
综上述,本研究成功制备了负载CTS丝素蛋白微载体,其具有良好的CTS缓释效果及生物相容性,在微重力条件下复合软骨细胞构建的复合物,能够改善关节损伤后炎症微环境,显著增强兔软骨修复效率。但是本研究构建的组织工程软骨失去了原生软骨结构,下一步将对支架进行优化;同时在膝关节复杂力学、化学信号作用下,CTS能否长期有效维持组织工程软骨修复质量也需进一步关注。
利益冲突 所有作者声明,在课题研究和文章撰写过程中不存在利益冲突;经费支持没有影响文章观点和对研究数据客观结果的统计分析及其报道
伦理声明 研究方案经南京中医药大学动物实验伦理委员会批准(201910A052);实验动物生产许可证号SCXK(沪)2018-0004,实验动物使用许可证号SYXK(苏)2018-0048
作者贡献声明 马勇、郭杨负责研究设计、数据整理;刘孟敏、汪志芳指导实验操作;涂鹏程负责支架载体构建及分析、数据收集、论文撰写;杨光露、孙杰、陈凯负责部分实验内容及数据分析;王礼宁、潘娅岚负责对文章涉及相关研究进展进行校阅
Funding Statement
国家自然科学基金面上项目(81673995);江苏高校优势学科(中西医结合)建设工程资助项目(苏政办发[2018]87号);江苏省研究生科研创新计划(KYCX17_1308、KYCX21_1683);2018年地方高校国家级大学生创新训练计划(201810315008)
National Natural Science Foundation of China (81673995); Projects Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (Integration of Chinese and Western Medicine)( [2018]87) ; Postgraduate Research & Practice Innovation Program of Jiangsu Province (KYCX17_1308, KYCX21_1683); Undergraduate Research & Practice Innovation Program of Jiangsu Province (201810315008)
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