高活性脐带间充质干细胞干预老年树鼩衰老脾脏的作用与机制

Effect and mechanisms of highly active umbilical cord mesenchymal stem cells on aging spleen in elderly tree shrews

背景:脾脏具有储血、造血和免疫功能,随着年龄增长,脾脏结构退变、功能衰退引起免疫系统功能受损,进而加速机体衰老进程,而高活性脐带间充质干细胞治疗树鼩脾脏衰老尚未见报道。目的:探讨高活性脐带间充质干细胞对树鼩脾脏衰老的干预作用及机制。方法:从剖腹产的新生树鼩脐带组织中分离、培养和获得高活性脐带间充质干细胞,三系分化试剂盒检测成脂、成骨、成软骨分化能力,流式细胞术检测细胞周期和表面标志物。以感染复数值分别为100,120,140,160,180,200的吉凯基因绿色荧光蛋白转染第2代高活性脐带间充质干细胞,筛选最佳转染条件;转染后的第4代高活性脐带间充质干细胞尾静脉输注给老年治疗组树鼩,青年对照组和老年模型组不予特殊处理,治疗4个月时取脾脏组织,苏木精-伊红染色观察脾脏组织结构;β-半乳糖苷酶染色检测衰老相关半乳糖苷酶活性;免疫组织化学染色检测p21和p53蛋白表达水平;Ki67和PCNA免疫荧光染色检测细胞增殖活性;免疫荧光染色检测脾脏自噬蛋白分子Beclin1和APG5L/ATG5表达水平;活性氧荧光染色检测脾脏组织的活性氧含量;CD3免疫荧光染色检测总T淋巴细胞比例变化;酶联免疫吸附实验检测脾脏组织白细胞介素1β和转化生长因子β1分泌水平;DAPI复染细胞核观察绿色荧光蛋白标记的高活性脐带间充质干细胞在脾脏组织的分布情况。结果与结论:①高活性脐带间充质干细胞呈核小短梭形、鱼群样生长,G_(0)/G_(1)期占比大,具有向成脂、成骨和成软骨分化潜能。②感染复数为140且转染72 h为吉凯基因绿色荧光蛋白标记树鼩高活性脐带间充质干细胞的最佳条件。③与老年模型组相比,老年治疗组树鼩脾脏组织细胞排列紧密,白髓面积增加(P<0.01),红白髓界线清晰,生发中心占比无显著差异(P>0.05),脾脏组织衰老相关半乳糖苷酶活性水平降低(P<0.001),衰老蛋白分子p21和p53表达下调(P<0.001),增殖相关分子Ki67和PCNA表达上调(P<0.001,P<0.05),自噬相关分子Beclin1和APG5L/ATG5表达上调(P<0.001),活性氧含量降低(P<0.001),CD3^(+)T细胞比例增加(P<0.05),衰老相关分泌表型中白细胞介素1β分泌水平降低(P<0.001),转化生长因子β1分泌水平无显著差异(P>0.05)。与青年对照组相比,以上检测指标在老年治疗组中均有显著差异(P<0.05)。④冰冻组织切片观察可见老年治疗组树鼩脾脏组织中有绿色荧光蛋白标记的绿色荧光细胞。结果表明:静脉输注高活性脐带间充质干细胞可迁移至脾脏组织,抑制活性氧产生,下调衰老相关蛋白分子表达,诱导细胞自噬,促进细胞增殖,降低慢性炎症,进而改善脾脏组织结构和功能。

BACKGROUND:Spleen has the functions of blood storage,hematopoiesis,and immunity.With the increase of age,the structural degeneration and functional decline of spleen lead to the impairment of immune system function,thus accelerating the aging process of the body.The treatment of spleen aging in tree shrews with highly active umbilical cord mesenchymal stem cells has not been reported.OBJECTIVE:To explore the intervention effect and mechanism of highly active umbilical cord mesenchymal stem cells on spleen aging in tree shrews.METHODS:Highly active umbilical cord mesenchymal stem cells were isolated,cultured,and obtained from the umbilical cord tissue of newborn tree shrews by caesarean section.The differentiation abilities of adipogenesis,osteogenesis,and chondrogenesis were detected by three-line differentiation kit.Cell cycle and surface markers were detected by flow cytometry.The second generation of highly active umbilical cord mesenchymal stem cells were transfected with Genechem Green Fluorescent Protein with infection complex values of 100,120,140,160,180,and 200,respectively,to screen the best transfection conditions.After transfection,the fourth generation of highly active umbilical cord mesenchymal stem cells was injected into the tail vein of tree shrews in the elderly treatment group.The young control group and the aged model group were not given special treatment.After 4 months of treatment,the spleen tissue was taken and the structure of the spleen was observed by hematoxylin-eosin staining.β-Galactosidase staining was used to detect the activity of aging-related galactosidase.Immunohistochemical staining was used to detect the expression levels of p21 and p53 proteins.Ki67 and PCNA immunofluorescence staining was used to detect cell proliferation activity.Immunofluorescence staining was used to detect the expression levels of spleen autophagy protein molecules Beclin 1 and APG5L/ATG5.Reactive oxygen species fluorescence staining was used to detect the content of reactive oxygen species in spleen tissue.CD3 immunofluorescence staining was used to detect the change of the proportion of total T lymphocytes.The secretion levels of interleukin 1βand transforming growth factor β1 in spleen were detected by enzyme linked immunosorbent assay.The distribution of highly active umbilical cord mesenchymal stem cells labeled with green fluorescent protein in spleen tissue was observed by DAPI double staining of nucleus.RESULTS AND CONCLUSION:(1)Highly active umbilical cord mesenchymal stem cells grew in a short spindle shape with fish-like growth,with a large proportion of G_(0)/G_(1) phase,and had the potential to differentiate into adipogenesis,osteogenesis,and chondrogenesis.(2)Multiplicity of infection=140 and transfection for 72 hours were the best conditions for labeling tree shrews highly active umbilical cord mesenchymal stem cells with Genechem Green Fluorescent Protein.(3)Compared with the aged model group,in the aged treatment group,the spleen tissue cells of tree shrews were arranged closely,and the area of white pulp was increased(P<0.01);the boundary between red pulp and white pulp was clear;the proportion of germinal centers did not show statistically significant difference(P>0.05).The activity level of galactosidase related to spleen tissue aging was decreased(P<0.001),and the expression levels of aging protein molecules p21 and p53 were down-regulated(P<0.001).The expression levels of proliferation-related molecules Ki67 and PCNA were up-regulated(P<0.001,P<0.05);expression levels of autophagy-related molecules Beclin 1 and APG5L/ATG5 were up-regulated(P<0.001),and the content of reactive oxygen species decreased(P<0.001),and the proportion of CD3^(+)T cells increased(P<0.05).The secretion level of interleukin 1β in the aging-related secretion phenotype decreased(P<0.001);no significant difference was found in transforming growth factor β1 level(P>0.05).Compared with the young control group,the above indexes were significantly different in the elderly treatment group(P<0.05).(4)Green fluorescent cells labeled with green fluorescent protein were observed in spleen tissue of tree shrews the elderly treatment group by frozen tissue section observation.The results show that intravenous infusion of highly active umbilical cord mesenchymal stem cells can migrate to spleen tissue,inhibit the production of reactive oxygen species,down-regulate the expression of aging-related proteins,induce autophagy,promote cell proliferation,reduce chronic inflammation,and then improve the structure and function of spleen tissue.