不同放疗剂量对肌营养不良鼠骨髓干细胞移植的影响

目的　使用不同剂量γ射线对Duchenne型肌营养不良鼠 (mdx鼠 )照射 ,研究骨髓干细胞移植后mdx鼠缺失蛋白表达的情况。方法　将 18只 7～ 8周mdx鼠随机平均分为A、B、C 3组 ,依次给予 7Gy、7.5Gy、8Gyγ射线预处理 ;3天后行骨髓干细胞移植。移植骨髓干细胞取自 4～ 5周的C5 7BL/6鼠 ,体外培养 3d ,按 1 2× 10 7个细胞 /每只剂量移植给 3组预处理后的mdx鼠。连续观察受体鼠的移植物抗宿主病 (GVHD)程度 ;移植 12周后 ,检测受体鼠体内抗肌萎缩蛋白表达情况。结果　C组GVHD反应较明显 ;A、B、C 3组的股骨肌肌纤维dystrophin蛋白表达率分别为 8%、9%和 13 %。各组间缺失蛋白表达率有显著差异。结论　对 7～ 8周mdx鼠 ,给予不同剂量的γ射线预处理 ,骨髓干细胞移植后 ,8Gyγ射线表达最多 ,7Gy射线照射表达量最少 ;但 8Gyγ射线照射GVHD反应较明显。     

Duchenne肌营养不良模型鼠骨髓移植后dystrophin的表达

目的　观察Duchenne型肌营养不良模型鼠 (mdx鼠 )不同成分骨髓细胞移植后dystrophin的表达。方法　用体外培养的C57BL雄鼠的骨髓细胞、骨髓悬浮细胞、骨髓基质细胞分别经鼠尾静脉注射到放疗后的mdx鼠体内 ,动态观察受体雌性mdx鼠骨骼肌dystrophin的表达 ,并取受体mdx雌鼠血 ,用聚合酶链反应进行Sry基因检测。结果　骨髓细胞、悬浮细胞、基质细胞移植后 1～ 2个月 ,较少肌纤维表达dystrophin(<1 % ) ,3～ 4个月分别约有 7%、6 %、4 %的肌纤维表达dystrophin。Sry基因检测均扩增出受体雌鼠Y染色体上 449bp的DNA片段 ,提示供体细胞在受体内存活。结论　骨髓细胞、悬浮细胞、基质细胞分别移植到mdx鼠体内后 ,mdx鼠骨骼肌均有dystrophin的表达     

干细胞移植前TX小鼠有效放疗剂量的探索

目的探索TX小鼠适合的干细胞移植前的放疗剂量,为细胞移植治疗用于WD动物模型提供优良的预处理方案。方法雌性7~8周龄TX小鼠分组接受8Gy、7Gy、6Gy和5Gyγ射线放疗,后接受DL雄性小鼠骨髓干细胞移植,移植后追踪12周考察受体鼠的一般情况,移植物抗宿主病(GVHD)、肝功能、血清铜蓝蛋白和供体细胞在受体鼠肝脏存活情况。结果8Gy组和7Gy组100%、6Gy组50%动物于移植后2周内死亡;5Gy组动物12周内完全存活,且GVHD反应轻微,移植后12周时肝功能和铜蓝蛋白较6Gy组改善更明显;从供体细胞在受体鼠肝脏中的存活情况来分析,5Gy和6Gy组间相比无统计学意义。结论TX小鼠模型用于细胞移植研究的适合预处理放疗剂量是5Gy。     

骨髓干细胞移植治疗Duchenne型肌营养不良鼠的实验研究

目的　研究骨髓干细胞移植治疗Duchenne型肌营养不良鼠 (mdx鼠 )的效果。方法　取 4～ 5周龄昆明鼠骨髓干细胞 ,体外培养 3d ,静脉移植到 7Gyγ射线预处理 7～ 8周龄mdx鼠体内。临床监测受体鼠移植物抗宿主病 (GVHD)表现 ,并对移植 12周mdx鼠的运动功能、肌电生理、dystrophin蛋白表达情况进行检测。 结果　 5只 7Gy剂量放疗mdx鼠 ,静脉移植 4 8× 10 6骨髓干细胞 ,3个月后 ,肌电图指标有了部分改善 ;10 %肌纤维表达了dystrophin蛋白。结论　静脉移植同种非同系鼠骨髓干细胞治疗mdx鼠有效 ,显示骨髓干细胞移植治疗DMD有着理想的前景。     

人主动脉-性腺-中肾区基质细胞诱导胚胎干细胞分化为造血干细胞及体内造血重建*☆

背景：研究证实多种造血生长因子、基质细胞饲养层及其条件培养液可促进胚胎干细胞向造血干细胞分化。 目的：以人主动脉-性腺-中肾(aorta-gonad-mesonephros,AGM)区基质细胞为饲养层体外诱导小鼠胚胎干细胞分化为造血干细胞,并比较不同移植途径对造血干细胞体内造血重建能力的影响。 方法：将小鼠E14 胚胎干细胞诱导为拟胚体,采用Transwell非接触共培养体系在人AGM区基质细胞饲养层上诱导6 d,接种NOD-SCID小鼠检测体内致瘤性。再将诱导后的拟胚体细胞移植经致死量60Co γ射线辐照的BALB/C雌鼠,受鼠随机分为静脉移植组、骨髓腔移植组、照射对照组及正常对照组。 结果与结论：拟胚体细胞经人AGM区基质细胞诱导后Sca-1+c-Kit+细胞占(13.12±1.30)%。NOD-SCID小鼠皮下接种经人AGM区基质细胞诱导的拟胚体细胞可出现畸胎瘤,经骨髓腔接种未见肿瘤形成。静脉移植组动物全部死亡,骨髓腔移植组生存率为55.6%,移植后21 d外周血象基本恢复,存活受鼠检测到供体来源Sry基因。提示小鼠胚胎干细胞经人AGM区基质细胞诱导分化的造血干细胞通过骨髓腔移植安全并具有一定的造血重建能力。     

混合骨髓移植后过继免疫治疗小鼠白血病**☆

背景：急性白血病自体造血干细胞移植后复发率高,异基因造血干细胞移植后移植相关病死率高,混合造血干细胞移植及移植后过继免疫治疗有可能取长补短,提高疗效。 目的：观察自体骨髓混合H-2半相合异体骨髓移植后供体淋巴细胞输注+白细胞介素2治疗对小鼠白血病的疗效。 方法：将Balb/c小鼠经直线加速器照射3 Gy后分为白血病模型组、白血病模型照射组、混合移植组、自体骨髓移植组,均尾静脉注射5×105 K562(GFP+/NeoR+)或K562(GFP-/NeoR-)细胞。7 d后6 Gy照射,自体骨髓移植组移植自体骨髓细胞或联合白细胞介素2治疗;混合移植组移植小鼠自体骨髓细胞混合1/10的H-2半相合异体骨髓细胞后应用白细胞介素2或联合供体淋巴细胞输注治疗。4周后行小鼠外周血及骨髓细胞形态检查,外周血细胞亚群、GFP及NeoR基因测定,肝、脾匀浆细胞GFP和NeoR基因测定。 结果与结论：白血病模型组小鼠因骨髓造血功能衰竭于20 d内全部死亡,白血病模型照射组小鼠因造血功能衰竭于14 d内全部死亡;自体骨髓移植组、混合移植组均有多少不等小鼠无白血病存活超过28 d,且混合骨髓移植后及自体骨髓移植后应用白细胞介素2治疗可提高白血病小鼠长期无病生存率,在此基础上联合供体淋巴细胞输注可更进一步提高白血病小鼠长期无病生存率。     

移植物化学修饰减轻小鼠半相合骨髓移植后的急性移植物抗宿主病

背景: 甲氧基聚乙二醇是一种无免疫原性的兼性聚合分子，可以共价结合方式修饰各种蛋白质，减少其免疫原性。因此，在进行半相合造血干细胞移植时，若能用甲氧基聚乙二醇对移植物的T细胞进行化学修饰，阻断其激活的途径，就可能减轻移植物抗宿主病反应，提高移植成功率。 目的：构建小鼠半相合骨髓移植模型，观察甲氧基聚乙二醇修饰移植物对小鼠H2半相合骨髓移植后移植物抗宿主病的影响。 设计、时间及地点：随机化配对设计实验，于2003-03/11在解放军总医院医学动物实验中心和小儿内科实验室完成。 材料：纳入20只8~10周龄雄性近交系BALB/cH-2d小鼠作为供鼠，60只8~10周龄杂交获得的雌性CB6 F1 代H-2d/b小鼠作为受鼠。甲氧基聚乙二醇为美国Sigma公司产品。 方法：常规制备供鼠骨髓及脾细胞混合悬液。受鼠行总剂量8.0 Gy 60Co γ射线全身均匀照射，照射后随机分为3组，每组20只。照射对照组每只受鼠经尾静脉输入RPMI-1640培养基0.5 mL，单纯移植组照射后12 h内经尾静脉输入未处理的半相合供鼠骨髓及脾细胞混合悬液0.5 mL，修饰移植组照射后12 h内经尾静脉输入甲氧基聚乙二醇修饰的半相合供鼠骨髓及脾细胞混合悬液0.5 mL。 主要观察指标：移植后观察动物存活率、急性移植物抗宿主病理表现及存活小鼠的染色体核型。 结果：照射对照组小鼠均在2周内死亡；修饰移植组小鼠30 d存活率显著高于单纯移植组（75%，40%，χ2=5.01，P=0.025）。取死亡小鼠的爪垫皮肤、肝及小肠肠管作病理组织学检查，修饰移植组急性移植物抗宿主病病理表现减轻，Thomas 病理分级轻于单纯移植组。移植后75 d应用染色体C带显色法检测存活受鼠的嵌合体，证实为完全供者型植入。 结论：甲氧基聚乙二醇修饰移植物可明显减轻急性移植物抗宿主病，提高半相合骨髓移植存活率。     

小鼠脂肪源间充质干细胞在重型再生障碍性贫血中的应用

背景：骨髓间充质干细胞联合造血干细胞移植是最有希望解决造血重建缓慢的策略之一，但临床实施中，抽取骨髓进而分离、扩增间充质干细胞尚不能为大部分健康供者所接受。 目的：探讨小鼠脂肪源间充质干细胞对异基因重型再生障碍性贫血模型鼠造血功能的影响。 设计、时间及地点：细胞学体内实验，于2007-05/11在河南省肿瘤医院中心实验室完成。 材料：雄性6~8周龄BALB/c（H-2Kd）小鼠20只，雌性7~8周龄C57BL/6（H-2Kb）小鼠50只，均购于河南省实验动物中心。 方法：贴壁法体外分离培养20只雄性BALB/c小鼠脂肪源间充质干细胞；反复吹打20只雌性C57BL/6（H-2Kb）小鼠骨髓细胞，加入EDTA-NH4Cl液去除红细胞，即为骨髓有核细胞。剩余30只雌性C57BL/6（H-2Kb）小鼠均给予一次全身3.0 Gy 60Co-γ照射，照射后第4，5，6天皮下注射环磷酰胺及氯霉素，建立重型再生障碍性贫血模型。模型鼠随机分为3组，联合组经尾静脉输入骨髓有核细胞2×107个+脂肪源间充质干细胞3×106个，骨髓有核细胞组单纯输入骨髓有核细胞2×107个，对照组输入生理盐水0.2 mL，10只/组。 主要观察指标：定期检测外周血和股骨有核细胞数以及巨噬细胞/粒细胞集落形成单位数的变化，PCR法鉴定Y染色体，流式细胞仪检测移植小鼠骨髓及脾脏CD3和H-2Kd阳性表达情况。 结果：细胞移植后第2周，联合组外周血有核细胞数、股骨有核细胞数、巨噬细胞/粒细胞集落形成单位数均明显高于骨髓有核细胞组（P < 0.05），且随移植时间的延长，各种细胞数量逐渐恢复（P < 0.05）。细胞移植后第4周（即造血恢复期），联合组外周血可特异性地扩增Y染色体的SRY基因片段，移植小鼠骨髓及脾脏中CD3和H-2Kd双阳性细胞达6.66%，提示在受体小鼠体内有供体细胞的存在。 结论：脂肪源间充质干细胞能够重建重型再生障碍性贫血小鼠的造血功能，促进小鼠造血系统的恢复。     

Sca-1+造血干/祖细胞重建致死剂量辐射小鼠造血功能的作用**☆

背景：近年来,造血干细胞移植在国内外已广泛开展,移植的造血干细胞能否有效重建造血成为造血干细胞移植领域的研究热点问题之一。 目的：观察Sca-1+造血干/祖细胞(hematopoietic stem/progenitor cell,Sca-1+HSC/HPC)对造血衰竭小鼠造血功能重建的作用。 方法：雌性C57BL/6受体鼠给予致死剂量60Coγ射线照射后分2组,对照组：输注无菌PBS;移植组：移植免疫磁性分选法分离纯化的同系雄性C57BL/6小鼠Sca-1+HSC/HPC;检测受体鼠生存时间;外周血白细胞、红细胞比容、血小板的变化;脾湿质量及脾集落数;PCR检测Y染色体(Sry基因)表达确定受体小鼠重建造血的细胞来源。 结果与结论：移植组受体鼠30 d存活率、白细胞、红细胞比容、血小板、脾湿质量及脾集落数均明显高于对照组(P < 0.05);Y染色体PCR分析,证实雌性受体小鼠重建造血的细胞来源于雄性供体。提示Sca-1+HSC/HPC移植后能重建造血衰竭小鼠造血功能。     

骨髓基质干细胞在肌营养不良模型鼠中的分布及移植途径对分布的影响

目的研究干细胞在mdx鼠体内较长时间的动态分布以及移植途径对它的影响。方法用3H-TdR掺入标记骨髓基质干细胞,用4×106个/只静脉及腹腔移植放疗mdx鼠各30只,在24h、48h、2周、1个月、2个月、4个月时间点处死小鼠,取血、心、肝、脾、肺、肾、肌、脑、骨髓消化测定放射计数,计算%ID/g值。结果①静脉移植的mdx鼠脑、骨髓在2周才达到它自身的最高水平,心肌、骨骼肌4个月时达到高峰;而每个时间点各器官含量相比早期基本是肺、肝、骨髓分布多,心肌、肌肉2个月后仅次于骨髓。②腹腔移植mdx鼠血、肺、肾、肝、脾脏、脑到达它各自的高峰比静脉注射均有不同时间延迟,早期还是在骨髓、肝、肺分布多,肌肉2个月后仅次于骨髓。③心、肌肉、脑、骨髓含量静脉移植比腹腔移植高,均具有显著的统计学意义(P<0.01)。结论干细胞移植mdx鼠后4个月达高峰,移植途径对干细胞的分布有影响,3H-TdR能长时间动态观察干细胞分布。     

应用含标记基因K562细胞制备的小鼠白血病模型

背景：文献报道应用NOD/SCID及SCID小鼠可以建立移植性人白血病小鼠模型，但由于小鼠存在免疫缺陷，使得在自体干细胞移植及移植后相关过继免疫治疗方面的研究受到限制和影响。 目的：探索用SPF级Balb/c小鼠和转染GFP及NeoR基因的K562细胞株制备白血病模型的方法。 方法：实验分为5组，A、B组和C、D组分别经X射线照射2 Gy和3 Gy，24 h后取对数生长期的K562(GFP+/Neo+) 细胞， A、C组尾静脉注射2×106个/只；B、D组尾静脉注射5×106个/只；E组为正常对照组。观察小鼠生存时间，进行骨髓细胞及外周血白细胞分类，采用流式细胞仪测定GFP阳性细胞及PCR方法测定Neo基因。 结果与结论：实验各组在接种5~7 d时发病，分别于30，23，24，17 d内全部死亡；生存天均显著短于正常对照组(P < 0.01)。 体质量均较正常对照组显著下降(P < 0.05)。小鼠的白血病发病率为100%，无自发缓解。随接种细胞数量的增加和照射剂量的增加，小鼠的存活时间缩短，且外周血及骨髓中白血病细胞所占比例增加。流式细胞仪测定及PCR方法也证实了GFP+细胞和NeoR基因在肝、脾中的存在。结果证实 Balb/c小鼠经照射后从尾静脉注射K562细胞株可以制备获得白血病小鼠模型。     

Freshly dissociated fetal neural stem/progenitor cells do not turn into blood

Earlier studies suggested that stem cells from one somatic tissue may generate differentiated elements of another, embryologically unrelated, tissue after an exchange in their positions through transplantation. Two reports indicated that murine and human neural stem cells of clonogenic origin after in vitro expansion in growth factor-supplemented media, may sustain hematopoiesis when injected into sublethally irradiated mice. Here we investigated if freshly dissociated fetal neural cells (fNC) share the reported hemopoietic potential of in vitro expanded neural cells. In order to minimize the risk of hemopoietic contamination, donor cells were taken from mouse E10.5 developing brains, before completion of blood vessel ingrowth into the brain; 10(6) fNC derived directly from fetal brains of transgenic mouse expressing an enhanced version of the green fluorescent protein were injected into the tail vein or directly into the bone marrow of sublethally irradiated (6 Gy) C57B16 mice. After transplantation, the presence of donor-derived cells was assessed at different survival times by FACS analysis, PCR, and clonogenic stem cell assays on peripheral blood and bone marrow. While bone marrow-derived cells were detected from 2 weeks onward after grafting, none of the mice grafted with neural embryonic cells demonstrated any sign of transdifferentiation into hemopoietic cells up to 16 months after transplantation. Our data indicate that ability to transdifferentiate from neural into the hematopoietic phenotype, if present, is acquired only after in vitro expansion of neural stem/progenitor cells and it is not present in vivo.     

Hematopoietic stem cell and marrow stromal cell for spinal cord injury in mice

We compared the effects of hematopoietic stem cell and marrow stromal cell transplantation for spinal cord injury in mice. From green fluorescent protein transgenic mouse bone marrow, lineage-negative, c-kit- and Sca-1-positive cells were sorted as hematopoietic stem cells and plastic-adherent cells were cultured as marrow stromal cells. One week after injury, hematopoietic stem cells or marrow stromal cells were injected into the lesioned site. Functional recovery was assessed and immunohistochemistry was performed. In the hematopoietic stem cell group, a portion of green fluorescent protein-positive cells expressed glial marker. In the marrow stem cell group, a number of green fluorescent protein and fibronectin-double positive cells were observed. No significant difference was observed in the recovery between both groups. Both hematopoietic stem cells and marrow stromal cells have the potential to restore the injured spinal cord and to promote functional recovery.     

人骨髓及脐血单个核细胞移植构建人源化非肥胖糖尿病/重症联合免疫缺陷

背景：人源化非肥胖糖尿病/重症联合免疫缺陷(nonobese diabetic/severe combined immunodeficient,NOD/SCID)小鼠模型在生物及医学科学研究中被广泛应用,而提高人源化NOD/SCID小鼠模型中的人源化水平是研究者的迫切需要。 目的：探讨提高人源化NOD/SCID小鼠模型人源化水平的措施。 设计、时间及地点：随机对照动物实验,于2008-11/2009-01在广西医科大学实验动物中心及广西医科大学第一附属医院完成。 材料：雄性NOD/SCID小鼠14只,体质量(25.0±1.5)g;1例骨髓标本约6 mL(多部位分层次采集)取自健康志愿者;1例足月脐带血标本大约90 mL,取自广西医科大学第一附属医院产科,为健康产妇。 方法：无菌抗凝的正常骨髓及足月脐带血样本均在采集后6 h内处理。密度梯度离心法分离单个核细胞。将14只小鼠标号电脑随机分为5组：全身照射/环磷酰胺骨髓移植组(n=3),全身照射/环磷酰胺脐血移植组(n=3),全身照射骨髓移植组(n=3),全身照射脐血移植组(n=3),空白对照组(n=2)。将人骨髓或脐血单个核细胞分别移植给经不同方案和剂量预处理的各组小鼠,移植后给小鼠腹腔注射重组人粒-巨噬细胞集落刺激因子及重组人促红细胞生成素。 主要观察指标：各组小鼠输注的细胞数,小鼠存活情况并计算死亡率,移植6周后流式细胞仪检测小鼠骨髓及外周血人CD45+细胞比例。 结果：全身照射/环磷酰胺骨髓移植组、全身照射骨髓移植组和全身照射/环磷酰胺脐血移植组、全身照射脐血移植组小鼠输注人单个核细胞数分别为(0.656 0±0.008 9) ×106和(4.077 5±0.845 0)×106。全身照射/环磷酰胺组死亡率均为100%,全身照射组死亡率均为33.3%。全身照射后再加环磷酰胺,小鼠不能耐受;而全身照射剂量越大,死亡率越高,当达400 cGy时,死亡率100%。存活小鼠移植6周后,流式细胞仪检测小鼠骨髓中人CD45+细胞的比例,全身照射脐血移植组13号和6号小鼠分别为59.61%和21.46%,而全身照射骨髓移植组2号和8号小鼠其比例均为0,空白对照组小鼠比例均为0。而在13号小鼠骨髓细胞中,CD33+细胞比例为13.13%,GlyA+CD45-细胞比例为20.21%。 结论：要建立人源化NOD/SCID小鼠模型,所输入的造血干细胞数量一定要达到阈剂量,而在可耐受的范围内,尽可能提高预处理的强度,并使用人细胞因子可提高人源化NOD/SCID小鼠模型的人源化比例。     

Hematopoietic stem cell transplantation protects mice from lethal stroke

Stroke is a major cause of mortality and morbidity in the United States. The ideal therapeutic approach would minimize cell death and regenerate brain tissue. In order to investigate some questions that are related to such an approach, we have generated a mouse model in which we induce a stroke using the middle cerebral artery occlusion method. After 2 h occlusion followed by reperfusion, 99% of mice died within 8 days of stroke. Total bone marrow cell transplantation by intravenous injection revealed an optimal timing of cell transfer in two doses on days 1 (same day of surgery) and 2 after surgery. Moreover, intravenous injection of Sca1+ bone marrow cells (enriched in hematopoietic stem cells) showed a dose–response effect on survival. Surviving mice also had no signs of apparent paralysis or weakness. Tracking analysis using donor stem cells expressing LacZ revealed only few donor cells in the brain. We conclude that hematopoietic stem cell-rich Sca1+ bone marrow cell transplantation after stroke protects the brain of a sizeable portion of mice subjected to stroke and alleviate remarkably the resulting neurological morbidity in surviving mice.     

Radiation inhibition of mdx mouse muscle regeneration: Dose and age factors

A single hind limb was irradiated with 12, 18, 24, or 30 Gy in mdx and C57 mice aged 12, 21, or 42 days to determine regeneration inhibition dose-response curves in different aged dystrophic mice and to characterize radiation side-effects in normal mice. The anterior tibial muscle mass (8 weeks postirradiation) and percent central nucleated (i.e., regenerated) muscle fibers were measures of regeneration inhibition. Twenty-one-day-old mdx mice irradiated with 18 Gy had complete inhibition of muscle regeneration, but 30 Gy only partially blocked regeneration in mdx mice irradiated at 12 and 42 days in age. In working to produce a clinically relevant model for Duchenne dystrophy, it is crucial to regard mouse age as a major factor in determining radiation effects on mdx muscle regeneration.© 1995 John Wiley &Sons, Inc.     

Para-inflammation-mediated retinal recruitment of bone marrow-derived myeloid cells following whole-body irradiation is CCL2 dependent

Previous studies have shown that following whole-body irradiation bone marrow (BM)-derived cells can migrate into the central nervous system, including the retina, to give rise to microglia-like cells. The detailed mechanism, however, remains elusive. We show in this study that a single-dose whole-body γ-ray irradiation (8 Gy) induced subclinical damage (i.e., DNA damage) in the neuronal retina, which is accompanied by a low-grade chronic inflammation, para-inflammation, characterized by upregulated expression of chemokines (CCL2, CXCL12, and CX3CL1) and complement components (C4 and CFH), and microglial activation. The upregulation of chemokines CCL2 and CXCL12 and complement C4 lasted for more than 160 days, whereas the expression of CX3CL1 and CFH was upregulated for 2 weeks. Both resident microglia and BM-derived phagocytes displayed mild activation in the neuronal retina following irradiation. When BM cells from CX3CR1(gfp/+) mice or CX3CR1(gfp/gfp) mice were transplanted to wild-type C57BL/6 mice, more than 90% of resident CD11b(+) cells were replaced by donor-derived GFP(+) cells after 6 months. However, when transplanting CX3CR1(gfp/+) BM cells into CCL2-deficient mice, only 20% of retinal CD11b(+) cells were replaced by donor-derived cells at 6 month. Our results suggest that the neuronal retina suffers from a chronic stress following whole-body irradiation, and a para-inflammatory response is initiated, presumably to rectify the insults and maintain homeostasis. The recruitment of BM-derived myeloid cells is a part of the para-inflammatory response and is CCL2 but not CX3CL1 dependent.     

Covert persistence of mdx mouse myopathy is revealed by acute and chronic effects of irradiation.

To compare muscle fiber loss in young and old mdx mice, we have blocked regeneration in one leg with a high dose (18 Gy) of X-rays administered at two ages; 16 days, just prior to the onset of the myopathy, and 15 weeks, when the myopathy is considered to be quiescent. Mice were examined 4 days after irradiation to look for acute effects, or after 6 weeks to look for cumulative effects. Tibial length, muscle weight, muscle fiber size, fiber number and histological changes were recorded. Signs of acute damage to muscle fibers, leakage of Procion Orange dye into fibers and loss of creatine kinase from the fibers were also examined. Irradiation caused no acute or chronic damage to muscle fibers; on the contrary, in the youngest mdx mice, irradiation delayed the onset of the disease. However, in mdx but not in normal mice, there was a loss of muscle mass and fiber number in irradiated by comparison with the non-irradiated contra-lateral muscles. This loss, attributed to fiber necrosis in the absence of regeneration, was as great in animals irradiated at 15 weeks as in those irradiated at 16 days. Such persistence of muscle fiber necrosis contradicts the standard view of the mdx mouse and establishes it as a closer model of Duchenne muscular dystrophy than is generally appreciated.