Magnetic Resonance Analysis of Connective Tissue and Muscle

结缔组织和肌肉的磁共振分析

• 批准号: 8335965
• 负责人: Richard Spencer
• 金额: $ 7.83万
• 依托单位: NATIONAL INSTITUTE ON AGING
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8335965
• 关键词: Berlex brand of ferumoxides; Biochemical; Biological Markers; Body Weight; Cartilage; Cartilage Matrix; Cattle; Cells; Charge; Chondrocytes; Connective Tissue; Creatine; Defect; Encapsulated; Engineering; Ethylene Oxide; Evaluation; Exclusion; FDA approved; Gadolinium; Glycosaminoglycans; Goals; Health; Histology; Hydrogels; Injectable; Investigation; Iron; Label; Laboratories; Link; Lipids; Location; Magnetic Resonance; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Measurement; Measures; Metabolic; Methods; Modality; Muscle; Obesity; Phenotype; Procedures; Process; Production; Risk; Sampling; Staging; System; Techniques; Therapeutic; Tissue Engineering; Tissues; Transfection; Work; cartilage development; density; gadolinium oxide; human subject; implantation; improved; interest; iron oxide; lipid metabolism; novel; novel strategies; particle; polysulfated glycosaminoglycan; research study; tissue culture; two-dimensional

In one specific project, we sought to assess the reliability in measurement of evolving sulfated glycosaminoglycan (GAG) content in a clinically applicable tissue engineered cartilage system using magnetic resonance imaging (MRI). Samples of the hydrogel, poly(ethylene oxide) diacrylate (PEODA) were used to encapsulate bovine chondrocytes ( 2.4 million cells/ sample). The fixed charge density (FCD) of the developing cartilage was determined using the MRI gadolinium exclusion method. MRI experiments were performed on samples following 9, 16, 29, 36, 43 and 50 days of incubation. Samples from these timepoints were subsequently analyzed via biochemical procedures in order to correlate the MRI-derived FCD measurements with the true GAG content in the tissue. Histological sections of the samples were also processed to reveal temporal differences in the GAG concentration. We found a strong correlation (R2 = 0.85) between FCD and GAG content was determined up to 36 days. However, when extended to 50 days, the correlation decreased significantly (R2 = 0.54). From this, we conclude that FCD of chondrocyte-encapsulated hydrogel constructs correlate well with true GAG content during the first 36 days of incubation. This study demonstrates that MRI-derived FCD measurements can be reliably interpreted in the early stage evaluation ( 5 weeks) of injectable cartilage tissue engineering systems. In further work, we sought to define the distribution of cells within tissue engineered constructs. This is difficult to study through non-destructive means, such as would be required after implantation. However, cell labeling with iron-containing particles may prove to be a useful approach to this problem, since regions of such labeled cells have been shown to be readily detectable using magnetic resonance imaging. In this study, we used the FDA-approved superparamagnetic iron oxide (SPIO) agent, Feridex, in combination with transfection agents to label and visualize with MRI chondrocytes in two different tissue engineered constructs. Correspondence between labeled cell location as determined by MRI and by histology was established. The phenotype, viability and production of major cartilage matrix constituents were found to be unaffected by the SPIO-labeling process. We believe that this method of visualizing and tracking chondrocytes may be useful in the further development of cartilage tissue engineering therapeutics. Lastly, MR is also an excellent modality for detailed metabolic investigations in human subject. We were interested in the link between body weight, lipid metabolism, and health risks. This is poorly understood and difficult to study. Magnetic resonance spectroscopy (MRS) permits non-invasive investigation of lipid metabolism. We extended existing two-dimensional MRS techniques to permit quantification of intramyocellular (IMCL) and extramyocellular (EMCL) lipid compartments and their degree of unsaturation in human subjects, and correlated these results with BMI. Using muscle creatine (Cr) for normalization, a statistically significant (p < 0.01) increase in IMCL/Cr with BMI (n=8 subjects per group) was observed, with values of 5.9 1.7 (BMI < 25), 10.9 1.82 (25 < BMI< 30) and 13.1 0.87 (BMI > 30). Similarly, the degree of IMCL unsaturation decreased significantly (p < 0.01) with BMI, with respective values of 1.51 0.08, 1.30 0.11, and 0.90 0.14. We conclude that important aspects of lipid metabolism can be evaluated with 2-dimensional MRS and propose that degree of unsaturation measured noninvasively may serve as a biomarker for lipid metabolic defects associated with obesity.

在一个特定的项目中，我们试图评估使用磁共振成像（MRI）在临床适用的组织工程软骨系统中测量不断发展的硫化糖胺聚糖（GAG）含量的可靠性。 水凝胶，聚乙烷氧化二丙酸酯（PEODA）的样品用于封装牛软骨细胞（240万细胞/样品）。使用MRI Gadolium排除法确定发育软骨的固定电荷密度（FCD）。在9、16、29、36、43和50天孵育之后，对样品进行了MRI实验。随后通过生化程序分析了这些时间点的样品，以将MRI衍生的FCD测量与组织中的真实GAG含量相关联。还处理了样品的组织学切片，以揭示GAG浓度的时间差异。我们发现FCD和GAG含量之间存在很强的相关性（R2 = 0.85），并确定长达36天。但是，当延长到50天时，相关性显着下降（R2 = 0.54）。从此，我们得出的结论是，在孵育的前36天，软骨细胞包含的水凝胶构建体的FCD与真实的GAG含量很好地相关。这项研究表明，在可注射软骨组织工程系统的早期评估（5周）中，可以可靠地解释MRI衍生的FCD测量值。 在进一步的工作中，我们试图定义组织工程结构中细胞的分布。 这很难通过非破坏性手段进行研究，例如植入后需要进行。然而，用含铁颗粒的细胞标记可能被证明是解决此问题的一种有用方法，因为已经证明使用磁共振成像可以很容易地检测到此类标记的细胞的区域。在这项研究中，我们使用了由FDA批准的超帕磁铁氧化铁（SPIO）剂Feridex与转染剂结合使用，以在两个不同的组织结构中与MRI软骨细胞可视化并与MRI软骨细胞可视化。建立了由MRI和组织学确定的标记细胞位置之间的对应关系。发现主要软骨基质成分的表型，生存能力和生产不受SPIO标记过程的影响。我们认为，这种可视化和跟踪软骨细胞的方法可能有助于软骨组织工程治疗剂的进一步发展。 最后，MR还是人类受试者详细代谢研究的绝佳方式。 我们对体重，脂质代谢和健康风险之间的联系感兴趣。 这是很众所周知的，难以研究。磁共振光谱（MRS）允许对脂质代谢的无创研究。我们扩展了现有的二维MRS技术，以允许量化细胞内（IMCL）和肌外（EMCL）脂质室及其在人类受试者中的不饱和程度，并将这些结果与BMI相关。使用肌肉肌酸（CR）进行归一化，观察到IMCL/CR具有BMI（每组n = 8个受试者）的统计学意义（P <0.01），值为5.9 1.7（BMI <25），10.9 1.82（25 <BMI <30）和13.1 0.87（BMI> 30）。同样，IMCL不饱和度的程度显着降低（p <0.01），其值分别为1.51 0.08、1.30 0.11和0.90 0.14。我们得出的结论是，可以通过二维MRS评估脂质代谢的重要方面，并提出，非饱和度测得的不饱和度可以作为与肥胖相关的脂质代谢缺陷的生物标志物。