Nondestructive Assessment of Glycosaminoglycans in Engineered Cartilages Using Hexabrix-Enhanced Micro-Computed Tomography

It is very useful to evaluate the content and 3D distribution of extracellular matrix non-destructively in tissue engineering. This study evaluated the feasibility of using micro-computed tomography (µCT) with Hexabrix to measure quantitatively sulfated glycosaminoglycans (GAGs) of engineered cartilage. Rabbit chondrocytes at passage 2 were used to produce artificial cartilages in polyglycolic acid scaffolds in vitro. Engineered cartilages were incubated with Hexabrix 320 for 20 min and analyzed via µCT scanning. The number of voxels in the 2D and 3D scanning images were counted to estimate the amount of sulfated GAGs. The optimal threshold value for quantification was determined by regression analysis. The 2D µCT images of an engineered cartilage showed positive correlation with the histological image of Safranin-O staining. Quantitative data obtained with the 3D µCT images of 14 engineered cartilages showed strong correlation with sulfated GAGs contents obtained by biochemical analysis (R² = 0.883, p < 0.001). Repeated exposure of engineered cartilages to Hexabrix 320 and µCT scanning did not significantly affect cell viability, total DNA content, or the total content of sulfated GAGs. We conclude that µCT imaging using Hexabrix 320 provides high spatial resolution and sensitivity to assess the content and 3D distribution of sulfated GAGs in engineered cartilages. It is expected to be a valuable tool to evaluate the quality of engineered cartilage for commercial development in the future.

Separation of sulfated urinary glycosaminoglycans by highresolution electrophoresis for isotyping of mucopolysaccharidoses in Malaysia

Mucopolysaccharidoses (MPS) are a group of inherited disorders caused by the defi ciency of specifi c lysosomal enzymes involved in glycosaminoglycans (GAGs) degradation. Currently, there are 11 enzyme defi ciencies resulting in seven distinct MPS clinical syndromes and their subtypes. Different MPS syndromes cannot be clearly distinguished clinically due to overlapping signs and symptoms. Measurement of GAGs content in urine and separation of GAGs using high-resolution electrophoresis (HRE) are very useful initial screening tests for isotyping of MPS before specifi c enzyme diagnostics. In this study, we measured total urinary GAGs by a method using dimethylmethylene blue (DMB), and followed by isolation and separation of GAGs using high resolution electrophoresis (HRE) technique. Of 760 urine samples analyzed, 40 have abnormal GAGs HRE patterns. Thirty-fi ve of these 40 cases have elevated urinary GAGs levels as well. These abnormal HRE patterns could be classifi ed into 4 patterns: Pattern A (elevated DS and HS; suggestive of MPS I, II or VII; 16 cases), Pattern B (elevated HS and CS; suggestive of MPS III; 17 cases), and Pattern C (elevated KS and CS; suggestive of MPS IV, 5 cases), and Pattern D (elevated DS; suggestive of MPS VI; 2 cases). Based on the GAGs HRE pattern and a few discriminating clinical signs, we performed selective enzymatic investigation in 16 cases. In all except one case with MPS VII, the enzymatic diagnosis correlated well with the provisional MPS type as suggested by the abnormal HRE pattern. Our results showed that GAGs HRE is a useful, inexpensive and practical fi rst-line screening test when MPS is suspected clinically, and it provides an important guide to further enzymatic studies on a selective basis.