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Simultaneous MR imaging for tissue engineering in a rat model of stroke.

Nicholls FJ, Ling W, Ferrauto G, Aime S, Modo M - Sci Rep (2015)

Bottom Line: Considering the varied lesion topology within each subject, the placement and distribution of cells within the lesion cavity is challenging.The use of multiple cell types to reconstruct damaged tissue illustrates the complexity of the process, but also highlights the challenges to provide a non-invasive assessment.The distribution of implanted cells within the lesion cavity and crucially the contribution of neural stem cells and endothelial cells to morphogenesis could be visualized simultaneously using two paramagnetic chemical exchange saturation transfer (paraCEST) agents.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Pittsburgh, PA.

ABSTRACT
In situ tissue engineering within a stroke cavity is gradually emerging as a novel therapeutic paradigm. Considering the varied lesion topology within each subject, the placement and distribution of cells within the lesion cavity is challenging. The use of multiple cell types to reconstruct damaged tissue illustrates the complexity of the process, but also highlights the challenges to provide a non-invasive assessment. The distribution of implanted cells within the lesion cavity and crucially the contribution of neural stem cells and endothelial cells to morphogenesis could be visualized simultaneously using two paramagnetic chemical exchange saturation transfer (paraCEST) agents. The development of sophisticated imaging methods is essential to guide delivery of the building blocks for in situ tissue engineering, but will also be essential to understand the dynamics of cellular interactions leading to the formation of de novo tissue.

No MeSH data available.


Related in: MedlinePlus

MRI detection of cells labeled via pinocytosis or electroporation.(A) Cells labeled with Yb-HPDO3A via electroporation (530 V, 100 μs pulse to give 9.5 mM pellet) (E) and pinocytosis (100 mM, 24 h to give 10.1 mM pellet) (P) were readily detected whereas unlabeled cells (U) did not produce a significant asymmetry. However, the asymmetry effect of Yb-HPDO3A is markedly attenuated after cell uptake compared to its effect in solution. (B) It was also evident that Yb-HPDO3A induced a dramatic shortening of T2 with a more significant shortening being evident upon pinocytotic incorporation. (C) Electroporation of Yb-HPDO3A showed a more significant asymmetry at 97 ppm than those labeled via pinocytosis. Notably, the asymmetry at 69 ppm was very much reduced. Z spectra were generated using image acquisitions at 66–71 and 95–100 ppm at 1 ppm per step, with reference images at 0 and −300 ppm. The remaining data points were fitted using smoothing splines.
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f3: MRI detection of cells labeled via pinocytosis or electroporation.(A) Cells labeled with Yb-HPDO3A via electroporation (530 V, 100 μs pulse to give 9.5 mM pellet) (E) and pinocytosis (100 mM, 24 h to give 10.1 mM pellet) (P) were readily detected whereas unlabeled cells (U) did not produce a significant asymmetry. However, the asymmetry effect of Yb-HPDO3A is markedly attenuated after cell uptake compared to its effect in solution. (B) It was also evident that Yb-HPDO3A induced a dramatic shortening of T2 with a more significant shortening being evident upon pinocytotic incorporation. (C) Electroporation of Yb-HPDO3A showed a more significant asymmetry at 97 ppm than those labeled via pinocytosis. Notably, the asymmetry at 69 ppm was very much reduced. Z spectra were generated using image acquisitions at 66–71 and 95–100 ppm at 1 ppm per step, with reference images at 0 and −300 ppm. The remaining data points were fitted using smoothing splines.

Mentions: Since paraCEST agents are highly pH sensitive, intracellular localization to the endosomes (as in the case of pinocytosis) and subsequent fusion with low pH lysosomes is likely to reduce detection. To assess this, ECs were labeled with Yb via pinocytosis (10.1 mM) and electroporation (9.5 mM). Both methods of incorporation produced cell-specific detectable signal changes on the CEST and T2 scan (Fig. 3A). A strong T2 shortening effect was evident for all labeled cells and this was more pronounced for those labeled through pinocytosis (Fig. 3B). Nevertheless, this T2 effect does not interfere with paraCEST imaging, provided a very short TE is used (<10 ms). Within cells, the 97 ppm exchange site revealed a greater asymmetry (10%) than 69 ppm (6%) (Fig. 3C). Despite the pinocytosis pellets having a 5% higher intracellular concentration, electroporated cells generated a 2% stronger signal at 97 ppm. Changes in microenvironment due to differential uptake therefore affect the paraCEST signal, but not in a dramatic fashion. Nevertheless, incorporation of agent into cells reduced signal for ~10 mM Yb concentration from 21% in solution to 6% in cells hinting at other factors that attenuate detection.


Simultaneous MR imaging for tissue engineering in a rat model of stroke.

Nicholls FJ, Ling W, Ferrauto G, Aime S, Modo M - Sci Rep (2015)

MRI detection of cells labeled via pinocytosis or electroporation.(A) Cells labeled with Yb-HPDO3A via electroporation (530 V, 100 μs pulse to give 9.5 mM pellet) (E) and pinocytosis (100 mM, 24 h to give 10.1 mM pellet) (P) were readily detected whereas unlabeled cells (U) did not produce a significant asymmetry. However, the asymmetry effect of Yb-HPDO3A is markedly attenuated after cell uptake compared to its effect in solution. (B) It was also evident that Yb-HPDO3A induced a dramatic shortening of T2 with a more significant shortening being evident upon pinocytotic incorporation. (C) Electroporation of Yb-HPDO3A showed a more significant asymmetry at 97 ppm than those labeled via pinocytosis. Notably, the asymmetry at 69 ppm was very much reduced. Z spectra were generated using image acquisitions at 66–71 and 95–100 ppm at 1 ppm per step, with reference images at 0 and −300 ppm. The remaining data points were fitted using smoothing splines.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588587&req=5

f3: MRI detection of cells labeled via pinocytosis or electroporation.(A) Cells labeled with Yb-HPDO3A via electroporation (530 V, 100 μs pulse to give 9.5 mM pellet) (E) and pinocytosis (100 mM, 24 h to give 10.1 mM pellet) (P) were readily detected whereas unlabeled cells (U) did not produce a significant asymmetry. However, the asymmetry effect of Yb-HPDO3A is markedly attenuated after cell uptake compared to its effect in solution. (B) It was also evident that Yb-HPDO3A induced a dramatic shortening of T2 with a more significant shortening being evident upon pinocytotic incorporation. (C) Electroporation of Yb-HPDO3A showed a more significant asymmetry at 97 ppm than those labeled via pinocytosis. Notably, the asymmetry at 69 ppm was very much reduced. Z spectra were generated using image acquisitions at 66–71 and 95–100 ppm at 1 ppm per step, with reference images at 0 and −300 ppm. The remaining data points were fitted using smoothing splines.
Mentions: Since paraCEST agents are highly pH sensitive, intracellular localization to the endosomes (as in the case of pinocytosis) and subsequent fusion with low pH lysosomes is likely to reduce detection. To assess this, ECs were labeled with Yb via pinocytosis (10.1 mM) and electroporation (9.5 mM). Both methods of incorporation produced cell-specific detectable signal changes on the CEST and T2 scan (Fig. 3A). A strong T2 shortening effect was evident for all labeled cells and this was more pronounced for those labeled through pinocytosis (Fig. 3B). Nevertheless, this T2 effect does not interfere with paraCEST imaging, provided a very short TE is used (<10 ms). Within cells, the 97 ppm exchange site revealed a greater asymmetry (10%) than 69 ppm (6%) (Fig. 3C). Despite the pinocytosis pellets having a 5% higher intracellular concentration, electroporated cells generated a 2% stronger signal at 97 ppm. Changes in microenvironment due to differential uptake therefore affect the paraCEST signal, but not in a dramatic fashion. Nevertheless, incorporation of agent into cells reduced signal for ~10 mM Yb concentration from 21% in solution to 6% in cells hinting at other factors that attenuate detection.

Bottom Line: Considering the varied lesion topology within each subject, the placement and distribution of cells within the lesion cavity is challenging.The use of multiple cell types to reconstruct damaged tissue illustrates the complexity of the process, but also highlights the challenges to provide a non-invasive assessment.The distribution of implanted cells within the lesion cavity and crucially the contribution of neural stem cells and endothelial cells to morphogenesis could be visualized simultaneously using two paramagnetic chemical exchange saturation transfer (paraCEST) agents.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Pittsburgh, PA.

ABSTRACT
In situ tissue engineering within a stroke cavity is gradually emerging as a novel therapeutic paradigm. Considering the varied lesion topology within each subject, the placement and distribution of cells within the lesion cavity is challenging. The use of multiple cell types to reconstruct damaged tissue illustrates the complexity of the process, but also highlights the challenges to provide a non-invasive assessment. The distribution of implanted cells within the lesion cavity and crucially the contribution of neural stem cells and endothelial cells to morphogenesis could be visualized simultaneously using two paramagnetic chemical exchange saturation transfer (paraCEST) agents. The development of sophisticated imaging methods is essential to guide delivery of the building blocks for in situ tissue engineering, but will also be essential to understand the dynamics of cellular interactions leading to the formation of de novo tissue.

No MeSH data available.


Related in: MedlinePlus