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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

Histological validation of in vivo imaging.(A) There is a good correspondence between the distribution of transplanted cells as visualized by paraCEST and the histological marker for human cells (Human Nuclei Antigen, HNA). Indeed, the Eu (18 ppm) image indicated a fairly homogenous distribution of NSCs, which was paralleled by its histological validation using GFAP as a marker within the transplant area. Yb (97 ppm) imaging also truthfully reflects the macroscopic distribution of transplanted ECs, as detected by CD31. (B) To further validate the accuracy of the MR images, partially transparent histological overlays of transplanted cells (HNA) with NSCs (GFAP) and ECs (CD31) specific markers were co-registered based on landmark identification to the relevant MRI images. The images further highlight the regional specificity of the MR images as well as a correct mapping of relative cell distribution. (C) Further histological analyses indicated a morphological formation within the grafted area that reflects the emergence of a de novo neurovascular environment resembling structures observed in organoids. (D) Within this environment, the presence of Eu-HPDO3A in transplanted NSCs was also validated using its fluorescent properties.
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f7: Histological validation of in vivo imaging.(A) There is a good correspondence between the distribution of transplanted cells as visualized by paraCEST and the histological marker for human cells (Human Nuclei Antigen, HNA). Indeed, the Eu (18 ppm) image indicated a fairly homogenous distribution of NSCs, which was paralleled by its histological validation using GFAP as a marker within the transplant area. Yb (97 ppm) imaging also truthfully reflects the macroscopic distribution of transplanted ECs, as detected by CD31. (B) To further validate the accuracy of the MR images, partially transparent histological overlays of transplanted cells (HNA) with NSCs (GFAP) and ECs (CD31) specific markers were co-registered based on landmark identification to the relevant MRI images. The images further highlight the regional specificity of the MR images as well as a correct mapping of relative cell distribution. (C) Further histological analyses indicated a morphological formation within the grafted area that reflects the emergence of a de novo neurovascular environment resembling structures observed in organoids. (D) Within this environment, the presence of Eu-HPDO3A in transplanted NSCs was also validated using its fluorescent properties.

Mentions: A histological validation of in vivo MR images indicates that in vivo images truthfully represent the presence and distribution of transplanted human cells (Fig. 7A). Indeed, the T2 signal decrease due to the incorporation of the paraCEST agents resulted in an overall demarcation of implanted cells that corresponded to the distribution of human cells within the rat brain (Fig. 7B). Eu-HPDO3A consistently represented the distribution and regional patterning of implanted neural stem cells, whereas Yb-HPDO3A reflected the pattern of ECs. Histology and MRI overlays further demonstrate the dependability of in vivo images to report on the histological reality. Implanted cells were contained within the lesion cavity that is embedded within damaged tissue. However, as indicated on the paraCEST scans, human cells did not invade this tissue. A tissue patterning revealed on paraCEST scans as differences in regional distributions of NSCs and ECs resembled the generation of major vascular structures with neural patches, but there was no direct evidence of neurovascular environment forming yet. The cell density within the implant region exceeded that of surrounding healthy tissue, potentially reflecting that a too dense mixture of cells is being injected or that insufficient dispersion of cells into surrounding damaged tissue occurred (as the whole T2 hyperintense area was used to calculate the volume for injection). Finally, the presence of Eu-HPDO3A, as source of the paraCEST signal, was validated in human cells (Fig. 7D). These results demonstrate the feasibility to simultaneously image non-invasively two populations of cells that putatively occupy the same space in an in situ tissue engineering paradigm, but they also highlight the technical challenges that need to be addressed to make this approach more amenable to answer key biological questions.


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)

Histological validation of in vivo imaging.(A) There is a good correspondence between the distribution of transplanted cells as visualized by paraCEST and the histological marker for human cells (Human Nuclei Antigen, HNA). Indeed, the Eu (18 ppm) image indicated a fairly homogenous distribution of NSCs, which was paralleled by its histological validation using GFAP as a marker within the transplant area. Yb (97 ppm) imaging also truthfully reflects the macroscopic distribution of transplanted ECs, as detected by CD31. (B) To further validate the accuracy of the MR images, partially transparent histological overlays of transplanted cells (HNA) with NSCs (GFAP) and ECs (CD31) specific markers were co-registered based on landmark identification to the relevant MRI images. The images further highlight the regional specificity of the MR images as well as a correct mapping of relative cell distribution. (C) Further histological analyses indicated a morphological formation within the grafted area that reflects the emergence of a de novo neurovascular environment resembling structures observed in organoids. (D) Within this environment, the presence of Eu-HPDO3A in transplanted NSCs was also validated using its fluorescent properties.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4588587&req=5

f7: Histological validation of in vivo imaging.(A) There is a good correspondence between the distribution of transplanted cells as visualized by paraCEST and the histological marker for human cells (Human Nuclei Antigen, HNA). Indeed, the Eu (18 ppm) image indicated a fairly homogenous distribution of NSCs, which was paralleled by its histological validation using GFAP as a marker within the transplant area. Yb (97 ppm) imaging also truthfully reflects the macroscopic distribution of transplanted ECs, as detected by CD31. (B) To further validate the accuracy of the MR images, partially transparent histological overlays of transplanted cells (HNA) with NSCs (GFAP) and ECs (CD31) specific markers were co-registered based on landmark identification to the relevant MRI images. The images further highlight the regional specificity of the MR images as well as a correct mapping of relative cell distribution. (C) Further histological analyses indicated a morphological formation within the grafted area that reflects the emergence of a de novo neurovascular environment resembling structures observed in organoids. (D) Within this environment, the presence of Eu-HPDO3A in transplanted NSCs was also validated using its fluorescent properties.
Mentions: A histological validation of in vivo MR images indicates that in vivo images truthfully represent the presence and distribution of transplanted human cells (Fig. 7A). Indeed, the T2 signal decrease due to the incorporation of the paraCEST agents resulted in an overall demarcation of implanted cells that corresponded to the distribution of human cells within the rat brain (Fig. 7B). Eu-HPDO3A consistently represented the distribution and regional patterning of implanted neural stem cells, whereas Yb-HPDO3A reflected the pattern of ECs. Histology and MRI overlays further demonstrate the dependability of in vivo images to report on the histological reality. Implanted cells were contained within the lesion cavity that is embedded within damaged tissue. However, as indicated on the paraCEST scans, human cells did not invade this tissue. A tissue patterning revealed on paraCEST scans as differences in regional distributions of NSCs and ECs resembled the generation of major vascular structures with neural patches, but there was no direct evidence of neurovascular environment forming yet. The cell density within the implant region exceeded that of surrounding healthy tissue, potentially reflecting that a too dense mixture of cells is being injected or that insufficient dispersion of cells into surrounding damaged tissue occurred (as the whole T2 hyperintense area was used to calculate the volume for injection). Finally, the presence of Eu-HPDO3A, as source of the paraCEST signal, was validated in human cells (Fig. 7D). These results demonstrate the feasibility to simultaneously image non-invasively two populations of cells that putatively occupy the same space in an in situ tissue engineering paradigm, but they also highlight the technical challenges that need to be addressed to make this approach more amenable to answer key biological questions.

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