In vivo imaging and evaluation of different biomatrices for improvement of stem cell survival

Abstract

Therapeutic effects from injection of stem cells are often hampered by acute donor cell death as well as migration away from damaged areas. This is likely due to the fact that injected cells do not have the physical and biochemical cues for ordered engrafment. Here we evaluate 3 common biomatrices (Matrigel, Collagen I, Purmatrix) that has the potential of providing suitable scaffolds needed to enhance stem cell survival. The longitudinal fate of transplanted stem cells was monitored by reporter imaging techniques.

Figure 1

Isolation and characterization of bone marrow derived mesenchymal stem cells from L2G85 transgenic mice (MSCs^Fluc+/eGFP+). (a) Morphology of MSCs^Fluc+/eGFP+ in brightfield and fluorescence microscopy. (b) MSCs^Fluc+/eGFP+ show robust correlation of firefly luciferase activities and cell numbers. Bioluminescence imaging was performed on varying numbers of MSCs^Fluc+/eGFP+ plated on 24-well plates. (c) MSCs^Fluc+/eGFP+ showed 87±8% GFP positive, 94±11% CD44, 90±5% CD90, 3±0.4% CD34, and 0.1±0.05% CD45. All samples were performed in triplicates. (d) MSCs^Fluc+/eGFP+ morphology after culturing in the presence of different biomatrices for 48 hours. The same culture condition and same cell number was tested for all group. Scale bars: 50 μm in panel a and 100 μm in panel d.

Figure 2

Bioluminescence imaging of transplanted MSCs^Fluc+/eGFP+ in living animals. (a) To assess longitudinal cell survival, animals were imaged for 5 months after subcutaneous injection of 5×10⁵ MSCs^Fluc+/eGFP+ mixed with PBS control, Matrigel, Collagen 1, Puramatrix, and mixture. (b) Quantification of BLI signals showed a drastic decrease of Fluc activities from day 2 to month 1. After that, the BLI signals in the Matrigel and mixture groups remained stable compared with the other three groups. BLI signals were all normalized to day 0 in each group. (c) Postmortem immunohistochemistry staining of eGFP by confocal fluorescence microscopy revealed more robust engraftment of MSCs^Fluc+/eGFP+ within the Matrigel and mixture groups compared to the PBS control and Collagen 1 groups, consistent with the noninvasive BLI data. Scale bars: 50 μm.