In vivo fluorescence imaging of muscle cell regeneration by transplanted EGFP-labeled myoblasts.
In vivo fluorescence imaging (FLI) enables monitoring fluorescent protein (FP)-labeled cells and proteins in living organisms noninvasively. Here, we examined whether this modality could reach a sufficient sensitivity to allow evaluation of the regeneration process of enhanced green fluorescent protein (eGFP)-labeled muscle precursors (myoblasts). Using a basic FLI station, we were able to detect clear fluorescence signals generated by 40,000 labeled cells injected into a tibialis anterior (TA) muscle of mouse. We observed that the signal declined to approximately 25% on the 48 hours of cell injection followed by a recovery starting at the second day and reached a peak of approximately 45% of the original signal by the 7th day, suggesting that the survived population underwent a limited run of proliferation before differentiation. To assess whether transplanted myoblasts could form satellite cells, we injured the transplanted muscles repeatedly with cardiotoxin. We observed a recovery of fluorescence signal following a disappearance of the signal after each cardiotoxin injection. Histology results showed donor-derived cells located underneath basal membrane and expressing Pax7, confirming that the regeneration observed by imaging was indeed mediated by donor-derived satellite cells. Our results show that FLI is a powerful tool that can extend our ability to unveil complicated biological processes such as stem cell-mediated regeneration.
Xu
Xiaoyin
X
Functional and Molecular Imaging Center, Optical Imaging Laboratory, Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Yang
Zhong
Z
Liu
Qiang
Q
Wang
Yaming
Y
D000818:Animals; D054715:Cardiotoxins / Q000009:adverse effects; D002454:Cell Differentiation; D049109:Cell Proliferation; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D016513:Mice, SCID; D008856:Microscopy, Fluorescence / Q000379:methods*; D018482:Muscle, Skeletal / Q000166:cytology / Q000293:injuries / Q000502:physiology*; D032446:Myoblasts / Q000637:transplantation*; D051763:PAX7 Transcription Factor / Q000502:physiology; D012038:Regeneration; D032496:Satellite Cells, Skeletal Muscle / Q000502:physiology
D054715:Cardiotoxins; D051763:PAX7 Transcription Factor; C497321:PAX7 protein, human; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins