Label-free DNA imaging in vivo with stimulated Raman scattering microscopy.
Label-free DNA imaging is highly desirable in biology and medicine to perform live imaging without affecting cell function and to obtain instant histological tissue examination during surgical procedures. Here we show a label-free DNA imaging method with stimulated Raman scattering (SRS) microscopy for visualization of the cell nuclei in live animals and intact fresh human tissues with subcellular resolution. Relying on the distinct Raman spectral features of the carbon-hydrogen bonds in DNA, the distribution of DNA is retrieved from the strong background of proteins and lipids by linear decomposition of SRS images at three optimally selected Raman shifts. Based on changes on DNA condensation in the nucleus, we were able to capture chromosome dynamics during cell division both in vitro and in vivo. We tracked mouse skin cell proliferation, induced by drug treatment, through in vivo counting of the mitotic rate. Furthermore, we demonstrated a label-free histology method for human skin cancer diagnosis that provides comparable results to other conventional tissue staining methods such as H&E. Our approach exhibits higher sensitivity than SRS imaging of DNA in the fingerprint spectral region. Compared with spontaneous Raman imaging of DNA, our approach is three orders of magnitude faster, allowing both chromatin dynamic studies and label-free optical histology in real time.
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138;
Fa-Ke
FK
Lu
Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138;
Srinjan
S
Basu
Cutaneous Biology Research Center, Department of Dermatology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129;
Vivien
V
Igras
Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114;
Mai P
MP
Hoang
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138;
Minbiao
M
Ji
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138;
Dan
D
Fu
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138;
Gary R
GR
Holtom
Department of Dermatology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114.
Victor A
VA
Neel
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138;
Christian W
CW
Freudiger
Cutaneous Biology Research Center, Department of Dermatology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129; dfisher3@mgh.harvard.edu xie@chemistry.harvard.edu.
David E
DE
Fisher
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138; dfisher3@mgh.harvard.edu xie@chemistry.harvard.edu.
X Sunney
XS
Xie
D000818:Animals; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D004247:DNA / Q000032:analysis* / Q000737:chemistry; D003952:Diagnostic Imaging; D005260:Female; D006367:HeLa Cells; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008055:Lipids / Q000737:chemistry; D051379:Mice; D008819:Mice, Nude; D008853:Microscopy; D008938:Mitosis; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000378:metabolism; D013059:Spectrum Analysis, Raman
D008055:Lipids; D004247:DNA
cell division; label-free histology; mitotic rate; skin cancer; stimulated Raman scattering microscopy