System and method for assessing cellular metabolic activity
Methods and corresponding apparatus and systems for assessing cellular metabolic activity are disclosed. In one aspect, a cell can be illuminated with optical radiation in order to cause multi-photon excitation of at least one endogenous metabolic cofactor in that cell and cause the excited metabolic cofactor to emit fluorescent radiation. A detector can be used to detect the fluorescent radiation emitted by the excited endogenous metabolic cofactor. A computer processor can analyze the fluorescent radiation to derive the following parameters: (1) using a computer processor to analyze the intensity of the fluorescent radiation, (2) a fluorescence lifetime of at least one of the excited metabolic cofactor, (3) a parameter indicative of mitochondrial clustering in the cell. These parameters can be used to assess at least one metabolic process of the cell.
1. A system for optical assessment of cellular metabolic activity, comprising:
an optical radiation source configured to illuminate a plurality of cells in-vivo distributed at different depths of a tissue portion so as to cause multi-photon excitation of at least two metabolic cofactors in the cells,
wherein said at least two metabolic cofactors comprise NAD(P)H and a flavin,
wherein the at least two metabolic cofactors emit fluorescent radiation in response to the excitation;
a detector configured to detect the emitted fluorescent radiation and to generate a plurality of detector signals each indicative of the detected fluorescent radiation; and
an analyzer comprising a processor configured to:
receive the plurality of the detector signals and operate on the detector signals to determine for each of said tissue depths:
(1) an intensity of the fluorescent radiation emitted by said at least two metabolic cofactors,
(2) a parameter associated with fluorescence lifetime of at least one of said at least two metabolic cofactors, and
(3) a parameter indicative of mitochondrial clustering in the cells, and
wherein said analyzer is further configured to provide an assessment of at least one cellular metabolic process selected from the group consisting of glycolysis, oxidative phosphorylation, glutaminolysis, fatty acid oxidation, extrinsic and intrinsic mitochondrial uncoupling, and fatty acid synthesis in each of said tissue depths based on a combined use of the parameter indicative of mitochondrial clustering, the intensity of the emitted fluorescent radiation and the parameter associated with the fluorescence lifetime of the at least one of said at least two metabolic cofactors,
wherein the processor is further configured to correlate an increase in the mitochondrial clustering parameter with enhanced glycolysis, enhanced fatty acid synthesis, enhanced fatty acid oxidation, or enhanced mitochondrial uncoupling, or to correlate a decrease in the mitochondrial clustering parameter with enhanced oxidative phosphorylation or enhanced glutaminolysis,
wherein the processor is further configured to correlate a decrease in an optical redox ratio of NAD(P)H and flavin computed based on said emitted fluorescent radiation with enhanced glycolysis, fatty acid synthesis, or fatty acid oxidation, or to correlate an increase in the optical redox ratio of NAD(P)H and flavin computed based on said emitted fluorescent radiation with enhanced oxidative phosphorylation, enhanced glutaminolysis, or enhanced mitochondrial uncoupling,
wherein the processor is further configured to correlate a decrease in NAD(P)H fluorescence lifetime with enhanced glycolysis, enhanced fatty acid oxidation, or enhanced thermogenesis-associated mitochondrial uncoupling, or to correlate an increase in NAD(P)H fluorescence lifetime with enhanced fatty acid synthesis, enhanced oxidative phosphorylation, enhanced glutaminolysis, or enhanced chemically-induced mitochondrial uncoupling,
wherein the processor is further configured to correlate an increase in the mitochondrial clustering parameter and/or a decrease in an optical redox ratio of NAD(P)H and flavin computed based on said emitted fluorescent radiation combined with a decrease in NAD(P)H fluorescence lifetime with enhanced glycolysis, and
wherein the processor is further configured to correlate an increase in the mitochondrial clustering parameter and/or a decrease in the optical redox ratio of NAD(P)H and flavin computed based on said emitted fluorescent radiation combined with a decrease in the NAD(P)H fluorescence lifetime with enhanced fatty acid synthesis.
2. The system of claim 1 , wherein the optical radiation has a wavelength in a range of about 600 nm to about 1400 nm.
3. The system of claim 2 , wherein the fluorescent radiation has a wavelength in a range of about 400 nm to about 650 nm.
4. The system of claim 1 , wherein the analyzer further comprises an imaging module configured to:
segment an image of each of the cells by selecting a plurality of pixels corresponding to cytoplasm and masking other pixels in the image;
normalize pixel intensities in the segmented image; and
assign an intensity for each of the unmasked pixels via digital object cloning so as to generate a processed image,
wherein the analyzer is further configured to obtain a Fourier transform of the processed image so as to determine a power spectral density associated with the processed image; and to compute the mitochondrial clustering parameter using the power spectral density.
5. The system of claim 4 , wherein the analyzer fits the power spectral density to an inverse power law decay expression for computing the mitochondrial clustering parameter.
6. The system of claim 5 , wherein the analyzer fits the power spectral density to a function R defined as R(k)=Ak −β , wherein, k denotes spatial frequency, A is an amplitude parameter, and β denotes the mitochondrial clustering parameter.
7. The system of claim 1 , wherein the processor is further configured to generate a plurality of fluorescent images of said tissue portion at the different depths and process said images to obtain the parameter indicative of mitochondrial clustering for each of the depths of the tissue portion.
8. The system of claim 7 , further comprising utilizing a depth-dependence of the mitochondrial clustering parameter to assess whether a disease condition is present in the tissue portion.
9. The system of claim 1 , wherein said tissue portion comprises epidermal tissue.
10. The system of claim 1 , wherein said parameter associated with the fluorescence lifetime is indicative of a fraction of the at least one of said at least two metabolic cofactors that is in free or bound state.
11. The system of claim 1 , wherein said flavin comprises any of FAD, lipoamide dehydrogenase, electron transfer flavoprotein and any combination thereof.
12. A system for in-vivo optical assessment of cellular metabolic activity, comprising:
an optical radiation source for illuminating at least one cell in-vivo so as to cause multi-photon excitation of any of NAD (P) H and a flavin in said at least one cell,
a detector configured to detect fluorescent radiation emitted by any of the excited NAD (P) H and the excited flavin and generate one or more detector signals indicative of the detected fluorescent radiation; and
an analyzer comprising a processor configured to receive the one or more detector signals and operate on the one or more detector signals to determine:
(1) an intensity of fluorescent radiation emitted by any of said excited NAD(P)H and said excited flavin,
(2) a parameter associated with a fluorescence lifetime of any of the excited NAD(P)H and the excited flavin, and
(3) a mitochondrial clustering parameter associated with the at least one cell, and
wherein the analyzer is further configured to use a combination of said mitochondrial clustering parameter with at least one of an optical redox ratio of NAD(P)H and flavin computed based on said intensities of emitted fluorescent radiation and said parameter associated with the fluorescence lifetime to assess at least one metabolic process in said at least one cell,
wherein the at least one metabolic process is selected from the group consisting of glycolysis, oxidative phosphorylation, glutaminolysis, fatty acid oxidation, extrinsic and intrinsic mitochondrial uncoupling, and fatty acid synthesis.
13. A system for in-vivo optical assessment of cellular metabolic activity, comprising:
an optical radiation source for illuminating at least one cell in-vivo so as to cause multi-photon excitation of at least two metabolic cofactors associated with mitochondria of said at least one cell, wherein the at least two metabolic cofactors emit fluorescent radiation in response to the excitation, and wherein at least one of said at least two metabolic cofactors comprises any of NAD(P)H and a flavin;
a detector configured to detect the emitted fluorescent radiation and generate one or more detector signals indicative of the detected fluorescent radiation; and
an analyzer comprising a processor configured to receive the one or more detector signals and operate on the one or more detector signals to determine:
(1) an optical redox ratio based on fluorescent radiation intensity associated with fluorescent radiation emitted by said excited at least two metabolic cofactors,
(2) a parameter associated with a fluorescence lifetime of the at least one of said at least two metabolic cofactors, and
(3) a mitochondrial clustering parameter associated with the at least one cell, and
wherein the analyzer is further configured to use a combination of said mitochondrial clustering parameter with said optical redox ratio and said parameter associated with the fluorescence lifetime to assess at least one metabolic process in said at least one cell.
14. A system for optical assessment of cellular metabolic activity, comprising:
an optical radiation source for illuminating at least one cell so as to cause multi-photon excitation of at least two metabolic cofactors in said at least one cell, wherein the at least two metabolic cofactors emit fluorescent radiation in response to the excitation, and wherein the at least two metabolic cofactors comprise NAD(P)H and a flavin,
a detector configured to detect the emitted fluorescent radiation and generate one or more detector signals indicative of the detected fluorescent radiation; and
an analyzer comprising a processor configured to receive the one or more detector signals and operate on the one or more detector signals to determine:
(1) an intensity of the emitted fluorescent radiation,
(2) a parameter associated with fluorescence lifetime of at least one of said at least two metabolic cofactors, and
(3) a parameter indicative of mitochondrial clustering in the at least one cell, and
wherein the analyzer is further configured to use a combination of the fluorescent radiation intensity, the parameter associated with the fluorescence lifetime and said parameter indicative of mitochondrial clustering to assess at least one cellular metabolic process in the at least one cell, wherein the at least one cellular metabolic process is selected from the group consisting of glycolysis, oxidative phosphorylation, glutaminolysis, fatty acid oxidation, extrinsic and intrinsic mitochondrial uncoupling, and fatty acid synthesis,
wherein the analyzer is further configured to correlate an increase in the mitochondrial clustering parameter with enhanced glycolysis, enhanced fatty acid synthesis, enhanced fatty acid oxidation, or mitochondrial uncoupling, and
wherein the analyzer is further configured to correlate an increase in the mitochondrial clustering parameter combined with a decrease in an optical redox ratio of the NAD(P)H relative to the flavin computed based on the intensity of the emitted fluorescent radiation and a decrease in NAD(P)H fluorescence lifetime with enhanced glycolysis.
15. The system of claim 14 , wherein said flavin comprises FAD.
16. A system for in-vivo optical assessment of a cellular metabolic activity, comprising:
an optical radiation source for illuminating at least one cell in-vivo so as to cause multi-photon excitation of at least one metabolic cofactor,
a detector configured to detect fluorescent radiation emitted by the excited at least one metabolic cofactor and generate one or more detector signals indicative of the detected fluorescent radiation; and
an analyzer comprising a processor configured to receive the one or more detector signals and operate on the one or more detector signals to determine fluorescence intensity emitted by the at least one metabolic cofactor, fluorescence lifetime of the at least one metabolic cofactor, and mitochondrial clustering within the at least one cell and to identify changes in one or more metabolic processes selected from the group consisting of glycolysis, glutaminolysis, extrinsic and intrinsic mitochondrial uncoupling, fatty acid oxidation and synthesis, and oxidative phosphorylation based on at least two of said fluorescence intensity, said fluorescence lifetime and said mitochondrial clustering.
17. The system of claim 16 , wherein said at least one metabolic cofactor comprises any of NADH, NAD(P)H, FAD, Lipoamide dehydrogenase (Lip-DH), and electron transfer flavoprotein (ETF).
18. The system of claim 17 , wherein the processor is further configured to correlate a decrease in NAD(P)H bound fraction with enhanced glycolysis, intrinsic mitochondrial uncoupling, or fatty acid oxidation.
19. The system of claim 17 , wherein the processor is further configured to correlate an increase in NAD(P)H bound fraction with enhanced oxidative phosphorylation, glutaminoloysis, extrinsic mitochondrial uncoupling or fatty acid synthesis.
20. The system of claim 16 , wherein the processor is further configured to correlate a decrease in the mitochondrial clustering with enhanced oxidative phosphorylation or glutaminolysis and an increase in the mitochondrial clustering with enhanced glycolysis, extrinsic mitochondrial uncoupling, intrinsic mitochondrial uncoupling, fatty acid synthesis or oxidation.