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Published January 1, 2022 | Accepted Version + Supplemental Material
Journal Article Open

Probing single-cell oxygen reserve in sickled erythrocytes via in vivo photoacoustic microscopy


Individuals with sickle cell disease (SCD) face ongoing risk of multi-organ ischemia resulting in chronic disability, frequent hospitalizations, and early mortality. The relationship between hemoglobin (Hb) S polymerization, erythrocyte sickling, and tissue ischemia has been of great interest. Oxygen off-loading and increasing deoxy-Hb concentration promote HbS polymerization, the latter, which has been linked to early erythrocyte deformation or "reversible" sickling. Eventually, severe polymerization weakens the cell membrane, leading to "irreversibly" sickled cells. Whether the degree of polymerization and the cell's morphologic state, in turn, influence oxygen binding and thus, tissue oxygen availability has been of interest, but technically challenging to study in patients. Over two decades, Wang and colleagues developed an imaging platform, photoacoustic microscopy (PAM), which offers two unique aspects compared to other intravital microscopy systems: (1) high resolution in vivo human imaging using the cuticle as the window to a highly organized vascular bed capable of imaging single capillary loops, and (2) measurements of oxy- and deoxy-Hb levels within single capillaries and single erythrocytes. In this study, we aimed to: (1) characterize capillary morphology and hemodynamic/oxygen metabolic properties in the cuticle nailbed of individuals with SCD compared to healthy controls and (2) track single erythrocytes along the capillary loop to obtain measurements of erythrocyte elongation (ellipticity index, EI) and oxygen saturation before and after tissue oxygen exchange. We hypothesized that erythrocyte EI, as an index of HbS polymerization, would be associated with decreased arteriolar oxygen saturation and/or increased oxygen extraction fraction (OEF) across capillaries—representing compromised "oxygen reserve."

Additional Information

© 2021 Wiley Periodicals LLC. Issue Online: 08 December 2021; Version of Record online: 02 November 2021; Accepted manuscript online: 23 October 2021; Manuscript accepted: 20 October 2021; Manuscript revised: 16 October 2021; Manuscript received: 16 June 2021. This work was supported by the National Institutes of Health R01HL129241 and RF1NS116565 (A.L.F.), R01NS094692, R37NS110699, U24NS107230 (J-M.L.), and R01GM113838 (A.D). Author Contributions: Andria L. Ford and Hsun-Chia Hsu designed the experiment, collected the data, analyzed and interpreted data, and prepared the manuscript. Michael M. Binkley, Stephen Rogers, Toru Imai, and Konstantin Maslov analyzed and interpreted the data. Allan Doctor, Lihong V. Wang, and Jin-Moo Lee designed the experiment and analyzed and interpreted data. All authors critically reviewed and approved the final version of the manuscript. Conflict of Interests: L. W. has a financial interest in Microphotoacoustics, Inc., CalPACT, LLC, and Union Photoacoustic Technologies, Ltd., which, however, did not support this work. The remaining authors do not have any competing interests. Data Availability Statement: The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.

Attached Files

Accepted Version - ajh.26387_acc.pdf

Accepted Version - nihms-1750651.pdf

Supplemental Material - ajh26387-sup-0001-supinfo.docx

Supplemental Material - ajh26387-sup-0002-figures1.tif

Supplemental Material - ajh26387-sup-0003-figures2.tif

Supplemental Material - ajh26387-sup-0004-figures3.tif

Supplemental Material - ajh26387-sup-0005-figures4.tif

Supplemental Material - ajh26387-sup-0006-tables1.docx


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Additional details

August 22, 2023
October 23, 2023