Kidney Week

Abstract: FR-PO110

Photoacoustic Microscopy Reveals Early Decrease in Peritubular Capillary (PC) O₂ Tension Associated with Temporal Changes in Cell Metabolism and Injury Despite Unimpaired PC Flow in Sepsis-Induced AKI

Session Information

• AKI: Mechanisms - Inflammation/Sepsis/Remote Injury
  November 08, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

• 103 AKI: Mechanisms

Authors

• Zheng, Shuqiu, University of Virginia, Charlottesville, Virginia, United States

Shuqiu Zheng,

• Sun, Naidi, University of Virginia, Charlottesville, Virginia, United States

Naidi Sun,

• Cao, Rui, University of Virginia, Charlottesville, Virginia, United States

Rui Cao,

• Poudel, Nabin, University of Virginia, Charlottesville, Virginia, United States

Nabin Poudel,

• Yao, Junlan, University of Virginia, Charlottesville, Virginia, United States

Junlan Yao,

• Tanaka, Shinji, University of Virginia, Charlottesville, Virginia, United States

Shinji Tanaka,

• Rosin, Diane L., University of Virginia, Charlottesville, Virginia, United States

Diane L. Rosin,

• Hu, Song, University of Virginia, Charlottesville, Virginia, United States

Song Hu,

• Okusa, Mark D., University of Virginia, Charlottesville, Virginia, United States

Mark D. Okusa,

Background

The ability to monitor dynamic changes in the renal metabolic rate of oxygen (MRO₂) is critical to understanding the time course of changes in local microenvironmental factors that lead to acute kidney injury (AKI). Technical limitations have impeded in vivo measurement of three key hemodynamic parameters—total hemoglobin concentration (C_Hb), oxygen saturation of hemoglobin (sO₂) and peritubular capillary blood flow (PCBF)—at the microscopic level. To address this, we developed a new technique - intravital multi-parametric photoacoustic microscopy (PAM).

Methods

To validate our system C57BL/6 mice were subjected to 1) hypoxia or 2) LPS-induced sepsis (5 mg/kg LPS, ip). The new intravital PAM platform uses nanosecond-pulsed lasers (532 and 558 nm) for dual-wavelength excitation-based spectroscopic measurement of sO₂. In vivo PAM imaging was performed over time on kidneys at depths of up to 200 μm. Plasma and kidneys were collected for measurement of creatinine, Kim1, NGAL, ATP, and various injury markers.

Results

In vivo PAM performed in mice challenged with 12 or 100% oxygen showed a strong correlation between sO₂ and inhaled oxygen concentration. After LPS, time-dependent changes in hemodynamic parameters and injury markers were observed. PCBF increased within 10 min but returned to and remained normal from 20-200 min. PC sO₂ began to decline immediately and a 30% decrease persisted from 20-200 min. Kidney ATP decreased by ~80% at 40 min. Abrupt increases in Kim1 (~20-fold) and Ngal (~300-fold) and decreases (~80%) in Nrf2 mRNA were observed at 12 hr. Creatinine increased at 24 hrs. Tlr4 and Myd88 mRNA increased at 12 hr.

Conclusion

In vivo PAM enables dynamic monitoring of renal MRO₂ in AKI. The immediate decrease in sO₂ but maintenance of PCBF indicates that blood flow was maintained yet sO₂ was limiting and produced marked temporal changes in biochemical parameters of cell metabolism and injury. This technical innovation lays the foundation for dynamic monitoring of renal oxygen metabolism in AKI, as well as chronic kidney disease, providing a new tool for AKI and CKD studies.
[Zheng & Sun are co-first authors and contributed equally]

Funding

• NIDDK Support