Towards non‐invasive monitoring of mitochondrial function
Op weg naar niet‐invasieve monitoring van mitochondriale functie
The work presented in this thesis describes the development of a non‐invasive and clinically usable system to monitor important aspects of mitochondrial function. This translational research project started with the validation of PpIX‐TSLT for cutaneous use in an animal model and finished with the first study performed in healthy human volunteers. Chapter 1 explores the possibility of using PpIX‐TSLT to measure oxygen‐dependent delayed fluorescence in skin after topical application of the PpIX precursor 5‐ aminolevulinic acid. To enable reliable cutaneous mitoPO2 measurements on the skin, calibration of the signals was necessary. Previous calibrations of PpIX‐TSLT were performed in cultured cells , heart and liver [11, 12]. However, the calibration procedures used for cultured cells and isolated organs were not applicable in skin tissue. Therefore, we developed a novel approach that enables simultaneous measurements of cutaneous mitoPO2 and microvascular oxygen tension in rats (Chapter 2). Subsequently, in Chapter 3, we validated the previously found calibration constants for application on skin by means of these simultaneous measurements. The absolute value of mitoPO2 is an important physiological parameter indicating mitochondrial oxygen availability. However, as investigated in Chapter 4, measurement of the kinetics of delayed fluorescence lifetime (indicative of changes in mitoPO2) after artificially blocking local oxygen supply, provides additional information on mitochondrial oxygen consumption (mitoVO2) and oxygen affinity of the respiratory chain. Having established the feasibility of measuring cutaneous mitoPO2 and mitoVO2 we then examined the changes in mitochondrial oxygenation and oxygen consumption in an endotoxin‐induced septic animal model with and without fluid resuscitation (Chapter 5). The substrate succinate improves mitochondrial complex II activity in sepsis‐induced mitochondrial dysfunction, as previously shown by classical respirometry in isolated mitochondria from muscle biopsies . If we are capable of in vivo monitoring of alterations in mitochondrial function, the administration of succinate in an endotoxininduced sepsis model should provide results similar to those observed in isolated mitochondria. Therefore, in Chapter 6, we performed validation of the mitoVO2 measurements by means of infusing succinate under endotoxin‐induced septic conditions in rats. Other important steps essential for the clinical applicability of PpIX‐TSLT are described in Chapter 7. Here we investigated whether alterations in mitochondrial parameters in skin reflect similar alterations in other organs and tissues. Furthermore, in this chapter we describe a clinical prototype of the PpIX‐TSLT device ready for human use. Finally, after extensive testing in animal studies, we describe the first results of measurements with our new clinical prototype in healthy volunteers (Chapter 8). Chapter 9 provides a detailed description of the PpIX–TSLT. This user‐friendly manual enables researchers to measure mitoPO2 and mitoVO2 in small animal models.
|R.J. Stolker (Robert)|
|Erasmus University Rotterdam|
|Financial support for the studies published in this thesis was obtained from ZonMW (the Netherlands Organisation for Health Research Development). Further financial support for this thesis was generously provided by: Erasmus MC and Photonic Health Care B.V.|
|Organisation||Erasmus MC: University Medical Center Rotterdam|
Harms, F.A. (2014, November 26). Towards non‐invasive monitoring of mitochondrial function. Erasmus University Rotterdam. Retrieved from http://hdl.handle.net/1765/77198