Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, C3
Using endothelial progenitor cells as a genetic shuttle to alter central control of cardiovascular function in conscious rats
A. Alviar Baquero1, N. Kränkel1, J. Whitaker1, J. Hewinson1, M. Dewhurst2, P. Madeddu1, J. Paton1
1. Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom. 2. Pfizer, Sandwich, kent, United Kingdom.
Emerging evidence indicates endothelial progenitor cell (EPC) dysfunction is a contributing factor in hypertension and as a result, EPCs could prove viable targets in its treatment 1. Our evidence shows endothelial dysfunction and inflammation of the brainstem microvasculature that includes regions responsible for regulating arterial pressure 2. Our aim is to use EPCs to target brainstem microvasculature in vivo and assess changes in central cardiovascular control. Bone marrow mononuclear cells from male Wistar rats (5% halothane until loss of pinch reflexes followed by cervical dislocation) were expanded in conditions appropriate for the endothelial lineage and confirmed subsequently 3,4. EPCs (60-90,000 cells) or control (Dulbecco’s Phosphate Buffered Saline vehicle without calcium and magnesium: DPBS, or differentiated rat brain endothelial cells: RBE4) were injected into dorsomedial medulla of normotensive (NT) and spontaneously hypertensive rats (SHR) following anaesthesia (5% halothane until loss of pinch reflex, then Ketamine (60mg/kg) and Domitor (250µg/kg)) given i.p. Following surgery Baytril (2.5%) antibiotic was given for 1 week in drinking water). EPCs were fluorescently tagged (CM-DiI) or transduced to express eGFP(LV-hELF-1α-eGFP). EPCs were associated with the microvasculature, including arterioles as seen by immunofluorescence. Using radio-telemetry 5, we found chronic decreases in systolic pressure (SBP) and low frequency spectra of SBP (LF-SBP) relative to animals injected with DPBS or RBE4. Peak change in SBP in NT EPC (n=7) vs. NT DPBS (n=6) was -4.0±0.7 mmHg (p=<0.001); NT EPC (n=7) vs. NT RBE4 (n=6) = -3.0±0.6 mmHg (p=<0.001); no significant difference seen comparing NT RBE4 vs. NT DPBS. In SHR EPC (n=5) vs. SHR DPBS (n=6) there was a fall of -8±0.7 mmHg (p=<0.001), which was greater than that seen in NT rats (p=<0.001 two-way unpaired students t-test). In the EPC NT group there was a decrease in LF-SBP vs. DPBS -10±3% (p=<0.01). In SHR there was a decrease in LF/HighFrequency pulse interval in the EPC group compared to DPBS group (-10±1% p=<0.001), which may suggest a difference in mechanisms between NT and SHR EPC groups. In conclusion, EPCs injected into the parenchyma of the dorsomedial medulla associate with the microvasculature and alter cardiovascular autonomic function in both NT and SHR. The finding that both SBP and, indirectly, sympathetic activity decrease after EPC transplantation is consistent with pro-hypertensive effects of endothelial dysfunction within the brainstem. Our current work is transducing EPCs using lentiviral vector to express angiotensin converting enzyme-2 prior to administration to in vivo rats. In a pilot, we injected NT EPCs-eGFP into SHRs (I.V.) and found a decrease in BP of ~20mmHg. Two-way paired students t-test used unless otherwise stated.
Where applicable, experiments conform with Society ethical requirements