An investigation of initial retention of stem / progenitor cells following intracoronary injection: implications to cell therapy for the treatment of heart failure.
Abstract
Intracoronary injection is a frequently used clinical protocol for stem / progenitor cell
therapy to the heart. Initial donor cell retention in the heart is the key to the success of this
approach; however, this process has been poorly investigated. I established an original
model to quantitatively assess initial donor cell retention after intracoronary cell injection in
rats using an ex-vivo heart perfusion system and investigated factors that could affect
retention.
The initial retention efficiency of bone marrow mononuclear cells (BMMNC) was
20% after injection into normal hearts. The majority (>90%) of BMMNC loss into the
coronary effluent occurred within the first minute of injection. Increased BMMNC dose
increased absolute retention with a linear dose-effect relationship, while retention efficiency
was unaltered. Retention efficiency increased to 30% in hearts with ischaemia-reperfusion,
while flow cytometric studies showed that surface marker expression was unchanged
between the pre-injection donor cell population and the population in the coronary effluent
in both normal and ischemia-reperfused hearts. This suggests that active interactions
between donor cells and coronary endothelium were not critical for donor cell retention
using these experimental conditions. Instead, cell size assessment revealed that larger
subpopulations of BMMNC were preferentially retained compared to smaller BMMNC in
both normal and ischemia-reperfused hearts. Furthermore, a larger cell type, bone-marrow
derived mesenchymal stem cells (MSC; median cell size=10.1 μm), had a markedly
increased retention efficiency (80%) compared to BMMNC (median cell size=7.0 μm). A
greater proportion of MSC with a larger diameter were retained compared to smaller
diameter MSC; this enhanced retention plateaued with MSC ≥ 9 μm.
Immunohistochemical analysis using fluorescently labeled donor cells demonstrated
that all BMMNC retained in normal and ischaemia-reperfusion hearts were located within
the coronary vasculature, without extravasation, up to 60 minutes after injection. Heart perfusion parameters and histological features exhibited evidence of coronary embolism
after intracoronary injection of MSC, but not BMMNC (up to 40x106).
These data collectively suggest that passive mechanical entrapment, and not active
endothelial cell-donor cell interactions, is responsible for initial donor cell retention after
intracoronary injection. This has important implications for future clinical protocols of
intracoronary injection of stem / progenitor cells to the heart.
Authors
Campbell, Niall Gordon SimonCollections
- Theses [4352]