Figure 1: Schematic of stem cell engineering approach
Stem cells are isolated from a variety of sources and modified with cardioprotective genes to confer increased proliferation and resistance to apoptosis. After expansion the enhanced stem cells are delivered to damaged myocardium where they elicit a multitude of protective effects: A) neovascularization, B) myogenesis, C) endogenous stem cell recruitment, D) induced proliferation and inhibition of apoptosis for the injected population, and E) secretion of paracrine factors to enhance the survival of the surrounding myocardium.
The results of mouse studies in which CPCs engineered to produce Pim-1 (CPCeP) are set forth in Figure 2. These studies show that long term, persistent benefits are achieved with CPCeP cells introduced into mouse myocardium in a model of myocardial infarction. Figure 3 illustrates the extended survival of CPCeP cells as they adoptively implant and differentiate into functional myocardium in vivo.
Figure 2. Long term persistent cardiac functional recovery in animals treated with CPCeP
(A-C) EKG asessment of FS (A), EF (B), and AWD (C), in sham (■, orange), vehicle (●, black), CPCe (▲, blue), and CPCeP (♦, green), 32 weeks post infarction (mean ± SEM, n≥6 animals for each group). (D-F) Cardiac function of sham, vehicle, CPCe, and CPCeP were evaluated using in vivo hemodynamic measurements of LVEDP (D), LVDP (E), and dP/dT (F), 32 weeks post-intramyocardial injection (mean ± SEM, n≥5).
Figure 3. Persistent engraftment and differentiation of CPCeP at 32 weeks post intramyocardial injection
(A) Infarct size measurement and confocal micrographs of hearts injected with CPCe or CPCeP 32 weeks post infarction. Sections stained for GFP (green), tropomyosin (red), c-kit (white), and nuclear stain (blue). (B) c-kit in cardiac sections treated with CPCe or CPCeP and stained with GFP (green), c-kit (red), tropomyosin (blue), and nuclear stain (white). (C) Number of total vessels (left panel), small vessels (right panel) and immunolabeling for vasculature at 32 weeks post infarction. Sections stained with GFP (green), smooth muscle actin (red), tropomyosin (blue), and nuclear stain (white). Infarction was verified by equivalent decreases in EF, FS, and AWD of all groups at 3 days post infarction. n=3, * p<.05, **p<.01, **p<.001. Scale bars = 50mm.