Objective: We investigated long-term effects of intracoronary CD34+ cell transplantation in dilated cardiomyopathy and the relationship between intramyocardial cell homing and clinical response. Methods and Results:

A fter an acute myocardial injury, recruitment of stem cells may significantly influence the repair process. Studies have shown that serum stromal-derived factor-1 (SDF-1) levels rise significantly after an acute myocardial infarction, which increases homing of stem cells to the damaged tissue. 1 In contrast, in patients with chronic heart failure, local homing signals may be less intense. This difference is especially pronounced in patients with nonischemic dilated cardiomyopathy (DCM), which involves significant downregulation of several homing factors, including SDF-1 2 . The importance of homing is especially prominent when considering stem cell therapy in patients with heart failure.3 In a recent study of patients with nonischemic DCM, we demonstrated that the response to intracoronary CD34 + cell therapy is dependent on the degree of myocardial cell retention. 4 These findings suggest that the efficacy of intracoronary cell therapy may be limited by the number of cells retained in the myocardium.Compared with intracoronary delivery, intramyocardial (IM) cell delivery is consistently associated with higher myocardial cell retention rates in both early and late phases after acute myocardial infarction. 5,6 In preclinical models of ischemic heart failure, IM injection of higher doses of bone marrow mononuclear cells was associated with incremental benefit, 7 and late cardiac functional recovery was more prominent in Background-In an open-label blinded study, we compared intracoronary and transendocardial CD34 + cell transplantation in patients with nonischemic dilated cardiomyopathy. Methods and Results-Of the 40 patients with dilated cardiomyopathy, 20 were randomized to receive intracoronary injection and 20 received transendocardial CD34 + cell delivery. In both groups, CD34 + cells were mobilized by filgrastim, collected via apheresis, and labeled with technetium-99m radioisotope for single-photon emission computed tomographic imaging. In the intracoronary group, cells were injected intracoronarily in the artery supplying segments of greater perfusion defect on myocardial perfusion scintigraphy. In the transendocardial group, electroanatomic mapping was used to identify viable but dysfunctional myocardium, and transendocardial cell injections were performed. Nuclear single-photon emission computed tomographic imaging for quantification of myocardial retention was performed 18 hours thereafter. At baseline, groups did not differ in age, sex, left ventricular ejection fraction, or N-terminal pro-brain natriuretic peptide levels. The number of CD34 + cells was also comparable (105±31×10 6 in the transendocardial group versus 103±27×10 6 in the intracoronary group, P=0.62). At 18 hours after procedure, myocardial retention was higher in the transendocardial group (19.2±4.8%) than in the intracoronary group (4.4±1.2%, P<0.01). At 6 months, left ventricular ejection fraction improved more in the transendocardial group (+8.1±4.3%) than in the intracoronary group (+4.2±2.3%, P=0.03). The same pattern was observed...

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Gain-of-function D816V point mutation within the kinase domain of the transmembrane receptor KIT is found in the great majority of patients with systemic mastocytosis (SM) and is attractive therapeutic target. Twenty patients with SM were enrolled during 2003–2005 in phase II clinical trial with imatinib mesylate (400mg daily), a KIT inhibitor. Median time on therapy was 9 months (range, 0.5 – 44+). Only 1 patient, with D816V KIT mutation-negative FIP1L1-PDGFRα-negative SM-HES, achieved complete remission (now lasting for 44 months). Six other patients reported symptomatic improvement, including 2 with D816V KIT mutation-positive SM (one reported improvement in diarrhea and the other in fatigue). Other patients had no benefit. Imatinib was relatively well tolerated. Our study confirms that imatinib therapy does not result in appreciable clinical activity in patients with D816V mutation-positive SM, but may result in a significant benefit in occasional patient with D816V mutation-negative SM.