Controlling new blood vessel formation is of interest in regenerative medicine and cancer treatment. Heparin, a biopolymer that binds to angiogenic growth factors, was used to nucleate the self-assembly of nanostructures from designed peptide amphiphile molecules. This process yields rigid nanofibers that display heparin chains to orient proteins for cell signaling. In vivo, the nanostructures stimulated extensive new blood vessel formation using nanogram amounts of growth-factor proteins that by themselves did not induce any detectable angiogenesis.

Rationale Efficient clearance of apoptotic cells (efferocytosis) is a prerequisite for inflammation resolution and tissue repair. Following myocardial infarction (MI), phagocytes are recruited to the heart and promote clearance of dying cardiomyocytes (CMs). The molecular mechanisms of efferocytosis of CMs and in the myocardium are unknown. The injured heart provides a unique model to examine relationships between efferocytosis and subsequent inflammation resolution, tissue remodeling, and organ function. Objective We set out to identify mechanisms of dying cardiomyocyte (CM) engulfment by phagocytes and to for the first time assess the causal significance of disrupting efferocytosis during MI. Methods and Results In contrast to other apoptotic cell receptors, macrophage MER tyrosine kinase (MER-TK) was necessary and sufficient for efferocytosis of CMs ex vivo. In mice, Mertk was specifically induced in Ly6cLO myocardial phagocytes after experimental coronary occlusion. Mertk deficiency led to an accumulation of apoptotic CMs, independent of changes in non-CMs, and a reduced index of in vivo efferocytosis. Importantly, suppressed efferocytosis preceded increases in myocardial infarct size and led to delayed inflammation resolution and reduced systolic performance. Reduced cardiac function was reproduced in chimeric mice deficient in bone marrow Mertk; reciprocal transplantation of Mertk+/+ marrow into Mertk-/- mice corrected systolic dysfunction. Interestingly, an inactivated form of MERTK, known as solMER, was identified in infarcted myocardium, implicating a natural mechanism of MERTK inactivation post MI. Conclusions These data collectively and directly link efferocytosis to wound healing in the heart and identify Mertk as a significant link between acute inflammation resolution and organ function.

IMPORTANCE Hematopoietic stem cell transplantation (HSCT) represents a potentially useful approach to slow or prevent progressive disability in relapsing-remitting multiple sclerosis (MS). OBJECTIVE To compare the effect of nonmyeloablative HSCT vs disease-modifying therapy (DMT) on disease progression.

Among patients with relapsing-remitting MS, nonmyeloablative hematopoietic stem cell transplantation was associated with improvement in neurological disability and other clinical outcomes. These preliminary findings from this uncontrolled study require confirmation in randomized trials.