Our results demonstrate the improvement of islet graft morphology and function by co-transplantation with MSCs. This improvement is attributable, at least in part, to the promotion of graft revascularization mediated by MSCs.

SUMMARY MyoD is a key regulator of skeletal myogenesis that directs contractile protein synthesis, but whether this transcription factor also regulates skeletal muscle metabolism has not been explored. In a genome-wide ChIP-seq analysis of skeletal muscle cells, we unexpectedly observed that MyoD directly binds to numerous metabolic genes, including those associated with mitochondrial biogenesis, fatty acid oxidation, and the electron transport chain. Results in cultured cells and adult skeletal muscle confirmed that MyoD regulates oxidative metabolism through multiple transcriptional targets including PGC-1β, a master regulator of mitochondrial biogenesis. We find that PGC-1β expression is cooperatively regulated by MyoD and the alternative NF-κB signaling pathway. Bioinformatics evidence suggests that this cooperativity between MyoD and NF-κB extends to other metabolic genes as well. Together, these data identify MyoD as a regulator of the metabolic capacity of mature skeletal muscle to ensure that sufficient energy is available to support muscle contraction.

Background The activation of p38 mitogen-activated protein kinases (MAPK) is implicated in cold ischemia-reperfusion injury of donor organs. The islet isolation process, from pancreas procurement through islet collection, may activate p38MAPK leading to cytokine release and islet damage. This damage may be prevented by treating pancreata with a p38MAPK inhibitor (p38IH) prior to cold preservation. Methods Pancreata removed from Beagle dogs were infused with UW solution containing either the p38IH, SB203580 and Pefabloc (n=6) or vehicle (DMSO and Pefabloc) alone (n=7), through the pancreatic duct and preserved using the two-layer method. After 20–22 hours, islets were isolated and 3000 IEQ/kg were autotransplanted into the corresponding dog to monitor glucose metabolism. Results P38IH-treated pancreata yielded significantly more islets than control pancreata (IEQ/g: 2,134±297 vs. 1,477±145 IEQ/g or 65,012±9,385 vs. 45,700±5,103 IEQ/Pancreas; p<0.05). Apoptotic β-cell percentages assessed by LSC were lower in p38IH-treated than the controls (44±9.4% vs. 61.6±4.8%, p<0.05). TNF-α expression assessed by RT-PCR was significantly lower in the p38IH-treated group than controls. All dogs (3000 IEQ/kg) transplanted with p38IH-treated islets (n=5) became euglycemic vs. 4 of 5 dogs that received untreated islets. Plasma C-peptide levels following glucagon challenge were higher in animals receiving p38IH-treated islets (n=5) vs. untreated islets (n=4) (0.40±0.78 vs. 0.21±0.05 ng/mL, p<0.05). Conclusions Infusion of pancreata with UW solution containing p38IH through the duct prior to peservation suppresses cytokine release, prevents β cell apoptosis, and improves islet yield significantly with no adverse effect on islet function following transplantation. P38IH treatment of human pancreata may improve islet yield for use in clinical transplantation.

SUMMARY Skeletal muscle growth immediately following birth is a critical for proper body posture and locomotion. However, compared to embryogenesis and adulthood, the processes regulating the maturation of neonatal muscles is considerably less clear. Studies in the 1960s predicted that neonatal muscle growth results from nuclear accretion of myoblasts preferentially at the tips of myofibers. Remarkably, little information has been added since then to resolve how myoblasts migrate to the ends of fibers. Here, we provide insight to this process by revealing a unique NF-κB-dependent communication between NG2+ interstitial cells and myoblasts. NF-κB in NG2+ cells promotes myoblast migration to the tips of myofibers through cell-cell contact. This occurs through expression of ephrinA5 from NG2+ cells, which we further deduce is an NF-κB target gene. Together, results suggest that NF-κB plays an important role in the development of newborn muscles to ensure proper myoblast migration for fiber growth.