Tissue-engineered fibrin scaffolds containing neural progenitors enhance functional recovery in a subacute model of SCI.

Two recurring problems with stem/neural progenitor cell (NPC) transplantation therapies for spinal cord injury (SCI) are poor cell survival and uncontrolled cell differentiation. The current study evaluated the viability and differentiation of embryonic stem cell-derived neural progenitor cells (ESNPCs) transplanted within fibrin scaffolds containing growth factors (GFs) and a heparin-binding delivery system (HBDS) to enhance cell survival and direct differentiation into neurons. Mouse ESNPCs were generated from mouse embryonic stem cells (ESCs) using a 4-/4+ retinoic acid (RA) induction protocol that resulted in a population of cells that was 70% nestin positive NPCs. The ESNPCs were transplanted directly into a rat subacute dorsal hemisection lesion SCI model. ESNPCs were either encapsulated in a fibrin scaffold; encapsulated in fibrin containing the HBDS, neurotrophin-3 (NT-3) and platelet derived growth factor (PDGF-AA); or encapsulated in fibrin scaffolds with NT-3 and PDGF-AA without the HBDS. We report that the combination of GFs and fibrin scaffold (without HBDS) enhanced the total number of ESNPCs present in the treated spinal cords and increased the number of ESNPC-derived NeuN positive neurons 8 weeks after transplantation. All experimental groups treated with ESNPCs exhibited an increase in behavioral function 4 weeks after transplantation. In a subset of animals, the ESNPCs over-proliferated as evidenced by SSEA-1 positive/Ki67 positive ESCs found at 4 and 8 weeks. These results demonstrate the potential of tissue-engineered fibrin scaffolds to enhance the survival of NPCs and highlight the need to purify cell populations used in therapies for SCI.

Eosinophils regulate adipose tissue inflammation and sustain physical and immunological fitness in old age.

Adipose tissue eosinophils (ATEs) are important in the control of obesity-associated inflammation and metabolic disease. However, the way in which ageing impacts the regulatory role of ATEs remains unknown. Here, we show that ATEs undergo major age-related changes in distribution and function associated with impaired adipose tissue homeostasis and systemic low-grade inflammation in both humans and mice. We find that exposure to a young systemic environment partially restores ATE distribution in aged parabionts and reduces adipose tissue inflammation. Approaches to restore ATE distribution using adoptive transfer of eosinophils from young mice into aged recipients proved sufficient to dampen age-related local and systemic low-grade inflammation. Importantly, restoration of a youthful systemic milieu by means of eosinophil transfers resulted in systemic rejuvenation of the aged host, manifesting in improved physical and immune fitness that was partially mediated by eosinophil-derived IL-4. Together, these findings support a critical function of adipose tissue as a source of pro-ageing factors and uncover a new role of eosinophils in promoting healthy ageing by sustaining adipose tissue homeostasis.

S-nitrosylation of dynamin-related protein 1 mediates mutant huntingtin-induced mitochondrial fragmentation and neuronal injury in Huntington's disease.

AIMS: Dynamin-related protein1 (Drp1) is a large GTPase that mediates mitochondrial fission. We recently reported in Alzheimer's disease (AD) that S-nitrosylation of Drp1 (forming S-nitroso [SNO]-Drp1) results in GTPase hyperactivity and mitochondrial fragmentation, thus impairing bioenergetics and inducing synaptic damage and neuronal loss. Here, since aberrant mitochondrial dynamics are also key features of Huntington's disease (HD), we investigated whether formation of SNO-Drp1 contributes to the pathogenesis of HD in cell-based and animal models. RESULTS: We found that expression of mutant huntingtin (mutHTT) protein in primary cultured neurons triggers significant production of nitric oxide (NO). Consistent with this result, increased levels of SNO-Drp1 were found in the striatum of a transgenic mouse model of HD as well as in human postmortem brains from HD patients. Using specific fluorescence markers, we found that formation of SNO-Drp1 induced excessive mitochondrial fragmentation followed by loss of dendritic spines, signifying synaptic damage. These neurotoxic events were significantly abrogated after transfection with non-nitrosylatable mutant Drp1(C644A), or by the blocking of NO production using an nitric oxide synthase inhibitor. These findings suggest that SNO-Drp1 is a key mediator of mutHTT toxicity, and, thus, may represent a novel drug target for HD. INNOVATION AND CONCLUSION: Our findings indicate that aberrant S-nitrosylation of Drp1 is a prominent pathological feature of neurodegenerative diseases such as AD and HD. Moreover, the SNO-Drp1 signaling pathway links mutHTT neurotoxicity to a malfunction in mitochondrial dynamics, resulting in neuronal synaptic damage in HD.

Controlled release of neurotrophin-3 and platelet-derived growth factor from fibrin scaffolds containing neural progenitor cells enhances survival and differentiation into neurons in a subacute model of SCI.

A consistent problem with stem/neural progenitor cell transplantation following spinal cord injury (SCI) is poor cell survival and uncontrolled differentiation following transplantation. The current study evaluated the feasibility of enhancing embryonic stem cell-derived neural progenitor cell (ESNPC) viability and directing their differentiation into neurons and oligodendrocytes by embedding the ESNPCs in fibrin scaffolds containing growth factors (GF) and a heparin-binding delivery system (HBDS) in a subacute rat model of SCI. Mouse ESNPCs were generated from mouse embryonic stem cells (ESCs) using a 4-/4+ retinoic acid (RA) induction protocol. The ESNPCs were then transplanted as embryoid bodies (EBs, 70% neural progenitor cells) into the subacute model of SCI. ESNPCs (10 EBs per animal) were implanted directly into the SCI lesion, encapsulated in fibrin scaffolds, encapsulated in fibrin scaffolds containing the HBDS, neurotrophin-3 (NT-3), and platelet-derived growth factor (PDGF), or encapsulated in fibrin scaffolds with NT-3 and PDGF with no HBDS. We report here that the combination of the NT-3, PDGF, and fibrin scaffold (with or without HBDS) enhanced the total number of ESNPCs present in the spinal cord lesion 2 weeks after injury. In addition, the inclusion of the HBDS with growth factor resulted in an increase in the number of ESNPC-derived NeuN-positive neurons. These results demonstrate the ability of fibrin scaffolds and the controlled release of growth factors to enhance the survival and differentiation of neural progenitor cells following transplantation into a SCI model.