Alignment and Composition of Laminin-Polycaprolactone Nanofiber Blends Enhance Peripheral Nerve Regeneration

Peripheral nerve transection occurs commonly in traumatic injury, causing deficits distal to the injury site. Conduits for repair currently on the market are hollow tubes; however, they often fail due to slow regeneration over long gaps. To facilitate increased regeneration speed and functional recovery, the ideal conduit should provide biochemically relevant signals and physical guidance cues, thus playing an active role in regeneration. To that end, laminin and lamininpolycaprolactone (PCL) blend nanofibers were fabricated to mimic peripheral nerve basement membrane. In vitro assays established 10% (wt) laminin content is sufficient to retain neurite-promoting effects of laminin. In addition, modified collector plate design to introduce an insulating gap enabled the fabrication of aligned nanofibers. The effects of laminin content and fiber orientation were evaluated in rat tibial nerve defect model. The lumens of conduits were filled with nanofiber meshes of varying laminin content and alignment to assess changes in motor and sensory recovery. Retrograde nerve conduction speed at 6 weeks was significantly faster in animals receiving aligned nanofiber conduits than in those receiving random nanofiber conduits. Animals receiving nanofiber-filled conduits showed some conduction in both anterograde and retrograde directions, whereas in animals receiving hollow conduits, no impulse conduction was detected. Aligned PCL nanofibers significantly improved motor function; aligned laminin blend nanofibers yielded the best sensory function recovery. In both cases, nanofiber-filled conduits resulted in better functional recovery than hollow conduits. These studies provide a firm foundation for the use of naturalsynthetic blend electrospun nanofibers to enhance existing hollow nerve guidance conduits

Therapeutic Angiogenesis and Bone Regeneration with Natural and Synthetic Small Molecules

Presented on June 11, 2013 from 8:30 a.m.-9:30 a.m. at the Parker H. Petit Institute for Bioengineering & Bioscience (IBB), room 1128, Georgia Tech.Edward Botchwey is an Associate Professor in the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology.Runtime: 68:05 minutesEndothelial cells play significant roles in conditioning the environment in local tissues after injury by the production and secretion of angiocrine factors. At least two distinct subsets of leukocytes, CD45+ CD11b+ Ly6C+Gr1+CX3CR1lo inflammatory monocytes (IM) and CD45+CD11b+Ly6CGr1-CX3CR1hi anti-inflammatory monocytes (AM), respond differentially to these angiocrine factors and promote pathogen/debris clearance and angiogenesis/wound healing, respectively. Our laboratory is currently investigating how local sphingosine 1-phosphate receptor 3 (S1P3) agonism recruits AM to remodeling vessels. We employ micron and nanoscale biomaterials to deliver FTY720, a S1P1/3 agonist, to inflamed and ischemic tissues, to reduce in pro-inflammatory cytokine secretion and an increase in regenerative cytokine secretion. The altered balance of cytokine secretion results in a reduction in inflammatory monocyte recruitment and an increase in anti-inflammatory CX3CR1hi monocyte recruitment to a pro-regenerative perivascular niche. Increased S1P3 expression and activation on AM resulted in significantly enhanced SDF-1α chemotaxis over IM. AM recruitment also enhanced arteriolar diameter expansion and increased length density of the local vasculature: classic signs of vascular remodeling. This work establishes a role for S1P receptor signaling in the local conditioning of tissues by angiocrine factors that preferentially recruit regenerative monocytes that can enhance healing outcomes, bone tissue regeneration, and biomaterial implant functionality

The Conflict between Traditional and Western Cultures: A Comparative Study of Wole Soyinka’s ‘Death and the King’s Horseman’ and Ama Ata Aidoo’s ‘Dilemma of a Ghost’

Conflict, a general phenomenon, exists in everyday life. It has different intrapersonal aspects (thus conflict within a person). There is also a kind of conflict that exists between two people or two groups of people. This is interpersonal conflict. It can be between a person and technology or between ideas. Conflict has been defined as a disagreement or clash between people, ideas, or cultures. Therefore, culture becomes a unique and sentimental phenomenon that is not only cherished but also protected dearly by individuals as well. Thus, literature has become one of the means through which cultural sentiments are projected and expressed. For a long time, Africans have been subjected to cultural imposition and displacement of Western culture. This paper aims to examine the theory that considers the superiority of westernization. This study adopts the sociological theory by focusing on Soyinka's Death and the King’s Horseman and Ama Ata Aidoo’s Dilemma of Ghost. Our decision to select these two texts is informed by the several instances of conflict portrayed in the two texts. The discussion focused on societal norms and belief systems, psychological and generational gap conflicts

Delivery of bioactive lipids from composite microgel-microsphere injectable scaffolds enhances stem cell recruitment and skeletal repair.

In this study, a microgel composed of chitosan and inorganic phosphates was used to deliver poly(lactic-co-glycolic acid) (PLAGA) microspheres loaded with sphingolipid growth factor FTY720 to critical size cranial defects in Sprague Dawley rats. We show that sustained release of FTY720 from injected microspheres used alone or in combination with recombinant human bone morphogenic protein-2 (rhBMP2) improves defect vascularization and bone formation in the presence and absence of rhBMP2 as evaluated by quantitative microCT and histological measurements. Moreover, sustained delivery of FTY720 from PLAGA and local targeting of sphingosine 1-phosphate (S1P) receptors reduces CD45+ inflammatory cell infiltration, promotes endogenous recruitment of CD29+CD90+ bone progenitor cells and enhances the efficacy of rhBMP2 from chitosan microgels. Companion in vitro studies suggest that selective activation of sphingosine receptor subtype-3 (S1P3) via FTY720 treatment induces smad-1 phosphorylation in bone-marrow stromal cells. Additionally, FTY720 enhances stromal cell-derived factor-1 (SDF-1) mediated chemotaxis of CD90+CD11B-CD45- bone progenitor cells in vitro after stimulation with rhBMP2. We believe that use of such small molecule delivery formulations to recruit endogenous bone progenitors may be an attractive alternative to exogenous cell-based therapy

Evaluating Angiogenic Potential of Small Molecules Using Genetic Network Approaches

Control of microvascular network growth is critical to treatment of ischemic tissue diseases and enhancing regenerative capacity of tissue engineering implants. Conventional therapeutic strategies for inducing angiogenesis aim to deliver one or more pro-angiogenic cytokines or to over-express known pro-angiogenic genes, but seldom address potential compensatory or cooperative effects between signals and the overarching signaling pathways that determine successful outcomes. An emerging grand challenge is harnessing the expanding knowledge base of angiogenic signaling pathways toward development of successful new therapies. We previously performed drug optimization studies by various substitutions of a 2-(2,6-dioxo-3-piperidyl)isoindole-1,3-dione scaffold to discover novel bioactive small molecules capable of inducing growth of microvascular networks, the most potent of which we termed phthalimide neovascularization factor 1 (PNF1, formerly known as SC-3-149). We then showed that PNF-1 regulates the transcription of signaling molecules that are associated with vascular initiation and maturation in a time-dependent manner through a novel pathway compendium analysis in which transcriptional regulatory networks of PNF-1-stimulated microvascular endothelial cells are overlaid with literature-derived angiogenic pathways. In this study, we generated three analogues (SC-3-143, SC-3-263, SC-3-13) through systematic transformations to PNF1 to evaluate the effects of electronic, steric, chiral, and hydrogen bonding changes on angiogenic signaling. We then expanded our compendium analysis toward these new compounds. Variables obtained from the compendium analysis were then used to construct a PLSR model to predict endothelial cell proliferation. Our combined approach suggests mechanisms of action involving suppression of VEGF pathways through TGF-β and NR3C1 network activation. Keywords: PNF-1; Pathway compendium analysis; Phthalimide compoundsNational Institutes of Health (U.S.) (Grant R01-DE019935)National Institutes of Health (U.S.) (Grant R01-AR056445

Harnessing systems biology approaches to engineer functional microvascular networks

This is a copy of an article published in Tissue Engineering Part B. © 2010 Mary Ann Liebert, Inc.; Tissue Engineering Part B is available online at: http://online.liebertpub.comDOI: 10.1089/ten.teb.2009.0611Microvascular remodeling is a complex process that includes many cell types and molecular signals. Despite a continued growth in the understanding of signaling pathways involved in the formation and maturation of new blood vessels, approximately half of all compounds entering clinical trials will fail, resulting in the loss of much time, money, and resources. Most pro-angiogenic clinical trials to date have focused on increasing neovascularization via the delivery of a single growth factor or gene. Alternatively, a focus on the concerted regulation of whole networks of genes may lead to greater insight into the underlying physiology since the coordinated response is greater than the sum of its parts. Systems biology offers a comprehensive network view of the processes of angiogenesis and arteriogenesis that might enable the prediction of drug targets and whether or not activation of the targets elicits the desired outcome. Systems biology integrates complex biological data from a variety of experimental sources (-omics) and analyzes how the interactions of the system components can give rise to the function and behavior of that system. This review focuses on how systems biology approaches have been applied to microvascular growth and remodeling, and how network analysis tools can be utilized to aid novel pro-angiogenic drug discovery

Masson's trichrome stain for bone growth in cranial defect at week 9 after treatment with (A) Chitosan, (B) Chitosan + PLAGA microspheres, (C) Chitosan + PLAGA microspheres loaded with FTY720, (D) Chitosan loaded with BMP-2 and (E) Chitosan loaded with BMP-2 + PLAGA microspheres loaded with FTY720.

<p>In the FTY720 groups there is increased bone formation in the defect void space compared to the BMP-2 group and vehicle controls. FTY720 treatment results in the formation of light osteoid bodies (asterisk) and mature bone (arrowhead) (scale bar  = 1 mm).</p

FTY720 enhances vascularization in a critical size cranial defect.

<p>(A) Vascularization in the critical size cranial defect measured using microfil enhanced microCT imaging. (B–F) Volume in the defect region occupied by vessel ingrowth 9 weeks after different treatments (** p<0.01 & *p<0.05 compared to chitosan control; αα p<0.01 & α p<0.05 compared to PLAGA control) MicroCT images showing vessel and bone in-growth at week 9 for animals treated with (B) Chitosan, (C) Chitosan + PLAGA microspheres, (D) Chitosan + PLAGA microspheres loaded with FTY720, (E) Chitosan loaded with BMP-2 and (F) Chitosan loaded with BMP-2 + PLAGA microspheres loaded with FTY720.</p