Peng Khaw

Polyvalent dendrimer glucosamine conjugates prevent scar tissue formation

Dendrimers are hyperbranched macromolecules that can be chemically synthesized to have precise structural characteristics. We used anionic, polyamidoamine, generation 3.5 dendrimers to make novel water-soluble conjugates of D(+)-glucosamine and D(+)-glucosamine 6-sulfate with immuno-modulatory and antiangiogenic properties respectively. Dendrimer glucosamine inhibited Toll-like receptor 4–mediated lipopolysaccharide induced synthesis of pro-inflammatory chemokines (MIP-1α, MIP-1β, IL-8) and cytokines (TNF-α, IL-1β, IL-6) from human dendritic cells and macrophages but allowed upregulation of the costimulatory molecules CD25, CD80, CD83 and CD86. Dendrimer glucosamine 6-sulfate blocked fibroblast growth factor-2 mediated endothelial cell proliferation and neoangiogenesis in human Matrigel and placental angiogenesis assays. When dendrimer glucosamine and dendrimer glucosamine 6-sulfate were used together in a validated and clinically relevant rabbit model of scar tissue formation after glaucoma filtration surgery, they increased the long-term success of the surgery from 30% to 80% (P = 0.029). We conclude that synthetically engineered macromolecules such as the dendrimers described here can be tailored to have defined immuno-modulatory and antiangiogenic properties, and they can be used synergistically to prevent scar tissue formation.

Triamcinolone attenuates macrophage/microglia accumulation associated with NMDA-induced RGC death and facilitates survival of Müller stem cell grafts.

Retinal ganglion cell (RGC) death in glaucoma models is associated with accumulation of activated microglia, a sign of neural degeneration which has been shown to constitute a barrier for transplant cell survival and migration. This study investigated the use of triamcinolone (TA) to control macrophage/microglia accumulation in a model of RGC depletion to create a permissive environment for stem cell grafting. Intravitreal NMDA alone or in combination with TA was used to induce rapid onset of RGC death in 3-4 week old Lister hooded (LH) rat eyes prior to Müller stem cell transplantation into the vitreoretinal space. The effect of NMDA on RGC death and microglial accumulation was assessed immuno-histochemically, whilst electroretinography (ERG) was used to assess RGC function. Post transplantation, survival of grafted cells and their association with microglia were also examined by immunohistochemical methods. Intravitreal injection of NMDA alone resulted in severe macrophage/microglia accumulation associated with extensive RGC death 4-7 days post-treatment. Combination of NMDA with TA significantly reduced microglial numbers in the RGC when compared to NMDA only treated eyes while still depleting the retina of RGC. At the same time, NMDA/TA treatment also caused functional RGC loss as demonstrated by reduction of the scotopic threshold response. Upon transplantation with Müller stem cells, NMDA/TA treatment caused significant reduction in the number of transplant associated macrophage/microglia compared to eyes treated with NMDA alone. On this basis it is proposed that intravitreal injection of TA may be useful as an effective anti-inflammatory agent to control macrophage/microglia accumulation induced by RGC death, thereby creating a retinal environment permissive to cell transplantation studies.