IntroductionIL6 has major functions in inflammatory reactions of the body. 1,2 Mice with a targeted inactivation of the IL6 gene are completely protected in animal models of rheumatoid arthritis 3,4 and multiple sclerosis. 5 Furthermore, regenerative reactions such as wound healing and liver regeneration are severely compromised in IL6 Ϫ/Ϫ mice. 6 A soluble form of the IL6R can bind IL6 with the same affinity as the membrane-bound form and the complex of IL6 and the soluble IL6R (sIL6R) can induce signaling in a process called IL6 transsignaling. 7,8 Because the IL6R is only sparely expressed, IL6 transsignaling dramatically increases the number of potential IL6 target cells. 9 This is relevant for inflammatory processes in vivo, because endothelial cells and smooth muscle cells, which play key roles in inflammation, lack IL6R expression. The interest in the role of IL6 in inflammatory processes has recently been intensified by the finding that the differentiation of TH 17 cells, which is a prerequisite for inflammatory damage during autoimmune disease, shows a dependence on IL6 in combination with TGF␤. 10 Recent studies with animal models of inflammatory bowel disease, 11,12 peritonitis, 13 rheumatoid arthritis, 14,15 and inflammatory colon cancer 16 suggest that IL6 transsignaling serves as the major proinflammatory paradigm of IL6 signaling under pathophysiologic conditions.To further analyze the relevance of IL6-transsignaling in vivo we generated a mouse model in which IL6-transsignaling is specifically abrogated. There have been reports describing the generation of knock-in mice with noncleavable L-selectin and noncleavable TNF-␣, showing that shedding of membrane proteins was important for antigen-stimulated lymphocyte migration and for secondary lymphoid organ architecture. 17,18 Such a strategy is impractical in the case of the sIL6R because its generation is complex and can be generated by ectodomain shedding as well as by translation from an alternatively spliced mRNA. Furthermore, shedding of the IL6R was also shown to occur at multiple cleavage sites and performed by multiple and distinct sheddase activities. [19][20][21][22] We therefore decided to generate transgenic mice overexpressing the sgp130Fc-protein that had been demonstrated to completely block IL6 transsignaling without affecting activities via the membrane bound IL6R. Blocking of IL6 transsignaling via sgp130Fc is independent of the mode of sIL6R generation. The need for a large molar excess of the sgp130Fc-protein necessitated the development of a codon optimization strategy that should be relevant for the construction of all animal models, which are based on the overexpression of heterologous proteins.The data presented here clearly show that sgp130Fc transgenic mice display an IL6-transsignaling knockout-like phenotype and establish them as the only possible in vivo model of this IL6-transsignaling paradigm. Here, we demonstrate in the air-pouch model of inflammatory activation that the transition from the neutrophil-dominated phase...

IL-6 is implicated in the pathogenesis

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Skin wound closure occurs when keratinocytes migrate from the edge of the wound and re-epithelialize the epidermis. Their migration takes place primarily before any vascularization is established, that is, under hypoxia, but relatively little is known regarding the factors that stimulate this migration. Hypoxia and an acidic environment are well-established stimuli for cancer cell migration. The carbonic anhydrases (CAs) contribute to tumor cell migration by generating an acidic environment through the conversion of carbon dioxide to bicarbonate and a proton. On this basis, we explored the possible role of CAs in tissue regeneration using mouse skin wound models. We show that the expression of mRNAs encoding CA isoforms IV and IX are increased (~25 × and 4 ×, respectively) during the wound hypoxic period (days 2–5) and that cells expressing CAs form a band-like structure beneath the migrating epidermis. RNA-Seq analysis suggested that the CA IV-specific signal in the wound is mainly derived from neutrophils. Due to the high level of induction of CA IV in the wound, we treated skin wounds locally with recombinant human CA IV enzyme. Recombinant CA IV significantly accelerated wound re-epithelialization. Thus, CA IV could contribute to wound healing by providing an acidic environment in which the migrating epidermis and neutrophils can survive and may offer novel opportunities to accelerate wound healing under compromised conditions.

The R-ras gene encodes a small GTPase that is a member of the Ras family. Despite close sequence similarities, R-Ras is functionally distinct from the prototypic Ras proteins; no transformative activity and no activating mutations of R-Ras in human malignancies have been reported for it. R-Ras activity appears inhibitory towards tumour proliferation and invasion, and to promote cellular quiescence. Contrary to this, using mice with a deletion of the R-ras gene, we found that R-Ras facilitates DMBA/TPA-induced skin tumour induction. The tumours appeared in wild-type (WT) mice on average 6 weeks earlier than in R-Ras knockout (R-Ras KO) mice. WT mice developed almost 6 times more tumours than R-Ras KO mice. Despite strong R-Ras protein expression in the dermal blood vessels, no R-Ras could be detected in the epidermis from where the tumours arose. The DMBA/TPA skin tumourigenesis-model is highly dependent upon inflammation, and we found a greatly attenuated skin inflammatory response to DMBA/TPA-treatment in the R-Ras KO mice in the context of leukocyte infiltration and proinflammatory cytokine expression. Thus, these data suggest that despite its characterised role in promoting cellular quiescence, R-Ras is pro-tumourigenic in the DMBA/TPA tumour model and important for the inflammatory response to DMBA/TPA treatment.

Growth factors, chemokines, and cytokines responsible for tissue regeneration have been identified. Their therapeutic usage in humans is almost nonexistent because of the difficulty in maintaining their bioactivity in the proteaserich milieu of injured tissues. Safety concerns have ruled out the systemic administration of growth factors. Angiogenic vasculature forming in the regenerating tissues has unique molecular structures, so-called "zip/postal codes". These unique vascular zip codes provide an opportunity for target-specific delivery of systemically administered therapeutics to tissue injuries by ligands (using peptides or antibodies as a delivery vehicle) binding to these specific structures. Molecules with therapeutic potential can also be packaged into nanocarriers which then can be targeted to the desired location by placing large number of peptides on the nanoparticle. The targeted delivery of systemically administered recombinant proteins to the injured tissue is hopefully rapidly advanced to provide new therapeutics to regenerative medicine.

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Objective: VEGFA (Vascular endothelial growth factor A) and its receptor VEGFR2 (vascular endothelial growth factor receptor 2) drive angiogenesis in several pathologies, including diabetic retinopathy, wet age-related macular degeneration, and cancer. Studies suggest roles for HSPGs (heparan sulfate proteoglycans) in this process, although the nature of this involvement remains elusive. Here, we set to establish the role of the HSPG SDC4 (syndecan-4) in pathological angiogenesis. Approach and Results: We report that angiogenesis is impaired in mice null for SDC4 in models of neovascular eye disease and tumor development. Our work demonstrates that SDC4 is the only SDC whose gene expression is upregulated during pathological angiogenesis and is selectively enriched on immature vessels in retinas from diabetic retinopathy patients. Combining in vivo and tissue culture models, we identified SDC4 as a downstream mediator of functional angiogenic responses to VEGFA. We found that SDC4 resides at endothelial cell junctions, interacts with vascular endothelial cadherin, and is required for its internalization in response to VEGFA. Finally, we show that pathological angiogenic responses are inhibited in a model of wet age-related macular degeneration by targeting SDC4. Conclusions: We show that SDC4 is a downstream mediator of VEGFA-induced vascular endothelial cadherin internalization during pathological angiogenesis and a potential target for antiangiogenic therapies.