The progression of inflammation parallels the dermal angiogenesis in a keratin 14 IL-4-transgenic model of atopic dermatitis.

The role angiogenesis plays in atopic dermatitis is not well understood. The authors previously demonstrated ultrastructurally dermal microvascular angiogenesis in the IL-4-transgenic mouse model of atopic dermatitis. Here, they determine the angiogenic factors involved in dermal microvascular angiogenesis, regulatory function of inflammatory cytokines on the VEGF-A production, and microvascular permeability in this model. Computer-assisted photometric analyses for immunofluorescence-labeled CD31 demonstrated a progressive increase in blood vessel number, diameter, and percent dermal areas occupied by CD31(+) vessels as the disease evolves in transgenic mice from before disease onset through early and late skin lesions. Similar findings were documented for VEGR2(+) vessels. Quantification of skin angiogenic factor mRNAs showed progressive increase of transcripts of VEGF-A, but not VEGF-B, VEGF-C, or VEGF-D. ELISA showed a similar increase of VEGF-A in the serum and skin of transgenic mice. IL-6 and IFN-gamma stimulated VEGF-A mRNA production in the skin and in primary keratinocytes of transgenic mice. Other skin angiogenic factors that increased included Ang-1, Ang-2, GBP-1, and VE-cadherin. Microvascular leakage began in the transgenic mouse skin before disease onset and peaked in the late stage. In conclusion, IL-6 and IFN-gamma may play important roles in upregulation of VEGF-A, along with other pro-angiogenic factors, to induce dermal microvascular angiogenesis.

Targeting TNFalpha rapidly reduces density of dendritic cells and macrophages in psoriatic plaques with restoration of epidermal keratinocyte differentiation.

BACKGROUND: The cytokine network theory for psoriasis postulates a key role for TNFalpha in mediating inflammation and altered epidermal differentiation. OBJECTIVE: This study defines responses following administration of adalimumab, a TNFalpha inhibitor, in pre-psoriatic skin (PN) and lesional psoriatic plaques (PP) skin. METHODS: PN and PP skin before and after treatment were biopsied at days 2, 7, 28 and 84 (n=6 different patients). Cryosections were immunohistochemically stained to detect TNFalpha and other relevant markers in epidermal and dermal compartments. Detection of apoptosis utilized antibody specific for activated caspase 3. Semiquantitative assessments and statistical analysis was performed for each staining profile. RESULTS: TNFalpha+ cells were increased in PP skin. PP skin was also characterized by a four-fold increase in number of CD68+ macrophages as well as eight-fold increase in CD11c+ dermal dendritic cells (DCs) compared to PN skin. By two-color immunofluorescence staining, both CD68+ cells as well as CD11c+ cells expressed TNFalpha. Following initiation of adalimumab therapy, CD11c+ cells, significantly decreased in PP skin at days 7, 28, and 84, while CD68+ and CD14+ cells decreased at days 28 and 84. Other markers for DCs (CD83, CD86) showed decreases at days 7, 28, and 84. Reduction in DCs, macrophages or T cells was not accompanied by increased activated caspase 3-positive cells. When a keratinocyte terminal differentiation marker was examined, adalimumab triggered rapid restoration of loricrin expression (beginning on day 2), with loss of aberrant differentiation marker, keratin 17 (K17). CONCLUSION: Adalimumab impacts dermal-based immunocytes, and the epidermal compartment also responds by restoration of normal differentiation without detectable apoptosis.

Lessons learned from psoriatic plaques concerning mechanisms of tissue repair, remodeling, and inflammation.

Following injury, skin establishes a balance between too little inflammation increasing risk of infection, and excessive inflammation contributing to delayed wound healing and scarring. Mounting evidence indicates both initiation and termination of inflammation involve active mechanisms. Not only does inflammation itself seem to be a paradox because inflammatory responses are both essential and potentially detrimental, but one chronic inflammatory skin disease (e.g. psoriasis) presents additional paradoxes. While plaques share several factors with wound healing, two understudied and puzzling aspects include why do not inflamed plaques more frequently transform?; and why do not plaques result in scarring? To get at these questions, we review responses involved in wound repair. Oral mucosa was probed because, like fetal skin, wound repair is characterized by its rapidity, low inflammation, and scarless resolution. Active roles for macrophages as both initiators and terminators of inflammation are highlighted. Therapeutic implications are discussed regarding psoriasis and pyoderma gangrenosum. Based on biochemical and immunohistochemical considerations linking psoriatic plaques to hard palate, a novel metaplastic model is presented. We hypothesize saliva and chronic trauma contribute to a constitutive epithelial program where keratinocyte proliferation is more intense prior to differentiation, accompanied by keratin 16 expression in hard palate, thereby resembling plaques. Rather than viewing psoriasis as a nonspecific response to inflammation, we postulate a metaplastic switch by which prepsoriatic skin is converted to a distinct adult tissue type resembling hard palate. In summary, many lessons can be learned by focusing on complex processes involved in regulation of inflammation, tissue repair, and remodeling.