Wound healing is an evolutionarily conserved, complex, multicellular process that, in skin, aims at barrier restoration. This process involves the coordinated efforts of several cell types including keratinocytes, fibroblasts, endothelial cells, macrophages, and platelets. The migration, infiltration, proliferation, and differentiation of these cells will culminate in an inflammatory response, the formation of new tissue and ultimately wound closure. This complex process is executed and regulated by an equally complex signaling network involving numerous growth factors, cytokines and chemokines. Of particular importance is the epidermal growth factor (EGF) family, transforming growth factor beta (TGF-beta) family, fibroblast growth factor (FGF) family, vascular endothelial growth factor (VEGF), granulocyte macrophage colony stimulating factor (GM-CSF), platelet-derived growth factor (PDGF), connective tissue growth factor (CTGF), interleukin (IL) family, and tumor necrosis factor-alpha family. Currently, patients are treated by three growth factors: PDGF-BB, bFGF, and GM-CSF. Only PDGF-BB has successfully completed randomized clinical trials in the Unites States. With gene therapy now in clinical trial and the discovery of biodegradable polymers, fibrin mesh, and human collagen serving as potential delivery systems other growth factors may soon be available to patients. This review will focus on the specific roles of these growth factors and cytokines during the wound healing process.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1524-475X.2008.00410.x

Growth factors and cytokines in wound healing.

Macrophages are innate immune cells with well-established roles in the primary response to pathogens, but also in tissue homeostasis, coordination of the adaptive immune response, inflammation, resolution, and repair. These cells recognize danger signals through receptors capable of inducing specialized activation programs. The classically known macrophage activation is induced by IFN-gamma, which triggers a harsh proinflammatory response that is required to kill intracellular pathogens. Macrophages also undergo alternative activation by IL-4 and IL-13, which trigger a different phenotype that is important for the immune response to parasites. Here we review the cellular sources of these cytokines, receptor signaling pathways, and induced markers and gene signatures. We draw attention to discrepancies found between mouse and human models of alternative activation. The evidence for in vivo alternative activation of macrophages is also analyzed, with nematode infection as prototypic disease. Finally, we revisit the concept of macrophage activation in the context of the immune response.

Alternative Activation of Macrophages: An Immunologic Functional Perspective

Cell-adhesion molecules, once believed to function primarily in tethering cells to extracellular ligands, are now recognized as having broader functions in cellular signalling cascades. The CD44 transmembrane glycoprotein family adds new aspects to these roles by participating in signal-transduction processes — not only by establishing specific transmembrane complexes, but also by organizing signalling cascades through association with the actin cytoskeleton. CD44 and its associated partner proteins monitor changes in the extracellular matrix that influence cell growth, survival and differentiation.

CD44: From adhesion molecules to signalling regulators

The TNF receptor 1-associated protein TRADD signals cell death and NF-κB activation

Dendritic cells: unique leukocyte populations which control the primary immune response.

A Role for Th1 and Th2 Cells in the Immunopathogenesis of Atopic Dermatitis

Medication use and the risk of Stevens-Johnson syndrome or toxic epidermal necrolysis

Background Tacrolimus (FK 506) is an effective immunosuppressant drug for the prevention of rejection after organ transplantation, and preliminary studies suggest that topical application of tacrolimus is effective in the treatment of atopic dermatitis. Methods We conducted a randomized, double-blind, multicenter study that compared 0.03 percent, 0.1 percent, and 0.3 percent tacrolimus ointment with vehicle alone in patients with moderate-to-severe atopic dermatitis. The ointment was applied twice daily to a defined, symptomatic area of 200 to 1000 cm2 of skin for three weeks. The primary end point was the change in the summary score for erythema, edema, and pruritus between the first and last days of treatment. Results After three weeks of treatment, the median percentage decrease in the summary score for dermatitis on the trunk and extremities was 66.7 percent for the 54 patients receiving 0.03 percent tacrolimus, 83.3 percent for the 54 patients receiving 0.1 percent tacrolimus, 75.0 percent for the 51...

/pdf/a-short-term-trial-of-tacrolimus-ointment-for-atopic-p91rocuapy.pdf

A short-term trial of tacrolimus ointment for atopic dermatitis. European Tacrolimus Multicenter Atopic Dermatitis Study Group

Lesional expression of interferon-γ in atopic eczema

• Little work has been carried out on the epidemiology of the two serious skin reactions—toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS). We collected details of all the hospitalized cases of TEN and SJS in the Federal Republic of Germany for the years 1981 through 1985 inclusive. Inquiries by telephone, letter, and personal visits produced an overall response of 91%; 259 cases of TEN and 315 cases of SJS were identified. From these data, we were able to calculate an overall annual risk of 0.93 and 1.1 per million for TEN and SJS, respectively. The average age group was higher for TEN (63 years) than for SJS (25 years). Women are markedly more at risk for TEN in the ratio of 2:1, these figures being reversed for SJS. The mortality was 34% (87/259) for TEN and only 1% (2/315) for SJS. An association with previous medication defined as "definite, probable, possible" could be established for 89% of cases of TEN and 54% of cases of SJS. The drugs most commonly involved were antibiotics (TEN, 40%; SJS, 34%), followed by the analgesics (TEN, 23%; SJS, 33%). As with the drug groups, the incidences being based on the defined daily doses, were high for sulfonamides, β-lactam antibiotics, and some nonsteroidal anti-inflammatory drugs. ( Arch Dermatol. 1991;127:839-842)

Erwin Schöpf

Papers

A Role for Th1 and Th2 Cells in the Immunopathogenesis of Atopic Dermatitis

Medication use and the risk of Stevens-Johnson syndrome or toxic epidermal necrolysis

A short-term trial of tacrolimus ointment for atopic dermatitis. European Tacrolimus Multicenter Atopic Dermatitis Study Group

Lesional expression of interferon-γ in atopic eczema

Toxic epidermal necrolysis and Stevens-Johnson syndrome. An epidemiologic study from West Germany.