Coordinate expression of NGF and α-smooth muscle actin mRNA and protein in cutaneous wound tissue of developing and adult rats

Abstract

Nerve growth factor (NGF) is synthesized in cutaneous wound tissue, and its higher levels in the neonate may contribute to more efficient wound healing. We used in situ hybridization and immunohistochemistry to define NGF mRNA and protein expression in intact skin and following excision wounding in neonatal and adult rats. To determine whether NGF is associated with wound contractile fibroblasts (myofibroblasts), we also examined expression of α-smooth muscle actin (α-SMA) mRNA and protein, established markers for these cells. In intact skin, NGF mRNA and protein were present in vascular and arrector pili smooth muscle, hair follicle sheath cells, keratinocytes, and hypodermal fibroblasts. Neonatal adipocytes and Schwann cells also expressed NGF mRNA and protein, while adult adipocytes and Schwann cells displayed only NGF-ir. Following wounding, NGF mRNA expression was exuberant in these cell types, and increased similarly at both ages and appeared de novo in skeletal muscle cells. Additionally, both NGF mRNA and protein were present in macrophages and myofibroblasts, and expression in myofibroblasts was significantly greater in neonates. Wound myofibroblasts also expressed α-SMA. Surprisingly, after wounding α-SMA mRNA and protein were present in essentially all cells in which NGF mRNA was detected. We conclude that NGF expression is enhanced in many cell types after wounding, but greater NGF synthesis in neonates appears to be due to a more robust myofibroblast response. In addition, cell types which demonstrated NGF mRNA also expressed α-SMA, and staining for both markers increased following wounding, suggesting synthesis of both proteins is regulated in a coordinated fashion.

Macrophage Depletion Suppresses Sympathetic Hyperinnervation following Myocardial Infarction

“…Rather, it is likely to have occurred secondary to the depletion in macrophages. Myofibroblasts transdifferentiate from several cell types including fibroblasts and pericytes [21,27,50]. Development of the myofibroblast phenotype requires the presence of various secreted proteins including TGF-β [11,13], which can be released by macrophages [3].…”

“…A second set of sections adjacent to the DBH-immunostained series was stained for CD68 (1:200, mouse monoclonal, MAB 1435, Chemicon), a marker for tissue macrophages and blood monocytes [40]. A third set was stained for α-smooth muscle actin (1/200, mouse monoclonal 1A4, Sigma, St Louis, MO, USA), which identifies myofibroblasts [27,53]. A fourth set of adjacent sections was immunostained for the T cell antigen receptor TCR α/β (1:100, mouse monoclonal, clone R73, Serotec, Oxford, UK).…”

“…To determine the contribution of the predominant NGF-expressing cell types in the vicinity of the infarct [8,26,27,43], we analyzed the NGF expression of macrophages, myofibroblasts and T cells. In ventricles with sham ligations, no macrophages were observed below the untied ligature and therefore did not contribute to NGF expression in the control ventricle (Fig.…”

“…Cytokines present in inflammatory environments are known to promote activation of macrophages [1] and in vitro macrophage activation induces NGF expression [8], suggesting that macrophages could contribute to sympathetic hyperinnervation. Myofibroblasts are thought to transdifferentiate from fibroblasts, pericytes, and possibly macrophages [27,50], and to promote wound healing through contraction and collagen deposition. Myofibroblasts, as well as another inflammatory wound cell, the T cell, are also known to synthesize NGF [26], making them possible contributors to the induction of sympathetic hyperinnervation.…”

Conceptual novelities in atherogenesis: smooth muscle cells, adventitia, and adipose tissue

“…Further work on molecular and cellular mechanisms of wound-healing phenotypes, including scarring, keloid and ulceration, is required for the better understanding of intima-based vascular occlusion and rupture in atherosclerosis. Intriguingly, the antiatherosclerotic factors es-trogen and transforming growth factor-β (8) accelerate skin wound healing (9), and a potential atheroprotective factor, nerve growth factor (10), also exerts healing effect in both skin wounds (11,12) and corneal ulcers (13).…”