Accelerated skin wound healing in plasminogen activator inhibitor-1-deficient mice - PubMed (original) (raw)

Accelerated skin wound healing in plasminogen activator inhibitor-1-deficient mice

J C Chan et al. Am J Pathol. 2001 Nov.

Abstract

Components of the fibrinolytic system have been implicated in cell migratory events associated with tissue remodeling. Studies in plasminogen-deficient mice (PG(-/-)) indicated that skin wound healing is impaired, but is resolved with an additional fibrinogen deficiency. Plasminogen activator inhibitor-1 (PAI-1) expression by keratinocytes has been identified shortly after wound injury. PAI-1 expression could affect wound healing by regulating the fibrinolytic environment of the wounded area, as well as influencing events associated with cell attachment and detachment through interactions with matrix proteins. The present study directly assesses PAI-1 involvement in skin wound healing through analyses of a dermal biopsy punch model in PAI-1-deficient (PAI-1(-/-) mice. While the cellular events associated with the healing process are similar between wild-type (WT) and PAI-1(-/-) mice, the rate of wound closure is significantly accelerated in PAI-1(-/-) mice.

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Figures

Figure 1.

Kinetics of skin wound healing in _PAI-1_−/− and WT mice. The percentage area of the wound (width × length) remaining as a function of time after skin incision in PAI-1 −/− (•) and WT (▪) mice. At least 4 mice/genotype/time point are graphically represented and expressed as the average ± SE. P values at days 3–9 < 0.05.

Figure 2.

Histological analysis of a skin lesion 5 days following administration of the wound in _PAI-1_−/− and WT mice (×40–100). H&E staining of a newly connected and thickened neoepithelial layer underneath the formed matrix, which is now attached only at a small, single point (*) in PAI-1 −/− mice (a) (×40). Under the same magnification, the leading edges of the migrating epithelium (*) have not yet associated in WT mice skin wounds (b). The underlying dermal layer in PAI-1 −/− mice (c) is not yet developed although Masson’s trichrome staining indicates the initiation of collagen deposition (*) in this area (×40). Some collagen is also present under the granulation tissue (arrow) of WT mice lesions (×40) (d). Ayoub-Shklar staining demonstrates that some erythrocytes (arrow) are still present in the immature and unconnected area in PAI-1 −/− mice (e) (×100) but is much more substantial in the WT mice wound (f) (arrows ×100).

Figure 3.

Immunohistochemical analysis of a skin lesion 5 days following wound placement in _PAI-1_−/− and WT mice. Anti-fibrin(ogen) immunostaining shows diffuse fibrin deposition (brown) within the healing lesion in PAI-1 −/− mice (a) and between the wound and the provisional matrix (arrow), whereas fibrin deposition in the WT mice skin lesions (b) remains generally unresolved (×100). Similarly, CD45-positive leukocytes are still prevalent in the granulation tissue (*) under the matrix of the WT mice lesions, (d) but not as prevalent in lesions from PAI-1 −/− mice (c) (×400). VEGF expression was prominent in the granulation tissue (*) of skin wounds from WT mice (f) but scarce in wounds from PAI-1 −/− mice (e) (×100).

Figure 4.

Histological comparisons of healed skin wounds (a,c,e,g) versus non-wounded skin (b,d,f,h) in _PAI-1_−/− mice (×200). H&E staining demonstrating a significantly thickened epidermal layer (*) within the healed lesion (a) as compared to uninjured skin (b). Invaginations of epidermal epithelium (arrow), which will ultimately result in the development of hair follicle structure, are observed. Masson’s Trichrome staining indicates premature, diffuse deposition of collagen (blue) (c) as compared to the rich organization of collagen fibers (*) in non-wounded skin (d). Ayoub Shklar staining demonstrates a thickened keratinized layer above the epidermis (arrow) (e). PAS staining demonstrates that the reticular fiber structure (pink) is still cellular and does not yet demonstrate the organized basement membrane (g) as compared to the more non-cellular reticular layer of fibrous network (*) seen in the non-wounded skin (h). These findings are similar to those observed in healed WT skin lesions.

Figure 5.

Immunohistochemical analysis of healed (a, c, e) and non-wounded skin (b, d, f) in _PAI-1_−/− mice (×200). Anti-α-actin immunostaining demonstrates a reorganization of α-actin positive cells with particular staining in the deep fibroblast-rich reticular region (*) of the healed lesion (a) compared to a more scattered and less localized presence in the dermis of non-wounded skin (b). There is no longer a significant presence of extravascular fibrin(ogen) (c) or CD45-positive leukocytes (e) within the healed area although nonspecific staining of the sebaceous glands is typical for the latter stain as demonstrated in f. Fibrinogen in non-wounded skin is primarily associated within the vasculature (d).

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Accelerated skin wound healing in plasminogen activator inhibitor-1-deficient mice - PubMed (original) (raw)