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Plasminogen is a critical regulator of cutaneous wound healing
Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics. (Företagsforskarskolan, Industrail Doctoral School)
Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Wound healing is a well-orchestrated, complex process leading to the repair of injured tissues. Two major proteolytic systems, the matrix metalloproteases and the plasminogen activator system, are involved in this process. The lack of plasminogen (plg) has previously been reported to cause a delay in wound closure in mice, and to be complemented by matrix metalloproteases. However, our previous finding that tympanic membrane perforations in plgdeficient mice do not heal indicated that plg has more important function in wound healing than previously regarded. In later studies, we have found that plg accumulates in the wound early during the healing process and potentiates the inflammatory response and the healing. In the present study, we have used incision and burn wound models in wild-type and plgdeficient mice to further investigate the role of plg in the later phases of the healing process, including its role after re-epithelization. In addition to the earlier observed delay of wound reepithelizationin plg-deficient mice, we have found that the tissue remodeling processes that take place after re-epithelization is also impaired in these mice. By morphological and immunohistochemical analyses, we found that plg-deficient mice had delayed granulationtissue formation, and were unable to clear the provisional matrix. Extensive fibrin deposition and persistent neutrophil infiltration even at day 60 post-wounding indicate that the inflammation was present subcutaneously in plg-deficient mice even at later time points. Importantly, intravenous or subcutaneous supplementation of plg-deficient mice by human plg led to a restored healing rate, and a healing pattern that was comparable to that in wildtype mice. Therefore, in addition to its important function in early stages of cutaneous wound healing, plg is also crucial for later phases, by clearing fibrin deposits and resolving inflammation after full re-epithelization of the wound. Our results suggest that plg may be a potential therapeutic agent for improving the healing of different types of skin wounds.

Keyword [en]
plasminogen, wound, healing, skin
National Category
Basic Medicine Dermatology and Venereal Diseases
URN: urn:nbn:se:umu:diva-68761OAI: diva2:617976
Swedish Research Council
Available from: 2013-04-25 Created: 2013-04-25 Last updated: 2013-05-06Bibliographically approved
In thesis
1. Plasminogen: a novel inflammatory regulator that promotes wound healing
Open this publication in new window or tab >>Plasminogen: a novel inflammatory regulator that promotes wound healing
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The plasminogen activator (PA) system has been shown to be intimately involved in wound healing. However, the role of this system in the initiation and resolution of inflammation during healing process remained to be determined. The aims of this thesis were to investigate the molecular mechanism underlying the interaction between the PA system and the inflammatory system during wound healing and to explore the therapeutic potential of plasminogen in various wound-healing models.

The role of plasminogen in the inflammatory phase of the healing process of acute and diabetic wounds was studied first. Our data showed that administration of additional plasminogen to wild-type mice accelerates the healing of acute wounds. After injury, both endogenous and exogenous plasminogen are bound to inflammatory cells and are transported to the wound site, which leads to activation of inflammatory cells. In diabetic db/db mice, wound-specific accumulation of plasminogen does not take place and the inflammatory response is impaired. However, when additional plasminogen is injected, plasminogen accumulates in the wound, the inflammatory response is enhanced, the signal transduction cascade is activated and the healing rate is significantly increased. These results indicate that administration of plasminogen may be a novel therapeutic strategy to treat different types of wounds, especially chronic wounds in diabetes.

The role of plasminogen at the later stage of wound healing was also studied in plasminogen-deficient mice. Our data showed that even if re-epithelialization is achieved in these mice, a prolonged inflammatory phase with abundant neutrophil accumulation and persistent fibrin deposition is observed at the wound site. These results indicate that plasminogen is also essential for the later phases of wound healing by clearing fibrin and resolving inflammation.

The functional role of two physiological PAs during wound healing was further studied in a tympanic membrane (TM) wound-healing model. Our data showed that the healing process was clearly delayed in urokinase-type PA (uPA)-deficient mice but not in tissue-type PA (tPA)-deficient mice. Less pronounced keratinocyte migration, abundant neutrophil accumulation and persistent fibrin deposition were observed in uPA-deficient mice. These results indicate that uPA plays a central role in the generation of plasmin during the healing of TM perforations.

Finally the therapeutic potential of plasminogen in the TM wound-healing model was studied. Our data showed that local injection of plasminogen restores the ability to heal TM perforations in plasminogen-deficient mice in a dose-dependent manner. Plasminogen supplementation also potentiates healing of acute TM perforations in wild-type mice, independent of the administration method used. A single local injection of plasminogen in plasminogen-deficient mice can initiate healing of chronic TM perforations resulting in a closed TM with a continuous but rather thick outer keratinocyte layer. Three plasminogen injections lead to a completely healed TM with a thin keratinizing squamous epithelium covering a connective tissue layer that can start to reorganize and further mature to its normal appearance. In conclusion, our results suggest that plasminogen is a promising drug candidate for the treatment of chronic TM perforations in humans. 

Taken together, our data indicate that plasminogen is a novel inflammatory regulator that promotes wound healing.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2013. 58 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1575
Plasminogen, inflammation, wound healing, diabetic wounds, tympanic membrane perforations
National Category
Basic Medicine Otorhinolaryngology Dermatology and Venereal Diseases Endocrinology and Diabetes
Research subject
Medical Biochemistry
urn:nbn:se:umu:diva-68755 (URN)978-91-7459-651-9 (ISBN)
Public defence
2013-05-24, KB3A9, KBC-huset, Umeå University, Umeå, 10:00 (English)
Swedish Research Council
Available from: 2013-05-03 Created: 2013-04-25 Last updated: 2013-05-21Bibliographically approved

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