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Plasminogen is a key proinflammatory regulator that accelerates the healing of acute and diabetic wounds
Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
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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2012 (English)In: Blood, ISSN 0006-4971, E-ISSN 1528-0020, Vol. 119, no 24, 5879-5887 p.Article in journal (Refereed) Published
Abstract [en]

Despite decades of research on wound healing, effective biologic agents for the treatment of chronic wounds, especially diabetic wounds, are still lacking. In the present study, we report that the inert plasma protein plasminogen (plg) acts as a key regulatory molecule that potentiates wound healing in mice. Early in the healing process, plg bound to inflammatory cells is transported to the wound area, where the level of plg is increased locally, leading to the induction of cytokines and intracellular signaling events and to a potentiation of the early inflammatory response. Systemic administration of additional plg not only accelerates the healing of acute burn wounds in wild-type mice, but also improves the healing of chronic diabetic wounds in a mouse model of diabetes. Our results suggest that the administration of plg may be a novel therapeutic strategy to treat many different types of wounds, especially chronic wounds such as those caused by diabetes. (Blood. 2012; 119(24):5879-5887)

Place, publisher, year, edition, pages
Washington, USA: American society of hematology , 2012. Vol. 119, no 24, 5879-5887 p.
National Category
Cell and Molecular Biology
Identifiers
URN: urn:nbn:se:umu:diva-58921DOI: 10.1182/blood-2012-01-407825ISI: 000307396500041OAI: oai:DiVA.org:umu-58921DiVA: diva2:550770
Available from: 2012-09-07 Created: 2012-09-06 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Plasminogen in periodontitis and wound repair
Open this publication in new window or tab >>Plasminogen in periodontitis and wound repair
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The plasminogen activator (PA) system plays a critical role in many physiological and pathological processes, such as fibrinolysis, extracellular matrix (ECM) degradation, wound healing, inflammation, and cancer. The key component of the PA system is plasmin, a broad-spectrum serine protease that is derived from its inactive form, plasminogen. The first aim of this thesis research was to determine the role of plasminogen in periodontitis, an inflammatory oral disease. The second aim was to explore the molecular mechanism by which plasminogen contributes to wound healing in the skin. Finally, the third aim was to investigate the possibility of using plasminogen as a treatment for skin wounds, especially for chronic wounds, such as diabetic wounds.

Periodontitis is an oral disease that involves a bacterial infection, the inflammation of the periodontium, and the degradation of gum tissue and alveolar bone. This disease is irreversible and, in severe cases, can lead to loss of teeth due to the degradation of the periodontal ligament and alveolar bone. To study the effects of the PA system on oral health, we monitored the development of periodontitis in plasminogen-deficient mice and plasminogen activator-deficient mice. In control wild-type mice, periodontitis did not occur. However, in plasminogen-deficient mice, periodontitis developed rapidly within 20 weeks after birth. The morphological studies of plasminogen-deficient mice showed the detachment of gingival tissues, resorption of the cementum layer, formation of necrotic tissue, and severe alveolar bone degradation. Immunohistochemical staining showed the massive infiltration of neutrophils into the periodontal tissues. Interestingly, doubly deficient mice lacking both tissue-type plasminogen activator (tPA) and urokinase-type PA (uPA) developed periodontitis at a similar rate as the plasminogen-deficient mice, but mice lacking only tPA or uPA remained healthy. The intravenous injection of human plasminogen for 10 days into plasminogen-deficient mice led to the absorption of necrotic tissue, the diminution of inflammation, and the full regeneration of gum tissues. Notably, there was also partial re-growth of degraded alveolar bone.

The wound healing process consists of three overlapping phases: inflammatory, proliferative, and remodeling. It has been postulated that the PA system plays an integral role in this process, and a lack of plasminogen leads to delayed wound healing in mice. To study the role of the PA system in wound healing, we monitored the responses of wild-type, plasminogen-deficient and diabetic mice to incision and burn wounds. We found that in addition to being delayed, the wound healing process in plasminogen-deficient mice was only superficial in nature. The plasminogen-deficient mice were unable to clear the provisional matrix after the formation of granulation tissue, and an extensive fibrin deposition. In addition, persistent inflammation was still present subcutaneously in these mice 60 days after introduction of the wound.

The essential role of plasminogen in burn and incision wounds healing was further confirmed by reconstitution experiments. Both intravenous and subcutaneous administrations of human plasminogen to plasminogen-deficient mice led to a restored healing rate and wound maturation that was comparable to those of wild-type mice. We also demonstrated that plasminogen supplementation of plasminogen to wild-type and diabetic mice significantly improved the healing of cutaneous wounds. Plasminogen levels were not only temporally increased during the inflammation phase but also spatially concentrated at the site of the wound. The wound-specific accumulation of plasminogen after systemic supplementation is mainly due to the transportation of plasminogen by neutrophils and macrophages. Furthermore, the increased expression of interleukin 6 and the enhanced phosphorylation of STAT3 were observed in the wound after plasminogen treatment. These data indicate that plasminogen acts as a key pro-inflammatory regulator. It enhances pro-inflammatory cytokines and activates intracellular signaling events during wound healing.

Taken together, the data obtained during the course of this project indicate that plasminogen is crucial for oral health in mice. We also demonstrate that supplementation of plasminogen to mice with periodontitis results in healing of gum tissues and significant re-growth of alveolar bone. Therefore, plasminogen may be a new drug that will be competitive to currently used oral health-related procedures, such as implantations and surgeries. Furthermore, we demonstrate for the first time that, in addition to its role in extracellular matrix degradation, plasminogen is a key pro-inflammatory factor that accumulates at the wound and potentiates the early inflammatory response during wound healing. Based on our findings, we propose the administration of plasminogen as a novel therapeutic strategy for the treatment of different types of wounds, including chronic diabetic wounds.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2013. 49 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1549
National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-63818 (URN)978-91-7459-547-5 (ISBN)
Public defence
2013-02-01, N450, Naturvetarhuset, Umeå universitet, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2013-01-11 Created: 2013-01-08 Last updated: 2013-01-11Bibliographically approved
2. 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.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1575
Keyword
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
Identifiers
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)
Opponent
Supervisors
Funder
Swedish Research Council
Available from: 2013-05-03 Created: 2013-04-25 Last updated: 2013-05-21Bibliographically approved

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Shen, YueMikus, PeterSulniute, RimaWilczynska, MalgorzataNy, TorLi, Jinan

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