Dhall Sandeep, Do Danh, Garcia Monika, Wijesinghe Dayanjan Shanaka, Brandon Angela, Kim Jane, Sanchez Antonio, Lyubovitsky Julia, Gallagher Sean, Nothnagel Eugene A, Chalfant Charles E, Patel Rakesh P, Schiller Neal, Martins-Green Manuela
Departments of Cell Biology and Neuroscience, University of California Riverside, Riverside, California, United States of America; Bioengineering Interdepartmental Graduate Program, University of California Riverside, Riverside, California, United States of America.
Division of Biomedical Sciences, University of California Riverside, Riverside, California, United States of America.
PLoS One. 2014 Oct 14;9(10):e109848. doi: 10.1371/journal.pone.0109848. eCollection 2014.
Chronic wounds have a large impact on health, affecting ∼6.5 M people and costing ∼$25B/year in the US alone. We previously discovered that a genetically modified mouse model displays impaired healing similar to problematic wounds in humans and that sometimes the wounds become chronic. Here we show how and why these impaired wounds become chronic, describe a way whereby we can drive impaired wounds to chronicity at will and propose that the same processes are involved in chronic wound development in humans. We hypothesize that exacerbated levels of oxidative stress are critical for initiation of chronicity. We show that, very early after injury, wounds with impaired healing contain elevated levels of reactive oxygen and nitrogen species and, much like in humans, these levels increase with age. Moreover, the activity of anti-oxidant enzymes is not elevated, leading to buildup of oxidative stress in the wound environment. To induce chronicity, we exacerbated the redox imbalance by further inhibiting the antioxidant enzymes and by infecting the wounds with biofilm-forming bacteria isolated from the chronic wounds that developed naturally in these mice. These wounds do not re-epithelialize, the granulation tissue lacks vascularization and interstitial collagen fibers, they contain an antibiotic-resistant mixed bioflora with biofilm-forming capacity, and they stay open for several weeks. These findings are highly significant because they show for the first time that chronic wounds can be generated in an animal model effectively and consistently. The availability of such a model will significantly propel the field forward because it can be used to develop strategies to regain redox balance that may result in inhibition of biofilm formation and result in restoration of healthy wound tissue. Furthermore, the model can lead to the understanding of other fundamental mechanisms of chronic wound development that can potentially lead to novel therapies.
慢性伤口对健康有重大影响，仅在美国就影响约650万人，每年花费约250亿美元。我们之前发现，一种基因改造小鼠模型表现出与人类问题伤口类似的愈合受损情况，且有时伤口会变成慢性伤口。在此我们展示这些受损伤口如何以及为何会变成慢性伤口，描述一种能随意促使受损伤口转变为慢性伤口的方法，并提出人类慢性伤口发展涉及相同过程。我们假设氧化应激水平加剧对慢性化的起始至关重要。我们发现，在受伤后很早的时候，愈合受损的伤口中活性氧和氮物种水平升高，而且和人类一样，这些水平会随年龄增长而增加。此外，抗氧化酶的活性并未升高，导致伤口环境中氧化应激积累。为诱导慢性化，我们通过进一步抑制抗氧化酶以及用从这些小鼠自然形成的慢性伤口中分离出的形成生物膜的细菌感染伤口，加剧了氧化还原失衡。这些伤口不会重新上皮化，肉芽组织缺乏血管化和间质胶原纤维，它们含有具有生物膜形成能力的耐抗生素混合生物菌群，并且会开放数周。这些发现具有高度重要性，因为它们首次表明可以在动物模型中有效且一致地产生慢性伤口。这样一个模型的可用性将极大地推动该领域向前发展，因为它可用于制定恢复氧化还原平衡的策略，这可能会抑制生物膜形成并导致健康伤口组织的恢复。此外，该模型可有助于理解慢性伤口发展的其他基本机制，这可能会带来新的治疗方法。
