Abstract BACKGROUND Diabetic foot ulcers are a common diabetic complication leading to alarming figures of amputation, disability, and early mortality. The diabetic glucooxidative environment impairs the healing response, promoting the onset of a ‘wound chronicity phenotype’. In 50% of ulcers, these non-healing wounds act as an open door for developing infections, a process facilitated by diabetic patients’ dysimmunity. Infection can elicit biofilm formation that worsens wound prognosis. How this microorganism community is able to take advantage of underlying diabetic conditions and thrive both within the wound and the diabetic host is an expanding research field. OBJECTIVES 1) Offer an overview of the major cellular and molecular derangements of the diabetic healing process versus physiological cascades in a non-diabetic host. 2) Describe the main immunopathological aspects of diabetics’ immune response and explore how these contribute to wound infection susceptibility. 3) Conceptualize infection and biofilim in diabetic foot ulcers and analyze their dynamic interactions with wound bed cells and matrices, and their systemic effects at the organism level. 4) Offer an integrative conceptual framework of wound–dysimmunity–infection–organism damage. EVIDENCE AQUISITION We retrieved 683 articles indexed in Medline/PubMed, SciELO, Bioline International and Google Scholar. 280 articles were selected for discussion under four major subheadings: 1) normal healing processes, 2) impaired healing processes in the diabetic population, 3) diabetic dysimmunity and 4) diabetic foot infection and its interaction with the host. DEVELOPMENT The diabetic healing response is heterogeneous, torpid and asynchronous, leading to wound chronicity. The accumulation of senescent cells and a protracted inflammatory profile with a pro-catabolic balance hinder the proliferative response and delay re-epithelialization. Diabetes reduces the immune system’s abilities to orchestrate an appropriate antimicrobial response and offers ideal conditions for microbiota establishment and biofilm formation. Biofilm–microbial entrenchment hinders antimicrobial therapy effectiveness, amplifies the host's pre-existing immunodepression, arrests the wound’s proliferative phase, increases localized catabolism, prolongs pathogenic inflammation and perpetuates wound chronicity. In such circumstances the infected wound may act as a proinflammatory and pro-oxidant organ superimposed onto the host, which eventually intensifies peripheral insulin resistance and disrupts homeostasis. CONCLUSIONS The number of lower-limb amputations remains high worldwide despite continued research efforts on diabetic foot ulcers. Identifying and manipulating the molecular drivers underlying diabetic wound healing failure, and dysimmunity-driven susceptibility to infection will offer more effective therapeutic tools for the diabetic population.

Type 2 diabetes mellitus comprises a group of non-communicable metabolic diseases with an expanding pandemic magnitude. Diabetes predisposes to lower extremities ulceration and impairs the healing process leading to wounds chronification. Diabetes also dismantles innate immunity favoring wound infection. Amputation is therefore acknowledged as one of the disease's complications. Hyperglycemia appears as the proximal detonator of toxic effectors including pro-inflammation, spillover of reactive oxygen and nitrogen species. The systemic accumulation of advanced glycation end-products irreversibly impairs the entire physiology from cells-to-organs. Insulin axis deficiency weakens wounds' anabolism and predisposes to inflammation. These factors converge to hamper fibroblasts and endothelial cells proliferation, migration, homing, secretion and organization of a productive granulation tissue. Diabetic wound bed may turn chronically inflamed, pro-catabolic and a superimposed source of circulating pro-inflammatory cytokines, establishing a self-perpetuating loop. Diabetic toxicity breadth includes mitochondrial damages in fibroblasts and endothelial cells becoming prone to apoptosis thus hindering granulation. Endothelial progenitor cells recruitment and tubulogenesis are also impaired. Failure of wound re-epithelialization remains as a clinical challenge while it appears to be biologically multifactorial. Novel medical interventions as the local intra-ulcer infiltration of epidermal growth factor have emerged to hopefully reduce the current worldwide amputation rates.

La diabetes mellitus tipo 2 implica desórdenes metabólicos no transmisibles, cuya incidencia va en aumento, con una extensión casi pandémica. Predispone a padecer úlceras en las extremidades inferiores y a su cronicidad, al afectar el proceso de cicatrización. También interfiere la inmunidad innata, lo que favorece la infección de posibles lesiones, y puede conducir a la amputación. La hiperglucemia desencadena los efectores tóxicos que incluyen la inflamación y la producción en exceso de especies reactivas de oxígeno y nitrógeno. Los productos finales altamente glicosilados, que se acumulan sistemáticamente, desarticulan la estructura de células y órganos. La deficiencia en el eje insulínico debilita el anabolismo en las lesiones y predispone a la inflamación. Estos factores convergen y debilitan la proliferación, la migración, el direccionamiento, la secreción y la organización de los fibroblastos y células endoteliales, lo que interfiere en la formación de tejido de granulación útil. El lecho de las heridas puede convertirse en una fuente inflamatoria y procatabólica de citocinas, y constituir un ciclo de perpetuación. La toxicidad diabética provoca daños mitocondriales en los fibroblastos y las células endoteliales, que los hace susceptibles de apoptosis y dificulta la granulación del tejido. También afecta el reclutamiento de las células progenitoras endoteliales, e impide la tubulogénesis. La regeneración del tejido epitelial en las lesiones sigue siendo un desafío clínico que depende de múltiples factores biológicos. Nuevas intervenciones médicas, como la infiltración local intralesional del factor de crecimiento epidérmico recombinante, prometen la reducción de las tasas mundiales de amputación.