Factors that influence healing in chronic venous ulcers treated with cryopreserved human epidermal cultures

Advanced biofabrication strategies for skin regeneration and repair

Skin is the largest organ of human body, acting as a barrier with protective, immunologic and sensorial functions. Its permanent exposure to the external environment can result in different kinds of damage with loss of variable volumes of extracellular matrix. For the treatment of skin lesions, several strategies are currently available, such as the application of autografts, allografts, wound dressings and tissue-engineered substitutes. Although proven clinically effective, these strategies are still characterized by key limitations such as patient morbidity, inadequate vascularization, low adherence to the wound bed, the inability to reproduce skin appendages and high manufacturing costs. Advanced strategies based on both bottom-up and top-down approaches offer an effective, permanent and viable alternative to solve the abovementioned drawbacks by combining biomaterials, cells, growth factors and advanced biomanufacturing techniques. This review details recent advances in skin regeneration and repair strategies, and describes their major advantages and limitations. Future prospects for skin regeneration are also outlined.

Skin tissue engineering--in vivo and in vitro applications

Significant progress has been made over the years in the development of in vitro-engineered substitutes that mimic human skin, either to be used as grafts for the replacement of lost skin or for the establishment of human-based in vitro skin models. This review summarizes these advances in in vivo and in vitro applications of tissue-engineered skin. We further highlight novel efforts in the design of complex disease-in-a-dish models for studies ranging from disease etiology to drug development and screening.

Skin tissue engineering--in vivo and in vitro applications

Significant progress has been made over the years in the development of in vitro-engineered substitutes that mimic human skin, either to be used as grafts for the replacement of lost skin or for the establishment of human-based in vitro skin models. This review summarizes these advances in in vivo and in vitro applications of tissue-engineered skin. We further highlight novel efforts in the design of complex disease-in-a-dish models for studies ranging from disease etiology to drug development and screening.

Chronic wound healing by fetal cell therapy may be explained by differential gene profiling observed in fetal versus old skin cells

Engineering of fetal tissue has a high potential for the treatment of acute and chronic wounds of the skin in humans as these cells have high expansion capacity under simple culture conditions and one organ donation can produce Master Cell Banks which can fabricate over 900 million biological bandages (9 x 12cm). In a Phase 1 clinical safety study, cases are presented for the treatment of therapy resistant leg ulcers. All eight patients, representing 13 ulcers, tolerated multiple treatments with fetal biological bandages showing no negative secondary effects and repair processes similar to that seen in 3rd degree burns. Differential gene profiling using Affymetrix gene chips (analyzing 12,500 genes) were accomplished on these banked fetal dermal skin cells compared to banked dermal skin cells of an aged donor in order to point to potential indicators of wound healing. Families of genes involved in cell adhesion and extracellular matrix, cell cycle, cellular signaling, development and immune response show significant differences in regulation between banked fetal and those from banked old skin cells: with approximately 47.0% of genes over-expressed in fetal fibroblasts. It is perhaps these differences which contribute to efficient tissue repair seen in the clinic with fetal cell therapy.

Wound-Healing Perspectives

Wound-healing in the skin is a complex orchestration of cellular processes, which has been perfected throughout the eons of phylogeny. It has so many coordinated biologic processes invoked both simultaneously and in a regulated orderly fashion that it has been likened to a recapitulation of gestation. Part of the problem with studying wound healing is in analyzing the processes independently and then seeing how they fit together and influence each other. This article discusses selected and recent scientific observations that have given insight into the biology of human skin wound healing. The article then discusses selected clinical advances that are based less on evidence-based observation and more on what works in practice and promotes wound healing.

The accuracy of venous leg ulcer prognostic models in a wound care system

Venous leg ulcers are among the most common chronic wounds. Treatment is commonly with a limb compression bandage. Previous small, often single-center, studies have shown that it is possible to predict which wounds are likely to respond to compression therapy. We designed this cohort study using a dataset of over 20,000 individuals with a venous leg ulcer to investigate the accuracy of several prognostic models. Creating complex models using logistic regression, as well as simply counting prognostic factors, we show that initial measures of wound size and duration accurately predict, as measured by area under the receiver operator curve and Brier score, who will heal by the 24th week of care. For example, a wound that is less than 10 cm(2) and less than 12 months old at the first visit has a 29 percent chance of not healing by the 24th week of care, while a wound greater than 10 cm(2) and greater than 12 months old has a 78 percent chance of not healing. Ultimately, these models can be applied by a clinician to help determine whom to continue to treat with standard care and perhaps whom to treat with adjuvant therapies. They may also aid in the design of clinical trials.