Biomimetic skin substitutes created from tropoelastin help to promote wound healing

摘要

Introduction: Tropoelastin, the precursor protein to elastin, is an important extracellular matrix protein found in many organs, including skin. Elastin is expressed in various tissues that require compliant mechanics to facilitate their funciton (e.g. skin, arteries, heart, bladder). However, the expression of this protein does not last a lifetime. Loss of elastin over time is associated with numerous disease states including aging of the organ or tissue. When skin becomes wounded in an adult, the repair mechanism no longer includes the production of tropoelastin as the gene is silent post-adolecence. By reverse-engineering native skin, an architectural template can be created to serve as a model for the development of biomimetic skin substitutes. The hypothesis in the current study was that a tropoelastin biomaterial impregnated with adipose-derived stem cells (ADSCs) would promote wound healing in full-thickness dermal wounds compared to control therapy. Materials and Methods: A human skin isoform of tropoelastin has been sequenced and expressed in E. coli to produce gram quantities of this protein for biomaterial fabrication using electrospinning procedures. Electrospinning methods were used to create a tropoeiastin biomaterial to serve as a biomimetic skin substitute for the delivery of ADSCs to a full thickness wounds. Human ADSCs found in the stromal vascular fraction (SVF) were isolated from liposuction fat provided by consenting patients. A severe combined immunodeficient (SCID) murine model was used for the creation of full thickness dermal wounds. SEM was performed on the biomimetic skin subsitutes with ADSCs for the assessment of ADSCs attachment, morphology and new extracellular matrix deposition. On postoperative day 6, animals were sacrificed, wounds photographed and wound tissue along with the wound margin collected and processed for histology and immunohistochemistry. Average percent wound closure and epithelial thickness of the newly formed tissue were quantified. Results and Discussion: In vitro studies demonstrated that the biomimetic skin substitutes facilitated ADSCs attachment and extracellular matrix deposition. This supports the concept that these biomimetic skin substitutes are biocompatible and will appropriately serve as a delivery vehicle for ADSCs. In the wound-healing study, ADSCs cultured onto the biomimetic skin substitutes demonstrated significantly enhanced wound closure and epithelial thickness compared to controls. In these studies, tropoelastin as a biomaterial offers unique material properties and characteristics that support its use in many tissues where elastin is found as a structural component. Conclusion: In the current study, recombinantly-derived human tropoelastin was used to create a novel biomaterial to serve as a biomimetic skin substitute and a delivery vehicle for ADSCs to a full thickness wound. Pre-clinical results in the current study demonstrate this combination therapy to be superior to control therapy for the closure of full thickness dermal wounds.