Andrew Zimmermann

Scarless fetal skin wound healing update.

Scar formation, a physiologic process in adult wound healing, can have devastating effects for patients; a multitude of pathologic outcomes, affecting all organ systems, stems from an amplification of this process. In contrast to adult wound repair, the early-gestation fetal skin wound heals without scar formation, a phenomenon that appears to be intrinsic to fetal skin. An intensive research effort has focused on unraveling the mechanisms that underlie scarless fetal wound healing in an attempt to improve the quality of healing in both children and adults. Unique properties of fetal cells, extracellular matrix, cytokine profile, and gene expression contribute to this scarless repair. Despite the great increase in knowledge gained over the past decades, the precise mechanisms regulating scarless fetal healing remain unknown. Herein, we describe the current proposed mechanisms underlying fetal scarless wound healing in an effort to recapitulate the fetal phenotype in the postnatal environment.

Isolation of Human Adipose-Derived Stromal Cells Using Laser-Assisted Liposuction and Their Therapeutic Potential in Regenerative Medicine

Harvesting adipose‐derived stromal cells (ASCs) for tissue engineering is frequently done through liposuction. However, several different techniques exist. Although third‐generation ultrasound‐assisted liposuction has been shown to not have a negative effect on ASCs, the impact of laser‐assisted liposuction on the quality and differentiation potential of ASCs has not been studied. Therefore, ASCs were harvested from laser‐assisted lipoaspirate and suction‐assisted lipoaspirate. Next, in vitro parameters of cell yield, cell viability and proliferation, surface marker phenotype, osteogenic differentiation, and adipogenic differentiation were performed. Finally, in vivo bone formation was assessed using a critical‐sized cranial defect in athymic nude mice. Although ASCs isolated from suction‐assisted lipoaspirate and laser‐assisted lipoaspirate both successfully underwent osteogenic and adipogenic differentiation, the cell yield, viability, proliferation, and frequency of ASCs (CD34+CD31−CD45−) in the stromal vascular fraction were all significantly less with laser‐assisted liposuction in vitro (p < .05). In vivo, quantification of osseous healing by micro‐computed tomography revealed significantly more healing with ASCs isolated from suction‐assisted lipoaspirate relative to laser‐assisted lipoaspirate at the 4‐, 6‐, and 8‐week time points (p < .05). Therefore, as laser‐assisted liposuction appears to negatively impact the biology of ASCs, cell harvest using suction‐assisted liposuction is preferable for tissue‐engineering purposes.

Enhancing In Vivo Survival of Adipose-Derived Stromal Cells Through Bcl-2 Overexpression Using a Minicircle Vector

Tissue regeneration using progenitor cell‐based therapy has the potential to aid in the healing of a diverse range of pathologies, ranging from short‐gut syndrome to spinal cord lesions. However, there are numerous hurdles to be overcome prior to the widespread application of these cells in the clinical setting. One of the primary barriers to effective stem cell therapy is the hostile environment that progenitor cells encounter in the clinical injury wound setting. In order to promote cellular survival, stem cell differentiation, and participation in tissue regeneration, relevant cells and delivery scaffolds must be paired with strategies to prevent cell death to ensure that these cells can survive to form de novo tissue. The Bcl‐2 protein is a prosurvival member of a family of proteins that regulate the mitochondrial pathway of apoptosis. Using several strategies to overexpress the Bcl‐2 protein, we demonstrated a decrease in the mediators of apoptosis in vitro and in vivo. This was shown through the use of two different clinical tissue repair models. Cells overexpressing Bcl‐2 not only survived within the wound environment at a statistically significantly higher rate than control cells, but also increased tissue regeneration. Finally, we used a nonintegrating minicircle technology to achieve this in a potentially clinically applicable strategy for stem cell therapy.

Evidence That Mast Cells Are Not Required for Healing of Splinted Cutaneous Excisional Wounds in Mice

Wound healing is a complex biological process involving the interaction of many cell types to replace lost or damaged tissue. Although the biology of wound healing has been extensively investigated, few studies have focused on the role of mast cells. In this study, we investigated the possible role of mast cells in wound healing by analyzing aspects of cutaneous excisional wound healing in three types of genetically mast cell-deficient mice. We found that C57BL/6-KitW-sh/W-sh, WBB6F1-KitW/W-v, and Cpa3-Cre; Mcl-1fl/fl mice re-epithelialized splinted excisional skin wounds at rates very similar to those in the corresponding wild type or control mice. Furthermore, at the time of closure, scars were similar in the genetically mast cell-deficient mice and the corresponding wild type or control mice in both quantity of collagen deposition and maturity of collagen fibers, as evaluated by Masson’s Trichrome and Picro-Sirius red staining. These data indicate that mast cells do not play a significant non-redundant role in these features of the healing of splinted full thickness excisional cutaneous wounds in mice.

Antimycotic Ciclopirox Olamine in the Diabetic Environment Promotes Angiogenesis and Enhances Wound Healing

Diabetic wounds remain a major medical challenge with often disappointing outcomes despite the best available care. An impaired response to tissue hypoxia and insufficient angiogenesis are major factors responsible for poor healing in diabetic wounds. Here we show that the antimycotic drug ciclopirox olamine (CPX) can induce therapeutic angiogenesis in diabetic wounds. Treatment with CPX in vitro led to upregulation of multiple angiogenic genes and increased availability of HIF-1α. Using an excisional wound splinting model in diabetic mice, we showed that serial topical treatment with CPX enhanced wound healing compared to vehicle control treatment, with significantly accelerated wound closure, increased angiogenesis, and increased dermal cellularity. These findings offer a promising new topical pharmacologic therapy for the treatment of diabetic wounds.

Epidermal or dermal specific knockout of PHD-2 enhances wound healing and minimizes ischemic injury

Introduction Hypoxia-inducible factor (HIF)-1α, part of the heterodimeric transcription factor that mediates the cellular response to hypoxia, is critical for the expression of multiple angiogenic growth factors, cell motility, and the recruitment of endothelial progenitor cells. Inhibition of the oxygen-dependent negative regulator of HIF-1α, prolyl hydroxylase domain-2 (PHD-2), leads to increased HIF-1α and mimics various cellular and physiological responses to hypoxia. The roles of PHD-2 in the epidermis and dermis have not been clearly defined in wound healing. Methods Epidermal and dermal specific PHD-2 knockout (KO) mice were developed in a C57BL/6J (wild type) background by crossing homozygous floxed PHD-2 mice with heterozygous K14-Cre mice and heterozygous Col1A2-Cre-ER mice to get homozygous floxed PHD-2/heterozygous K14-Cre and homozygous floxed PHD-2/heterozygous floxed Col1A2-Cre-ER mice, respectively. Ten to twelve-week-old PHD-2 KO and wild type (WT) mice were subjected to wounding and ischemic pedicle flap model. The amount of healing was grossly quantified with ImageJ software. Western blot and qRT-PCR was run on protein and RNA from primary cells cultured in vitro. Results qRT-PCR demonstrated a significant decrease of PHD-2 in keratinocytes and fibroblasts derived from tissue specific KO mice relative to control mice (*p<0.05). Western blot analysis showed a significant increase in HIF-1α and VEGF protein levels in PHD-2 KO mice relative to control mice (*p<0.05). PHD-2 KO mice showed significantly accelerated wound closure relative to WT (*p<0.05). When ischemia was analyzed at day nine post-surgery in a flap model, the PHD-2 tissue specific knockout mice showed significantly more viable flaps than WT (*p<0.05). Conclusions PHD-2 plays a significant role in the rates of wound healing and response to ischemic insult in mice. Further exploration shows PHD-2 KO increases cellular levels of HIF-1α and this increase leads to the transcription of downstream angiogenic factors such as VEGF.

Repair of a Critical-sized Calvarial Defect Model Using Adipose-derived Stromal Cells Harvested from Lipoaspirate

Craniofacial skeletal repair and regeneration offers the promise of de novo tissue formation through a cell-based approach utilizing stem cells. Adipose-derived stromal cells (ASCs) have proven to be an abundant source of multipotent stem cells capable of undergoing osteogenic, chondrogenic, adipogenic, and myogenic differentiation. Many studies have explored the osteogenic potential of these cells in vivo with the use of various scaffolding biomaterials for cellular delivery. It has been demonstrated that by utilizing an osteoconductive, hydroxyapatite-coated poly(lactic-co-glycolic acid) (HA-PLGA) scaffold seeded with ASCs, a critical-sized calvarial defect, a defect that is defined by its inability to undergo spontaneous healing over the lifetime of the animal, can be effectively show robust osseous regeneration. This in vivo model demonstrates the basis of translational approaches aimed to regenerate the bone tissue - the cellular component and biological matrix. This method serves as a model for the ultimate clinical application of a progenitor cell towards the repair of a specific tissue defect.

Differences in Foetal, Adult Skin and Mucosal Repair

Abstract Scar formation, a physiologic process in adult wound healing, can have devastating effects for patients; a multitude of pathologic outcomes, affecting all organ systems, stems from an amplification of this process. In contrast to adult wound repair, the early gestation fetal skin wound heals without scar formation, a phenomenon that appears to be intrinsic to fetal skin. Interestingly, there is strong evidence to suggest healing of oral mucosal wounds parallels that of fetal skin wound repair, and that the relative scarless repair of oral mucosa is also derived primarily from the intrinsic differences in oral mucosal tissue, rather than from the intraoral environment. An intensive research effort has focused on unraveling the mechanisms that underlie scarless fetal wound healing in an attempt to improve the quality of healing in both children and adults. Unique properties of fetal skin and oral mucosal cells, extracellular matrix, cytokine profile, and gene expression contribute to this scarless repair. Despite the great increase in knowledge gained over the past decades, the precise mechanisms regulating scarless wound healing remain unknown. Herein, we describe the current models and proposed mechanisms underlying scarless wound healing in an effort to better understand this privileged phenotype.

Abstract 151: short hairpin RNA interference therapy for diabetic murine wound closure and hindlimb ischemia.

Suday, M arch 9, 2014 hypoxia/2h reoxygenation at 32°C (0.42 ± 0.04 OD/mg wet wt.; n=6), at 30°C (0.44 ± 0.42 OD/mg wet wt.; n=6) and at 10°C (0.39 ± 0.05 OD/mg wet wt.; n=6). There was no significant difference in MTT content among these three hypothermial treatment groups. The skeletal muscle contents of LDH and ATP are being analyzed at the present time, and will be ready for presentation at the meeting.

Abstract 135: improved engraftment of autologous skin grafts in diabetic mice with adipose-derived stem cells.

PurPose: Non-healing diabetic wounds are a major health concern in the US, affecting over 1 in 10 diabetic patients. With the increasing prevalence of diabetes, a significant rise in the number of diabetic patients suffering from non-healing wounds is also expected to occur. However, therapies currently available to diabetics are often insufficient to ensure satisfactory wound healing. Thus there is an urgent need for novel therapeutic strategies to address non-healing diabetic wounds. Autologous full thickness skin grafts are one of the most common procedures used for wound closure in both diabetic and nondiabetic patients. However, in diabetic patients skin graft rejection is common because of poor circulation around the graft and surrounding wound areas. One strategy that has been identified as particularly promising has been a cell-based therapeutic approach utilizing adipose-derived stem cells (ASCs). ASCs are an abundant and easily accessible population of adult pluripotent stem cells present in stromal tissue. They can be readily isolated from patients through minimally invasive techniques, potentially allowing for autologous transplantation. ASCs have been shown to promote wound healing in hypoxic environments by releasing various cytokines and growth factors at the wound to promote neovascularization. However, whether ASCs can increase the success of autologous full thickness skin grafts in a diabetic setting remains unclear. In this study we examine the ability of ASCs to mediate acceptance of autologous skin grafts in both wild-type and diabetic mice.