Showing papers by "Geoffrey C. Gurtner published in 2017"

Injectable and Tunable Gelatin Hydrogels Enhance Stem Cell Retention and Improve Cutaneous Wound Healing

Abstract: Stem cells have shown substantial promise for various diseases in preclinical and clinical trials. However, low cell engraftment rates significantly limit the clinical translation of stem cell therapeutics. Numerous injectable hydrogels have been developed to enhance cell retention. Yet, the design of an ideal material with tunable properties that can mimic different tissue niches and regulate stem cell behaviors remains an unfulfilled promise. Here, an injectable poly(ethylene glycol) (PEG)–gelatin hydrogel is designed with highly tunable properties, from a multifunctional PEG-based hyperbranched polymer and a commercially available thiolated gelatin. Spontaneous gelation occurs within about 2 min under the physiological condition. Murine adipose-derived stem cells (ASCs) can be easily encapsulated into the hydrogel, which supports ASC growth and maintains their stemness. The hydrogel mechanical properties, biodegradability, and cellular responses can be finely controlled by changing hydrogel formulation and cell seeding densities. An animal study shows that the in situ formed hydrogel significantly improves cell retention, enhances angiogenesis, and accelerates wound closure using a murine wound healing model. These data suggest that injectable PEG–gelatin hydrogel can be used for regulating stem cell behaviors in 3D culture, delivering cells for wound healing and other tissue regeneration applications.

Mechanical Forces in Cutaneous Wound Healing: Emerging Therapies to Minimize Scar Formation

Abstract: Significance: Excessive scarring is major clinical and financial burden in the United States. Improved therapies are necessary to reduce scarring, especially in patients affected by hypertrophic and keloid scars. Recent Advances: Advances in our understanding of mechanical forces in the wound environment enable us to target mechanical forces to minimize scar formation. Fetal wounds experience much lower resting stress when compared with adult wounds, and they heal without scars. Therapies that modulate mechanical forces in the wound environment are able to reduce scar size. Critical Issues: Increased mechanical stresses in the wound environment induce hypertrophic scarring via activation of mechanotransduction pathways. Mechanical stimulation modulates integrin, Wingless-type, protein kinase B, and focal adhesion kinase, resulting in cell proliferation and, ultimately, fibrosis. Therefore, the development of therapies that reduce mechanical forces in the wound environment would decrease the risk of developing excessive scars. Future Directions: The development of novel mechanotherapies is necessary to minimize scar formation and advance adult wound healing toward the scarless ideal. Mechanotransduction pathways are potential targets to reduce excessive scar formation, and thus, continued studies on therapies that utilize mechanical offloading and mechanomodulation are needed.

Isotretinoin and Timing of Procedural Interventions: A Systematic Review With Consensus Recommendations

Abstract: Importance The notion that systemic isotretinoin taken within 6 to 12 months of cutaneous surgery contributes to abnormal scarring or delayed wound healing is widely taught and practiced; however, it is based on 3 small case series from the mid-1980s. Objective To evaluate the body of literature to provide evidence-based recommendations regarding the safety of procedural interventions performed either concurrently with, or immediately following the cessation of systemic isotretinoin therapy. Evidence Review A panel of national experts in pediatric dermatology, procedural/cosmetic dermatology, plastic surgery, scars, wound healing, acne, and isotretinoin was convened. A systematic PubMed review of English-language articles published from 1982 to 2017 was performed using the following search terms: isotretinoin, 13-cis-retinoic acid, Accutane, retinoids, acitretin, surgery, surgical, laser, ablative laser, nonablative laser, laser hair removal, chemical peel, dermabrasion, wound healing, safety, scarring, hypertrophic scar, and keloid. Evidence was graded, and expert consensus was obtained. Findings Thirty-two relevant publications reported 1485 procedures. There was insufficient evidence to support delaying manual dermabrasion, superficial chemical peels, cutaneous surgery, laser hair removal, and fractional ablative and nonablative laser procedures for patients currently receiving or having recently completed isotretinoin therapy. Based on the available literature, mechanical dermabrasion and fully ablative laser are not recommended in the setting of systemic isotretinoin treatment. Conclusions and Relevance Physicians and patients may have an evidence-based discussion regarding the known risk of cutaneous surgical procedures in the setting of systemic isotretinoin therapy. For some patients and some conditions, an informed decision may lead to earlier and potentially more effective interventions.

Pharmacological rescue of diabetic skeletal stem cell niches

Abstract: Diabetes mellitus (DM) is a metabolic disease frequently associated with impaired bone healing. Despite its increasing prevalence worldwide, the molecular etiology of DM-linked skeletal complications remains poorly defined. Using advanced stem cell characterization techniques, we analyzed intrinsic and extrinsic determinants of mouse skeletal stem cell (mSSC) function to identify specific mSSC niche-related abnormalities that could impair skeletal repair in diabetic (Db) mice. We discovered that high serum concentrations of tumor necrosis factor-α directly repressed the expression of Indian hedgehog (Ihh) in mSSCs and in their downstream skeletogenic progenitors in Db mice. When hedgehog signaling was inhibited during fracture repair, injury-induced mSSC expansion was suppressed, resulting in impaired healing. We reversed this deficiency by precise delivery of purified Ihh to the fracture site via a specially formulated, slow-release hydrogel. In the presence of exogenous Ihh, the injury-induced expansion and osteogenic potential of mSSCs were restored, culminating in the rescue of Db bone healing. Our results present a feasible strategy for precise treatment of molecular aberrations in stem and progenitor cell populations to correct skeletal manifestations of systemic disease.

Delivery of monocyte lineage cells in a biomimetic scaffold enhances tissue repair

Abstract: The monocyte lineage is essential to normal wound healing. Macrophage inhibition or knockout in mice results in impaired wound healing through reduced neovascularization, granulation tissue formation, and reepithelialization. Numerous studies have either depleted macrophages or reduced their activity in the context of wound healing. Here, we demonstrate that by increasing the number of macrophages or monocytes in the wound site above physiologic levels via pullulan-collagen composite dermal hydrogel scaffold delivery, the rate of wound healing can be significantly accelerated in both wild-type and diabetic mice, with no adverse effect on the quality of repair. Macrophages transplanted onto wounds differentiate into M1 and M2 phenotypes of different proportions at various time points, ultimately increasing angiogenesis. Given that monocytes can be readily isolated from peripheral blood without in vitro manipulation, these findings hold promise for translational medicine aimed at accelerating wound healing across a broad spectrum of diseases.

Comparison of the Hydroxylase Inhibitor Dimethyloxalylglycine and the Iron Chelator Deferoxamine in Diabetic and Aged Wound Healing.

Abstract: Background:A hallmark of diabetes mellitus is the breakdown of almost every reparative process in the human body, leading to critical impairments of wound healing. Stabilization and activity of the transcription factor hypoxia-inducible factor (HIF)-1α is impaired in diabetes, leading to deficits in

Isolation of CD248-expressing stromal vascular fraction for targeted improvement of wound healing.

Abstract: Wound healing remains a global issue of disability, cost, and health. Addition of cells from the stromal vascular fraction (SVF) of adipose tissue has been shown to increase the rate of full thickness wound closure. This study aimed to investigate the angiogenic mechanisms of CD248+ SVF cells in the context of full thickness excisional wounds. Single cell transcriptional analysis was used to identify and cluster angiogenic gene-expressing cells, which was then correlated with surface marker expression. SVF cells isolated from human lipoaspirate were FACS sorted based on the presence of CD248. Cells were analyzed for angiogenic gene expression and ability to promote microvascular tubule formation in vitro. Following this, 6mm full thickness dermal wounds were created on the dorsa of immunocompromised mice and then treated with CD248+, CD248-, or unsorted SVF cells delivered in a pullalan-collagen hydrogel or the hydrogel alone. Wounds were measured every other day photometrically until closure. Wounds were also evaluated histologically at 7 and 14 days post-wounding and when fully healed to assess for reepithelialization and development of neovasculature. Wounds treated with CD248+ cells healed significantly faster than other treatment groups, and at 7 days, had quantitatively more reepithelialization. Concurrently, immunohistochemistry of CD31 revealed a much higher presence of vascularity in the CD248+ SVF cells treated group at the time of healing and at 14 days post-op, consistent with a pro-angiogenic effect of CD248+ cells in vivo. Therefore, using CD248+ pro-angiogenic cells obtained from SVF presents a viable strategy in wound healing by promoting increased vessel growth in the wound.

The Role of Focal Adhesion Kinase in Keratinocyte Fibrogenic Gene Expression.

Abstract: Abnormal skin scarring causes functional impairment, psychological stress, and high socioeconomic cost. Evidence shows that altered mechanotransduction pathways have been linked to both inflammation and fibrosis, and that focal adhesion kinase (FAK) is a key mediator of these processes. We investigated the importance of keratinocyte FAK at the single cell level in key fibrogenic pathways critical for scar formation. Keratinocytes were isolated from wildtype and keratinocyte-specific FAK-deleted mice, cultured, and sorted into single cells. Keratinocytes were evaluated using a microfluidic-based platform for high-resolution transcriptional analysis. Partitive clustering, gene enrichment analysis, and network modeling were applied to characterize the significance of FAK on regulating keratinocyte subpopulations and fibrogenic pathways important for scar formation. Considerable transcriptional heterogeneity was observed within the keratinocyte populations. FAK-deleted keratinocytes demonstrated increased expression of genes integral to mechanotransduction and extracellular matrix production, including Igtbl, Mmpla, and Col4a1. Transcriptional activities upon FAK deletion were not identical across all single keratinocytes, resulting in higher frequency of a minor subpopulation characterized by a matrix-remodeling profile compared to wildtype keratinocyte population. The importance of keratinocyte FAK signaling gene expression was revealed. A minor subpopulation of keratinocytes characterized by a matrix-modulating profile may be a keratinocyte subset important for mechanotransduction and scar formation.

Optimizing Outcomes of Postmastectomy Breast Reconstruction With Acellular Dermal Matrix: A Review of Recent Clinical Data.

Abstract: Background: This article reports on the current use of acellular dermal matrix in breast reconstruction. Methods: A literature review of articles on acellular dermal matrix in breast reconstruction from January 1, 2010, through December 20, 2016, was performed and analyzed for trends in acellular dermal matrix use and differences between commonly used acellular dermal matrixes. Findings: Clinical findings varied but include improved cosmesis and more 1-stage reconstructions using acellular dermal matrix. Superiority of sterile versus aseptic acellular dermal matrixes was noted, and the increased incidence of red breast syndrome with AlloDerm was significant. The cost-effectiveness of acellular dermal matrix use despite increased upfront costs was also highlighted. Finally, the article emphasizes the importance of well-vascularized mastectomy flaps and the use of indocyanine green angiography as an adjunct in immediate reconstruction with acellular dermal matrix.

Wound healing outcomes: Using big data and a modified intent-to-treat method as a metric for reporting healing rates.

Abstract: Chronic wounds are increasing in prevalence and are a costly problem for the US healthcare system and throughout the world. Typically outcomes studies in the field of wound care have been limited to small clinical trials, comparative effectiveness cohorts and attempts to extrapolate results from claims databases. As a result, outcomes in real world clinical settings may differ from these published studies. This study presents a modified intent-to-treat framework for measuring wound outcomes and measures the consistency of population based outcomes across two distinct settings. In this retrospective observational analysis, we describe the largest to date, cohort of patient wound outcomes derived from 626 hospital based clinics and one academic tertiary care clinic. We present the results of a modified intent-to-treat analysis of wound outcomes as well as demographic and descriptive data. After applying the exclusion criteria, the final analytic sample includes the outcomes from 667,291 wounds in the national sample and 1,788 wounds in the academic sample. We found a consistent modified intent to treat healing rate of 74.6% from the 626 clinics and 77.6% in the academic center. We recommend that a standard modified intent to treat healing rate be used to report wound outcomes to allow for consistency and comparability in measurement across providers, payers and healthcare systems.

Is early inflammation good or bad? Linking early immune changes to hypertrophic scarring.

Abstract: The mechanisms regulating hypertrophic scar (HTS) formation are multifactorial and complex. Early inflammation following dermal injury is believed to be a critical and essential event in the progression of normal wound healing and repair. It is generally accepted that acute inflammatory responses are necessary for normal wound repair, while chronic or excessive inflammation may lead to pathological scarring and fibrosis. A new study published in Experimental Dermatology revisited this topic and demonstrated that reduced and/or delayed early immunological responses were actually associated with HTS formation (1). This article is protected by copyright. All rights reserved.

Black, White, and Gray: Macrophages in Skin Repair and Disease.

Abstract: Macrophages alter their responses during the temporal stages of wound healing. During the inflammatory phase, they perform phagocytosis. During neovascularization, they fuse sprouting endothelial cells. In the proliferation phase, they deposit extracellular matrix, and during wound resolution, macrophages phagocytize excessive cellular components. This review addresses how changing macrophage phenotypes affects skin repair and disease. Macrophages can determine the outcome of repair and can shift the normal wound healing response into fibrosis or chronic wounds. Emerging single-cell technologies for the first time provide us with tools to uncover macrophage origin, heterogeneity, and function. Macrophages may exist as one population where all cells alter their phenotype in response to signals from the microenvironment. Alternatively, macrophages may exist as distinct subsets that can control wound outcomes. A clarified understanding will strengthen our knowledge of skin biology and aid in the development of wound healing therapies.

Abstract 100: Human Mesenchymal Stromal Cells Engineered to Overexpress PDGF-B Using CRISPR/Cas9/rAAV6-based Tools Improve Wound Healing.

Abstract: PURPOSE: Mesenchymal Stromal Cells (MSCs) are a promising source for cell therapy due to their proregenerative and immunomodulatory effects. These properties can be enhanced by engineering MSCs to overexpress and secrete growth factors favorable to wound healing processes. Here, we aimed to develop a platform for targeted gene insertion in human bone marrow (hBM)-MSCs that utilizes CRISPR/Cas9 nuclease and recombinant adeno-associated virus serotype 6 (rAAV6) to deliver a designed homologous recombination-based repair template. Using this method, we engineered hBM-MSCs to overexpress and secrete soluble platelet derived growth factor B (PDGF-B) and examined the ability of this cell line to promote wound healing.

Engineering Niches for Skin and Wound Healing

Abstract: Optimization of wound healing has been a major goal of medical care throughout history. A myriad of devices, dressings, and therapies have been developed to control the local wound environment, facilitate timely healing, and modulate scar. Despite this, chronic wounds remain a major health burden, scarless wound healing is an aspirational goal, and hypertrophic and keloid scar formation are unpredictable and difficult to treat. Stem cells play a vital role in both wound healing and normal skin homeostasis, prompting their application to wounds and local tissues in efforts to optimize wound healing. However, significant barriers to their use remain, in the form of variable results, regulatory hurdles, expense, poor user-friendliness, and limited cell survival. Stem cell niche engineering is an emerging modality that seeks to facilitate stem cell recruitment, aid the effectiveness of exogenous stem cells, and ultimately result in the reestablishment of stable stem cell populations in support of wound healing and normal skin homeostasis. We examine the stem cell niches of the skin during normal homeostasis and wound healing, explore niche engineering approaches, and identify how these approaches may help address important unmet clinical needs and thereby optimize wound care.

Disease models: Method in the madness of fibrosis

Abstract: Blocking the growth of new blood vessels has been shown to alter fibrosis in livers in a disease stage-specific manner. In vitro models of fibrosis were developed to understand this process, highlighting the role of environmental mechanics.

Excess Dermal Tissue Remodeling In Vivo: Does It Settle?

Abstract: Background:Surgical manipulation of skin may result in undesired puckering of excess tissue, which is generally assumed to settle over time. In this article, the authors address the novel question of how this excess tissue remodels.Methods:Purse-string sutures (6-0 nylon) were placed at the midline

Threads of hyaluronic acid, methods of making thereof and uses thereof

Abstract: The present invention provides threads of hyaluronic acid, and/or derivatives thereof, methods of making thereof and uses thereof, for example, in aesthetic applications ( e.g. , dermal fillers), surgery (sutures), drug delivery, etc.