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Frank Isik
Plastic and reconstructive surgery 07/2011; 128(1):112-3. · 2.74 Impact Factor
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ABSTRACT: Although bone marrow-derived mesenchymal stem cells have been shown to promote repair when applied to cutaneous wounds, the mechanism for this response remains to be determined. The aim of this study was to determine the effects of paracrine signaling from mesenchymal stem cells on dermal fibroblast responses to injury including proliferation, migration and expression of genes important in wound repair. Dermal fibroblasts were co-cultured with bone marrow-derived mesenchymal stem cells grown in inserts, which allowed for paracrine interactions without direct cell contact. In this co-culture model, bone marrow-derived mesenchymal stem cells regulate dermal fibroblast proliferation, migration and gene expression. When co-cultured with mesenchymal stem cells, dermal fibroblasts show increased proliferation and accelerated migration in a scratch assay. A chemotaxis assay also demonstrated that dermal fibroblasts migrate towards bone marrow-derived mesenchymal stem cells. A PCR array was used to analyze the effect of mesenchymal stem cells on dermal fibroblast gene expression. In response to mesenchymal stem cells, dermal fibroblasts up-regulate integrin alpha 7 expression and down-regulate expression of ICAM1, VCAM1 and MMP11. These observations suggest that mesenchymal stem cells may provide an important early signal for dermal fibroblast responses to cutaneous injury.
Experimental Cell Research 09/2009; 316(1):48-54. · 3.58 Impact Factor
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ABSTRACT: Cutaneous wound repair in adult mammals does not regenerate the original epithelial architecture and results in altered skin function. We propose that lack of regeneration may be due to the absence of appropriate molecular signals to promote regeneration. In this study, we investigated the regulation of Wnt signaling during cutaneous wound healing and the consequence of activating either the beta-catenin-dependent or beta-catenin-independent Wnt signaling on epidermal architecture during wound repair.
We determined that the expression of Wnt ligands that typically signal via the beta-catenin-independent pathway is up-regulated in the wound while the beta-catenin-dependent Wnt signaling is activated in the hair follicles adjacent to the wound edge. Ectopic activation of beta-catenin-dependent Wnt signaling with lithium chloride in the wound resulted in epithelial cysts and occasional rudimentary hair follicle structures within the epidermis. In contrast, forced expression of Wnt-5a in the deeper wound induced changes in the interfollicular epithelium mimicking regeneration, including formation of epithelia-lined cysts in the wound dermis, rudimentary hair follicles and sebaceous glands, without formation of tumors.
These findings suggest that adult interfollicular epithelium is capable of responding to Wnt morphogenic signals necessary for restoring epithelial tissue patterning in the skin during wound repair.
BMC Cell Biology 02/2006; 7:4. · 2.59 Impact Factor
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ABSTRACT: The bone marrow provides inflammatory cells and endothelial progenitor cells to healing cutaneous wounds. To further explore the bone marrow contribution to skin and healing wounds, we used a chimeric mouse model in which the bone marrow from enhanced green fluorescent protein (EGFP) transgenic mice is transplanted into normal C57BL mice. We found that normal skin is a target organ for bone marrow-derived cells from both the hematopoietic and the mesenchymal stem cell pool. We present evidence that the bone marrow contribution to normal skin and the healing cutaneous wound is substantially greater than the previously recognized CD45+ subpopulation, where 15%-20% of the spindle-shaped dermal fibroblasts were bone marrow-derived (EGFP+). Furthermore, the bone marrow-derived cells were able to contract a collagen matrix and transcribe both collagen types I and III, whereas the skin-resident cells transcribed only collagen type I. Whereas endothelial progenitor cells were found early during the wound repair process, bone marrow-derived endothelial cells were not seen after epithelialization was complete. Our data show that wound healing involves local cutaneous cells for reconstituting the epidermis but distant bone marrow-derived cells and the adjacent uninjured dermal mesenchymal cells for reconstituting the dermal fibroblast population.
Stem Cells 02/2004; 22(5):812-22. · 7.78 Impact Factor
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Frank Isik
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ABSTRACT: Life-threatening acute respiratory distress syndrome (ARDS) complicates the recovery of patients with burn and inhalation injury. The study by Enkhbaatar and co-workers in this issue of Clinical Science suggests that reducing the early and robust inflammatory cascade may provide patients with protection from developing cardiopulmonary compromise seen early after burn and inhalation injury.
Clinical Science 12/2003; 105(5):549-50. · 4.61 Impact Factor
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ABSTRACT: The Human Genome Project was launched in 1989 in an effort to sequence the entire span of human DNA. Although coding sequences are important in identifying mutations, the static order of DNA does not explain how a cell or organism may respond to normal and abnormal biological processes. By examining the mRNA content of a cell, researchers can determine which genes are being activated in response to a stimulus. Traditional methods in molecular biology generally work on a "one gene: one experiment" basis, which means that the throughput is very limited and the "whole picture" of gene function is hard to obtain. To study each of the 60,000 to 80,000 genes in the human genome under each biological circumstance is not practical. Recently, microarrays (also known as gene or DNA chips) have emerged; these allow for the simultaneous determination of expression for thousands of genes and analysis of genome-wide mRNA expression. The purpose of this article is twofold: first, to provide the clinical plastic surgeon with a working knowledge and understanding of the fields of genomics, microarrays, and bioinformatics and second, to present a case to illustrate how these technologies can be applied in the study of wound healing.
Plastic & Reconstructive Surgery 10/2002; 110(3):849-58. · 3.38 Impact Factor
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ABSTRACT: Injury induces a flux in the cellular composition of tissues as part of the wound healing response. There is no reliable and rapid method to quantify and characterize the cellular composition of the matrix-rich wound. Our aim was to develop a rapid method to quantify the cellular composition in wounds by tissue dispersion and flow cytometry. Age- and weight-matched mice were wounded on the dorsum using a 1.5 x 1.5 cm2 template, and the wounds were excised at predetermined time points. Tissues were dispersed into single-cell suspensions and labeled with antibodies to cell surfaces and intracellular antigens. Flow cytometry was performed to quantify the percentage of each cell population and cell death. We found that our tissue dispersion protocol resulted in low cell death (4%-6%) and very high yield (80-220 x 10(6) cells/g). Furthermore, cell surfaces and intracellular antigens were preserved to provide accurate identification of the different cell populations. With the appropriate modifications, this protocol is likely to be applicable for the viable retrieval and identification of cells from skin and other collagen-dense tissues.
BioTechniques 04/2002; 32(3):548-51. · 2.67 Impact Factor
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ABSTRACT: Vascular endothelial growth factor (VEGF) is a potent paracrine signal for initiating angiogenesis. Although VEGF can bind to several cell surface receptors, VEGF receptor type 2 (VEGFR2, a.k.a. KDR or flk-1) is the primary receptor responsible for VEGF-induced endothelial cell proliferation. To determine whether the VEGF-VEGFR2 signaling axis has an important role in wound healing angiogenesis, we used a retrovirus to deliver a signaling-defective truncated VEGFR2 (tm VEGFR2) to block VEGF-VEGFR2-induced endothelial cell proliferation in murine wounds. We show that the retroviral construct effectively blocked phosphorylation of VEGFR2 in vitro and we were able to express the truncated receptor in murine wounds. We achieved significant reduction of angiogenesis and granulation tissue formation in murine wounds, but this did not lead to delayed wound closure. In contrast, there was a corresponding increase in wound contraction, showing that functional VEGFR2 intracellular signaling is not critical for normal closure of excisional dermal wounds. Our results show a novel relationship between wound bed vascularity and wound contraction.
Wound Repair and Regeneration 10(4):222-9. · 2.91 Impact Factor
