Acne Scars

Appl Microbiol Biotechnol. 2009 Jul 25; McCleary WRThe ability to control the expression of chromosomal genes is important for many applications, including metabolic engineering and the functional analysis of cellular processes. This mini-review presents recent work on the application of techniques that allow researchers to replace a chromosomal promoter with one designed for a specific level of activity, thereby exerting precise transcriptional control while retaining the natural genetic context of a gene or operon. This technique, termed promoter swapping, involves the creation of a PCR product that encodes a removable antibiotic resistance cassette and an engineered promoter. Short homology sequences on the ends of the PCR fragment target it for homologous recombination with the chromosome catalyzed by phage-derived recombination proteins. After the PCR product is introduced by electroporation into an appropriate acceptor strain, antibiotic resistance selects the desired recombination products. The antibiotic resistance cassette is then removed from the strain by site-specific recombination leaving the engineered promoter precisely positioned upstream of a target gene but downstream of a short scar consisting of a single site-specific recombination site.

Matrix metalloproteinases (MMPs) are a large family of proteolytic enzymes involved in inflammation, wound healing and other pathological processes after neurological disorders. MMP-2 promotes functional recovery after spinal cord injury (SCI) by regulating the formation of a glial scar. In the present study, we aimed to investigate the expression and/or activity of several MMPs, after SCI and human umbilical cord blood mesenchymal stem cells (hUCB) treatment in rats with a special emphasis on MMP-2.

Treatment with hUCB after SCI altered the expression of several MMPs in rats. MMP-2 is upregulated after hUCB treatment in spinal cord injured rats and in spinal neurons injured either with staurosporine or hydrogen peroxide. Further, hUCB induced upregulation of MMP-2 reduced formation of the glial scar at the site of injury along with reduced immunoreactivity to chondroitin sulfate proteoglycans. Blockade of MMP-2 activity in hUCB cocultured injured spinal neurons reduced the protection offered by hUCB indicated the involvement of MMP-2 in the neuroprotection offered by hUCB.

Based on these results, we conclude that hUCB treatment after SCI upregulate MMP-2 levels and reduce the formation of the glial scar thereby creating an environment suitable for endogenous repair mechanisms.


"Human umbilical cord blood stem cells upregulate matrix metalloproteinase-2 in rats after spinal cord injury."
Neurobiol Dis. 2009 Jul 22; Veeravalli KK, Dasari VR, Tsung AJ, Dinh DH, Gujrati M, Fassett D, Rao JS

J Mol Cell Cardiol. 2009 Jul 22; Dobaczewski M, Gonzalez-Quesada C, Frangogiannis NGThe dynamic alterations in the cardiac extracellular matrix following myocardial infarction not only determine the mechanical properties of the infarcted heart, but also directly modulate the inflammatory and reparative response. During the inflammatory phase of healing, rapid activation of matrix metalloproteinases (MMP) causes degradation of the cardiac extracellular matrix. Matrix fragments exert potent pro-inflammatory actions, while MMPs process cytokines and chemokines altering their biological activity. In addition, vascular hyperpermeability results in extravasation of fibronectin and fibrinogen leading to formation of a plasma-derived provisional matrix that serves as a scaffold for leukocyte infiltration. Clearance of the infarct from dead cells and matrix debris is essential for resolution of inflammation and marks the transition to the proliferative phase. The fibrin-based provisional matrix is lysed and cellular fibronectin is secreted. ED-A fibronectin, mechanical tension and Transforming Growth Factor (TGF)-beta are essential for modulation of fibroblasts into myofibroblasts, the main collagen-secreting cells in the wound. The matricellular proteins thrombospondin-1 and -2, osteopontin, tenascin-C, periostin, and secreted protein acidic and rich in cysteine (SPARC) are induced in the infarct regulating cellular interactions and promoting matrix organization. As the infarct matures, matrix cross-linking results in formation of a dense collagen-based scar. At this stage, shielding of fibroblasts from external mechanical tension by the mature matrix network may promote deactivation and cellular quiescence. The components of the extracellular matrix do not passively follow the pathologic alterations of the infarcted heart but critically modulate inflammatory and reparative pathways by transducing signals that affect cell survival, phenotype and gene expression.

Am J Dermatopathol. 2009 Jul 23; Wiedemeyer K, Kutzner H, Abraham JL, Thakral C, Carlson JA, Tran TA, Hausser I, Hartschuh WGadolinium (Gd) is associated with nephrogenic systemic fibrosis (NSF), a severe disorder mimicking scleroderma with involvement of the skin, lungs, heart, liver, and muscles. There is strong evidence that specific Gd-containing contrast agents (GCCAs) used in magnetic resonance imaging can cause NSF when administered to patients with chronic kidney disease. We present the 8-year history of cutaneous NSF with osseous metaplasia that occurred in a 56-year-old man with dialysis-dependent renal failure who was exposed to GCCA [gadopentate dimeglumine (Magnevist; Bayer Schering Pharma AG, Pittsburgh, PA)]. Three months after exposure to GCCA, he developed pruritic, pigmented patches that slowly coalesced and darkened over 8 years. Although not recognized at onset, skin biopsy showed typical histology of NSF affecting the entire dermis: CD34/procollagen I spindle cells associated with fibrosis. Biopsy performed 6 years later showed superficial scar-like fibrosis that was CD34/procollagen I and had numerous elastocollagenous balls (refractile elastic fibers surrounded by coarse collagen). Biopsy 7 years later showed the superimposition of osseous metaplasia on elastocollagenous balls. Both of these later biopsies had typical NSF histology affecting the deep dermis and subcutis. Over time, there was progressive diminishment of CD34 and procollagen I+ cells and an increase in FXIIIa+ and CD68 cells. Scanning electron microscopy and energy-dispersive x-ray spectroscopy showed Gd deposits in all areas of typical NSF histology but not in the regions of scar-like fibrosis, elastocollagenous balls, or osseous metaplasia. We suspect that the later changes may represent a late, involuting stage of NSF.