Reduced Fibroblast Interaction with Intact Collagen as a Mechanism for Depressed Collagen Synthesis in Photodamaged Skin

Fibroblast mechanics in 3D collagen matrices

Connective tissues provide mechanical support and frameworks for the other tissues of the body. Type 1 collagen is the major protein component of ordinary connective tissue, and fibroblasts are the cell type primarily responsible for its biosynthesis and remodeling. Research on fibroblasts interacting with collagen matrices explores all four quadrants of cell mechanics: pro-migratory vs. pro-contractile growth factor environments on one axis; high tension vs. low tension cell-matrix interactions on the other. The dendritic fibroblast - probably equivalent to the resting tissue fibroblast - can be observed only in the low tension quadrant and generally has not been appreciated from research on cells incubated with planar culture surfaces. Fibroblasts in the low tension quadrant require microtubules for formation of dendritic extensions, whereas fibroblasts in the high tension quadrant require microtubules for polarization but not for spreading. Ruffling of dendritic extensions rather than their overall protrusion or retraction provides the mechanism for remodeling of floating collagen matrices, and floating matrix remodeling likely reflects a model of tissue mechanical homeostasis.

Microtubule function in fibroblast spreading is modulated according to the tension state of cell-matrix interactions

Mechanical and physical features of the extracellular environment dramatically impact cell shape. Fibroblasts interacting with 3D relaxed collagen matrices appear much different from cells on 2D collagen-coated surfaces and form dendritic cell extensions that contain microtubule cores and actin-rich tips. We found that interfering with cellular microtubules caused cells in relaxed matrices to remain round and unable to form dendritic extensions, whereas fibroblasts on coverslips formed lamellipodial extensions and were spread completely without microtubules but were unable to become polarized. Fibroblasts in relaxed collagen matrices lack stress fibers, focal adhesions, and focal adhesion signaling. Fibroblasts on collagen-coated coverslips that were unable to develop stress fibers and focal adhesions, because of either adding blebbistatin to the cells or use of soft coverslips, also formed microtubule-dependent dendritic extensions. Conversely, fibroblasts interacting with precontracted collagen matrices developed stress fibers and lamellipodial extensions and required microtubules for polarization but not spreading. Our findings demonstrate an unexpected relationship between the role of microtubules in cell spreading and the tension state of cell-matrix interactions. At a low tension state (absence of stress fibers and focal adhesions) typical of fibroblasts in relaxed collagen matrices, cells spread with dendritic extensions whose formation requires microtubules; at a high tension state (stress fibers and focal adhesions) typical of cells on coverslips, cells spread with lamellipodial extensions and microtubules are required for cell polarization but not for spreading.

Curcumin protects against radiation-induced acute and chronic cutaneous toxicity in mice and decreases mRNA expression of inflammatory and fibrogenic cytokines

PURPOSE

To determine whether curcumin ameliorates acute and chronic radiation skin toxicity and to examine the expression of inflammatory cytokines (interleukin [IL]-1, IL-6, IL-18, IL-1Ra, tumor necrosis factor [TNF]-alpha, and lymphotoxin-beta) or fibrogenic cytokines (transforming growth factor [TGF]-beta) during the same acute and chronic phases.

METHODS AND MATERIALS

Curcumin was given intragastrically or intraperitoneally to C3H/HeN mice either: 5 days before radiation; 5 days after radiation; or both 5 days before and 5 days after radiation. The cutaneous damage was assessed at 15-21 days (acute) and 90 days (chronic) after a single 50 Gy radiation dose was given to the hind leg. Skin and muscle tissues were collected for measurement of cytokine mRNA.

RESULTS

Curcumin, administered before or after radiation, markedly reduced acute and chronic skin toxicity in mice (p < 0.05). Additionally, curcumin significantly decreased mRNA expression of early responding cytokines (IL-1 IL-6, IL-18, TNF-alpha, and lymphotoxin-beta) and the fibrogenic cytokine, TGF-beta, in cutaneous tissues at 21 days postradiation.

CONCLUSION

Curcumin has a protective effect on radiation-induced cutaneous damage in mice, which is characterized by a downregulation of both inflammatory and fibrogenic cytokines in irradiated skin and muscle, particularly in the early phase after radiation. These results may provide the molecular basis for the application of curcumin in clinical radiation therapy.

Decreased collagen production in chronologically aged skin: roles of age-dependent alteration in fibroblast function and defective mechanical stimulation

Reduced synthesis of collagen types I and III is characteristic of chronologically aged skin. The present report provides evidence that both cellular fibroblast aging and defective mechanical stimulation in the aged tissue contribute to reduced collagen synthesis. The reduction in collagen synthesis due to fibroblast aging was demonstrated by a lower in vitro production of type I procollagen by dermal fibroblasts isolated from skin of young (18 to 29 years) versus old (80+ years) individuals (82 +/- 16 versus 56 +/- 8 ng/ml; P < 0.05). A reduction in mechanical stimulation in chronologically aged skin was inferred from morphological, ultrastructural, and fluorescence microscopic studies. These studies, comparing dermal sections from young and old individuals, demonstrated a greater percentage of the cell surface attached to collagen fibers (78 +/- 6 versus 58 +/- 8%; P < 0.01) and more extensive cell spreading (1.0 +/- 0.3 vs. 0.5 +/- 0.3; P < 0.05) in young skin compared with old skin. These features are consistent with a lower level of mechanical stimulation on the cells in old versus young skin. Based on the findings presented here, we conclude that reduced collagen synthesis in chronologically aged skin reflects at least two different underlying mechanisms: cellular fibroblast aging and a lower level of mechanical stimulation.

Photoaging: Mechanisms and repair

Aging is a complex, multifactorial process resulting in several functional and esthetic changes in the skin. These changes result from intrinsic as well as extrinsic processes, such as ultraviolet radiation. Recent advances in skin biology have increased our understanding of skin homeostasis and the aging process, as well as the mechanisms by which ultraviolet radiation contributes to photoaging and cutaneous disease. These advances in skin biology have led to the development of a diversity of treatments aimed at preventing aging and rejuvenating the skin. The focus of this review is the mechanism of photoaging and the pathophysiology underlying the treatments specifically designed for its prevention and treatment.

LEARNING OBJECTIVES

At the conclusion of this learning activity, participants should be familiar with the mechanism of photoaging, the treatments for photoaging, and the data that supports the use of these treatments.

Matrix metalloproteinase expression in basal cell carcinoma: relationship between enzyme profile and collagen fragmentation pattern

Matrix metalloproteinases (MMPs) with collagenolytic and gelatinolytic activities are up-regulated in basal cell carcinoma. In the present study we demonstrate that the major collagenolytic enzyme detected is MMP-1 (interstitial collagenase) while gelatinolytic enzymes include both MMP-2 (72-kDa gelatinase A) and MMP-9 (92-kDa gelatinase B). Significant fractions of all three enzymes are present as active forms. In spite of the fact that high levels of gelatinolytic enzymes are present, the major fragmentation products resulting from digestion of intact type I collagen are the 1/4 and 3/4 fragments (products of MMP-1-mediated digestion). Thus, it appears that the gelatinolytic enzymes are not capable of degrading the collagen fragments as rapidly as they are produced. Since previous studies have demonstrated that interaction of interstitial fibroblasts with high molecular weight fragments of type I collagen leads to increased MMP production, the present results suggest a mechanism underlying altered function of stromal elements in the connective tissue adjacent to the growing neoplasm.

DNA as classical and quantum information system: Implication to gene expression in normal and cancer cells

Usually, we think about DNA as a molecular machinery system responsible to make proteins. Protein looks like a second side of DNA code because mapping function is based on a classical information system (chemical/physical) by code 43=64. However, in organisms like paramecium DNA works 95% as molecular machinery for proteins synthesis, while in humans it is only about 10%. Is 90% of human genetic structure "junk"? What does other 90% DNA work in human organism? What type of information system, different than classical, does DNA possess? To give answer to this question we are rethinking well-known facts of biomolecules from both classical and quantum information point of view. Basic element in our consideration is hydrogen bond, which possess both classical and quantum properties. Based on new vision of old data we develop synergetic (classical/quantum) model of DNA information processing, which may help for better understanding the functions of "junk" sequence in genetic code. We believe that "junk" sequences may be active regulatory factor of system complexity trough microtubules (centrioles) and water in living systems. Synergetic approach (classical/quantum) of information channels may open a new vision and understanding of the genomic programming and molecular interconnection on distance based on matching classical and quantum properties of hydrogen bonds and entanglement. .

All-trans-retinoic acid suppresses matrix metalloproteinase activity and increases collagen synthesis in diabetic human skin in organ culture

Diabetes increases susceptibility to chronic skin ulceration. The etiology of chronic wound formation in diabetic individuals is multifactoral but may be accelerated by changes in the structure and function of the skin secondary to impaired fibroblast proliferation, decreased collagen synthesis, and increased matrix metalloproteinase (MMP) expression. This study explored the effects of all-trans-retinoic acid (RA) on cellular and biochemical features of diabetic human skin in organ culture. Two-mm skin biopsies from hip or ankle were obtained from diabetic subjects and incubated for 9 days in the absence or presence of 2 micro mol/L RA. Hip skin from non-diabetic individuals served as control. Following organ culture incubation, untreated and RA-treated tissue was examined histologically after staining with hematoxylin and eosin. In parallel, organ culture-conditioned medium collected on days 5 and 7 was assayed for levels of active and total MMP-1 (interstitial collagenase) and MMP-9 (gelatinase B). The same organ culture fluids were assayed for the presence of soluble collagen. In comparison with skin from non-diabetic individuals, diabetic skin demonstrated no major differences in overall epidermal thickness or collagen production (both were increased in RA-treated tissue as compared to non-RA-treated tissue). In contrast, levels of MMP-9 (active forms) were elevated in organ culture fluid from diabetic skin as compared to non-diabetic control skin. In the presence of RA, active forms of both MMP-1 and MMP-9 were reduced. Together, these data suggest that RA has the capacity to improve structure and function of diabetic skin, and that a major effect is on reduction of collagen-degrading MMPs.