MIT20_441JF09_lec18b_iy

MIT20_441JF09_lec18b_iy - Skin synthesis in vivo (induced...

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Skin synthesis in vivo (induced regeneration)* 1. Experimental parameters 2. Synthesis of epidermis and BM 3. Synthesis of dermis 4. Partial synthesis of skin 5. Comparative regenerative activity of reactants 6. Overall mechanism of skin regeneration ________________________ * Tissue and Organ Regeneration in Adults , Yannas, Springer, 2001, Ch. 5.
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1. Experimental parameters (skin) A. Anatomically well-defined defect Designate experimental volume Delete nonregenerative tissue(s) Anatomical bounds Containment of exudate B. Timescale of observations Initial state: defect generated Final state: defect closed Note : Remodeling continues after closure
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Figure removed due to copyright restrictions. See Figure 3.1 in [TORA]. Diagram with four types of anatomically well-defects for study of induced skin regeneration. [TORA] = Yannas, I. V. Tissue and Organ Regeneration in Adults . New York, NY: Springer-Verlag, 2001. ISBN: 9780387952147. [Preview in Google Books ]
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1. Experimental parameters (skin) [Cont.] C. Assays of final state (product of synthesis) -Literature describes several assays, unrelated to nature of product synthesized (e.g., time of closure by epithelialization, % take of graft, ability to cross histocompatibility barriers). -Required assays are both qualitative (which tissue was synthesized?) and quantitative (How much?)
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2. Synthesis of an epidermis Structure . Five cell layers (strata); 100 μ m thick. Basal layer is closest to BM…stratum corneum is farthest out. Cell maturation gradient (increasing keratin content away from BM). Tissue turns over every 25-50 days. Function . Protection against dehydration and microorganisms (primarily stratum corneum). Also protection against mechanical, thermal, chemical, UV insults.
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Schematic view of epidermis Figure by MIT OpenCourseWare.
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2. Synthesis of an epidermis [Cont.] Synthesis in vitro . Epidermis trypsinization dissociated keratinocytes (KC). Condensation of KC to epidermis requires nondiffusible substrate (e.g., plastic surface) but not growth factors or dermal substrate. In vivo . Epidermis synthesized spontaneously by KC, originally at the defect edge. KC dissociate spontaneously, migrate over residual dermis toward “center” of defect, synthesize BM and reform epidermis.
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2B. Synthesis of BM Structure . BM structure similar in all organs. 100 nm thick. Egg-carton topology in skin. Layer closest to epidermis is 20-40 nm thick (lamina lucida; mostly laminin). Intermediate layer 40-50 nm thick (lamina densa; type IV collagen). Next to stroma is fibroreticular layer (anchoring fibrils based on type VII collagen) that connects with type I collagen fibers in dermis via anchoring plaques. Hemidesmosomes connect basal cells to BM (tonofilaments).
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(blister) through dermis: irreversible healing through epidermis: reversible healing between epidermis and dermis: reversible healing Figure removed due to copyright restrictions. See Figure 2.6 in [TORA].
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This note was uploaded on 11/11/2011 for the course BIO 2.797j taught by Professor Matthewlang during the Fall '06 term at MIT.

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MIT20_441JF09_lec18b_iy - Skin synthesis in vivo (induced...

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