2.79J/3.96J/20.441/HST522JUNIT CELL PROCESSES ASSOCIATED WITH WOUND HEALINGM. Spector, Ph.D.Massachusetts Institute of TechnologyHarvard Medical SchoolBrigham and Women’s HospitalVA Boston Healthcare SystemAcuteChronicPhotos and diagrams of skin wound healing removed due to copyright restrictions.InjuryInflammation(Vascularized tissue)HealingProcessRegeneration* Repair (Scar)CT: bone CT: cartilageEp: epidermis Nerve Muscle: smooth Muscle: cardiac, skel.WOUND HEALINGRoots of the Tissue Response 4 Tissue CategoriesConnective TissueEpitheliumNerveMuscle*spontaneousResolutionSlightNo HealingNonvascularizedtissueInjuryVascular ResponseInflammationTissue of Labile Tissue ofand Stable Cells Permanent CellsFramework Framework ScarIntact DestroyedRegeneration ScarRESPONSE TO IMPLANTS:WOUND HEALINGSurgical ImplantationVascular ResponseClottingPhagocytosisNeovascularizationNew Collagen SynthesisTissue of Labile and Stable Cells Tissue of Permanent CellsFramework Framework ScarringIntact Destroyed (fibrous encapsulation;synovium)Regen. Scarring Chronic Inflammation(incorp. (fibrous encapsulation;of implant) synovium)Chronic InflammationRESPONSE TO IMPLANTS:WOUND HEALINGAcute InflammationGranulationTissueImplant MovementInc. timeAcute Inflammation – Local/Gross ChangesThe cardinal signs of acute inflammation are:RednessHeatSwellingPainLoss of functionGranulation TissuePhoto removed due to copyright restrictions.UNIT CELL PROCESSESCell + Matrix Product + RegulatorRegulatorMitosisSynthesisMigrationContractionEndocytosisExocytosisUCPConnectiveTissueEpitheliaMuscleNerveECMAdhesionProteinCollagenBiomaterialIntegrinUNIT CELL PROCESSESVASCULAR RESPONSEEndothelial Cell + Basal Lamina Leakage + Reg.ContractionDiagrams removed due tocopyright restrictions.UNIT CELL PROCESSESVASCULAR RESPONSEEndothelial Cell + Basal Lamina Leakage + Reg.ContractionPlatelet + serum Reg.ExocytosisBasophil + serum Reg.ExocytosisExocytosisSeratoninHistaminePAF*Seratonin(circulation)(circulation)(tissue)* PAF, platelet activating factorMast Cell + ECM Reg.Mast cells can be identified by their darkly staining granules which contain histamine and heparin. They are involved in the inflammatory response and are very common near blood vessels. Photo of mast cell removed due to copyright restrictions.See Figure 10.45 in Berg, J. M. et al. Biochemistry. 5thedition. W. H. Freeman, 2002.http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=stryer&part=A1378&rendertype=figure&id=A1413UNIT CELL PROCESSESVASCULAR RESPONSEEndothelial Cell + Basal Lamina Leakage + Reg.ContractionSmooth Muscle + Basal Lamina Vasoconstrict.ContractionPlatelet + serum Reg.ExocytosisBasophil + serum Reg.ExocytosisMast Cell + ECM Reg.ExocytosisHistamineCellSeratoninHistaminePAFSeratoninUNIT CELL PROCESSESCLOTTINGPlatelet + Collagen Coagulation factorsExocytosisFibrin polymerizationImage removed due to copyright restrictions.See Fig. 10.2, “The role of platelets in thrombosis.”In Rubin, E., and H. M. Reisner, editors. Essentials of Rubin’s Pathology. Lippincott Williams & Wilkins, 2008.http://books.google.com/books?id=7HdzBBhtxycC&pg=PA197Scanning electron micrograph shows the fine structure of a fibrin clot that has entangled 2 red blood cells. Platelets released from the circulation and exposed to the air use fibrinogen from the blood plasma to spin a mesh of fibrin. Photo removed due to copyright restrictions.See http://www.cellsalive.com/cover7.htm.UNIT CELL PROCESSESCLOTTINGPlatelet + Collagen Coaguation factorsExocytosisBasophil + serum Reg.ExocytosisMast Cell + ECM Reg.ExocytosisFibrin polymerizationPAFPAF(In Circulation)(In Tissue)UNIT CELL PROCESSESPHAGOCYTOSISMacrophage + Part.* Sol. Part + Reg.Endocytosis* Cell debris and degraded ECMAlveolar macrophage phagocytosis of E. coli (lung pleural cavity). The macrophage is the large, yellowish cell with projections; the bacterial cells are small, rod-like, blue cells.Microscope image removed due to copyright restrictions.See http://www.visualsunlimited.com/c/visualsunlimited/image/I0000pCnNefPj_tE(Dennis Kunkel Microscopy)Scanning electron micrograph shows a human macrophage (gray) approaching a chain of Streptococcus pyogenes (yellow). Riding atop the macrophage is a spherical lymphocyte. Macrophages and lymphocytes can be found near an infection, and the interaction between these cells is important in eliminating infection. Photo removed due to copyright restrictions.See http://www.cellsalive.com/cover5.htm.This scanning electron micrograph (courtesy of Drs. Jan M. Orenstein and Emma Shelton) shows a single macrophage surrounded by several lymphocytes.http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Blood.htmlCourtesy of Jan M. Orenstein. Used with permission.Macrophage phagocytosing 2 erythrocytes (red blood cells).Photo removed due to copyright restrictions.Transmission electron micrograph showing a macrophagePhoto removed due to copyright restrictions.Macrophage containing engulfed bacteria The bacteria are colored red for easy identification. The large purple structure at the bottom of the cell is the cell nucleus. http://hei.org/research/aemi/mac.htmImage removed due to copyright restrictions.Polyethylene Particles in Peri-prosthetic TissuesLight Microscopy1 mmTransmission Electron Microscopy, TEMNucleusSee Benz E, Spector M, et al., Biomat. 2001;22:2835UNIT CELL PROCESSESPHAGOCYTOSISMacrophage + Part.* Sol. Part + Reg.Endocytosis* Cell debris and degraded ECMFibroblast + ECM + Reg.Endothelial Cell + ECM + Reg.Neovascularization/Angiogenesis/New Blood Vessel FormationFigure by MIT OpenCourseWare.1) Basement membranedegradation2) Migration3) Mitosis4) DifferentiationParent vesselUNIT CELL PROCESSESNEOVASCULARIZATIONEndothelial Cell + Basal Lamina + Reg.Endothelial Cell + ECM + Reg.Endothelial Cell + ECM + Reg.Synthesis: enzymesMigrationMitosisUNIT CELL PROCESSESNEW COLLAGEN SYNTHESISFibroblast + ECM + Reg.Fibroblasts are the most common cell type in connective tissue. They are large, long, branching cells that produce and secrete the collagen fibers and proteoglycans.Photo removed due to copyright restrictions.Once the connective tissue has been formed, the immature fibroblast will become