人体细胞和肠道微生物数量比例课件.ppt

对人体细胞和微生物数量的改进估计,RonSender,1.OriginofprevalentclaimsintheliteratureonthenumberofbacterialcellsInhumans,为什么大家会普遍认为肠道微生物数量是人体细胞的十倍，本文作者对文献进行了追溯，结果显示1977年Savage,annu,Rev.Microbiol引用超过一千。而它的计算基础是胃肠道容积为1L，肠道微生物浓度为1011/g.,2.Distributionofbacteriaindifferenthumanorgans,不同部位的微生物数量相差很大，由上表可知，人体微生物约90%都集中在结肠。所以作者统计了不同文献的结肠微生物浓度，平均值为0.92*1011/g.,3.Concentrationofbacteriainthecolon,4.Thenumberofhumancellsina“standard”adultmale,Amass-basedorder-of-magnitudeestimateforthisnumberassumesa102kgman,whichisdividedbythemassofa“representative”mammalian,cell10-12-10-11kg(assumingcellvolumesof1,000-10,000m3,spectively),thusarrivingat1013-1014cells.,OnestudyusedaDNA-centeredmethod(Baserga,1985).Themethodbeginsbyestimatingthenumberofcellsinthebodyofa25gmousebydividingthetotalamountofDNA(statedtobe20mg)bytheDNAcontentofonediploidmousecell(610-12gDNApercell)toget3109cellsina25gmouse.Thenextrapolatefrommousetohumanbyusingtheratioofmassestoget1013cellsinthehumanbody.ThismethodexcludescellsthatdonotcontainDNA,suchasredbloodcellsandplatelets.,Summingoveratotalof56cellcategories(Bianconietal.,2013)resultedinanoverallestimateof3.71013humancellsinthebody(SD0.81013,i.e.CVof22%),5.Updatedinventoryofhumancellsinthebody,Wefocusonthesixcelltypesthatwererecentlyidentified(Bianconietal.,2013)tocomprise97%ofthehumancellcount:redbloodcellaccountingfor70%),glialcells(8%),endothelialcells(7%),dermafibroblasts(5%),platelets(4%)andbonemarrowcells(2%).Theother50celltypesaccountfortheremaining3%.,5.Updatedinventoryofhumancellsinthebody,Redbloodcells:,(Boer,1984;FeldschuhandEnson,1977;Nadleretal.,1962;Snyderetal.,1975)4.9L,(Ambayyaetal.,2014;Dosooetal.,2012;Nordinetal.,2004;Pekelharingetal.,2010;VolkmerandHeinemann,2011;Wakemanetal.,2007)5.01012cells/L(SEM1.2%,CV7%),(SEM1.6%,CV9%),Thisledtoatotalof2.51013redbloodcells(SEM2%,CV12%),Thisissimilartotheearlierreportof2.61013cells(Bianconietal.,2013).,5.Updatedinventoryofhumancellsinthebody,glialcells:Thenumberofglialcellswaspreviouslyreportedas31012(Bianconietal.,2013)estimateisbaseda10:1ratiobetweenglialllsandneuronsinthebrain.,However,arecentanalysis(Azevedoetal.,2009)revisitsthisvalueandafteranalyzingthevariationinbetweenbrainregionsconcludesthattheratioiscloseto1:1.Thestudyconcludesthatthereare8.51010glialcells(CV11%)inthebrainandasimilarnumberofneuronsandsoweusethesevalueshere.,5.Updatedinventoryofhumancellsinthebody,endothelialcells:Thenumberofendothelialcellsinthebodywasearlierestimatedat2.51012cells(CV40%),bytakingthemeansurfaceareaofoneendothelialcell(Bianconietal.,2013)anddividingitintothetotalsurfaceareaofthebloodvessels,basedonatotalcapillarylengthof8109cm.Wecouldnotfindaprimarysourceforthetotallengthofthecapillarybedandthusdecidedtorevisitthisestimate.Weuseddataregardingthepercentageofthebloodvolumeineachtypeofbloodvesse(LeggettandWilliamst,1991).Usingmeandiametersfordifferentbloodvessels(Burton,1954)wewereabletoderivethetotallengthofeachtypeofvessel(arteries,veins,capillariesetc.)anditscorrespondingsurfacearea.Dividingbythemeansurfaceareaoneendothelialcell(Fltou,2011)wederiveatotalestimateof61011cells,5.Updatedinventoryofhumancellsinthebody,dermalfibroblast:Thenumberofdermalfibroblastwaspreviouslyestimatedtobe1.851012(Bianconietal.,2013),basedonmultiplyingthetotalsurfaceareaofthehumanbody(SA=1.85m2(Herman,2007)byanarealdensityofdermalfibroblasts(RandolphandSimon,1998).Thedermisiscomposedoftwomainlayers:papillarydermis(about10%ofthedermisthickness)andreticulardermis(theother90%)(McGrathetal.,2004).2.61010cells.,5.Updatedinventoryofhumancellsinthebody,6.Masscenteredapproachassanitycheckforcellcount,Forareferencemanmassof70kg,25%isextracellularfluid(Shenetal.,2007),another7%isextra-cellularsolids(Shenetal.,2007),thusweneedtoaccountfor47kgofcellmass(includingfat).,作者对人体的细胞数量进行了重新估计，84%为红细胞（质量2.5Kg），5%为血小板；脂肪占0.2%（质量13Kg），肌肉细胞占0.001%（质量20Kg）。,7.Theratioofbacteriatohumancellsintheadultbody,8.Discussion,wethinkthatupdatingtheratioofbacteriatohumancellsfrom10:1or100:1tocloserto1:1doesnottakeawayfromthebiologicalimportanceofthemicrobiota.Yet,weareconvincedthatanum