人体细胞和肠道生物数量比例

对人体细胞和微生物数量旳改善估计RonSender1.OriginofprevalentclaimsintheliteratureonthenumberofbacterialcellsInhumans为何大家会普遍以为肠道微生物数量是人体细胞旳十倍，本文作者对文件进行了追溯，成果显示1977年Savage,annu,Rev.Microbiol引用超出一千。而它旳计算基础是胃肠道容积为1L，肠道微生物浓度为1011/g.2.Distributionofbacteriaindifferenthumanorgans不同部位旳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件旳结肠微生物浓度，平均值为0.92*1011/g.3.Concentrationofbacteriainthecolon4.Thenumberofhumancellsina“standard”adultmaleAmass-basedorder-of-magnitudeestimateforthisnumberassumesa102kgman,whichisdividedbythemassofa“representative”mammalian,cell10-12-10-11kg(assumingcellvolumesof1,000-10,000µm3,spectively),thusarrivingat1013-1014cells.OnestudyusedaDNA-centeredmethod(Baserga,1985).Themethodbeginsbyestimatingthenumberofcellsinthebodyofa25gmousebydividingthetotalamountofDNA(statedtobe20mg)bytheDNAcontentofonediploidmousecell(6·10-12gDNApercell)toget≈3·109cellsina25gmouse.Thenextrapolatefrommousetohumanbyusingtheratioofmassestoget≈1013cellsinthehumanbody.ThismethodexcludescellsthatdonotcontainDNA,suchasredbloodcellsandplatelets.Summingoveratotalof56cellcategories(Bianconietal.,2023)resultedinanoverallestimateof3.7·1013humancellsinthebody(SD0.8·1013,i.e.CVof22%)5.UpdatedinventoryofhumancellsinthebodyWefocusonthesixcelltypesthatwererecentlyidentified(Bianconietal.,2023)tocomprise97%ofthehumancellcount:redbloodcellaccountingfor70%),glialcells(8%),endothelialcells(7%),dermafibroblasts(5%),platelets(4%)andbonemarrowcells(2%).Theother50celltypesaccountfortheremaining3%.5.UpdatedinventoryofhumancellsinthebodyRedbloodcells:(Boer,1984;FeldschuhandEnson,1977;Nadleretal.,1962;Snyderetal.,1975)4.9L(Ambayyaetal.,2023;Dosooetal.,2023;Nordinetal.,2023;Pekelharingetal.,2023;VolkmerandHeinemann,2023;Wakemanetal.,2023)5.0·1012cells/L(SEM1.2%,CV7%)(SEM1.6%,CV9%)Thisledtoatotalof2.5·1013redbloodcells(SEM2%,CV12%)Thisissimilartotheearlierreportof2.6·1013cells(Bianconietal.,2023).5.Updatedinventoryofhumancellsinthebodyglialcells:Thenumberofglialcellswaspreviouslyreportedas3·1012(Bianconietal.,2023)estimateisbaseda10:1ratiobetweenglialllsandneuronsinthebrain.However,arecentanalysis(Azevedoetal.,2023)revisitsthisvalueandafteranalyzingthevariationinbetweenbrainregionsconcludesthattheratioiscloseto1:1.Thestudyconcludesthatthereare8.5·1010glialcells(CV11%)inthebrainandasimilarnumberofneuronsandsoweusethesevalueshere.5.Updatedinventoryofhumancellsinthebodyendothelialcells:Thenumberofendothelialcellsinthebodywasearlierestimatedat2.5·1012cells(CV40%),bytakingthemeansurfaceareaofoneendothelialcell(Bianconietal.,2023)anddividingitintothetotalsurfaceareaofthebloodvessels,basedonatotalcapillarylengthof8·109cm.Wecouldnotfindaprimarysourceforthetotallengthofthecapillarybedandthusdecidedtorevisitthisestimate.Weuseddataregardingthepercentageofthebloodvolumeineachtypeofbloodvesse(LeggettandWilliamst,1991).Usingmeandiametersfordifferentbloodvessels(Burton,1954)wewereabletoderivethetotallengthofeachtypeofvessel(arteries,veins,capillariesetc.)anditscorrespondingsurfacearea.Dividingbythemeansurfaceareaoneendothelialcell(Félétou,2023)wederiveatotalestimateof6·1011cells5.Updatedinventoryofhumancellsinthebodydermalfibroblast:Thenumberofdermalfibroblastwaspreviouslyestimatedtobe1.85·1012(Bianconietal.,2023),basedonmultiplyingthetotalsurfaceareaofthehumanbody(SA=1.85m2(Herman,2023))byanarealdensityofdermalfibroblasts(RandolphandSimon,1998).Thedermisiscomposedoftwomainlayers:papillarydermis(about10%ofthedermisthickness)andreticulardermis(theother90%)(McGrathetal.,2023).2.6∙1010cells.5.Updatedinventoryofhumancellsinthebody6.MasscenteredapproachassanitycheckforcellcountForareferencemanmassof70kg,25%isextracellularfluid(Shenetal.,2023),another7%isextra-cellularsolids(Shenetal.,2023),thusweneedtoaccountfor≈47kgofcellmass(includingfat).作者对人体旳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.Theratioofbacteriatohumancellsintheadultbody8.Discussionwethinkthatupdatingtheratioofbacteriatohumancellsfrom10:1or100:1tocloserto1:1doesnottakeawayfromthebiologicalimportanceofthemicrobiota.Yet,wearecon