Osteoblasto: Diferenzas entre revisións

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[[Ficheiro:Active osteoblasts.jpg|thumb|right|Osteoblastos activos.]]
[[Ficheiro:Active osteoblasts.jpg|thumb|right|Osteoblastos activos.]]


'''Osteoblasts''' (from the [[Greek language|Greek]] words for "[[bone]]" and "germ" or embryonic) are mononucleate [[cell (biology)|cell]]s that are responsible for bone formation; in essence, osteoblasts are specialized [[fibroblast]]s that in addition to fibroblastic products, express [[bone sialoprotein]] and [[osteocalcin]].<ref name="Salentijn">Salentijn, L. ''Biology of Mineralized Tissues: Cartilage and Bone'', [[Columbia University College of Dental Medicine]] post-graduate dental lecture series, 2007</ref>
Os '''osteoblastos''' (do grego "[[óso]]" e "xerme" ou "embrionario") son as células encargadas da formación do óso, que se poden considerar como [[fibroblasto]]s especializados que ademais dos produtos fibroblásticos, expresan [[sialoproteína ósea|sialoproteínas óseas]] e [[osteocalcina]].<ref name="Salentijn">Salentijn, L. ''Biology of Mineralized Tissues: Cartilage and Bone'', [[Columbia University College of Dental Medicine]] post-graduate dental lecture series, 2007</ref>


Osteoblasts produce a [[extracellular matrix|matrix]] of [[osteoid]], which is composed mainly of Type I [[collagen]]. Osteoblasts are also responsible for mineralization of this matrix. Zinc, copper and sodium are some of the minerals required in this process. Bone is a dynamic tissue that is constantly being reshaped by osteoblasts, in charge of production of matrix and mineral, and [[osteoclasts]], which remodel the tissue. Osteoblast cells tend to decrease with age, affecting the balance of formation and resorption in the [[bone tissue]].<ref name=Dippolito1999>{{cite journal|author = D’ippolito, Gianluca|coauthors = Schiller, Paul C.; Ricordi, Camillo; Roos, Bernard A.; Howard, Guy A.|year = 1999|title = Age-Related Osteogenic Potential of Mesenchymal Stromal Stem Cells from Human Vertebral Bone Marrow|journal = Journal of Bone and Mineral Research|volume = 14|issue = 7|pages = 1115–1122|doi = 10.1359/jbmr.1999.14.7.1115|pmid = 10404011}}</ref>
Os osteoblastos producen a [[matriz extracelular]] do tecido óseo (osteoide), que está composta principalmente de [[coláxeno]] de tipo I. Os osteoblastos son tamén responsables da mineralización desta matriz. O [[cinc]], o [[cobre]] e o [[sodio]] son algúns dos ións minerais que se requiren neste proceso. O óso é un tecido dinámico que está constantemente sendo remodelado polos osteoblastos, encargados da produción da matriz e a parte mineral do tecido, e polos [[osteoclasto]]s, que destrúen parte do tecido durante a remodelación. Os osteoblastos tenden a decrecer en número coa idade, o que afecta ao balance entre a formación e a reabsorción do [[tecido óseo]].<ref name=Dippolito1999>{{cite journal|author = D’ippolito, Gianluca|coauthors = Schiller, Paul C.; Ricordi, Camillo; Roos, Bernard A.; Howard, Guy A.|year = 1999|title = Age-Related Osteogenic Potential of Mesenchymal Stromal Stem Cells from Human Vertebral Bone Marrow|journal = Journal of Bone and Mineral Research|volume = 14|issue = 7|pages = 1115–1122|doi = 10.1359/jbmr.1999.14.7.1115|pmid = 10404011}}</ref>


==Osteoxénese==
==Osteoxénese==
Os osteoblastos orixínanse a partir de '''células osteoproxenitoras''' localizadas na capa profunda do [[periostio]] que rodea os ósos e na [[medula ósea]]. As células osteoproxenitoras son células inmaduras que expresan o [[factor de transcrición]] regulatorio principal [[Cbfa1|Cbfa1/Runx2]].
Osteoblasts arise from '''osteoprogenitor cells''' located in the deeper layer of [[periosteum]] and the [[bone marrow]]. Osteoprogenitors are immature [[progenitor cell]]s that express the master regulatory [[transcription factor]] [[Cbfa1|Cbfa1/Runx2]].


Osteoprogenitors are induced to differentiate under the influence of [[growth factor]]s, in particular the '''[[bone morphogenetic protein]]s''' (BMPs).<ref name="Agata, H. 2007">{{cite journal|doi=10.1177/154405910708600113|last1=Agata|first1=H|last2=Asahina|first2=I|last3=Yamazaki|first3=Y|last4=Uchida|first4=M|last5=Shinohara|first5=Y|last6=Honda|first6=MJ|last7=Kagami|first7=H|last8=Ueda|first8=M|title=Effective bone engineering with periosteum-derived cells.|journal=Journal of dental research|volume=86|issue=1|pages=79–83|year=2007|pmid=17189468}}</ref> Aside from BMPs, other growth factors including fibroblast growth factor (FGF),<ref name="Agata, H. 2007"/> [[platelet-derived growth factor]] (PDGF) and [[transforming growth factor|transforming growth factor beta]] (TGF-β) may promote the division of osteoprogenitors and potentially increase osteogenesis.
As células osteoproxenitoras son inducidas a diferenciarse baixo a influencia de [[factor de crecemento|factores de crecemento]], en particular as [[proteína morfoxenética ósea|proteínas morfoxenéticas óseas]] (BMPs).<ref name="Agata, H. 2007">{{cite journal|doi=10.1177/154405910708600113|last1=Agata|first1=H|last2=Asahina|first2=I|last3=Yamazaki|first3=Y|last4=Uchida|first4=M|last5=Shinohara|first5=Y|last6=Honda|first6=MJ|last7=Kagami|first7=H|last8=Ueda|first8=M|title=Effective bone engineering with periosteum-derived cells.|journal=Journal of dental research|volume=86|issue=1|pages=79–83|year=2007|pmid=17189468}}</ref> Ademais das BMPs, outros factores de crecemento como o factor de crecemento dos fibroblastos (FGF),<ref name="Agata, H. 2007"/> o [[factor de crecemento derivado das plaquetas]] (PDGF) e o [[factor de crecemento transformante]] beta (TGF-β) poden promover a división das células osteoproxenitoras e potencialmente incrementar a osteoxénese.


Once osteoprogenitors start to differentiate into osteoblasts, they begin to express a range of genetic markers including [[Osterix]], [[collagen|Col1]],<ref name="Ringe, J. 2008">{{cite journal|last1=Ringe|first1=J|last2=Leinhase|first2=I|last3=Stich|first3=S|last4=Loch|first4=A|last5=Neumann|first5=K|last6=Haisch|first6=A|last7=Häupl|first7=T|last8=Manz|first8=R|last9=Kaps|first9=C|title=Human mastoid periosteum-derived stem cells: promising candidates for skeletal tissue engineering.|journal=Journal of tissue engineering and regenerative medicine|volume=2|issue=2-3|pages=136–46|year=2008|pmid=18383554|doi=10.1002/term.75}}</ref> [[Bone sialoprotein|BSP]], [[Macrophage colony-stimulating factor|M-CSF]], [[alkaline phosphatase|ALP]],<ref>{{cite journal|last1=Szulc|first1=P|last2=Garnero|first2=P|last3=Marchand|first3=F|last4=Duboeuf|first4=F|last5=Delmas|first5=PD|title=Biochemical markers of bone formation reflect endosteal bone loss in elderly men--MINOS study.|journal=Bone|volume=36|issue=1|pages=13–21|year=2005|pmid=15663998|doi=10.1016/j.bone.2004.09.004}}</ref> [[osteocalcin]],<ref name="Ringe, J. 2008"/> [[osteopontin]], and [[osteonectin]]. Although the term osteoblast implies an immature cell type, osteoblasts are in fact the mature bone cells entirely responsible for generating bone tissue in animals and humans.
Unha vez que as células osteoproxenitoras comezan a se diferenciar en osteoblastos, empezan a expresar un conxunto de marcadores xenéticos como o [[Osterix]], [[colláxeno|Col1]],<ref name="Ringe, J. 2008">{{cite journal|last1=Ringe|first1=J|last2=Leinhase|first2=I|last3=Stich|first3=S|last4=Loch|first4=A|last5=Neumann|first5=K|last6=Haisch|first6=A|last7=Häupl|first7=T|last8=Manz|first8=R|last9=Kaps|first9=C|title=Human mastoid periosteum-derived stem cells: promising candidates for skeletal tissue engineering.|journal=Journal of tissue engineering and regenerative medicine|volume=2|issue=2-3|pages=136–46|year=2008|pmid=18383554|doi=10.1002/term.75}}</ref> [[sialoproteína ósea|BSP]], [[factor estimulante das colonias de macrófagos|M-CSF]], [[fosfatase alcalina|ALP]],<ref>{{cite journal|last1=Szulc|first1=P|last2=Garnero|first2=P|last3=Marchand|first3=F|last4=Duboeuf|first4=F|last5=Delmas|first5=PD|title=Biochemical markers of bone formation reflect endosteal bone loss in elderly men--MINOS study.|journal=Bone|volume=36|issue=1|pages=13–21|year=2005|pmid=15663998|doi=10.1016/j.bone.2004.09.004}}</ref> [[osteocalcina]],<ref name="Ringe, J. 2008"/> [[osteopontina]], e [[osteonectina]]. Aínda que o termo osteoblasto implica un tipo de célula inmadura, os osteoblastos son de feito células óseas maduras enteiramente responsables da xeración do tecido óseo en animais e humanos.


==Morfoloxía e tinguidura==
==Morfoloxía e tinguidura==

Revisión como estaba o 26 de novembro de 2011 ás 17:46

Osteoblastos activos.

Os osteoblastos (do grego "óso" e "xerme" ou "embrionario") son as células encargadas da formación do óso, que se poden considerar como fibroblastos especializados que ademais dos produtos fibroblásticos, expresan sialoproteínas óseas e osteocalcina.[1]

Os osteoblastos producen a matriz extracelular do tecido óseo (osteoide), que está composta principalmente de coláxeno de tipo I. Os osteoblastos son tamén responsables da mineralización desta matriz. O cinc, o cobre e o sodio son algúns dos ións minerais que se requiren neste proceso. O óso é un tecido dinámico que está constantemente sendo remodelado polos osteoblastos, encargados da produción da matriz e a parte mineral do tecido, e polos osteoclastos, que destrúen parte do tecido durante a remodelación. Os osteoblastos tenden a decrecer en número coa idade, o que afecta ao balance entre a formación e a reabsorción do tecido óseo.[2]

Osteoxénese

Os osteoblastos orixínanse a partir de células osteoproxenitoras localizadas na capa profunda do periostio que rodea os ósos e na medula ósea. As células osteoproxenitoras son células inmaduras que expresan o factor de transcrición regulatorio principal Cbfa1/Runx2.

As células osteoproxenitoras son inducidas a diferenciarse baixo a influencia de factores de crecemento, en particular as proteínas morfoxenéticas óseas (BMPs).[3] Ademais das BMPs, outros factores de crecemento como o factor de crecemento dos fibroblastos (FGF),[3] o factor de crecemento derivado das plaquetas (PDGF) e o factor de crecemento transformante beta (TGF-β) poden promover a división das células osteoproxenitoras e potencialmente incrementar a osteoxénese.

Unha vez que as células osteoproxenitoras comezan a se diferenciar en osteoblastos, empezan a expresar un conxunto de marcadores xenéticos como o Osterix, Col1,[4] BSP, M-CSF, ALP,[5] osteocalcina,[4] osteopontina, e osteonectina. Aínda que o termo osteoblasto implica un tipo de célula inmadura, os osteoblastos son de feito células óseas maduras enteiramente responsables da xeración do tecido óseo en animais e humanos.

Morfoloxía e tinguidura

Osteoblastos (frecha) revestindo o óso e osteocitos nas lagoas do óso.

Hematoxylin and eosin staining reveals that the cytoplasm of osteoblasts is basophilic due to the presence of a large amount of rough endoplasmic reticulum. A large Golgi apparatus is also present in the centre. The nucleus is spherical and large. Active osteoblasts synthesize, and stain positively for, Type-I collagen and alkaline phosphatase.

Osteoblastos e osteocitos

Artigo principal: osteocito.

Osteoblasts that become trapped in the bone matrix and remain isolated in lacunae become osteocytes. They cease to generate osteoid and mineralized matrix, and instead act in a paracrine manner on active osteoblasts. They are believed to respond to mechanosensory stimuli.[6][7]

Notas

  1. Salentijn, L. Biology of Mineralized Tissues: Cartilage and Bone, Columbia University College of Dental Medicine post-graduate dental lecture series, 2007
  2. D’ippolito, Gianluca; Schiller, Paul C.; Ricordi, Camillo; Roos, Bernard A.; Howard, Guy A. (1999). "Age-Related Osteogenic Potential of Mesenchymal Stromal Stem Cells from Human Vertebral Bone Marrow". Journal of Bone and Mineral Research 14 (7): 1115–1122. PMID 10404011. doi:10.1359/jbmr.1999.14.7.1115.  A referencia usa o parámetro obsoleto |coauthors= (Axuda)
  3. 3,0 3,1 Agata, H; Asahina, I; Yamazaki, Y; Uchida, M; Shinohara, Y; Honda, MJ; Kagami, H; Ueda, M (2007). "Effective bone engineering with periosteum-derived cells.". Journal of dental research 86 (1): 79–83. PMID 17189468. doi:10.1177/154405910708600113. 
  4. 4,0 4,1 Ringe, J; Leinhase, I; Stich, S; Loch, A; Neumann, K; Haisch, A; Häupl, T; Manz, R; Kaps, C (2008). "Human mastoid periosteum-derived stem cells: promising candidates for skeletal tissue engineering.". Journal of tissue engineering and regenerative medicine 2 (2-3): 136–46. PMID 18383554. doi:10.1002/term.75. 
  5. Szulc, P; Garnero, P; Marchand, F; Duboeuf, F; Delmas, PD (2005). "Biochemical markers of bone formation reflect endosteal bone loss in elderly men--MINOS study.". Bone 36 (1): 13–21. PMID 15663998. doi:10.1016/j.bone.2004.09.004. 
  6. Ehrlich, P. J.; Lanyon, L. E. (2002). "Mechanical Strain and Bone Cell Function: A Review". Osteoporosis International 13 (9): 688–700. PMID 12195532. doi:10.1007/s001980200095.  A referencia usa o parámetro obsoleto |coauthors= (Axuda)
  7. You, J.; Yellowley, C. E.; Donahue, H. J.; Zhang, Y.; Chen, Q.; Jacobs, C. R. (2000). "Substrate Deformation Levels Associated With Routine Physical Activity Are Less Stimulatory to Bone Cells Relative to Loading-Induced Oscillatory Fluid Flow". Journal of Biomechanical Engineering 122 (4): 387–394. PMID 11036562. doi:10.1115/1.1287161.  A referencia usa o parámetro obsoleto |coauthors= (Axuda)

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