鄭 潔，王瑞輝，寇久社

(陜西中醫(yī)學(xué)院 1.針灸推拿系；2.第二附屬醫(yī)院 康復(fù)針灸科，陜西 咸陽 712046)

短篇綜述

炎性反應(yīng)在骨關(guān)節(jié)炎軟骨退變中的作用

鄭 潔1*，王瑞輝1，寇久社2

(陜西中醫(yī)學(xué)院 1.針灸推拿系；2.第二附屬醫(yī)院 康復(fù)針灸科，陜西 咸陽 712046)

慢性炎性反應(yīng)是骨關(guān)節(jié)炎軟骨破壞的一個主要原因。骨關(guān)節(jié)炎性環(huán)境下，軟骨細(xì)胞異?；钴S，細(xì)胞外基質(zhì)重塑加快，引起軟骨細(xì)胞生物力學(xué)環(huán)境的改變，進而推動病理進程。細(xì)胞外基質(zhì)成分和結(jié)構(gòu)的異常改變干擾骨髓間充質(zhì)干細(xì)胞的成軟骨分化，從而使軟骨的修復(fù)無法進行。

骨關(guān)節(jié)炎; 炎性反應(yīng)；細(xì)胞外基質(zhì)；軟骨細(xì)胞；骨髓間充質(zhì)干細(xì)胞

骨性關(guān)節(jié)炎(Osteoarthritis, OA)是一種累及關(guān)節(jié)軟骨、軟骨下骨、滑膜和韌帶等關(guān)節(jié)周圍多種組織的退行性疾病。由于病理機制不明確，目前沒有有效方法可完全阻止OA的病理進程。多種因素可影響OA進程，其中包括持續(xù)存在的炎性反應(yīng)和關(guān)節(jié)軟骨磨損和(/或)創(chuàng)傷引起的關(guān)節(jié)生物力學(xué)環(huán)境的變化。骨關(guān)節(jié)炎性環(huán)境下，軟骨細(xì)胞異?；钴S，細(xì)胞外基質(zhì)重塑加快，引起軟骨細(xì)胞生物力學(xué)環(huán)境的改變，進而加速了OA進程。細(xì)胞外基質(zhì)成分和結(jié)構(gòu)的改變干擾了骨髓間充質(zhì)干細(xì)胞(mesenchymal stem cells, MSCs)的成軟骨分化，從而使軟骨的修復(fù)無法進行。

本綜述將重點關(guān)注炎性反應(yīng)誘導(dǎo)的細(xì)胞外基質(zhì)(extracellular matrix, ECM)重塑是如何干擾軟骨細(xì)胞活動，進而阻止OA軟骨自我修復(fù)的這一過程。

1 炎性反應(yīng)誘導(dǎo)的ECM改變

1.1 OA中ECM合成的改變

ECM成分和結(jié)構(gòu)的改變是OA進程的主要特征。

正常軟骨基質(zhì)主要由Ⅱ型膠原和蛋白聚糖組成，前者構(gòu)成了軟骨的支架，后者發(fā)揮著抗壓和減振的作用。OA大鼠蛋白聚糖基因表達水平顯著下調(diào)[1]。OA中蛋白聚糖以非聚集形式存在，改變了基質(zhì)的滲透性和機械順應(yīng)性[2]。以聚集形式存在的蛋白聚糖的含量減少降低了軟骨的抗壓模量，使組織在負(fù)載時承受更大的壓力。與此相反，膠原的合成率在OA初期升高并持續(xù)維持在高水平，但膠原成分由原來的Ⅱ型轉(zhuǎn)變?yōu)棰裥?主要存在于軟骨下骨)[3]，基質(zhì)膠原成分的這種變化影響了ECM網(wǎng)絡(luò)的機械穩(wěn)定性。這些ECM組成及結(jié)構(gòu)的變化逐步改變了對軟骨細(xì)胞活動具有重要調(diào)節(jié)作用的生物及機械微環(huán)境。

1.2 炎性反應(yīng)誘導(dǎo)的ECM改變

OA進程中，炎性反應(yīng)在ECM數(shù)量與質(zhì)量的改變過程中發(fā)揮了積極作用。機械損傷和(/或)增齡性磨損引發(fā)了包括關(guān)節(jié)軟骨、滑膜、軟骨下骨和韌帶等多種組織的系統(tǒng)性炎性反應(yīng)[4]。炎性環(huán)境下，軟骨細(xì)胞分解代謝加快，最終導(dǎo)致軟骨ECM的降解[5]。與軟骨破壞相關(guān)的多種炎性基因在OA大鼠膝關(guān)節(jié)的表達相繼上調(diào)[1]。這些炎性因子可增加基質(zhì)金屬蛋白酶(MMPs)和蛋白聚糖酶的表達量[6- 7]。細(xì)胞聚集的增加是OA早期階段軟骨細(xì)胞典型的形態(tài)特征，這一過程伴隨著MMP-13的高表達[8]。糖基化終產(chǎn)物受體在OA軟骨細(xì)胞表達的上調(diào)可刺激MAP激酶和核轉(zhuǎn)錄因子κB (NF-κB)的活性，進而使MMP-13的合成增加，加速軟骨基質(zhì)的分解代謝[9]。在軟骨基質(zhì)降解的同時，炎性介質(zhì)還介導(dǎo)了轉(zhuǎn)化生長因子-β(transforming growth factor β, TGF-β)、sry基因型高遷移率組盒9 (SOX9)、胰島素樣生長因子(insulin-like growth factor, IGF)和結(jié)締組織生長因子(connective tissue growth factor, CTGF)等參與軟骨基質(zhì)合成的轉(zhuǎn)錄因子的表達下調(diào)[1]。腱糖蛋白-C (Tenascin-C, TN-C)是ECM中的一種糖蛋白，參與組織損傷和修復(fù)過程，OA患者膝關(guān)節(jié)液中TN-C濃度顯著升高，并參與誘導(dǎo)炎性介質(zhì)和促進ECM降解[10]。OA進程中關(guān)節(jié)軟骨和半月板中雙鏈蛋白聚糖碎片及髖和膝關(guān)節(jié)液中纖連蛋白碎片的含量增加[11]。蛋白聚糖和纖連蛋白均可通過激活toll樣受體(toll-like receptor, TLR)發(fā)揮促炎效應(yīng)[12]。可見，炎性反應(yīng)誘導(dǎo)的基質(zhì)蛋白酶表達上調(diào)和軟骨細(xì)胞ECM合成下調(diào)共同作用，促進軟骨基質(zhì)降解，加速了OA進程。除以上作用，慢性炎性反應(yīng)還可誘導(dǎo)細(xì)胞死亡。健康人軟骨細(xì)胞經(jīng)OA患者關(guān)節(jié)滑液誘導(dǎo)后，軟骨細(xì)胞中白介素-6(IL-6)、 IL-8、單核細(xì)胞趨化蛋白-1 (MCP-1)和血管內(nèi)皮生長因子(VEGF)等細(xì)胞因子表達量明顯上調(diào)，且軟骨細(xì)胞凋亡速度明顯加快[5]。

2 ECM變化對關(guān)節(jié)軟骨細(xì)胞的影響

炎性環(huán)境下，ECM成分和結(jié)構(gòu)的變化引起軟骨細(xì)胞基質(zhì)微環(huán)境改變，進而推動了軟骨細(xì)胞的分解代謝，最終導(dǎo)致軟骨破壞。OA進程中，基質(zhì)代謝不平衡(基質(zhì)降解大于合成)和非軟骨性ECM的形成導(dǎo)致軟骨的機械順應(yīng)性不斷下降。ECM局部硬化灶的增加對軟骨細(xì)胞活動具有抑制作用。軟骨細(xì)胞可感受基質(zhì)硬化并改變其細(xì)胞表型，導(dǎo)致不同類型ECM(如Ⅱ型膠原合成減少，Ⅰ型膠原合成增加)的生成[13- 15]。適當(dāng)?shù)幕|(zhì)硬化可促進軟骨細(xì)胞SOX9, Ⅱ型膠原α1鏈 (COL2α1)和蛋白聚糖的基因表達，而過高或過低的基質(zhì)硬化可通過TGF-β信號通路誘導(dǎo)細(xì)胞向纖維軟骨細(xì)胞表型分化[13]。OA軟骨基質(zhì)成分的變化不僅能影響軟骨細(xì)胞的機械環(huán)境，還可改變軟骨基質(zhì)蛋白與軟骨細(xì)胞間的相互作用。母系蛋白-3(Matrilin-3, MATN3)是健康軟骨基質(zhì)的一種組成成分，有溶解和凝固兩種形式，凝固形MATN3有助于ECM合成和堆積，溶解形MATN3可使人軟骨細(xì)胞分解代謝增加，合成代謝減少[16]。OA患者關(guān)節(jié)軟骨MATN3表達上調(diào)且關(guān)節(jié)液MATN3含量顯著升高[16- 17]，提示MATN3可改變軟骨細(xì)胞的活動。這一結(jié)果表明，通過與軟骨細(xì)胞的相互作用及改變軟骨細(xì)胞的機械環(huán)境，ECM直接或間接的參與了OA進程。軟骨鈣化是OA的一個重要特征，并隨OA嚴(yán)重程度的加重而增多，研究顯示，軟骨鈣化與肥大軟骨細(xì)胞分化密切相關(guān)[18]。纖維連接蛋白是另一影響軟骨細(xì)胞代謝的基質(zhì)成分，基質(zhì)纖維連接蛋白含量與軟骨細(xì)胞凋亡呈顯著正相關(guān)[19]。以上結(jié)果表明，ECM的改變引起基質(zhì)合成下降、分解增加，軟骨細(xì)胞凋亡，加速了OA的病理進程。

3 OA炎性環(huán)境對MSCs成軟骨分化的影響

在特定環(huán)境下，MSCs可向骨、軟骨和脂肪等多種間質(zhì)組織分化，在骨質(zhì)破壞的修復(fù)中發(fā)揮重要作用。軟骨下骨骨髓中MSCs距關(guān)節(jié)軟骨較近，加之其具有成軟骨分化的能力，因此可能成為軟骨修復(fù)的細(xì)胞來源。但關(guān)節(jié)炎性反應(yīng)、ECM結(jié)構(gòu)改變以及損傷軟骨生物力學(xué)環(huán)境的變化均對MSCs的軟骨分化造成影響。研究表明，IL-1β和TNF-α等多種炎性細(xì)胞因子除影響原有軟骨細(xì)胞的自穩(wěn)功能，還可干擾MSCs的成軟骨分化[20- 21]。在OA滑膜來源的條件培養(yǎng)基中，人MSCs的成軟骨分化受到抑制[22]。這些炎性因子抗軟骨生成的作用是通過激活NF-κB信號通路實現(xiàn)的?？梢姡琌A軟骨的炎性條件可抑制MSCs的成軟骨分化，進而阻止了損傷軟骨的再生修復(fù)。

4 ECM改變對MSCs軟骨分化的影響

OA中ECM成分的變化同樣也影響了MSCs的成軟骨分化。隨著OA的進展，軟骨細(xì)胞Ⅰ型膠原合成增多，Ⅱ型膠原合成減少。這一變化將影響到MSCs向軟骨細(xì)胞分化，與Ⅰ型膠原相比，Ⅱ型膠原對細(xì)胞形態(tài)的調(diào)節(jié)作用更有利于誘導(dǎo)軟骨形成[23]。不僅如此，ECM機械特性的變化 (蛋白聚糖流失引起的基質(zhì)硬化)通過對細(xì)胞形態(tài)的調(diào)節(jié)也干擾了MSCs的成軟骨分化[24]。與硬度較高的機械環(huán)境相比，柔軟的機械環(huán)境更有利于MSCs的軟骨分化。有人用不同硬度的聚丙烯酰胺水凝膠作為培養(yǎng)基培養(yǎng)人MSCs，觀察機械環(huán)境對MSCs軟骨分化的影響，結(jié)果發(fā)現(xiàn)不論初始細(xì)胞接種密度如何，較軟的凝膠培養(yǎng)基更有利于人MSCs向軟骨細(xì)胞分化[25]。這一研究充分說明，細(xì)胞與基質(zhì)的相互作用在MSCs成軟骨分化過程中的重要性。由此可見，OA中ECM構(gòu)成及機械特性的改變極大限制了MSCs的成軟骨分化，從而抑制損傷軟骨的再生修復(fù)。

5 小結(jié)

綜上所述，在慢性炎性反應(yīng)及異常基質(zhì)環(huán)境中，軟骨細(xì)胞向肥大細(xì)胞表型轉(zhuǎn)變，導(dǎo)致非軟骨性ECM的合成。炎性反應(yīng)下ECM的變化及軟骨基質(zhì)的降解，加快了生物力學(xué)環(huán)境改變帶來的軟骨退變過程。通過影響固有關(guān)節(jié)軟骨細(xì)胞以及軟骨下骨MSCs對損傷軟骨的修復(fù)，炎性因子和ECM成分的異常改變推動了OA的病理進程。這樣，炎性環(huán)境下ECM的改變與細(xì)胞功能的變化相互影響，形成了一個推動OA病理進展的正反饋環(huán)。

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The role of inflammation in degeneration of arthritic cartilage in osteoarthritis

ZHENG Jie1*, WANG Rui-hui1, KOU Jiu-she2

(1.Dept. of Acupunture and Moxibustion; 2.Dept. of Acupuncture & Rehabilitation of the Second Affiliated Hospital,Shan’xi Universtiy of Chinese Medicine， Xianyang 712046, China)

Chronic inflammation is one of the major causes of cartilage destruction in osteoarthritis. During the progression of osteoarthritis, extracellular matrix of cartilage (ECM) is actively remodeled by chondrocytes in inflammatory conditions. This alteration of ECM, in turn, changes the biomechanical environment of chondrocytes, which further drives the progression of the disease in the presence of inflammation. The changes in ECM composition and structure also prevent participation of mesenchymal stem cells in the repair process by inhibiting their chondrogenic differentiation.

osteoarthritis; inflammation; extracellular matrix; chondrocytes; esenchymal stem cells

2013- 10- 16

2013- 11- 22

陜西省中醫(yī)康復(fù)學(xué)重點學(xué)科建設(shè)項目(陜中醫(yī)藥發(fā)[2011]46號)

*通信作者(correspondingauthor)： 15005178161@163.com

1001-6325(2014)08-1146-04

R 683

A