細胞向胞外環(huán)境中釋放多種來源于細胞內(nèi)體或細胞膜的囊泡結(jié)構(gòu)，包括外泌體、微泡等，統(tǒng)稱為細胞外囊泡。細胞外囊泡是細胞間信號溝通的一種重要模式，介導了蛋白質(zhì)，脂質(zhì)，RNA等活性大分子在細胞間的傳遞。
文章信息
- 文獻標題：Challenges and directions in studying cell–cell communication by extracellular vesicles
- Doi：https://doi.org/10.1038/s41580-022-00460-3
- 發(fā)表時間：Published: 08 March 2022
- 作者：Guillaume van Niel 和Pieter Vader
我的問題
- 細胞分泌外泌體是否隨機？
- 分泌出去的外泌體的靶向受體細胞是否隨機？
- 外泌體介導的細胞通訊與其他方式的細胞通訊有何不同？
- 外泌體運輸途徑有哪些？
Extracellular vesicle biogenesis
EV由通過多種機制產(chǎn)生的異質(zhì)膜泡組成。EV的兩個主要類型為：ectosomes和exosomes
- ectosomes：包括oncosomes，microvesicles（在質(zhì)膜上向外出芽產(chǎn)生的微囊泡）
- exosomes：在細胞內(nèi)產(chǎn)生，在內(nèi)吞途徑中，通過內(nèi)吞體膜向內(nèi)出芽，導致形成內(nèi)吞體腔內(nèi)包含的非常小的囊泡狀結(jié)構(gòu)
關于EVs的生成涉及到的方面有以下幾點值得關注：
- EV subtypes的區(qū)分
- 生物發(fā)生機制、EV亞型及其內(nèi)含物的多樣性
- EV分泌調(diào)節(jié)
- 生理背景下的EV生物發(fā)生
EV的多種產(chǎn)生機制：
不同的細胞外囊泡亞型以及各自的特征：可以看到這里主要的區(qū)別手段是size與marker不同
Box 1 | EV 生成: 關鍵問題與挑戰(zhàn)
How do we consider the whole complexity of the cell, including regulation of intracellular trafficking and cell metabolism in the study of extracellular vesicle (ev) biogenesis?
since ev biogenesis is also dependent on interaction with neighbouring cells and matrix in vivo,to which extent doe sthe ‘EV secretome’ change depending on environmental cues?
are distinct subsets of exosomes with different functions associated with multivesicular endosome (Mve) subpopulations?
what are the processes that turn subpopulations of Mves into secretory organelles?
How do chemical parameters, such as pericellular pH, concentration of reactive oxygen species and osmotic pressure, as well as physical constrains of the tissue, such as mechanical pressure due to cell density or stiffening extracellular matrix, affect intraluminal vesicle generation and secretion and plasma membrane budding?
Are processes described in vitro relevantin vivo?
From a more practical perspective, when aiming to interfere with ev biogenesis, how can we consider the complexity and diversity of the biogenesis of subpopulations of evs as well as the cell types, culture conditions and level of expression of ev cargoes? For instance, a given pathway, such as ceramide production, may inhibit exosome secretion of one subtype but not of others, while simultaneously affecting other regulatory processes in the cell. Moreover, if the inhibition or impairment of a specific process affects Mve biogenesis, given that not all Mves are secretory, new approaches are needed to clearly distinguish correlation and causality of the importance of the given process during exosome secretion.
The dynamics in extracellular space
EV可以在細胞之間以自分泌、旁分泌或內(nèi)分泌分泌的方式進行交換。ev介導局部和遠處細胞間通信能力的關鍵是它們在大多數(shù)細胞嵌入的細胞胞外和細胞外基質(zhì)中導航的能力
這個交流方式有以下幾點可以關注：
- EVs釋放到胞外的過程
- EVs攜帶的cargos
- EV 在體內(nèi)的分布情況
這里補充一個知識點：（《細胞生物學》第三版 翟中和）
細胞通訊：
細胞通訊是指一個細胞發(fā)出的信息通過介質(zhì)(又稱為配體)傳遞到另一個細胞并與靶細胞相應的受體相互作用，然后通過細胞信號轉(zhuǎn)導產(chǎn)生細胞內(nèi)一系列生理生化變化，最終表現(xiàn)為細胞整體的生物學效應的過程。細胞信號轉(zhuǎn)導是細胞間實現(xiàn)通訊的關鍵過程，對于多細胞生物細胞間功能的協(xié)調(diào)、控制細胞的生長和分裂、組織發(fā)生與形態(tài)建成是必需的。
細胞通訊的方式，可以分為三種：
- 細胞通過分泌化學信號進行細胞間通訊，這是多細胞生物普遍采用的通訊方式(圖A-D)
- 細胞間接觸依賴性的通訊，細胞間直接接觸，通過與質(zhì)膜結(jié)合的信號分子影響其他細胞(圖E)
- 動物相鄰細胞間形成間隙鏈接，植物細胞間通過胞間連絲是細胞間相互溝通
其中，自分泌方式一般是病理性質(zhì)的，多見于腫瘤細胞自己分泌刺激因子促進自身分裂增殖
外泌體的交流方式：
Box 2 | 胞外空間的動態(tài)性: 關鍵問題與挑戰(zhàn)
what is the interrelationship between extracellular vesicles (evs) and the extracellular matrix?
are all evs capable of crossing all basement membranes and, if not, is there tissue subpopulation specificity?
Given the importance of the extracellular matrix in the maintenance of normal tissue function, how do mechanical forces and the local matrix composition influence ev–extracellular matrix interaction?
to what extent does the composition of the extracellular matrix modulate the composition, and hence function, of evs?
what types of evs interact with the extracellular matrix, and is release of specific subpopulations into the extracellular matrix directly dependent on plasma membrane–matrix interactions and the associated mechanical forces?
Do evs carry components/properties that allow them to resist degradation extracellularly and to avoid undesirable interactions with non-target cells, matrix constituents and other interstitial factors?
How important are the biophysical properties of evs (for example, their size and compressibility) in traversing through the complex extracellular microenvironment?
after traversing the extracellular matrix, evs, or at least a subpopulation thereof, appear to have the capacity to cross several biological barriers. is this capability influenced by specific pathological situations (for example, the increase in vascular permeability)?
Do specific cell types interact with evs more efficiently, and does this interaction differ between different ev subpopulations?
Most of our understanding ofthe fate of EVsin vivo comesfrom studies using exogenously administered evs. However, ev isolation, storage, method of formulation and labelling may affect their targeting specificity and ultimate fate. thus, are the results obtained using exogenously administered evs representative of the physiological fate of endogenously generated evs?
Multiple approaches have been used to assessthe biodistribution of EVs in vivo, including fluorescent labelling of lipids and proteins, immunofluorescence, bioluminescence, Pet, sPeCt, Mri and Ct imaging59. all of these approaches have limitations in tracking the fate of evs, and novel approaches with large dynamic ranges of both temporal and spatial resolution are required to overcome these.
Functional delivery of extracellular vesicle cargo
很多研究都觀察到不同細胞類型對EV的攝取現(xiàn)象，EV攝取可以被視為一系列的步驟（圖2，5-9），但引導EV進入受體細胞的過程目前尚不清楚，以下幾點值得關注：
- EV 與細胞表面的作用
- 進入細胞的途徑
- EV胞內(nèi)的運輸與傳遞
- 細胞與細胞間通過EVs通訊
假設這下面兩個人是兩個細胞，中間的是細胞外囊泡，那兩個細胞的EV交流方式是不是就像下面這樣口若懸河滔滔不絕？
Box 3 | EV cargo的攝取與功能傳遞: 關鍵問題與挑戰(zhàn)
- which extracellular vesicle (ev)-associated factors are critical for dictating function (defined by signal-induction and/or cell entry)?
- Can we define the rules that govern ev targeting, and can we manipulate this knowledge in future translational studies using ev-based medicines?
- to what extent is the nature of the protein corona controlled by the native ev composition and how important is the corona in determining interactions with recipient cells or whole systems?
- How do we overcome the technical challenge of small ev size and scarcity of cargo, posing issues on directimaging of functional delivery of cargo by native EVs in vivo?
- are different ev subpopulations processed differently in recipient cells and do they exert different cellular functions? Can this heterogeneity be addressed by studying ev subpopulations individually, or do they cooperate in a synergistic manner?
- How do we provide direct evidence that observed physiological effects are truly ev mediated and, if so, what ev cargoes are responsible? in this regard, an overlooked aspect is the relative contribution of evs compared to other communication means such as cell–cell contact, nanotubes orsoluble factorslike cytokines or extracellular rNa.
- when attempting to dissect the relative potency of evs in directing cell communication from other secretome constituents, how important are the different non-vesicular secreted factors, such as extracellular matrix proteins and cytokines, in co-operation with evs in dictating the final and complex cellular response?
未來的研究方向
- Technical challenges
- Standardization of research
- Applications and translational opportunities
厲害的文章必有大牛：
- 自 1998 年以來，Guillaume van Niel 一直在研究外泌體及其起源區(qū)室、多泡體。
- 在 Necker 研究所（法國巴黎）攻讀博士學位期間，他報告并研究了腸上皮細胞分泌的外泌體的分泌和功能。
- 2003 年，他在烏得勒支內(nèi)側(cè)中心（荷蘭烏得勒支）展示了 MHC II 分子的泛素化，這是一種用于分選樹突細胞中多泡體的關鍵翻譯后修飾。
- 2005 年，他加入居里研究所（法國巴黎），并于 2008 年在該團隊獲得 CNRS 永久職位，以研究色素細胞中多泡體的生物發(fā)生。他特別報道了腔內(nèi)囊泡在生理淀粉樣蛋白原纖維生成中的作用。
- 自 2017 年以來，他擔任巴黎精神病學和神經(jīng)科學研究所（法國巴黎）的團隊負責人，開發(fā)新工具來可視化外泌體，尤其是在體內(nèi)，并了解內(nèi)體動力學在淀粉樣蛋白相關病理（阿爾茨海默病和膠質(zhì)母細胞瘤發(fā)展等神經(jīng)病）中降解和分泌之間的作用。
- 他在外泌體的細胞生物學方面擁有豐富的專業(yè)知識，并使用廣泛不同的成像技術，其中包括電子顯微鏡。
另外一個大佬：https://www.sluijterlab.com/dr-pieter-vader
