Arvanitis D, Polak P E, Szuchet S
Department of Pathology, Aghia Sophia Children's Hospital, Athens, Greece.
Dev Neurosci. 1992;14(5-6):313-27. doi: 10.1159/000111678.
The issue of the capacity of mature oligodendrocytes to remyelinate naked axons has not been totally resolved. The impression is that for this to happen, oligodendrocytes have to undergo cell division. We are interested in providing an answer to the question: can oligodendrocytes myelinate more than once? To address this question, we are using a model system consisting of pure cultures of postmyelination oligodendrocytes. We have previously shown that these cells have plasticity and are able to regenerate, but for this to occur they need a signal. In vitro, this signal is provided by interaction with a positively charged substratum and a serum factor(s). Over time in culture, without cell division, oligodendrocytes assemble multilamellar structures that ultrastructurally resemble myelin. We have named this process myelin palingenesis--rebirth--to distinguish it from remyelination. In order to ascertain the significance of the regenerative process observed in vitro and its predictive value as to the capabilities of oligodendrocytes to ensheathe axons, we undertook an ultrastructural and immunocytochemical characterization of the multilamellar membranes to assess whether they contain all the myelin-characteristic proteins, i.e., myelin basic protein, proteolipid protein, 2',3'-cyclic nucleotide 3'-phosphodiesterase and myelin-associated glycoprotein. We have used antibodies against these proteins as immunocytochemical probes in conjunction with the immunogold method at the electron microscopic level. Oligodendrocyte cultures were processed for electron microscopy. Blocks were serially sectioned parallel to the culture plate at 0.09-micron spacings. Staining of cells was done prior to embedding. Analysis of these micrographs brought to light the existence of membrane-membrane interaction between multilamellar structures; this is reminiscent of the interactions observed in situ between myelinated axons. We have found that the membranous structures possess all the myelin-characteristic proteins. Furthermore, based on the accessibility of these proteins to the antibodies, e.g., whether or not permeabilization was required, we can surmise that these proteins are incorporated into the membranous structures with the same orientation as in myelin. These results, in conjunction with our earlier work, show that mature oligodendrocytes stripped of their myelin are able to regenerate and reassemble multilamellar membranes that have all the myelin proteins. It remains to be proven that when provided with axons, these oligodendrocytes will generate typical myelin.
成熟少突胶质细胞对裸露轴突进行髓鞘再生的能力问题尚未完全解决。目前的印象是，要实现这一点，少突胶质细胞必须进行细胞分裂。我们感兴趣的是回答这个问题：少突胶质细胞能否进行多次髓鞘形成？为了解决这个问题，我们正在使用一个由髓鞘形成后少突胶质细胞的纯培养物组成的模型系统。我们之前已经表明，这些细胞具有可塑性并且能够再生，但要实现这一点它们需要一个信号。在体外，这个信号由与带正电荷的基质和一种血清因子的相互作用提供。在培养过程中，少突胶质细胞在不进行细胞分裂的情况下组装出超微结构类似于髓磷脂的多层结构。我们将这个过程命名为髓鞘再生——重生——以将其与髓鞘再生区分开来。为了确定在体外观察到的再生过程的意义及其对少突胶质细胞包裹轴突能力的预测价值，我们对多层膜进行了超微结构和免疫细胞化学表征，以评估它们是否包含所有髓鞘特征性蛋白质，即髓鞘碱性蛋白、蛋白脂蛋白、2',3'-环核苷酸3'-磷酸二酯酶和髓鞘相关糖蛋白。我们使用针对这些蛋白质的抗体作为免疫细胞化学探针，并结合电子显微镜水平的免疫金方法。对少突胶质细胞培养物进行电子显微镜处理。将包埋块平行于培养板以0.09微米的间距连续切片。在包埋前对细胞进行染色。对这些显微照片的分析揭示了多层结构之间存在膜-膜相互作用；这让人想起在有髓轴突原位观察到的相互作用。我们发现这些膜结构拥有所有髓鞘特征性蛋白质。此外，基于这些蛋白质对抗体的可及性，例如是否需要通透处理，我们可以推测这些蛋白质以与髓鞘中相同的方向整合到膜结构中。这些结果，结合我们早期的工作，表明脱髓鞘的成熟少突胶质细胞能够再生并重新组装具有所有髓鞘蛋白的多层膜。有待证明的是，当有轴突存在时，这些少突胶质细胞是否会产生典型的髓鞘。
