³ú¿Í ô¼ö¸¦ Æ÷ÇÔÇÏ´Â ÁßÃ߽Űæ°è¿¡´Â ÁÖ·Î ´Ù¾çÇÑ Å¸ÀÔµéÀÇ ½Å°æ¼¼Æ÷¿Í ¾Æ±³¼¼Æ÷·Î ºÐ·ùµÇ´Â ¼º»ó¼¼Æ÷(astrocytes), ¹Ì¼¼¾Æ±³¼¼Æ÷(microglia), Èñµ¹±â±³¼¼Æ÷(oligodendrocytes)·Î ±¸¼ºµÇ¾î ÀÖÀ¸¸ç, ±× ¹Û¿¡ ³»ÇǼ¼Æ÷, Ç÷°üÁÖÀ§¼¼Æ÷, Ç÷°ü-³ú À庮À» Åë°úÇÑ ¸é¿ª¼¼Æ÷µéÀÌ Á¸ÀçÇÑ´Ù. ÀÌ Áß¿¡¼ °¡Àå ÁÖ¿äÇÑ Ç÷¹À̾îÀÎ ½Å°æ¼¼Æ÷´Â È°µ¿ÀüÀ§(action potential) »ý¼º°ú ÀüÆÄ ¹× ½Ã³À½º Àü´ÞÀ» ÅëÇØ ½Å°æ½ÅÈ£¸¦ Àü´ÞÇÏ´Â ÇÙ½ÉÀûÀÎ ¿ªÇÒÀ» ÇÑ´Ù. ¹ß±îÁö À̾îÁö´Â ¿îµ¿½Å°æ¼¼Æ÷µéÀº ÀÏÂ÷ ¿îµ¿ÇÇÁú(primary motor cortex)¿¡¼ ½ÃÀÛÇØ Ã´¼ö±îÁö À̾îÁö´Â »óÀ§¿îµ¿½Å°æ°ú, ô¼ö¿¡¼ ½Ã³À½º¸¦ ÅëÇؽÅÈ£¸¦ ¹Þ¾Æ ±ÙÀ°±îÁö È°µ¿ÀüÀ§¸¦ Àü´ÞÇÏ´Â ÇÏÀ§¿îµ¿½Å°æÀ¸·Î ±¸¼ºµÇ¾îÀÖ´Ù. 1 ¹ÌÅÍ ÀÌ»ó Àü´ÞµÇ¾î¾ß ÇÏ´Â È°µ¿ÀüÀ§ ¼Óµµ´Â ¾à 50 m/s À̸ç, À̸¦ ¼ºÃëÇϱâ À§ÇÑ ¿¡³ÊÁöµµ ÀûÁö ¾Ê°Ô ¿ä±¸µÈ´Ù [1, 2]. È°µ¿ÀüÀ§°¡ ÀÌ·¸°Ô ºü¸£°í ¼±¸íÇÏ°Ô Á¦ ±â´ÉÀ» Çϱâ À§Çؼ´Â ½Å°æ¼¼Æ÷µµ °Ç°ÇØ¾ß ÇÏÁö¸¸, ºñ½Å°æ¼¼Æ÷µéÀÇ ½Å°æº¸È£ ±â´É°ú ¿¡³ÊÁö ¼Ò½º °ø±Þ ±â´ÉµéÀÌ ÇʼöÀûÀÌ´Ù.
½Å°æÅðÇà Áúȯ¿¡¼´Â Á¶Á÷ ¼öÁØ¿¡¼ ³ú ¹× ô¼öÀÇ À§Ãà, ¼¼Æ÷ ¼öÁØ¿¡¼ ´Ü¹éÁú ÀÀÁý°ú ½Å°æ¼¼Æ÷ »ç¸êÀ» ³ªÅ¸³½´Ù [3]. ½Å°æÅðÇàÀº ½Å°æ¼¼Æ÷ ÀÌ»óÀ̳ª ºñ½Å°æ¼¼Æ÷ÀÇ ½Å°æ¿°Áõ¿¡¼ À¯·¡µÇ¸ç, ½Å°æÈ°¼º¿¡ ¿µÇâÀ» ÁØ´Ù. ½Å°æÅðÇà Á¶°ÇµéÀÌ ½Å°æ¼¼Æ÷¸¦ °úÈ°¼ºÈ(hyperexcitability or hyperactivity) ½Ãų ¶§ ºÒÇÊ¿äÇÑ ½Å°æÀÌ»ó ¹ÝÀÀ µîÀÌ ³ªÅ¸³¯ ¼ö ÀÖ´Ù. ¹Ý´ë·Î ½Å°æÀÌ ÀúÈ°¼ºÈ ȤÀº Á×°Ô µÈ´Ù¸é ½Å°æ Àü´Þ ±â´ÉÀÌ ¸ØÃçÁö°Å³ª Áö¿¬µÉ °ÍÀÌ´Ù. ÀÌ·¯ÇÑ Àü±â»ý¸®½ÅÈ£ÀÇ ÀÌ»óÀº ±â´ÉÀûÀÎ ¹ÙÀÌ¿À¸¶Ä¿(functional biomarker)·Î¼ ·ç°Ô¸¯º´°ú ¾ËÃ÷ÇÏÀ̸Ӻ´À» ºñ·ÔÇÑ ½Å°æÅðÇà ȯÀÚµé°ú ½Å°æÅðÇà ½ÇÇè ¸ðµ¨µ¿¹°¿¡¼ ¸¹ÀÌ º¸°í µÇ°í ÀÖ´Ù [4,5,6]. ƯÈ÷ ½Å°æ °úÈ°¼ºÈ´Â ·ç°Ô¸¯º´À̳ª ¾ËÃ÷ÇÏÀ̸Ӻ´¿¡¼ Áúº´ÀÇ Ãʱ⿡ ³ªÅ¸³ª±â ¶§¹®¿¡ Áø´ÜÀ¸·Îµµ È°¿ëµÇ°í ÀÖ´Ù [17]. ÀÌ·¯ÇÑ ºñÁ¤»óÀû ½Å°æÈ°¼ºÀº ½Å°æÅðÇà ÁúȯÀÇ °á°ú¹°ÀÌÁö¸¸, ±× ÀÚü·Î ½Å°æÅðÇà Áúȯ ÁøÇàÀ» °¡¼ÓȽÃÅ°´Â µî ºÎÁ¤Àû ¿µÇâÀ» ÁÙ ¼ö ÀÖ´Ù (±×¸² 1). ÀÌ·¯ÇÑ °æ¿ì ºñÁ¤»óÀû ½Å°æÈ°¼ºÀ» Á¤»óȽÃÅ°´Â ¹æ¹ýÀº Ä¡·áÁ¦ °³¹ßÀÇ ±âȸ°¡ µÉ ¼ö ÀÖ´Ù. º» ±Û¿¡¼´Â ·ç°Ô¸¯º´°ú ¾ËÃ÷ÇÏÀ̸Ӻ´ Áß½ÉÀ¸·Î ½Å°æÀÇ È°¼ºÀÌ Áø´Ü ¹× ±â´ÉÀû ¹ÙÀÌ¿À¸¶Ä¿·Î »ç¿ëµÉ ¼ö ÀÖ´ÂÁö, ºñÁ¤»óÀû ½Å°æÈ°¼ºÀÇ Á¶ÀýÀÌ °ú¿¬ Ä¡·áÁ¦·Î »ç¿ëµÉ ¼ö ÀÖ´ÂÁö¿¡ °üÇÑ ¿¬±¸µéÀ» ¼Ò°³ÇÏ°íÀÚ ÇÑ´Ù.
½Å°æÀÇ Àü±â»ý¸® È°¼ºÀº È°µ¿ÀüÀ§¿Í ¸·ÀüÀ§ÀÇ Áøµ¿À» ÃøÁ¤ÇÔÀ¸·Î½á ÆÇ´ÜÇÒ ¼ö ÀÖ´Ù. ÀÌ·¯ÇÑ ÃøÁ¤Àº ½ÇÇèÀÇ ¸ñÀû¿¡ µû¶ó ÀÓ»ó, ºñÀÓ»ó (in vivo ¹× ex vivo), in vitro ÀÇ ¿©·¯ ·¹º§¿¡¼ ¼öÇàµÈ´Ù [7]. ¿ÜºÎ ÀÚ±ØÀ» ÁÖÁö ¾ÊÀ¸¸é ÀÚ¹ßÀû È°¼º(spontaneous firing) Á¤º¸¸¦ ¾òÀ» ¼ö ÀÖÀ¸¸ç, ¿ÜºÎÀÚ±ØÀ¸·Î À¯¹ßÀû È°¼º(evoked firing) Á¤º¸¸¦ ¾òÀ» ¼ö ÀÖ´Ù. ÀÌ·¯ÇÑ Á¤º¸¸¦ ¾ò´Â ¹æ¹ýÀ¸·Î ¼ö¼úÀÌ ÇÊ¿ä¾ø´Â EEG (Electroencephalography) ¹× EMG (Electromyography) µîÀÌ ÀÖ°í, ºñÀÓ»ó¿¡¼ ¼ö¼úÀ» ÅëÇØ Àü±Ø¹Ù´ÃÀ̳ª ´ÙÁßÀü±Ø(multielectrode)À» »ðÀÔÇÏ´Â ¹æ¹ýµéÀ» »ç¿ëÇÒ ¼ö ÀÖ´Ù. In vitro ¼öÁØ¿¡¼´Â ÆÖġŬ·¥ÇÁ¿Í MEA(multielectrode array)¸¦ ÁÖ·Î »ç¿ëÇÑ´Ù [7]. ÀÌ¿Ü¿¡µµ ºñÀÓ»ó ¹× in vitro¿¡¼´Â Ä®½· Ç¥ÁöÀÚ¿Í Àü¾Ð Ç¥ÁöÀÚ µîÀÌ »ç¿ëµÇ°í ÀÖ´Ù [8].
´ÜÀÏ È°µ¿ÀüÀ§°¡ ÃøÁ¤µÈ °æ¿ì Àü¾ÐÀÇ ¼¼±â¿Í ¼Óµµ°¡ ÁÖ¿ä Á¤º¸°¡ µÈ´Ù. º¹¼ö È°µ¿ÀüÀ§°¡ ÃøÁ¤µÈ °æ¿ì È°µ¿ÀüÀ§ÀÇ °¹¼ö¿Í ºóµµ ¹× ÆÐÅÏÀÌ ÁÖ¿ä Á¤º¸°¡ µÉ °ÍÀÌ´Ù (±×¸² 2). ³×Æ®¿öÅ©¸¦ Çü¼ºÇÏ´Â ¿©·¯ ½Å°æ¼¼Æ÷°¡ µ¿½Ã¿¡ ÃøÁ¤µÈ °æ¿ì È°µ¿ÀüÀ§°¡ µ¿½Ã¿¡ ÀϾ´ÂÁö(synchronization)°¡ Áß¿äÇÑ Á¤º¸°¡ µÉ °ÍÀÌ´Ù. È°µ¿ÀüÀ§°¡ ¾Æ´Ï´õ¶óµµ ¸·ÀüÀ§ Áøµ¿Àº Áß¿äÇÑ Á¤º¸¸¦ Á¦°øÇϴµ¥, ÀÌ´Â ½Ã³À½ºÈÄ ÀüÀ§°ú ½Å°æ¼¼Æ÷ ÀÚüÀû Ư¡À» ¹Ý¿µÇÏ°í, È°µ¿ÀüÀ§ »ý¼º ¹× synchronization¿¡ ¹ÐÁ¢ÇÏ°Ô ¿¬°üµÇ¾î ÀÖ´Ù. ¸·ÀüÀ§ Áøµ¿Àº ÃøÁ¤µÇ´Â ÁÖÆļö¿¡ µû¶ó¼ ¾ËÆÄ(8-15Hz), º£Å¸(16-31Hz), °¨¸¶(30-100Hz), µ¨Å¸(<4Hz), ¼¼Å¸(4-8Hz) µîÀ¸·Î ºÐ·ùµÈ´Ù.
½Å°æÅðÇàÁúȯ¿¡¼ À¯ÀÇÇÏ°Ô º¯È¸¦ ³ªÅ¸³Â´ø ¿ä¼ÒµéÀº ÁÖ·Î (1) ½Å°æÈ°¼ºÀÇ ¿ªÄ¡, (2) ½Å°æÈ°¼ºÀÇ ¼¼±â, (3) ½Å°æÈ°¼ºÀÇ ¼Óµµ, (4) ÈïºÐ¼º ¹× ¾ïÁ¦¼º ½ÅÈ£ ±ÕÇü, (5) synchronization µîÀÇ ³×Æ®¿öÅ© È°¼º, (6) ¸·ÀüÀ§ Áøµ¿ µîÀÌ´Ù. ÀÌ·¯ÇÑ º¯È´Â ½Å°æ¼¼Æ÷ ÀÚü(intrinsic excitability) ¹× ½Å°æ³×Æ®¿öÅ©¿¡¼ÀÇ ÀÌ»ó »Ó ¾Æ´Ï¶ó ºñ½Å°æ¼¼Æ÷ÀÇ º´¸®¿¡¼ À¯·¡µÉ ¼ö ÀÖ´Ù (±×¸² 1). ´ëÇ¥ÀûÀÎ ¿¹·Î ½Å°æÀÇ Ãà»èµ¹±â¸¦ °¨½Î´Â ¼öÃÊÈ(myelination)´Â È°µ¿ÀüÀ§ ¼Óµµ¿¡ Áß¿äÇѵ¥, Èñµ¹±â±³¼¼Æ÷¿¡ ÀÇÇØ Çü¼ºµÈ´Ù. Èñµ¹±â±³¼¼Æ÷¿¡ ÀÌ»óÀÌ »ý±â¸é ¼öÃÊÈ ¹× ½Å°æ¼¼Æ÷·Î ¿¡³ÊÁö °ø±ÞÀÌ º¯ÈµÇ¾î È°µ¿ÀüÀ§ÀÇ ¼Óµµ ¹× ¼¼±â°¡ ´Þ¶óÁú °ÍÀÌ´Ù [9]. ¶ÇÇÑ ¼º»ó¼¼Æ÷´Â ¹æÃâµÈ ±Û·çŸ¸ÞÀÌÆ®¸¦ ÀçÈí¼öÇϴµ¥ Áß¿äÇѵ¥, ±Û·çŸ¸ÞÀÌÆ®´Â ½Å°æÈ°¼º¿¡ ¿µÇâÀ» ÁÖ¸ç, ¹®Á¦°¡ »ý±æ°æ¿ì ½Å°æ°úÈ°¼º¿¡ ¿µÇâÀ» ÁÙ ¼ö ÀÖ´Ù [10, 11].
ȯÀÚÀÇ ¿îµ¿½Å°æ È°¼ºÀº Transcranial magnetic stimulation (TMS)·Î ³úÀÇ »óÀ§¿îµ¿½Å°æÀ» ºñ¿Ü°úÀûÀ¸·Î ÀÚ±ØÇÑ ÈÄ ±ÙÀ°ÀÇ Àü¾ÐÀ» ÃøÁ¤ÇÏ¿© ¾ò¾îÁø´Ù. Threshold trackingÀº ÀÏÁ¤ÇÑ ¼¼±âÀÇ ¹ÝÀÀ(mV)À» ³ªÅ¸³»´Â ¿ªÄ¡(mA)¸¦ ÃøÁ¤ÇÏ´Â ±â¼úÀε¥, ÀÌ ±â¼úÀÇ °³¹ß·Î µ¥ÀÌŸº¯µ¿¼ºÀÌ °¨¼ÒµÇ¾ú´Ù. ÀÌ µÎ ±â¼úÀÇ ¹ßÀüÀÌ ·ç°Ô¸¯º´¿¡¼ ½Å°æ °úÈ°¼ºÈ¸¦ ±Ô¸íÇϴµ¥ ±â¿©ÇÏ¿´´Ù [12]. ·ç°Ô¸¯º´ ȯÀÚµéÀº Áúº´ Ãʱ⠴ܰ迡¼ »óÀ§¿îµ¿½Å°æ °úÈ°¼ºÈ¸¦ ³ªÅ¸³½´Ù [13]. Áï Ãʱ⠷ç°Ô¸¯º´ ȯÀÚ´Â ÀϹÝÀΰú ºñ±³ÇÏ¿© °°Àº ¼¼±âÀÇ È°µ¿ÀüÀ§¿¡ µµ´ÞÇϱâ À§ÇØ ´õ ÀûÀº ÀÚ±ØÀÌ ÇÊ¿äÇÏ´Ù. Short interval intracortical inhibition (SICI)´Â 7~10ÃÊ °£°ÝÀ¸·Î µÎ °³ÀÇ ÀÚ±ØÀ» ÁÙ ¶§, µÎ¹ø° ½ÅÈ£¿¡¼ ƯÁ¤ ¼¼±â¿¡ µµ´ÞÇϱâ À§ÇÑ ÀÚ±ØÀÇ ¼¼±âÀε¥, ÀÌ´Â ¾ïÁ¦¼º ½Å°æ¼¼Æ÷ È°¼ºÀ» ¹Ý¿µÇÑ´Ù. Ãʱ⠷ç°Ô¸¯º´ ȯÀÚ´Â SICI¿¡¼ ´õ ÀûÀº ÀÚ±ØÀÌ ÇÊ¿äÇϹǷÎ, °¨¼ÒµÈ ¾ïÁ¦¼º ½Å°æ¼¼Æ÷ È°¼ºÀ¸·Î ÀÎÇÑ °úÈïºÐ¼ºÀÌ ÀÖ´Ù°í ÃßÁ¤ÇÒ ¼ö ÀÖ´Ù. ·ç°Ô¸¯º´¿¡¼ SICI°¡ Áß¿äÇÑ ÀÌÀ¯´Â ȯÀÚÀÇ Áúº´ ÁøÇà ¹× ¼ö¸í°ú »ó°ü°ü°è¸¦ ³ªÅ¸³Â±â ¶§¹®ÀÌ´Ù [11, 14]. µû¶ó¼ ½Å°æ°úÈ°¼ºÀ» ³·Ãß´Â ¾à¹°À» Å×½ºÆ®ÇÏ´Â ÀÓ»ó½ÇÇè¿¡¼ SICI´Â ÀÏÂ÷Á¾°áÁ¡(primary end point)·Î »ç¿ëµÇ°í ÀÖ´Ù [15, 16].
½Å°æ°úÈ°¼ºÀº Áúº´ Ãʱ⠴ܰ迡 ³ªÅ¸³ª¹Ç·Î Áø´ÜÀ¸·Î¼ À¯¿ëÇѵ¥, ·ç°Ô¸¯º´ ÀÓ»ó Áø´Ü¿¡¼ ½Å°æÈ°¼º ÃøÁ¤À» Æ÷ÇÔÇÒ ¶§ Áø´ÜÀ» ´õ Á¤È®ÇÏ°Ô ÇÒ ¼ö ÀÖ´Ù [17]. ±×·³¿¡µµ ºÒ±¸ÇÏ°í ·ç°Ô¸¯º´¿¡¼ ½Å°æÈ°¼ºÀÇ º¯È¸¦ ÁÖÀDZí°Ô Çؼ®ÇØ¾ß ÇÑ´Ù. ±× ÀÌÀ¯´Â ·ç°Ô¸¯º´ Ãʱ⿡ ½Å°æ°úÈ°¼ºÀ» ³ªÅ¸³»´õ¶óµµ Áúº´ÀÌ ÁøÇàµÊ¿¡ µû¶ó °á±¹ ÀúÈ°¼º ¹× ºñÈ°¼ºÀÌ °üÂûµÈ´Ù´Â Á¡ÀÌ´Ù. ÀÌ·¯ÇÑ Á¡À» ¹Ý¿µÇÏ¿´À» ¶§ Áø´Ü ÀÓ»ó½ÇÇè¿¡¼ ½Å°æÈ°¼ºÀº 73%ÀÇ ¹Î°¨µµ¿Í 81%ÀÇ Æ¯À̵µ¸¦ ³ªÅ¸³»¾ú´Ù [18]. ·ç°Ô¸¯º´ ȯÀÚ iPSC ÇÏÀ§ ¿îµ¿½Å°æ¼¼Æ÷ ¹× ·ç°Ô¸¯º´ »ýÁ㠸𵨿¡¼µµ ½Å°æÈ°¼ºÀº ½Ã°£¿¡ µû¸¥ º¯È¸¦ ³ªÅ¸³»¾ú´Ù [19, 20]. ½Å°æÈ°¼º Çؼ®À» ÁÖÀÇÇØ¾ß ÇÏ´Â ¶Ç ´Ù¸¥ ÀÌÀ¯´Â ·ç°Ô¸¯º´ ȯÀÚµéÀÇ »óÀ§ ¿îµ¿½Å°æÀÇ °úÈ°¼º¿¡ °üÇÑ ÀÓ»ó°á°úµéÀº ¸¹ÀÌ ÃàôµÇ¾îÀÖÁö¸¸, ÇÏÀ§ ¿îµ¿½Å°æÀÇ °úÈ°¼º¿¡ °üÇؼ´Â ȯÀÚ iPSC ½Å°æ¼¼Æ÷¿Í »ýÁ㠸𵨠½Å°æ¼¼Æ÷¿¡¼ °á°úµéÀÌ ¾ù°¥¸®±â ¶§¹®ÀÌ´Ù [21, 22]. µû¶ó¼ ÇöÀç±îÁö´Â »óÀ§ ¿îµ¿½Å°æÀÇ °úÈ°¼ºÈ¸¦ È°¿ëÇÏ´Â °ÍÀÌ ÀûÀýÇÏ´Ù.
TMS¸¦ ÀÌ¿ëÇÏ¿© ÃøÁ¤ÇÑ »óÀ§ ¿îµ¿½Å°æÀÇ °úÈ°¼ºÀº ·ç°Ô¸¯º´ »Ó¸¸ ¾Æ´Ï¶ó FTD ¹× ¾ËÃ÷ÇÏÀÌ¸Ó È¯Àڵ鿡¼µµ ³ªÅ¸³´Ù [4, 5, 23]. ¾ËÃ÷ÇÏÀ̸Ӻ´ ȯÀÚ¸¦ ´ë»óÀ¸·Î ÇÑ PET ¹× MRI À̹Ì¡ ¿¬±¸¿¡¼ Áúº´ Ãʱ⿡ Çظ¶ÀÇ °úÈ°¼ºÈ¸¦ °üÂûÇÑ Á¡°ú ¾ËÃ÷ÇÏÀÌ¸Ó È¯ÀÚµéÀÌ °£ÁúÀ» ºó¹øÇÏ°Ô ¹ß»ýÇÏ´Â »ç½Çµµ ¿îµ¿½Å°æ Æ÷ÇÔÇÑ ¿©·¯ ³úºÎÀ§¿¡¼ °úµµÇÑ ½Å°æÈ°¼ºÀÌ ÀÖ´Ù´Â °ÍÀ» µÞ¹ÞħÇÑ´Ù [5]. ÃÖ±Ù »ýÁã¸ðµ¨À» ÀÌ¿ëÇÑ Àü±â»ý¸® ¿¬±¸¿¡¼ ¾ËÃ÷ÇÏÀ̸Ӻ´ º´¸®ÀÎ ¾Æ¹Ð·ÎÀÌµå º£Å¸, Ÿ¿ì, ¹× ½Å°æ¿°ÁõÀÌ ½Å°æÈ°¼º¿¡ ¿µÇâÀ» ¹ÌÃÆ´Ù°í ¹àÇû´Ù [24, 25, 26]. Ÿ¿ì ¹× ½Å°æ¿°ÁõÀº ÈïºÐ¼º ¹× ¾ïÁ¦¼º ½ÅÈ£ ±ÕÇüÀ» ÅëÇØ °úÈïºÐ¼º¿¡ ¿¬°üµÇ¾î ÀÖ¾ú°í, ¾Æ¹Ð·ÎÀÌµå º£Å¸´Â LTP ¹× LTD ±ÕÇü¿¡ ¿µÇâÀ» ¹ÌÃÆ´Ù.
¾ËÃ÷ÇÏÀ̸Ӻ´ ȯÀÚ¿¡¼´Â ·ç°Ô¸¯º´¿¡ ºñÇØ EEG¿Í MEG (Magnetoencephalography)À» ÀÌ¿ëÇÑ ³úÁøµ¿ ÃøÁ¤ ¿¬±¸°¡ ´õ ¸¹ÀÌ ÀÌ·ç¾îÁ³´Ù. ¾ËÃ÷ÇÏÀÌ¸Ó È¯ÀÚ¿¡¼ Àü¹ÝÀûÀ¸·Î ¹ß°ßµÇ´Â Ư¡Àº ¾ËÆÄ, º£Å¸, ¹× °¨¸¶ (8~100 Hz) µîÀÇ ºü¸¥ Áøµ¿µéÀÌ °¨¼ÒÇÏ°í ´À¸° Áøµ¿µéÀÌ Áõ°¡ÇÏ´Â °ÍÀÌ´Ù [27]. ÀÌ·¯ÇÑ Çö»óµéÀº ¾ËÃ÷ÇÏÀÌ¸Ó µ¿¹° ¸ðµ¨¿¡¼µµ ³ªÅ¸³µ´Âµ¥, ƯÈ÷ hAPPJ20 »ýÁã¿Í 5XFAD »ýÁãµéÀÌ °¨¸¶Áøµ¿¿¡¼ °¨¼Ò¸¦ ³ªÅ¸³Â´Ù [28, 29]. ÀÌ·¯ÇÑ Çö»óµéÀº ÀÓ»ó¿¡¼ ÀÎÁö °¨¼Ò³ª ¾Æ¹Ð·ÎÀÌµå º£Å¸ ȤÀº Ÿ¿ì µîÀÇ ¾ËÃ÷ÇÏÀ̸ÓÀÇ ´Ù¸¥ ÁöÇ¥µé°úµµ »ó°ü°ü°è¸¦ ³ªÅ¸³ÂÀ¸¸ç, °æµµÀÎÁöÀå¾Ö¿¡¼ ¾ËÃ÷ÇÏÀÌ¸Ó ÁúȯÀ¸·ÎÀÇ ÀüȯÀ» ¿¹ÃøÇÏ´Â ¸¶Ä¿·Î È°¿ëµÉ °ÍÀ¸·Î ±â´ëÇÏ°í ÀÖ´Ù [27].
·ç°Ô¸¯º´¿¡¼ »óÀ§¿îµ¿½Å°æÀÇ °úÈ°¼ºÀº Áúº´ÀÇ ¾ÇÈ¿Í °ü·ÃÀÖ´Ù. »óÀ§¿îµ¿½Å°æÀÌ ±Û·çŸ¸ÞÀÌÆ®¸¦ ºñÁ¤»óÀûÀ¸·Î ¹æÃâÇÏ¿© ÈïºÐµ¶¼º(excitotoxicity)À» ÅëÇØ ÇÏÀ§¿îµ¿½Å°æÀÇ ÅðÇàÀ» ÀÏÀ¸Å³ °ÍÀ̶ó´Â °¡¼³(dying forward mechanism)·Î À̸¦ µÞ¹ÞħÇÑ´Ù. ÀÌ·² °æ¿ì °úÈ°¼º ¹× ÈïºÐµ¶¼ºÀ» ¾ïÁ¦ÇÑ´Ù¸é Ä¡·áÁ¦°¡ µÉ ¼ö ÀÖ´Ù [30]. ·ç°Ô¸¯º´ Ä¡·áÁ¦·Î ½ÂÀÎµÈ RiluzoleÀº Na+ ÀÌ¿Âä³Î È°¼ºÀ» ÁÙÀÌ°í ±Û·çŸ¸ÞÀÌÆ® ¼ö¿ëü¸¦ ¾ïÁ¦ÇϹǷΠ½Å°æ°úÈ°¼º°ú ÈïºÐµ¶¼ºÀ» ³·Ãß´Â ÀÛ¿ëÀ» ÇÑ´Ù [15]. °úÈ°¼ºÀ» ³»´Â ·ç°Ô¸¯º´ ȯÀÚ iPSC À¯·¡ ¿îµ¿½Å°æ¿¡ K+ ÀÌ¿Âä³Î È°¼ºÁ¦ RetigabineÀ» ó¸®ÇßÀ» ¶§µµ, ½Å°æ°úÈ°¼ºÀ» ÁÙÀÌ´Â µ¿½Ã¿¡ ¿îµ¿½Å°æ¼¼Æ÷ÀÇ »ýÁ¸À» Áõ°¡½ÃÄ×´Ù. RetigabineÀº ÇöÀç ÀÓ»ó 2»ó¿¡¼µµ ¿îµ¿½Å°æÈ°¼ºÀ» ÁÙÀÌ´Â °ÍÀ¸·Î ¹àÇôÁ®¼ [16] iPSC À¯·¡ ¿îµ¿½Å°æ¿¡¼¿Í °°ÀÌ È¯ÀÚ ¿îµ¿½Å°æÀ» º¸È£ÇÒ °ÍÀ¸·Î ±â´ëµÈ´Ù. ±×·³¿¡µµ ºÒ±¸ÇÏ°í RiluzoleÀÌ ¼ö¸íÀ» 3-4 °³¿ù Á¤µµ ¿¬Àå½ÃÄÑÁÖ´Â ¹Ì¹ÌÇÑ È¿°ú¸¦ ³ªÅ¸³½ Á¡°ú [31], ÈïºÐµ¶¼º °¡¼³À» ±â¹ÝÀ¸·Î ÇÑ ´Ù¸¥ ¾à¹°µéµµ Àü¹ÝÀûÀ¸·Î ¼º°øÀûÀÎ °á°ú¸¦ º¸¿©ÁÖÁö ¸øÇÑ Á¡Àº ÀÌ·¯ÇÑ Á¢±Ù¹ýÀÇ Å« ¾àÁ¡ÀÌ´Ù. Retigabine ÀÓ»ó ½ÇÇèÀ» ÅëÇؼ K+ ÀÌ¿Âä³ÎÀ» Ç¥ÀûÇÏ´Â °ÍÀÌ RiluzoleÀ̳ª mexiletine °°ÀÌ Na+ ÀÌ¿Âä³ÎÀ» Ç¥ÀûÇÏ´Â °Íº¸´Ù °³¼±µÉ °á°ú¸¦ º¸¿©ÁÙ Áö´Â ÁöÄѺÁ¾ß ÇÒ °ÍÀÌ´Ù [16].
ÈïºÐµ¶¼º °¡¼³À» ±â¹ÝÀ¸·Î ÇÑ ¾ïÁ¦¼º ¾à¹° Ä¡·á ÀÌ¿Ü¿¡µµ ½Å°æÀ» ÀڱؽÃÅ´À¸·Î¼ Ä¡·áÈ¿°ú¸¦ ³»´Â Á¢±Ù¹ýµµ ½Å°æÅðÇàÁúȯ¿¡ Àû¿ëµÇ±â ½ÃÀÛÇß´Ù. À§¿¡¼ ¾ð±ÞÇßµíÀÌ ¾ËÃ÷ÇÏÀÌ¸Ó ¸ðµ¨ »ýÁã´Â °¨¸¶Áøµ¿¿¡¼ °¨¼Ò¸¦ ³ªÅ¸³Â´Ù. ±¤À¯ÀüÇÐ ±â¼úÀ» ÅëÇØ Çظ¶ ½Å°æ¼¼Æ÷¸¦ °¨¸¶Áøµ¿À» ÁÖ¾úÀ» ¶§ ¹Ì¼¼¾Æ±³¼¼Æ÷¸¦ ÅëÇØ ¾Æ¹Ð·ÎÀ̵å ÀÀÁýÀÌ °¨¼ÒÇÏ¿´´Ù [29]. ÀÌ·¯ÇÑ ¿¬±¸°á°ú¸¦ ȯÀÚ¿¡°Ô Àû¿ëÇϱâ À§ÇØ GENUS (Gamma ENtrainment Using Sensory stimuli) ÀåÄ¡°¡ °í¾ÈµÇ¾ú°í, °¨°¢±â°ü ÀÚ±ØÀ» ÅëÇØ ³ú°¨¸¶Áøµ¿À» ÀÏÀ¸ÄÑ Ä¡·áÈ¿°ú¸¦ ³»´Â °ÍÀ» ¸ñÇ¥·Î ÇÏ°íÀÖ´Ù (ÀÓ»ó½ÇÇè NCT04042922, NCT04055376) [32].
½Å°æ¼¼Æ÷ÀÇ ÀÚ±ØÀº Èñµ¹±â±³¼¼Æ÷¸¦ ÅëÇؼµµ Ä¡·á È¿°ú¸¦ ³¾ °¡´É¼ºÀÌ ÀÖ´Ù. »ýÁã¿¡¼ ±¤À¯ÀüÇÐÀ» ÀÌ¿ëÇÏ¿© ´ë³úÀÇ ¿îµ¿½Å°æ ºÎÀ§¸¦ ÀڱؽÃÄ×À» ¶§ ¼öÃÊȸ¦ Áõ°¡½ÃÄ×°í, ¿îµ¿±â´ÉÀ» Çâ»ó½ÃÄ×´Ù [33]. ÆÄŲ½¼º´ ȯÀÚ¸¦ ´ë»óÀ¸·Î ¿¬±¸ ÁßÀÎ Deep Brain Stimulation (DBS) ¹æ¹ýµµ ½Å°æ¼¼Æ÷¸¦ ÀÚ±ØÇÏ´Â ¹æ½ÄÀε¥, ÀáÀçÀû ¸ÞÄ«´ÏÁòÀ¸·Î¼ ³úÁøµ¿ Á¶ÀýÀ» Æ÷ÇÔÇÑ´Ù [34].
À§¿¡¼ ¼³¸íÇÑ Áõ°¡µÈ ½Å°æÈ°¼ºÀÇ ¾ïÁ¦³ª °¨¼ÒµÈ ½Å°æÈ°¼ºÀÇ ÀçÈ°¼ºÀº ¼·Î ¹èÄ¡µÇ´Â Á¢±Ù¹ýÀε¥, ÀÌ·¯ÇÑ »ç½ÇÀº ½Å°æ³×Æ®¿öÅ©°¡ µ¿ÀûÀÌ°í º¹ÀâÇÏ´Ù´Â »ç½ÇÀ» ¹Ý¿µÇÑ´Ù. ·ç°Ô¸¯º´À̳ª ¾ËÃ÷ÇÏÀ̸Ӻ´¿¡¼ Áõ°¡µÈ ¿îµ¿½Å°æÀÇ È°¼º Áõ°¡´Â ÈïºÐµ¶¼ºÀÇ ¿øÀÎÀ¸·Î¼ ÀÛ¿ëÇϱ⵵ ÇÏÁö¸¸, ½Å°æÈ°¼º Áõ°¡°¡ ¿îµ¿½Å°æ¼¼Æ÷ »ç¸êÀÇ ¿øÀÎÀÌ ¾Æ´Ï¸ç [35], ½Å°æ¼¼Æ÷°¡ ½ºÆ®·¹½º¿¡ ´ëÀÀÇÏ´Â ÀûÀÀÀû (adaptive) ¹ÝÀÀÀÏ ¼ö ÀÖ´Ù´Â ¿¬±¸°á°úµµ ÀÖ´Ù [36]. ½ÇÁ¦·Î AMPA¸¦ ·ç°Ô¸¯º´ ¸ðµ¨ »ýÁãÀÎ SOD1 G93A¿¡ Åõ¿©ÇØ ½Å°æÈ°¼ºÀ» Áõ°¡½ÃÄ×À» ¶§ ¼ö¸íÀÌ ¿¬ÀåµÇ¾ú°í ¹Ý´ë·Î AMPA ¼ö¿ëü¸¦ ¾ïÁ¦ÇÏ´Â CNQX¸¦ Åõ¿©ÇßÀ» ¶§ ¼ö¸íÀÌ °¨¼ÒÇÏ¿©¼, ½Å°æÈ°¼º Áõ°¡°¡ ½Å°æÅðÇà¿¡ À¯ÀÍÇÒ ¼ö ÀÖ´Â Áõ°Å¸¦ Á¦½ÃÇÏ¿´´Ù [37].
½Å°æÅðÇàÁúȯ Á¶°Ç¿¡¼ ½Å°æÈ°¼ºÀº º¯ÈÇϸç, Áúº´Ãʱ⿡ ¹ß»ýÇϱ⠶§¹®¿¡ ·ç°Ô¸¯º´À̳ª ¾ËÃ÷ÇÏÀ̸Ӻ´¿¡¼ Áø´ÜÀ¸·Î È°¿ëµÉ ¼ö ÀÖ´Ù. Áúº´ÀÇ Á¶±â Áø´Ü°ú ´ëó°¡ Áß¿äÇѵ¥ Àü±â»ý¸®ÃøÁ¤À» ÀÌ¿ëÇÑ Áø´ÜÀº PETÀ̳ª fMRI°ú ÇÔ²² Áß¿äÇÑ Áø´Üµµ±¸°¡ µÉ °ÍÀÌ´Ù. ÇÏÁö¸¸ ½Å°æÈ°¼ºÀÌ ¹ÙÀÌ¿À¸¶Ä¿·Î¼ ¾ÈÁ¤ÀûÀ¸·Î »ç¿ëµÇ¾îÁö±â À§Çؼ´Â ½ÇÇè ¹æ¹ý ¹× Á¶°ÇÀÇ Â÷ÀÌ¿¡¼ ¹ß»ýÇÏ´Â µ¥ÀÌÅͺ¯µ¿¼ºÀÌ ÁÙ¾îµé¾î¾ß ÇÑ´Ù. ¶ÇÇÑ, ´õ ¸¹Àº ȯÀÚ±º¿¡¼ °ËÁõµÈ ƯÀ̼º°ú ¹Î°¨¼º ¼öÁØÀÌ ¹àÇôÁ®¾ß ÇÏ¸ç ´Ù¸¥ ÀÓ»óÀû ÁöÇ¥µé°ú »óÈ£º¸¿ÏÀûÀ̾î¾ß ÇÒ °ÍÀÌ´Ù.
½Å°æÈ°¼ºÀ» °¨¼Ò½ÃÅ°µç Áõ°¡½ÃÅ°µç ½Å°æÀÇ ±â´ÉÀ» º¹¿øÇÏ¿© ½Å°æÅðÇàÁúȯ Ä¡·á È¿°ú¸¦ ³»·Á´Â ½Ãµµ´Â ÇöÀç ÀÓ»ó½ÇÇè Áß¿¡ ÀÖ´Ù. ½Å°æÈ°¼ºÀÇ Ç׻󼺰ú º¹ÀâÇÑ ³×Æ®¿öÅ© ¶§¹®¿¡ ½Å°æÅðÇàÁúȯ Á¶°ÇÀÌ ½Å°æ°è¿¡ ¹ÌÄ¡´Â ¿µÇâ¿¡ ´ëÇÑ ÀÌÇØ°¡ ´õ ÇÊ¿äÇÏÁö¸¸, ÀÌ¿Í µ¿½Ã¿¡ ½Å°æÀ» ºñ¿Ü°úÀûÀ¸·Î ƯÀÌÀû ºÎÀ§³ª ȸ·Î¸¦ Á¶ÀýÇÒ ¼ö ÀÖ´Â ±â¼úÀÌ °³¹ßµÈ´Ù¸é Ä¡·á¹æ¹ýÀ¸·Î¼ÀÇ ÀÀ¿ë¿¡ ÇÑ°ÉÀ½ ´õ °¡±îÀÌ °¡°Ô µÉ °ÍÀÌ´Ù.
º» ³»¿ëÀº Bristol Myers Squibb³ª ±× »óÇ°µéÀ» ´ëÇ¥ÇÏÁö ¾ÊÀ¸¸ç, Bristol Myers Squibb¿¡ Ãß±¸ÇÏ´Â ¸®¼Ä¡ ¹æÇâ°ú °ü·ÃÀÌ ¾ø½À´Ï´Ù.
S Chouhan. Normal Motor and Sensory Nerve Conduction Velocity of Radial Nerve in Young Adult Medical Students. J Clin Diagn Res (2016)
A Trevisiol et al. Monitoring ATP dynamics in electrically active white matter tracts. Elife (2017)
LJ Martin. Mitochondrial and Cell Death Mechanisms in Neurodegenerative Diseases. Pharmaceuticals (Basel) (2010)
RM Ahmed et al. Physiological changes in neurodegeneration - mechanistic insights and clinical utility. Nat Rev Neurol (2018)
S Tok et al. Functional Neurophysiological Biomarkers of Early-Stage Alzheimer's Disease: A Perspective of Network Hyperexcitability in Disease Progression. J Alzheimers Dis (2021)
W Huynh et al. Functional Biomarkers for Amyotrophic Lateral Sclerosis. Front Neurol (2019)
C Babiloni et al. What electrophysiology tells us about Alzheimer's disease: a window into the synchronization and connectivity of brain neurons. Neurobiol Aging (2020)
Yang HH, et al. Genetically Encoded Voltage Indicators: Opportunities and Challenges. J Neurosci (2016)
Yamazaki Y. Oligodendrocyte Physiology Modulating Axonal Excitability and Nerve Conduction. Adv Exp Med Biol (2019)
Pal B. Involvement of extrasynaptic glutamate in physiological and pathophysiological changes of neuronal excitability. Cell Mol Life Sci (2018)
ZI Gunes et al. Exciting Complexity: The Role of Motor Circuit Elements in ALS Pathophysiology. Front Neurosci (2020)
S Vucic et al. Cortical hyperexcitability: Diagnostic and pathogenic biomarker of ALS. Neurosci Lett (2021)
S Vucic et al. Utility of threshold tracking transcranial magnetic stimulation in ALS. Clin Neurophysiol Pract (2018)
K Shibuya et al. Motor cortical function determines prognosis in sporadic ALS. Neurology (2016)
N Geevasinga et al. Riluzole exerts transient modulating effects on cortical and axonal hyperexcitability in ALS. Amyotroph Lateral Scler Frontotemporal Degener (2016)
BJ Wainger et al. Effect of Ezogabine on Cortical and Spinal Motor Neuron Excitability in Amyotrophic Lateral Sclerosis: A Randomized Clinical Trial. JAMA Neurol (2021)
N Geevasinga et al. Diagnostic utility of cortical excitability studies in amyotrophic lateral sclerosis. Eur J Neurol (2014)
P Menon et al. Sensitivity and specificity of threshold tracking transcranial magnetic stimulation for diagnosis of amyotrophic lateral sclerosis: a prospective study. Lancet Neurol (2015)
AC Devlin et al. Human iPSC-derived motoneurons harbouring TARDBP or C9ORF72 ALS mutations are dysfunctional despite maintaining viability. Nat Commun (2015)
J Kim et al. Changes in the Excitability of Neocortical Neurons in a Mouse Model of Amyotrophic Lateral Sclerosis Are Not Specific to Corticospinal Neurons and Are Modulated by Advancing Disease. J Neurosci (2017)
BJ Wainger et al. Intrinsic membrane hyperexcitability of amyotrophic lateral sclerosis patient-derived motor neurons. Cell Rep (2014)
N Delestree et al. Adult spinal motoneurones are not hyperexcitable in a mouse model of inherited amyotrophic lateral sclerosis. J Physiol (2014)
M Cantone et al. The contribution of transcranial magnetic stimulation in the diagnosis and in the management of dementia. Clin Neurophysiol (2014)
JL Sanderson et al. ¥â-Amyloid disruption of LTP/LTD balance is mediated by AKAP150-anchored PKA and Calcineurin regulation of Ca 2+-permeable AMPA receptors. Cell Rep (2021)
CW Chang et al. Tau reduction affects excitatory and inhibitory neurons differently, reduces excitation/inhibition ratios, and counteracts network hypersynchrony. Cell Rep (2021)
GA Czapski et al. Glutamate and GABA in Microglia-Neuron Cross-Talk in Alzheimer's Disease. Int J Mol Sci (2021)
Z Jafari et al. Neural oscillations and brain stimulation in Alzheimer's disease. Prog Neurobiol (2020)
L Verret et al. Inhibitory interneuron deficit links altered network activity and cognitive dysfunction in Alzheimer model. Cell (2012)
HF Iaccarino et al. Gamma frequency entrainment attenuates amyloid load and modifies microglia. Nature (2018)
King AE, et al. Excitotoxicity in ALS: Overstimulation, or overreaction? Exp Neurol (2016)
Bensimon G, et al. A controlled trial of riluzole in amyotrophic lateral sclerosis. N Engl J Med (1994)
C Adaikkan et al. Gamma Entrainment: Impact on Neurocircuits, Glia, and Therapeutic Opportunities. Trends Neurosci (2020)
EM Gibson et al. Neuronal activity promotes oligodendrogenesis and adaptive myelination in the mammalian brain. Science (2014)
TM Herrington. Mechanisms of deep brain stimulation. J Neurophysiol (2016)
ML Martinez-Silva et al. Hypoexcitability precedes denervation in the large fast-contracting motor units in two unrelated mouse models of ALS. Elife (2018)
S Huh et al. Time Course of Alterations in Adult Spinal Motoneuron Properties in the SOD1(G93A) Mouse Model of ALS. eNeuro (2021)
S Saxena et al. Neuroprotection through excitability and mTOR required in ALS motoneurons to delay disease and extend survival. Neuron (2013)
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Boston Children¡¯s Hospital Neurobiology Dept., Postdoc fellow
Bristol Myers Squibb Neuroscience TRC, Principal scientist