저자는 그들의 지원을 위해 멤피스 대학의 기술 페덱스 연구소 감사 그 싶습니다. 저자는 멤피스 (데이비드 버틀러, 재키 카터, 도미닉 클리블랜드, 야곱 섀퍼) 대학에서 기계 공학 부서의 수석 디자인 프로젝트 그룹의 학생들을 인정하고 싶습니다, 모터 제어를위한 대학 멤피스의 공학 기술 부서의 다니엘 콘 세포 배양에서의 도움, 박사 빈 탱과 양 Charlean Luellen. 이 작품은 K01 HL120912 (ER) 및 R01 HL123540 (CMW)에 의해 지원되었다.

보존 셀의 문화 매체에 대한 음의 벽 (최종 제품에 대한 그림 1D 참조) 멤브레인의 1. 건설 <ol><li> 콜라겐 I로 코팅 된 폴리 디메틸 실록산 (PDMS) 시트를 사용하여, 메스 나 다이를가요 성 멤브레인의 윤곽을 잘랐다. </li><li> 저장을위한 60mm 페트리 접시에 각각의 막 놓습니다. </li><li> 벽의 창조 : <ol><li> B (경화제) 엘라스토머 엘라스토머의 중량비는 1 : 10 PDMS 섞는다. </li><li> 50 ㎖ 튜브에 완전히 혼합 된 PDMS 5 mL를 따르십시오. </li><li> 수평 하이브리드 오븐에서 경화 PDMS 50 ml의 튜브를 놓습니다. </li><li> 경화 시간 동안 8 rpm에서 코팅 튜브의 내벽을 로터 함수를 사용한다. 실온에서, PDMS는 완전히 2 일 내에 완치됩니다. </li><li> 무균 세포 배양 후드에 튜브에서 PDMS를 제거합니다. </li><li> 새로운 면도날을 사용하여, 섹션의 높이에 대한 4mm의 PDMS 실린더 분할. </li><li> 막 WA 될 것입니다 섹션을 배치LLS, 수없이 페트리 접시 용기에 벽이 접혔 될 수 있습니다. </li></ol></li><li> 페트리 접시에 두 가지를 유지하면서 하나의 막에 PDMS의 한 벽을 선택하고 센터. </li><li> 접착제로 사용하는 벽의 바깥 둘레에 : (1 비율 10) 조심스럽게 경화 PDMS를 놓습니다. 이 액체를 유지하기 위해 존재하기 때문에 벽과 막 사이의 간격의 형성을 방지합니다. </li><li> 각 페트리 접시 완성 된 멤브레인을 포함하고 치료하는 24 시간 동안 70 ℃의 오븐에서 덮여를 놓습니다. </li></ol> 교정 용 클램프 변위 또는 레이디 얼 성장 (그림 2)와 모터의 회전 2. 상관 관계 <ol><li> 모터를 제어하는​​ 소프트웨어를 시작합니다. </li><li> 모터 소프트웨어의 수동 설정을 사용하여 장치의 클램프를 변위. </li><li> 거리를 측정하고 클램프의 최소 및 최대 변위 모두에서 클램프를 반대 사이의 모터 카운트 위치를 기록한다. </li><li> D의 변화율을 계산모터 카운트 (~ 0-75k 개수)의 함수로서 클램프 사이 istance. 이 막에 달성의 최대 잠재적 인 변형을 나타냅니다. </li></ol> 마우스 폐 상피 세포주에 스트레치 3. 응용 프로그램 (MLE12) <ol><li> 물론 당 유연한 막에 250 만 세포 (1 단계)에서 종자 MLE12 세포는 이틀 컨 플루 언트합니다. 파종 밀도는 다른 세포 유형에 따라 다를 수 있습니다. </li><li> 기계 액추에이터는 완전히 편안한 위치에 있는지 확인합니다. <ol><li> 세포 배양 용지를 제거합니다. </li><li> 여섯 클램프 각각의 두 펀치 구멍, 1.5 mm에게 생검 펀치를 사용하여 멤브레인의 탭 (도 1d 참조). 구멍의 반경 방향 위치는 멤브레인 경험 초기 사전 장력의 양을 결정한다. 어떠한 미리 장력이 요구되지 않은 경우 멤브레인 탭 20.5 mm의 반경 펀치 구멍. </li><li> 펀치 구멍이 클램프 내에서 핀을 일렬로 들것에 막을 놓습니다.장소에 최고 클램프를 놓습니다. 나사 한 번 교류 측면에서 하나를 조입니다. </li><li> 1 ml의 세포 배양 배지를 추가합니다. </li></ol></li><li> 빛의 경로와 멤브레인의 중앙을 중심으로 현미경의 무대 장치를 놓습니다. </li><li> 무대에 장치를 고정하는 테이프 또는 자석 (가능한 경우)를 사용합니다. 일단 고정, 현미경의 스테이지 제어기와 기계 장치의 면내 (막으로 평행 한 방향) 및 수직 (Z 방향)을 제어한다. </li><li> 수동 회전 모터 (20)의 위치 및 속도를 제어함으로써, 제조사에 의해 제공된 소프트웨어를 사용하여 연신을 적용한다. </li></ol> 미토콘드리아 활성 산소 종의 4. 측정 (ROS) <ol><li> 세포가 컨 플루 언트되면, 직접 세포에 미토콘드리아 초과 산화물 표시 등 (5 μm의 최종 농도)와 RT DMEM의 1-2 ml를 추가합니다. </li><li> 37 ℃에서 10 분 동안 품어. </li><li> 워시 세포는 부드럽게 버퍼와 세 번에 물을 욕조에 따뜻하게37 ° C. </li><li> 즉시 똑바로 공 초점 현미경으로 이미 자리에 들것 (단계 2.2)에 유연한 막 놓습니다. </li><li> 페놀 레드 무료 매체 HEPES 25 mm의 DMEM의 1 ML을 추가합니다. </li><li> 580분의 510 nm의 여기 / 방출 필터를 설정합니다. </li><li> 이미지 여러 필드는 매 15 분 미토콘드리아 슈퍼 옥사이드 생산의 원하는 시간 코스를 만들 수 있습니다. </li><li> 캡처 된 이미지에서, 기록 형광 강도는 형광 강도를 정량화 가능한 소프트웨어를 사용하여 각 시간 간격 히스토그램. </li></ol> 스트레칭과 원자 힘 현미경 (5) 응용 프로그램 (AFM) 참고 :이 단계는 특정 원자 현미경과 광학 현미경 조합 (그림 4 및 재료 목록) 제공됩니다. <ol><li> 실험을위한 AFM을 준비합니다. <ol><li> Z 방향의 최대 위치로 AFM 헤드의 높이를 증가시킨다. </li><li> AFM의 다리에 익스텐더를 넣어비행기를 해제하는 AFM은 캔틸레버 연락처 샘플을에서. 시험편 AFM 헤드는 기계 장치의 높이를 수용하도록 해제 될 필요가있다. </li></ol></li><li> (사용 가능한 경우) 광학 현미경을 준비합니다. <ol><li> AFM 스캐너 플레이트를 제거합니다. 원하는 목표를 제거합니다. </li><li> 목적에 스페이서를 추가합니다. 스페이서의 높이는 대물과 특정 AFM 셋업에 달려 있지만, 관측 평면 들것 및 어댑터의 높이 (도 동일한 양만큼 z- 방향으로 이동되기 때문에 광학 이미징이 요구되는 경우에 필요하다 5A). AFM은 일반적으로 상기 장치 광로 저배율 이미징을 제공합니다. </li><li> 그 위치에서 원하는 목표를 다시 마운트합니다. AFM에 다시 스캐너를 설치. </li><li> AFM 소프트웨어를 시작합니다. 형광 측정을위한 광원을 포함한 모든 필요한 광원을 시작합니다. </li><li> 캔틸레버 빔 칩을 탑재하는원하는 측정에 적합합니다. 생균의 탄성률을 측정 할 때 200 PN / nm 이하의 강성이 바람직하다. </li><li> 레이저를 맞추고 장치에 장착 된 유리 커버 슬립에 제조업체의 제안에 따라 캔틸레버의 강성을 보정. </li></ol></li><li> 단계 1에서와 같이 막을 제조되지만 다음과 변형. <ol><li> 즉시 스트레칭 장치에 막을 설치하기 전에, 높이 약 1mm로 벽을 잘라. 이는 멤브레인 벽과로드 셀 간의 간섭 발생을 방지한다. </li><li> 3.2.1-3.2.3 설명 된대로 기계 장치에 막을 마운트합니다. </li><li> 유출시 AFM 스캐너의 손상을 방지하기 위하여 세포 배양 배지를 제거한다. </li><li> 커플 어댑터 (도 5a)와 장치. 스캐너의 어댑터와 기계 장치를 놓습니다. </li><li> 원하는 인장 변형 레벨 막을 스트레칭. </li></ol></li><li&gt; 신장 세포의 나노 압입. <ol><li> 때문에 유출에 AFM 스캐너 또는 현미경 손상을 방지하기 위해 세포에서 미디어의 제한 (&lt;0.5 ml)에 볼륨을 추가합니다. </li><li> 멤브레인 외팔보를 작동. </li><li> 관심 분야를 스캔하고 특정 AFM 장치의 프로토콜을 따르십시오. </li></ol></li></ol>

<ol>
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C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+cytoskeletal+structure+and+mechanics+on+epithelial+cell+injury+during+cyclic+airway+reopening.">Influence of cytoskeletal structure and mechanics on epithelial cell injury during cyclic airway reopening.</a> Am J Physiol Lung Cell Mol Physiol. 297, L881-L891 (2009).</li><li>Jacob, A. M., Gaver, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atelectrauma+disrupts+pulmonary+epithelial+barrier+integrity+and+alters+the+distribution+of+tight+junction+proteins+ZO-1+and+claudin+4.">Atelectrauma disrupts pulmonary epithelial barrier integrity and alters the distribution of tight junction proteins ZO-1 and claudin 4.</a> J Appl Physiol. 113, 1377-1387 (2012).</li><li>DiPaolo, B. C., Lenormand, G., Fredberg, J. J., Margulies, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stretch+magnitude+and+frequency-dependent+actin+cytoskeleton+remodeling+in+alveolar+epithelia.">Stretch magnitude and frequency-dependent actin cytoskeleton remodeling in alveolar epithelia.</a> Am J Physiol Cell Physiol. 299, C345-C353 (2010).</li></ol>

저자는 그들이 더 경쟁 재정적 이익이 없다는 것을 선언합니다.

기계적 스트레칭 동안 라이브 세포 이미징의 고유 장치가 개발되었다; 그리고이 장치는 폐 상피 세포 제어 공학을 연구 프로토콜에서 사용되었다. 예비 연구에서, 단일 개최 스트레칭 기관지 상피 세포에서 미토콘드리아 초과 산화물의 생산을 자극 한 것으로 나타났습니다. 또한, 기계적인 변형의 수준 증가는 폐포 상피 세포 단층의 무결성에 대한 직접적인 손상을 야기하는 것이 입증되었다. </p...

세포는 여러 조직에서의 기계적 하중을 실시하고,이 기계적 자극 유전자 발현, 성장 인자, 사이토 카인, 또는 세포 외 기질의 재 형성의 방출 패턴의 변화를 촉진하고 세포 골격 1-4 밝혀졌다. 기계적 자극에서 형질 세포 내 신호는 mechanotransduction 5-7의 과정을 통해 발생한다. 호흡계에서, mechanotransduction의 일 결과는, 반응성 산소 종 (ROS) 환상 인장 변형의 존재 폐 상피 세포에서 8,9 및 전 염증성 사이토 카인 (10)의 증가이다. 강력한 증거는 과도한 인장력이 11-14 세포의 생화학 적 반응에 더하여, 폐포 상피 부상을 직접 유도 것을 시사한다. 포커스 여기서 기계적 변형에 폐 세포의 반응에 주로이지만 mechanotransduction 의해 유도 경로는 BAS에 중요한 역할혈관 음 (15)의 조정 · 성장판 (16)의 개발을 포함하여 인체의 여러 조직의 IC 기능. mechanotransduction에 대한 관심이 증가 배양 세포 및 조직 생리 학적으로 중요한 기계적 하중의인가에 대한 여러 장치의 발전을 가져왔다. 특히, 조직 경험 기계적 하중의 일반적인 형태 인 인장 변형을, 적용 장치 11,17-19 인기 있습니다. 그러나, 사용 가능한 장치의 대부분은 어느 조직 공학 응용 프로그램을위한 생물 반응기로 설계 또는 스트레칭 실시간 영상에 도움이 아니다. 이와 같이, mechanotransduction의 경로의 조사를 용이하게하기 위해 장력 세포와 조직을 시각화 도구와 방법의 개발이 요구된다. 여기서, 면내 기계적 연신 장치를 설계하고, 프로토콜은 m을 적용하기 위해 개발되었다ultiple 조직에 변형의 형태와 세포를 실시간으로 (그림 1A-D)의 생화학 적 및 기계적 응답의 영상을 허용하면서. 장치는가요 성 멤브레인을 잡고 약 20 % (도 1b)에 면내 방사형 팽창 위로 적용 원주 등 간격 배치 여섯 클램프를 사용한다. 모터 (도 1C)는 인큐베이터의 외측에 배치 된 모터 공급자 독점 소프트웨어에 의해 제어되는 동안 구동 장치는 장기간 세포 배양 용 인큐베이터에 배치 될 수있다. 모터는 긴장과 이완 균일 여섯 들것 클램프 구동, 내부 캠을 회전 선형 드라이버에 접속된다. 기계적인 장치 이외에, 맞춤형가요 성 멤브레인은 기계 시스템에 사용되는 시판되는 세포 배양 준비 막으로부터 만들어졌다. 약의 직경 그리고 원형 벽 (28mm)를 만들어 세포 만 잘 설명 변형 프로파일이 지역에서 배양 할 수 있도록 유연한 막에 부착 하였다. 구동 장치 내에서 이러한 막의 배치는가요 성 멤브레인의 중앙에 균일하고 등방 변형을 제공 할 수 있는지 여부를 확인하기 위하여, 유한 요소 분석은 시판되는 소프트웨어 (도 1E-F)를 수행 하였다. 플렉서블 멤브레인은 대칭 경계 조건으로 메시에 대한 모든 사변형 요소를 이용하여 모델링되었다. 그림 1 층에 표시된 최대 주 변형률의 윤곽 플롯에서 볼 동심 링은 변형의 등방성 분포를 나타냅니다. 막에 의해 경험 한 스트레인은 하중 (도 2)를 통해 표시의 화상을 기록하여 측정 하였다.도 2d는 반경 방향 및 축 방향으로 측정 된 평균 막 응력은 대략 선형임을 나타낸다적용된 모터에 대하여 20 %의 최대 선형 변형까지 카운트한다. 다시 정지 위치로 후퇴 동안 측정과 비교 팽창 동안 측정 균주 수준 사이에는 유의 한 차이가 없었다. 다음으로,가요 ​​성 멤브레인에 정의 배양 인간 기관지 상피 세포 (16HBE) 및 그 핵의 변위를 측정 하였다. 전 세포 변위 디지털 현미경 기록 위상차 이미지를 측정 하였다 반면 16HBE 세포의 형광 표지 (DAPI) 핵은, 공 초점 현미경으로 20 배의 대물 렌즈를 사용하여 영상화되었다. 도 3에서 보듯이, 핵의 변위에 의해 측정 된 변형은 최대 ~ 20 %의 선형 변형에 막 마크의 변위에 의해 측정 된 것과 유사 하였다. 이는 멤브레인에 적용 균주 부착 세포에 전달되었음을 확인한다. 전통적인 현미경에 정의 디바이스의 사용을 기술하는 프로토콜 및 원자 힘 microscopE는 다음과 같이 제공된다.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>SmartMotor NEMA 34: 3400 Series</td>
			<td>MOOG Animatics</td>
			<td>SM3416D</td>
			<td>Integrated motor, controller, amplifier, encoder and communications bus</td>
		</tr>
		<tr>
			<td>Flexcell Membrane (Collagen I coated)</td>
			<td>Flexcell International Corp</td>
			<td>SM2-1010C</td>
			<td>3.5x5.25x0.020&#34;</td>
		</tr>
		<tr>
			<td>Sylgard 184&#160;</td>
			<td>Dow Corning Corporation</td>
			<td></td>
			<td>10:1</td>
		</tr>
		<tr>
			<td>Hoechst 33342&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>H1399</td>
			<td>DAPI stain</td>
		</tr>
		<tr>
			<td>MitoSOX</td>
			<td>Sigma-Aldrich</td>
			<td>M36008</td>
			<td></td>
		</tr>
		<tr>
			<td>Tiron</td>
			<td>Sigma-Aldrich</td>
			<td>D7389&#160;</td>
			<td>mitochondrial superoxide label</td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td></td>
			<td></td>
			<td>superoxide inhibitor</td>
		</tr>
		<tr>
			<td>FBS</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>50 ml tubes</td>
			<td>Fisher Scientific</td>
			<td>06-443-19</td>
			<td>Any centriguge tube can be used to create an area for imaging.</td>
		</tr>
		<tr>
			<td>Hybridization oven</td>
			<td>Bellco Glass</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MLE12 Cells</td>
			<td>ATCC</td>
			<td>CRL-2110</td>
			<td>Mouse Lung Epithelial Cells&#160;</td>
		</tr>
		<tr>
			<td>16HBE cells</td>
			<td>ATCC</td>
			<td>CRL-2741</td>
			<td>Human Bronchial Epithelial Cells</td>
		</tr>
		<tr>
			<td>AFM Indentation Experiments</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cantilever Beams for Nano-indentation</td>
			<td>Budget Sensors</td>
			<td>Si-Ni30</td>
			<td></td>
		</tr>
		<tr>
			<td>AFM&#160;</td>
			<td>Asylum Research</td>
			<td>MFP3D</td>
			<td></td>
		</tr>
		<tr>
			<td>Olympus microscope</td>
			<td>Olympus</td>
			<td>IX-71</td>
			<td>Inverted microscope with 20X and 40X objectives.</td>
		</tr>
		<tr>
			<td>AFM Leg Extenders</td>
			<td>Asylum Research</td>
			<td>Not available</td>
			<td>AFM microscope</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Finite Element Analyses</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ABAQUS</td>
			<td>Simulia</td>
			<td>6.12</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ImageJ</td>
			<td>NIH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microscopes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Digital microscope</td>
			<td>Life Technologies</td>
			<td>EVOS XL Core</td>
			<td>Initially a self standing company, now owned by Life Technologies.</td>
		</tr>
		<tr>
			<td>Confocal microscope</td>
			<td>Zeiss</td>
			<td>LSM 710</td>
			<td>2-photon upright microscope</td>
		</tr>
	</tbody>
</table>

live cell imaging during mechanical stretch

There is currently a significant interest in understanding how cells and tissues respond to mechanical stimuli, but current approaches are limited in their capability for measuring responses in real time in live cells or viable tissue. A protocol was developed with the use of a cell actuator to distend live cells grown on or tissues attached to an elastic substrate while imaging with confocal and atomic force microscopy (AFM). Preliminary studies show that tonic stretching of human bronchial epithelial cells caused a significant increase in the production of mitochondrial superoxide. Moreover, using this protocol, alveolar epithelial cells were stretched and imaged, which showed direct damage to the epithelial cells by overdistention simulating one form of lung injury in vitro. A protocol to conduct AFM nano-indentation on stretched cells is also provided.

활성 산소 종 및 변형 이전의 연구는 환상 스트레칭 21에 응답기도 및 폐포 상피 세포에서 반응성 산소 종 (ROS)의 증가를 보여 주었다. 활성 산소는 분자와 지질, 단백질, 다당류, 핵산 22-24 높은 반응성 산소 분자에서 파생 된 활성 산소를 포함한다. ROS는 일반적인 세포 내 이온 채널의 기능을 조절하는 신호 단백질 키나제 / 포스파타제 활성 및 유전자 ?...

Watch this Scientific Journal Video about Live Cell Imaging during Mechanical Stretch at JoVE.com

Live Cell Imaging during Mechanical Stretch

A novel imaging protocol was developed using a custom motor-driven mechanical actuator to allow the measurement of real time responses to mechanical strain in live cells. Relevant to mechanobiology, the system can apply strains up to 20% while allowing near real-time imaging with confocal or atomic force microscopy.

기계 스트레치 동안 라이브 세포 이미징

There is currently a significant interest in understanding how cells and tissues respond to mechanical stimuli, but current approaches are limited in ...

live-cell-imaging-during-mechanical-stretch

Research

JoVE Journal

Bioengineering

10.3K 조회수.  University of Tennessee Health Science Center. A novel imaging protocol was developed using a custom motor-driven mechanical actuator to allow the measurement of real time responses to mechanical strain in live cells. Relevant to mechanobiology, the system can apply strains up to 20% while allowing near real-time imaging with confocal or atomic force microscopy. 

비디오: Live Cell Imaging during Mechanical Stretch

Axon Stretch Growth: The Mechanotransduction of Neuronal Growth

During pre-synaptic embryonic development, neuronal processes traverse short distances to reach their targets via growth cone. Over time, neuronal somata are separated from their axon terminals due to skeletal growth of the enlarging organism (Weiss 1941; Gray, Hukkanen et al. 1992). This mechanotransduction induces a secondary mode of neuronal growth capable of accommodating continual elongation of the axon (Bray 1984; Heidemann and Buxbaum 1994; Heidemann, Lamoureux et al. 1995; Pfister, Iwata et al. 2004).
Axon Stretch Growth (ASG) is conceivably a central factor in the maturation of short embryonic processes into the long nerves and white matter tracts characteristic of the adult nervous system. To study ASG in vitro, we engineered bioreactors to apply tension to the short axonal processes of neuronal cultures (Loverde, Ozoka et al. 2011). Here, we detail the methods we use to prepare bioreactors and conduct ASG. First, within each stretching lane of the bioreactor, neurons are plated upon a micro-manipulated towing substrate. Next, neurons regenerate their axonal processes, via growth cone extension, onto a stationary substrate. Finally, stretch growth is performed by towing the plated cell bodies away from the axon terminals adhered to the stationary substrate; recapitulating skeletal growth after growth cone extension.
Previous work has shown that ASG of embryonic rat dorsal root ganglia neurons are capable of unprecedented growth rates up to 10mm/day, reaching lengths of up to 10cm; while concurrently resulting in increased axonal diameters (Smith, Wolf et al. 2001; Pfister, Iwata et al. 2004; Pfister, Bonislawski et al. 2006; Pfister, Iwata et al. 2006; Smith 2009). This is in dramatic contrast to regenerative growth cone extension (in absence of mechanical stimuli) where growth rates average 1mm/day with successful regeneration limited to lengths of less than 3cm (Fu and Gordon 1997; Pfister, Gordon et al. 2011). Accordingly, further study of ASG may help to reveal dysregulated growth mechanisms that limit regeneration in the absence of mechanical stimuli.

A unique tissue engineering method was developed to elongate numerous nerve fibers in culture by recapitulating axon stretch growth; a form of nervous system growth whereby nerves elongate in conjunction with growth of the enlarging body.

액슨 스트레치 성장의 연결을 성장의 Mechanotransduction

During pre-synaptic embryonic development, neuronal processes traverse short distances to reach their targets via growth cone. Over time, neuronal somata ...

연구

생체공학

Live-cell Imaging of Migrating Cells Expressing Fluorescently-tagged Proteins in a Three-dimensional Matrix

Traditionally, cell migration has been studied on two-dimensional, stiff plastic surfaces. However, during important biological processes such as wound healing, tissue regeneration, and cancer metastasis, cells must navigate through complex, three-dimensional extracellular tissue. To better understand the mechanisms behind these biological processes, it is important to examine the roles of the proteins responsible for driving cell migration. Here, we outline a protocol to study the mechanisms of cell migration using the epithelial cell line (MDCK), and a three-dimensional, fibrous, self-polymerizing matrix as a model system. This optically clear extracellular matrix is easily amenable to live-cell imaging studies and better mimics the physiological, soft tissue environment. This report demonstrates a technique for directly visualizing protein localization and dynamics, and deformation of the surrounding three-dimensional matrix. 
Examination of protein localization and dynamics during cellular processes provides key insight into protein functions. Genetically encoded fluorescent tags provide a unique method for observing protein localization and dynamics. Using this technique, we can analyze the subcellular accumulation of key, force-generating cytoskeletal components in real-time as the cell maneuvers through the matrix. In addition, using multiple fluorescent tags with different wavelengths, we can examine the localization of multiple proteins simultaneously, thus allowing us to test, for example, whether different proteins have similar or divergent roles. Furthermore, the dynamics of fluorescently tagged proteins can be quantified using Fluorescent Recovery After Photobleaching (FRAP) analysis. This measurement assays the protein mobility and how stably bound the proteins are to the cytoskeletal network.
By combining live-cell imaging with the treatment of protein function inhibitors, we can examine in real-time the changes in the distribution of proteins and morphology of migrating cells. Furthermore, we also combine live-cell imaging with the use of fluorescent tracer particles embedded within the matrix to visualize the matrix deformation during cell migration. Thus, we can visualize how a migrating cell distributes force-generating proteins, and where the traction forces are exerted to the surrounding matrix. Through these techniques, we can gain valuable insight into the roles of specific proteins and their contributions to the mechanisms of cell migration.

Cellular processes such as cell migration have traditionally been studied on two-dimensional, stiff plastic surfaces. This report describes a technique for directly visualizing protein localization and analyzing protein dynamics in cells migrating in a more physiologically relevant, three-dimensional matrix.

3 차원 매트릭스에서 찬란 태그가 추가된 단백질을 표현 마이 그 레이션 전지의 라이브 세포 이미징

Traditionally, cell migration has been studied on two-dimensional, stiff plastic surfaces. However, during important biological processes such as wound ...

Monitoring the Wall Mechanics During Stent Deployment in a Vessel

Clinical trials have reported different restenosis rates for various stent designs1. It is speculated that stent-induced strain concentrations on the arterial wall lead to tissue injury, which initiates restenosis2-7. This hypothesis needs further investigations including better quantifications of non-uniform strain distribution on the artery following stent implantation. A non-contact surface strain measurement method for the stented artery is presented in this work. ARAMIS stereo optical surface strain measurement system uses two optical high speed cameras to capture the motion of each reference point, and resolve three dimensional strains over the deforming surface8,9. As a mesh stent is deployed into a latex vessel with a random contrasting pattern sprayed or drawn on its outer surface, the surface strain is recorded at every instant of the deformation. The calculated strain distributions can then be used to understand the local lesion response, validate the computational models, and formulate hypotheses for further in vivo study.

Stent-induced arterial strain distributions are characterized using an optical surface strain measurement system. This visualization technique is used to gain insights into the impact of stent implantation on the host vessel.

선박의 스텐 트를 배포하는 동안 벽 역학 모니터링

Clinical trials have reported different restenosis rates for various stent designs1. It is speculated that stent-induced strain concentrations on the ...

High Throughput Single-cell and Multiple-cell Micro-encapsulation

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement from a bulk fluid environment with applications in high throughput screening, cytometry, and mass spectrometry. We describe a method to not only encapsulate single cells, but to repeatedly capture a set number of cells (here we demonstrate one- and two-cell encapsulation) to study both isolation and the interactions between cells in groups of controlled sizes. By combining drop generation techniques with cell and particle ordering, we demonstrate controlled encapsulation of cell-sized particles for efficient, continuous encapsulation. Using an aqueous particle suspension and immiscible fluorocarbon oil, we generate aqueous drops in oil with a flow focusing nozzle. The aqueous flow rate is sufficiently high to create ordering of particles which reach the nozzle at integer multiple frequencies of the drop generation frequency, encapsulating a controlled number of cells in each drop. For representative results, 9.9 &mu;m polystyrene particles are used as cell surrogates. This study shows a single-particle encapsulation efficiency Pk=1 of 83.7% and a double-particle encapsulation efficiency Pk=2 of 79.5% as compared to their respective Poisson efficiencies of 39.3% and 33.3%, respectively. The effect of consistent cell and particle concentration is demonstrated to be of major importance for efficient encapsulation, and dripping to jetting transitions are also addressed. 
Introduction 
Continuous media aqueous cell suspensions share a common fluid environment which allows cells to interact in parallel and also homogenizes the effects of specific cells in measurements from the media. High-throughput encapsulation of cells into picoliter-scale drops confines the samples to protect drops from cross-contamination, enable a measure of cellular diversity within samples, prevent dilution of reagents and expressed biomarkers, and amplify signals from bioreactor products. Drops also provide the ability to re-merge drops into larger aqueous samples or with other drops for intercellular signaling studies.1,2 The reduction in dilution implies stronger detection signals for higher accuracy measurements as well as the ability to reduce potentially costly sample and reagent volumes.3 Encapsulation of cells in drops has been utilized to improve detection of protein expression,4 antibodies,5,6 enzymes,7 and metabolic activity8 for high throughput screening, and could be used to improve high throughput cytometry.9 Additional studies present applications in bio-electrospraying of cell containing drops for mass spectrometry10 and targeted surface cell coatings.11 Some applications, however, have been limited by the lack of ability to control the number of cells encapsulated in drops. Here we present a method of ordered encapsulation12 which increases the demonstrated encapsulation efficiencies for one and two cells and may be extrapolated for encapsulation of a larger number of cells.
To achieve monodisperse drop generation, microfluidic "flow focusing" enables the creation of controllable-size drops of one fluid (an aqueous cell mixture) within another (a continuous oil phase) by using a nozzle at which the streams converge.13 For a given nozzle geometry, the drop generation frequency f and drop size can be altered by adjusting oil and aqueous flow rates Qoil and Qaq. As the flow rates increase, the flows may transition from drop generation to unstable jetting of aqueous fluid from the nozzle.14 
When the aqueous solution contains suspended particles, particles become encapsulated and isolated from one another at the nozzle. For drop generation using a randomly distributed aqueous cell suspension, the average fraction of drops Dk containing k cells is dictated by Poisson statistics, where Dk = &lambda;k exp(-&lambda;)/(k!) and &lambda; is the average number of cells per drop. The fraction of cells which end up in the "correctly" encapsulated drops is calculated using Pk = (k x Dk)/&Sigma;(k' x Dk'). The subtle difference between the two metrics is that Dk relates to the utilization of aqueous fluid and the amount of drop sorting that must be completed following encapsulation, and Pk relates to the utilization of the cell sample. As an example, one could use a dilute cell suspension (low &lambda;) to encapsulate drops where most drops containing cells would contain just one cell. While the efficiency metric Pk would be high, the majority of drops would be empty (low Dk), thus requiring a sorting mechanism to remove empty drops, also reducing throughput.15
Combining drop generation with inertial ordering provides the ability to encapsulate drops with more predictable numbers of cells per drop and higher throughputs than random encapsulation. Inertial focusing was first discovered by Segre and Silberberg16 and refers to the tendency of finite-sized particles to migrate to lateral equilibrium positions in channel flow. Inertial ordering refers to the tendency of the particles and cells to passively organize into equally spaced, staggered, constant velocity trains. Both focusing and ordering require sufficiently high flow rates (high Reynolds number) and particle sizes (high Particle Reynolds number).17,18 Here, the Reynolds number Re =uDh/&nu; and particle Reynolds number Rep =Re(a/Dh)2, where u is a characteristic flow velocity, Dh [=2wh/(w+h)] is the hydraulic diameter, &nu; is the kinematic viscosity, a is the particle diameter, w is the channel width, and h is the channel height. Empirically, the length required to achieve fully ordered trains decreases as Re and Rep increase. Note that the high Re and Rep requirements (for this study on the order of 5 and 0.5, respectively) may conflict with the need to keep aqueous flow rates low to avoid jetting at the drop generation nozzle. Additionally, high flow rates lead to higher shear stresses on cells, which are not addressed in this protocol. The previous ordered encapsulation study demonstrated that over 90% of singly encapsulated HL60 cells under similar flow conditions to those in this study maintained cell membrane integrity.12 However, the effect of the magnitude and time scales of shear stresses will need to be carefully considered when extrapolating to different cell types and flow parameters. The overlapping of the cell ordering, drop generation, and cell viability aqueous flow rate constraints provides an ideal operational regime for controlled encapsulation of single and multiple cells.
Because very few studies address inter-particle train spacing,19,20 determining the spacing is most easily done empirically and will depend on channel geometry, flow rate, particle size, and particle concentration. Nonetheless, the equal lateral spacing between trains implies that cells arrive at predictable, consistent time intervals. When drop generation occurs at the same rate at which ordered cells arrive at the nozzle, the cells become encapsulated within the drop in a controlled manner. This technique has been utilized to encapsulate single cells with throughputs on the order of 15 kHz,12 a significant improvement over previous studies reporting encapsulation rates on the order of 60-160 Hz.4,15 In the controlled encapsulation work, over 80% of drops contained one and only one cell, a significant efficiency improvement over Poisson (random) statistics, which predicts less than 40% efficiency on average.12
In previous controlled encapsulation work,12 the average number of particles per drop &lambda; was tuned to provide single-cell encapsulation. We hypothesize that through tuning of flow rates, we can efficiently encapsulate any number of cells per drop when &lambda; is equal or close to the number of desired cells per drop. While single-cell encapsulation is valuable in determining individual cell responses from stimuli, multiple-cell encapsulation provides information relating to the interaction of controlled numbers and types of cells. Here we present a protocol, representative results using polystyrene microspheres, and discussion for controlled encapsulation of multiple cells using a passive inertial ordering channel and drop generation nozzle.

Combining monodisperse drop generation with inertial ordering of cells and particles, we describe a method to encapsulate a desired number of cells or particles in a single drop at kHz rates. We demonstrate efficiencies twice exceeding those of unordered encapsulation for single- and double-particle drops.

높은 처리량 마이크로 캡슐 단일 셀 및 다중 셀

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement ...

Using Microfluidics Chips for Live Imaging and Study of Injury Responses in Drosophila Larvae

Live imaging is an important technique for studying cell biological processes, however this can be challenging in live animals. The translucent cuticle of the Drosophila larva makes it an attractive model organism for live imaging studies. However, an important challenge for live imaging techniques is to noninvasively immobilize and position an animal on the microscope. This protocol presents a simple and easy to use method for immobilizing and imaging Drosophila larvae on a polydimethylsiloxane (PDMS) microfluidic device, which we call the 'larva chip'. The larva chip is comprised of a snug-fitting PDMS microchamber that is attached to a thin glass coverslip, which, upon application of a vacuum via a syringe, immobilizes the animal and brings ventral structures such as the nerve cord, segmental nerves, and body wall muscles, within close proximity to the coverslip. This allows for high-resolution imaging, and importantly, avoids the use of anesthetics and chemicals, which facilitates the study of a broad range of physiological processes. Since larvae recover easily from the immobilization, they can be readily subjected to multiple imaging sessions. This allows for longitudinal studies over time courses ranging from hours to days. This protocol describes step-by-step how to prepare the chip and how to utilize the chip for live imaging of neuronal events in 3rd instar larvae. These events include the rapid transport of organelles in axons, calcium responses to injury, and time-lapse studies of the trafficking of photo-convertible proteins over long distances and time scales. Another application of the chip is to study regenerative and degenerative responses to axonal injury, so the second part of this protocol describes a new and simple procedure for injuring axons within peripheral nerves by a segmental nerve crush.

Using Microfluidics Chips for Live Imaging and Study of Injury Responses in Drosophila Larvae

Drosophila larvae are an attractive model system for live imaging due to their translucent cuticle and powerful genetics. This protocol describes how to utilize a single-layer PDMS device, called the &#39;larva chip&#39; for live imaging of cellular processes within neurons of 3rd instar Drosophila larvae.

라이브 이미징 및 상해 응답의 연구에 대한 마이크로 유체 칩을 사용<em&gt; 초파리</em&gt; 애벌레

Live imaging is an important technique for studying cell biological processes, however this can be challenging in live animals. The translucent cuticle of ...

A Microfluidic Technique to Probe Cell Deformability

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an efficient manner. Typically, data for ~102 cells can be acquired within a 1 hr experiment. An automated image analysis program enables efficient post-experiment analysis of image data, enabling processing to be complete within a few hours. Our device geometry is unique in that cells must deform through a series of micron-scale constrictions, thereby enabling the initial deformation and time-dependent relaxation of individual cells to be assayed. The applicability of this method to human promyelocytic leukemia (HL-60) cells is demonstrated. Driving cells to deform through micron-scale constrictions using pressure-driven flow, we observe that human promyelocytic (HL-60) cells momentarily occlude the first constriction for a median time of 9.3 msec before passaging more quickly through the subsequent constrictions with a median transit time of 4.0 msec per constriction. By contrast, all-trans retinoic acid-treated (neutrophil-type) HL-60 cells occlude the first constriction for only 4.3 msec before passaging through the subsequent constrictions with a median transit time of 3.3 msec. This method can provide insight into the viscoelastic nature of cells, and ultimately reveal the molecular origins of this behavior.

We demonstrate a microfluidics-based assay to measure the timescale for cells to transit through a sequence of micron-scale constrictions.

미세 유체 기술은 셀 변형능을 검사 할

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an ...

From Fast Fluorescence Imaging to Molecular Diffusion Law on Live Cell Membranes in a Commercial Microscope

It has become increasingly evident that the spatial distribution and the motion of membrane components like lipids and proteins are key factors in the regulation of many cellular functions. However, due to the fast dynamics and the tiny structures involved, a very high spatio-temporal resolution is required to catch the real behavior of molecules. Here we present the experimental protocol for studying the dynamics of fluorescently-labeled plasma-membrane proteins and lipids in live cells with high spatiotemporal resolution. Notably, this approach doesn&#8217;t need to track each molecule, but it calculates population behavior using all molecules in a given region of the membrane. The starting point is a fast imaging of a given region on the membrane. Afterwards, a complete spatio-temporal autocorrelation function is calculated correlating acquired images at increasing time delays, for example each 2, 3, n repetitions. It is possible to demonstrate that the width of the peak of the spatial autocorrelation function increases at increasing time delay as a function of particle movement due to diffusion. Therefore, fitting of the series of autocorrelation functions enables to extract the actual protein mean square displacement from imaging (iMSD), here presented in the form of apparent diffusivity vs average displacement. This yields a quantitative view of the average dynamics of single molecules with nanometer accuracy. By using a GFP-tagged variant of the Transferrin Receptor (TfR) and an ATTO488 labeled 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphoethanolamine (PPE) it is possible to observe the spatiotemporal regulation of protein and lipid diffusion on &#181;m-sized membrane regions in the micro-to-milli-second time range.

Spatial distribution and temporal dynamics of plasma membrane proteins and lipids is a hot topic in biology. Here this issue is addressed by a spatio-temporal image fluctuation analysis that provides conceptually the same physical quantities of single particle tracking, but it uses small molecular labels and standard microscopy setups.

상용 현미경에서 라이브 세포막에 분자 확산 법률에 빠른 형광 이미징

It has become increasingly evident that the spatial distribution and the motion of membrane components like lipids and proteins are key factors in the ...

Isokinetic Robotic Device to Improve Test-Retest and Inter-Rater Reliability for Stretch Reflex Measurements in Stroke Patients with Spasticity

Measuring spasticity is important in treatment planning and determining efficacy after treatment. However, the current tool used in clinical settings has been shown to be limited in inter-rater reliability. One factor in this poor inter-rater reliability is the variability of passive motion while measuring the angle of catch (AoC) measurements. Therefore, an isokinetic device has been proposed to standardize the manual joint motion; however, the benefits of isokinetic motion for AoC measurements has not been tested in a standardized manner. This protocol investigates whether isokinetic motion itself can improve inter-rater reliability for AoC measurements. For this purpose, a robotic isokinetic device was developed that is combined with surface electromyography (EMG). Two conditions, manual and isokinetic motions, are compared with the standardized method to measure the angle and subjective feeling of catch. It is shown that in 17 stroke patients with mild elbow flexor spasticity, isokinetic motion improved the intraclass correlation coefficient (ICC) for inter-rater reliability of AoC measurements to 0.890 [95% confidence interval (CI): 0.685&#8211;0.961] by the EMG criteria, and 0.931 (95% CI: 0.791&#8211;0.978) by the torque criteria, from 0.788 (95% CI: 0.493&#8211;0.920) by manual motion. In conclusion, isokinetic motion itself can improve inter-rater reliability of AoC measurements in stroke patients with mild spasticity. Given that this system may provide greater standardized angle measurements and catch of feeling, it may be a good option for the evaluation of spasticity in a clinical setting.

Using a robotic isokinetic device with electromyography (EMG) measurements, this protocol illustrates that isokinetic motion itself can improve inter-rater reliability for the angle of catch measurements in stroke patients with mild elbow flexor spasticity.

경직성이 있는 뇌졸중 환자의 스트레치 반사 측정을 위한 테스트 재검사 및 평가자 간 신뢰성을 향상시키는 이소키네틱 로봇 장치

Measuring spasticity is important in treatment planning and determining efficacy after treatment. However, the current tool used in clinical settings has ...

Controlled Strain of 3D Hydrogels under Live Microscopy Imaging

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized in vitro stretching methods. Various available systems use 2D substrate-based stretchers, while the accessibility of 3D techniques to strain soft hydrogels, is more restricted. Here, we describe a method that allows external stretching of soft hydrogels from their circumference, using an elastic silicone strip as the sample carrier. The stretching system utilized in this protocol is constructed from 3D-printed parts and low-cost electronics, making it simple and easy to replicate in other labs. The experimental process begins with polymerizing thick (&#62;100 &#956;m) soft fibrin hydrogels (Elastic Modulus of ~100 Pa) in a cut-out at the center of a silicone strip. Silicone-gel constructs are then attached to the printed-stretching device and placed on the confocal microscope stage. Under live microscopy the stretching device is activated, and the gels are imaged at various stretch magnitudes. Image processing is then used to quantify the resulting gel deformations, demonstrating relatively homogenous strains and fiber alignment throughout the gel&#8217;s 3D thickness (Z-axis). Advantages of this method include the ability to strain extremely soft hydrogels in 3D while executing in situ microscopy, and the freedom to manipulate the geometry and size of the sample according to the user&#8217;s needs. Additionally, with proper adaptation, this method can be used to stretch other types of hydrogels (e.g., collagen, polyacrylamide or polyethylene glycol) and can allow for analysis of cells and tissue response to external forces under more biomimetic 3D conditions.

The presented method involves uniaxial stretching of 3D soft hydrogels embedded in silicone rubber while allowing live confocal microscopy. Characterization of the external and internal hydrogel strains as well as fiber alignment are demonstrated. The device and protocol developed can assess the response of cells to various strain regimes.

라이브 현미경 이미징 에서 3D 하이드로겔의 제어 변형

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized ...

A Microphysiological System to Study Leukocyte-Endothelial Cell Interaction during Inflammation

Leukocyte-endothelial cell interactions play an important role in inflammatory diseases such as sepsis. During inflammation, excessive migration of activated leukocytes across the vascular endothelium into key organs can lead to organ failure. A physiologically relevant biomimetic microfluidic assay (bMFA) has been developed and validated using several experimental and computational techniques, which can reproduce the entire leukocyte rolling/adhesion/migration cascade to study leukocyte-endothelial cell interactions. Microvascular networks obtained from in vivo images in rodents were digitized using a Geographic Information System (GIS) approach and microfabricated with polydimethylsiloxane (PDMS) on a microscope slide. To study the effect of shear rate and vascular topology on leukocyte-endothelial cell interactions, a Computational Fluid Dynamics (CFD) model was developed to generate a corresponding map of shear rates and velocities throughout the network. The bMFA enables the quantification of leukocyte-endothelial cells interactions, including rolling velocity, number of adhered leukocytes in response to different shear rates, number of migrated leukocytes, endothelial cell permeability, adhesion molecule expression and other important variables. Furthermore, by using human-related samples, such as human endothelial cells and leukocytes, bMFA provides a tool for rapid screening of potential therapeutics to increase their clinical translatability.

In this protocol, a biomimetic microfluid assay, which can reproduce a physiologically relevant microvascular environment and reproduce the entire leukocyte adhesion/migration cascade, is employed to study leukocyte-endothelial cell interactions in inflammatory disease.

염증 중 백혈구-내피 세포 상호작용을 연구하는 미생리학적 시스템

Leukocyte-endothelial cell interactions play an important role in inflammatory diseases such as sepsis. During inflammation, excessive migration of ...