Yazarlar, desteklerinden dolayı Memphis Üniversitesi&#39;nde Teknoloji Fedex Enstitüsü&#39;ne teşekkür isterim. Yazarlar Memphis (David Butler, Jackie Carter, Dominick Cleveland, Jacob Shaffer) Üniversitesi Makine Mühendisliği Bölümü&#39;nde kıdemli tasarım proje grubunun öğrencileri kabul etmek istiyorum, motor kontrolü için University of Memphis Mühendislik Teknolojisi bölümünden Daniel Kohn Hücre kültüründe yardım ettikleri için, Dr. Bin Teng ve Bayan Charlean Luellen. Bu eser K01 HL120912 (ER) ve R01 HL123540 (CMW) tarafından desteklenmiştir.

Tutma Hücre Kültürü Medya Kuyu Walls (nihai ürün için Şekil 1D bakınız) Membran 1. İnşaat <ol><li> Kollajen I ile kaplanmış polidimetilsiloksan (PDMS) yaprak kullanarak, neşter veya bir kalıp esnek membran hatlarını kesti. </li><li> Depolanması için bir 60 mm Petri kabı, her membran yerleştirin. </li><li> Duvarların Oluşturma: <ol><li> B (sertleştirici) elastomer elastomer A: 1 ağırlık oranında, bir 10 PDMS karıştırın. </li><li> 50 ml tüpler içine tam olarak karıştırılır PDMS 5 ml dökün. </li><li> Yatay bir hibridizasyon fırında sertleşmemiş PDMS ile 50 ml&#39;lik tüpler yerleştirin. </li><li> Kür süresinde 8 rpm&#39;de kaplamak için tüplerin iç duvarları rotor işlevini kullanın. Oda sıcaklığında, PDMS tam 2 gün içinde tedavi edilecek. </li><li> Steril hücre kültürü kaputu tüpten PDMS çıkarın. </li><li> Yeni bir jilet kullanarak, bölümlerde yüksekliği 4 mm içine PDMS silindir bölümlemek. </li><li> Membran wa olarak görev yapacak bölümleri, koyunlls, izin vermeden bir Petri kabı kabına duvarları buruşuk olmak. </li></ol></li><li> Petri kabındaki iki korurken, bir zar üzerinde PDMS bir duvar seçin ve merkezi. </li><li> Tutkal olarak kullanılmak üzere, duvarın dış çevre üzerinde (1 oranında 10) hafifçe sertleşmemiş PDMS yerleştirin. Bu sıvı tutmak için olmadığı duvar ve zar arasındaki boşluk oluşmasını önler. </li><li> Her petri çanağı tamamlanmış membran içeren ve tedavi etmek için 24 saat boyunca 70 ° C&#39;de bir fırın içinde kapalı bir yer. </li></ol> Kalibrasyon için Kelepçe Yerinden veya Radyal Büyüme (Şekil 2) Motorlu Münavebesindeki 2. Korelasyon <ol><li> Motorun kontrol yazılımını başlatın. </li><li> Motor yazılımı manuel ayarını kullanarak cihazın kelepçeleri yerinden. </li><li> Mesafeyi ölçün ve kelepçeler minimum ve maksimum deplasman hem de kelepçeler karşıt arasındaki motor sayısı konumunu kaydedin. </li><li> D yüzde değişim hesaplayınMotor sayımı (~ 0-75k sayımları) &#39;in bir fonksiyonu olarak kelepçeler arasında istance. Bu membran üzerinde elde edilen maksimum potansiyel gerginlik gösterecektir. </li></ol> Fare Akciğer Epitel Hücre Hattı Stretch 3. Uygulama (MLE12) <ol><li> Oyuk başına esnek bir zar üzerinde 2.500.000 hücreleri (Aşama 1) Tohum MLE12 hücreler iki gün içinde birleşmiş olması. tohum yoğunluğu farklı hücre tipleri için farklı olabilir. </li><li> Mekanik aktüatör tamamen rahat bir konumda olduğundan emin olun. <ol><li> Hücre kültürü ortamı çıkarın. </li><li> Altı kelepçenin her iki delikler, 1.5 mm biyopsi kalıplar kullanılarak membran çıkıntıları (Şekil 1D bakınız). deliklerin radyal yerleştirme membran deneyimleri başlangıçta ön gerilim miktarını belirler. Hiçbir ön gerilim isteniyorsa membran sekmelerde 20.5 mm yarıçapında delikler. </li><li> Delikli delik kelepçeler içinde iğne ile sıraya ile sedye üzerinde membran yerleştirin.Yerde üst kelepçeleri yerleştirin. Vidaları zaman alternatif tarafta bir tane sıkın. </li><li> 1 ml hücre kültür ortamı ekleyin. </li></ol></li><li> Işık yolu ile membran orta merkezleme mikroskop sahnede cihazı yerleştirin. </li><li> Sahneye cihazı sabitlemek için bant veya mıknatısları (mümkünse) kullanın. Bir kez, sabit, mikroskop aşamasında kontrol ünitesi ile mekanik bir cihazın düzlem (zara paralel) ve dikey (z-yönü) kontrol eder. </li><li> Manuel motor dönüş 20 konumunu ve hızını kontrol ederek üretici tarafından sağlanan yazılım ile streç uygulayın. </li></ol> Mitokondriyal reaktif oksijen türlerinin 4. Ölçüm (ROS) <ol><li> Hücreler birleştiklerinde, sonra, doğrudan hücrelerde mitokondriyal süperoksit göstergesi (5 uM nihai konsantrasyon) ile RT DMEM 1-2 ml ekleyin. </li><li> 37 ° C&#39;de 10 dakika süreyle inkübe edin. </li><li> Yıkama Hücreler nazikçe tampon maddesi ile üç defa bir su banyosu içinde ısıtılmıştır37 ° C. </li><li> Hemen dik konfokal mikroskop altında zaten yerinde sedyeye (Adım 2.2) esnek membran yerleştirin. </li><li> Fenol-kırmızı içermeyen ortamda ve HEPES 25 mM DMEM 1 ml ilave edilir. </li><li> 510/580 nm uyarım / emisyon filtreleri ayarlayın. </li><li> Görüntü birden alanlar her 15 dk mitokondriyal süperoksit üretiminin istenilen zaman ders oluşturmak için. </li><li> Çekilen görüntülerin itibaren, rekor floresan yoğunluğu floresan yoğunluğu miktarının yeteneğine sahip yazılımı kullanarak her zaman aralığında histogramlar. </li></ol> Streç ve Atomik Kuvvet Mikroskobu 5. Uygulama (AFM) Not: Bu adımlarda, belirli bir AFM ve optik mikroskop kombinasyonu (Şekil 4 ve Malzeme Listesi) için verilmiştir. <ol><li> Deney için AFM hazırlayın. <ol><li> Z-doğrultusunda maksimum pozisyona AFM baş yüksekliğini artırın. </li><li> AFM ayakları üzerine genişleticiler koyUçağı kaldırmak hangi AFM konsol temas örnek de. Numune ve AFM kafası mekanik bir cihaz yüksekliğine uyacak kaldırılması gerekir. </li></ol></li><li> (Varsa) optik mikroskop hazırlayın. <ol><li> AFM tarayıcı plakasını sökün. İstenilen hedefe çıkarın. </li><li> Amaç için bir ayırıcı ekleyin. aralama yüksekliği objektif ve belirli AFM set-up bağlı olacaktır, ancak gözlem uçağı sedye ve adaptör yüksekliği (Şekil eşit miktarda z-yönünde kayma olacağından optik görüntüleme isteniyorsa gerekli olduğunu 5A). AFM genellikle cihazın üzerinde bir optik yolundan düşük büyütme görüntüleme sağladığını unutmayın. </li><li> Konumu istenen amaç geri monte edin. AFM geri tarayıcıyı yerleştirin. </li><li> AFM yazılımını başlatın. Floresan ölçümleri için ışık kaynağı dahil gerekli bütün ışık kaynakları başlatın. </li><li> Bir konsol kiriş ile bir çip monte olduğunuarzu edilen ölçümler için uygundur. Canlı hücrelerin elastik modülü ölçerken 200 pN / nm ya da daha az sertlik tercih edilmektedir. </li><li> Lazer hizalama ve cihaz üzerine monte edilmiş bir cam lamel üzerinde üreticinin önerilerine göre konsol sertliği kalibre. </li></ol></li><li> Aşama 1 &#39;de olduğu gibi bir zar hazırlama, ancak şu değişiklikler yapılmıştır. <ol><li> Hemen germe aygıtının için membran takmadan önce, yüksekliği yaklaşık 1 mm duvar kesti. Bu membran duvar ve yük hücresi arasında yaşanan girişimi önler. </li><li> 3.2.1-3.2.3 tarif edildiği gibi mekanik bir cihaz ile ilgili membran monte edin. </li><li> Bir dökülme durumunda AFM tarayıcı zarar görmesini önlemek için hücre kültürü ortamı çıkarın. </li><li> Çift bir adaptör (Şekil 5A) ile bir cihaz. Tarayıcının adaptörle mekanik cihaz yerleştirin. </li><li> İstenen gerilme gerinim seviyesine membran gerin. </li></ol></li><li&gt; Gergin hücrelerin Nano-girinti. <ol><li> Nedeniyle dökülme için AFM tarayıcı veya mikroskop zarar görmesini önlemek için hücreler üzerinde medya sınırlı (&lt;0.5 ml) hacmi ekleyin. </li><li> Membran ile konsol kiriş Engage. </li><li> Ilgi alanları taramak için belirli AFM cihazının protokolünü izleyin. </li></ol></li></ol>

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Yazarlar hiçbir rakip mali çıkarlarını olduğunu beyan ederim.

Mekanik streç sırasında canlı hücre görüntüleme için benzersiz bir cihaz geliştirildi; ve bu cihaz, akciğer epitelyal hücre mechanobiology incelemek için bir protokol kullanılmıştır. Ön çalışmalarda, tek tutulan streç bronşiyal epitel hücrelerde mitokondrial süperoksid üretimini uyardığı tespit edildi. Buna ek olarak, mekanik zorlanma artmış seviyeleri alveolar epitel hücrelerinin bir tek tabaka bütünlüğü doğrudan bozukluklara sebep olduğu gösterilmiştir. <p class="jove_conte...

Hücreler, bir çok dokuda mekanik yüklere maruz kalır ve bu, mekanik uyarma gen ekspresyonu, büyüme faktörleri, sitokinler, ya da hücre dışı matrisin yeniden verildiği şekillerindeki değişiklikleri teşvik etmek ve 1-4 hücre iskeletinin gösterilmiştir. Bu tür mekanik uyarıcılara karşı hücre içi sinyallere mechanotransduction 5-7 işleminde meydana gelir. Solunum sisteminde, mechanotransduction bir sonucu, reaktif oksijen türlerinin (ROS), siklik bir çekme gücü mevcudiyetinde pulmoner epitel hücrelerinde 8,9 ve pro-inflamatuar sitokinlerin 10 artıştır. Güçlü kanıtlar ayrıca aşırı gerilim soyu hücrelerinin 11-14 biyokimyasal yanıtların yanı sıra, alveol epiteline yaralanması doğrudan yol açtığını göstermektedir. Odak Burada mekanik deformasyon akciğer hücrelerinin yanıtı esas olmasına rağmen, mechanotransduction neden yollar bas önemli bir rol oynardamar tonusu 15 düzenlenmesinde ve büyüme plağının 16 geliştirilmesi dahil olmak üzere insan vücudunda birçok dokuda, bir ic fonksiyonu. mechanotransduction artan ilgi kültürlenmiş hücreler ve doku için fizyolojik olarak ilgili mekanik yüklerin uygulanması için çok sayıda cihazı geliştirilmesi ile sonuçlanmıştır. Özel olarak, doku tarafından yaşanan mekanik yüklenme ortak bir biçimi olan bir çekme gücü, uygulama tertibatının 11,17-19 popülerdir. Ancak, mevcut cihazların çoğu ya doku mühendisliği uygulamaları için biyoreaktör olarak tasarımlanmış veya streç ile gerçek zamanlı görüntüleme için elverişli değildir. Bu nedenle, mechanotransduction arasında yolların araştırılmasını kolaylaştırmak için gerilim hücre ve dokuları görselleştirmek araçları ve yöntemlerinin geliştirilmesi için bir ihtiyaç vardır. Burada, bir düzlem mekanik germe cihazı tasarlanmıştır ve protokoller m uygulamak için geliştirilmiştirultiple dokulara soyunun formları ve hücreler, gerçek zaman (Şekil 1A-D), biyokimyasal ve mekanik yanıtların görüntüleme imkan verir. Cihaz, esnek bir membran kavramak ve yaklaşık% 20 (Şekil 1B) bir düzlemsel radyal distansiyon yukarı uygulamak için çevresel olarak yerleştirilmiş olan eşit aralıklı kelepçeler kullanılmaktadır. Motor (Şekil 1C) inkübatör dışına yerleştirilmiş ve motor satıcı tarafından sunulan özel yazılım tarafından kontrol edilir ise çalıştırma tertibatı, uzun bir zaman süresi için bir hücre kültürü inkübatöründe yerleştirilebilir. kas gerginliği ve gevşeme eşit altı sedye kelepçeler sürüş bir iç cam döner lineer sürücü bağlanır. Mekanik cihaz ek olarak, özel esnek zarların mekanik bir sistemde kullanılmak üzere ticari olarak temin edilebilen hücre kültürü hazır zarlarından oluşturulmuştur. Yaklaşık bir çapı olan, dairesel sonra duvar (28 mm) yapılmıştır ve hücreler, sadece iyi tarif edilen suş profili bu bölgede kültürlenebilir böylece esnek bir zar üzerine bağlanmıştır. Harekete geçirme cihazı içinde bu membranların yerleştirilmesi, esnek bir zarın merkezinde tek tip ve izotropik streynini sağlayabilir olup olmadığını belirlemek için, sonlu eleman analizi, ticari olarak temin edilebilen yazılımı (Şekil 1E-F) kullanılarak yapıldı. Esnek zar simetrik sınır koşulları ve örgü için tüm dörtgen elemanlar kullanan ile modellenmiştir. Şekil 1F gösterilen maksimum asal zorlanma kontur arsa görülen eş halkalar zorlanma izotropik dağılımını göstermektedir. membran tarafından hissedilen gerginlik yükleme (Şekil 2) vasıtasıyla işaretler görüntüleri kaydedilerek sürekli olarak ölçüldü. Şekil 2B, radyal ve eksenel yönde ölçülen ortalama membran soyu yaklaşık doğrusal olduğunu göstermektediruygulanan motoru ile ilgili olarak% 20 oranında bir maksimum doğrusal suşu kadar sayar. Geri dinlenme pozisyonuna geri çekilmesi sırasında ölçülen kıyasla distansiyon sırasında ölçülen gerilme düzeyleri arasında anlamlı bir fark yoktu. Daha sonra, özel bir esnek zar üzerinde kültürlenmiş insan bronşiyal epitel hücreleri (16HBE) ve bunların çekirdeklerinin değiştirme ölçüldü. Bütün hücre yer değiştirmesi, bir dijital mikroskop ile kaydedilen faz kontrast görüntüleri ile ölçüldü ise 16HBE hücrelerinin floresan etiketli (DAPI) çekirdekler, konfokal mikroskop altında bir 20x objektif kullanılarak görüntülendi. Şekil 3&#39;te görüldüğü gibi, çekirdek yer değiştirmesi ile ölçülen gerilme, up ~% 20 lineer streyn zar üzerinde işaretlerin yer değiştirmesi ile ölçülen benzer olmuştur. Bu membranların uygulanan gerilme yapışık hücrelere iletilen olduğunu doğrulamaktadır. Geleneksel mikroskop özel cihazın kullanımını anlatan protokolleri ve atomik kuvvet mikroskopE, aşağıdaki adımlarda verilmiştir.

<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.

Reaktif Oksijen Türleri ve Deformasyon Daha önce yapılan çalışmalar, siklik streç 21 tepki olarak hava yolu ve alveolar epitel hücrelerinin, reaktif oksijen türlerinin (ROS) artış göstermiştir. Reaktif oksijen türleri, molekülleri ve lipitler, proteinler, polisakkaritler, nükleik asitler, 22-24, yüksek reaktiviteye sahip moleküler oksijenden türemiş serbest radikalleri içerir. ROS, ortak bir hücre içi iyon kanalı fonksiyonu düzenleyen b...

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.

Mekanik Stretch sırasında Canlı Hücre Görüntüleme

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 Görüntüleme.  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. 

Video: 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.

Akson Streç Büyüme: Nöronal Büyüme Mechanotransduction

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

Biyomühendislik

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.

Üç boyutlu Matrix floresan etiketli Proteinler ifade Geçiş Hücreler Canlı hücre Görüntüleme

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.

Bir Gemi Stent Dağıtım sırasında Duvar Mekaniği izlenmesi

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.

Yüksek Verim Micro-encapsulation Tek hücreli ve Çoklu-hücre

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.

Canlı Görüntüleme ve Yaralanma Yanıtları Çalışması için Mikroakiskan Chips kullanma<em&gt; Drosophila</em&gt; Larva

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.

Mikroakışkan Tekniği Hücre deformabilitesi Probe

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.

Ticari Mikroskop Canlı Hücre Zarları Moleküler Difüzyon Kanunu Hızlı Floresans Görüntüleme Gönderen

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.

Spasticity ile Inme hastalarda streç refleks ölçümleri için test-retest ve Inter-Rater güvenilirlik geliştirmek için isokinetic robotik cihaz

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.

Canlı Mikroskopi Görüntüleme Altında 3D Hidrojellerin Kontrollü Suşu

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.

Enflamasyon Sırasında Lökosit-Endotelyal Hücre Etkileşimini İnceleyen Mikrofizyolojik Bir Sistem

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