Name: preparation of human myocardial tissue for long-term cultivation
Uploaded: 2022-06-02T14:10:00
Description: Watch this Scientific Journal Video about Preparation of Human Myocardial Tissue for Long-Term Cultivation at JoVE.com

연구는 DZHK 보조금 81Z0600207 (JH, PS 및 DM) 및 81X2600253 (AD 및 TS)이 자금을 지원했습니다.
저자들은 Claudia Fahney, Mei-Ping Wu 및 Matthias Semisch에게 셋업 준비와 조직 재배의 정기적 인 유지 보수에 대한 지원에 감사드립니다.

여기에 설명 된 실험을위한 조직 수집은 뮌헨 대학 (University of Munich)과 루르 대학 보훔 (Ruhr-University Bochum)의 기관 검토위원회 (Institutional Review Board)의 승인을 받았다. 연구는 헬싱키 선언 지침에 따라 수행되었습니다. 환자들은 조직 수집 전에 서면 정보에 입각 한 동의를했습니다.
1. 조직 획득
<ol><li>심장 이식 또는 심장 수술을받는 환자로부터 인간 조직을 얻습...

<ol>
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J., 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=Long-term+cultivation+of+human+atrial+myocardium.">Long-term cultivation of human atrial myocardium.</a> Frontiers in Physiology. 13, 839139 (2022).</li><li>Krane, M., 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=Sequential+defects+in+cardiac+lineage+commitment+and+maturation+cause+hypoplastic+left+heart+syndrome.">Sequential defects in cardiac lineage commitment and maturation cause hypoplastic left heart syndrome.</a> Circulation. 144 (17), 1409-1428 (2021).</li><li>Miller, J. 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(157), e60913 (2020).</li><li>Ou, Q., 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=Physiological+biomimetic+culture+system+for+pig+and+human+heart+slices.">Physiological biomimetic culture system for pig and human heart slices.</a> Circulation research. 125 (6), 628-642 (2019).</li><li>Watson, S. A., 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=Biomimetic+electromechanical+stimulation+to+maintain+adult+myocardial+slices+in+vitro.">Biomimetic electromechanical stimulation to maintain adult myocardial slices in vitro.</a> Nature Communications. 10 (1), 1-15 (2019).</li><li>Abu-Khousa, M., 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=The+degree+of+t-system+remodeling+predicts+negative+force-frequency+relationship+and+prolonged+relaxation+time+in+failing+human+myocardium.">The degree of t-system remodeling predicts negative force-frequency relationship and prolonged relaxation time in failing human myocardium.</a> Frontiers in Physiology. 11, 182 (2020).</li><li>Bojkova, D., 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=SARS-CoV-2+infects+and+induces+cytotoxic+effects+in+human+cardiomyocytes.">SARS-CoV-2 infects and induces cytotoxic effects in human cardiomyocytes.</a> Cardiovascular Research. 116 (14), 2207-2215 (2020).</li><li>Esfandyari, D. A. -. O., 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=MicroRNA-365+regulates+human+cardiac+action+potential+duration.">MicroRNA-365 regulates human cardiac action potential duration.</a> Nature Communications. 13 (1), 1-15 (2022).</li><li>Moretti, A., 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=Somatic+gene+editing+ameliorates+skeletal+and+cardiac+muscle+failure+in+pig+and+human+models+of+Duchenne+muscular+dystrophy.">Somatic gene editing ameliorates skeletal and cardiac muscle failure in pig and human models of Duchenne muscular dystrophy.</a> Nature Medicine. 26 (2), 207-214 (2020).</li><li>Pitoulis, F. G., 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=Remodelling+of+adult+cardiac+tissue+subjected+to+physiological+and+pathological+mechanical+load+in+vitro.">Remodelling of adult cardiac tissue subjected to physiological and pathological mechanical load in vitro.</a> Cardiovascular Research. 118 (3), 814-827 (2021).</li><li>Curtis, T. M., Scholfield, C. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nifedipine+blocks+Ca2++store+refilling+through+a+pathway+not+involving+L-type+Ca2++channels+in+rabbit+arteriolar+smooth+muscle.">Nifedipine blocks Ca2+ store refilling through a pathway not involving L-type Ca2+ channels in rabbit arteriolar smooth muscle.</a> The Journal of Physiology. 532 (3), 609-623 (2001).</li><li>de Weille, J. R., Schweitz, H., Maes, P., Tartar, A., Lazdunski, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calciseptine,+a+peptide+isolated+from+black+mamba+venom,+is+a+specific+blocker+of+the+L-type+calcium+channel.">Calciseptine, a peptide isolated from black mamba venom, is a specific blocker of the L-type calcium channel.</a> Proceedings of the National Academy of Sciences. 88 (6), 2437-2440 (1991).</li><li>Schleifer, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+molecular+modelling+study+of+the+calcium+channel+blockers+nifedipine+and+black+mamba+toxin+FS2.">Comparative molecular modelling study of the calcium channel blockers nifedipine and black mamba toxin FS2.</a> Journal of Computer-Aided Molecular Design. 11 (5), 491-501 (1997).</li><li>Thomas, G., Chung, M., Cohen, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+dihydropyridine+(Bay-K8644)+that+enhances+calcium+currents+in+guinea+pig+and+calf+myocardial+cells.+A+new+type+of+positive+inotropic+agent.">A dihydropyridine (Bay-K8644) that enhances calcium currents in guinea pig and calf myocardial cells. A new type of positive inotropic agent.</a> Circulation Research. 56 (1), 87-96 (1985).</li><li>Pitoulis, F. G., Watson, S. A., Perbellini, F., Terracciano, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myocardial+slices+come+to+age:+an+intermediate+complexity+in+vitro+cardiac+model+for+translational+research.">Myocardial slices come to age: an intermediate complexity in vitro cardiac model for translational research.</a> Cardiovascular Research. 116 (7), 1275-1287 (2020).</li><li>Watson, S. A., 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=Preparation+of+viable+adult+ventricular+myocardial+slices+from+large+and+small+mammals.">Preparation of viable adult ventricular myocardial slices from large and small mammals.</a> Nature Protocols. 12 (12), 2623-2639 (2017).</li></ol>

과거에는 심혈관 연구가 심근 세포 배양에 큰 발전을 이루었습니다. 그러나 손상되지 않은 기하학을 가진 심근 세포의 3D 배양은 아직 잘 확립되지 않았습니다. 심근 조직의 생체 외 배양에 적용된 이전의 프로토콜과 비교하여, 우리가 여기서 기술한 프로토콜은 조직의 생체내 환경과 더 밀접하게 닮았다. 또한, 사전 및 후부하의 적용은 더 많은 생체 모방 환경을 허용합니다. 우리는 ...

지난 10년 동안, 심근 세포의 시험관내 배양은 2D 및 3차원(3D) 기술에서부터 심장 심근세포 1,2,3으로 분화된 오가노이드 및 유도만능 줄기 세포의 사용에 이르기까지 큰 발전을 이루었다. Ex vivo 및 일차 세포 배양은 특히 유전 연구 및 약물 개발 4,5,6에 큰 가치를 지닌다. 인간 조직을 사용하면 결과의 번역 값이 향상됩니다. 그러나 손상되지 않은 기하학을 가진 심근 조직의 장기적인 3D 배양은 잘 확립되어 있지 않습니다. 손상되지 않은 기하학은 적절한 심장 기능, 다른 세포 간의 의사 소통 및 세포 - 매트릭스 상호 작용이 전제 조건이기 때문에 생체 내 조건을 모방하는 핵심 기능입니다. 심근 조직 재배는 다양한 발달 단계를 거쳤습니다. 생체외 심근 조직 배양의 성공률과 안정성은 처음에는 상당히 낮았지만, 최근의 접근법은 유망한 결과 7,8,9,10,11을 산출했다.
그 중에서도, Fischer 등은 인간 심근 조직의 생존력 및 수축성 성능이수년 7주 동안 생체외 세포 배양에서 유지될 수 있다는 것을 최초로 입증하였다. 그들의 기술은 외래 된 인간 심근에서 절단 된 얇은 조직 조각을 기반으로했으며, 이는 정의 된 생체 역학 조건과 지속적인 전기 자극을 제공하는 새로 개발 된 재배 챔버에 장착되었습니다. 이 배양 방법은 심근 조직의 생체 내 기능과 매우 유사하며 여러 독립적 인 연구 그룹2,12,13,14,15에 의해 재현되었습니다. 중요하게도, Fischer et al.이 사용하는 챔버는 또한 최대 4 개월 동안 개발 된 힘의 지속적인 등록을 가능하게하여 손상되지 않은 인간 심근에 대한 생리 학적 및 약리학 적 연구를위한 전례없는 기회를 열었습니다7.
유사한 기술이 다른 그룹에 의해 독립적으로 개발되어 인간, 래트, 돼지 및 토끼 심근7,10,11에 적용되었다. Pitoulis et al.은 수축 사이클 동안 정상적인 힘-길이 관계를 재현하는 보다 생리학적인 방법을 개발했지만, 고처리량 분석(16)에는 덜 적합하다. 이와 같이, 생체모방 재배의 일반적인 접근법은 동물 실험의 감소, 정제 및 대체(3R)를 위한 추가의 단계로 간주될 수 있다.
그러나 이러한 잠재력을 활용하려면 표준화된 절차, 높은 콘텐츠 분석 및 높은 처리량 수준이 필요합니다. 우리는 상용화 된 생체 모방 재배 시스템에서 살아있는 인간 심근의 자동화 된 슬라이싱과 시험관 내 유지 보수를 결합한 기술을 제시합니다 ( 재료 표 참조). 제안된 접근법으로, 단일 경막 심근 표본으로부터 생성될 수 있는 개별 슬라이스의 수는 처리 시간에 의해서만 제한된다. 충분한 크기와 품질 (3cm x 3cm)의 표본은 종종 자동화 된 vibratome으로 편리하게 절단되는 20-40 개의 조직 조각을 산출합니다. 이들 슬라이스는 시스템에 속하는 재배 챔버에 배치될 수 있다. 챔버는 전기 자극을 허용하며, 그 파라미터는 변조 될 수 있습니다 (즉, 펄스 지속 시간, 극성, 속도 및 전류), 챔버 내부의 스프링 와이어를 사용하여 사전 및 후부하의 조정. 각 슬라이스의 수축은 스프링 와이어에 부착 된 작은 자석의 움직임으로부터 등록되고 해석 가능한 그래프로 표시됩니다. 데이터는 항상 기록되고 자유롭게 사용 가능한 소프트웨어를 사용하여 분석 할 수 있습니다. 일정한 기준선 페이싱을 제외하고, 스케줄링된 프로토콜은 그들의 내화 기간, 자극 임계치, 포스트-일시정지-강화 및 힘-주파수 관계를 기능적으로 평가하기 위해 수행될 수 있다.
개별 심장에서 여러 심근 절편의 이러한 장기간의 생체 모방 배양은 인간과 동물 조직 모두에서 미래의 생체 외 연구를위한 길을 열어주고 심혈관 의학에서 치료 및 심장 독성 약물 효과에 대한 스크리닝을 용이하게합니다. 이미 다양한 실험적 접근법 2,12,13,15에 적용되었다. 여기에서는 인간 조직 준비에 대한 자세한 단계별 설명을 제공하고 자주 발생하는 재배 문제에 대한 솔루션을 제공합니다.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Chemicals</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose Low melting point</td>
			<td>Roth</td>
			<td>6351.2</td>
			<td></td>
		</tr>
		<tr>
			<td>Bay-K8644</td>
			<td>Cayman Chemical</td>
			<td>19988</td>
			<td></td>
		</tr>
		<tr>
			<td>BDM (2,3-Butanedione monoxime)</td>
			<td>Sigma</td>
			<td>B0753-1kg</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2*H2O</td>
			<td>Merck</td>
			<td>2382.1</td>
			<td></td>
		</tr>
		<tr>
			<td>Calciseptine</td>
			<td>Alomone Labs</td>
			<td>SPC-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose*H2O</td>
			<td>AppliChem</td>
			<td>A3730.0500</td>
			<td></td>
		</tr>
		<tr>
			<td>H2O</td>
			<td>BBraun</td>
			<td>3703452</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>AppliChem</td>
			<td>A1069.0500</td>
			<td></td>
		</tr>
		<tr>
			<td>Histoacryl</td>
			<td>BBraun</td>
			<td>1050052</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropanol 100%</td>
			<td>SAV LP GmbH</td>
			<td>UN1219</td>
			<td></td>
		</tr>
		<tr>
			<td>ITS-X-supplement</td>
			<td>Gibco</td>
			<td>5150056</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Merck</td>
			<td>1.04933.0500</td>
			<td></td>
		</tr>
		<tr>
			<td>Medium 199</td>
			<td>Gibco</td>
			<td>31150-022</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2*6H2O</td>
			<td>AppliChem</td>
			<td>A1036.0500</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma</td>
			<td>S5886-1KG</td>
			<td></td>
		</tr>
		<tr>
			<td>NaH2PO4*H2O</td>
			<td>Merck</td>
			<td>1.06346.0500</td>
			<td></td>
		</tr>
		<tr>
			<td>Nifedipine</td>
			<td>Sigma</td>
			<td>N7634-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin / streptomycin x100</td>
			<td>Sigma</td>
			<td>P0781-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>&#946;-Mercaptoethanol</td>
			<td>AppliChem</td>
			<td>A1108.0100</td>
			<td></td>
		</tr>
		<tr>
			<td>Laboratory equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Flow cabinet</td>
			<td>Thermo Scientific</td>
			<td>KS15</td>
			<td></td>
		</tr>
		<tr>
			<td>Frigomix waterpump and cooling + BBraun Thermomix BM</td>
			<td>BBraun</td>
			<td></td>
			<td>In-house made combination of cooling and heating solution.</td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Binder</td>
			<td>CB240</td>
			<td></td>
		</tr>
		<tr>
			<td>MyoDish bioreactor system</td>
			<td>InVitroSys GmbH</td>
			<td>MyoDish 1</td>
			<td>Myodish cultute system</td>
		</tr>
		<tr>
			<td>Vibratome</td>
			<td>Leica</td>
			<td>VT1200s</td>
			<td></td>
		</tr>
		<tr>
			<td>Water bath 37 degrees</td>
			<td>Haake</td>
			<td>SWB25</td>
			<td></td>
		</tr>
		<tr>
			<td>Water bath 80 degrees</td>
			<td>Daglef Patz KG</td>
			<td>7070</td>
			<td></td>
		</tr>
		<tr>
			<td>Materials</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>100 mL plastic single-use beaker</td>
			<td>Sarstedt</td>
			<td>75.562.105</td>
			<td></td>
		</tr>
		<tr>
			<td>Filtration unit, Steritop Quick Release</td>
			<td>Millipore</td>
			<td>S2GPT05RE</td>
			<td></td>
		</tr>
		<tr>
			<td>Needles 0.9 x 70 mm 20G</td>
			<td>BBraun</td>
			<td>4665791</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic triangles</td>
			<td></td>
			<td></td>
			<td>In-house made</td>
		</tr>
		<tr>
			<td>Razor Derby premium</td>
			<td>Derby Tokai</td>
			<td>B072HJCFK6</td>
			<td></td>
		</tr>
		<tr>
			<td>Razor Gillette Silver Blue</td>
			<td>Gillette</td>
			<td>7393560010170</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel disposable</td>
			<td>Feather</td>
			<td>02.001.30.020</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe 10 mL Luer tip BD Discardit</td>
			<td>BBraun</td>
			<td>309110</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue Culture Dish 10 cm</td>
			<td>Falcon</td>
			<td>353003</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue Culture Dish 3.5 cm</td>
			<td>Falcon</td>
			<td>353001</td>
			<td></td>
		</tr>
		<tr>
			<td>Tubes 50 mL</td>
			<td>Falcon</td>
			<td>352070</td>
			<td></td>
		</tr>
	</tbody>
</table>

preparation of human myocardial tissue for long-term cultivation

심근세포 배양은 2차원(2D) 세포 배양에서 iPSC 유래 오가노이드에 이르기까지 방대한 수의 발전을 이뤘다. 2019 년에는 심근 수축의 생체 내 상태에 접근하면서 인간 심장 샘플에서 얻은 심근 절편을 배양하는 생체 외 방법이 입증되었습니다. 이 샘플은 주로 심장 이식 또는 좌심실 보조 장치 배치에서 비롯됩니다. 비브라톰과 특별히 개발된 재배 시스템을 사용하여 300μm 두께의 슬라이스를 고정된 와이어와 스프링 와이어 사이에 배치하여 몇 주 동안 안정적이고 재현 가능한 재배가 가능합니다. 재배하는 동안 조각은 개별 설정에 따라 지속적으로 자극됩니다. 수축은 실시간으로 표시되고 기록 될 수 있으며 약리학 적 제제를 쉽게 적용 할 수 있습니다. 사용자-정의된 자극 프로토콜은 일시정지-강화, 자극 임계값, 힘-주파수 관계, 내화 기간과 같은 중요한 수축 파라미터를 평가하기 위해 스케줄링되고 수행될 수 있다. 더욱이, 상기 시스템은 보다 생리학적 재배를 위한 가변 사전-후 하중 설정을 가능하게 한다.
여기에서, 우리는 상업적 생체 모방 재배 용액을 사용하여 인간 좌심실 심근 절편의 성공적인 장기 배양을 생성하는 방법에 대한 단계별 가이드를 제시합니다.

심근 조각의 수축은 재배 챔버를 해당 커넥터에 삽입 한 후 컴퓨터 화면에 표시되었습니다 (그림 3). 인간 심근 조각의 수축은 자극 즉시 시작되었습니다. 조각은 5-10 분 동안 과도하게 수축되었습니다. 이것은 손상된 조직 분획의 강장제 수축으로 인한 이완기 힘의 증가로 나타났습니다. 이 과정은 1-1.5 h 내에서 다양한 정도로 되돌렸다. 안정화 후, 인간 LV 조직 절편은 자극?...

Watch this Scientific Journal Video about Preparation of Human Myocardial Tissue for Long-Term Cultivation at JoVE.com

Preparation of Human Myocardial Tissue for Long-Term Cultivation

우리는 인간 심실 심근 조직의 생체 외 배양을 위한 프로토콜을 제시한다. 수축력 및 동역학에 대한 상세한 분석뿐만 아니라 생체 내 생리 환경을보다 면밀히 모방하기 위해 사전 및 후부하의 적용을 허용합니다.

장기 재배를 위한 인간 심근 조직의 제조

Cardiomyocyte cultivation has seen a vast number of developments, ranging from two-dimensional (2D) cell cultivation to iPSC derived organoids. In 2019, ...

이 프로토콜을 사용하여, 인간 좌심실 조직 절편은 생체모방 챔버에서 생체외 배양될 수 있다. 사전 및 후부하의 적용은 생리 환경의 유사성을 향상시킵니다. 이 기술은 조직 수축의 지속적인 등록을 허용합니다.사용자 정의 자극 프로토콜은 일시정지 후 강화, 자극 임계값, 힘-주파수 관계, 내화 기간과 같은 중요한 수축 파라미터의 평가를 허용한다. 이 설정을 사용하여 심근 조각의 장기간 재배는 심혈관 의학에서 치료 및 심장 독성 약물 효과에 대한이 스크리닝을 용이하게하여 향후 생체 외 연구를위한 길을 열어 줄 것입니다. 시작하려면 배양 챔버와 흑연 전극을 10 % 이소프로판올 용액 1 리터에 담그고 밤새 교반하십시오.다음날 챔버를 100 % 이소프로판올 용액으로 3 분 동안 옮긴 다음 챔버 및 흑연 전극을 층류 후드 하에서 공기 건조시킵니다. 로커의 사용 가능한 위치에 따라 회로 기판을 각 챔버에 부착하십시오. 제조업체의 지침에 따라 회로 기판에 두 개의 흑연 전극을 놓은 다음 감염을 예방하기 위해 챔버에 35mm 페트리 접시 뚜껑을 놓습니다.그런 다음 절단 트레이를 슬라이싱 버퍼로 최대 90 ~ 95 %까지 채 웁니다. 조직 샘플을 차가운 슬라이싱 버퍼로 채워진 100 밀리미터 페트리 접시에 옮기고 접시를 섭씨 4도의 냉각 플레이트에 놓습니다. 핀셋으로 심내막을 잡고 심내막 섬유주를 제거한 다음 가위를 사용하여 약 3mm의 심내막 조직을 잘라냅니다.절단된 조직 샘플, 심내막 측면을 정사각형 위치에 고정된 네 개의 0.9x70밀리미터 20게이지 바늘을 사용하여 2x2센티미터 고무 패치까지 고정시킨다. 각 바늘 팁의 대각선 가장자리가 안쪽을 향하고 있는지 확인하여 고정력을 강화하고 심근 손상을 방지하십시오. 메스를 사용하여 네 개의 바늘 사각형 외부의 모든 과도한 조직을 잘라냅니다.핀셋을 사용하여 트리밍된 샘플을 멸균된 조직 조각에 10초 동안 올려 놓고 과도한 슬라이싱 버퍼를 제거합니다. 다음으로, 수조에서 아가로스 주사기를 제거하고 샘플을 아가로스에 침수시킨다. 아가로스를 냉각판에서 다섯 분 동안 응고시키십시오.샘플의 심내막 측면은 아가로스에서 볼 수 있어야합니다. 핀셋을 사용하여 아가로스에 포함 된 샘플의 심외경면을 접착 된 부위 위에 놓은 다음 아가로스를 자르거나 손상시키지 않고 무딘 도구로 상단에서 아가로스 함유 샘플을 부드럽게 누릅니다. 접착제가 1 분 동안 굳어지게하십시오.진동 진폭을 1mm로, 초기 절삭 속도를 초당 0.07mm로, 슬라이스 두께를 300미크론으로 설정합니다. 재배 시스템을 컴퓨터에 연결 한 후 해당 소프트웨어 프로그램을 시작하십시오. 로커 속도를 60rpm으로 설정하고 자극 매개 변수를 미리 설정합니다.인간의 심장 조각의 경우, 표준 자극을 50 밀리암페어 또는 3 밀리 초 양의 전류, 1 밀리 초 일시 중지 및 분당 30 비트 또는 bpm의 간격 속도로 반전 전류의 3 밀리 초 펄스로 구성된 이단계 임펄스로 설정 한 다음 소프트웨어의 전극 표시기를 확인하고 재배 챔버의 전극이 올바르게 작동하는지 확인하십시오. 핀셋을 사용하여 아가로스를 조직에서 분리하십시오. 조직을 만지지 말고 조직의 손상이 배양의 성공률을 떨어 뜨릴 수 있으므로 조심스럽게 다루십시오.두 개의 플라스틱 삼각형을 샘플에 부착하려면 멸균 된 Petri 접시 뚜껑에 1 마이크로 리터의 접착제를 놓습니다. 후크 핀셋을 사용하여 오토클레이브 플라스틱 삼각형 하나를 집어 들으십시오. 삼각형의 앞 가장자리를 접착제에 빠르게 담그고 삼각형을 심근 세포 정렬에 수직인 샘플에 붙여 넣으십시오.다른 삼각형에 대해 반복합니다. 메스를 사용하여 삼각형 너비를 초과하는 조직을 트리밍하고 두 개의 장착된 삼각형이 있는 슬라이스를 슬라이스 버퍼가 있는 절단 트레이에 다시 놓습니다. 배지가 채워진 배양 챔버를 인큐베이터로부터 제거한다.준비된 슬라이스 하나를 선택하고 각 핀에 삼각형 하나를 연결하여 챔버에 삽입합니다. 장착 핀 사이의 거리를 샘플 크기로 조정합니다. 샘플이 배지에 잠겨 있는지 확인하십시오.접시를 로커에 놓은 후 컴퓨터 화면의 해당 그래프의 기준선이 더 이상 변경되지 않을 때까지 조정 나사를 시계 반대 방향으로 돌려 프리로드를 줄인 다음 조정 나사를 시계 방향으로 돌려 프리로드 또는 장력을 조심스럽게 높입니다. 강성이 높은 챔버의 경우, 그래프의 해당 기준선이 1밀리뉴턴 프리로드에 해당하는 1, 000 ~ 1, 200 단위만큼 증가할 때까지 계속하십시오. 신선한 재배 배지를 준비한 후, 배지를 섭씨 37도의 수조 또는 열풍 배양기에서 30 내지 45분 동안 미리 가온한다.챔버에서 매체를 제거하고 챔버에 약 0.8 밀리리터를 남긴 다음 동일한 챔버에 1.6 밀리리터의 신선한 배지를 추가하여 챔버 당 2.4 밀리리터의 총 부피를 만듭니다. 마지막으로, 챔버의 덮개를 다시 놓고 재배 챔버를 각각의 위치에 놓습니다. 전형적인 자극 동안 다섯 개의 심근 슬라이스의 수축에 대한 판독은 일시 중지 후 강화, 자극 임계 값, 힘 - 주파수 관계 및 난치성 기간의 네 가지 별개의 섹션으로 구성되었습니다.대조군과 비교하여, 칼슘 길항제인 니페디핀 및 칼시셉틴으로 처리된 슬라이스의 수축력은 10분 이내에 감소하였다. 대조적으로, 전압-게이팅된 칼슘 채널 작용제인 Bay-K8644는 수축력을 증가시켰다. 대조군 및 처리된 슬라이스의 일시정지 후 강화를 사르코플라스마 망상체로부터의 세포내 칼슘 방출에 대해 평가하였다.컨트롤 조각에 변경 내용이 표시되지 않았습니다. 칼시셉틴과 니페디핀의 존재 하에서, L형 칼슘 채널의 억제는 50초의 정지 후 첫 번째 수축의 강화로 이어졌고, 이는 전체 수축성에 대한 세포내 칼슘 방출의 더 높은 상대적 기여를 반영한다. 반대 효과는 L형 칼슘 채널을 통해 세포외 칼슘의 진입을 자극하는 Bay-K8644에서 관찰되었다.힘-주파수 관계 분석에서, 제어 슬라이스에서 어떠한 변화도 관찰되지 않았다. 칼시셉틴 처리는 치료 전후 데이터를 비교할 때 자극 빈도의 증가시 자극을 따르는 슬라이스의 능력을 변화시키지 않았다. 칼시셉틴과 비교했을 때, 니페디핀은 더 높은 페이싱 속도에서 수축성의 증가를 방지하고 80bpm에서 최대 포획률을 감소시켰다.Bay-K8644에서는 매우 낮은 자극 주파수에서 수축력 증가가 관찰되었습니다. 그러나, 50 bpm보다 높은 주파수에서, 수축력은 전처리 조건에서보다 낮았다. 적출 된 조직은 4 도의 심장 흉막으로 신속하게 옮겨야합니다.슬라이스 후 플라스틱 삼각형은 섬유 방향에 수직으로 부착되어야합니다. 프리로드는 1500밀리뉴턴을 초과해서는 안 됩니다. 생체 모방 슬라이스 배양은 연구자가 성인 인간 심근의 재생 및 복구를 연구하기위한 세포 기반 치료법뿐만 아니라 유전자 조작을 활용하는 데 도움이 될 수 있습니다.

preparation-of-human-myocardial-tissue-for-long-term-cultivation

Research

JoVE Journal

Medicine

Corneal Donor Tissue Preparation for Endothelial Keratoplasty

Over the past ten years, corneal transplantation surgical techniques have undergone revolutionary changes1,2. Since its inception, traditional full thickness corneal transplantation has been the treatment to restore sight in those limited by corneal disease. Some disadvantages to this approach include a high degree of post-operative astigmatism, lack of predictable refractive outcome, and disturbance to the ocular surface. The development of Descemet's stripping endothelial keratoplasty (DSEK), transplanting only the posterior corneal stroma, Descemet's membrane, and endothelium, has dramatically changed treatment of corneal endothelial disease. DSEK is performed through a smaller incision; this technique avoids 'open sky' surgery with its risk of hemorrhage or expulsion, decreases the incidence of postoperative wound dehiscence, reduces unpredictable refractive outcomes, and may decrease the rate of transplant rejection3-6.
Initially, cornea donor posterior lamellar dissection for DSEK was performed manually1 resulting in variable graft thickness and damage to the delicate corneal endothelial tissue during tissue processing. Automated lamellar dissection (Descemet's stripping automated endothelial keratoplasty, DSAEK) was developed to address these issues. Automated dissection utilizes the same technology as LASIK corneal flap creation with a mechanical microkeratome blade that helps to create uniform and thin tissue grafts for DSAEK surgery with minimal corneal endothelial cell loss in tissue processing.
Eye banks have been providing full thickness corneas for surgical transplantation for many years. In 2006, eye banks began to develop methodologies for supplying precut corneal tissue for endothelial keratoplasty. With the input of corneal surgeons, eye banks have developed thorough protocols to safely and effectively prepare posterior lamellar tissue for DSAEK surgery. This can be performed preoperatively at the eye bank. Research shows no significant difference in terms of the quality of the tissue7 or patient outcomes8,9 using eye bank precut tissue versus surgeon-prepared tissue for DSAEK surgery. For most corneal surgeons, the availability of precut DSAEK corneal tissue saves time and money10, and reduces the stress of performing the donor corneal dissection in the operating room. In part because of the ability of the eye banks to provide high quality posterior lamellar corneal in a timely manner, DSAEK has become the standard of care for surgical management of corneal endothelial disease.
The procedure that we are describing is the preparation of the posterior lamellar cornea at the eye bank for transplantation in DSAEK surgery (Figure 1).

Endothelial corneal transplantation is a surgical technique for treatment of posterior corneal diseases. Mechanical microkeratome dissection to prepare tissue results in thinner, more symmetric grafts with less endothelial cell loss and improved outcomes. Dissections can be performed at the eye bank prior to corneal transplantation surgery.

내피 Keratoplasty을위한 각막 기증자 조직 준비

Over the past ten years, corneal transplantation surgical techniques have undergone revolutionary changes1,2. Since its inception, traditional full ...

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Working with Human Tissues for Translational Cancer Research

Medical research for human benefit is greatly impeded by the necessity for human tissues and subjects. However, upon obtaining consent for human specimens, precious samples must be handled with the greatest care in order to ensure integrity of organs, tissues, and cells to the highest degree. Unfortunately, tissue processing by definition requires extraction of tissues from the host, a change which can cause great cellular stress and have major repercussions on subsequent analyses. These stresses could result in the specimen being no longer representative of the site from which it was retrieved. Therefore, a strict protocol must be adhered to while processing these specimens to ensure representativeness. The desired assay(s) must also be taken into consideration in order to ensure that an optimal technique is used for sample processing. Outlined here is a protocol for tissue retrieval, processing and various analyses which may be performed on processed tissue in order to maximize downstream production from limited tissue samples.

Translational cancer research is dependent on extraction of human tissues. Much work has gone into optimizing extraction methods for ex vivo analysis. Here, we describe tissue processing methods allowing for maximal data output from limited samples.

번역 상 암 연구를위한 인체 조직에 대한 작업

Medical research for human benefit is greatly impeded by the necessity for human tissues and subjects. However, upon obtaining consent for human ...

Long-Term Catheterization of the Intestinal Lymph Trunk and Collection of Lymph in Neonatal Pigs

Catheterization of the intestinal lymph trunk in neonatal pigs is a technique allowing for the long-term collection of large quantities of intestinal (central) efferent lymph. Importantly, the collection of central lymph from the intestine enables researchers to study both the mechanisms and lipid constitutes associated with lipid metabolism, intestinal inflammation and cancer metastasis, as well as cells involved in immune function and immunosurveillance. A ventral mid-line surgical approach permits excellent surgical exposure to the cranial abdomen and relatively easy access to the intestinal lymph trunk vessel that lies near the pancreas and the right ventral segment of the portal vein underneath the visceral aspect of the right liver lobe. The vessel is meticulously dissected and released from the surrounding fascia and then dilated with sutures allowing for insertion and subsequent securing of the catheter into the vessel. The catheter is exteriorized and approximately 1 L/24 hr of lymph is collected over a 7 day period. While this technique enables the collection of large quantities of central lymph over an extended period of time, the success depends on careful surgical dissection, tissue handling and close attention to proper surgical technique. This is particularly important with surgeries in young animals as the lymph vessels can easily tear, potentially leading to surgical and experimental failure. The video demonstrates an excellent surgical technique for the collection of intestinal lymph.

We present a surgical procedure to catheterize the intestinal lymph trunk in neonatal pigs to collect large quantities of lipid metabolism components from efferent lymph.

신생아 돼지에서 림프의 창자 림프 트렁크와 컬렉션의 장기 도관

Catheterization of the intestinal lymph trunk in neonatal pigs is a technique allowing for the long-term collection of large quantities of intestinal ...

Surgical Placement of Catheters for Long-term Cardiovascular Exercise Testing in Swine

This protocol describes the surgical procedure to chronically instrument swine and the procedure to exercise swine on a motor-driven treadmill. Early cardiopulmonary dysfunction is difficult to diagnose, particularly in animal models, as cardiopulmonary function is often measured invasively, requiring anesthesia. As many anesthetic agents are cardiodepressive, subtle changes in cardiovascular function may be masked. In contrast, chronic instrumentation allows for measurement of cardiopulmonary function in the awake state, so that measurements can be obtained under quiet resting conditions, without the effects of anesthesia and acute surgical trauma. Furthermore, when animals are properly trained, measurements can also be obtained during graded treadmill exercise.
Flow probes are placed around the aorta or pulmonary artery for measurement of cardiac output and around the left anterior descending coronary artery for measurement of coronary blood flow. Fluid-filled catheters are implanted in the aorta, pulmonary artery, left atrium, left ventricle and right ventricle for pressure measurement and blood sampling. In addition, a 20 G&#160;catheter is positioned in the anterior interventricular vein to allow coronary venous blood sampling.
After a week of recovery, swine are placed on a motor-driven treadmill, the catheters are connected to pressure and flow meters, and swine are subjected to a five-stage progressive exercise protocol, with each stage lasting 3 min. Hemodynamic signals are continuously recorded and blood samples are taken during the last 30 sec of each exercise stage.
The major advantage of studying chronically instrumented animals is that it allows serial assessment of cardiopulmonary function, not only at rest but also during physical stress such as exercise. Moreover, cardiopulmonary function can be assessed repeatedly during disease development and during chronic treatment, thereby increasing statistical power and hence limiting the number of animals required for a study.

Here we present a protocol to assess cardiopulmonary function in awake swine, at rest and during graded treadmill exercise. Chronic instrumentation allows for repeated hemodynamic measurements uninfluenced by cardiodepressive anesthetic agents.

돼지의 장기 심장 혈관 운동 테스트를위한 카테터의 외과 배치

This protocol describes the surgical procedure to chronically instrument swine and the procedure to exercise swine on a motor-driven treadmill. Early ...

Long-term Blood Pressure Measurement in Freely Moving Mice Using Telemetry

During the development of new vasoactive agents, arterial blood pressure monitoring is crucial for evaluating the efficacy of the new proposed drugs. Indeed, research focusing on the discovery of new potential therapeutic targets using genetically altered mice requires a reliable, long-term assessment of the systemic arterial pressure variation. Currently, the gold standard for obtaining long-term measurements of blood pressure in ambulatory mice uses implantable radio-transmitters, which require&#160;artery cannulation. This technique eliminates the need for tethering, restraining, or anesthetizing the animals which introduce stress and artifacts during data sampling. However, arterial blood pressure monitoring in mice via catheterization can be rather challenging due to the small size of the arteries. Here we present a step-by-step guide to illustrate the crucial key passages for a successful subcutaneous implantation of radio-transmitters and carotid artery cannulation in mice. We also include examples of long-term blood pressure activity taken from freely moving mice after a period of post-surgery recovery. Following this procedure will allow reliable direct blood pressure recordings from multiple animals simultaneously.

The goal of this protocol is to assess systemic blood pressure in conscious freely moving mice using implantable radio-telemetry devices.

텔레 메 트리를 사용하여 자유롭게 이동 마우스의 장기 혈압 측정

During the development of new vasoactive agents, arterial blood pressure monitoring is crucial for evaluating the efficacy of the new proposed drugs. ...

3D Whole-heart Myocardial Tissue Analysis

Cardiac regenerative therapies aim to protect and repair the injured heart in patients with ischemic heart disease. By injecting stem cells or other biologicals that enhance angio- or vasculogenesis into the infarct border zone (IBZ), tissue perfusion is improved, and the myocardium can be protected from further damage. For maximum therapeutic effect, it is hypothesized that the regenerative substance is best delivered to the IBZ. This requires accurate injections and has led to the development of new injection techniques. To validate these new techniques, we have designed a validation protocol based on myocardial tissue analysis. This protocol includes whole-heart myocardial tissue processing that enables detailed two-dimensional (2D) and three-dimensional (3D) analysis of the cardiac anatomy and intramyocardial injections. In a pig, myocardial infarction was created by a 90-min occlusion of the left anterior descending coronary artery. Four weeks later, a mixture of a hydrogel with superparamagnetic iron oxide particles (SPIOs) and fluorescent beads was injected in the IBZ using a minimally-invasive endocardial approach. 1 h after the injection procedure, the pig was euthanized, and the heart was excised and embedded in agarose (agar). After the solidification of the agar, magnetic resonance imaging (MRI), slicing of the heart, and fluorescence imaging were performed. After image post-processing, 3D analysis was performed to assess the IBZ targeting accuracy. This protocol provides a structured and reproducible method for the assessment of the targeting accuracy of intramyocardial injections into the IBZ. The protocol can be easily used when the processing of scar tissue and/or validation of the injection accuracy of the whole heart is desired.

This protocol describes a novel method for the 3D comparison of whole-heart myocardial tissue with MRI. This is designed for the accurate assessment of intramyocardial injections in the infarct border zone of a chronic porcine model of myocardial infarction.

3D 전체 심장 심근 조직 분석

Cardiac regenerative therapies aim to protect and repair the injured heart in patients with ischemic heart disease. By injecting stem cells or other ...

Improvement of a Closed Chest Porcine Myocardial Infarction Model by Standardization of Tissue and Blood Sampling Procedures

Myocardial ischemia reperfusion (I/R) injury contributes to almost half of the necrotic area after myocardial infarction. To date there is no approved drug to prevent or reduce myocardial I/R injury. The study and understanding of the pathophysiological mechanisms of myocardial I/R injury is essential to develop successful treatments. Large animal experiments are an important step in translational methods. The porcine model of acute myocardial infarction has been established and described by ourselves and others. We aimed to further improve the value of the model by focusing in detail on the sampling techniques for use in future experiments. Furthermore, we emphasize small but important steps that can affect the quality of the final results. To mimic the clinical situation of myocardial I/R injury, a percutaneous coronary intervention (PCI) catheter was inserted into the left anterior descending coronary artery (LAD) of an anesthetized pig. &#176;&#176;&#176;This model mimics acute myocardial infarction and PCI treatment in humans with the possibility of accurately determining the area at risk as well as the necrotic- and viable ischemic tissue. Here the model was used to investigate the effect of a bicyclic peptide inhibitor of FXIIa. The model can also be modified to allow longer reperfusion times to study later effects of myocardial infarction.

Here we demonstrate a protocol to standardize sampling procedures of an established porcine model of acute myocardial infarction in order to increase its translational value in the understanding of the pathophysiology of myocardial ischemia/reperfusion injury and to test novel drug candidates.

조직 및 혈액 샘플링 절차의 표준화에 의해 닫힌된 가슴 돼지 심근 경색 모델의 개선

Myocardial ischemia reperfusion (I/R) injury contributes to almost half of the necrotic area after myocardial infarction. To date there is no approved ...

Analyzing Long-Term Electrocardiography Recordings to Detect Arrhythmias in Mice

Arrhythmias are common, affecting millions of patients worldwide. Current treatment strategies are associated with significant side effects and remain ineffective in many patients. To improve patient care, novel and innovative therapeutic concepts causally targeting arrhythmia mechanisms are needed. To study the complex pathophysiology of arrhythmias, suitable animal models are necessary, and mice have been proven to be ideal model species to evaluate the genetic impact on arrhythmias, to investigate fundamental molecular and cellular mechanisms, and to identify potential therapeutic targets.
Implantable telemetry devices are among the most powerful tools available to study electrophysiology in mice, allowing continuous ECG recording over a period of several months in freely moving, awake mice. However, due to the huge number of data points (&gt;1 million QRS complexes per day), analysis of telemetry data remains challenging. This article describes a step-by-step approach to analyze ECGs and to detect arrhythmias in long-term telemetry recordings using the software, Ponemah, with its analysis modules, ECG Pro and Data Insights, developed by Data Sciences International (DSI). To analyze basic ECG parameters, such as heart rate, P wave duration, PR interval, QRS interval, or QT duration, an automated attribute analysis was performed using Ponemah to identify P, Q, and T waves within individually adjusted windows around detected R waves. 
Results were then manually reviewed, allowing adjustment of individual annotations. The output from the attribute-based analysis and the pattern recognition analysis was then used by the Data Insights module to detect arrhythmias. This module allows an automatic screening for individually defined arrhythmias within the recording, followed by a manual review of suspected arrhythmia episodes. The article briefly discusses challenges in recording and detecting ECG signals, suggests strategies to improve data quality, and provides representative recordings of arrhythmias detected in mice using the approach described above.

Here we present a step-by-step protocol for a semiautomated approach to analyze murine long-term electrocardiography (ECG) data for basic ECG parameters and common arrhythmias. Data are obtained by implantable telemetry transmitters in living and awake mice and analyzed using Ponemah and its analysis modules.

마우스의 부정맥을 감지하기 위한 장기 심전도 기록 분석

Arrhythmias are common, affecting millions of patients worldwide. Current treatment strategies are associated with significant side effects and remain ...

Technique for Obtaining Mesenchymal Stem Cell from Adipose Tissue and Stromal Vascular Fraction Characterization in Long-Term Cryopreservation

Human mesenchymal stem cells derived from adipose tissue have become increasingly attractive as they show appropriate features and are an accessible source for regenerative clinical applications. Different protocols have been used to obtain adipose-derived stem cells. This article describes different steps of an improved time-saving protocol to obtain a more significant amount of ADSC, showing how to cryopreserve and thaw ADSC to obtain viable cells for culture expansion. One hundred milliliters of lipoaspirate were collected, using a 26 cm three-hole and 3 mm caliber syringe liposuction, from the abdominal area of nine patients who subsequently underwent elective abdominoplasty. The stem cells isolation was carried out with a series of washes with Dulbecco&#39;s Phosphate Buffered Saline (DPBS) solution supplemented with calcium and the use of collagenase. Stromal Vascular Fraction (SVF) cells were cryopreserved, and their viability was checked by immunophenotyping. The SVF cellular yield was 15.7 x 105 cells/mL, ranging between 6.1-26.2 cells/mL. Adherent SVF cells reached confluence after an average of 7.5 (&#177;4.5) days, with an average cellular yield of 12.3 (&#177; 5.7) x 105 cells/mL. The viability of thawed SVF after 8 months, 1 year, and 2 years ranged between 23.06%-72.34% with an average of 47.7% (&#177;24.64) with the lowest viability correlating with cases of two-year freezing. The use of DPBS solution supplemented with calcium and bag resting times for fat precipitation with a shorter time of collagenase digestion resulted in an increased stem cell final cellular yield. The detailed procedure for obtaining high yields of viable stem cells was more efficient regarding time and cellular yield than the techniques from previous studies. Even after a long period of cryopreservation, viable ADSC cells were found in the SVF.

The present protocol describes an improved methodology for ADSC isolation resulting in a tremendous cellular yield with time gain compared to the literature. This study also provides a straightforward method for obtaining a relatively large number of viable cells after long-term cryopreservation.

지방 조직에서 중간엽 줄기세포를 얻는 기술 및 장기 냉동 보존에서 기질 혈관 분획 특성 분석

Human mesenchymal stem cells derived from adipose tissue have become increasingly attractive as they show appropriate features and are an accessible ...

Long-Term Continuous Measurement of Renal Blood Flow in Conscious Rats

The kidneys play a crucial role in maintaining the homeostasis of body fluids. The regulation of renal blood flow (RBF) is essential to the vital functions of filtration and metabolism in kidney function. Many acute studies have been carried out in anesthetized animals to measure RBF under various conditions to determine mechanisms responsible for the regulation of kidney perfusion. However, for technical reasons, it has not been possible to measure RBF continuously (24 h/day) in unrestrained unanesthetized rats over prolonged periods. These methods allow the continuous determination of RBF over many weeks while also simultaneously recording blood pressure (BP) with implanted catheters (fluid-filled or by telemetry). RBF monitoring is carried out with rats placed in a circular servo-controlled rat cage that enables the unrestrained movement of the rat throughout the study. At the same time, the tangling of cables from the flow probe and arterial catheters is prevented. Rats are first instrumented with an ultrasonic flow probe placement on the left renal artery and an arterial catheter implanted in the right femoral artery. These are routed subcutaneously to the nape of the neck, and connected to the flowmeter and pressure transducer, respectively, to measure RBF and BP. Following surgical implantation, rats are immediately placed in the cage to recover for at least one week and stabilize the ultrasonic probe recordings. Urine collection is also feasible in this system. The surgical and post-surgical procedures for continuous monitoring are demonstrated in this protocol.

The present protocol describes a long-term continuous measurement of renal blood flow in conscious rats and simultaneously recording blood pressure with implanted catheters (fluid-filled or by telemetry).