A DIC based technique to measure the contraction of a skeletal muscle engineered tissue

Tissue engineering is a multidisciplinary science based on the application of engineering approaches to biologic tissue formation. Engineered tissue internal organization represents a key aspect to increase biofunctionality before transplant and, as regarding skeletal muscles, the potential of generating contractile forces is dependent on the internal fiber organization and is reflected by some macroscopic parameters, such as the spontaneous contraction. Here we propose the application of digital image correlation (DIC) as an independent tool for an accurate and noninvasive measurement of engineered muscle tissue spontaneous contraction. To validate the proposed technique we referred to the X-MET, a promising 3-dimensional model of skeletal muscle. The images acquired through a high speed camera were correlated with a custom-made algorithm and the longitudinal strain predictions were employed for measuring the spontaneous contraction. The spontaneous contraction reference values were obtained by studying the force response.The relative error between the spontaneous contraction frequencies computed in both ways was always lower than 0.15%. In conclusion, the use of a DIC based systemallows for an accurate and noninvasive measurement of biological tissues’ spontaneous contraction, in addition to the measurement of tissue strain field on any desired region of interest during electrical stimulation

A DIC Based Technique to Measure the Contraction of a Skeletal Muscle Engineered Tissue

Tissue engineering is a multidisciplinary science based on the application of engineering approaches to biologic tissue formation. Engineered tissue internal organization represents a key aspect to increase biofunctionality before transplant and, as regarding skeletal muscles, the potential of generating contractile forces is dependent on the internal fiber organization and is reflected by some macroscopic parameters, such as the spontaneous contraction. Here we propose the application of digital image correlation (DIC) as an independent tool for an accurate and noninvasive measurement of engineered muscle tissue spontaneous contraction. To validate the proposed technique we referred to the X-MET, a promising 3-dimensional model of skeletal muscle. The images acquired through a high speed camera were correlated with a custom-made algorithm and the longitudinal strain predictions were employed for measuring the spontaneous contraction. The spontaneous contraction reference values were obtained by studying the force response. The relative error between the spontaneous contraction frequencies computed in both ways was always lower than 0.15%. In conclusion, the use of a DIC based system allows for an accurate and noninvasive measurement of biological tissues' spontaneous contraction, in addition to the measurement of tissue strain field on any desired region of interest during electrical stimulation

Functional Human Cell-Based Cardiac Tissue Model with Contraction Force Measurements

Sydämeen kohdistuvat lääkkeiden haittavaikutukset ovat yksi suurimpia syitä lääkeainekandidaattien hylkäämiselle sekä jo markkinoille vietyjen lääkkeiden poisvedoille. Nykyiset menetelmät lääkkeiden turvallisuuden ja tehokkuuden testaamiseen eivät ennusta lääkkeiden vaikutuksia ihmiselle riittävän tarkasti. Koska sydänten toiminnassa on lajikohtaisia eroja, eläinkokeissa ei välttämättä tunnisteta kaikkia ihmisen sydämelle haitallisia aineita. Tätä varten tarvitaan toiminnaltaan mahdollisimman hyvin ihmisen sydänkudosta vastaavia ihmissolupohjaisia sydänkudosmalleja. Tämän väitöskirjan tavoitteena oli kehittää toiminnallinen sydänkudosmalli, joka mallintaa aikuisen ihmisen sydäntä, sekä yhdistää tähän malliin sykintävoiman mittaus. Tässä työssä kehitetty sydänkudosmalli koostuu ihmisen rasvan kantasoluista (hASC) ja ihmisen napanuoran laskimon endoteelisoluista (HUVEC) muodostuvasta verisuoniverkostosta, jonka päälle kasvatetaan ihmisen indusoiduista kantasoluist (hiPSC) erilaistetut sydänlihassolut. Tämä sydänkudosmalli karakterisoitiin rakenteellisesti, geenien ilmentymisen tasolla ja toiminnallisesti. Sydänkudosmallien sykintävoimanmittaukseen kehitettiin yksi- ja kaksisuuntaisia pietsosähköisiä sensoreita. Tulosten perusteella yhteisviljelmä verisuonipohjan kanssa parantaa sydänlihassolujen kypsymistä edistämällä niiden järjestäytymistä ja morfologiaa, sarkomeerirakennetta ja solu-solu-liitoksia. Myös sydänlihassolujen geenien ilmentymisessä oli vastaavuuksia aikuisen sydämeen. Toiminnallinen karakterisointi tunnetuilla sydämeen vaikuttavilla lääkeaineilla osoitti mallin tunnistavan tarkasti aineiden vaikutuksia. Kehitetyt pietsosähköiset voima-anturit soveltuivat sydänmallien sykintävoiman mittaamiseen. Antureiden todettiin pystyvän mittaamaan sekä voimaa eri mekanismein lisäävien että sitä vähentävien aineiden vaikutuksia. Yhteenvetona voidaan todeta, että työssä kehitetty sydänkudosmalli jäljittelee sydänlihaskudoksen rakennetta ja toimintaa. Malli sopii testaamaan ihmisen sydämeen kohdistuvia akuutteja lääkeaineiden haittavaikutuksia ja sydänlääkkeiden tehoa. Kehitettyyn sydänkudosmalliin liitetyllä pietsosähköisellä voima-anturilla on potentiaalia voimaankohdistuvien lääkeainevaikutusten testaamiseen.Adverse cardiac effects are a major reason for drug attrition during drug development and for post-approval market withdrawals. Therefore, drug development would greatly benefit from tests that better predict human cardiac function. Due to intrinsic species-to-species differences in the functionality of the heart, nonclinical animal testing does not fully represent the effects of the drugs on human. Thus, there is a need for reliable, human cell -based standardised in vitro models for cardiotoxicity and drug efficacy testing. The aim of this thesis was to develop a functional human cell -based cardiac tissue model that mimics the adult human heart and to develop a contraction force measurement system for measuring the cardiac contractility of the cardiac tissue model. The cardiac tissue model that was optimised in this thesis consisted of human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes that are cocultured with preformed human adipose stromal cells (hASC) and human umbilical vein endothelial cells (HUVEC) vascular-like networks. The model was characterized structurally, in gene expression levels, and functionally. For measuring the cardiac contraction force, piezoelectric cantilever sensors with single axis and dual axis sensor designs were developed. The cell culture method was adjusted according to the sensor designs. The functionality of the cardiac tissue model and contraction force measurement technology were confirmed by known inotropic drug exposures. The results show that the coculture with the vascular-like networks improved the cardiomyocyte maturity and the tissue like structure of the model. The cardiomyocytes in the model showed improved organization and morphology, well- developed sarcomeres, and cell-cell connections. The gene expression of the cardiac tissue model also showed characteristics of the adult human heart. The functional characterization with known reference compounds showed that the model had good predictivity with high correlation to human data. The developed piezoelectric contraction force sensors were suitable for measuring the contraction force of cardiac tissue constructs. Both positive and negative inotropic effects including different mechanisms were measurable in the model with the system. In conclusion, the developed cardiac tissue model mimics the myocardium structure and functionality. The model is suitable for testing cardiotoxicity and efficacy of acute drug-induced effects on human heart. Moreover, the functionality of the cardiac tissue model with the developed contraction force measurement system was shown on a proof-of-concept level