Engineered cardiac microbundle time-lapse microscopy image dataset

The "Microbundle Time-lapse Dataset" contains 24 experimental time-lapse images of cardiac microbundles using three distinct types of experimental testbeds. Of the 24 experimental time-lapse images, 23 examples are brightfield videos, and a single example is a phase contrast video. We categorize the different experimental testbeds into 3 types, where "Type 1" includes movies obtained from standard experimental microbundle platforms termed microbundle strain gauges [1,2,3]. We refer to data collected from non-standard platforms termed FibroTUGs [4] as "Type 2" data, and "Type 3" data represents a highly versatile and diverse nanofabricated experimental platform [5,6].

References:

[1] Boudou T, Legant WR, Mu A, Borochin MA, Thavandiran N, Radisic M, Zandstra PW, Epstein JA, Margulies KB, Chen CS. A microfabricated platform to measure and manipulate the mechanics of engineered cardiac microtissues. Tissue Engineering Part A. 2012 May 1;18(9-10):910-9.

[2] Xu F, Zhao R, Liu AS, Metz T, Shi Y, Bose P, Reich DH. A microfabricated magnetic actuation device for mechanical conditioning of arrays of 3D microtissues. Lab on a Chip. 2015;15(11):2496-503.

[3] Bielawski KS, Leonard A, Bhandari S, Murry CE, Sniadecki NJ. Real-time force and frequency analysis of engineered human heart tissue derived from induced pluripotent stem cells using magnetic sensing. Tissue Engineering Part C: Methods. 2016 Oct 1;22(10):932-40.

[4] DePalma SJ, Davidson CD, Stis AE, Helms AS, Baker BM. Microenvironmental determinants of organized iPSC-cardiomyocyte tissues on synthetic fibrous matrices. Biomaterials science. 2021;9(1):93-107.

[5] Jayne RK, Karakan MÇ, Zhang K, Pierce N, Michas C, Bishop DJ, Chen CS, Ekinci KL, White AE. Direct laser writing for cardiac tissue engineering: a microfluidic heart on a chip with integrated transducers. Lab on a Chip. 2021;21(9):1724-37.

[6] Karakan MÇ. A Direct-Laser-Written Heart-on-a-Chip Platform for Generation and Stimulation of Engineered Heart Tissues (Doctoral dissertation, Boston University, 2023).

Methods
We include here a brief description of the 3 data types. For "Type 1" testbeds, each experimental tissue well consisted of 2 pillars with rectangular cross sections and spherical caps cast from poly(dimethylsiloxane) (PDMS) using a 3D printed mold. Following treatment to promote cell attachment to the spherical caps, hiPSC-CMs, differentiated and purified, were seeded with human ventricular cardiac fibroblasts. And after 5-7 days of seeding, time-lapse videos of tissue contractions were acquired. 

As for "Type 2" experimental platforms, arrays of PDMS cantilevers were fabricated by soft lithography. Then, fiber matrices were generated by selective photo-crosslinking of electrospun dextran vinyl sulfone (DVS) fibers and suspended between pairs of cantilevers. After functionalizing the electrospun fiber matrices, iPSC-CMs, differentiated and purified, were patterned onto matrices using microfabricated seeding masks cast from 3D-printed molds. Finally, time-lapse videos of the microtissue’s spontaneous contractions were taken after 7 days of seeding. 

Finally, seeding platforms from "Type 3" were generated using a combination of soft lithography and two-photon direct laser writing (DLW). Briefly, the process involves printing negative master molds using DLW, casting PDMS onto the molds, followed by sandwiching, curing and demolding. Then, cage-like micron-scale structures were printed using DLW on the sides of the wells of the demolded PDMS devices to facilitate cell attachment. Differentiated and purified hiPSC-CMs were seeded into the wells and time-lapse videos of the tissue contractions were obtained 4-9 days after seeding. Of note, these platforms allow for mechanical actuation of the microbundle, and within this dataset, we include "Example_01" which is subjected to sawtooth actuation. 

We note that more details about testbed fabrication, tissue preparation protocols, and imaging procedures for each type of the 3 experimental platforms are included in the accompanying file "Microbundle_metadata.pdf" and its machine-readable version in ".csv" format. We note that cells containing "N/A" indicate that the details provided for the other tissue engineering platform types are not applicable to this specific type.