The adult heart is a vital and highly specialized organ of the human body, with limited capability of self-repair and regeneration in case of injury or disease. Engineering biomimetic cardiac tissue to regenerate the heart has been an ambition in the field of tissue engineering, tracing back to the 1990s. Increased understanding of human stem cell biology and advances in process engineering have provided an unlimited source of cells, particularly cardiomyocytes, for the development of functional cardiac muscle, even though pluripotent stem cell-derived cardiomyocytes poorly resemble those of the adult heart. This review outlines key biology-inspired strategies reported to improve cardiomyocyte maturation features and current biofabrication approaches developed to engineer clinically relevant cardiac tissues. It also highlights the potential use of this technology in drug discovery science and disease modeling as well as the current efforts to translate it into effective therapies that improve heart function and promote regeneration.

Microfluidic paper-based analytical devices (μPADs) fabricated by wax-printing are suitable platforms for the development of simple and affordable molecular diagnostic assays for infectious diseases, especially in resource-limited settings. Paper devices can be modified for biological assays by adding appropriate reagents to the test areas. For this purpose, the use of affinity immobilization strategies can be a good solution for bioactive paper fabrication. This paper describes a methodology to capture labeled-DNA strands and hybrids on paper via the anchoring of antibodies with a fusion protein that combines a family 3 carbohydrate binding module (CBM) from Clostridium thermocellum, with high affinity to cellulose, and the ZZ fragment of the staphyloccocal protein A, which recognizes IgG antibodies via their Fc portion. Antibodies immobilized via CBM-ZZ were able to capture appropriately labeled (biotin, fluorescein) DNA strands and DNA hybrids. The ability of an antibody specific to biotin to discriminate complementary from noncomplementary, biotin-labeled targets was demonstrated in both spot and microchannel assays. Hybridization was detected by fluorescence emission of the fluorescein-labeled DNA probe. The efficiency of the capture of labeled-DNA by antibodies immobilized on paper via the CBM-ZZ construct was significantly higher when compared with a physical adsorption method where antibodies were simply spotted on paper without the intermediation of other molecules. The experimental proof of concept of wax-printed μPADs functionalized with CBM-ZZ for DNA detection at room temperature presented in this study constitutes an important step toward the development of easy to use and affordable molecular diagnostic tests.

Extracellular vesicles (EV) are an attractive therapy to boost cardiac regeneration. Nevertheless, identification of native EV and corresponding cell platform(s) suitable for therapeutic application, is still a challenge. Here, EV are isolated from key stages of the human induced pluripotent stem cell-cardiomyocyte (hiPSC-CM) differentiation and maturation, i.e., from hiPSC (hiPSC-EV), cardiac progenitors, immature and mature cardiomyocytes, with the aim of identifying a promising cell biofactory for EV production, and pinpoint the genetic signatures of bioactive EV. EV secreted by hiPSC and cardiac derivatives show a typical size distribution profile and the expression of specific EV markers. Bioactivity assays show increased tube formation and migration in HUVEC treated with hiPSC-EV compared to EV from committed cell populations. hiPSC-EV also significantly increase cell cycle activity of hiPSC-CM. Global miRNA expression profiles, obtained by small RNA-seq analysis, corroborate an EV-miRNA pattern indicative of stem cell to cardiomyocyte specification, confirming that hiPSC-EV are enriched in pluripotency-associated miRNA with higher in vitro pro-angiogenic and pro-proliferative properties. In particular, a stemness maintenance miRNA cluster upregulated in hiPSC-EV targets the PTEN/PI3K/AKT pathway, involved in cell proliferation and survival. Overall, the findings validate hiPSC as cell biofactories for EV production for cardiac regenerative applications.