Human vs Mouse Heart Development

Mice Heart Development

Mice provide an excellent model for studying not only heart development but heart disease as well. Because mice are also mammalian, they have a similar heart development to that of humans. In mice, the heart begins to develop at embryonic day 8 when the cardiac loop forms, and by embryonic day 14.5, all of the major structures of the heart are formed. These structures include the atria, ventricle, and septum formation of the heart. The figure above adapted from Andrés-Delgado & Mercader, 2016 shows the major development steps in mouse heart development starting with the heart tube, formation of the cardiac loop, formation of the valves, and then eventually the distinct formation of the individual chambers with full septation. After these structures are formed, the heart undergoes more development where the existing structures are more refined and the heart continues to compact making the muscle more condensed.

Human Heart Development

Because gestation is longer in humans than mice, the development of the heart also takes more time. The heart begins to form around 4 weeks into development and does not finish forming all of the major structures till around 9 weeks into development. It is after this time that the heart will continue to enlarge as the rest of the embryo develops. The human heart follows the same developmental stages as the mouse regarding the heart; however, the time that it takes is longer. It still develops the same features with similar timings. The figure above adapted from Lim et al., 2021 shows the major developmental stages and their timings for human heart development.

Differences in Development

Above are two figures adapted from Krishnan et al., 2014 where the major development events are tracked for when these features start and stop developing. Excluded are the beginnings and ending of major heart development as well as the refinement process of heart structure which greatly exceeds the time frame listed. The major difference in heart development between mice and humans lies in the timing of the heart development with respect to rest of embryonic development. As a result there are some congenital diseases that do not occur near as frequently. This is due to hemodynamic processes in which there is potentially not enough blood flow to different parts of the heart which then stunts the development of these areas.

Citations

• Krishnan, A., Samtani, R., Dhanantwari, P. et al. A detailed comparison of mouse and human cardiac development. Pediatr Res 76, 500–507 (2014). https://doi.org/10.1038/pr.2014.128
• Andrés-Delgado, L., & Mercader, N. (2016). Interplay between cardiac function and heart development. Biochimica et biophysica acta, 1863(7 Pt B), 1707–1716. https://doi.org/10.1016/j.bbamcr.2016.03.004
• Lim TB, Foo SYR, Chen CK. The Role of Epigenetics in Congenital Heart Disease. Genes. 2021; 12(3):390. https://doi.org/10.3390/genes12030390