Table 1.
Summary of the differences between immature and mature CMs.
| Parameter | Immature CMs | Mature CMs |
|---|---|---|
| Cell shape | Irregular | Rod-shaped |
| Cell area | 480 ± 32 µm2 | 1716 ± 150 µm2 |
| Sarcomere structure | Disorganized and less-developed | Organized and M-line developed |
| Sarcomere length | ≈1.65 µm | ≈1.81−2.3 µm |
| Cardiac troponin I | ssTnI | cTnI |
| Titin | N2BA isoform (N2B and N2A) | N2B |
| MHC | β-MHC ≤ α-MHC | β-MHC >> α-MHC |
| T-tubules | Deficient | Abundant |
| Mitochondria | Round and cristae are less mature | Elongated and more mature cristae (up to 40% cell volume) |
| Sarcoplasmic reticulum network | Underdeveloped | Well-developed |
| Metabolic | Glycolysis (80%) | Fatty acid β-oxidation 70–80%) |
| Nucleation | Mononuclear | Dinuclear (~35.3%) |
| Upstroke velocity | ≈44 to 50 V/s | ≈188.7 to 250 V/s |
| Resting membrane potential | ≈ −50 to −60 mV | ≈ −90 mV |
| Gap junction | Circumferentially | Periphery at the intercalated disc |
| Adrenergic receptors | ≈β1 ≤ β2 | ≈70 β1:30 β2 and response to β-adrenergic stimulation |
| SERCA2a | Low expressed | Highly expressed |
| Contraction | Asynchronous | Synchronous |