Table 3.
Desired tissue (patho)physiological activities, proposed building blocks, feature sizes, and cited resolutions (reported for cell-laden or acellular bioinks) for major tissue models. (NA: not available)
| Organ Model |
Primary (Patho)- physiological Activity |
Proposed Building Block | Desired Feature Size42 | Cited Resolution | Ref |
|---|---|---|---|---|---|
| Bone (compact) | Provides mechanical strength of the skeletal system | Cylindrical osteon of osteocytes and mineralized ECM | ~200 μm | 150–400 μm; acellular |
43,44 |
| Cartilage | Provides structural support and lubricates joints between bones | Zonal layers of ECM hydrogel and chondrocytes | 50–500 μm | 100–200 μm; cell-laden |
45 |
| Skeletal muscle | Provides forces for movements | Aligned multi-nucleated skeletal muscle bundles/fibers | ~20–50 μm | 50–200 μm; acellular |
43,46 |
| Brain | Generates electrical signaling for cognition and for controlling rest of the body | Directionally oriented neuronal cells supported by astrocytes | <5 μm (neurites) | 350 μm; cell-laden |
6 |
| Eye cornea | Allows light penetration and focusing for visualization | Transparent membrane seeded by epithelial/endothelial cells | ~500 μm (thickness) | 150–200 μm; cell-laden |
47 |
| Cardiac muscle | Generates contractions for driving the circulatory system | Aligned cardiomyocytes bundles | 50–100 μm | 100–200 μm; cell-laden |
5 |
| Lung | Provides gas exchange through respiratory movements | Hierarchical airways and spherical alveoli at terminal ends with epithelial cells on the surfaces and endothelial cells in the junctions | ~200 μm (diameter of alveolus); single cell (alveolus thickness) | NA | |
| Gut | Enables food digestion and absorption | Membrane-like ECM containing villi surfaces with epithelial cells | 50–150 μm (villus size) ~500 μm (villus length) |
500 μm; acellular |
48 |
| Liver | Metabolizes and detoxifies | Hexagonal lobule of primarily hepatocytes | ~500 μm | 50–200 μm; cell-laden |
8 |
| Kidney | Provides excretion of waste molecules and reabsorption of functional molecules | Various nephron structures (e.g., renal corpuscle, renal tubule) | ~15–250 μm | 100–200 μm; acellular |
3 |
| Blood vessel | Carries nutrients/oxygen to the organs and wastes away | Tubular layers of cells and ECMs | 30 μm (arteriole/venule); 8 μm (capillary) | 50–500 μm; acellular |
4 |
| Tumors | Feature hypoxic, uncontrolled proliferative and dense tumor microenvironments | Tumor type-dependent cells in ECMs | 10–500 μm (tumor type-dependent) | 50–500 μm; cell-laden |
40 |