Table 2.

Benchmarking Parameters for Heart-on-a-Chip, Liver-on-a-Chip, Kidney-on-a-Chip, and Adipose-on-a-Chip Organ Models

Model	Benchmarking parameters
Heart-on-a-chip	Elongated, rod-like cardiomyocytes149
	Expression of adult ventricular genes (MYH7, MYL2, and TNNI3)149
	Contractile stress 30–60 mN/mm3,150,151
	Positive force-frequency ratio, characteristic notch at the top of upstroke152
	RMP −90 mV, action potential amplitude 100–110 mV, action potential duration 230–300 ms152
	Depolarization velocity 250–300 V/s, conduction velocity 30–100 cm/s152
	Well-developed sarcoplasmic reticulum structure and function, gene expression of calcium-handling machinery149
	Cytosolic calcium concentration 1 μm during systole, 100 nmol/L during diastole153
	Reliance on fatty acid oxidation (>70%)154
Liver-on-a-chip	Albumin production >37 μg per day/1 million hepatocytes155
	Urea synthesis >56 μg per day/1 million hepatocytes155
	Expression of phase I and II CYP450 enzymes, hepatocyte uptake, and efflux transports155
	Polygonal, nonrounded, polarized hepatocytes155
	Presence of bile canaliculi (BSEP, MRP2, and AQP1) and bile acid synthesis155
	Presence of Kupffer cells (CD68) and stellate cells (desmin)155
Kidney-on-a-chip	Albumin reabsorption efficiency of at least 80%156
	Glucose reabsorption efficiency of at least 95%157
	Transepithelial electrical resistance 6–10 Ω·cm2 (proximal tubule),158 100–500 Ω·cm2 (renal cell lines)159
	Expression of podocyte markers (NPSH1, NPSH2, and WT1)160
	Expression of mesangial cell markers (GATA3, PDGFRA, and ITGA8)160
	Expression of glomerular endothelial cell markers (EHD3, EMCN, KDR, and CD31)160
	Brush border enzyme activity: Na+/K+-ATPase, alkaline phosphatase, γ-glutamyltransferase160
Adipose-on-a-chip	Adipocytes >55 μm in diameter161
	Unilocular lipid contents, expression of maturation markers (PPARG, FABP4, and adiponectin)162
	Evidence of insulin-stimulated glucose uptake162
	Evidence of lipid metabolism (free fatty acid uptake, glycerol release)162
	Incorporation of resident immune cells (CD68) and stromovascular cells (CD31, ACTA2)162

Parameters are reflective of values normally observed for mature cardiomyocytes, hepatocytes, proximal tubule epithelial cells/glomerular cells, and adipocytes. ACTA2 indicates alpha-smooth muscle actin; AQP1 indicates aquaporin 1; BSEP, bile salt export pump; CD, cluster of differentiation; CYP450, cytochrome P450; DES, desmin; EHD3, EH domain containing 3; EMCN, endomucin; FABP4, fatty acid-binding protein 4; GATA3, GATA-binding protein 3; ITGA8, integrin alpha 8; KDR, Kinase Insert Domain Receptor; MRP2, multidrug resistance-associated protein 2; MYH7, myosin heavy chain 7; MYL2, myosin light chain 2; NPSH1, nephrin; NPSH2, podocin; PDGFRA, platelet-derived growth factor receptor alpha; PPARG, peroxisome proliferator-activated receptor gamma; RMP, resting membrane potential; TNNI3, troponin I type 3; WT1, Wilms tumor-1; and WT, wild-type.