Impelling force and current challenges by chemicals in somatic cell reprogramming and expansion beyond hepatocytes

Table 1 Expandable hepatic cells induced from primary hepatocytes to date

Hepatocyte source(s)	Chemicals	Growth factor(s)	Medium and supplements	Expansion potential		Yr
				Passage count	Doubling time
Mouse and Rat	A83-01, CHIR99021, Y-27632	EGF	DMEM/F12, HEPES, L-proline, ITS, dexamethasone, nicotinamide, ascorbic acid-2 phosphate, BSA, antibiotic/ antimycotic	Rat: >10; Mouse: >20	Rat: 14.7 ± 1.1 h	2017[62]
Mouse	A83-01, CHIR99021, Y-27632	EGF, HGF	DMEM/F12, N2 or ITS, S1P, LPA	>30	15-20 h	2017[63]
Human (resected patient liver tissue, non-lesion)	A83-01, CHIR99021	EGF, HGF	DMEM/F-12 (high glucose), FBS, nicotinamide, dexamethasone, ITS, penicillin/ streptomycin	>10	37.9-39.8 h	2018[64]
Human (resected patient liver tissue, non-lesion)	A83-01, CHIR99021, Y-27632	EGF, HGF	Advanced DMEM/F-12, N2, B27, sodium pyruvate, ascorbic acid, S1P, LPA	>10	24.7 ± 1.4 h	2018[67]
Human (normal, cryopreserved)	A83-01, Y-27632	EGF, FGF10, HGF, Wnt3a	Advanced DMEM/F-12, FBS, N2, B27 (minus vitamin A), N-acetylcysteine, nicotinamide, [Leu15]-gastrin I, penicillin/ streptomycin,	4 (normoxia); 8 (hypoxia)		2018[68]
Human (normal, freshly isolated and cryopreserved)	A83-01, CHIR99021, Y-27632	EGF, FGF7, FGF10, HGF, TGFa	Advanced DMEM/F-12, HEPES, B27 (minus vitamin A), R-spodin1 conditioned medium, N-acetylcysteine, nicotinamide, gastrin, GlutaMAX, penicillin/ streptomycin,	Fetal hepatocytes: >16	5-7 d	2018[70]

Table 2 The specificity and commonality of chemicals in direct lineage conversion

Compounds	Function	Target germ layer and cell types			Ref.
		Ectoderm: Neural stem/ progenitor cell, neuron	Mesoderm: Cardiomyocyte	Endoderm/ extraembryonic endoderm: Endoderm progenitor cell, XENs
A83-01	TGF-βRI (ALK4/5/7) inhibitor	+	+		[42,43,51,53]
AM580	RAR agonist			+	[25,54]
AS8351	KDM5B inhibitor		+		[53]
Bay K 8644	Ca2+ channel activator		+		[51]
BIX01294	Histone methyltransferase inhibitor	+	+		[42,53]
CHIR99021	GSK3 inhibitor	+	+	+	[25,41-46,50,51,53-55,78]
DMH1	BMP inhibitor	+			[46]
EPZ004777	DOT1L inhibitor			+	[25,54]
Forskolin	cAMP activator	+	+	+	[25,44-46,50,51,54,55,78]
GO6983	PKC inhibitor	+			[44]
Hh-Ag1.5	Smo agonist	+			[43]
I-BET151	BET bromodomain inhibitor	+			[78]
ISX9	Neurogenic agent	+			[78]
JNJ10198409	PDGF-RTK inhibitor		+		[53]
LDN193189	BMP type I receptor (ALK2/3) inhibitor	+			[43,45]
OAC2	Oct4 activator		+		[53]
Parnate (Tranylcypromine)	LSD1/MAO inhibitor	+	+	+	[25,43,50,54]
PD0325901	MEK inhibitor	+			[42,45]
RepSox (616452)	TGF-βRI (ALK5) inhibitor	+	+	+	[25,41,44,46,50,54,55]
RG108	DNA methyltransferase inhibitor	+			[42,43]
SB431542	TGF-βRI (ALK4/7) inhibitor	+			[45,78]
SC1	ERK1/RasGAP inhibitor		+		[51,53]
SMER28	Autophagy modulator	+			[43]
SP600125	JNK inhibitor	+			[44,46]
SU16F	PDGFRβ inhibitor		+		[53]
TTNPB	RAR agonist		+	+	[50,55]
VPA	Histone deacetylase inhibitor	+	+	+	[25,41,42,44,46,50,54]
Y‑27632	ROCK inhibitor	+	+	+	[44,46,53-55]

XENs: Extraembryonic endoderm-like cells.

Table 3 Advantages and disadvantages of different strategies for functional cell induction

Strategy	Induction efficiency	Reproducibi-lity/stability	Target specificity	Cellular function	In vivo engraftment	Safety	Scaling up	Cost	Ref.
TF-mediated pluripotent reprogramming followed by differentia-tion	Moderate	Highly reproducible/ stable	High	Immature	Low	Genomic integration; tumorigenesis risk	Expandable before differentia-tion	Very high	[11,97-99]
TF-mediated direct lineage conversion	Fast and efficient	Reproducible/stable	High	Deficient	Low	Genomic integration	Expandable in progenitors	High	[100-103]
Chemical-mediated pluripotent reprogramming followed by differentia-tion	Controversial	Poorly reproducible/ unstable	Low	Not clear	Not clear	Integration-free	Not clear	Low	[24,25,29,31]
Chemical-mediated direct lineage conversion	Low	Reproducible/ unstable	Low	Deficient	Low	Integration-free	Expandable in progenitors	Very low	[18,77,104,105]
Chemical-mediated direct lineage expansion	Fast and efficient	Reproducible/ unstable	Low	Close to primary	High	Integration free	Expandable in rodents/ Limited in humans	Very low	[62,64,67,68]

TF: Transcriptional factor; XENs: Extraembryonic endoderm-like cells.