Cardiac stem cells: Current knowledge and future prospects

Table 1 Main outcomes of the studies investigated the impact of nanotechnology in cardiac stem cell-based studies

Nanotechnology field	Types of nanoparticles	Type of cardiac disease/stem cells	Type of research	Outcomes	Ref.
Tissue engineering	Semi-crystalline PLLA nanostructured membranes among several PLGA membranes	Non-diseased/primary CMs	In vitro: electrospun matrices were used as scaffolds for generating cardiac tissue constructs	Nanostructured non-woven PLLA scaffolds provide flexibility and guidance for CMs growth and can be successfully applied to obtain structurally and functionally competent cardiac tissue constructs.	[201]
Tissue engineering	ECM-mimicking nanofibrous PLLA scaffolds with porous structure (porous NF PLLA) of high interconnection for cardiac tissue formation	Non-diseased/mouse ESCs	In vitro: CPCs with porous NF PLLA	In vitro: porous NF PLLA scaffolds facilitate cell attachment, extension, and differentiation.	[202]
			In vivo: male athymic nude mice
				In vivo: subcutaneous implantation of cell/scaffold supports survival of grafted cells and differentiation to CMs, SMCs, ECs lineages.
		CPCs
Tissue engineering/therapeutic	Biodegradable ANF	MI/hiPSCs-CMs	In vitro: hiPSCs (253G1)	In vitro: multilayered, elongated, organized CMs at high density along ANF, with up regulation of genes of sarcomere structures (ACTN2, TNNT2, TNNI3), cardiac maturation (MYH7), ventricular structures (MYL2, HAND2).	[203]
			In vivo: nude rat
				In vivo: CTLCs improve MI functionally due to transplantation of organized functional CMs.
Tissue engineering	Electroactive Au-Lap NPs loaded myocardial ECM	Non diseased/Resident CSCs	In vitro: rat CMs from 2-d old neonatal rats	Combination of electrically active nano-formulations and biologically active ECM boost the expression of cardiac-specific proteins (SAC, cTnl, Cx43).	[204]
Therapeutic	Self-assembling peptide nanofibers tethered with insulin-like growth factor-1 (NF-IGF-1)	MI/CPCs	In vitro: clonogenic CPCs	In vitro: NF-IGF-1 promote CPCs division (↑BrdU) and protect them from death signal (↓TdT).	[207]
				In vivo: CPCs-NF-IGF-1 enhance postinfarction ventricular remodeling, attenuate chamber dilation, and improve cardiac performance.
			In vivo: female Fischer 344 rats
Therapeutic	Transplantation of self-assembling nanopeptides: Cell-PM complex	MI/cSCA-1+ cardiac progenitors Other stem cells BM, SM, AMC	In vivo: Wild-type mice (C57Bl/6J); Adult GFP transgenic mice	cSCA-1/PM attenuates ventricular enlargement, restore cardiac function, with high capillary density (↑vWF) and conductive vessels (↑αSMA, ↑VEGF).	[208]
				↓TUNEL+ CMs in the infarct area of cSCA-1/PM.
Therapeutic	CMMP contained control-released stem cell factors in its polymeric core and cloaked with hCSC membrane fragments on the surface	MI/Human CSCs	In situ: characterization	In situ: CMMPs express hCSC surface markers.	[209]
			In vitro: NRCM
			In vivo: male SCID Beige mice
				In vitro: CMMPs promote NRCM contractility and proliferation.
				In vivo: CMMPs preserve viable myocardium, augment cardiac functions, with safety profile.
Therapeutic and drug delivery tool	Statin PLGA nanoparticles	MI/hAdSCs	In vivo: male nude mice (BALB/c nu/nu)	A small number of intravenously administered SimNP-loaded AdSCs improve cardiac function following MI, stimulating endogenous cardiac regeneration in the infarcted myocardium.	[244]
Tracking of treatment	Colloidal nanoparticles containing europium loaded on collagen matrix	MI/Lewis rat BM-MSCs	In vivo: female Fischer rat	Collagen matrix enhance transplanted MSC retention and reduce migration of the cells into remote organs as tracked by the radioactive NPs.	[211]
Tracking and magnetic targeting of treatment	Superparamagnetic iron microspheres	MI/Rat CDCs	In vitro: rat CDCsIn vivo: female WKY rats	In vitro: ↓caspase 3+, ↓TUNEL+.	[212]
				In vivo: enhanced cell engraftment, with attenuated left ventricular remodeling and increased ejection fraction. ↑GFP+, ↑Ki67+ CMs, and ↑GFP−/c-KIT+ cells.
Imaging and therapeutic by magnetic targeting	Ferumoxytol (FDA-approved SPIONs) nanoparticles linked by heparin sulfate and protamine sulfate	MI/Human and ratCDCs	In vitro: hCDCs and rCDCs	In vitro: ↓TUNEL+, ↓ROS and ↑CCK-8, ↑Ki67.	[213]
				In vivo: augmentation of acute cell retention and attenuation of left ventricular remodeling, 3 wk after treatment by MRI, fluorescence imaging, qPCR.
			In vivo: female WKY rats
Imaging and tracking for differentiation	Potassium niobate harmonic nanoparticles stabilized by polyethylene glycol	Non-diseased/ESC-derived CMs	In vitro: mouse ESC (CGR8 cell line)	Monitoring at high acquisition speed the rhythmic contractions of ESC-derived CMs beating within 3D cluster.	[245]
Therapeutic by magnetic guidance of NPs	Iron oxide nanoparticle-incorporated nanovesicles (exosome memetic nanovesicles); (IONP-NVs)	MI/MSCs	In vitro: rat CM, rat CFs, macrophage, HUVECs.	In vitro: under hypoxia IONP-MSCs exert	[217]
				Antiapoptotic effect on CMs: ↓caspase 3+, ↑Cx43, ↑PI3K.
				Antifibrotic effect on CFs: ↑Cx43, ↓TGFβ1, ↓αActa2, ↓MMP2, ↓MMP9.
				Anti-inflammatory effect on macrophage.
			In vivo: Fischer 344 rats
				Proangiogenic effect on HUVECs: ↑tube formation, ↑EC migration.
				In vivo: magnetic guidance increases IONP-MSCs retention within the infarcted heart, with early shift from inflammatory stage to reparative stage.

AMC: Adipose tissue-derived mesenchymal cell; ANF: Aligned PLGA nanofibers; Au-Lap NP: Gold and laponite nanoparticle; BrdU: Bromodeoxyuridine cell proliferation assay; CCK-8: Cell counting kit-8; CF: Cardiac fibroblast; CM: Cardiomyocyte; CMMP: Cell-mimicking microparticle; CPC: Cardiac progenitor cell; CTLC: Cardiac tissue-like construct; cTnl: Cardiac troponin 1; FDA: Food and Drug Administration; ECM: Extracellular matrix; ESC: Embryonic stem cell; hAdSC: Human adipose-derived stem cell; HUVEC: Human umbilical cord vein endothelial cell; IONP: Iron oxide nanoparticle; MRI: Magnetic resonance imaging; NF: Nanofibrous; MI: Myocardial infarction; MMP: Matrix metalloproteinase; NRCM: Neonatal rat cardiomyocyte; PLGA: Poly D,L-lactic-co-glycolic acid; PLLA: Poly (L-lactic acid); PM: Puramatrix™; qPCR: Quantitative polymerase chain reaction; SM: Skeletal myoblast; SPION: Superparamagnetic iron oxide NP; TdT: Terminal deoxynucleotidyl transferase apoptotic assay; TUNEL: Terminal deoxynucleotidyl transferase dUTP nick end labeling apoptotic assay; vWF: von-Willebrand factor; WKY: Wistar-Kyoto; αSMA: Alpha smooth muscle actin; 3-D: Three-dimensional.

Table 2 Completed clinical trials reporting on the use of cardiac derived stem cells in cardiovascular disorders

Study name, NCT Number	Start year	Study phase	Cardio-vascular disease	Patients number	Type of cardiac stem cells/origin	Route of delivery /count of cells	Timing of cell delivery	Follow up times	Imagingtechniques	Outcomes	Ref.
CADUCEUS, 00893360	2009	1	IHD	17	Autologous CDCs/endomyocardial biopsies	IC/12.5-25 × 106	1.5-3 m post STEMI	6 mo	MRI	Significant reduction in infarct size	[221]
										Significant growth in viable mass global LVEF remains unchanged LVEF and volumes.
ALLSTAR, 01458405	2017	I/II	IHD	90	Allogenic CDCs/endomyocardial biopsies	IC/25 × 106	< 5 d post MI	12 mo	MRI	No effect on scar sizeAttenuation of post infarct cardiac remodeling	[222]
										Improvement in LV end diastolic volume
ALCADIA, 00981006	2010	I	CHFIHDVD	6	Autologous hCSCs/endomyocardial biopsies + bFGF on gelatin hydrogel sheet	IM/0.5 × 106 /kg and 200 µg of bFGF	At CABG	12 mo	Not mentioned	Decreased scar size	[229]
ESCORT, 020579000	2013	I	IHD	6	ESCs-derived ISL1+ CSCs	Epicardial patch 5-10 × 106 CSCs embedded in a fibrin patch	At CABG	18 mo	CT	Symptomatically improved patients with an increased systolic motion of the cell- treated segments.	[223]
									PET scan
										The protocol generated a highly purified population of cardiovascular progenitors.
									Echo
										One patient died of heart failure after 22 mo
CAREMI, 02439398.	2014	I/II	AMI	55	Allogeneic hCSCs/right atrial appendage	IC/35 × 106 cells	5 to 7 d after successful reperfusion of AMI by PCI or 8 d from symptoms onset	1 wk, 1, 2, 3, 4, 5, 6, 9 and 12 mo	MRI	Allogeneic CSCs intracoronary infusion early after AMI is safe and anticipates reasonable efficacy outcomes	[227]
									ECG
CONSERT-HF, 02501811.	2015	II	HF	125	Autologous c-KIT+ CPCs + MSCs/right ventricular endocardial biopsy + Bone marrow aspiration	Trans endocardial/150 × 106 MSCs and 5 × 106 CPCs	14 wk after cell harvest	6 and 12 mo	MRI	Increased LVEF	[230]
									Treadmill
										Decrease in infarct size with LV end systolic volume reduction.
									Questionnaire
										Strong safety profile
HOPE, 02485938	2015	I\II	CM secondary to DMD	25	Allogeneic CDCs	IC/75 × 106	Not specified	12 mo	MRI	Significant scar reduction improvement in inferior wall systolic thickening compared to the usual care group.	[228]
									Questionnaire
										CDCs are generally safe and well-tolerated
DYNAMIC, 02293603	2014	I	Idiopathic dilated CM	42	Allogeneic CDC/not specified	IC/Stepwise dose escalation	Not specified	6, 12 mo	ECG	Not published	_
									Cardiac enzymes
TICAP, 01273857	2011	I	HLHS	7	Autologous CDCs/right atrial appendage	IC/0.3 × 106 cells/kg	1 m after cardiac surgery	36 mo	Echo	Safety of the procedure	[233]
										Increased right ventricle ejection fraction
										Improved somatic growth
										Reduced heart failure status
Perseus, 01829750	2013	II	HLHS	34	Autologous CDCs/not specified	IC/0.3 × 106 cells/kg	4 to 9 wk after surgery	3 and 12 mo follow-up	EchoMRIQuestionnaire	Significant improve of ventricular function	[231]
										Improved somatic growth, and quality of life
										Reduced heart failure status and cardiac fibrosis compared with baseline

AMI: Acute myocardial infarction; bFGF: Basic fibroblast growth factor; CABG: Coronary artery by bass graft; CHF: Congestive heart failure; CM: Cardiomyopathy; CSC: Cardiac stem cell; DMD: Duchenne muscle dystrophy; hCSC: Human-derived cardiac stem cell; HLHS: Hypoplastic left heart syndrome; IC: Intracoronary; IHD: Ischemic heart disease; IHF: Ischemic heart failure; IM: Intramyocardial; MRI: Magnetic resonance imaging; NCT: National clinical trial; PCI: Percutaneous infusion; STEMI: ST segment elevation after MI; VD: Ventricular dysfunction.

Table 3 Ongoing and future expected clinical trials

Study name, NCT number	Year of study start	Study phase	Cardiovascular disease	Number of patients	Type of cardiac cells	Route of delivery
Regress-HFpEF, 02941705	2017	II	Symptomatic hypertensive heart disease induced HFpEF	40	Allogeneic CDCs	IC
APOLLON trial, 02781922	2016	III	HLHS	40	Autologous CSCs	IC
CHILD, 03406884	2019	I	HLHS	32	Autologous c-KIT+ cells	IM
ALPHA, 03145298	2017	I	PAH	26	Allogeneic CDC	IV
TAC-HFT-II, 02503280	2025	I/II	IHF	0 enrollment until now	Autologous combination of MSCs and CSCs	Trans endocardial Injection

CSC: Cardiac stem cell; HFpEF: Heart failure with preserved ejection fraction; HLHS: Hypoplastic left heart syndrome; IC: Intracardiac; IHF: Ischemic heart failure; IM: Intramyocardial; IV: Intravenous; NCT: National clinical trial; PAH: Pulmonary atrial hypertension.