Table 2. Characteristics of stem cells.

Year	First Author	numbers	Label	Modification	Follow-up Time	Fate
2004	Bochinski [4]	5 X103	GFP	BDNF transduction	3 months	undetectable
2006	Y Kim [5]	1X106	lacZ	none	2 weeks / 4 weeks	detected
2009	Fall [6]	1X107	PKH-26	none	3 weeks / 5 weeks	detected
2010	Albersen [7]	1X106	Edu	none	4weeks	very few
2010	Kendirci [8]	0.5 X106	GFP transgene	p75LNGFR selection	4weeks	undetectable
2011	Lin [9]	1X106	Edu	none	7days	time-dependent disappearance
2011	Lin [10]	unclear	Edu	none	3 months	detected
2011	Woo [11]	1X106	PKH-26	none	4 weeks	detected
2012	Fandel [12]	2X106	Edu	none	4 weeks	time-dependent disappearance
2012	SJ Kim [13]	1X106	PKH-26	none	4 weeks	detected
2012	SJ Kim [14]	1X106	unclear	BDNF transduction	4 weeks	detected
2012	Kovanecz [15]	1X106	unclear	Oral sildenafil	42days	undetectable
2012	Piao [16]	1X106	PKH-26	BDNF	4 weeks	quantify
2012	Qiu [17]	1X106	Edu	none	17 weeks	very few
2012	Qiu [18]	2X106	none	none	12 weeks	No mentioned
2013	Jeong [19]	1X106	none	BDNF Oral udenafil	4 weeks	No mentioned
2013	You [20]	1X106	CELL STALKER	None	4 weeks	detected
2013	You [21]	1X106	CELL STALKER	None	4 weeks	detected
2013	IG Kim [22]	1X106	PKH-26	NGF	4 weeks	quantify
2013	Choi [23]	1X107	CM-DiI	none	4 weeks	detected
2013	Ying [24]	1X106	none	none	3 months	No mentioned
2014	Ying [25]	1X106	none	none	3 months	No mentioned
2014	Miyamoto [26]	1X106	none	none	12 weeks	detected
2014	Lee [27]	1X106	PKH-26	BDNF, bFGF	4 weeks	detected