(a).

Year	Study	Animal model	Dose	Size of sample	Time of analysis after injection
2007	Nagae et al. [35]	Rabbits, nucleotomy	20 μl	36	2, 4, and 8 weeks
2009	Kazuhide et al. [34]	Rabbits, nucleotomy	20 μl	128	2, 4, and 8 weeks
2009	Chen et al. [20]	Miniature porcine, chymopapain	No mention	14	4 and 8 weeks
2011	GB et al. [36]	Rats, needle puncture	100 μl	18	2, 4, and 6 weeks
2012	Obata et al. [37]	Rabbits, needle puncture	20 μl	12	8 weeks
2015	Gui et al. [38]	Rabbits, needle puncture	100 μl	36	2 weeks
2016	Wang et al. [39]	Rabbits, needle puncture	200 μl	40	1, 2, and 8 weeks
2016	Yang et al. [22]	Rabbits, needle puncture	15 μl	24	0, 4, 8, and 12 weeks
2016	Hou et al. [40]	Rabbits	40 μl	60	4 and 8 weeks