Table 4.

Developing technologies for maturing patient testicular tissues/cells and producing sperm outside the patient’s body. Evidence in human studies.

Tissue source	Technique	Methods	Results	Reference
Cisgender prepubertal tissue	Tissue- based	Xenotransplant into SCID or nude mice
Fresh tissue into dorsal skin
From 10-11-year-old donors, n=3			Spermatogonia	Goossens et al. (2008)
From 3-9-year-old donors, n=3			BOLL+ spermatocytes	Ntemou et al. (2019)
Fresh tissue into scrotum
From 5-year-old donor, n=1			Spermatogonia	Van Saen et al. (2011)
From 12-13-year-old donors, n=2			Spermatocyte	Van Saen et al. (2011)
From 2-12-year-old donors, n=10			Spermatocyte	Poels et al. (2013)
From 3-9 -ear-old donors, n=3			Spermatocyte	Ntemou et al. (2019)
Frozen prepubertal tissue into scrotum
From 3-13-year-old donors, n=3			Spermatogonia	Van Saen et al. (2011)
From 2-12-year-old donors, n=11			Spermatogonia	Wyns et al. (2007)
From 2-15-year-old donors, n=6			Spermatogonia	Poels et al. (2014)
From 7-14-year-old donors, n=5			Spermatocyte	Wyns et al. (2008)
From 2-12-year-old donors, n=10			Spermatocyte	Poels et al. (2013)
Cisgender adult tissue
Fresh tissue into dorsal skin			Degenerated tissue	Schlatt et al. (2006)
			Spermatogonia	Geens et al. (2006)
Fresh adult tissue into scrotum			Spermatocyte	Van Saen et al. (2011)
Frozen adult tissue into scrotum			Spermatocyte	Van Saen et al. (2011)
Cisgender immature tissues (age 6-14)	Tissue- based	IVM with testicular tissue culture
Used fresh			Spermatogonia	Portela et al. (2019)
Used frozen			Spermatogonia	Portela et al. (2019), de Michele et al. (2017)
			SYCP3+ primary spermatocytes	Medrano et al. (2018), Younis et al. (2023)
			Round spermatid	de Michele et al. (2018)
Cisgender adult tissue
Used Fresh			Spermatogonia	Jorgensen et al. (2014)
Transgender adult tissue
Fresh and cryopreserved adult GAHT-exposed testicular tissue			No progression of spermatogenesis after 2 weeks in culture	Komeya et al. (2021)
Cisgender prepubertal and adult cells	Cell-based	De novo testicular morphogenesis (organoid culture)
Fresh pubertal (age 15) and adult testicular cells	SC- based, or SC-free transwell		Mitotically-active germ cells, normal somatic cells function and arrangement	Baert et al. (2017)
Frozen prepubertal testicular cells	Matrigel		Inverted organization of spermatogonia and somatic cells	Sakib et al. (2019)
Fresh and frozen adult testicular cells	ECM		Spermatogonia clusters, normal somatic cells function and arrangement	Baert et al. (2015)
			PRM2+ elongated spermatids	Pendergraft et al. (2017), Nikmahzar et al. (2023)

TGNB, transgender and non-binary; GnRHa, gonadotropin-releasing hormone agonist; GAHT, gender-affirming hormone therapy, SYCP3 +, synaptonemal complex protein 3 (marker for primary spermatocytes); SCID, severe combined immunodeficiency;, BOLL , boule homologue RNA-binding protein (marker for secondary spermatocytes and round spermatids); ECM, extracellular matrix; IVM, in vitro maturation; SC, scaffold.