Table I. Neurite growth promoting factors identified in the USSC secretome. Overall, 31 proteins were identified in the USSC secretome (contaminants excluded) which are known to be directly involved in neurite growth.

ID	Neurite growth promoting factor	Short description	Secretion via/localization	Reference
O00468	Agrin	Heparan sulfate basal lamina glycoprotein	signal peptide	72
O15123	Angiopoietin-2	Growth factor	signal peptide	40
P10909	Clusterin (Clu)	Extracellular chaperone	signal peptide	60–61
P09603	Colony-stimulating factor 1 (CSF-1)	Cytokine	signal peptide	55
P07585	Decorin	Matrix proteoglycan	signal peptide	46
P23142	Fibulin-1	ECM-associated	signal peptide	47
P06396	Gelsolin	Actin-binding protein	signal peptide	80
P07093	Glia-derived nexin (serpinE2)	Secreted serine protease inhibitor	signal peptide	57
P28799	Granulins	Secreted glycosylated peptide, cytokine-like activity	signal peptide	68–69
Q99988	Growth/differentiation factor 15 (GDF-15)	Growth factor	signal peptide	41
P51858	Hepatoma-derived growth factor (HDGF)	Growth factor	extracellular	42
P14174	Macrophage migration inhibitory factor (MIF)	Pro-inflammatory cytokine	non-classical pathway	56
P55145	Mesencephalic astrocyte-derived neurotrophic factor (MANF)	Neurotrophic factor	signal peptide	37
Q9HB63	Netrin-4	ECM-associated	signal peptide	48
Q9UMX5	Neudesin	Secreted neurotrophic factor	signal peptide	38
Q8TB73	Neuron-derived neurotrophic factor (NDNF)	Neurotrophic factor	signal peptide	39
Q7Z3B1	Neuronal growth regulator 1	Membrane-associated	signal peptide	49
Q9Y639	Neuroplastin	Type I transmembrane protein	signal peptide	50–51
Q99574	Neuroserpin	Secreted serine protease inhibitor	signal peptide	58
P14543	Nidogen-1	Sulfated glycoprotein in basal lamina	signal peptide	71
O95897	Noelin-2	secreted glycoprotein	signal peptide	52
Q15063	Periostin	ECM-associated	signal peptide	67
P36955	Pigment epithelium-derived factor (PEDF)	Secreted neurotrophic factor	signal peptide	84–86
P05121	Plasminogen activator inhibitor 1 (serpinE1)	Secreted serine protease inhibitor	signal peptide	59
P04085	Platelet-derived growth factor (PDGFA)	Growth factor	signal peptide	43
P09486	Secreted protein, acidic, cysteine-rich (SPARC)	Matrix-asscociated	signal peptide	53
P48061	Stromal cell-derived factor 1 (SDF-1)	Chemokine	signal peptide	14–15
P24821	Tenascin	ECM-associated	signal peptide	54
P07996	Thrombospondin-1 (TSP-1)	Adhesive glycoprotein	signal peptide	63
P01137	Transforming growth factor, beta-1 (TGF-b1)	Growth factor	signal peptide	45
P61812	Transforming growth factor, beta-2 (TGF-b2)	Growth factor	signal peptide	44