Elucidating the secretion proteome of human

Various studies on stem cell-derived secreted factors showed that the secreted factor alone without the stem cell itself may cause tissue repair in various conditions that involved tissue/organ damage.The secreted factors are referred to as secretome, microvesicles, or exosome and can be found in the medium where the stem cells are cultured; thus, the medium is called conditioned medium (CM) [2]. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

elucidating the secretion proteome of human-72

Various studies showed that conditioned medium have been tested in various kinds of diseases/conditions (Table 1) [1, 3–33], that is, alopecia [3, 5], acute and chronic hind limb ischemia [6–9], acute and chronic wound healing [4, 10–14], myocardial infarct [1, 15–18], acute liver injury/failure [19–22], cerebral injury/ischemia/stroke [23–27], spinal cord injury [28], lung injury [32], and bone defect [33], and showed improvement of the conditions.

Moreover, chronic kidney disease that was treated using human embryonic stem cell-derived mesenchymal stem cell (hu ESC-MSC) CM showed decreased systolic blood pressure and proteinuria and improvement in tubular and glomerular damage, renal blood flow, and glomerular filtration rate [29].

In the two cases of kidney disease, it can be concluded that CM from hu-ESC-MSC can improve the condition, and the needed growth factor level is presumably enough as CM processing includes a 25-time concentration step [29].

However, for hu-UCB-USSC or m BM-MSC-CM, lack of data concerning CM processing and growth factor level of the CM [30] prevent further analysis to conclude whether the failure to improve the condition is due to the lack of certain growth factor or due to the level of growth factors that was too low to give an effect.

However, nephropathy that was treated using CM from human umbilical cord blood unrestricted somatic stem cell (hu UCB-USSC) or mouse bone marrow mesenchymal stem cell (m BM-MSC) CM did not show improvement in serum urea and creatinine level, histopathological damage, and physical activity score [30].

Moreover, prevention of cancer using human mesenchymal stem cell line CM showed increased tumor cell proliferation and vascularization [31].Data collection is as follows: treated conditions/diseases, type of cell that was cultured, detailed composition of medium and supplements that was used to culture the cells, culture condition (hypoxia or normoxia) to get the CM, CM processing, growth factors, and other secretions that were analyzed; method (mode) of application and outcome of CM application were noted, grouped, and tabulated.Data synthesis is as follows: data were grouped according to treated disease and cell types that were used to produce the CM.Only some of the various studies using CM checked the growth factor levels (Table 3) [5–10, 13, 17, 20, 22, 24, 25, 27, 28, 33, 36] and the same type of cells yielded different growth factor levels, when cell number, culture medium and condition, and CM processing were different [6, 24].Moreover, growth factor measures also differed, that is, pg/m L or ng/m L [6, 8, 10, 13, 17, 24, 27, 28, 33], pg/μg DNA [9, 36], fg/cell [25], spot density [5], and positive/negative [20] (Table 3).The use of secretome containing CM has several advantages compared to the use of stem cells, as CM can be manufactured, freeze-dried, packaged, and transported more easily.

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