About this Journal Submit a Manuscript Table of Contents
BioMed Research International
Volume 2014 (2014), Article ID 965849, 14 pages
http://dx.doi.org/10.1155/2014/965849
Review Article

Prospect of Stem Cell Conditioned Medium in Regenerative Medicine

Department of Histology, Faculty of Medicine, University of Indonesia, Jalan Salemba 6, Jakarta 10430, Indonesia

Received 11 May 2014; Revised 22 July 2014; Accepted 25 July 2014; Published 28 August 2014

Academic Editor: Antonio Salgado

Copyright © 2014 Jeanne Adiwinata Pawitan. 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.

Abstract

Background. Stem cell-derived conditioned medium has a promising prospect to be produced as pharmaceuticals for regenerative medicine. Objective. To investigate various methods to obtain stem cell-derived conditioned medium (CM) to get an insight into their prospect of application in various diseases. Methods. Systematic review using keywords “stem cell” and “conditioned medium” or “secretome” and “therapy.” Data concerning treated conditions/diseases, type of cell that was cultured, medium and supplements to culture the cells, culture condition, CM processing, growth factors and other secretions that were analyzed, method of application, and outcome were noted, grouped, tabulated, and analyzed. Results. Most of CM using studies showed good results. However, the various CM, even when they were derived from the same kind of cells, were produced by different condition, that is, from different passage, culture medium, and culture condition. The growth factor yields of the various types of cells were available in some studies, and the cell number that was needed to produce CM for one application could be computed. Conclusion. Various stem cell-derived conditioned media were tested on various diseases and mostly showed good results. However, standardized methods of production and validations of their use need to be conducted.

1. Introduction

Data of the use of stem cells in various diseases are accumulating. Some studies reported beneficial effects of stem cell therapy in degenerative diseases such as myocardial infarction and revealed that stem cells cause tissue repair due to their ability to secrete trophic factors that exert beneficial impact on the damaged tissue, rather than their capacity to differentiate into the needed cells [1]. 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].

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. Moreover, as it is devoid of cells; there is no need to match the donor and the recipient to avoid rejection problems. Therefore, stem cell-derived conditioned medium have a promising prospect to be produced as pharmaceuticals for regenerative medicine.

To date, no clinical trial that used CM for a certain disease has been reported, except two pilot studies on the use of adipose derived mesenchymal stem cell CM for hair follicle regeneration [3] and fractional carbon dioxide resurfacing wound healing [4] in human, which showed good results. The use of CM for therapy is very appealing and may be booming in the near future, as studies on the use of CM for various diseases are accumulating [1, 333]. Conditioned medium contains various growth factors and tissue regenerative agents, which were secreted by the stem cells. The fact that stem cells secrete various growth factors was also shown by various proteomic studies, which revealed the presence of various growth factors and other cytokines in the CM [5, 79, 13, 17, 20, 22, 28, 34, 35].

However, various studies reported the use of various kinds of stem cells and various methods to get the CM to cure various kinds of degenerative diseases in various animal models. Therefore, this systematic review aimed to investigate the various methods to get the CM and the various diseases that were treated, to get an insight into the various kinds of CM and their application benefit in various diseases.

2. Materials and Methods

We performed “all text” searches without time restriction on January 23, 2014, in Pubmed/Medline using keywords “stem cell” and “conditioned medium” or “secretome” and “therapy,” “all text” searches in Cochrane library (trials) using keywords “secretome” or “conditioned medium,” and “all text” searches in ClinicalTrials.gov using keywords “stem cell” and “conditioned medium” or “secretome” and “therapy.” In addition, relevant existing articles in our library were added.

Inclusion criteria are all studies that used CM for a certain disease. Exclusion criteria are studies that did not contain complete data concerning subject condition/disease model, source of CM, and outcome of treatment with CM.

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. Further, to know the growth factor yields of the various types of cells, when available, growth factor levels were tabulated and grouped according to types of cells that yielded the growth factor containing conditioned medium, in relation to the number of cells, type and duration of culture, and processing of the conditioned medium. When the data was available, the number of cells that were needed to produce the CM for one application was computed.

3. Results and Discussion

We got 39 articles that met the inclusion criteria, and 7 were excluded due to incomplete data. Various conditions/diseases were treated by various cell-derived CM and mostly showed promising results (Table 1).

tab1
Table 1: Studies on various subjects, conditions, source of conditioned medium, and outcome.

The various conditioned media, even when they were derived from same kind of cells, were produced by different condition, that is, from different passage, number of cells, culture medium, and culture condition (Table 2). The growth factor yields of the various types of cells can be seen in Table 3, and the cell number that is needed to produce CM for one application can be seen in Table 4.

tab2
Table 2: Cell type, medium, culture condition, cell number, duration, passage, and processing of conditioned medium.
tab3
Table 3: Growth factor level from various cell sources, culture duration, cell number and processing of conditioned medium.
tab4
Table 4: Cell number to produce CM per application, volume, and mode of delivery of various cell sources for various conditions and the outcome.

Various studies showed that conditioned medium have been tested in various kinds of diseases/conditions (Table 1) [1, 333], that is, alopecia [3, 5], acute and chronic hind limb ischemia [69], acute and chronic wound healing [4, 1014], myocardial infarct [1, 1518], acute liver injury/failure [1922], cerebral injury/ischemia/stroke [2327], 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 (huESC-MSC) CM showed decreased systolic blood pressure and proteinuria and improvement in tubular and glomerular damage, renal blood flow, and glomerular filtration rate [29]. However, nephropathy that was treated using CM from human umbilical cord blood unrestricted somatic stem cell (huUCB-USSC) or mouse bone marrow mesenchymal stem cell (mBM-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].

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 mBM-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.

The conditioned medium can be harvested from various kinds of cells (Table 2). Moreover, there are various methods to get the conditioned medium, which may interfere with the growth factor types and levels that were harvested by the methods. Only some of the various studies using CM checked the growth factor levels (Table 3) [510, 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/mL or ng/mL [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 measure of pg/μg DNA and fg/cell can be computed into pg or ng/mL provided the DNA content/cell and cell number is known. However, in some studies, the exact cell number that was used to produce the CM was not mentioned [7, 8, 10, 13, 28, 33, 36]. In addition, most studies measured different sets of growth factors and other cytokines/factors (Table 3).

3.1. Culture Medium and Supplement

Some studies used fetal bovine serum or other supplement containing complete medium, while other studies used serum-free media. Moreover, the basal media used were variable, for example, αMEM, DMEM, DMEM/F12, M199, EBM2, EGM-2, in vivo 15, or chemically defined medium, and the same type of cell might be cultured in different kind of basal medium (Table 2). Culture medium in in vitro culture represents microenvironment in in vivo condition and may determine cell fate and thus cell secretion [37]. Therefore, the same type of cells may secrete different level of growth factors when they were cultured in different medium, as can be seen in Table 3 [25, 27].

3.2. Culture Duration

Production of CM varies in culture duration from sixteen hours to five days (Table 3). In case complete medium was used, short culture duration might leave certain serum derived growth factors that was not consumed by the cells and might add to the growth factor level, or, on the contrary, suppress growth factor secretion by the cells. Possibility of the presence of residual growth factor from the medium can be seen in a study, which showed that medium without cell contained a TGF-b1 level of  pg/mL (Table 3) [24].

3.3. Culture Condition

Some studies produce CM from cell culture in normoxia (O2 level 20-21%) and variable oxygen deprived (hypoxia O2 level 0.5%, 1%, 1.5%, and 2%) condition (Table 2). Some studies on various stem cells showed that most growth factors were upregulated in hypoxia condition, for example, vascular endothelial derived growth factor (VEGF) [5, 8, 27], hepatocyte growth factor (HGF) [8, 27], platelet derived growth factor (PDGF) [5, 8], placenta growth factor (PlGF) [25], and insulin-like growth factor II (IGF-II) [5], except epidermal growth factor (EGF) that was downregulated [5]. However, another study showed the contrary, that is, down regulation of VEGF and HGF in hypoxia condition [25].

Most studies produced CM in monolayer culture, but several studies used spheroid cultures (Table 3). Spheroid cultures need a special handling and equipment (spinner flask) but yield more cells compared to conventional monolayer cultures, and thus more secreted factors [6, 24] (Table 4). In addition, cells located at the center of the spheroid may be in relative hypoxic condition compared to cells on the surface, thus further increasing certain growth factor yield.

3.4. Secreted Factor’s Role in Improvement of Diseases

Various cytokines were secreted by stem cells into the CM, and they played a role in the improvement of various diseases/conditions. Those cytokines can be grouped into growth factors, proinflammatory and anti-inflammatory cytokines, and other cytokines. Various studies used various methods to assess various cytokines in the conditioned CM, from the conventional ELISA assays [6, 10, 24, 25, 27, 33, 36] to proteomic profiling methods [5, 79, 13, 17, 20, 22, 28, 34, 35].

3.4.1. Growth Factors

Growth factors that are secreted by various kinds of stem cells are vascular endothelial derived growth factor (VEGF) [5, 6, 8, 10, 13, 17, 24, 25, 27, 33, 36], platelet derived growth factor (PDGF) [5, 8, 10, 13, 24], epidermal growth factor (EGF) [5, 10, 13, 20], insulin-like growth factor I (IGF-I) [33, 36], insulin-like growth factor II (IGF-II) [5], hepatocyte growth factor (HGF) [6, 8, 20, 25, 27, 33], fibroblast growth factor 2/basic fibroblast growth factor (FGF-2/bFGF) [6, 7, 10, 13], keratinocyte growth factor/fibroblast growth factor 7 (KGF/FGF-7) [10, 20], platelet derived endothelial cell growth factor (PDEGF) [20], heparin binding epidermal growth factor (HEGF) [20], placenta growth factor (PlGF) [25], neural growth factor (NGF) [28], and brain derived neurotrophic factor (BDNF) [28].

Further, studies that analyzed various growth factors reported the presence of the various growth factors, which were secreted by various stem cells into their conditioned medium (Table 3), except for human MSC (Lonza) that did not secrete FGF-2, PDGFBB, BMP-2, and SDF-1 but secreted IGF-1, VEGF, TGF β1, and HGF [33]. Moreover, different culture condition and medium may yield different level of growth factor secretions [6].

3.4.2. Pro- and Anti-Inflammatory Cytokines

Anti-inflammatory cytokines that are secreted by stem cells are TGFβ1 [9, 10, 20, 24, 33] and some interleukins (IL), that is, IL-6 [9, 13, 17, 25, 28], IL-10, IL-27, IL-17E, IL-13, IL-12p70, and IL-1 receptor antagonist (IL-1ra) [20], while the secreted proinflammatory cytokines are IL-8/CXCL-8 [8, 9, 13], IL-9 [13, 35], and IL-1b [20].

3.4.3. Other Cytokines

Other secreted factors are leptin [7], angiogenin [8], granulocyte colony stimulating factor (GCSF) [5, 10], granulocyte macrophage CSF (GM-CSF) [5, 10, 13], macrophage CSF (MCSF) [5], fractalkine [13], monocyte chemotactic protein (MCP-1) [9, 13, 17, 20], serpin E-1 [20], endostatin/collegen XVIII [20], UPA, thrombospondins 1 and 2 [20], tissue inhibitor of metalloproteinase-1 (TIMP-1) [20], IGF binding protein (IGFBP) [5, 20], stem cell-derived factor 1 (SDF-1)/CXCL-12 [69, 20, 25], adrenomedullin (ADM) [25], Dickkopf-1 (DKK-1) [25], and receptors, that is, MCSF receptor (MCSFR) [5] and PDGF receptor (PDGFR) [5].

3.5. Translation of Conditioned Medium Usage in Patients

In conditioned medium, various factors may be present as a cocktail and act in concert to promote regeneration. Therefore, it is important to analyze a complete set of growth factor and cytokine levels for every kind of stem cell-derived conditioned medium and to know the culture condition, conditioned medium processing, and diseases/conditions that are responsive to a certain conditioned medium treatment. When the content of the various cytokines in a certain conditioned medium is known, the result of the conditioned medium on a certain disease/condition can be determined, and the way to translation into patients is open.

From studies that analyzed VEGF level we can conclude that most stem cells secrete VEGF. As VEGF plays a role on angiogenesis [36] that is important in regeneration of injured/damaged tissues/organs, various stem cell-derived conditioned media are able to cure various diseases and will have more impact on diseases with ischemia. In addition, VEGF may prevent apoptosis in hypoxic condition, thus preventing further damage [6].

Concerning angiogenesis, other than VEGF, other growth factors that may play a role in angiogenesis are FGF2 [7, 38], EGF [7], HGF [7, 8], PlGF [7], SDF-1 [7], PDGF [7, 38], TGFβ1 [38], and PDEGF [39]. In addition, various cytokines, that is, interleukin [38], IL-8 [8, 9, 13], chemokines [38], monocyte chemotactic protein (MCP-1) [9, 13, 17, 20], leptin [7], angiogenin [8], and endostatin/collagen XVIII [20], also play a role in angiogenesis.

Moreover, FGF2 is a more potent angiogenic factor compared to VEGF, with additional effect on proliferation of fibroblasts, preadipocytes, and endothelial, epithelial, and neural stem cells, on migration of neural crest derived glial and myogenic cells and on differentiation of neuroepithelial cells into mature neurons and glial cells [38].

Other growth factors contribute in the regeneration of injured/damaged tissue organs, with special emphasis on proliferation, that is, PDGF for connective tissue, glial, and other cells, EGF for mesenchymal, glial, and epithelial cells, and IGF-I and IGF-II for various kinds of cells [40]. In addition, PlGF that is a member of VEGF family increases the activity of VEGF in vitro and in vivo [41], KGF inhibits oxidative stress induced epithelial cell death [42], NGF promotes neurite outgrowth and neural cell survival [40], BDNF is neuroprotective, promotes cell survival, and reduces astroglial scar formation [28], and some growth factors, including HEGF, FGF-7, EGF, and HGF promote liver regeneration [20].

Proinflammatory cytokines that play a role in regeneration are IL-1b due to its liver protective role [20], IL-8 due to its angiogenic activity [8, 9, 13], and IL-9 due to wound healing promotion activity [13, 43]. In addition, anti-inflammatory cytokines prevent inflammation and promote liver regeneration [20].

Other cytokines, that is, UPA and thrombospondins 1 and 2, promote liver regeneration [20], serpin E-1 [20] and SDF-1 [69, 20, 25] promote tissue repair [20], TIMP-1 and IGFBP [5, 20] prevent apoptosis [20], ADM causes vasodilatation and reduces cellular oxidative stress and apoptosis [25], DKK-1 initiates bone marrow stem cell proliferation [25], and fractalkine prevents apoptosis [13, 44].

Various colony stimulating factors, that is, granulocyte colony stimulating factor (GCSF) [5, 10], granulocyte macrophage CSF (GM-CSF) [5, 10, 13], and macrophage CSF (MCSF) [5], may recruit various resident stem cells/progenitor cells including endothelial progenitors to site of injury/damage and promote wound healing process [10, 13] or hair growth [5].

MCSF receptor (MCSFR) [5] promotes myeloid progenitor, mononuclear phagocyte, and placental trophoblast growth and development [45], and PDGFR [5] may interact with various signaling molecules or integrin to cause cell proliferation, motility, differentiation, or survival by apoptosis inhibition [46].

Moreover, one factor may contribute to more than one mode of regenerative action, such as MCP-1 that is involved in angiogenesis [9, 13, 17, 20] and liver protection activity [20]. Further, for production of CM to be applied in various human diseases, data from animal studies that showed promising outcome are very valuable.

3.5.1. Production of CM for Translation into Various Human Diseases

To use CM for various human diseases, production method of the CM needs to be standardized in terms of the type and number of cells that were needed to produce the CM, culture medium and condition, and conditioned medium processing. In addition, the volume and mode of delivery are also important. As various studies used various numbers and type of cells and various doses of CM, it is important to know the number of cells that yielded the CM for one application, which may be interpolated for human studies. Therefore, in Table 4 we summarized all data that may be needed for interpolation into human studies, that is, diseases that were treated, species and age or body weight of the animal, type of cell, culture medium and condition, number of cells to produce CM for one application, volume, and mode of application. Moreover, various possible applications of CM for various conditions are summarized in Figure 1.

965849.fig.001
Figure 1: Various possible applications of CM for various conditions.

In addition, for translation into patients, it is very important to analyze and to note the various cytokine contents of the various conditioned media. Further, for every conditioned medium with known cytokine content, validation of its use on various diseases needs to be conducted. Finally, the possibility of promotion of existing cancer should be tested for every CM, and caution should be taken before CM therapy to ensure that the recipient is free from cancer.

Advantages of production of various CM for patients lie in the possibility of mass production by pharmaceutical companies, when production methods have been standardized. Conditioned media are not like stem cells that need a good manufacturing practice (GMP) facility to be applied to patients [47]. When CM has been packaged properly, it can be transported easily as drugs and does not need cryopreservation, such as that the stem cells need. However, compared to stem cells that may survive for a rather long period, CM needs to be given more frequently, as cytokines’ and growth factors’ half-lives are mostly shorter [48, 49], which is a disadvantage for the patients but will give more profit to pharmaceutical companies.

4. Conclusion

Various stem cell-derived conditioned media were produced by various methods and processing and tested on various diseases and mostly showed good results. However, standardized methods for various conditioned media production and validations of their use on various diseases need to be conducted.

Conflict of Interests

The author declares that there is no conflict of interests regarding the publication of this paper.

Acknowledgment

This study was funded by the research grant from Indonesian Ministry of Education and Culture (Pusnas 2014), Contract no. 2218/H2.R12/HKP.05.00/2014.

References

  1. D. Yang, W. Wang, L. Li et al., “The relative contribution of paracine effect versus direct differentiation on adipose-derived stem cell transplantation mediated cardiac repair,” PLoS ONE, vol. 8, no. 3, Article ID e59020, 2013. View at Publisher · View at Google Scholar · View at Scopus
  2. H. O. Kim and S. Choi, “Mesenchymal stem cell-derived secretome and microvesicles as a cell-free therapeutics for neurodegenerative disorders,” Tissue Engineering and Regenerative Medicine, vol. 10, no. 3, pp. 93–101, 2013. View at Publisher · View at Google Scholar · View at Scopus
  3. H. Fukuoka, H. Suga, K. Narita, R. Watanabe, and S. Shintani, “The latest advance in hair regeneration therapy using proteins secreted by adipose-derived stem cells,” American Journal of Cosmetic Surgery, vol. 29, no. 4, pp. 273–282, 2012.
  4. B. R. Zhou, Y. Xu, S. L. Guo et al., “The effect of conditioned media of adipose-derived stem cells on wound healing after ablative fractional carbon dioxide laser resurfacing,” BioMed Research International, vol. 2013, Article ID 519126, 9 pages, 2013. View at Publisher · View at Google Scholar
  5. B. S. Park, W. S. Kim, J. S. Choi et al., “Hair growth stimulated by conditioned medium of adipose-derived stem cells is enhanced by hypoxia: evidence of increased growth factor secretion,” Biomedical Research, vol. 31, no. 1, pp. 27–34, 2010. View at Publisher · View at Google Scholar · View at Scopus
  6. S. H. Bhang, S. Lee, J. Y. Shin, T. J. Lee, H. K. Jang, and B. S. Kim, “Efficacious and clinically relevant conditioned-medium of human adipose-derived stem cells for therapeutic angiogenesis,” Molecular Therapy, vol. 22, no. 4, p. 862, 2014.
  7. J. C. Y. Ho, W. Lai, M. Li et al., “Reversal of endothelial progenitor cell dysfunction in patients with type 2 diabetes using a conditioned medium of human embryonic stem cell-derived endothelial cells,” Diabetes/Metabolism Research and Reviews, vol. 28, no. 5, pp. 462–473, 2012. View at Publisher · View at Google Scholar · View at Scopus
  8. S. di Santo, Z. Yang, M. W. von Ballmoos et al., “Novel cell-free strategy for therapeutic angiogenesis: in vitro generated conditioned medium can replace progenitor cell transplantation,” PLoS ONE, vol. 4, no. 5, Article ID e5643, 2009. View at Publisher · View at Google Scholar · View at Scopus
  9. T. Mirabella, M. Cilli, S. Carlone, R. Cancedda, and C. Gentili, “Amniotic liquid derived stem cells as reservoir of secreted angiogenic factors capable of stimulating neo-arteriogenesis in an ischemic model,” Biomaterials, vol. 32, no. 15, pp. 3689–3699, 2011. View at Publisher · View at Google Scholar · View at Scopus
  10. J. Kim, J. H. Lee, S. M. Yeo, H. M. Chung, and J. I. Chae, “Stem cell recruitment factors secreted from cord blood-derived stem cells that are not secreted from mature endothelial cells enhance wound healing,” In Vitro Cellular & Developmental Biology: Animal, vol. 50, no. 2, pp. 146–154, 2014. View at Publisher · View at Google Scholar
  11. J. Y. Kim, S. H. Song, K. L. Kim et al., “Human cord blood-derived endothelial progenitor cells and their conditioned media exhibit therapeutic equivalence for diabetic wound healing,” Cell Transplantation, vol. 19, no. 12, pp. 1635–1644, 2010. View at Publisher · View at Google Scholar · View at Scopus
  12. C. Shrestha, L. Zhao, K. Chen, H. He, and Z. Mo, “Enhanced healing of diabetic wounds by subcutaneous administration of human umbilical cord derived stem cells and their conditioned media,” International Journal of Endocrinology, vol. 2013, Article ID 592454, 10 pages, 2013. View at Publisher · View at Google Scholar
  13. M. J. Lee, J. Kim, K. I. Lee, J. M. Shin, J. I. Chae, and H. M. Chung, “Enhancement of wound healing by secretory factors of endothelial precursor cells derived from human embryonic stem cells,” Cytotherapy, vol. 13, no. 2, pp. 165–178, 2011. View at Publisher · View at Google Scholar · View at Scopus
  14. P. J. Mishra and D. Banerjee, “Cell-free derivatives from mesenchymal stem cells are effective in wound therapy,” World Journal of Stem Cells, vol. 4, no. 5, pp. 35–43, 2012.
  15. B. Hynes, A. H. S. Kumar, J. O'Sullivan et al., “Potent endothelial progenitor cell-conditioned media-related anti-apoptotic, cardiotrophic, and pro-angiogenic effects post-myocardial infarction are mediated by insulin-like growth factor-1,” European Heart Journal, vol. 34, no. 10, pp. 782–789, 2013. View at Publisher · View at Google Scholar · View at Scopus
  16. L. Timmers, S. K. Lim, I. E. Hoefer et al., “Human mesenchymal stem cell-conditioned medium improves cardiac function following myocardial infarction,” Stem Cell Research, vol. 6, no. 3, pp. 206–214, 2011. View at Publisher · View at Google Scholar · View at Scopus
  17. F. See, T. Seki, P. J. Psaltis et al., “Therapeutic effects of human STRO-3-selected mesenchymal precursor cells and their soluble factors in experimental myocardial ischemia,” Journal of Cellular and Molecular Medicine, vol. 15, no. 10, pp. 2117–2129, 2011. View at Publisher · View at Google Scholar · View at Scopus
  18. L. Timmers, S. K. Lim, F. Arslan et al., “Reduction of myocardial infarct size by human mesenchymal stem cell conditioned medium,” Stem Cell Research, vol. 1, no. 2, pp. 129–137, 2008. View at Publisher · View at Google Scholar · View at Scopus
  19. Z. Du, C. Wei, K. Cheng et al., “Mesenchymal stem cell-conditioned medium reduces liver injury and enhances regeneration in reduced-size rat liver transplantation,” Journal of Surgical Research, vol. 183, no. 2, pp. 907–915, 2013. View at Publisher · View at Google Scholar · View at Scopus
  20. D. S. Zagoura, M. G. Roubelakis, V. Bitsika et al., “Therapeutic potential of a distinct population of human amniotic fluid mesenchymal stem cells and their secreted molecules in mice with acute hepatic failure,” Gut, vol. 61, no. 6, pp. 894–906, 2012. View at Publisher · View at Google Scholar · View at Scopus
  21. D. van Poll, B. Parekkadan, C. H. Cho et al., “Mesenchymal stem cell-derived molecules directly modulate hepatocellular death and regeneration in vitro and in vivo,” Hepatology, vol. 47, no. 5, pp. 1634–1643, 2008. View at Publisher · View at Google Scholar · View at Scopus
  22. B. Parekkadan, D. Van Poll, K. Suganuma et al., “Mesenchymal stem cell-derived molecules reverse fulminant hepatic failure,” PLoS ONE, vol. 2, no. 9, article e941, 2007. View at Publisher · View at Google Scholar · View at Scopus
  23. T. Inoue, M. Sugiyama, H. Hattori, H. Wakita, T. Wakabayashi, and M. Ueda, “Stem cells from human exfoliated deciduous tooth-derived conditioned medium enhance recovery of focal cerebral ischemia in rats,” Tissue Engineering A, vol. 19, no. 1-2, pp. 24–29, 2013. View at Publisher · View at Google Scholar · View at Scopus
  24. Y. J. Cho, H. S. Song, S. Bhang et al., “Therapeutic effects of human adipose stem cell-conditioned medium on stroke,” Journal of Neuroscience Research, vol. 90, no. 9, pp. 1794–1802, 2012. View at Publisher · View at Google Scholar · View at Scopus
  25. B. Bakondi, I. S. Shimada, A. Perry et al., “CD133 identifies a human bone marrow stem/progenitor cell sub-population with a repertoire of secreted factors that protect against stroke,” Molecular Therapy, vol. 17, no. 11, pp. 1938–1947, 2009. View at Publisher · View at Google Scholar · View at Scopus
  26. T. J. Chuang, K. C. Lin, C. C. Chio, C. C. Wang, C. P. Chang, and J. R. Kuo, “Effects of secretome obtained from normoxia-preconditioned human mesenchymal stem cells in traumatic brain injury rats,” Journal of Trauma and Acute Care Surgery, vol. 73, no. 5, pp. 1161–1167, 2012. View at Publisher · View at Google Scholar · View at Scopus
  27. C. Chang, C. Chio, C. Cheong, C. Chao, B. Cheng, and M. Lin, “Hypoxic preconditioning enhances the therapeutic potential of the secretome from cultured human mesenchymal stem cells in experimental traumatic brain injury,” Clinical Science, vol. 124, no. 3, pp. 165–176, 2013. View at Publisher · View at Google Scholar · View at Scopus
  28. D. Cantinieaux, R. Quertainmont, S. Blacher et al., “Conditioned medium from bone marrow-derived mesenchymal stem cells improves recovery after spinal cord injury in rats: an original strategy to avoid cell transplantation,” PLoS ONE, vol. 8, no. 8, Article ID e69515, 2013. View at Publisher · View at Google Scholar · View at Scopus
  29. A. van Koppen, J. A. Joles, B. W. M. van Balkom et al., “Human embryonic mesenchymal stem cell-derived conditioned medium rescues kidney function in rats with established chronic kidney disease,” PLoS ONE, vol. 7, no. 6, Article ID e38746, 2012. View at Publisher · View at Google Scholar · View at Scopus
  30. Y. Gheisari, N. Ahmadbeigi, M. Naderi, S. M. Nassiri, S. Nadri, and M. Soleimani, “Stem cell-conditioned medium does not protect against kidney failure,” Cell Biology International, vol. 35, no. 3, pp. 209–213, 2011. View at Publisher · View at Google Scholar · View at Scopus
  31. W. Zhu, L. Huang, Y. Li et al., “Mesenchymal stem cell-secreted soluble signaling molecules potentiate tumor growth,” Cell Cycle, vol. 10, no. 18, pp. 3198–3207, 2011. View at Publisher · View at Google Scholar · View at Scopus
  32. L. Li, Y. Liu, C. Yang et al., “Improvement of ventilator-induced lung injury by IPS cell-derived conditioned medium via inhibition of PI3K/Akt pathway and IP-10-dependent paracrine regulation,” Biomaterials, vol. 34, no. 1, pp. 78–91, 2013. View at Publisher · View at Google Scholar · View at Scopus
  33. T. Inukai, W. Katagiri, R. Yoshimi et al., “Novel application of stem cell-derived factors for periodontal regeneration,” Biochemical and Biophysical Research Communications, vol. 430, no. 2, pp. 763–768, 2013. View at Publisher · View at Google Scholar · View at Scopus
  34. E. Ivanova-Todorova, I. Bochev, R. Dimitrov et al., “Conditioned medium from adipose tissue-derived mesenchymal stem cells induces CD4+FOXP3+ cells and increases IL-10 secretion,” Journal of Biomedicine and Biotechnology, vol. 2012, Article ID 295167, 8 pages, 2012. View at Publisher · View at Google Scholar · View at Scopus
  35. S. K. Sze, D. P. V. de Kleijn, R. C. Lai et al., “Elucidating the secretion proteome of human embryonic stem cell-derived mesenchymal stem cells,” Molecular and Cellular Proteomics, vol. 6, no. 10, pp. 1680–1689, 2007. View at Publisher · View at Google Scholar · View at Scopus
  36. S. Sadat, S. Gehmert, Y. Song et al., “The cardioprotective effect of mesenchymal stem cells is mediated by IGF-I and VEGF,” Biochemical and Biophysical Research Communications, vol. 363, no. 3, pp. 674–679, 2007. View at Publisher · View at Google Scholar · View at Scopus
  37. R. Goswami and M. H. Kaplan, “A brief history of IL-9,” The Journal of Immunology, vol. 186, no. 6, pp. 3283–3288, 2011. View at Publisher · View at Google Scholar
  38. Y. R. Yun, J. E. Won, E. Jeon et al., “Fibroblast growth factors: biology, function, and application for tissue regeneration,” Journal of Tissue Engineering, vol. 2010, Article ID 218142, 2010. View at Publisher · View at Google Scholar
  39. T. Saeki, M. Tanada, S. Takashima et al., “Correlation between expression of platelet-derived endothelial cell growth factor (thymidine phosphorylase ) and microvessel density in early-stage human colon carcinomas,” Japanese Journal of Clinical Oncology, vol. 27, no. 4, pp. 227–230, 1997. View at Publisher · View at Google Scholar · View at Scopus
  40. G. Litwack, “Growth factors and cytokines,” in Human Biochemistry and Disease, G. Litwack, Ed., pp. 587–683, Elsevier Academic Press, 2008.
  41. J. E. Park, H. H. Chen, J. Winer, K. A. Houck, and N. Ferrara, “Placenta growth factor: potentiation of vascular endothelial growth factor bioactivity, in vitro and in vivo, and high affinity binding to Flt-1 but not to Flk-1/KDR,” The Journal of Biological Chemistry, vol. 269, no. 41, pp. 25646–25654, 1994. View at Scopus
  42. P. Ray, Y. Devaux, D. B. Stolz et al., “Inducible expression of keratinocyte growth factor (KGF) in mice inhibits lung epithelial cell death induced by hyperoxia,” Proceedings of the National Academy of Sciences of the United States of America, vol. 100, no. 10, pp. 6098–6103, 2003. View at Publisher · View at Google Scholar · View at Scopus
  43. J. E. Turner, P. J. Morrison, C. Wilhelm et al., “IL-9-mediated survival of type 2 innate lymphoid cells promotes damage control in helminth—induced lung inflammation,” The Journal of Experimental Medicine, vol. 210, no. 13, pp. 2951–2965, 2013. View at Publisher · View at Google Scholar
  44. G. E. White and D. R. Greaves, “Fractalkine: a survivor's guide chemokines as antiapoptotic mediators,” Arteriosclerosis, Thrombosis, and Vascular Biology, vol. 32, no. 3, pp. 589–594, 2012. View at Publisher · View at Google Scholar · View at Scopus
  45. A. Mancini, A. Koch, A. D. Whetton, and T. Tamura, “The M-CSF receptor substrate and interacting protein FMIP is governed in its subcellular localization by protein kinase C-mediated phosphorylation, and thereby potentiates M-CSF-mediated differentiation,” Oncogene, vol. 23, no. 39, pp. 6581–6589, 2004. View at Publisher · View at Google Scholar · View at Scopus
  46. J. Andrae, R. Gallini, and C. Betsholtz, “Role of platelet-derived growth factors in physiology and medicine,” Genes and Development, vol. 22, no. 10, pp. 1276–1312, 2008. View at Publisher · View at Google Scholar · View at Scopus
  47. P. Wuchter, K. Bieback, H. Schrezenmeier et al., “Standardization of Good Manufacturing Practice–compliant production of bone marrow–derived human mesenchymal stromal cells for immunotherapeutic applications,” Cytotherapy, 2014. View at Publisher · View at Google Scholar
  48. P. Yde, B. Mengel, M. H. Jensen, S. Krishna, and A. Trusina, “Modeling the NF-κB mediated inflammatory response predicts cytokine waves in tissue,” BMC Systems Biology, vol. 5, article 115, 2011. View at Publisher · View at Google Scholar · View at Scopus
  49. A. Khosravi, C. M. Cutler, M. H. Kelly et al., “Determination of the elimination half-life of fibroblast growth factor-23,” The Journal of Clinical Endocrinology & Metabolism, vol. 92, no. 6, pp. 2374–2377, 2007. View at Publisher · View at Google Scholar · View at Scopus