Amniotic stem cells
Amniotic stem cells are the mixture of stem cells that can be obtained from the amniotic fluid  as well as the amniotic membrane. They can develop into various tissue types including skin, cartilage, cardiac tissue, nerves, muscle, and bone. The cells also have potential medical applications, especially in organ regeneration.
The stem cells are usually extracted from the amniotic sac by amniocentesis which occurs without harming the embryos. The use of amniotic fluid stem cells is therefore generally considered to lack the ethical problems associated with the use of cells from embryos.
In 2009, the first US amniotic stem cell bank was opened in Medford, MA, by Biocell Center, an international company specializing in the cryopreservation and private banking of amniotic fluid stem cells.
The presence of embryonic and foetal cells from all germ layers in the amniotic fluid was gradually determined since the 1980s. Haematopoietic progenitor cells were first reported to be present in the amniotic fluid in 1993, specifically up to the 12th week of pregnancy. It was suggested that these originated from the yolk sac.
In 1996, a study indicated that non-haematopoietic progenitor cells were also present in the amniotic fluid. This was later confirmed as mesenchymal stem cells were obtained. In addition, evidence indicated that embryonic stem cells are part of the fluid, although in very small quantities.
At around the same time, it was determined that stem cells from the amniotic membrane also have multipotent potential. AS their differentiation into neural and glial cells as well as hepatocyte precursors was observed.
The majority of stem cells present in the amniotic fluid share many characteristics, which suggests they may have a common origin.
In 2007, it was confirmed that the amniotic fluid contains a heterogeneous mixture of multipotent cells after it was demonstrated that they were able to differentiate into cells from all three germ layers but they could not form teratomas following implantation into immunodeficient mice. This characteristic differentiates them from embryonic stem cells but indicates similarities with adult stem cells. However, foetal stem cells attained from the amniotic fluid are more stable and more plastic than their adult counterparts making it easier for them to be reprogrammed to a pluripotent state.
A variety of techniques has been developed for the isolation and culturing of amniotic stem cells. One of the more common isolation methods involves the removal of amniotic fluid by amniocentesis. The cells are then extracted from the fluid based on the presence of c-Kit. Several variations of this method exist. There is some debate whether c-Kit is a suitable marker to distinguish amniotic stem cells from other cell types because cells lacking c-Kit also display differentiation potential. Culture conditions may also be adjusted to promote the growth of a particular cell type.
Mesenchymal Stem Cells
Mesenchymal stem cells (MSCs) are highly abundant in the amniotic fluid and several techniques have been described for their isolation. They usually involve the removal of amniotic fluid by amniocentesis and their distinction from other cells may be based on their morphology or other characteristics.
Human leukocyte antigen testing has been utilised to confirm that the MSCs stem from the fetus and not from the mother. Originally it was proposed that the MSCs were discarded from the embryo at the end of their life cycle but since the cells remained viable in the amniotic fluid and were able to proliferate in culture this hypothesis was overturned. However, it remains unclear whether the cells originate from the fetus itself, the placenta or possibly the inner cell mass of the blastocyst.
Comparison of amniotic fluid-derived MSCs to bone-marrow-derived ones showed that the former has a higher expansion potential in culture. However, the cultured amniotic fluid-derived MSCs have a similar phenotype to both adult bone-marrow-derived MSCs and MSCs originating from second trimester fetal tissue. In animals, the MSCs seem to have a unique immunological profile which was observed after their isolation and in vitro culturing.
Embryonic-like stem cells
As opposed to mesenchymal stem cells, embryonic-like stem cells are not abundant in the amniotic fluid, making up less than 1% of amniocentesis samples. Embryonic-like stem cells were originally identified using markers common to embryonic stem cells such as nuclear Oct4, CD34, vimentin, alkaline phosphatase, stem cell factor and c-Kit. However, these markers were not necessarily concomitantly expressed. In addition, all of these markers can occur on their own or in some combination in other types of cells.
The pluripotency of these embryonic-like stem cells remains to be fully established. Although those cells which expressed the markers were able to differentiate into muscle, adipogenic, osteogenic, nephrogenic, neural and endothelial cells, this did not necessarily occur from a homogenous population of undifferentiated cells. Evidence in favour of their embryonic stem cell nature is the cells’ ability to produce clones.
The use of amniotic stem cells instead of embryonic stem cells may be advantageous in some cases for various reasons including that the former do not form teratomas. Their enhanced stability and plasticity compared to adult stem cells may also be an advantage. Stem cells from both the amniotic fluid and membrane are utilised for therapeutic approaches.
Foetal tissue engineering
Possible applications include the use of amniotic stem cells for foetal tissue engineering to reconstruct birth defects in infants. This would circumvent the complications that are often associated with harvesting stem cells from foetal tissue. A small amount of amniotic fluid provides a large enough quantity of cells for the tissue engineering process and could help correct a number of defects including diaphragmatic hernia and possibly repair premature membrane rupture during pregnancy. If frozen and banked, the cells may also be used for similar purpose later in life.
Cardiovascular tissue engineering
Several studies have been carried out to investigate the potential of amniotic stem cells to differentiate into cardiac cells. Although c-Kit sorted cells express some genes common in cardiac cells, success in this area is still limited. Co-culturing, i.e. mixing cells and plating them together, of human amniotic stem cells with neonatal rat ventricular myocytes (NRVM) caused the cells to form functional gap junctions with each other, an indicator for cardiac-like cells. However, these results may be due to the specific features of the NRVM or fusion of the cells rather than the amniotic stem cell’s own potential to differentiate into cardiac cells. In general, these types of techniques are considered to be potentially significant but further investigations are required.
Another area of interest is the use of these cells for improvement of cardiac tissue following a myocardial infarction. Several strategies have been tested in rats including the injection of dissociated amniotic stem cells into the infarct region, which yielded conflicting results from several research groups. In contrast, injection of amniotic stem cell aggregates seems to improve the function of the tissue significantly by reducing the size of the infarct area and improving the function of the left ventricle. In addition, vasculature density has been shown to increase. Injection of cells immediately following the infarct is particularly beneficial as the cells protect the cardiac tissue from further damage.
Kidney injury repair
Following the discovery that amniotic stem cells are able to differentiate into renal cells, this was further explored in several studies. These showed that in vitro the cells were able to contribute to early kidney structures as well as being able to integrate into early kidney structures ex vivo and continue their development into mature nephrons. Results obtained for the use of amniotic stem cells in the postnatal kidney were far less encouraging as the cell’s contribution to the tissue was very small. However, the cells were able to exert a protective effect on tubular cells in mice with acute tubular necrosis.
Amniotic stem cells can also be used to treat chronic damage. This was shown in mouse models for Alport syndrome, where the cells prolonged survival of the animals by slowing down the progression of the disease. The same effect was observed in mouse models where human amniotic stem cells were used to treat uretral obstruction.
The use of foetal cells has been highly controversial because the tissue is usually obtained from the foetus following induced abortion. In contrast, foetal stem cells in the amniotic fluid can be obtained through routine prenatal testing without the need for abortion or foetal biopsy.
- Fauza, D. (2004). "Amniotic fluid and placenta stem cells". Best Practice & Research Clinical Obstetics and Gynaecology 18: 877–891. doi:10.1016/j.bpobgyn.2004.07.001.
- Cananzi, Mara; Atala, Anthony; De Coppi, Paolo (2009). "Stem cells derived from amniotic fluid: new potentials in regenerative medicine". Reproductive biomedicine online 18 (Suppl 1): 17–27. doi:10.1016/s1472-6483(10)60111-3. PMID 19281660.
- De Coppi, Paolo; Bartsch, Georg; Siddiqui, M. Minhaj; Xu, Tao; Santos, Cesar C.; Perin, Laura; Mostoslavsky, Gustavo; Serre, Angéline C.; Snyder, Evan Y.; Yoo, James J.; Furth, Mark E.; Soker, Shay; Atala, Anthony (February 2007). "Isolation of amniotic stem cell lines with potential for therapy" (PDF). Nature Biotechnology 25 (1): 100–106. doi:10.1038/nbt1274. PMID 17206138.
- Kaviani, A; Perry, T E; Dzakovic, A; Jennings, R W; Ziegler, M M; Fauza, D O (November 2001). "The amniotic fluid as a source of cells for fetal tissue engineering". Journal of pediatric surgery 36 (11): 1662–1665. doi:10.1053/jpsu.2001.27945. PMID 11685697.
- Sessarego, Nadia; Parodi, Alessia; Podestà, Marina; Benvenuto, Federica; Mogni, Massimo; Raviolo, Valentina; Lituania, Mario; Kunkl, Annalisa; Ferlazzo, Guido; Bricarelli, Franca Dagna; Uccelli, Antonio; Frassoni, Francesco (March 2008). "Multipotent mesenchymal stromal cells from amniotic fluid: solid perspectives for clinical application" (PDF). Haematologica 93 (3): 339–346. doi:10.3324/haematol.11869. PMID 18268281.
- Siegel, Nicol; Valli, Alessandro; Fuchs, Christiane; Rosner, Margit; Hengstschläger, Markus (December 2009). "Induction of mesenchymal/epithelial marker expression in human amniotic fluid stem cells". Reproductive biomedicine online 19 (6): 838–846. doi:10.1016/j.rbmo.2009.09.015. PMID 20031026.
- Steigman, Shaun A; Armant, Myriam; Bayer-Zwirello, Lucy; Kao, Grace S; Silberstein, Leslie; Ritz, Jerome; Fauza, Dario O (June 2008). "Preclinical regulatory validation of a 3-stage amniotic mesenchymal stem cell manufacturing protocol". Journal of pediatric surgery 43 (6): 1164–1169. doi:10.1016/j.jpedsurg.2008.02.052. PMC 2478751. PMID 18558201.
- Walther, Guillaume; Gekas, Jean; Bertrand, Olivier F (1 June 2009). "Amniotic stem cells for cellular cardiomyoplasty: promises and premises". Catheterization and Cardiovascular Interventions 73 (7): 917–924. doi:10.1002/ccd.22016. PMID 19455667.
- Zhang, Ping; Baxter, Jason; Vinod, Kateki; Tulenko, Thomas N; Di Muzio, Paul J (November 2009). "Endothelial differentiation of amniotic fluid-derived stem cells: synergism of biochemical and shear force stimuli". Stem Cells and Development 18 (9): 1299–1308. doi:10.1089/scd.2008.0331. PMC 3139996. PMID 19508152.
- Kim, M.K,, Kim, E.Y.; Lee, K-B. (2014). "The potential of mesenchymal stem cells derived from amniotic membrane and amniotic fluid for neuronal regenerative therapy.". BMB Rep 47: 135–140. doi:10.5483/BMBRep.2014.47.3.289.
- Antonucci, Ivana; Iezzi, Irene; Morizio, Elisena; Mastrangelo, Filiberto; Pantalone, Andrea; Mattioli-Belmonte, Monica; Gigante, Antonio; Salini, Vincenzo; Calabrese, Giuseppe; Tete, Stefano; Palka, Giandomenico; Stuppia, Liborio; Morizio, E; Mastrangelo, F; Pantalone, A; Mattioli-Belmonte, M; Gigante, A; Salini, V; Calabrese, G; Tetè, S; Palka, G; Stuppia, L (16 February 2009). "Isolation of osteogenic progenitors from human amniotic fluid using a single step culture protocol". BMC Biotechnology 9: 9. doi:10.1186/1472-6750-9-9. PMC 2654889. PMID 19220883.
- Perin, L; Giuliani, S; Jin, D; Sedrakyan, S; Carraro, G; Habibian, R; Warburton, D; Atala, A; De Filippo, R E (December 2007). "Renal differentiation of amniotic fluid stem cells". Cell proliferation 40 (6): 936–948. doi:10.1111/j.1365-2184.2007.00478.x. PMID 18021180.
- Perin, Laura; Sedrakyan, Sargis; Da Sacco, Stafano; De Filippo, Roger (2008). "Characterization of human amniotic fluid stem cells and their pluripotential capability". Methods in cell biology. Methods in Cell Biology 86: 85–99. doi:10.1016/S0091-679X(08)00005-8. ISBN 9780123738769. PMID 18442645.
- Prusa, Andrea-Romana; Marton, Erika; Rosner, Margit; Bettelheim, Dieter; Lubec, Gent; Pollack, Arnold; Bernaschek, Gerhard; Hengstschläger, Markus (July 2004). "Neurogenic cells in human amniotic fluid". American Journal of Obstetrics and Gynecology 191 (1): 309–314. doi:10.1016/j.ajog.2003.12.014. PMID 15295384.
- Schmidt, Dörthe; Achermann, Josef; Odermatt, Bernhard; Genoni, Michele; Zund, Gregor; Hoerstrup, Simon P (July 2008). "Cryopreserved amniotic fluid-derived cells: a lifelong autologous fetal stem cell source for heart valve tissue engineering". The Journal of Heart Valve Disease 17 (4): 446–455; discussion 455. PMID 18751475.
- Siegel, N; Rosner, M; Hanneder, M; Freilinger, A; Hengstschläger, M (August 2008). "Human amniotic fluid stem cells: a new perspective". Amino Acids 35 (2): 291–293. doi:10.1007/s00726-007-0593-1. PMID 17710362.
- Abdi, Reza; Fiorina, Paolo; Adra, Chaker N; Atkinson, Mark; Sayegh, Mohamed H (July 2008). "Immunomodulation by mesenchymal stem cells: a potential therapeutic strategy for type 1 diabetes". Diabetes 57 (7): 1759–1767. doi:10.2337/db08-0180. PMC 2453631. PMID 18586907.
- Centeno, Christopher J; Busse, Dan; Kisiday, John; Keohan, Cristin; Freeman, Michael; Karli, David (June 2008). "Increased knee cartilage volume in degenerative joint disease using percutaneously implanted, autologous mesenchymal stem cells". Pain physician 11 (3): 343–353. PMID 18523506.
- Fuchs, Julie R; Kaviani, Amir; Oh, Jung-Tak; LaVan, David; Udagawa, Taturo; Jennings, Russell W; Wilson, Jay M; Fauza, Dario O (June 2004). "Diaphragmatic reconstruction with autologous tendon engineered from mesenchymal amniocytes". Journal of Pediatric Surgery 39 (6): 834–838. doi:10.1016/j.jpedsurg.2004.02.014. PMID 15185207.
- Hauser, Peter V; De Fazio, Roberta; Bruno, Stefania; Sdei, Simona; Grange, Cristina; Bussolati, Benedetta; Benedetto, Chiara; Camussi, Giovanni (October 2010). "Stem cells derived from human amniotic fluid contribute to acute kidney injury recovery". The American Journal of Pathology 177 (4): 2011–2021. doi:10.2353/ajpath.2010.091245. PMC 2947295. PMID 20724594.
- Kunisaki, Shaun M; Freedman, Deborah A; Fauza, Dario O (April 2006). "Fetal tracheal reconstruction with cartilaginous grafts engineered from mesenchymal amniocytes". Journal of pediatric surgery 41 (4): 675–682; discussion 675–682. doi:10.1016/j.jpedsurg.2005.12.008. PMID 16567175.
- Le Blanc, Katarina; Frassoni, Francesco; Ball, Lynne; Locatelli, Franco; Roelofs, Helene; Lewis, Ian; Lanino, Edoardo; Sundberg, Berit; Bernardo, Maria Ester; Remberger, Mats; Dini, Giorgio; Egeler, R Maarten; Bacigalupo, Andrea; Fibbe, Willem; Ringdén, Olle; Developmental Committee of the European Group for Blood and Marrow Transplantation (10 May 2008). "Mesenchymal stem cells for treatment of steroid-resistant, severe, acute graft-versus-host disease: a phase II study". Lancet 371 (9624): 1579–1586. doi:10.1016/S0140-6736(08)60690-X. PMID 18468541.
- Parolini, Ornella; Soncini, Maddalena; Evangelista, Marco; Schmidt, Dörthe (March 2009). "Amniotic membrane and amniotic fluid-derived cells: potential tools for regenerative medicine?". Regenerative medicine 4 (2): 275–291. doi:10.2217/17460718.104.22.1685. PMID 19317646.
- Steigman, Shaun A; Ahmed, Azra; Shanti, Rabie M; Tuan, Rocky S; Valim, Clarissa; Fauza, Dario O (June 2009). "Sternal repair with bone grafts engineered from amniotic mesenchymal stem cells". Journal of pediatric surgery 44 (6): 1120–1126; discussion 1126. doi:10.1016/j.jpedsurg.2009.02.038. PMC 3556735. PMID 19524727.
- Jacot, J.G., Petsche Connell, J.; Camci-Unal, G.; Khademhosseini, A. (2013). "Amniotic Fluid-Derived Stem Cells for Cardiovascular Tissue Engineering Applications". Tissue Engineering 19: 368–379. doi:10.1089/ten.teb.2012.0561.
- De Coppi, P., Morigi, M. (2014). "Cell Therapy for Kidney Injury: Different Options and Mechanisms – Mesenchymal and Amniotic Fluid Stem Cells". Nephron Exp Nephrol 126: 59–63. doi:10.1159/000360667.
- Moschidou, D.; et al. (2012). "Valproic acid confers functional pluripotency to human amniotic fluid stem cells in a transgene-free approach.". Mol Ther 20: 1953–1967. doi:10.1038/mt.2012.117.
- Soker, S., Guan, X.; Delo, D.M.; Attala, A. (2011). "In vitro cardiomyogenic potential of human amniotic fluid stem cells". J Tissue Eng Regen Med 5: 220–228. doi:10.1002/term.308.
- Wang, J.J., Lee, W.Y.; Wei, H.J.; Lin, W.W.; Yeh, Y.C.; Hwang, S.M. (2011). "Enhancement of cell retention and functional benefits in myocardial infarction using human amniotic-fluid stem-cell bodies enriched with endogenous ECM.". Biomaterials 32: 5558–5567. doi:10.1016/j.biomaterials.2011.04.031.
- Hsu, L.W., Yeh, Y.C.; Lee, W.Y.; Yu, C.L.; Hwang, S.M.; Chung, M.F. (2010). "Cardiac repair with injectable cell sheet fragments of human amniotic fluid stem cells in an immune-suppressed rat model.". Biomaterials 31: 6444–6453. doi:10.1016/j.biomaterials.2010.04.069.
- Bollini, S.; et al. (2011). "Amniotic fluid stem cells are cardioprotective following acute myocardial infarction.". Stem Cells Dev 20: 1985–1994. doi:10.1089/scd.2010.0424.
- Perin, L.; et al. (2007). "Renal differentiation of amniotic fluid stem cells.". Cell Prolif 40: 936–948. doi:10.1111/j.1365-2184.2007.00478.x. PMID 18021180.
- Perin, L.; et al. (2010). "Contribution of human amniotic fluid stem cells in an immunodeficient mouse model of acute tubular necrosis.". PLOS ONE 24: e9357. doi:10.1371/journal.pone.0009357.
- Sedrakyan, S.; et al. (2012). "Injection of amniotic fluid stem cells delays progression of renal fibrosis.". J Am Soc Nephrol 23: 661–673. doi:10.1681/ASN.2011030243.
- Sun, D.; et al. (2013). "Therapeutic effects of human amniotic fluid-derived stem cells on renal interstitial fibrosis in a murine model of unilateral ureteral obstruction.". PLOS ONE 8: e65042. doi:10.1371/journal.pone.0065042.