Keywords

2.1 Introduction

Mesenchymal stem cells (MSCs) are multipotent stem cells that can differentiate into a variety of cell types, e.g., osteoblasts (bone cells), chondrocytes (cartilage cells), and adipocytes (fat cells). MSCs were first discovered by Alexander Maximow, who identified a cell type within the mesenchyme with potential to develop into various types of blood cells. McCulloch and James later revealed the clonal nature of marrow cells in 1963 (Becker et al. 1963; Siminovitch et al. 1963). An ex vivo assay for examining the potential of multipotent marrow clonogenic cells was reported in the 1970s by Friedenstein and colleagues (Friedenstein et al. 1974, 1976). MSCs were determined based on three common characteristics: ability to adhere to culture vessels with a fibroblast-like shape; expression of characteristic markers Stro-1, CD133, CD29, CD44, CD90, CD105 (SH2), SH3, SH4 (CD73), c-kit, CD71, and CD106; and ability to differentiate into specialized cells, e.g., the bone, cartilage, and fat. To easily determine which stem cells are MSCs, in 2006 the International Society of Cellular Therapy defined MSCs with som e minimal criteria (Dominici et al. 2006), including:

  1. 1.

    MSCs must be adherent to plastic under standard tissue culture conditions.

  2. 2.

    MSCs must express some specific markers such as CD73, CD90, and CD150 and lack expression of CD14, CD34, CD45 or CD11b, CD79 alpha or CD19, and HLA-DR.

  3. 3.

    MSCs must successfully differentiate into osteoblasts, adipocytes, and chondroblasts under in vitro conditions.

The first identified source of MSCs was bone marrow. MSCs are currently isolated from many different tissues in the body, such as the adipose tissue, peripheral blood, umbilical cord blood, banked umbilical cord blood, umbilical cord, umbilical cord membrane, umbilical cord vein, Wharton’s jelly of the umbilical cord, placenta, decidua basalis, ligamentum flavum, amniotic fluid, amniotic membrane, dental pulp, chorionic villi of the human placenta, fetal membranes, menstrual blood, breast milk, and urine (Fig. 2.1, Table 2.1).

Fig. 2.1
figure 1

Sources of MSCs. MSCs can be derived from several tissues in the adult or infant human body

Full size image
Table 2.1 Human MSC sources , cell surface markers, and expansion media with serum supplements
Full size table

2.2 How MSCs Can Treat Diseases?

Different than other stem cells, MSCs can be used to treat diseases by two different mechanisms, including tissue repair and immune modulation. While tissue repair is related to the differentiation of multipotent MSCs, immune modulation is a particular property of MSCs. Over the last decades, MSCs have been considered as a feasible source of stem cells for tissue regeneration. It hopes to open the new era of stem cell therapy for degenerative diseases. However, the immune modulation capacity of MSCs has been the subject of recent interest over the past several years. The first MSC drug, Prochymal produced by Osiris Therapeutics, was approved in 2012 and is used for immune modulation in graft-versus-host disease (GVHD) treatment (Fig. 2.2).

Fig. 2.2
figure 2

Some mechanisms of MSCs in therapeutic application. MSCs are multipotent stem cells; therefore, they can differentiate into some specific cells that can replace some injured cells/damaged adult cells. In another strategy, MSCs can modulate the immune response via some cytokines

Full size image

2.2.1 Tissue Regeneration

MSCs were shown to have differentiation potential into mesenchymal cells as well as endoderm and ectoderm cells. Based on this capacity, MSCs were considered as a suitable cell source for tissue regeneration from the bone, cartilage, adipose tissue, heart, muscle, and skin. Using in vitro assays, MSCs have been successfully differentiated into osteoblasts (Castren et al. 2015; Glueck et al. 2015; Wang et al. 2015), chondroblasts (Ibrahim et al. 2015; Moghadam et al. 2014; Pustlauk et al. 2015), adipocytes (Li et al. 2015b; Mohammadi et al. 2015), neurons (Bagher et al. 2015; Kim et al. 2015; Nan et al. 2015), insulin-producing cells (Allahverdi et al. 2015; Balici et al. 2016; Ngoc et al. 2011; Van Pham et al. 2014), skeletal muscle (Xu et al. 2015), endothelial progenitor cells (Ikhapoh et al. 2015), cardiac progenitor cells (Li et al. 2015a; Pham et al. 2014; Yang et al. 2015c), and hepatocytes (Han et al. 2015; Sawitza et al. 2015; Ye et al. 2015).

Animal models showed that transplanted MSCs could differentiate in vivo into functional cells at injected sites and contribute to recovering tissue functions. In the minipig model with injured cartilage, Ha et al. (2015) showed that injected human umbilical cord blood-derived MSCs (UC-MSCs) could differentiate and regenerate the cartilage (Ha et al. 2015). Similarly, MSCs can also successfully differentiate into functional insulin-producing cells in vivo in diabetic mice (Yang et al. 2015b), hepatic cells (Hu and Li 2015; Zhong et al. 2015), and neurons (Taran et al. 2014). In animal models, MSCs from the bone marrow, umbilical cord blood, umbilical cord, and peripheral blood have been successfully used to treat several diseases, s uch as injured cartilage (Punwar and Khan 2011; Song et al. 2014), osteoarthritis (Ozeki et al. 2015; Wolfstadt et al. 2015; Xia et al. 2015), myocardial infarction (MI) (Chen et al. 2015), cornea damage (Guo et al. 2006; Ma et al. 2006), wound healing (Li et al. 2015d; Pelizzo et al. 2015), brain and spinal cord injury (Mannoji et al. 2014; Wu et al. 2015), lung failure (Liu et al. 2014a; Matthay et al. 2010), liver cirrhosis (Tang et al. 2015; Yang et al. 2015a), bone healing (Dehghan et al. 2015; Li et al. 2015c), and diabetes mellitus (DM) (Hao et al. 2013; Kong et al. 2014; Lian et al. 2014; Yaochite et al. 2015).

Based on these studies, MSCs have been clinically applied in disease treatment, especially for tissue injury and degenerative medicine. One popular application of MSCs in degenerative disease is in osteoarthritis as well as injured cartilage. Bornes et al. (2014) showed that MSC transplantation shows positive functional outcomes at 12–48 months postimplantation (Bornes et al. 2014). The first reported use of MSCs to repair cartilage damage in humans was conducted by Wakitani et al. in 1998 (Wakitani et al. 2004). To date, approximately 15 publications have reported the application of MSCs in cartilage regeneration (Bornes et al. 2014). The first MSC-based product (allogeneic umbilical cord blood MSC or CARTISTEM) was approved to treat injured cartilage in Korea in 2014. MSCs have also been clinically used in the treatment of wound healing (Falanga et al. 2007; Rasulov et al. 2005; Ravari et al. 2011; Vojtassak et al. 2006).

2.2.2 Immune Modulation

In comparison to other stem cells, MSCs exhibit a powerful capacity of regulating immune responses. Many studies showed that MSCs could regulate immune responses both in vitro and in vivo. The effects of MSCs on immune cells are summarized in Tables 2.2 and 2.3. MSCs can affect all kinds of immune cells including T lymphocytes (Aggarwal and Pittenger 2005; Di Nicola et al. 2002; English et al. 2009), B lymphocytes (Asari et al. 2009; Augello et al. 2005; Corcione et al. 2006), natural killer cells (Sotiropoulou et al. 2006; Spaggiari et al. 2006), and dendritic cells (DCs) (Chen et al. 2007; Zhang et al. 2004). MSCs have thus been successfully applied in both preclinical and clinical treatments for some immune disorder-related diseases. For example, MSCs have been used to treat GVHD in patients transplanted with hematopoietic stem cells (Introna and Rambaldi 2015; von Dalowski et al. 2016; Zhao et al. 2015a), systemic lupus erythematosus (Gu et al. 2014; Wang et al. 2014a; Yan et al. 2013), Crohn’s disease (Ciccocioppo et al. 2015; Liew et al. 2014), multiple system atrophy (Lee et al. 2012; Sunwoo et al. 2014), multiple sclerosis (Dulamea 2015; Gharibi et al. 2015), and amyotrophic lateral sclerosis (Hajivalili et al. 2016; Lewis and Suzuki 2014; Rushkevich et al. 2015). An allogeneic MSC-based product was ap proved as drug for GVHD treatment in Canada in 2015 (Prochymal, which is produced by Osiris Therapeutics). This represents the first approved stem cell drug.

Table 2.2 Immunomodulatory effec ts of MSCs on immune cells
Full size table
Table 2.3 Important bioactive m olecules secreted by MSCs and their functions
Full size table

2.3 Clinical Applications of MSCs

2.3.1 Approved MSC-Based Products

For the past 5 years, MSCs have been widely used in clinical applications mainly through two main approaches: approved MSC-based products and clinical trials. To date, approximately nine MSC-based products have been approved by several countries for the treatment of different diseases such as degenerative arthritis, post-acute MI, and GVHD (Table 2.4, Fig. 2.3). These products have been used in autologous and allogenous transplantation in several countries and have significantly contributed to the growth of MSC clinical applications.

Table 2.4 Allogeneic mesenchymal stem cell-based products approved by several countries
Full size table
Fig. 2.3
figure 3

Some approved MSC-based products in some countries. (a) CARTISTEM; (b) Trinity Evolution; (c) Osteocel; (d) Prochymal

Full size image

CARTISTEM® , a combination of human UC-MSCs and sodium hyaluronate, is intended to be used as a single-dose therapeutic agent for cartilage regeneration in humans with cartilage defects of the knee as a result of aging, trauma, or degenerative diseases.

CardioRel® is an au tologous product designed for early or planned intervention in patients of MI providing mononuclear and mesenchymal stem cells for cardiac regeneration.

Trinity® Evolution™ is an al lograft of cancellous bone containing viable adult stem cells and osteoprogenitor cells within the matrix and a demineralized bone component. Trinity Evolution offers an ideal alternative to autograft and other bone grafting options (without their drawbacks).

Osteocel® Plus is an allograft cellular bone matrix that retains its native bone-forming cells, including MSCs and osteoprogenitors. Osteocel® Plus is intended for the repair, replacement, and reconstruction of skeletal defects.

Hearticellgram®-AMI are bone marrow-derived MSCs (BM-MSCs) used to treat acute MI through intracoronary injection. This study assessed the safety and efficacy of i ntracoronary autologous transplantation of BM-MSCs in patients with acute MI. There were no adverse reactions or major cardiac events. There was an improvement in left ventricular (LV) ejection fraction, already evident 6 h after treatment, in acute myocardial function patients who underwent percutaneous transluminal coronary angiography within 72 h of chest pain onset.

AlloStem is partially de mineralized allograft bone combined with adipose-derived MSCs (AD-MSCs). Suitable for general bone grafting applications, AlloStem is similar to autograft bone because it provides the three key properties necessary for bone formation: osteoconductive (partially demineralized allograft bone, the foundation for the AlloStem tissue, provides a natural scaffold for new bone formation), osteoinductive (naturally occurring growth factors present in allograft bone have been shown to encourage osteogenic activity), and osteogenic (AlloStem contains adult MSCs that naturally adhere to the bone substrate and may contribute to the formation of new bone).

Prochymal is the first stem cell therapy approved for use in Canada. It is also the first therapy approved in Canada for acute GVHD. It is an allogeneic stem therapy based on MSCs derived from the bone marrow of adult donors. MSCs are purified from the marrow and cultured and packaged, with up to 10,000 doses derived from a single donor. The doses are stored frozen until needed.

2.3.2 Clinical Trials of MSC-Based Therapy

In addition to approved MSC-based products, MSCs have been used in disease treatment through clinical trials. According to clinicaltrials.gov, approximately 542 registered clinical trials have used MSCs for treatment. The first clinical trial using in vitro expanded MSCs was performed in 1995, in which 15 patients were treated with autologous stem cells (Lazarus et al. 1995). According to clinicaltrials.gov, almost all of the current trials are in phase I, phase II, or phase I/II, and some of these trials are in phase II or phase II/III (Fig. 2.4, Table 2.5).

Fig. 2.4
figure 4

Clinical trials using mesenchymal stem cells

Full size image
Table 2.5 MSC-based clinical trials in a completed status
Full size table

2.3.2.1 MSCs for Osteoarthritis

MSCs easily differentiate into osteoblasts as well as chondroblasts, and therefore they can be rapidly applied in treating several diseases related to bone and cartilage degeneration. MSCs from various sources have been clinically used in bone and cartilage regeneration (Table 2.6).

Table 2.6 Clinical trials using MSC s for intra-articular injection of cells
Full size table

Autologous MSCs from bone marrow were used in osteoarthritis with good results (Orozco et al. 2013). Autologous in vitro expanded MSCs were also transplanted in cartilage defects (Wong et al. 2013). Allogeneic expanded MSCs from bone marrow were used to treat chronic knee. Vega et al. (2015) showed that allogeneic MSC therapy is simple, without requirement for surgery, and significantly improves cartilage quality (Vega et al. 2015). ADSCs are also used in cartilage regeneration. Autologous ADSCs have been successfully applied in osteoarthritis treatment. Stromal vascular fraction as non-expanded ADSCs was injected to improve knee osteoarthritis for several years (Bui et al. 2014; Koh et al. 2013; Pak 2011). Almost all studies have shown that ADSC transplantation is safe, with no treatment-related adverse events. Intra-articular injection of ADSCs into the osteoarthritic knee improved function and pain of the knee joint and reduced cartilage defects by regeneration of hyaline-like articular cartilage (Jo et al. 2014). Intra-articular autologous activated p eripheral blood stem cells also improved quality of life and regenerated articular cartilage in early osteoarthritic knee disease (Saw et al. 2011, 2013; Turajane et al. 2013).

2.3.2.2 Cardiovascular Diseases

Today, more than 40 clinical trials are l isted with a majority of bone marrow, Wharton’s jelly, and adipose stem cells (Chen et al. 2004; Gee et al. 2010; Hare et al. 2009; Trachtenberg et al. 2011). Both autologous and allogeneic MSCs have been used to treat MI. In 2012, Hare et al. (2012) compared allogeneic vs. autologous BM-MSCs delivered by transendocardial injection in patients with ischemic cardiomyopathy. The authors showed that there was no difference between allogeneic and autologous BM-MSC injection, and MSC injection favorably affected patient functional capacity, quality of life, and ventricular remodeling (Hare et al. 2012). Efficiency of MSCs or mononuclear cells (MNCs) derived from bone marrow was also compared in a recent study (Heldman et al. 2014). Although both MSCs and MNCs from bone marrow were safe by transendocardial injection in ischemic cardiomyopathy patients, improvements such as the 6-min walk distance score, infarct size as a percentage of LV mass, and regional myocardial function as peak Eulerian circumferential strain at the site of injection were only improved in MSC-injected patients (Heldman et al. 2014). Gao et al. (2015) intracoronary infused Wharton’s jelly-derived MSCs (WJMSCs) to treat acute MI. After 18 months of follow-up, the absolute decreases in LV end-systolic volumes and end-diastolic volumes at 18 months in the WJMSC group were significantly greater than those in the placebo group (Gao et al. 2015). In another randomized placebo-controlled clinical trial, Musialek et al. (2015) showed that allogeneic transplantation of WJMSCs is safe and effective in MI patients (Musialek et al. 2015). However, the efficiency of treatment based on MSCs differs based on the age of patients. By transendocardial injection of expanded MSCs, Golpanian et al. (2015) showed that MSC injection improved the 6-min walk distance and quality of life using the Minnesota Living with Heart Failure Questionnaire score and reduces MI size in younger patients (younger than 60 years old); in older patients, these scores were not improved (Golpanian et al. 2015).

Other diseases related to cardiovascular diseases, especially hind limb ischemia, were studied for treatment with MSC injection. ADSCs were collected and expanded ex vivo to treat non-revascularizable critical limb ischemia (Bura et al. 2014). ADSCs were intramuscularly injected into the ischemic leg of patients; no complications were observed, transcutaneous oxygen pressure tended to increase in most patients, and ulcer evolution and wound healing were improved (Bura et al. 2014). Allogeneic MSCs also can improve critical limb ischemia (Gupta et al. 2013). However, different than MSCs, BM-MNCs injection was insufficient to treat critical lower limb ischemia (Moazzami et al. 2014).

2.3.2.3 MSCs for Chronic Inflammatory and Autoimmune Diseases

MSCs have a strong capacity of immune modulation that affects all kinds of immune cells. Several clinical studies have examined MSCs in refractory and severe systemic lupus erythematosus treatment. Some results showed that MSC transplantation resulted in the induction of clinical remission and improvements in serological markers of organ dysfunction (Liang et al. 2010; Sun et al. 2009; Wang et al. 2013a). MSCs have also been used in treatment of Crohn’s disease, which is a chronic inflammatory disorder of the gastrointestinal tract. Crohn’s disease is currently treated by steroids, immunosuppressive agents, or anti-TNF therapy; however, the efficiency of these therapies is low. MSCs from various sources, such as the bone marrow, adipose tissue, and umbilical cord of both autologous and allogeneic forms, were tested to treat Crohn’s disease. Autologous BM-MSCs were safe and beneficial in refractory fistulizing Crohn’s disease (Ciccocioppo et al. 2011; Duijvestein et al. 2010). Molendijk et al. (2015) showed that local administration of allogeneic BM-MSCs was not associated with severe adverse events in patients with perianal fistulizing Crohn’s disease and promoted healing of perianal fistulas (Molendijk et al. 2015). These results were consistent with the study by Forbes et al., in which administration of allogeneic MSCs reduced CDAI and CDEIS scores in patients (Forbes et al. 2014).

2.3.2.4 MSCs for Liver, Lung, and Kidney Disease

The numbers of MSC-based treatments for liver, lung, and kidney diseases have increased over the past several years. The lungs are susceptible to edema and endothelial permeability caused by traumatic injury and represent good targets for MSC-based cell therapy. Three kinds of pulmonary diseases are clinically treated by MSCs, including idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD) , and severe acute respiratory distress syndrome (ARDS). Recent clinical trials have clearly assessed the safety and feasibility of MSCs for the treatment of IPF patients. Both MSCs from the placenta (Chambers et al. 2014) and adipose tissue (Tzouvelekis et al. 2013) were used to treat IPF. The first clinical study of MSC transplantation for COPD was performed in 2013 (Weiss et al. 2013). In this report, Weiss et al. (2013) used in vitro expanded allogeneic MSCs from bone marrow with good results, showing a significant decrease in levels of circulating C-reactive protein in patients treated with MSCs (Weiss et al. 2013). Both BM-MSCs and AD-MSCs were transplanted into ARDS patients. While the clinical results showed that this is a safe method, the disease did not significantly improve after treatment (Simonson et al. 2015; Zheng et al. 2014).

MSC transplantation also shows grea t promise for the treatment of impaired livers, especially advanced fibrosis. Several clinical studies have examined liver fibrosis treatment by MSC transplantation. Almost all these clinical studies (over ten studies) used BM-MSCs, while four studies used allogeneic MSCs, with three studies using UC-MSCs and one study using BM-MSCs (Shi et al. 2012; Wang et al. 2014b, 2013b; Zhang et al. 2012). Interestingly, allogeneic MSC infusion is clinically safe, without side effects, and improved liver function. Zhang et al. examined the safety and efficacy of UC-MSCs in patients affected by liver cirrhosis. The results showed significantly improved liver function in transplanted patients without side effects or complications (Zhang et al. 2012). UC-MSCs were also used to treat acute chronic liver failure patients. The results showed that UC-MSC transfusions significantly increased the survival rates in acute chronic liver failure patients (Shi et al. 2012). In summary, these data demonstrated that MSC transfusions are safe and may serve as a novel therapeutic appro ach for liver diseases.

MSC transplantation is also considered as a promising therapy for kidney failure based on several results in animal models. To date, three phase I/II clinical trials have examined the use of MSCs for kidney failure treatment (Gaspari et al. 2010; Gooch et al. 2008; Togel and Westenfelder 2010). Some initial results showed that MSC infusion could prevent and treat acute renal failure patients (Togel and Westenfelder 2010). Preliminary data indicate that MSC infusion is safe and feasible and that it reduced the length of hospital stay and readmission rates by 40 % (Gooch et al. 2008; Togel and Westenfelder 2010). Gooch et al. indicated that the infusion of allogeneic MSCs seemed to prevent all complications in patients with post-cardiopulmonary bypass-induced acute kidney injury and p romote kidney recovery (Gooch et al. 2008).

2.3.2.5 Diabetes Mellitus (DM)

Several clinical trials have examined the application of MSCs in T1DM patients. The first clinical trial was performed by Haller et al. (2008) to assess the safety and efficacy of using MSC-containing autologous cord blood infusion for DM in children (Haller et al. 2008). This study suggested that cord blood infusion was feasible and safe; there was an increase of peripheral regulatory T-cell level and reduced insulin requirement 6 months after cord blood infusion (Haller et al. 2008). Nevertheless, after 2 years, the therapeutic effect disappeared (Haller et al. 2011).

In another study, Hu et al. evaluated the long-term effects of injecting WJMSCs for new-onset T1DM patients (Hu et al. 2013). Treated T1DM patients had better glycemic control and increased C-peptide levels after 2 years of follow-up (Hu et al. 2013). Ten other clinical trials using MSCs for DM were registered in clinicaltrials.gov. In addition to autologous MSCs, some clinical trials used allogeneic and expanded MSCs for treatment. Prochymal was also evaluated for DM treatment. Some improvements were recorded in treated patients such as glycemic control in newly diagnosed T1DM patients (NCT00690066). Four kinds of MSCs have been used in the clinic, including MSCs from the umbilical cord blood, umbilical cord, adipose tissue, and bone marrow.

MSCs have also been used to treat T2DM. Although, the mechanism of MSCs in T2DM treatment is not yet clear, some clinical trials showed that MSC transplantation is promising. Kong et al. (2014) showed that UC-MSC transfusion was safe and well tolerated, effectively alleviated blood glucose, and increased the generation of C-peptide levels and Tregs in a subgroup of T2DM patients (Kong et al. 2014). This result was similar to another study (Liu et al. 2014b). Placenta-derived MSCs also showed huge potential for T2DM treatment. Transplanted T2DM patients had no fever, chills, liver damage, or other side effects. More importantly, renal function and cardiac function were improved after infusion (Jiang et al. 2011).

2.3.2.6 MSCs in Acute Brain Injury: Stroke

In recent years, clinical trials usin g MSC in stroke have increased dramatically. Since 2009, th ere were 22 clinical trials in phase I/II (Bang et al. 2005; De Keyser 2005; Smith and Gavins 2012). Bang et al. performed the first phase I study to assess safety of intravenous administration of 108 autologous MSCs in patients with severe neurological deficits due to subacute ischemic stroke. The results showed that intravenous cell infusion appeared safe and feasible. In 2010, Lee et al. transplanted MSCs in 16 patients with stroke. Some neurological recovery scores were improved in the MSC group compared with the placebo group (Lee et al. 2010). Both autologous and allogeneic MSCs have been used to treat stroke. All clinical studies showed that MSC transplantation for stroke is safe, with improvement of functional recovery such as neurological scores and size of infarct. These results suggest the potential therapeutic use for MSC in s troke management .

2.4 Safety of MSCs in Clinical Applications

Although the number of c linical applications of MSCs has increased over recent years, the safety of MSCs is still a focus for scientists and medical doctors. The highest risk for MSC transplantation is tumorigenesis in vivo after transplantation. Some hypothesis demonstrated tumorigenesis related to MSC characteristics and some modifications in MSCs during the in vitro expansion. Some studies showed that MSCs without in vitro expansion were safe in both preclinical and clinical applications. For this reason, in 2014, the FDA clarified minimal manipulation of cell/tissue products to be used in the clinic.

In regard to in vitro expanded MSC transplantation, some concerns about the genetic alterations of expanded MSCs were addressed with recent in vitro studies as well as several clinical trials using expanded MSCs. In vitro assays showed that three commonly used MSC types, including BM-MSCs, ADSCs, and UC-MSCs, maintained phenotype and genotype after extended culture. For example, Bernardo et al. showed that BM-MSCs can be cultured long-term in vitro without losing their morphologic, phenotypical, and functional characteristics. These cells can maintain normal karyotype after 44 weeks of culture (Bernardo et al. 2007). ADSCs also did not bypass senescence after 2 months of culture, with no evidence of transformation in vitro (Meza-Zepeda et al. 2008). Chen et al. reported that human UC-MSCs maintained their biological characteristics and function after long-term in vitro culturing and were not susceptible to malignant transformation (Chen et al. 2014). In this study, MSCs could be expanded up to the 25th passage without chromosomal changes by G-band (Chen et al. 2014).

The key obstacle of stem cell therapy is related to whether stem cells may undergo malignant transformation. Some previous studies have described spontaneous transformation of MSCs in vitro (Pan et al. 2014; Ren et al. 2011). However, almost all of these studies have been retracted owing to cross-contamination with cancer cells (de la Fuente et al. 2010; Garcia et al. 2010; Rubio et al. 2005; Torsvik et al. 2010). Roemeling-van Rhijn et al. (2013) showed that ADSCs can form aneuploid cells during in vitro culture. However, they also confirmed that aneuploidy was not a predecessor of transfo rmation or tumor formation (Roemeling-van Rhijn et al. 2013). In preclinical trials, all studies on NOD mice, NOD/SCID mice, guinea pigs, rabbits, and monkey models showed that upon the use of UC-MSCs from the master MSC bank (passage 2, P2) and culturing for an additional five passages (P7) or 11 passages (P13) with a dose of 1 × 107/mouse or 2.106 or 1.107 cells/kg body weight for monkeys, no tumor formation was observed after 2 months (Wang et al. 2012a, b).

Based on these results, in vitro or ex vivo expanded MSCs were accepted for use in clinical trials in various diseases (Table 2.7). Almost all trials were in phase II, and some were in phase II. All trials showed that expanded MSC transplantation was safe and exhibited good effects for disease improvement. Using both methods of delivery of MSCs, including intravenous infusion and local injection, MSC transplantation was shown to be safe. Performed a meta-analysis of clinical trials examining the safety of MSC transplantation, and the results confirmed the safety of MSC transplantation. A total of 2347 citations and 36 studies were reviewed, which included a total of 1012 participants with diseases such as ischemic stroke, Crohn’s disease, cardiomyopathy, MI, GVHD, and healthy volunteers. The authors showed that there was no association between acute infusional toxicity, org an system complications, infection, death, and malignancy. These authors also showed that there was no difference in safety between autologous MSC and allogeneic MSCs, between matched allogeneic MSCs and unmatched allogeneic MSCs, between non-expanded MSCs and in vitro expanded MSCs, and between fresh MSCs and cryopreserved MSCs. However, there was a significant association between MSC tr ansplantation and transient fever.

Table 2.7 List of completed clinical trials us ing ex vivo expanded MSCs
Full size table

2.5 Conclusions

MSCs have become the most frequently applied stem cell type in the clinic. To date, multiple degenerative diseases and several immune-related diseases have been clinically treated by MSC transplantation. Several sources of MSCs include MSCs from the bone marrow, adipose tissue, umbilical cord blood, umbilical cord, and placenta, both with and without in vitro expansion. With useful characteristics about immune modulation, MSCs not only autologously injected into patients but allogeneic graft also was used. After over 10 years of MSC-based treatments, all reports have shown that MSC transplantation is safe. Many reports demonstrate some improvements in disease treatment using MSCs, and several MSC-based products have been approved as stem cell drugs for diseases such as GVHD and osteoarthritis. Together this demonstrates that MSC transplantation is a safe and promising therapy for disease treatment.