Enhancing survival, engraftment, and osteogenic potential of mesenchymal stem cells

Mesenchymal stem cells(MSCs)are promising candidates for bone regeneration therapies due to their plasticity and easiness of sourcing.MSC-based treatments are generally considered a safe procedure,however,the long-term results obtained up to now are far from satisfactory.The main causes of these therapeutic limitations are inefficient homing,engraftment,and osteogenic differentiation.Many studies have proposed modifications to improve MSC engraftment and osteogenic differentiation of the transplanted cells.Several strategies are aimed to improve cell resistance to the hostile microenvironment found in the recipient tissue and increase cell survival after transplantation.These strategies could range from a simple modification of the culture conditions,known as cell-preconditioning,to the genetic modification of the cells to avoid cellular senescence.Many efforts have also been done in order to enhance the osteogenic potential of the transplanted cells and induce bone formation,mainly by the use of bioactive or biomimetic scaffolds,although alternative approaches will also be discussed.This review aims to summarize several of the most recent approaches,providing an up-to-date view of the main developments in MSCbased regenerative techniques.

How mesenchymal stem cell cotransplantation with hematopoietic stem cells can improve engraftment in animal models

BACKGROUND Bone marrow transplantation(BMT)can be applied to both hematopoietic and nonhematopoietic diseases;nonetheless,it still comes with a number of challenges and limitations that contribute to treatment failure.Bearing this in mind,a possible way to increase the success rate of BMT would be cotransplantation of mesenchymal stem cells(MSCs)and hematopoietic stem cells(HSCs)to improve the bone marrow niche and secrete molecules that enhance the hematopoietic engraftment.AIM To analyze HSC and MSC characteristics and their interactions through cotransplantation in murine models.METHODS We searched for original articles indexed in PubMed and Scopus during the last decade that used HSC and MSC cotransplantation and in vivo BMT in animal models while evaluating cell engraftment.We excluded in vitro studies or studies that involved graft versus host disease or other hematological diseases and publications in languages other than English.In PubMed,we initially identified 555 articles and after selection,only 12 were chosen.In Scopus,2010 were identified,and six were left after the screening and eligibility process.RESULTS Of the 2565 articles found in the databases,only 18 original studies met the eligibility criteria.HSC distribution by source showed similar ratios,with human umbilical cord blood or animal bone marrow being administered mainly with a dose of 1×10^(7) cells by intravenous or intrabone routes.However,MSCs had a high prevalence of human donors with a variety of sources(umbilical cord blood,bone marrow,tonsil,adipose tissue or fetal lung),using a lower dose,mainly 106 cells and ranging 104 to 1.5×107 cells,utilizing the same routes.MSCs were characterized prior to administration in almost every experiment.The recipient used was mostly immunodeficient mice submitted to low-dose irradiation or chemotherapy.The main technique of engraftment for HSC and MSC cotransplantation evaluation was chimerism,followed by hematopoietic reconstitution and survival analysis.Besides the engraftment,homing and cellularity were also evaluated in some studies.CONCLUSION The preclinical findings validate the potential of MSCs to enable HSC engraftment in vivo in both xenogeneic and allogeneic hematopoietic cell transplantation animal models,in the absence of toxicity.

Manipulation of collagen synthesis influences progenitor cell engraftment and angiomyogenesis

Myocardial infarction(MI)results in loss of cardiomyocytes(CM) in the ischemic area of the heart followed by an inflammatory response and replacement of contractile CM with fibrosis.Myocardial fibrosis,a key contributor to cardiac dysfunction after MI,presents as a secondary response to the pathophysiological remodeling of long-standing disease including ischemia,obstruction,and microvascular abnormalities.Cardiac fibroblasts and myofibroblasts are responsible for post-MI remodeling which occurs via regulation of extracellular matrix (ECM),presenting as increased collagenⅠandⅢinto the interstitial and perivascular space.In addition to the pluripotency of stem cells following stem/ progenitor cell transplantation,decreased apoptosis, hypertrophy,and fibrosis in the infarcted heart have been demonstrated.This has made transplantation of progenitor/stem cells a primary research focus in the field of tissue regeneration.Unfortunately,the accumulation of ECM and myofibroblasts in areas of tissue injury presents a barrier that can impair penetration of reparative stem/progenitor cells mobilized from peripheral reservoirs.Therefore,cardiac fibroblast production and degradation of ECM are critical in regulating cardiac remodeling and stem/progenitor cell mobilization.This study used transgenic mice overexpressing adenylyl cyclaseⅥ(AC6) in which collagen synthesis was decreased to determine the role of collagen deposition on the engraftment of iPSC from a tri-cell patch applied to infarcted area after MI.

Plerixafor-based mobilization and mononuclear cell counts in graft increased the risk of engraftment syndrome after autologous hematopoietic stem cell transplantation

Engraftment syndrome(ES)is one of the most common complications in the early phase after autologous hematopoietic stem cell transplantation(ASCT),and we aimed to evaluate the incidence and risk factors for ES patients receiving ASCT in the era of plerixafor-based mobilization.A total of 294 were enrolled,and 16.0%(n=47)experienced ES after ASCT.The main clinical manifestations were fever(100%),diarrhea(78.7%),skin rash(23.4%),and hypoxemia/pulmonary edema(12.8%).Plerixafor-based mobilization was associated with higher counts of CD3^(+)cells,CD4^(+)cells,and CD8^(+)cells in grafts.In univariate analysis of the total cohort,age≥60 years,receiving ASCT at complete remission(CR),higher number of mononuclear cell(MNC),CD3^(+)cell counts,CD4^(+)cells as well as CD8^(+)cells transfused and plerixafor-based mobilization were associated with ES after ASCT.Multivariate analysis showed that age≥60 years(P=0.0014),receiving ASCT at CR(P=0.002),and higher number of MNC transfused(P=0.026)were associated with ES in total cohort.In plasma cell disease subgroup,age≥60 years(P=0.013),plerixafor-based mobilization(P=0.036),and receiving ASCT at CR(P=0.002)were associated with ES.Patients with more risk factors had a higher risk of ES.The 1-year probabilities of relapse,non-relapse mortality,and survival were comparable between patients with and without ES.Thus,plerixafor-based mobilization may influence the composition of T lymphocytes in grafts and increase the risk of ES,particularly in patients with plasma cell disease.

Long-term engraftment of p18^(INK4C)-deficient hematopoietic stem cells is enhanced in the sublethally-irradiated recipients

Non-myeloablative regimens for host conditioning have been widely used in clinical hematopoietic stem cell transplantation due to their reduced toxicity on the recipients. But a milder conditioning regimen may require a higher engrafting ability of donor stem cells in competing with endogenous stem cells. Thus, new strategies for enhancing the competitiveness of donor stem cells in non-myeloablative recipients would have important implications for current clinical stem cell trans- plantation. It is known that the absence of p18INK4C (p18) gene can enhance the self-renewal potential of hematopoietic stem cells (HSCs). We applied the approach of competitive bone marrow trans- plantation to evaluate the impact of p18 gene deletion on long-term engraftment of HSCs in sub- lethally irradiated hosts. We found that p18?/? HSCs had a significant advantage over wild-type HSCs during long-term engraftment in the mouse recipients that received a sub-lethal irradiation (5-Gy). The engraftment efficiency of p18?/? HSCs in the sub-lethally irradiated recipients was similar to that in the lethally irradiated (10-Gy) recipients. Our current study demonstrates that enhanced engraftment of donor HSCs in the absence of p18 does not strictly depend on the dose of irradiation used for host conditioning. Therefore, p18 might serve as a potential drug target for increasing the efficacy of stem cell transplant in the patients that are preconditioned with either a myeloablative or non-myeloablative regimen.

Cell-based therapeutic strategies for treatment of spinocerebellar ataxias:an update

Spinocerebellar ataxias are heritable neurodegenerative diseases caused by a cytosine-adenine-guanine expansion,which encodes a long glutamine tract(polyglutamine)in the respective wild-type protein causing misfolding and protein aggregation.Clinical features of polyglutamine spinocerebellar ataxias include neuronal aggregation,mitochondrial dysfunction,decreased proteasomal activity,and autophagy impairment.Mutant polyglutamine protein aggregates accumulate within neurons and cause neural dysfunction and death in specific regions of the central nervous system.Spinocerebellar ataxias are mostly characterized by progressive ataxia,speech and swallowing problems,loss of coordination and gait deficits.Over the past decade,efforts have been made to ameliorate disease symptoms in patients,yet no cure is available.Previous studies have been proposing the use of stem cells as promising tools for central nervous system tissue regeneration.So far,pre-clinical trials have shown improvement in various models of neurodegenerative diseases following stem cell transplantation,including animal models of spinocerebellar ataxia types 1,2,and 3.However,contrasting results can be found in the literature,depending on the animal model,cell type,and route of administration used.Nonetheless,clinical trials using cellular implants into degenerated brain regions have already been applied,with the expectation that these cells would be able to differentiate into the specific neuronal subtypes and re-populate these regions,reconstructing the affected neural network.Meanwhile,the question of how feasible it is to continue such treatments remains unanswered,with long-lasting effects being still unknown.To establish the value of these advanced therapeutic tools,it is important to predict the actions of the transplanted cells as well as to understand which cell type can induce the best outcomes for each disease.Further studies are needed to determine the best route of administration,without neglecting the possible risks of repetitive transplantation that these approaches so far appear to demand.Despite the challenges ahead of us,cell-transplantation therapies are reported to have transient but beneficial outcomes in spinocerebellar ataxias,which encourages efforts towards their improvement in the future.

Impact of conditioning regimen on peripheral blood hematopoietic cell transplant

AIM To investigate infused hematopoietic cell doses and their interaction with conditioning regimen intensity +/-total body irradiation(TBI) on outcomes after peripheral blood hematopoietic cell transplant(PBHCT).METHODS Our retrospective cohort included 247 patients receiving a first, T-replete, human leukocyte antigen-matched allogeneic PBHCT and treated between 2001 and2012. Correlations were calculated using the Pearson product-moment correlation coefficient. Overall survival and progression free survival curves were generated using the Kaplan-Meier method and compared using the log-rank test.RESULTS Neutrophil engraftment was significantly faster after reduced intensity TBI based conditioning [reduced intensity conditioning(RIC) + TBI] and > 4 × 10~6 CD34+cells/kg infused. A higher total nucleated cell dose led to a higher incidence of grade II-IV acute graft-versus-host disease in the myeloablative + TBI regimen group(P = 0.03), but no significant difference in grade III-IV graft-versus-host disease. A higher total nucleated cell dose was also associated with increased incidence of moderate/severe chronic graft-versus-host disease, regardless ofconditioning regimen. Overall and progression-free survival were significantly better in patients with a RIC + TBI regimen and total nucleated cell dose > 8 ×10~8/kg(3 years, overall survival: 70% vs 38%, P = 0.02, 3 years, progression free survival: 64% vs 38%, P = 0.02).CONCLUSION TBI and conditioning intensity may alter the relationship between infused cell doses and outcomes after PBHCT. Immune cell subsets may predict improved survival after unmanipulated PBHCT.

Identification of a Native Novel Oncolytic Immunoglobulin on Exfoliated Colon Epithelial Cells: A Bispecific Heterodimeric Chimera of IgA/IgG*

Understanding the nature of cell surface markers on exfoliated colonic cells is a crucial step in establishing criteria for a normally functioning mucosa. We have found that colonic cells isolated from stool samples (SCSR-010 Fecal Cell Isolation Kit, NonInvasive Technologies, Elkridge, MD), preserved at room temperature for up to one week, with viability of >85% and low levels of apoptosis (8% - 10%) exhibit two distinct cell size subpopulations, in the 2.5 μM - 5.0 μM and 5.0 μM - 8.0 μM range. In addition to IgA, about 60% of the cells expressed a novel heterodimeric IgA/IgG immunoglobulin that conferred a broad-spectrum cell mediated cytotoxicity against tumor cells. In a cohort of 58 subjects the exclusive absence of this immunoglobulin in two African-Americans was suggestive of a germline deletion. Serial cultures in stem cell medium retained the expression of this heterodimer. Since a majority of the cystic cells expressed the stem cell markers Lgr5 and Musashi-1 we termed these cells as gastrointestinal progenitor stem cells (GIP-C**). CXCR-4, the cytokine co-receptor for HIV was markedly expressed. These cells also expressed CD20, IgA, IgG, CD45, and COX-2. We assume that they originated from mature columnar epithelium by dedifferentiation. Our observations indicate that we have a robust noninvasive method to study mucosal pathophysiology and a direct method to create a database for applications in regenerative medicine.

Impact of T cells on hematopoietic stem and progenitor cell function:Good guys or bad guys?

When hematopoietic stem and progenitor cells(HSPC)are harvested for transplantation, either from the bone marrow or from mobilized blood, the graft contains a significant number of T cells. It is these T cells that are the major drivers of graft-vs-host disease(Gv HD). The risk for Gv HD can simply be reduced by the removal of these T cells from the graft. However, this is not always desirable, as this procedure also decreases the engraftment of the transplanted HSPCs and, if applicable, a graft-vs-tumor effect. This poses an important conundrum in the field: T cells act as a double-edged sword upon allogeneic HSPC transplantation, as they support engraftment of HSPCs and provide anti-tumor activity, but can also cause Gv HD. It has recently been suggested that T cells also enhance the engraftment of autologous HSPCs, thus supporting the notion that T cells and HSPCs have an important functional interaction that is highly beneficial, in particular during transplantation. The underlying reason on why and how T cells contribute to HSPC engraftment is still poorly understood. Therefore, we evaluate in this review the studies that have examined the role of T cells during HSPC transplantation and the possible mechanisms involved in their supporting function. Understanding the underlying cellular and molecular mechanisms can provide new insight into improving HSPC engraftment and thus lower the number of HSPCs required during transplantation. Moreover, it could provide new avenues to limit the development of severe Gv HD, thus making HSPC transplantations more efficient and ultimately safer.

APPLICATION OF TWO-COLOR INTERPHASE FISH USING SEX PROBE IN ALLOGENEIC STEM CELL TRANSPLANTATION

Objective: To evaluate the significance of two-color interphase fluorescence in situ hybridization (FISH) using X and Y centromere probe in the engraftment estimation and minimal residual disease (MRD) monitoring after allogeneic stem cell transplantation (alloSCT). Methods: Samples from 12 cases patients in different periods after alloSCT were detected by interphase FISH. Results: All of the 12 patients were proved to obtain engraftment 22–35 days after alloSCT. While traditional karyotype showed as 100%XX or 100%XY invariably, FISH showed different percentages of donor original sex chromosome. Conclusion: Two-color interphase FISH is a more sensitive and simple test for engraftment evaluation and MRD monitoring post SCT, though, it can not entirely replace traditional karyotype analysis and gene detection by RT-PCR.

Xenogeneic hepatic progenitor cell transplantation ameliorate CCl_4 /partial hepatectomy-induced rat acute liver failure

Objective： Hepatic progenitor cell transplantation has shed light on the treatment of liver failure. The present study was designed to evaluate whether xenogeneic liver epithelial progenitor cells （LEPCs） transplantation could promote liver recovery in a rat model of acute liver failure. The engraftment and hepatocytic differentiation of transplanted hepatic progenitor cells in the rat spleen was also investigated. Methods： LEPCs were propagated in vitro for long and transduced with lentiviral vector carrying mCherry gene. Intraperitoneal injection of CC14 followed by 2/3 partial hepatectomy three days later were used to establish rat models of acute liver failure. Rats were intrasplenically injected with mCherry modified LEPCs （n=20, 1× 107 cells/0.5 mL） or the same volume of medium （n=20）. Serum liver enzymes （ALT, AST） and liver histology were evaluated for 21 days after transplantation. The engraftment of transplanted LEPCs in the spleens was tested by polymerase chain reaction （PCR） amplification targeting mCherry gene. The differentiation into hepatocytic lineage of transplanted LEPCs was investigated usingimmunohistochemistry staining against Alb. Results： LEPCs were effectively transduced with lentiviral vector showing a transduction efficiency of 90%. Compared with control, cell-injected group displayed significantly lower levels of ALT and AST （P〈0.05） and better histological features including less swelling change and hepatocyte death. PCR amplification of mCherry sequences confirmed the engraftment of LEPCs in the spleens. Alb-positive cells first appeared 5 days after cell transplantation and the number of Alb-positive cells increased substantially （P〈0.05）, which revealed the hepatocytic differentiation process Conclusion： Xenogeneic hepatic progenitor cells can engraft and differentiate into hepatocytes in the splenic parenchyma. Intrasplenic delivery of hepatic progenitor cells ameliorates CCh/partial hepatectomy-induced liver injury in rats

Considerations for hematopoietic stem cell transplantation in primary immunodeficiency disorders

Primary immunodeficiency disorders (PIDs) result from inborn errors in immunity.Susceptibility to infections and oftentimes severe autoimmunity pose life-threatening risks to patients with these disorders.Hematopoietic cell transplant (HCT) remains the only curative option for many.Severe combined immunodeficiency disorders (SCID) most commonly present at the time of birth and typically require emergent HCT in the first few weeks of life.HCT poses an unusual challenge for PIDs.Donor source and conditioning regimen often impact the outcome of immune reconstitution after HCT in PIDs.The use of matched or unmatched, as well as related versus unrelated donor has resulted in variable outcomes for different subsets of PIDs.Additionally, there is significant variability in the success of engraftment even for a single patient’s lymphocyte subpopulations.While certain cell lines do well without a conditioning regimen, others will not reconstitute unless conditioning is used.The decision to proceed with a conditioning regimen in an already immunocompromised host is further complicated by the fact that alkylating agents should be avoided in radiosensitive PIDs.This manuscript reviews some of the unique elements of HCT in PIDs and evidence-based approaches to transplant in patients with these rare and challenging disorders.

Engrafted newborn neurons could functionally integrate into the host neuronal network

The limited capability to regenerate new neurons following injuries of the central neural system（CNS）still remains a major challenge for basic and clinical neuroscience.Neural stem cells（NSCs）could nearly have the potential to differentiate into all kinds of neural cells in vitro.

Monitoring the source of mesenchymal stem cells in patients after transplantation of mismatched-sex hematopoietic stem cells plus thirdparty cells

Background In bone marrow transplant patients, the microenvironment in bone marrow is damaged after chemotherapy or radiotherapy. Subsequent to allogenic hematopoietic stem cell transplantation in patients with clinically successful engraftments, the source of mesenchymal stem cells （MSCs） remains controversial. To further verify the stimulatory effect of the simultaneous transplantation of cells from second donors on engraftment success for hematopoietic stem cell transplantation in support of donor MSCs engraftments, the aim of this study is to monitor the dynamics of the engraftment of bone marrow-derived MSCs in patients after transplantation with mismatched-sex hematopoietic stem and third-party cells. Methods In this study, the hematopoietic stem cells from 32 clinical donors of different sexes that resulted in successful engraftments were selected for transplantation and were classified into three groups for research purposes： group A consisted of 14 cases of transplantation with bone marrow and recruited peripheral hematopoietic stem cell transplantation, group B contained 8 cases of simultaneous re-transfusion of MSCs from the second donor, and group C contained 10 cases of simultaneous re-transfusion of umbilical blood from the second donor. The bone marrow from 32 patients with successful engraftments of hematopoietic transplantation were selected and sub-cultured with MSCs. Flow cytometry （FCM） was used to measure the expression of surface antigens on MSCs. Denaturing high-performance liquid chromatography （DHPLC） in combination with polymerase chain reaction amplification of short tandem repeats （STR- PCR） was used to measure the engraftment status of fifth-generation MSCs in patients. Fluorescence in situ hybridization （FISH） revealed the sex origin of the fifth-generation MSCs in 32 patients. Dynamic examinations were performed on patients receiving donor transplantations. Results The progenies of fifth-generation MSCs were successfully cultured in 32 cases. The results of FCM demonstrated that the expression levels of CD14＋ and CD45＋ cells were lower than 0.04% in the fifth-generation MSCs. The analysis using DHPLC and FISH showed similar results. One patient from group B also received a temporary transplantation of MSCs from the donor. The MSCs in the remaining 31 patients all originated from the patients themselves. Conclusions After transplantation, the MSCs present in patients originated from the host. In patients transplanted with MSCs from a second donor, the phenomenon of temporary chimerization of MSCs was observed.

Strategies to improve the migration of mesenchymal stromal cells in cell therapy

Mesenchymal stromal/stem cells(MSCs) are multipotent cells under consideration as a potential new therapy for a variety of inflammatory diseases including certain neurological disorders. It is generally thought that the efficacy of cell therapy in attenuating damage after ischemia, inflammation, or injury depends on the quantity of transplanted cells recruited to the target tissue. However, only a small number of systematically infused MSCs can effectively migrate to target sites, which significantly decreases the efficacy of exogenous cell-based therapy. In this review, we discuss specific factors influencing MSC migration, and summarize current strategies that effectively promote the motility of MSCs. In addition, we describe several protocols to improve the migration of stromal cells into the nervous system and, therefore,enhance the efficiency of engraftment as means of treating neurological disorders.