Allogeneic Adipose-Derived Stem Cells with Low Immunogenicity Constructing Tissue-Engineered Bone for Repairing Bone Defects in Pigs

Subaqueous free-standing 3D cell culture system for ultrafast cell compaction, mechano-inductive immune control, and improving therapeutic angiogenesis

Conventional 3D cell culture methods require a comprehensive complement in labor-intensive and time-consuming processes along with in vivo circumstantial mimicking. Here, we describe a subaqueous free-standing 3D cell culture (FS) device that can induce the omnidirectional environment and generate ultrafast human adipose-derived stem cells (hADSCs) that efficiently aggregate with compaction using acoustic pressure. The cell culture conditions were optimized using the FS device and identified the underlying molecular mechanisms. Unique phenomena in cell aggregation have led to extraordinary cellular behavior that can upregulate cell compaction, mechanosensitive immune control, and therapeutic angiogenesis. Therefore, we designated the resulting cell aggregates as "pressuroid." Notably, external acoustic stimulation produced by the FS device affected the pressuroids. Furthermore, the pressuroids exhibited upregulation in mechanosensitive genes and proteins, PIEZO1/2. CyclinD1 and PCNA, which are strongly associated with cell adhesion and proliferation, were elevated by PIEZO1/2. In addition, we found that pressuroids significantly increase angiogenic paracrine factor secretion, promote cell adhesion molecule expression, and enhance M2 immune modulation of Thp1 cells. Altogether, we have concluded that our pressuroid would suggest a more effective therapy method for future cell therapy than the conventional one.

Engineered Adipose-Derived Stem Cells Overexpressing RXFP1 via CRISPR Activation Ameliorate Erectile Dysfunction in Diabetic Rats

Due to the high incidence of diabetes mellitus (DM) and poor response to the first-line treatment of DM-induced erectile dysfunction (DMED), new therapeutic strategies for DMED are needed. Adipose-derived stem cell (ADSC) transplantation is considered a promising treatment modality for DMED but is limited by poor survival and efficacy after transplantation. In this study, we aimed to increase the therapeutic effect of DMED by overexpressing the relaxin family peptide receptor 1 (RXFP1) using a clustered regularly interspaced short palindromic repeats activation (CRISPRa) system in ADSCs. Two lentiviruses carrying the CRISPRa system transfected ADSCs to overexpress RXFP1 (RXFP1-ADSCs). The intracavernous injection of ADSCs was performed in DMED rats induced by the intraperitoneal injection of streptozotocin. Four weeks after transplantation, we measured erectile function and collected specimens of the corpus cavernosum for follow-up detection. The results showed that ADSCs improved erectile function in diabetic rats, and the RXFP1-ADSCs were more significant. We detected reduced levels of oxidative stress, apoptosis and fibrosis together with relative normalization of endothelial and smooth muscle cell function in the penis after ADSC transplantation. RXFP1-ADSCs had more potent efficacy in the above alterations compared to negative control ADSCs due to the high levels of survival and paracrine capacity in RXFP1-ADSCs. The results revealed that RXFP1-ADSC transplantation could partially preserve erectile function in DMED rats associated with the regulation of oxidative stress, apoptosis, fibrosis and endothelial and smooth muscle cell dysfunction. RXFP1 may be the new target for the genetic modification of ADSCs, which benefits the management of DMED.

Effects of Tissue-engineered Bone by Coculture of Adipose-derived Stem Cells and Vascular Endothelial Cells on Host Immune Status

AIM

The study aimed to explore the effects of tissue-engineered bone constructed with partially deproteinized biologic bone (PDPBB) and coculture of adipose-derived stem cells (ADSCs) and vascular endothelial cells (VECs) on host immune status, providing a very useful clue for the future development of bone engineering.

METHODS

Tissue-engineered bones constructed by PDPBB and ADSCs, VECs or coculture of them were implanted into the muscle bag of bilateral femurs of Sprague-Dawley rats. Partially deproteinized biologic bone alone and blank control were also implanted. After transplantation, the proliferation of implanted seed cells in tissue-engineered bones was labeled by bromodeoxyuridine staining. Moreover, the changes of T-lymphocyte subpopulations, including CD3 + CD4+ and CD3 + CD8+ in peripheral blood were then detected using flow cytometry to analyze the immune rejection of tissue-engineered bone implantation based on peripheral blood CD4/CD8 ratios.

RESULTS

After transplantation, the proliferation of implanted seed cells was observed in tissue-engineered bones of different groups. At different time points after transplantation, the CD4+/CD8+ ratio in peripheral blood of PDPBB + ADSCs, PDPBB + coculture, and blank control groups did not exhibit significant change. Although the CD4+/CD8+ ratio in peripheral blood of PDPBB + VECs group was significantly higher than other group at 1 week after transplantation, that of PDPBB + VECs and PDPBB + coculture group was significantly decreased at 8 week after transplantation compared with that of blank control group.

CONCLUSIONS

Our results indicated that there was no significant immune rejection after transplantation of tissue-engineered bone constructed with PDPBB and coculture of ADSCs and VECs as seed cells.

Xenogeneic mesenchymal stem cell transplantation for mandibular defect regeneration

BACKGROUND

It is commonly accepted that xenogeneic stem cell transplantation for tissue engineering is faced with host immune rejection. Using a rat critical-size mandibular defect model, this study examined whether the immune rejection can be evaded by diminishing T-cell immunity.

METHODS

To examine donor cell survival and host immune reaction, pig bone marrow-derived mesenchymal stem cells (BM-MSCs) were labeled with CM-DiI, loaded onto gelatin sponge (5 × 10⁶ cells/scaffold), and transplanted into 5-mm mandibular defects of immunocompetent and T cell-deficient athymic rats. To examine the effects of xenogeneic BM-MSCs on bone regeneration, athymic rats undergone the same surgeries were terminated at post-operative weeks 1, 3, and 6. Control rats underwent the same jaw surgery without BM-MSC transplantation.

RESULTS

The density of CM-DiI-labeled BM-MSCs decreased with time in both strains of rats. Although it was substantially higher in athymic rats than in immunocompetent rats at post-operative day 1, by day 3-7 the density became comparable between the two strains of rats. Apoptosis reflected by cleaved Caspase-3 staining was low in both strains. Stronger infiltration of neutrophils, macrophages, B cells and CD8⁺ T cells was found in MSC-treated animals. In athymic rats, infiltration of neutrophils and macrophages was strong, but it occurred later than that in immunocompetent rats. While bone volume fraction significantly increased with time (P < .001), no difference was found between MSC-treated and control groups.

CONCLUSIONS

Even in hosts with deficient T-cell immunity, xenogeneic BM-MSC transplantation into mandibular critical-sized defects still faces challenges from host innate immunity, which compromises their regenerative efficacy.

Advances in regenerative therapy: A review of the literature and future directions

There is enormous global anticipation for stem cell-based therapies that are safe and effective. Numerous pre-clinical studies present encouraging results on the therapeutic potential of different cell types including tissue derived stem cells. Emerging evidences in different fields of research suggest several cell types are safe, whereas their therapeutic application and effectiveness remain challenged. Multiple factors that influence treatment outcomes are proposed including immunocompatibility and potency, owing to variations in tissue origin, ex-vivo methodologies for preparation and handling of the cells. This communication gives an overview of literature data on the different types of cells that are potentially promising for regenerative therapy. As a case in point, the recent trends in research and development of the mesenchymal stem cells (MSCs) for cell therapy are considered in detail. MSCs can be isolated from a variety of tissues and organs in the human body including bone marrow, adipose, synovium, and perinatal tissues. However, MSC products from the different tissue sources exhibit unique or varied levels of regenerative abilities. The review finally focuses on adipose tissue-derived MSCs (ASCs), with the unique properties such as easier accessibility and abundance, excellent proliferation and differentiation capacities, low immunogenicity, immunomodulatory and many other trophic properties. The suitability and application of the ASCs, and strategies to improve the innate regenerative capacities of stem cells in general are highlighted among others.

Tissue Engineering and Regenerative Medicine: Achievements, Future, and Sustainability in Asia

Exploring innovative solutions to improve the healthcare of the aging and diseased population continues to be a global challenge. Among a number of strategies toward this goal, tissue engineering and regenerative medicine (TERM) has gradually evolved into a promising approach to meet future needs of patients. TERM has recently received increasing attention in Asia, as evidenced by the markedly increased number of researchers, publications, clinical trials, and translational products. This review aims to give a brief overview of TERM development in Asia over the last decade by highlighting some of the important advances in this field and featuring major achievements of representative research groups. The development of novel biomaterials and enabling technologies, identification of new cell sources, and applications of TERM in various tissues are briefly introduced. Finally, the achievement of TERM in Asia, including important publications, representative discoveries, clinical trials, and examples of commercial products will be introduced. Discussion on current limitations and future directions in this hot topic will also be provided.

Biomaterials-Induced Stem Cells Specific Differentiation Into Intervertebral Disc Lineage Cells

Stem cell therapy, which promotes stem cells differentiation toward specialized cell types, increases the resident population and production of extracellular matrix, and can be used to achieve intervertebral disc (IVD) repair, has drawn great attention for the development of IVD-regenerating materials. Many materials that have been reported in IVD repair have the ability to promote stem cells differentiation. However, due to the limitations of mechanical properties, immunogenicity and uncontrollable deviations in the induction of stem cells differentiation, there are few materials that can currently be translated into clinical applications. In addition to the favorable mechanical properties and biocompatibility of IVD materials, maintaining stem cells activity in the local niche and increasing the ability of stem cells to differentiate into nucleus pulposus (NP) and annulus fibrosus (AF) cells are the basis for promoting the application of IVD-regenerating materials in clinical practice. The purpose of this review is to summarize IVD-regenerating materials that focus on stem cells strategies, analyze the properties of these materials that affect the differentiation of stem cells into IVD-like cells, and then present the limitations of currently used disc materials in the field of stem cell therapy and future research perspectives.

Conditioned Medium from Adipose-Derived Stem Cell Inhibits Jurkat Cell Proliferation through TGF-β1 and p38/MAPK Pathway

Background

Since the first report on the immunomodulatory and immunosuppressive properties of Adipose-Derived Stem Cells (ADSCs), many studies have elucidated the underlying molecular mechanism of their suppressive activity on mixed lymphocyte reaction (MLR). However, a gap exists in our understanding of the molecular mechanism of ADSC-conditioned medium (ADSC-CM) on MLR.

Methods

ADSCs were isolated from Human Adipose Tissues, and Enzyme-linked Immunosorbent Assay (ELISA) was used to identify the concentration of transforming growth factor β1 (TGF-β1) in ADSC-CM. The transcript abundance of TGF-β1, as well as that of insulin-like growth factor binding protein 3 (IGF-BP3), was evaluated using qRT-PCR on Jurkat cells cultured in ADSC-CM for 24 hours. The proliferation of the Jurkat cells was assessed using cell cycle assay. Western blotting was performed to identify potential signaling molecules involved in the ADSC-CM-induced inhibition of Jurkat cell proliferation.

Results

The findings confirm that the isolated ADSCs demonstrate classic ADSC characteristics. The level of TGF-β1 was found to be low in ADSC-CM, as assessed by ELISA. Jurkat cells grown in ADSC-CM show reduced gene expression of TGF-β1 and IGF-BP3 compared with that of the control group. Furthermore, western blotting of ADSC-CM grown Jurkat cells that were blocked at the G0/G1 stage indicates that ADSC-CM decreases the protein expression of pP38 in a dose-dependent manner.

Conclusion

ADSC-CM can inhibit Jurkat cell proliferation through the TGF-β1-p38 signaling pathway.

New bioresorbable wraps based on oxidized polyvinyl alcohol and leukocyte-fibrin-platelet membrane to support peripheral nerve neurorrhaphy: preclinical comparison versus NeuraWrap

Nerve wrapping improves neurorrhaphy outcomes in case of peripheral nerve injuries (PNIs). The aim of this preclinical study was to assess the efficacy of two novel biodegradable wraps made of a synthetic 1% oxidized polyvinyl alcohol (OxPVA) and a natural leukocyte-fibrin-platelet membrane (LFPm) versus the commercial product NeuraWrap. After rats sciatic nerve transection and neurorrhaphy, the wraps were implanted and compared for functional outcome, by sciatic function index assessment; structural characteristics, by histological/immunohistochemical analysis; ultrastructural features, by transmission electron microscopy. Moreover, a morphometric study was also performed and collagen distribution was observed by Second Harmonic Generation microscopy. After 12 weeks from implantation, all wraps assured nerve function recovery; no scar tissue/neuromas were visible at dissection. LFPm wraps were completely resorbed, while residues of OxPVA and NeuraWrap were observed. In all groups, biocompatibility was confirmed by the absence of significant inflammatory infiltrate. According to histological/immunohistochemical analysis and morphometric findings, OxPVA and LFPm wraps were both effective in preserving nerve integrity. These results assess that bioengineered OxPVA and LFPm wraps successfully guarantee favorable lesion recovery after PNI/neurorrhaphy and, in future, may be considered an interesting alternative to the commercial NeuraWrap.

Bioprinting functional tissues

Despite the numerous lives that have been saved since the first successful procedure in 1954, organ transplant has several shortcomings which prevent it from becoming a more comprehensive solution for medical care than it is today. There is a considerable shortage of organ donors, leading to patient death in many cases. In addition, patients require lifelong immunosuppression to prevent graft rejection postoperatively. With such issues in mind, recent research has focused on possible solutions for the lack of access to donor organs and rejections, with the possibility of using the patient's own cells and tissues for treatment showing enormous potential. Three-dimensional (3D) bioprinting is a rapidly emerging technology, which holds great promise for fabrication of functional tissues and organs. Bioprinting offers the means of utilizing a patient's cells to design and fabricate constructs for replacement of diseased tissues and organs. It enables the precise positioning of cells and biologics in an automated and high throughput manner. Several studies have shown the promise of 3D bioprinting. However, many problems must be overcome before the generation of functional tissues with biologically-relevant scale is possible. Specific focus on the functionality of bioprinted tissues is required prior to clinical translation. In this perspective, this paper discusses the challenges of functionalization of bioprinted tissue under eight dimensions: biomimicry, cell density, vascularization, innervation, heterogeneity, engraftment, mechanics, and tissue-specific function, and strives to inform the reader with directions in bioprinting complex and volumetric tissues. STATEMENT OF SIGNIFICANCE: With thousands of patients dying each year waiting for an organ transplant, bioprinted tissues and organs show the potential to eliminate this ever-increasing organ shortage crisis. However, this potential can only be realized by better understanding the functionality of the organ and developing the ability to translate this to the bioprinting methodologies. Considering the rate at which the field is currently expanding, it is reasonable to expect bioprinting to become an integral component of regenerative medicine. For this purpose, this paper discusses several factors that are critical for printing functional tissues including cell density, vascularization, innervation, heterogeneity, engraftment, mechanics, and tissue-specific function, and inform the reader with future directions in bioprinting complex and volumetric tissues.

Perspectives for Clinical Translation of Adipose Stromal/Stem Cells

Adipose stromal/stem cells (ASCs) are an ideal cell type for regenerative medicine applications, as they can easily be harvested from adipose tissue in large quantities. ASCs have excellent proliferation, differentiation, and immunoregulatory capacities that have been demonstrated in numerous studies. Great interest and investment have been placed in efforts to exploit the allogeneic use and immunomodulatory and anti-inflammatory effects of ASCs. However, bridging the gap between in vitro and in vivo studies and moving into clinical practice remain a challenge. For the clinical translation of ASCs, several issues must be considered, including how to characterise such a heterogenic cell population and how to ensure their safety and efficacy. This review explores the different phases of in vitro and preclinical ASC characterisation and describes the development of appropriate potency assays. In addition, good manufacturing practice requirements are discussed, and cell-based medicinal products holding marketing authorisation in the European Union are reviewed. Moreover, the current status of clinical trials applying ASCs and the patent landscape in the field of ASC research are presented. Overall, this review highlights the applicability of ASCs for clinical cell therapies and discusses their potential.

Bone marrow mesenchymal stem cells: Aging and tissue engineering applications to enhance bone healing

Bone has well documented natural healing capacity that normally is sufficient to repair fractures and other common injuries. However, the properties of bone change throughout life, and aging is accompanied by increased incidence of bone diseases and compromised fracture healing capacity, which necessitate effective therapies capable of enhancing bone regeneration. The therapeutic potential of adult mesenchymal stem cells (MSCs) for bone repair has been long proposed and examined. Actions of MSCs may include direct differentiation to become bone cells, attraction and recruitment of other cells, or creation of a regenerative environment via production of trophic growth factors. With systemic aging, MSCs also undergo functional decline, which has been well investigated in a number of recent studies. In this review, we first describe the changes in MSCs during aging and discuss how these alterations can affect bone regeneration. We next review current research findings on bone tissue engineering, which is considered a promising and viable therapeutic solution for structural and functional restoration of bone. In particular, the importance of MSCs and bioscaffolds is highlighted. Finally, potential approaches for the prevention of MSC aging and the rejuvenation of aged MSC are discussed.

Hypoxia-preconditioned MSCs Have Superior Effect in Ameliorating Renal Function on Acute Renal Failure Animal Model

BACKGROUND

Acute renal failure (ARF) is a serious disease characterised by a rapid loss of renal functions due to nephrotoxic drug or ischemic insult. The clinical treatment approach such as dialysis techniques and continuous renal enhancement have grown rapidly during past decades. However, there is yet no significant effect in improving renal function. Hypoxia-preconditioned mesenchymal stem cells (HP-MSCs) have positive effects on the in vitro survival and stemness, in addition to angiogenic potential.

AIM

In this study, we aimed to analyse the effect of HP-MSCs administration in improving renal function, characterised by blood urea nitrogen (BUN) and creatinine level.

METHODS

A group of 15 male Wistar rats weighing 250 g to 300 g were used in this study (n = 5 for each group). Rats were randomly distributed into 3 groups: Vehicle control (Veh) as a control group, HP-MSCs and normoxia MSCs (N-MSCs) as the treatment group. Renal function was evaluated based on the BUN and creatinine levels using the colourimetric method on day 5 and 13. The histological analysis using HE staining was performed on day 13.

RESULTS

The result showed there is a significant decrease in BUN and creatinine level (p < 0.05). The histological analysis of renal tissue also showed a significant decrease between Veh and treatment group (p < 0.05).

CONCLUSION

Based on this study, we conclude that HP-MSCs have a superior beneficial effect than N-MSCs in improving renal function in an animal model of gentamicin-induced ARF.

DMPE-PEG scaffold binding with TGF-β1 receptor enhances cardiomyogenic differentiation of adipose-derived stem cells

Background

Heart failure has become a global health problem with increasing incidences worldwide. Traditional pharmacological treatments can delay but cannot reverse the underlying disease processes. The clinical application of myocardial tissue engineering represents a promising strategy because it features cell-based replacement therapies that replace partially or fully damaged cardiac tissues with in vitro-generated tissue equivalents. However, the effectiveness of this therapy is limited by poor viability and differentiation of the grafted cells. This limitation could be overcome by rapidly increasing the numbers of functional cardiomyocytes. In this study, we aimed to obtain functional myocardial tissue engineering seed cells with high proliferation and differentiation rates by combining 1,2-dimyristoyl-sn-glycero-3-phosphoethan-olamine-polyethylene glycol (DMPE-PEG) and recombinant transforming growth factor-β1 receptor I (rTGF-β1 RI), followed by binding to human adipose-derived stromal cells (hADSCs).

Methods

To induce higher expression level of TGF-β1 RI, DMPE-PEG was inoculated with rTGF-β1 RI to modify the surface of hADSCs. The differentiation ability and morphological characteristics of the modified hADSCs were examined in vitro and in vivo.

Results

The caridiomyocartic differentiation ability of TGF-β1 RI-modified hADSCs was significantly enhanced, as indicated by elevated expression levels of the cardiac markers cardiac troponin T (cTnT) and α-smooth muscle actin (SMA) via increased phosphorylation of the Smad signaling pathway-related proteins.

Conclusion

Our findings provide new insights into stem cell transplantation therapy in myocardial tissue engineering.

Human Bone Marrow Mesenchymal Stromal Cells Promote Bone Regeneration in a Xenogeneic Rabbit Model: A Preclinical Study

Significant research efforts have been undertaken during the last decades to treat musculoskeletal disorders and improve patient's mobility and quality of life. The goal is the return of function as quickly and completely as possible. Cellular therapy has been increasingly employed in this setting. The design of this study was focused on cell-based alternatives. The present study aimed at investigating the bone regeneration capacity of xenogeneic human bone marrow-derived mesenchymal stromal cell (hMSC) implantation with tricalcium phosphate (TCP) granules in an immunocompetent rabbit model of critical-size bone defects at the femoral condyles. Two experimental groups, TCP and hMSC + TCP, were compared. Combination of TCP and hMSC did not affect cell viability or osteogenic differentiation. We also observed significantly higher bone regeneration in vivo in the hMSC + TCP group, which also displayed better TCP osteointegration. Also, evidence of hMSC contribution to a better TCP osteointegration was noticed. Finally, no inflammatory reaction was detected, besides the xenotransplantation of human cells into an immunocompetent recipient. In summary, hMSC combined with TCP granules is a potential combination for bone regeneration purposes that provides better preclinical results compared to TCP alone.

Exogenous stromal derived factor-1 releasing silk scaffold combined with intra-articular injection of progenitor cells promotes bone-ligament-bone regeneration

Anterior cruciate ligament (ACL) is one of the most difficult tissues to heal once injured. Ligament regeneration and tendon-bone junction healing are two major goals of ACL reconstruction. This study aimed to investigate the synergistic therapeutic effects of Stromal cell-derived factor 1 (SDF-1)-releasing collagen-silk (CSF) scaffold combined with intra-articular injection of ligament-derived stem/progenitor cells (LSPCs) for ACL regeneration and the amelioration in the long-term complication of osteoarthritis (OA). The stem cell recruitment ability of CSF scaffold and the multipotency, particularly the tendon forming ability of LSPCs from rabbits were characterized in vitro, while the synergistic effect of the CSF scaffold and LSPCs for ACL regeneration and OA amelioration were investigated in vivo at 1, 3, and 6 months with a rabbit ACL reconstruction model. The CSF scaffold was used as a substitute for the ACL, and LSPCs were injected into the joint cavity after 7 days of the ACL reconstruction. CSF scaffold displayed a controlled release pattern for the encapsulated protein for up to 7 days with an increased stiffness in the mechanical property. LSPCs, which exhibited highly I Collagen and CXCR4 expression, were attracted by SDF-1 and successfully relocated into the CSF scaffold at 1 month in vivo. At 3 and 6 months post-treatment, the CSF scaffold combined with LSPCs (CSFL group) enhanced the regeneration of ACL tissue, and promoted bone tunnel healing. Furthermore, the OA progression was impeded efficiently. Our findings here provided a new strategy that using stem cell recruiting CSF scaffold with tissue-specific stem cells, could be a promising solution for ACL regeneration.

STATEMENT OF SIGNIFICANCE

In this study, we developed a silk scaffold with increased stiffness and SDF-1 controlled release capacity for ligament repair. This advanced scaffold transplantation combined with intra-articular injection of LSPCs (which was isolated from rabbit ligament for the first time in this study) promoted the regeneration of both the tendinous and bone tunnel portion of ACL. This therapeutic strategy also ameliorated cartilage degeneration and reduced the severity of arthrofibrosis. Hence, combining LSPCs injection with SDF-1-releasing silk scaffold is demonstrated as a therapeutic strategy for ACL regeneration and OA treatment in the clinic.

Repair of bone defects in rat radii with a composite of allogeneic adipose-derived stem cells and heterogeneous deproteinized bone

Background

In the bone tissue engineering domain, seed cells, scaffold and cell-scaffold composites are three focuses. In this study, the feasibility of using allogeneic adipose-derived stem cells(ADSCs) combined with heterogeneous deproteinized bone (HDB) to repair segmental radial defects was investigated by observing the repair of the defect area.

Methods

ADSCs were cultured in vitro, purified, antigen-detected and osteogenic differentiation potency-measured; then, the ADSCs of the third generation were seeded into HDB to prepare an ADSCs-HDB composite partly with osteogenesis induced cells. Sixty Wistar rats were randomly divided into four groups with 15 in each group. A bone defect (4 mm in length) was created at the left radius in each rat. Two kinds of ADSCs-HDB composites were implanted in the ADSCs osteogenesis group or ADSCs group; HDB was implanted in the negative control group; nothing was filled in the blank control group. The bone defect repair was evaluated by gross observation, molybdenum target X-ray examination and histological analyses after surgery.

Results

Gross observation: the bone defect area was completely filled and difficult to recognize in the ADSCs osteogenesis group. The connection of the ADSCs group was strong, but the implants were clearly identifiable. The joints of the negative control group were slightly thick but the connection was unstable. In the blank control group, kermesinus tissue was between the two ends and bones were not connected after 8 weeks. Molybdenum target X-ray examinations: In the ADSCs osteogenesis group, evident bridges in the graft were observed in the defects in the fourth week; the defects were filled with new bone completely and a marrow cavity appeared at 8 weeks. In the ADSCs group, there were some callus formations, but the radial defect was still obvious at 8 weeks. In the negative control group, fracture lines were clear. In the blank control group, no osseous bridges were observed, which resulted in bone nonunion eventually in 8 weeks. There were significant differences in the callus density between experimental groups and the blank control group at 4 and 8 weeks (P < 0.01). Histological measures showed that the rate and quality of the new bone formation and remodelling was significantly different between the experimental and control groups.

Conclusions

A composite of ADSCs-HDB has a strong osteogenic ability. It can repair segmental bone defects well and is promising to serve as grafting material in bone tissue engineering.

New pathway of icariin-induced MSC osteogenesis: transcriptional activation of TAZ/Runx2 by PI3K/Akt

Icariin has been demonstrated to stimulate mesenchymal stem cell (MSC) osteogensis and activate several signals, such as PI3K/Akt, but how the osteogenesis was sequentially mediated is unclear. Runx2 is one of the osteogenic regulators in MSC and is regulated by the TAZ gene. The purpose of this study was to investigate whether icariin-activated PI3K/Akt crosstalked with the TAZ-Runx2 pathway to regulate MSC osteogenesis. Adipose-derived MSCs were treated with icariin alone, together with TAZ silencing or PI3K/Akt inhibitor. Normal MSCs were used as a control. The activation of PI3K/Akt, expression of TAZ and downstream expression of Runx2 were analyzed. Induction of MSC osteogenesis under different treatments was detected. The results demonstrated that icariin treatment significantly activated PI3K/Akt and TAZ expression, as well as the downstream Runx2 expression. When activation of PI3K/Akt by icariin was inhibited by LY294002, upregulated TAZ expression was reversed, as well as the downstream expression of Runx2. Consequently, with the osteogenic counteracting effects of icariin on MSCs, inhibition of TAZ upregulation by siRNA did not significantly influence PI3K/ Akt activation in icariin-treated MSCs, but icariin-induced upregulation of Runx2 and osteogenic differentiation in MSCs was counteracted. It could be concluded from these findings that icariin treatment activated PI3K/Akt and further mediated the transcriptional activation of the TAZ/Runx2 pathway to induce osteogenic differentiation of MSCs.

Epidermal growth factor promotes proliferation and maintains multipotency of continuous cultured adipose stem cells via activating STAT signal pathway in vitro

This study aimed to investigate the effects of epidermal growth factor (EGF) on the proliferation and differentiation of adipose stem cells (ASC) during the repeated passaging and probe the underlying signal pathway. Results showed that the Ki67 positive rate remained at a high level, the number of ASCs in G0/G1 phase reduced significantly, but ASCs in G2/M phase and S phase increased markedly in ASCs treated with EGF when compared with ASCs without EGF treatment, indicating that EGF made more ASCs in proliferation phase. The adipogenic capability of ASCs without EGF was compromised when compared with that of ASCs after EGF treatment, although significant difference was not observed. The osteogenic and chondrogenic potencies increased significantly in ASC with EGF treatment indicating EGF could maintain differentiative capacity of ASCs. Gene Set Enrichment Analysis showed EGF upregulated the expression of molecules in the epithelial mesenchymal transition and G2/M checkpoint signal pathways. GeneMANIA database analysis indicated the network interaction between EGF and STAT. EGF receptor (EGFR) inhibitor and STAT3 inhibitor were independently used to validate the role of both pathways in these effects. After inhibition of EGFR or STAT3, the proliferation of ASCs was significantly inhibited, and Western blotting showed EGF was able to markedly increase the expression of EGFR and STAT3. These findings suggest EGF not only promotes the proliferation of ASCs and delays their senescence, but also maintains the differentiation potency of ASCs, which are related to the EGF-induced activation of STAT signal pathway.

Effects of Macromolecular Crowding on Human Adipose Stem Cell Culture in Fetal Bovine Serum, Human Serum, and Defined Xeno-Free/Serum-Free Conditions

Microenvironment plays an important role for stem cell proliferation and differentiation. Macromolecular crowding (MMC) was recently shown to assist stem cells in forming their own matrix microenvironment in vitro. The ability of MMC to support adipose stem cell (ASC) proliferation, metabolism, and multilineage differentiation was studied under different conditions: fetal bovine serum- (FBS-) and human serum- (HS-) based media and xeno- and serum-free (XF/SF) media. Furthermore, the immunophenotype of ASCs under MMC was evaluated. The proliferative capacity of ASCs under MMC was attenuated in each condition. However, osteogenic differentiation was enhanced under MMC, shown by increased deposition of mineralized matrix in FBS and HS cultures. Likewise, significantly greater lipid droplet accumulation and increased collagen IV deposition indicated enhanced adipogenesis under MMC in FBS and HS cultures. In contrast, chondrogenic differentiation was attenuated in ASCs expanded under MMC. The ASC immunophenotype was maintained under MMC with significantly higher expression of CD54. However, MMC impaired metabolic activity and differentiation capacity of ASCs in XF/SF conditions. Both the supportive and inhibitory effects of MMC on ASC are culture condition dependent. In the presence of serum, MMC maintains ASC immunophenotype and enhances adipogenic and osteogenic differentiation at the cost of reduced proliferation.

Therapeutic effects of adipose-derived stem cells-based microtissues on erectile dysfunction in streptozotocin-induced diabetic rats

This study aimed to explore the therapeutic effects of adipose-derived stem cells (ADSCs)-based microtissues (MTs) on erectile dysfunction (ED) in streptozotocin (STZ)-induced diabetic rats. Fifty-six 8-week-old Sprague-Dawley rats received intraperitoneal injection of STZ (60 mg kg⁻¹), and 8 weeks later, the determined diabetic rats randomly received intracavernous (IC) injection of phosphate buffer solution (PBS), ADSCs, or MTs. Another eight normal rats equally got IC injection of PBS. MTs were generated with a hanging drop method, and the injected cells were tracked in ADSC- and MT-injected rats. Four weeks after the treatments, intracavernous pressure (ICP), histopathological changes in corpus cavernosum (CC), and functional proteins were measured. Rat cytokine antibody array was used to detect ADSCs or MTs lysate. The results showed that MTs expressed vascular endothelial growth factor (VEGF), nerve growth factor (NGF), and tumor necrosis factor-stimulated gene-6 (TSG-6). MTs injection had a higher retention than ADSCs injection and MTs treatment improved ICP, neuronal nitric oxide synthase (nNOS) expression, smooth muscle, and endothelial contents in diabetic rats, ameliorated local inflammation in CC better. Thus, our findings demonstrate that IC injection of MTs improves erectile function and histopathological changes in STZ-induced diabetic rats and appears to be more promising than traditional ADSCs. The underlying mechanisms involve increased cell retention accompanied with neuroprotection and anti-inflammatory behaviors of the paracrine factors.

Repair of bone defects with prefabricated vascularized bone grafts and double-labeled bone marrow-derived mesenchymal stem cells in a rat model

This study aims to investigate the repair of bone defects with prefabricated vascularized bone grafts and double-labeled bone marrow-derived mesenchymal stem cells (BMSCs) in a rat model. BMSCs were separated from rat bone marrow. LTR-CMVpro-RFP and LTR-CMVpro-GFP were transfected into the BMSCs for in vitro and in vivo tracking. BMSCs-RFP and BMSCs-GFP were induced into endothelial progenitor cells (EPCs) and osteoblasts (OBs). Rats were divided into five groups: Group A: in vitro prefabrication with EPCs-RFP + in vivo prefabrication with arteriovenous vascular bundle + secondary OBs-GFP implantation; Group B: in vitro prefabrication with EPCs-RFP + secondary OBs-GFP implantation; Group C: in vivo prefabrication with arteriovenous vascular bundle + secondary OBs-GFP implantation; Group D: implantation of EPCs-RFP + implantation of with arteriovenous vascular bundle + simultaneous OBs-GFP implantation; Group E: demineralized bone matrix (DBM) grafts (blank control). Among five groups, Group A had the fastest bone regeneration and repair, and the regenerated bone highly resembled normal bone tissues; Group D also had fast bone repair, but the repair was slightly slower than Group A. Therefore, in vitro prefabrication with EPCs-RFP plus in vivo prefabrication with arteriovenous vascular bundle and secondary OBs-GFP implantation could be the best treatment for bone defect.

Repair of urethral defects with polylactid acid fibrous membrane seeded with adipose-derived stem cells in a rabbit model

AIM

The aim of this study is to evaluate the capacity of polylactid acid (PLA) fibrous membrane seeded with allogeneic rabbit adipose tissue-derived stem cells (ADSCs) to repair urethral defects in a rabbit model.

MATERIALS AND METHODS

Rabbit ADSCs were harvested and phenotypically characterized. Twenty-four New Zealand male rabbits with 5-mm urethral mucosal defects were randomly divided into two groups. They underwent urethroplasty either with PLA fibrous membrane seeded with ADSCs (group A) or blank PLA fibrous membrane (group B). At 4 and 6 weeks after urethroplasty, the urethral grafts were collected and analyzed grossly and histologically. The incidence rate of urethrostenosis was measured.

RESULTS

The adipose tissue-derived cells in monolayer culture showed a typical morphology of mesenchymal stem cells (MSCs). They were positive for the MSC marker CD44 but negative for lineage markers CD45 and CD105. Six weeks after surgery, the incidence rate of urethrostenosis in group A was significantly lower than that in group B (p < 0.05). In group A, the ADSC-seeded grafts showed a normal urethral architecture with a thickened muscle layer. In contrast, the newly developed urethra in group B demonstrated a fewer number of urothelial layers and scarce or no smooth muscle cells.

CONCLUSION

The PLA scaffold seeded with ADSCs is effective in urethral regeneration in a rabbit model. ADSCs may represent a promising source of seed cells for urethral tissue engineering.

Stem cell therapy for bone repair: a systematic review and meta-analysis of preclinical studies with large animal models

AIM

Injury to bone is a significant clinical challenge, due to its limited regenerative capacity. The current methods of repairing bone defect are surgical, highly invasive and not always successful. A systematic review and meta-analysis of preclinical studies involving large animals with bone defects were conducted to determine the treatment outcomes with stem cell therapies.

METHODS

A random effects meta-analysis of the available studies was conducted to assess the treatment outcomes including the rate of new bone formation and new bone mineral density (BMD). Stratified analyses were also conducted by separating studies based on each characteristic independently.

RESULTS

Pooled analysis of 20 preclinical studies showed a significant beneficial effect of stem cell therapy in increasing new bone formation (17.79%, 95% confidence interval [CI], 10.54, 25.03; P < 0.001) and BMD (276.94 mg cm(-2) , 95% CI, 62.71, 491.17; P < 0.001) for disease amelioration. Regarding new bone formation, a statistical improvement was similarly detected from randomized controlled trial groups (17.06%, 95% CI, 8.87, 25.24; P < 0.001) and cohort groups (17.43%, 95% CI, 10.79, 24.07; P < 0.001). Exploratory stratified analysis yielded significant predictors of new bone formation including cell number (<10(7) vs. ≥10(7) ; P = 0.048) and the route of cell delivery (combining with matrix scaffold showed more effect than direct cell injection, P = 0.041). The effect of stem cell therapy diminished after 12 weeks.

CONCLUSION

The study results suggest that stem cell therapy improves new bone formation and BMD in bone defect models. Future trials should focus on the transplantation of ≥10(7) stem cells, especially using slow release biodegradable scaffolds or repetitive cell injections.

Allogeneic adipose-derived stem cells regenerate bone in a critical-sized ulna segmental defect

Adipose-derived stem cells (ASCs) with multilineage potential can be induced into osteoblasts, adipocytes and chondrocytes. ASCs as seed cell are widely used in the field of tissue engineering, but most studies either use autologous cells as the source or an immunodeficient animal as the host. In our present study, we explored the feasibility of applying allogeneic ASCs and demineralized bone matrix (DBM) scaffolds for repairing tubular bone defects without using immunosuppressive therapy. Allogeneic ASCs were expanded and seeded on DBM scaffolds and induced to differentiate along the osteogenic lineage. Eight Sprague-Dawley (SD) rats were used in this study and bilateral critical-sized defects (8 mm) of the ulna were created and divided into two groups: with ASC-DBM constructs or DBM alone. The systemic immune response and the extent of bone healing were evaluated post-operatively. Twenty-four weeks after implantation, digital radiography (DR) testing showed that new bones had formed in the experimental group. By contrast, no bone tissue formation was observed in the control group. This study demonstrated that allogeneic ASCs could promote bone regeneration and repair tubular bone defects combined with DBM by histologically typical bone without systemic immune response.

The rational use of animal models in the evaluation of novel bone regenerative therapies

Bone has a high potential for endogenous self-repair. However, due to population aging, human diseases with impaired bone regeneration are on the rise. Current strategies to facilitate bone healing include various biomolecules, cellular therapies, biomaterials and different combinations of these. Animal models for testing novel regenerative therapies remain the gold standard in pre-clinical phases of drug discovery and development. Despite improvements in animal experimentation, excessive poorly designed animal studies with inappropriate endpoints and inaccurate conclusions are being conducted. In this review, we discuss animal models, procedures, methods and technologies used in bone repair studies with the aim to assist investigators in planning and performing scientifically sound experiments that respect the wellbeing of animals. In the process of designing an animal study for bone repair investigators should consider: skeletal characteristics of the selected animal species; a suitable animal model that mimics the intended clinical indication; an appropriate assessment plan with validated methods, markers, timing, endpoints and scoring systems; relevant dosing and statistically pre-justified sample sizes and evaluation methods; synchronization of the study with regulatory requirements and additional evaluations specific to cell-based approaches. This article is part of a Special Issue entitled "Stem Cells and Bone".

Hepatocyte growth factor gene-modified adipose-derived mesenchymal stem cells ameliorate radiation induced liver damage in a rat model

Liver damage caused by radiotherapy is associated with a high mortality rate, but no established treatment exists. Adipose-derived mesenchymal stem cells (ADSCs) are capable of migration to injured tissue sites, where they aid in the repair of the damage. Hepatocyte growth factor (HGF) is critical for damage repair due to its anti-apoptotic, anti-fibrotic and cell regeneration-promoting effects. This study was performed to investigate the therapeutic effects of HGF-overexpressing ADSCs on radiation-induced liver damage (RILD). ADSCs were infected with a lentivirus encoding HGF and HGF-shRNA. Sprague-Dawley (SD) rats received 60Gy of irradiation to induce liver injury and were immediately given either saline, ADSCs, ADSCs + HGF or ADSCs + shHGF. Two days after irradiation, a significant reduction in apoptosis was observed in the HGF-overexpressing ADSC group compared with the RILD group, as assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Scanning electron microscopy showed chromatin condensation after irradiation, which was ameliorated in the group that received ADSCs and was reversed in the group that received HGF-overexpressing ADSCs. HGF-overexpressing ADSCs ameliorated radiation- induced liver fibrosis through down regulation of α-SMA and fibronectin. Hepatocyte regeneration was significantly improved in rats treated with ADSCs compared with rats from the RILD group), as assessed by Ki-67 immunohistochemistry. Rats that received HGF-overexpressing ADSCs showed an even greater level of hepatocyte regeneration. HGF-overexpressing ADSCs completely blocked the radiation-induced increase in the enzymes ALT and AST. The effect of mitigating RILD was compromised in the ADSC + shHGF group compared with the ADSC group. Altogether, these results suggest that HGF-overexpressing ADSCs can significantly improve RILD in a rat model, which may serve as a valuable therapeutic alternative.

Concise review: the immune status of mesenchymal stem cells and its relevance for therapeutic application

Multipotentiality and anti-inflammatory activity, the two main properties of mesenchymal stem cells (MSCs), underlie their therapeutic prospective. During the past decade, numerous studies in animal models and clinical trials explored the potential of MSCs in the treatment of diseases associated with tissue regeneration and inflammatory control. Other qualities of MSCs: ready accessibility in bone marrow and fat tissue and rapid expansion in culture make the therapeutic use of patients' own cells feasible. The prevailing belief that MSCs are nonimmunogenic encouraged the use of unrelated donor cells in immune-competent recipients. The data emerging from studies performed with immune-incompatible cells in animal models for a wide-range of human diseases show, however, conflicting results and cast doubt on the immune privileged status of MSCs. Our analysis of the preclinical literature in this review is aimed to gain a better understanding of the therapeutic potential of immune-incompatible MSCs. Emphasis was laid on applications for enhancement of tissue repair in the absence of immune-suppressive therapy.

Changes in immunological profile of allogeneic mesenchymal stem cells after differentiation: should we be concerned?

Mesenchymal stem cells (MSCs) are an adult stromal cell population possessing potent differentiation capacity and a potential for use across major histocompatibility complex barriers. Although allogeneic MSCs have potent immunosuppressive properties, evidence also suggests that they elicit a weak allogeneic immune response. However, the effect of induced differentiation on the immunosuppressive ability and immunogenicity of allogeneic MSCs is a potential obstacle when applying MSCs in tissue replacement therapies. These concerns will be explored in this review, with particular emphasis on changes in the cell surface expression of immunogenic markers, changes in the secretion of immunosuppressive molecules and in vivo functional benefits of the cell therapy. We review the literature from a translational point of view, focusing on pre-clinical studies that have utilised and analysed the effects of allogeneic immune responses on the ability of allogeneic MSCs to regenerate damaged tissue in models of bone, heart and cartilage defects.

Different culture conditions modulate the immunological properties of adipose stem cells

The potential of human adipose stem cells (ASCs) for regenerative medicine has received recognition owing to their ease of isolation and their multilineage differentiation capacity. Additionally, low immunogenicity and immunosuppressive properties make them a relevant cell source when considering immunomodulation therapies and allogeneic stem cell treatments. In the current study, immunogenicity and immunosuppression of ASCs were determined through mixed lymphocyte reactions. The immunogenic response was analyzed after cell isolation and expansion in fetal bovine serum (FBS), human serum (HS)-supplemented medium, and xeno-free and serum-free (XF/SF) conditions. Additionally, the immunophenotype and the secretion of CXC chemokine ligand 8 (CXCL8), CXCL9, CXCL10, C-C chemokine ligand 2 (CCL2), CCL5, interleukin 2 (IL-2), IL-4, IL-6, IL-10, IL-17A, tumor necrosis factor-α, interferon-γ, transforming growth factor-β1, indoleamine 2,3-deoxygenase, Galectin-1, and Galectin-3 were analyzed. The results showed that ASCs were weakly immunogenic when expanded in any of the three conditions. The significantly strongest suppression was observed with cells expanded in FBS conditions, whereas higher ASC numbers were required to display suppression in HS or XF/SF conditions. In addition, statistically significant differences in protein secretion were observed between direct versus indirect cocultures and between different culture conditions. The characteristic immunophenotype of ASCs was maintained in all conditions. However, in XF/SF conditions, a significantly lower expression of CD54 (intercellular adhesion molecule 1) and a higher expression of CD45 (lymphocyte common antigen) was observed at a low passage number. Although culture conditions have an effect on the immunogenicity, immunosuppression, and protein secretion profile of ASCs, our findings demonstrated that ASCs have low immunogenicity and promising immunosuppressive potential whether cultured in FBS, HS, or XF/SF conditions.

Proliferation and differentiation of human adipose-derived mesenchymal stem cells (ASCs) into osteoblastic lineage are passage dependent

OBJECTIVE

The effect of in vitro expansion of human adipose-derived stem cells (ASCs) on stem cell properties is controversial. We examined serial subcultivation with expansion on the ability of ASCs to grow and differentiate into osteoblastic lineages.

DESIGN

Flow cytometric analysis, growth kinetics, cell population doubling time, light microscopy and confocal analysis, and osteogenesis induction were performed to assess growth and osteogenic potential of subcultivated ASCs at passages 2 (P2), P4 and P6.

RESULTS

Flow cytometric analysis revealed that ASCs at P2 express classical mesenchymal stem cell markers including CD44, CD73, and CD105, but not CD14, CD19, CD34, CD45, or HLA-DR. Calcium deposition and alkaline phosphatase activity were the highest at P2 but completely abrogated at P4. Increased passage number impaired cell growth; P2 cultures exhibited exponential growth, while cells at P4 and P6 showed near linear growth with cell population doubling times increased from 3.2 at P2 to 4.8 d at P6. Morphologically, cells in various subcultivation stages showed flattened shape at low density but spindle-like structures at confluency as judged by phalloidin staining.

CONCLUSIONS

Osteogenic potential of ASCs is impaired by successive passaging and may not serve as a useful clinical source of osteogenic ASCs past P2.

Hypoxia-pretreated human MSCs attenuate acute kidney injury through enhanced angiogenic and antioxidative capacities

Hypoxia preconditioning has been confirmed as an effective strategy to enhance the therapeutic potentials of mesenchymal stem cells (MSCs), such as for myocardial ischemia. However, whether hypoxia preconditioning would produce beneficial effects on MSC-based renal repair has not been demonstrated. In the study, we aimed to determine the feasibility and efficacy of hypoxia preconditioning to enhance MSC-based therapy of acute kidney injury (AKI). MSCs were isolated from human adipose tissues. The paracrine effects of MSCs under normoxia and hypoxia were determined in vitro. Rats of AKI were induced by kidney I/R surgery and randomly divided into three groups: I/R control receiving PBS injection; MSC group receiving normal MSC injection; hypoMSC group receiving hypoxia-preconditioned MSC injection. It was demonstrated in vitro that paracrine effects of MSCs were significantly enhanced, especially angiogenic factors. Dihydroethidium (DHE) staining showed that antioxidative activities of MSCs were significantly enhanced by hypoxia stimulation. Vascularization, apoptosis, and histological injury were all significantly improved in hypoMSC injected group compared with that in control and MSC injected groups. Finally, the renal function was also significantly improved in hypoMSC injected group compared with that in the other two groups as assessed by the serum creatinine and BUN levels.