Immunomodulatory Effects of Different Cellular Therapies of Bone Marrow Origin on Chimerism Induction and Maintenance Across MHC Barriers in a Face Allotransplantation Model

Chimeric Cell Therapy Transfers Healthy Donor Mitochondria in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a severe X-linked disorder characterized by dystrophin gene mutations and mitochondrial dysfunction, leading to progressive muscle weakness and premature death of DMD patients. We developed human Dystrophin Expressing Chimeric (DEC) cells, created by the fusion of myoblasts from normal donors and DMD patients, as a foundation for DT-DEC01 therapy for DMD. Our preclinical studies on mdx mouse models of DMD revealed enhanced dystrophin expression and functional improvements in cardiac, respiratory, and skeletal muscles after systemic intraosseous DEC administration. The current study explored the feasibility of mitochondrial transfer and fusion within the created DEC cells, which is crucial for developing new therapeutic strategies for DMD. Following mitochondrial staining with MitoTracker Deep Red and MitoTracker Green dyes, mitochondrial fusion and transfer was assessed by Flow cytometry (FACS) and confocal microscopy. The PEG-mediated fusion of myoblasts from normal healthy donors (MBN/MBN) and normal and DMD-affected donors (MBN/MBDMD), confirmed the feasibility of myoblast and mitochondrial fusion and transfer. The colocalization of the mitochondrial dyes MitoTracker Deep Red and MitoTracker Green confirmed the mitochondrial chimeric state and the creation of chimeric mitochondria, as well as the transfer of healthy donor mitochondria within the created DEC cells. These findings are unique and significant, introducing the potential of DT-DEC01 therapy to restore mitochondrial function in DMD patients and in other diseases where mitochondrial dysfunction plays a critical role.

Chimeric Cell Therapies as a Novel Approach for Duchenne Muscular Dystrophy (DMD) and Muscle Regeneration

Chimerism-based strategies represent a pioneering concept which has led to groundbreaking advancements in regenerative medicine and transplantation. This new approach offers therapeutic potential for the treatment of various diseases, including inherited disorders. The ongoing studies on chimeric cells prompted the development of Dystrophin-Expressing Chimeric (DEC) cells which were introduced as a potential therapy for Duchenne Muscular Dystrophy (DMD). DMD is a genetic condition that leads to premature death in adolescent boys and remains incurable with current methods. DEC therapy, created via the fusion of human myoblasts derived from normal and DMD-affected donors, has proven to be safe and efficacious when tested in experimental models of DMD after systemic-intraosseous administration. These studies confirmed increased dystrophin expression, which correlated with functional and morphological improvements in DMD-affected muscles, including cardiac, respiratory, and skeletal muscles. Furthermore, the application of DEC therapy in a clinical study confirmed its long-term safety and efficacy in DMD patients. This review summarizes the development of chimeric cell technology tested in preclinical models and clinical studies, highlighting the potential of DEC therapy in muscle regeneration and repair, and introduces chimeric cell-based therapies as a promising, novel approach for muscle regeneration and the treatment of DMD and other neuromuscular disorders.

Transplantation of Donor-Recipient Chimeric Cells Restores Peripheral Blood Cell Populations and Increases Survival after Total Body Irradiation-Induced Injury in a Rat Experimental Model

Current therapies for acute radiation syndrome (ARS) involve bone marrow transplantation (BMT), leading to graft-versus-host disease (GvHD). To address this challenge, we have developed a novel donor-recipient chimeric cell (DRCC) therapy to increase survival and prevent GvHD following total body irradiation (TBI)-induced hematopoietic injury without the need for immunosuppression. In this study, 20 Lewis rats were exposed to 7 Gy TBI to induce ARS, and we assessed the efficacy of various cellular therapies following systemic intraosseous administration. Twenty Lewis rats were randomly divided into four experimental groups (n = 5/group): saline control, allogeneic bone marrow transplantation (alloBMT), DRCC, and alloBMT + DRCC. DRCC were created by polyethylene glycol-mediated fusion of bone marrow cells from 24 ACI (RT1a) and 24 Lewis (RT11) rat donors. Fusion feasibility was confirmed by flow cytometry and confocal microscopy. The impact of different therapies on post-irradiation peripheral blood cell recovery was evaluated through complete blood count, while GvHD signs were monitored clinically and histopathologically. The chimeric state of DRCC was confirmed. Post-alloBMT mortality was 60%, whereas DRCC and alloBMT + DRCC therapies achieved 100% survival. DRCC therapy also led to the highest white blood cell counts and minimal GvHD changes in kidney and skin samples, in contrast to alloBMT treatment. In this study, transplantation of DRCC promoted the recovery of peripheral blood cell populations after TBI without the development of GVHD. This study introduces a novel and promising DRCC-based bridging therapy for treating ARS and extending survival without GvHD.

Novel cell-based strategies for immunomodulation in vascularized composite allotransplantation

PURPOSE OF REVIEW

Vascularized composite allotransplantation (VCA) has become a clinical reality in the past two decades. However, its routine clinical applications are limited by the risk of acute rejection, and the side effects of the lifelong immunosuppression. Therefore, there is a need for new protocols to induce tolerance and extend VCA survival. Cell- based therapies have emerged as an attractive strategy for tolerance induction in VCA. This manuscript reviews the current strategies and applications of cell-based therapies for tolerance induction in VCA.

RECENT FINDINGS

Cellular therapies, including the application of bone marrow cells (BMC), mesenchymal stem cells (MSC), adipose stem cells, regulatory T cells (Treg) cells, dendritic cells and donor recipient chimeric cells (DRCC) show promising potential as a strategy to induce tolerance in VCA. Ongoing basic science research aims to provide insights into the mechanisms of action, homing, functional specialization and standardization of these cellular therapies. Additionally, translational preclinical and clinical studies are underway, showing encouraging outcomes.

SUMMARY

Cellular therapies hold great potential and are supported by preclinical studies and clinical trials demonstrating safety and efficacy. However, further research is needed to develop novel cell-based immunosuppressive protocol for VCA.

Human Multi-Chimeric Cell (HMCC) Therapy as a Novel Approach for Tolerance Induction in Transplantation

Cellular therapies are regarded as the most promising approach for inducing transplant tolerance without life-long immunosuppression in solid organ and vascularized composite allotransplantation (VCA). Currently, no therapies are achieving this goal. This study introduces a novel Human Multi-Chimeric Cell (HMCC) line created by fusion of umbilical cord blood (UCB) cells, from three unrelated donors as an alternative therapeutic approach to bone marrow transplantation and tolerance induction in solid organ and VCA transplants. We performed eighteen ex vivo polyethylene glycol mediated fusions of human UCB cells from three unrelated donors to create HMCC. Mononuclear cells labeled with PKH26, PKH67, and eFluor™ 670 fluorescent dyes were fused and sorted creating a new population of triple-labeled (PKH26/PKH67/eFluor™ 670) HMCC. The creation of HMCC from three unrelated human UCB donors was confirmed by flow cytometry and confocal microscopy. Genotyping analyses determined the tri-chimeric state of HMCC by presence of parent alleles and selected loci specific for each of three UCB donors. Phenotype characterization confirmed hematopoietic markers distribution, comparable to UCB donors. HMCC maintained viability and displayed a low apoptosis level. The COMET assay revealed absence of genotoxicity, confirming fusion safety. Colony forming units assay showed clonogenic properties of HMCC. This study confirmed the feasibility of HMCC creation from three unrelated human UCB donors and characterized tri-chimeric state, hematopoietic phenotype, viability, safety, and clonogenic properties of HMCC. The created HMCC line, representing genotype characteristics of three unrelated human UCB donors, introduces a novel therapeutic approach for bone marrow, solid organ, and VCA transplants.

Dystrophin Expressing Chimeric (DEC) Cell Therapy for Duchenne Muscular Dystrophy: A First-in-Human Study with Minimum 6 Months Follow-up

Duchenne Muscular Dystrophy (DMD) is a X-linked progressive lethal muscle wasting disease for which there is no cure. We present first-in-human study assessing safety and efficacy of novel Dystrophin Expressing Chimeric (DEC) cell therapy created by fusion of patient myoblasts with myoblasts of normal donor origin. We report here on safety and functional outcomes of the first 3 DMD patients. No study related adverse events (AE) and no serious adverse events (SAE) were observed up to 14 months after systemic-intraosseous administration of DEC01. Ambulatory patients showed improvements in functional tests (6-Minute Walk Test (6MWT), North Star Ambulatory Assessment (NSAA)) and both, ambulatory and non-ambulatory in PUL, strength and fatigue resistance which correlated with improvement of Electromyography (EMG) parameters. DEC01 therapy does not require immunosuppression, involves no risks of off target mutations, is not dependent upon the causative mutation and is therefore a universal therapy that does not use viral vectors and therefore can be readministered, if needed. This study was approved by the Bioethics Committee (approval No. 46/2019). Mechanism of action of the Dystrophin Expressing Chimeric Cell (DEC) cells created via ex vivo fusion of human myoblast from normal and DMD-affected donors. Following systemic-intraosseous administration, DEC engraft and fuse with the myoblasts of DMD patients, deliver dystrophin and improve muscle strength and function. (Created with BioRender.com).

A Brief Review of Duchenne Muscular Dystrophy Treatment Options, with an Emphasis on Two Novel Strategies

Despite the full cloning of the Dystrophin cDNA 35 years ago, no effective treatment exists for the Duchenne Muscular Dystrophy (DMD) patients who have a mutation in this gene. Many treatment options have been considered, investigated preclinically and some clinically, but none have circumvented all barriers and effectively treated the disease without burdening the patients with severe side-effects. However, currently, many novel therapies are in the pipelines of research labs and pharmaceutical companies and many of these have progressed to clinical trials. A brief review of these promising therapies is presented, followed by a description of two novel technologies that when utilized together effectively treat the disease in the mdx mouse model. One novel technology is to generate chimeric cells from the patient’s own cells and a normal donor. The other technology is to systemically transplant these cells into the femur via the intraosseous route.

Long-Term Protective Effect of Human Dystrophin Expressing Chimeric (DEC) Cell Therapy on Amelioration of Function of Cardiac, Respiratory and Skeletal Muscles in Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a lethal disease caused by mutations in dystrophin encoding gene, causing progressive degeneration of cardiac, respiratory, and skeletal muscles leading to premature death due to cardiac and respiratory failure. Currently, there is no cure for DMD. Therefore, novel therapeutic approaches are needed for DMD patients.

We have previously reported functional improvements which correlated with increased dystrophin expression following administration of dystrophin expressing chimeric (DEC) cells of myoblast origin to the mdx mouse models of DMD.

In the current study, we confirmed dose-dependent protective effect of human DEC therapy created from myoblasts of normal and DMD-affected donors, on restoration of dystrophin expression and amelioration of cardiac, respiratory, and skeletal muscle function at 180 days after systemic-intraosseous DEC administration to mdx/scid mouse model of DMD. Functional improvements included maintenance of ejection fraction and fractional shortening levels on echocardiography, reduced enhanced pause and expiration time on plethysmography and improved grip strength and maximum stretch induced contraction of skeletal muscles. Improved function was associated with amelioration of mdx muscle pathology revealed by reduced muscle fibrosis, reduced inflammation and improved muscle morphology confirmed by reduced number of centrally nucleated fibers and normalization of muscle fiber diameters. Our findings confirm the long-term systemic effect of DEC therapy in the most severely affected by DMD organs including heart, diaphragm, and long skeletal muscles.

These encouraging preclinical data introduces human DEC as a novel therapeutic modality of Advanced Therapy Medicinal Product (ATMP) with the potential to improve or halt the progression of DMD and enhance quality of life of DMD patients.

A systematic review of immunomodulatory strategies used in skin-containing preclinical vascularized composite allotransplant models

BACKGROUND

Acute rejection remains a vexing problem in vascularized composite allotransplantation (VCA). Available immunosuppressive regimens are successful at minimizing alloimmune response and allowing VCA in humans. However, repeated rejection episodes are common, and systemic side effects of the current standard regimen (Tacrolimus, MMF, Prednisone) are dose limiting. Novel immunomodulatory approaches to improve allograft acceptance and minimize systemic toxicity are continuously explored in preclinical models. We aimed to systematically summarize past and current approaches to help guide future research in this complex field.

METHODS

We conducted a systematic review of manuscripts listed in the MEDLINE and PubMed databases. For inclusion, articles had to primarily investigate the effect of a therapeutic approach on prolonging the survival of a skin-containing preclinical VCA model. Non-VCA studies, human trials, anatomical and feasibility studies, and articles written in a language other than English were excluded. We followed the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines.

RESULTS

The search retrieved 980 articles of which 112 articles were ultimately included. The majority of investigations used a rat model. An orthotopic hind limb VCA model was used in 53% of the studies. Cell and drug-based approaches were investigated 58 and 52 times, respectively. We provide a comprehensive review of immunomodulatory strategies used in VCA preclinical research over a timeframe of 44 years.

CONCLUSION

We identify a transition from anatomically non-specific to anatomical models mimicking clinical needs. As limb transplants have been most frequently performed, preclinical research focused on using the hind limb model. We also identify a transition from drug-based suppression therapies to cell-based immunomodulation strategies.

Immunosuppressed Miniswine as a Model for Testing Cell Therapy Success: Experience With Implants of Human Salivary Stem/Progenitor Cell Constructs

An urgent need exists to develop large animal models for preclinical testing of new cell therapies designed to replace lost or damaged tissues. Patients receiving irradiation for treatment of head and neck cancers frequently develop xerostomia/dry mouth, a condition that could one day be treated by cell therapy to repopulate functional saliva-producing cells. Using immunosuppression protocols developed for patients receiving whole face transplants, we successfully used immunosuppressed miniswine as a suitable host animal to evaluate the long-term stability, biocompatibility, and fate of matrix-modified hyaluronate (HA) hydrogel/bioscaffold materials containing encapsulated salivary human stem/progenitor cells (hS/PCs). An initial biocompatibility test was conducted in parotids of untreated miniswine. Subsequent experiments using hS/PC-laden hydrogels were performed in animals, beginning an immunosuppression regimen on the day of surgery. Implant sites included the kidney capsule for viability testing and the parotid gland for biointegration time periods up to eight weeks. No transplant rejection was seen in any animal assessed by analysis of the tissues near the site of the implants. First-generation implants containing only cells in hydrogel proved difficult to handle in the surgical suite and were modified to adhere to a porcine small intestinal submucosa (SIS) membrane for improved handling and could be delivered through the da Vinci surgical system. Several different surgical techniques were assessed using the second-generation 3D-salivary tissue (3D-ST) for ease and stability both on the kidney capsule and in the capsule-less parotid gland. For the kidney, sliding the implant under the capsule membrane and quick stitching proved superior to other methods. For the parotid gland, creation of a tissue “pocket” for placement and immediate multilayer tissue closure were well tolerated with minimal tissue damage. Surgical clips were placed as fiduciary markers for tissue harvest. Some implant experiments were conducted with miniswine 90 days post-irradiation when salivation decreased significantly. Sufficient parotid tissue remained to allow implant placement, and animals tolerated immunosuppression. In all experiments, viability of implanted hS/PCs was high with clear signs of both vascular and nervous system integration in the parotid implants. We thus conclude that the immunosuppressed miniswine is a high-value emerging model for testing human implants prior to first-in-human trials.

The Positive Impact of Donor Bone Marrow Cells Transplantation into Immunoprivileged Compartments on the Survival of Vascularized Skin Allografts

Using the vascularized skin allograft (VSA) model, we compared the tolerogenic effects of different allogeneic bone marrow transplantation (BMT) delivery routes into immunoprivileged compartments under a 7-day protocol immunosuppressive therapy. Twenty-eight fully MHC mismatched VSA transplants were performed between ACI (RT1^a) donors and Lewis (RT1¹) recipients in four groups of seven animals each, under a 7-day protocol of alfa/beta TCRmAb/CsA (alpha/beta-TCR monoclonal antibodies/Cyclosporine A therapy). Donor bone marrow cells (BMC) (100 × 106 cells) were injected into three different immunoprivileged compartments: Group 1: Control, without cellular supportive therapy, Group 2: Intracapsular BMT, Group 3: Intragonadal BMT, Group 4: Intrathecal BMT. In Group 2, BMC were transplanted under the kidney capsule. In Group 3, BMC were transplanted into the right testis between tunica albuginea and seminiferous tubules, and in Group 4, cells were injected intrathecally. The assessment included: skin evaluation for signs and grade of rejection and immunohistochemistry for donor cells engraftment into host lymphoid compartments. Donor-specific chimerism for MHC class I (RT1^a) antigens and the presence of CD4⁺/CD25⁺ T cells were assessed in the peripheral blood of recipients. The most extended allograft survival, 50–78 days, was observed in Group 4 after intrathecal BMT. The T cells CD4⁺/CD25⁺ in the peripheral blood were higher after intrathecal BMC injection than other experimental groups at each post-transplant time point. Transplantation of BMC into immunoprivileged compartments delayed rejection of fully mismatched VSA and induction of robust, donor-specific chimerism.

Human dystrophin expressing chimeric (DEC) cell therapy ameliorates cardiac, respiratory, and skeletal muscle's function in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a progressive and lethal disease, caused by X‐linked mutations of the dystrophin encoding gene. The lack of dystrophin leads to muscle weakness, degeneration, fibrosis, and progressive loss of skeletal, cardiac, and respiratory muscle function resulting in premature death due to the cardiac and respiratory failure. There is no cure for DMD and current therapies neither cure nor arrest disease progression. Thus, there is an urgent need to develop new approaches and safer therapies for DMD patients. We have previously reported functional improvements which correlated with increased dystrophin expression following transplantation of dystrophin expressing chimeric (DEC) cells of myoblast origin to the mdx mouse models of DMD. In this study, we demonstrated that systemic‐intraosseous transplantation of DEC human cells derived from myoblasts of normal and DMD‐affected donors, increased dystrophin expression in cardiac, respiratory, and skeletal muscles of the mdx/scid mouse model of DMD. DEC transplant correlated with preservation of ejection fraction and fractional shortening on echocardiography, improved respiratory function on plethysmography, and improved strength and function of the limb skeletal muscles. Enhanced function was associated with improved muscle histopathology, revealing reduced mdx pathology, fibrosis, decreased inflammation, and preserved muscle morphology and architecture. Our findings confirm that DECs generate a systemic protective effect in DMD‐affected target organs. Therefore, DECs represents a novel therapeutic approach with the potential to preserve or enhance multiorgan function of the skeletal, cardiac, and respiratory muscles critical for the well‐being of DMD patients.

Donor Recipient Chimeric Cells Induce Chimerism and Extend Survival of Vascularized Composite Allografts

This study evaluated the efficacy of donor recipient chimeric cell (DRCC) therapy created by fusion of donor and recipient derived bone marrow cells (BMC) in chimerism and tolerance induction in a rat vascularized composite allograft (VCA) model. Twenty-four VCA (groin flaps) from MHC-mismatched ACI (RT1^a) donors were transplanted to Lewis (RT1^l) recipients. Rats were randomly divided into (n = 6/group): Group 1—untreated controls, Groups 2—7-day immunosuppression controls, Group 3—DRCC, and Group 4—DRCC with 7-day anti-αβTCR monoclonal antibody and cyclosporine A protocol. DRCC created by polyethylene glycol-mediated fusion of ACI and Lewis BMC were cultured and transplanted (2–4 × 10⁶) to VCA recipients via intraosseous delivery route. Flow cytometry assessed peripheral blood chimerism while fluorescent microscopy and PCR tested the presence of DRCC in the recipient’s blood, bone marrow (BM), and lymphoid organs at the study endpoint (VCA rejection). No complications were observed after DRCC intraosseous delivery. Group 4 presented the longest average VCA survival (79.3 ± 30.9 days) followed by Group 2 (53.3 ± 13.6 days), Group 3 (18 ± 7.5 days), and Group 1 (8.5 ± 1 days). The highest chimerism level was detected in Group 4 (57.9 ± 6.2%) at day 7 post-transplant. The chimerism declined at day 21 post-transplant and remained at 10% level during the entire follow-up period. Single dose of DRCC therapy induced long-term multilineage chimerism and extended VCA survival. DRCC introduces a novel concept of customized donor-recipient cell-based therapy supporting solid organ and VCA transplants.

Development of Donor Recipient Chimeric Cells of bone marrow origin as a novel approach for tolerance induction in transplantation

Background

Cell therapies and chimerism-based strategies are currently the most successful approach for tolerance induction in transplantation. This study aimed to establish and characterize novel Donor Recipient Chimeric Ccell (DRCC) therapy of bone marrow (BM) origin presenting donor-recipient phenotype to support tolerance induction.

Methods

Ex vivo fusions of fully MHC-mismatched BM cells from ACI (RT1^a) and Lewis (RT1^l) rats were performed using polyethylene-glycol (PEG). The creation of rat DRCC was tested by flow cytometry (FC), confocal microscopy and PCR. FC characterized DRCC's phenotype (CD3, CD4, CD8, CD45, CD90, CD11b/c, CD45RA, OX-82, or CD4/CD25) and apoptosis, while mixed lymphocyte reaction assessed DRCC's immunogenicity and colony forming unit assay tested DRCC's differentiation and proliferation. DRCC's polyploidy was evaluated using Hoechst33342 staining and COMET assay tested genotoxicity of fusion procedure. ELISA analyzed the secretion of IL-2, IL-4, IL-10, TGFß1, IFNγ and TNFα by DRCC at day 1, 5 and 14 post-fusion. The DRCC's phenotype after long-term culturing was assessed by reverse-transcription PCR.

Results

The chimeric state of DRCC was confirmed. Fusion did not change the expression of hematopoietic markers compared to BM controls. Although an increased number of early and late apoptotic (Annexin V⁺/Sytox blue^- and Annexin V⁺/Sytox blue⁺, respectively) DRCC was detected at 24h post-fusion, the number significantly decreased at day 5 (38.4%±3.1% and 22.6%±2.5%, vs. 28.3%±2.5% and 13.9%±2.6%, respectively, P<0.05). DRCC presented decreased immunogenicity, increased expression of IL-10 and TGFβ1 and proliferative potential comparable to BM controls. The average percentage of tetraploid DRCC was 3.1%±0.2% compared to 0.96%±0.1% in BM controls. The lack of damage to the DRCC's DNA content supported the DRCC's safety. In culture, DRCC maintained proliferation for up to 28 days while preserving hematopoietic profile.

Conclusions

This study confirmed feasibility of DRCC creation via ex vivo PEG mediated fusion. The created DRCC revealed pro-tolerogenic properties indicating potential immunomodulatory effect of DRCC therapy when applied in vivo to support tolerance induction in solid organ and vascularized composite allograft transplantation.

Transplantation of Dystrophin Expressing Chimeric Human Cells of Myoblast/Mesenchymal Stem Cell Origin Improves Function in Duchenne Muscular Dystrophy Model

Duchenne muscular dystrophy (DMD) is a lethal X-linked disorder caused by mutations in dystrophin gene. Currently, there is no cure for DMD. Cell therapies are challenged by limited engraftment and rejection. Thus, more effective and safer therapeutic approaches are needed for DMD. We previously reported increased dystrophin expression correlating with improved function after transplantation of dystrophin expressing chimeric (DEC) cells of myoblast origin in the mdx mouse models of DMD. This study established new DEC cell line of myoblasts and mesenchymal stem cells (MSC) origin and tested its efficacy and therapeutic potential in mdx/scid mouse model of DMD. Fifteen ex vivo cell fusions of allogenic human myoblast [normal myoblasts (MBN)] and normal human bone marrow-derived MSC (MSCN) from normal donors were performed using polyethylene glycol. Flow cytometry, confocal microscopy, polymerase chain reaction (PCR)-short tandem repeats, polymerase chain reaction-reverse sequence-specific oligonucleotide probe assessed chimeric state of fused MBN/MSCN DEC cells, whereas Comet assay assessed fusion procedure safety testing genotoxicity. Immunofluorescence and real-time PCR assessed dystrophin expression and myogenic differentiation. Mixed lymphocyte reaction (MLR) evaluated DEC's immunogenicity. To test MBN/MSCN DEC efficacy in vivo, gastrocnemius muscle of mdx/scid mice were injected with vehicle (n = 12), nonfused MBN and MSCN (n = 9, 0.25 × 106/each) or MBN/MSCN DEC (n = 9, 0.5 × 106). Animals were evaluated for 90 days using ex vivo and in vivo muscle strength tests. Histology and immunofluorescence staining assessed dystrophin expression, centrally nucleated fibers and scar tissue formation. Post-fusion, MBN/MSCN DEC chimeric state, myogenic differentiation, and dystrophin expression were confirmed. MLR reveled reduced DEC's immune response compared with controls (P < 0.05). At 90 days post-DEC transplant, increase in dystrophin expression (20.26% ± 2.5%, P < 0.05) correlated with improved muscle strength and function in mdx/scid mice. The created human MBN/MSCN DEC cell line introduces novel therapeutic approach combining myogenic and immunomodulatory properties of MB and MSC, and as such may open a universal approach for muscle regeneration in DMD.

The past the present and the future of face transplantation

PURPOSE OF REVIEW

Face transplantation represents vascularized composite allotransplantation (VCA) organ and became one of the most rewarding reconstructive options for severely disfigured patients. This review summarizes the past, current and future challenges of face transplantation, based on our experience and literature reports.

RECENT FINDINGS

In 2005, first partial face transplantation was reported by French team. In 2008, we have performed the US first near-total face transplantation. Currently, more than 40 face transplant cases were reported worldwide. Based on the outcomes of our three patients and the literature reports, face transplantation improved aesthetics, function and the quality of life of face transplant patients. However, there are still many challenges encountered including the side effects of immunosuppressive protocols, the psychological and social problems as well as the financial challenges which need to be address in the near future to maintain face transplantation in the armamentarium of reconstructive surgery.

SUMMARY

Currently, feasibility of face transplantation was confirmed; however, the life-long immunosuppressive protocols bearing serious side effects are still required to prevent face rejection. Thus, for the future of face and other VCA, novel approaches of cell-based therapies or engineered scaffolds should be developed to make face transplantation safer.

Innovations and Future Directions in Head and Neck Microsurgical Reconstruction

Head and neck reconstructive microsurgery is constantly innovating because of a combination of multidisciplinary advances. This article examines recent innovations that have affected the field as well as presenting research leading to future advancement. Innovations include the use of virtual surgical planning and three-dimensional printing in craniofacial reconstruction, advances in intraoperative navigation and imaging, as well as postoperative monitoring, development of minimally invasive reconstructive microsurgery techniques, integration of regenerative medicine and stem cell biology with reconstruction, and the dramatic advancement of face transplant.

Cardiac Protection after Systemic Transplant of Dystrophin Expressing Chimeric (DEC) Cells to the mdx Mouse Model of Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a progressive lethal disease caused by X-linked mutations of the dystrophin gene. Dystrophin deficiency clinically manifests as skeletal and cardiac muscle weakness, leading to muscle wasting and premature death due to cardiac and respiratory failure. Currently, no cure exists. Since heart disease is becoming a leading cause of death in DMD patients, there is an urgent need to develop new more effective therapeutic strategies for protection and improvement of cardiac function. We previously reported functional improvements correlating with dystrophin restoration following transplantation of Dystrophin Expressing Chimeric Cells (DEC) of myoblast origin in the mdx and mdx/scid mouse models. Here, we confirm positive effect of DEC of myoblast (MB^wt/MB^mdx) and mesenchymal stem cells (MB^wt/MSC^mdx) origin on protection of cardiac function after systemic DEC transplant. Therapeutic effect of DEC transplant (0.5 × 10⁶) was assessed by echocardiography at 30 and 90 days after systemic-intraosseous injection to the mdx mice. At 90 days post-transplant, dystrophin expression in cardiac muscles of DEC injected mice significantly increased (15.73% ± 5.70 –MB^wt/MB^mdx and 5.22% ± 1.10 – MB^wt/MSC^mdx DEC) when compared to vehicle injected controls (2.01% ± 1.36) and, correlated with improved ejection fraction and fractional shortening on echocardiography. DEC lines of MB and MSC origin introduce a new promising approach based on the combined effects of normal myoblasts with dystrophin delivery capacities and MSC with immunomodulatory properties. Our study confirms feasibility and efficacy of DEC therapy on cardiac function and represents a novel therapeutic strategy for cardiac protection and muscle regeneration in DMD.

The effect of thymus transplantation on donor-specific chimerism in the rat model of composite osseomusculocutaneous sternum, ribs, thymus, pectoralis muscles, and skin allotransplantation

INTRODUCTION

Research on tolerance has proven that development of donor-specific chimerism (DSC) may accompany tolerance induction in vascularized composite allotransplantation (VCA). In this study, we aimed to determine the effect of thymus transplantation on the induction of DSC in rat VCA model of osseomusculocutaneous sternum (OMCS) and osseomusculocutaneous sternum and thymus (OMCST) allotransplantation.

MATERIALS AND METHODS

A total of 20 Lewis-Brown Norway and Lewis rats, 5-6 weeks old, weighting between 120 and 150 g, were used in the study. OMCS (n = 5) and OMCST (n = 5) allografts were harvested from Lewis-Brown Norway donors (RT1^l + n ) based on the common carotid artery and external jugular vein, and a heterotopic transplantation was performed to the inguinal region of the Lewis (RT1^l ) recipients under cyclosporine A monotherapy (16 mg/kg) protocol tapered to 2 mg/kg and maintained for the duration of the study. The peripheral blood chimerism levels (T-cell, B-cell, and monocyte/granulocyte/dendritic cell-MGDC populations) were evaluated at days 7, 14, 35, 63, 100, and 150 posttransplant by flow cytometry. At Day 150, thymus, spleen, and liver samples were assessed by polymerase chain reaction (PCR) in the presence of DSC.

RESULTS

Total chimerism level increased in both OMCST and OMCS groups at all time points. At 150 days posttransplant, chimerism in OMCST group was significantly higher (12.91 ± 0.16%) than that in OMCS group (8.89 ± 0.53%%, p < .01), and PCR confirmed the presence of donor-derived cells in the liver and spleen of all OMCST recipients and in one liver sample and two spleen samples in OMCS recipients without thymus transplant.

CONCLUSIONS

This study confirmed the direct effects of thymus transplantation on the induction and maintenance of DSC in T-cell, B-cell, and MGDC populations. These results confirm correlation between thymus transplantation and DSC induction.

Creation of Dystrophin Expressing Chimeric Cells of Myoblast Origin as a Novel Stem Cell Based Therapy for Duchenne Muscular Dystrophy

Over the past decade different stem cell (SC) based approaches were tested to treat Duchenne Muscular Dystrophy (DMD), a lethal X-linked disorder caused by mutations in dystrophin gene. Despite research efforts, there is no curative therapy for DMD. Allogeneic SC therapies aim to restore dystrophin in the affected muscles; however, they are challenged by rejection and limited engraftment. Thus, there is a need to develop new more efficacious SC therapies. Chimeric Cells (CC), created via ex vivo fusion of donor and recipient cells, represent a promising therapeutic option for tissue regeneration and Vascularized Composite Allotransplantation (VCA) due to tolerogenic properties that eliminate the need for lifelong immunosuppression. This proof of concept study tested feasibility of myoblast fusion for Dystrophin Expressing. Chimeric Cell (DEC) therapy through in vitro characterization and in vivo assessment of engraftment, survival, and efficacy in the mdx mouse model of DMD. Murine DEC were created via ex vivo fusion of normal (snj) and dystrophin–deficient (mdx) myoblasts using polyethylene glycol. Efficacy of myoblast fusion was confirmed by flow cytometry and dystrophin immunostaining, while proliferative and myogenic differentiation capacity of DEC were assessed in vitro. Therapeutic effect after DEC transplant (0.5 × 10⁶) into the gastrocnemius muscle (GM) of mdx mice was assessed by muscle functional tests. At 30 days post-transplant dystrophin expression in GM of injected mdx mice increased to 37.27 ± 12.1% and correlated with improvement of muscle strength and function. Our study confirmed feasibility and efficacy of DEC therapy and represents a novel SC based approach for treatment of muscular dystrophies.

Dystrophin Expressing Chimeric (DEC) Human Cells Provide a Potential Therapy for Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a progressive and lethal disease caused by mutations of the dystrophin gene. Currently no cure exists. Stem cell therapies targeting DMD are challenged by limited engraftment and rejection despite the use of immunosuppression. There is an urgent need to introduce new stem cell-based therapies that exhibit low allogenic profiles and improved cell engraftment. In this proof-of-concept study, we develop and test a new human stem cell-based approach to increase engraftment, limit rejection, and restore dystrophin expression in the mdx/scid mouse model of DMD. We introduce two Dystrophin Expressing Chimeric (DEC) cell lines created by ex vivo fusion of human myoblasts (MB) derived from two normal donors (MB^N1/MB^N2), and normal and DMD donors (MB^N/MB^DMD). The efficacy of fusion was confirmed by flow cytometry and confocal microscopy based on donor cell fluorescent labeling (PKH26/PKH67). In vitro, DEC displayed phenotype and genotype of donor parent cells, expressed dystrophin, and maintained proliferation and myogenic differentiation. In vivo, local delivery of both DEC lines (0.5 × 10⁶) restored dystrophin expression (17.27%±8.05—MB^N1/MB^N2 and 23.79%±3.82—MB^N/MB^DMD) which correlated with significant improvement of muscle force, contraction and tolerance to fatigue at 90 days after DEC transplant to the gastrocnemius muscles (GM) of dystrophin-deficient mdx/scid mice. This study establishes DEC as a potential therapy for DMD and other types of muscular dystrophies.

The differentiation of mesenchymal stem cells to vascular cells regulated by the HMGB1/RAGE axis: its application in cell therapy for transplant arteriosclerosis

BACKGROUND

Mesenchymal stem cell (MSC) transplantation shows promise for treating transplant arteriosclerosis, at least partly via promoting endothelial regeneration. However, the efficacy and safety are still under investigation especially regarding recent findings that neointimal smooth muscle cells are derived from MSC-like cells. The high mobility group box 1 (HMGB1)/receptor for advanced glycation end-product (RAGE) axis is involved in regulating proliferation, migration, and differentiation of MSCs, and therefore it can be presumably applied to improve the outcome of cell therapy. The aim of the current study was to investigate this hypothesis.

METHODS

Rat MSCs were treated with HMGB1 or modified with HMGB1 vectors to activate the HMGB1/RAGE axis. RAGE was targeted and inhibited by specific short hairpin RNA vectors. We assessed the capacity for cell proliferation, migration, and differentiation after vector transfection in vitro and in a rat model of transplant arteriosclerosis. The expression of CD31 and α-smooth muscle actin (αSMA) was determined to evaluate the differentiation of MSCs to endothelial cells and smooth muscle cells.

RESULTS

Exogenous HMGB1 treatment and transfection with HMGB1 vectors promoted MSC migration and vascular endothelial growth factor (VEGF)-induced differentiation to CD31+ cells while inhibiting their proliferation and platelet-derived growth factor (PDGF)-induced differentiation to αSMA+ cells. Such an effect was blocked by RAGE knockdown. HMGB1-modified cells preferably migrated to graft neointima and differentiated to CD31+ cells along with significant relief of transplant arteriosclerosis and inhibition of HMGB1 and RAGE expression in graft vessels. RAGE knockdown inhibited cell migration to graft vessels.

CONCLUSIONS

HMGB1 stimulated MSCs to migrate and differentiate to endothelial cells via RAGE signaling, which we translated to successful application in cell therapy for transplant arteriosclerosis.

The miracle of face transplantation after 10 years

INTRODUCTION

At the 10th year anniversary of the first face transplantation, there are currently 36 patients worldwide, who are the recipients of faces coming from human donors.

AREAS OF AGREEMENT

Despite the initial debates and ethical concerns, face transplantation became a clinical reality with satisfactory functional outcomes.

AREAS OF CONTROVERSY

The areas of controversy still include the impact of lifelong immunosuppression on otherwise healthy patients as well as the selection process of face transplant candidates.

GROWING POINTS

Other concerns include financial support for this new generation of transplants as well as social reintegration and patients return to work after face transplantation.

AREAS TIMELY FOR DEVELOPING RESEARCH

Based on over 20 years of research experience in the field of vascularized composite allotransplantation, and clinical experience as a leading surgeon of the US first face transplantation, this review will summarize the well-known facts as well as unexpected outcomes and challenges of face transplantation.

Bone marrow chimerism as a strategy to produce tolerance in solid organ allotransplantation

PURPOSE OF REVIEW

Clinical transplant tolerance has been most successfully achieved combining hematopoietic chimerism with kidney transplantation. This review outlines this strategy in animal models and human transplantation, and possible clinical challenges.

RECENT FINDINGS

Kidney transplant tolerance has been achieved through chimerism in several centers beginning with Massachusetts General Hospital's success with mixed chimerism in human leukocyte antigen (HLA)-mismatched patients and the Stanford group with HLA-matched patients, and the more recent success of the Northwestern protocol achieving full chimerism. This has challenged the original view that stable mixed chimerism is necessary for organ graft tolerance. However, among the HLA-mismatched kidney transplant-tolerant patients, loss of mixed chimerism does not lead to renal-graft rejection, and the development of host Foxp3+ regulatory T cells has been observed. Recent animal models suggest that graft tolerance through bone marrow chimerism occurs through both clonal deletion and regulatory immune cells. Further, Tregs have been shown to improve chimerism in animal models.

SUMMARY

Animal studies continue to suggest ways to improve our current clinical strategies. Advances in chimerism protocols suggest that tolerance may be clinically achievable with relative safety for HLA-mismatched kidney transplants.

Immunomodulatory Role of Mesenchymal Stem Cell Therapy in Vascularized Composite Allotransplantation

This review aims to summarize contemporary evidence of the in vitro and in vivo immunomodulatory effects of mesenchymal stem cells (MSCs) in promoting vascularized composite allotransplant (VCA) tolerance. An extensive literature review was performed to identify pertinent articles of merit. Prospective preclinical trials in mammal subjects receiving VCA (or skin allograft) with administration of MSCs were reviewed. Prospective clinical trials with intravascular delivery of MSCs in human populations undergoing solid organ transplant were also identified and reviewed. Sixteen preclinical studies are included. Eleven studies compared MSC monotherapy to no therapy; of these, ten reported improved graft survival, which was statistically significantly prolonged in eight. Eight studies analyzed allograft survival with MSC therapy as an adjunct to proven immunosuppressive regimens. In these studies, daily immunosuppression was transiently delivered and then stopped. In all studies, treatment-free graft survival was statistically significantly prolonged in animals that received MSC therapy. MSCs have been safely administered clinically and their use in renal transplant clinical trials provides evidence that they improve allograft transplant tolerance in clinical practice. There is potential for MSC induction therapy to overcome many of the obstacles to widespread VCA in clinical practice. Preclinical studies are needed before MSC-induced VCA tolerance becomes a clinical reality.