Characteristics and Immunomodulating Functions of Adipose-Derived and Bone Marrow-Derived Mesenchymal Stem Cells Across Defined Human Leukocyte Antigen Barriers

Background

Vascularized composite allotransplantation opens new possibilities in reconstructive transplantation such as hand or face transplants. Lifelong immunosuppression and its side-effects are the main drawbacks of this procedure. Mesenchymal stem cells (MSCs) have clinically useful immunomodulatory effects and may be able to reduce the burden of chronic immunosuppression. Herein, we assess and compare characteristics and immunomodulatory capacities of bone marrow- and adipose tissue-derived MSCs isolated from the same human individual across defined human leukocyte antigen (HLA) barriers.

Materials and methods

Samples of omental (o.) adipose tissue, subcutaneous (s.c.) adipose tissue, and bone marrow aspirate from 10 human organ donors were retrieved and MSCs isolated. Cells were characterized by flow cytometry and differentiated in three lineages: adipogenic, osteogenic, and chondrogenic. In mixed lymphocyte reactions, the ability of adipose-derived mesenchymal stem cells (ASCs) and bone marrow-derived mesenchymal stem cells (BMSCs) to suppress the immune response was assessed and compared within individual donors. HLA mismatched or mitogen stimulations were analyzed in co-culture with different MSC concentrations. Supernatants were analyzed for cytokine contents.

Results

All cell types, s.c.ASC, o.ASC, and BMSC demonstrated individual differentiation potential and cell surface markers. Immunomodulating effects were dependent on dose and cell passage. Proliferation of responder cells was most effectively suppressed by s.c.ASCs and combination with BMSC resulted in highly efficient immunomodulation. Immunomodulation was not cell contact-dependent and cells demonstrated a specific cytokine secretion.

Conclusion

When human ASCs and BMSCs are isolated from the same individual, both show effective immunomodulation across defined HLA barriers in vitro. We demonstrate a synergistic effect when cells from the same biologic system were combined. This cell contact-independent function underlines the potential of clinical systemic application of MSCs.

Mycophenolic Acid for Topical Immunosuppression in Vascularized Composite Allotransplantation: Optimizing Formulation and Preliminary Evaluation of Bioavailability and Pharmacokinetics

Mycophenolic acid (MPA), is the active form of the ester prodrug mycophenolate mofetil (MMF). MMF is an FDA approved immunosuppressive drug that has been successfully used in systemic therapy in combination with other agents for the prevention of acute rejection (AR) following solid organ transplantation (SOT) as well as in vascularized composite allotransplantation (VCA). Systemic use of MMF is associated with gastrointestinal adverse effects. Topical delivery of the prodrug could thus provide graft-targeted immunosuppression while minimizing systemic drug exposure. Our goal was to develop a topical formulation of MPA with optimal in vitro/in vivo characteristics such as release, permeation, and tissue bioavailability to enable safety and efficacy evaluation in clinical VCA.

Permeation studies were performed with a solution of MPA (10 mg/ml). In vitro release and permeation studies were performed for different semisolid formulations (Aladerm, Lipoderm, emollient, and VersaBase) of MPA (1% w/w) using a Franz Diffusion Cell System (FDCS). In vivo pharmacokinetic characterization of MPA release from Lipoderm was performed in rats.

MPA in solution exhibited a steady state flux (3.8 ± 0.1 µg/cm²/h) and permeability (1.1 × 10⁻⁷ ± 3.2 × 10⁻⁹ cm/s). MPA in Lipoderm exhibited a steady state flux of 1.12 ± 0.24 µg/cm²/h, and permeability of 6.2 × 10⁻⁰⁹ ± 1.3 × 10⁻⁹ cm/s across the biomimetic membrane. The cumulative release of MPA from Lipoderm, showed a linear single-phase profile with a R² of 0.969. In vivo studies with MPA in Lipoderm showed markedly higher local tissue MPA levels and lower systemic MPA exposure as compared to values obtained after intravenous delivery of the same dose of drug (p < 0.05).

We successfully developed for the first time, a topical formulation of MPA in Lipoderm with optimal in vitro/in vivo permeability characteristics and no undesirable local or systemic adverse effects in vivo. Our study provides key preliminary groundwork for translational efficacy studies of topical MPA in pre-clinical large animal VCA models and for effectiveness evaluation in patients receiving VCA.

An Elastomeric Polymer Matrix, PEUU-Tac, Delivers Bioactive Tacrolimus Transdurally to the CNS in Rat

Central nervous system (CNS) neurons fail to regrow injured axons, often resulting in permanently lost neurologic function. Tacrolimus is an FDA-approved immunosuppressive drug with known neuroprotective and neuroregenerative properties in the CNS. However, tacrolimus is typically administered systemically and blood levels required to effectively treat CNS injuries can lead to lethal, off-target organ toxicity. Thus, delivering tacrolimus locally to CNS tissues may provide therapeutic control over tacrolimus levels in CNS tissues while minimizing off-target toxicity. Herein we show an electrospun poly(ester urethane) urea and tacrolimus elastomeric matrix (PEUU-Tac) can deliver tacrolimus trans-durally to CNS tissues. In an acute CNS ischemia model in rat, the optic nerve (ON) was clamped for 10s and then PEUU-Tac was used as an ON wrap and sutured around the injury site. Tacrolimus was detected in PEUU-Tac wrapped ONs at 24 h and 14 days, without significant increases in tacrolimus blood levels. Similar to systemically administered tacrolimus, PEUU-Tac locally decreased glial fibrillary acidic protein (GFAP) at the injury site and increased growth associated protein-43 (GAP-43) expression in ischemic ONs from the globe to the chiasm, consistent with decreased astrogliosis and increased retinal ganglion cell (RGC) axon growth signaling pathways. These initial results suggest PEUU-Tac is a biocompatible elastic matrix that delivers bioactive tacrolimus trans-durally to CNS tissues without significantly increasing tacrolimus blood levels and off-target toxicity.

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PEUU-Tac locally delivers tacrolimus to CNS tissues

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PEUU-Tac positively modulates CNS tissue remodeling

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PEUU-Tac minimizes off-target tacrolimus toxicity

Central nervous system (CNS) injury typically results in permanently lost neurological function. Tacrolimus is an FDA-approved drug used during organ transplantation that also has CNS neuroprotective and neuroregenerative properties. However, tacrolimus is typically delivered systemically in the blood and delivering effective concentrations to CNS tissues requires tacrolimus blood levels that can lead to adverse side effects in multiple organs. Herein we show that PEUU-Tac, a tacrolimus-eluting matrix, can locally deliver tacrolimus to injured CNS tissues without increasing blood levels, suggesting PEUU-Tac can be used to treat CNS injuries locally while minimizing adverse side effects.

Anesthesia and Perioperative Care in Reconstructive Transplantation

Reconstructive transplantation of vascularized composite allografts (VCAs), such as upper extremity, craniofacial, abdominal, lower extremity, or genitourinary transplants, has emerged as a cutting-edge specialty, with more than 50 programs in the United States and 30 programs across the world performing these procedures. Most VCAs involve complicated technical planning and preparation, protracted surgery, and complex immunosuppressive or immunomodulatory protocols, each associated with unique anesthesiology challenges. This article outlines key procedural, patient, and protocol-related aspects of VCA relevant to anesthesiology management with the goal of ensuring patient safety and optimizing surgical, immunologic, and functional outcomes.

Peripheral Nerve Nanoimaging: Monitoring Treatment and Regeneration

Accidental and iatrogenic trauma are major causes of peripheral nerve injury. Healing after nerve injury is complex and often incomplete, which can lead to acute or chronic pain and functional impairment. Current assessment methods for nerve regeneration lack sensitivity and objectivity. There is a need for reliable and reproducible, noninvasive strategies with adequate spatial and temporal resolution for longitudinal evaluation of degeneration or regeneration after injury/treatment. Methods for noninvasive monitoring of the efficacy and effectiveness of neurotherapeutics in nerve regeneration or of neuropathic pain are needed to ensure adequacy and responsiveness to management, especially given the large variability in the patient populations, etiologies, and complexity of nerve injuries. Surrogate biomarkers are needed with positive predictive correlation for the dynamics and kinetics of neuroregeneration. They can provide direct real-time insight into the efficacy and mechanisms of individualized therapeutic intervention. Here, we review the state-of-the-art tools, technologies, and therapies in peripheral nerve injury and regeneration as well as provide perspectives for the future. We present compelling evidence that advancements in nanomedicine and innovation in nanotechnology such as nanotheranostics hold groundbreaking potential as paradigm shifts in noninvasive peripheral nerve imaging and drug delivery. Nanotechnology, which revolutionized molecular imaging in cancer and inflammatory disease, can be used to delineate dynamic molecular imaging signatures of neuroinflammation and neuroregeneration while simultaneously monitoring cellular or tissue response to drug therapy. We believe that current clinical successes of nanotechnology can and should be adopted and adapted to the science of peripheral nerve injury and regeneration.

Ultra-high field upper extremity peripheral nerve and non-contrast enhanced vascular imaging

OBJECTIVE

The purpose of this study was to explore the efficacy of Ultra-high field [UHF] 7 Tesla [T] MRI as compared to 3T MRI in non-contrast enhanced [nCE] imaging of structural anatomy in the elbow, forearm, and hand [upper extremity].

MATERIALS AND METHOD

A wide range of sequences including T1 weighted [T1] volumetric interpolate breath-hold exam [VIBE], T2 weighted [T2] double-echo steady state [DESS], susceptibility weighted imaging [SWI], time-of-flight [TOF], diffusion tensor imaging [DTI], and diffusion spectrum imaging [DSI] were optimized and incorporated with a radiofrequency [RF] coil system composed of a transverse electromagnetic [TEM] transmit coil combined with an 8-channel receive-only array for 7T upper extremity [UE] imaging. In addition, Siemens optimized protocol/sequences were used on a 3T scanner and the resulting images from T1 VIBE and T2 DESS were compared to that obtained at 7T qualitatively and quantitatively [SWI was only qualitatively compared]. DSI studio was utilized to identify nerves based on analysis of diffusion weighted derived fractional anisotropy images. Images of forearm vasculature were extracted using a paint grow manual segmentation method based on MIPAV [Medical Image Processing, Analysis, and Visualization].

RESULTS

High resolution and high quality signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR]-images of the hand, forearm, and elbow were acquired with nearly homogeneous 7T excitation. Measured [performed on the T1 VIBE and T2 DESS sequences] SNR and CNR values were almost doubled at 7T vs. 3T. Cartilage, synovial fluid and tendon structures could be seen with higher clarity in the 7T T1 and T2 weighted images. SWI allowed high resolution and better quality imaging of large and medium sized arteries and veins, capillary networks and arteriovenous anastomoses at 7T when compared to 3T. 7T diffusion weighted sequence [not performed at 3T] demonstrates that the forearm nerves are clearly delineated by fiber tractography. The proper digital palmar arteries and superficial palmar arch could also be clearly visualized using TOF nCE 7T MRI.

CONCLUSION

Ultra-high resolution neurovascular imaging in upper extremities is possible at 7T without use of renal toxic intravenous contrast. 7T MRI can provide superior peripheral nerve [based on fiber anisotropy and diffusion coefficient parameters derived from diffusion tensor/spectrum imaging] and vascular [nCE MRA and vessel segmentation] imaging.

Blood product utilization in human upper-extremity transplantation: challenges, complications, considerations, and transfusion protocol conception

BACKGROUND

Upper-extremity transplantation (UET) is a reality. Immunologic, functional, and graft survival outcomes have been encouraging. However, these complex reconstructions have unique considerations that pose distinct challenges. Transplant programs have reported morbidity and mortality due to significant intraoperative blood losses, but similar data are scant during other phases of recovery. We report experience from two centers on complete blood component demands and utilization with UET.

STUDY DESIGN AND METHODS

Inpatient medical records of UET recipients from intraoperative (time from initiation of transplant surgery to exit from the operative suite) and postoperative (exit from the operative suite to discharge from the hospital) phases were retrospectively reviewed.

RESULTS

Six patients received various UETs and mean (±SD) postoperative hospital stay was 46 (±14.4) days. Mean (±SD) intraoperative blood unit utilization was 14.8 (±10.2) red blood cells (RBCs), 10.5 (±11.8) plasma, 0.8 (±1.2) platelets (PLTs), and 0.3 (±0.8) cryoprecipitate units. Mean postoperative blood unit utilization was 9.3 (±10.4) RBCs, 5.3 (±6.7) plasma, 1.2 (±2.0) PLTs, and 0.7 (±1.6) cryoprecipitate units. Both intraoperative and postoperative blood utilization for unilateral versus bilateral transplant were different, but not significantly so. However, total inpatient blood use in bilateral transplants was significantly greater than in unilateral transplants.

CONCLUSION

Substantial blood loss may occur in UET and require transfusion of many blood components, primarily RBCs and plasma. We propose an UET transfusion protocol and suggest that centers preparing to perform these transplants should actively engage the transfusion medicine service to ensure availability and access to appropriate blood components for the entire hospitalizations of these unique patients.

Ultra-high-field RF coil development for evaluating upper extremity imaging applications

The purpose of this study is to develop and evaluate a custom-designed 7  T MRI coil and explore its use for upper extremity applications. An RF system composed of a transverse electromagnetic transmit coil and an eight-channel receive-only array was developed for 7  T upper extremity applications. The RF system was characterized and evaluated using scattering parameters and B₁⁺ mapping. Finite difference time domain simulations were performed to evaluate the B₁⁺ field distribution and specific absorption rate for the forearm region of the upper extremity. High-resolution 7  T images were acquired and compared with those at 3 T. The simulation and experimental results show very good B₁⁺ field homogeneity across the forearm. High-resolution images of musculotendinous, osseocartilaginous, and neurovascular structures in the upper extremity are presented with T₁ volumetric interpolated breath-hold examination, T₂ double-echo steady state, T₂ * susceptibility weighted imaging (SWI), diffusion tensor imaging, and time-of-flight sequences. Comparison between 3  T and 7  T is shown. Intricate contextual anatomy can be delineated in synovial, fibrocartilaginous, interosseous, and intraosseous trabecular structures of the forearm, as well as palmar and digital vascular anatomy (including microvascular detail in SWI). Ultra-high-field 7  T imaging holds great potential in improving the sensitivity and specificity of upper extremity imaging, especially in wrist and hand pathology secondary to bone, ligament, nerve, vascular, and other soft or hard tissue etiology.

Biopatterned CTLA4/Fc Matrices Facilitate Local Immunomodulation, Engraftment, and Glucose Homeostasis After Pancreatic Islet Transplantation

Pancreatic islet transplantation (PIT) represents a potential therapy to circumvent the need for exogenous insulin in type 1 diabetes. However, PIT remains limited by lack of donor islets and the need for long-term multidrug immunosuppression to prevent alloimmune islet rejection. Our goal was to evaluate a local immunoregulatory strategy that sustains islet allograft survival and restores glucose homeostasis in the absence of systemic immunosuppression. Nanogram quantities of murine CTLA4/Fc fusion protein were controllably delivered within human acellular dermal matrix scaffolds using an inkjet-based biopatterning technology and cotransplanted with allogeneic islets under the renal capsule to create an immunoregulatory microenvironment around the islet allograft. We achieved long-term engraftment of small loads of allogeneic islet cells with 40% of MHC-mismatched mouse recipients maintaining sustained normoglycemia following pancreatic β-cell ablation by streptozotocin. Biopatterned CTLA4/Fc local therapy was associated with expansion of Foxp3⁺ regulatory T cells and shifts in cytokine production and gene expression from proinflammatory to regulatory profiles, thus substantially benefiting islet allografts survival and function. This study is a new paradigm for targeted therapies in PIT that demonstrates the favorable effects of immune alterations in the transplant milieu and suggests a unique strategy for minimizing systemic immunosuppression and promoting islet allograft survival.

Spontaneous resolution of acute rejection and tolerance induction with IL-2 fusion protein in vascularized composite allotransplantation

Vascularized composite allotransplantation (VCA) has emerged as a treatment option for treating nonlife-threatening conditions. Therefore, in order to make VCA a safe reconstruction option, there is a need to minimize immunosuppression, develop tolerance-inducing strategies and elucidate the mechanisms of VCA rejection and tolerance. In this study we explored the effects of hIL-2/Fc (a long-lasting human IL-2 fusion protein), in combination with antilymphocyte serum (ALS) and short-term cyclosporine A (CsA), on graft survival, regulatory T cell (Treg) proliferation and tolerance induction in a rat hind-limb transplant model. We demonstrate that hIL-2/Fc therapy tips the immune balance, increasing Treg proliferation and suppressing effector T cells, and permits VCA tolerance as demonstrated by long-term allograft survival and donor-antigen acceptance. Moreover, we observe two distinct types of acute rejection (AR), progressive and reversible, within hIL-2/Fc plus ALS and CsA treated recipients. Our study shows differential gene expression profiles of FoxP3 versus GzmB, Prf1 or interferon-γ in these two types of AR, with reversible rejection demonstrating higher Treg to Teff gene expression. This correlation of gene expression profile at the first clinical sign of AR with VCA outcomes can provide the basis for further inquiry into the mechanistic aspects of VCA rejection and future drug targets.

Effects of immunosuppressive drugs on viability and susceptibility of adipose- and bone marrow-derived mesenchymal stem cells

The immunomodulatory potential of cell therapies using adipose-derived stem cells (ASCs) and bone marrow-derived mesenchymal stem cells (BM-MSCs) has been studied in vascularized composite allotransplantation (VCA). Most cell therapy-based experimental and clinical protocols integrate some degree of recipient conditioning/induction with antibodies or other immunosuppressive agents. We investigated the susceptibility of ASCs and BM-MSCs to anti-lymphocyte serum (ALS) and tacrolimus. Rat ASCs and BM-MSCs were exposed to varying concentrations of tacrolimus and ALS in vitro. Serum from ALS-treated animals was added to cell cultures. Viability, susceptibility, and cytotoxicity parameters were evaluated. ALS inhibited ASC and BM-MSC viability and susceptibility in vitro in a dose-dependent manner. ASCs were more susceptible to both ALS and tacrolimus than BM-MSCs. Trypsinized and adherent ASCs were significantly smaller than BM-MSCs. This is the first report on the viability and susceptibility characteristics of BM-MSCs or ASCs to collateral effects of ALS and tacrolimus. These in vitro insights may impact choice of cell type as well as concomitant conditioning agents and the logistical coordination of the timing, dosing, and frequency of drug or cell therapy in solid organ transplantation or VCA protocols.

Biologics and donor bone marrow cells for targeted immunomodulation in vascularized composite allotransplantation: a translational trial in swine

INTRODUCTION

Bone marrow (BM) infusion following organ transplantation is a prerequisite for potential donor-antigen-specific tolerance induction. We developed a preclinical swine model to determine the optimal dose of BM cells to achieve microchimerism. Furthermore, induction therapy was optimized by augmenting the BM infusion with biologics in the form of costimulatory blockade: cytotoxic T-lymphocyte antigen 4 immunoglobulin (CTLA4-Ig).

MATERIALS AND METHODS

Yucatan miniature swine (n = 12) underwent total body and thymic irradiation for cytodepletion. Animal groups received 15, 30, or 60 million cells per kilogram of whole unmodified BM. The optimal dose of BM cell infusion (BMT) was then applied to subsequent experiments evaluating the addition of CTLA4lg. Group 1 (control) received no treatment. Group 2 received FK506 only; group 3 received irradiation, BMT, and FK506; group 4 received FK506 and CTLA4-lg.

RESULTS

Microchimerism was established in all animals after BM cell infusion; at postoperative day 9, it was significantly increased for 60 million cells per kilogram (P = .0001). Transplanted animals in group 1 rejected the allograft 5 to 8 days after transplantation. Group 2 rejected the allograft (skin and muscle) 30 to 32 days after transplantation (2 days after cessation of immunosuppression). Group 3 rejected the skin portion of the allograft at 50, 52, and 53 days posttransplant. Remaining allograft components (muscle, bone, nerve, vessel) survived indefinitely. Group 4 animals demonstrated significantly prolonged muscle survival beyond 150 days posttransplant; the skin component survived past 150 days in two of three animals. Skin and muscle histology in all long-term surviving animals were normal.

CONCLUSIONS

BM cell infusion with 60 million cells per kilogram results in stable levels of microchimerism. The addition of costimulatory blockade (CTLA4lg) prolonged allograft skin survival and overall graft survival. Such targeted immunomodulatory protocols might facilitate immune tolerance and eliminate the need for multidrug immunosuppression to maintain graft survival after vascularized composite allotransplantation.

Vascularized osteomyocutaneous allografts are permissive to tolerance by induction-based immunomodulatory therapy

Vascularized composite allografts (VCAs) are unique among transplanted organs in that they are composed of multiple tissues with disparate antigenic and immunologic properties. As the predominant indications for VCAs are non-life-threatening conditions, there is an immediate need to develop tolerance induction strategies and to elucidate the mechanisms of VCA rejection and tolerance using VCA-specific animal models. In this study, we explore the effects of in vitro induced donor antigen-specific CD4(-) CD8(-) double negative (DN) Treg-based therapy, in a fully MHC mismatched mouse VCA such as a vascularized osteomyocutaneous as compared to a non-VCA such as a full thickness skin (FTS) transplantation model to elucidate the unique features of VCA rejection and tolerance. We demonstrate that combined therapy with antigen-induced CD4 derived DN Tregs and a short course of anti-lymphocyte serum, rapamycin and IL-2/Fc fusion protein results in donor-specific tolerance to VCA, but not FTS allografts. Macrochimerism was detected in VCA but not FTS allograft recipients up to >60 days after transplantation. Moreover, a significant increase of CD4(+) Foxp3(+) Tregs was found in the peripheral blood of tolerant VCA recipients. These data suggest that VCA are permissive to tolerance induced by DN Treg-based induction therapy.

Perspectives on the use of mesenchymal stem cells in vascularized composite allotransplantation

Reconstructive transplantation has emerged as clinical reality over the past decade. Long-term graft acceptance has been feasible in extremity and facial vascularized composite allotransplantation (VCA) under standard immunosuppression. Minimizing overall burden of lifelong immunosuppression is key to wider application of these non-life saving grafts. Allograft tolerance is the holy grail of many cell-based immunomodulatory strategies. Recent protocols using mesenchymal stem cells from bone marrow and adipose tissue offer promise and potential in VCA. This article provides an overview of the experimental basis, the scientific background and clinical applications of stem cell-based therapies in the field of reconstructive allotransplantation.

Anesthetic management in upper extremity transplantation: the Pittsburgh experience

BACKGROUND

Hand/forearm/arm transplants are vascularized composite allografts, which, unlike solid organs, are composed of multiple tissues including skin, muscle, tendons, vessels, nerves, lymph nodes, bone, and bone marrow. Over the past decade, 26 upper extremity transplantations were performed in the United States. The University of Pittsburgh Medical Center has the largest single center experience with 8 hand/forearm transplantations performed in 5 recipients between January 2008 and September 2010. Anesthetic management in the emerging field of upper extremity transplants must address protocol and procedure-specific considerations related to the role of regional blocks, effects of immunosuppressive drugs during transplant surgery, fluid and hemodynamic management in the microsurgical setting, and rigorous intraoperative monitoring during these often protracted procedures.

METHODS

For the first time, we outline salient aspects of upper extremity transplant anesthesia based on our experience with 5 patients. We highlight the importance of minimizing intraoperative vasopressors and improving fluid management and blood product use.

RESULTS

Our approach reduced the incidence of perioperative bleeding requiring re-exploration or hemostasis and shortened in-hospital and intensive care unit stay. Functional, immunologic and graft survival outcomes have been highly encouraging in all patients.

CONCLUSIONS

Further experience is required for validation or standardization of specific anesthetic protocols. Meanwhile, our recommendations are intended as pertinent guidelines for centers performing these novel procedures.

Clinical implementation of a procedure to prepare bone marrow cells from cadaveric vertebral bodies

AIMS

Vertebral bone marrow is a rich and easily accessible source of hematopoietic and mesenchymal stem cells that has been used to promote chimerism and transplantation tolerance in connection with cadaveric organ transplantation. The purpose of this study is to provide a detailed account of the procedure used to prepare the first five vertebral bone marrow products for infusion in conjunction with the first hand/hand-forelimb transplants performed at the University of Pittsburgh (PA, USA).

MATERIALS & METHODS

The cell separation and release testing were performed at the University of Pittsburgh Cancer Institute's Hematopoietic Stem Cell Laboratory, a Good Manufacturing Practice-compliant facility accredited for clinical cell processing by the Foundation for Accreditation of Cellular Therapy (FACT) and for clinical flow cytometry by the College of American Pathologists (CAP).

Favoring the risk-benefit balance for upper extremity transplantation--the Pittsburgh Protocol

Upper extremity transplantation is an innovative reconstructive strategy with potential of immediate clinical application and the most near-term pay-off for select amputees, allowing reintegration into employment and society. Routine applicability and widespread impact of such strategies for the upper extremity amputees with devastating limb loss could be enabled by implementation of cellular therapies that integrate and unify the concepts of transplant tolerance induction with those of reconstructive transplantation. Such therapies offer the promise of minimizing the risks, maximizing the benefits and optimizing outcomes of these innovative procedures.

Surgical and technical aspects of hand transplantation: is it just another replant?

The ultimate goal of hand allotransplantation is to achieve graft survival and useful long-term function. To achieve these goals, selection of the appropriate patient, detailed preoperative planning, and precise surgical technique are of paramount importance. Transplantation should be reserved for motivated consenting adults in good general heath, who are psychologically stable and have failed a trial of prosthetic use. While the key surgical steps of transplantation are similar to those of replantation, there are major differences. This article describes the steps in hand allotransplantation, and the importance of patient selection as well as preoperative and postoperative care.

Acute and chronic rejection in upper extremity transplantation: what have we learned?

To date, 78 upper extremity transplants have been performed in 55 recipients around the world. The purpose of this article is to provide an overview of acute and chronic rejection (CR) and to summarize collective insights in upper extremity transplantation. To date, almost all patients experienced AR that is pathophysiologically similar to that in solid organs. The spectre of chronic rejection is just emerging. Upper extremity transplantation has significant potential as a reconstructive option only if efforts are invested in strategies to reduce risks of prolonged immunosuppression and in approaches to better diagnose, monitor and treat AR and CR.

Development and validation of a procedure to isolate viable bone marrow cells from the vertebrae of cadaveric organ donors for composite organ grafting

BACKGROUND AIMS

Donor-derived vertebral bone marrow (BM) has been proposed to promote chimerism in solid organ transplantation with cadaveric organs. Reports of successful weaning from immunosuppression in patients receiving directed donor transplants in combination with donor BM or blood cells and novel peri-transplant immunosuppression has renewed interest in implementing similar protocols with cadaveric organs.

METHODS

We performed six pre-clinical full-scale separations to adapt vertebral BM preparations to a good manufacturing practice (GMP) environment. Vertebral bodies L4-T8 were transported to a class 10 000 clean room, cleaned of soft tissue, divided and crushed in a prototype bone grinder. Bone fragments were irrigated with medium containing saline, albumin, DNAse and gentamicin, and strained through stainless steel sieves. Additional cells were eluted after two rounds of agitation using a prototype BM tumbler.

RESULTS

The majority of recovered cells (70.9 ± 14.1%, mean ± SD) were eluted directly from the crushed bone, whereas 22.3% and 5.9% were eluted after the first and second rounds of tumbling, respectively. Cells were pooled and filtered (500, 200 μm) using a BM collection kit. Larger lumbar vertebrae yielded about 1.6 times the cells of thoracic vertebrae. The average product yielded 5.2 ± 1.2 × 10(10) total cells, 6.2 ± 2.2 × 10(8) of which were CD45(+) CD34(+). Viability was 96.6 ± 1.9% and 99.1 ± 0.8%, respectively. Multicolor flow cytometry revealed distinct populations of CD34(+) CD90(+) CD117(dim) hematopoietic stem cells (15.5 ± 7.5% of the CD34 (+) cells) and CD45(-) CD73(+) CD105(+) mesenchymal stromal cells (0.04 ± 0.04% of the total cells).

CONCLUSIONS

This procedure can be used to prepare clinical-grade cells suitable for use in human allotransplantation in a GMP environment.

The effect of chondroitinase on nerve regeneration following composite tissue allotransplantation

PURPOSE

To improve the degree of functional return and sensibility provided by composite tissue allotransplantation, enhanced nerve regeneration is essential. Chondroitin sulfate proteoglycans are found in the extracellular matrix of nerves and inhibit regenerating axons after injury. Treatment with chondroitinase to remove chondroitin sulfate proteoglycans has been shown to improve nerve regeneration in isolated nerve graft and transection-and-repair models. This study assesses the efficacy of chondroitinase as a neurotherapeutic agent in the setting of composite tissue allotransplantation.

METHODS

Adult Lewis rats received either orthotopic hind limb transplants from Brown Norway rat donors (n = 12) or sciatic nerve transection and repair (n = 6). Following approximation of the sciatic nerve, half the animals received intraneural injections of chondroitinase in saline and the other half received intraneural injections of saline alone. Five weeks after transplantation, we killed the animals and analyzed nerves with nonbiased quantitative nerve histomorphometry. One day after transection and repair, we killed animals and harvested sciatic nerves for immunohistochemical staining of cleaved chondroitin sulfate proteoglycans epitope and laminin. We used unpaired t-tests for statistical analysis.

RESULTS

Distal to the suture line, chondroitinase-treated animals demonstrated statistically greater total number of fibers and nerve density compared with controls. There were no statistically significant differences in fiber number or nerve density proximal to the suture line or in fiber widths. We observed staining of cleaved chondroitin sulfate proteoglycan epitopes only in treated animals, with no differences observed in the degree of laminin staining.

CONCLUSIONS

Intraneural injection of chondroitinase cleaved inhibitory chondroitin sulfate proteoglycans without disrupting proregenerative laminin and resulted in enhanced nerve regeneration after composite tissue allotransplantation. Studies at later time points are needed to assess whether this enhanced nerve regeneration will produce improved functional return.

Hand allotransplantation

In the past decade, more than 100 different composite tissue allotransplantation (CTA) procedures have been performed around the world including more than 50 hand and 8 facial transplants with encouraging graft survival and excellent functional outcomes. Broader clinical application of CTA, however, continues to be hampered by requirement for long-term, high-dose, multidrug maintenance immunosuppression to prevent graft rejection mediated particularly by composite tissue allograft's highly immunogenic skin component. Medication toxicity could result in severe adverse events including metabolic and infectious complications or malignancy. Notably, unlike in solid organs, clinical success is dictated not only by graft acceptance and survival but also by nerve regeneration, which determines ultimate functional outcomes. Novel strategies such as cellular and biologic therapies that integrate the concepts of immune regulation with those of nerve regeneration have shown promising results in small and large animal models. Clinical translation of these insights to reconstructive transplantation and CTA could further minimize the need of immunosuppression and optimize functional outcomes. This will enable wider application of such treatment options for patients in need of complex reconstructive surgery for congenital deformities or devastating injuries that are not amenable to standard methods of repair.

Immunologic aspects and rejection in solid organ versus reconstructive transplantation

The immunosuppressive medications developed over the past 3 decades have paved the way for solid organ transplantation to become the treatment of choice for end-stage organ failure. At the end of the century, composite tissue transplantation in humans was performed with success using the same immunosuppressive medications and therapeutic principles. A decade later, experience from >100 cases of reconstructive transplantation have increased the knowledge, changed the view, and affected the therapeutic principles in this novel field. We herein portray the evolution of this novel type of transplant with particular reference to immunologic aspects, particularly differences between reconstructive and solid organ transplantation.