A double blind randomized placebo controlled phase I/II study assessing the safety and efficacy of allogeneic bone marrow derived mesenchymal stem cell in critical limb ischemia

Safety and biodistribution study of bone marrow-derived mesenchymal stromal cells and mononuclear cells and the impact of the administration route in an intact porcine model

BACKGROUND AIMS

Bone marrow mononuclear cells (BM-MNCs) and bone marrow-derived mesenchymal stem stromal cells (BM-MSCs) could have therapeutic potential for numerous conditions, including ischemia-related injury. Cells transplanted intravascularly may become entrapped in the lungs, which potentially decreases their therapeutic effect and increases the risk for embolism.

METHODS

Twelve pigs were divided into groups of 3 and received (99m)Tc- hydroxymethyl-propylene-amine-oxime-labeled autologous BM-MNCs or allogeneic BM-MSCs by either intravenous (IV) or intra-arterial (IA) transplantation. A whole body scan and single photon emission computed tomography/computed tomography (SPECT/CT) were performed 8 h later, and tissue biopsies were collected for gamma counting. A helical CT scan was also performed on 4 pigs to detect possible pulmonary embolism, 2 after IV BM-MSC injection and 2 after saline injection.

RESULTS

The transplantation route had a greater impact on the biodistribution of the BM-MSCs than the BM-MNCs. The BM-MNCs accumulated in the spleen and bones, irrespective of the administration route. The BM-MSCs had relatively higher uptake in the kidneys. The IA transplantation decreased the deposition of BM-MSCs in the lungs and increased uptake in other organs, especially in the liver. Lung atelectases were frequent due to mechanical ventilation and attracted transplanted cells. CT did not reveal any pulmonary embolism.

CONCLUSIONS

Both administration routes were found to be safe, but iatrogenic atelectasis might be an issue when cells accumulate in the lungs. The IA administration is effective in avoiding pulmonary entrapment of BM-MSCs. The cell type and administration method both have a major impact on the acute homing.

Effect of repetitive intra-arterial infusion of bone marrow mononuclear cells in patients with no-option limb ischemia: the randomized, double-blind, placebo-controlled Rejuvenating Endothelial Progenitor Cells via Transcutaneous Intra-arterial Supplementation (JUVENTAS) trial

BACKGROUND

Patients with severe limb ischemia may not be eligible for conventional therapeutic interventions. Pioneering clinical trials suggest that bone marrow-derived cell therapy enhances neovascularization, improves tissue perfusion, and prevents amputation. The objective of this trial was to determine whether repetitive intra-arterial infusion of bone marrow mononuclear cells (BMMNCs) in patients with severe, nonrevascularizable limb ischemia can prevent major amputation.

METHODS AND RESULTS

The Rejuvenating Endothelial Progenitor Cells via Transcutaneous Intra-arterial Supplementation (JUVENTAS) trial is a randomized, double-blind, placebo-controlled clinical trial in 160 patients with severe, nonrevascularizable limb ischemia. Patients were randomly assigned to repetitive (3 times; 3-week interval) intra-arterial infusion of BMMNC or placebo. No significant differences were observed for the primary outcome, ie, major amputation at 6 months, with major amputation rates of 19% in the BMMNC versus 13% in the placebo group (relative risk, 1.46; 95% confidence interval, 0.62-3.42). The safety outcome (all-cause mortality, occurrence of malignancy, or hospitalization due to infection) was not significantly different between the groups (relative risk, 1.46; 95% confidence interval, 0.63-3.38), neither was all-cause mortality at 6 months with 5% versus 6% (relative risk, 0.78; 95% confidence interval, 0.22-2.80). Secondary outcomes quality of life, rest pain, ankle-brachial index, and transcutaneous oxygen pressure improved during follow-up, but there were no significant differences between the groups.

CONCLUSIONS

Repetitive intra-arterial infusion of autologous BMMNCs into the common femoral artery did not reduce major amputation rates in patients with severe, nonrevascularizable limb ischemia in comparison with placebo. The general improvement in secondary outcomes during follow-up in both the BMMNC and the placebo group, as well, underlines the essential role for placebo-controlled design of future trials.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00371371.

Current Phase II drugs under investigation for the treatment of limb ischemia

INTRODUCTION

More than 20 million people in Europe suffer from peripheral arterial disease and nearly 3% develop critical limb ischemia (CLI). Without any medical treatment, CLI has poor prognosis, resulting in limb loss and high mortality rate. Until today, no systemic drug is available for the treatment of CLI and the gold standard method of treatment includes risk factor modification and open surgical or endovascular revascularization. Endovascular local drug delivery devices and novel antithrombotic agents, currently under investigation, aim to improve outcomes of revascularization procedures. The pioneering concept of therapeutic angiogenesis induced by gene and stem cell therapy has been proposed, in an attempt to increase ischemic tissue perfusion.

AREAS COVERED

This review summarizes local and systemic pharmacological treatment of CLI using endovascular or pharmaco-biological therapy and focuses on Phase II trials available for these drugs.

EXPERT OPINION

Novel endovascular technologies combining angioplasty and local drug-delivery continuously improve and will come to be standard of practice for the management of limb ischemia, while new antithrombotic agents will further improve outcomes. Therapeutic angiogenesis represents a safe and promising treatment option. The combination of revascularization with microcirculation improvement induced by gene or stem cell therapy could enhance limb salvage.

Local intramuscular transplantation of autologous mononuclear cells for critical lower limb ischaemia

BACKGROUND

Peripheral arterial disease is a major health problem, and in about 1% to 2% of patients the disease progresses to critical limb ischaemia (CLI). In a substantial number of patients with CLI, no effective treatment option other than amputation is available and around a quarter of these patients will require a major amputation during the following year. This is an update of the review first published in 2011.

OBJECTIVES

To determine the effectiveness and safety of local intramuscular transplantation of autologous adult bone marrow mononuclear cells (BMMNCs) as a treatment for critical limb ischaemia (CLI).

SEARCH METHODS

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched February 2014) and the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, Issue 1).

SELECTION CRITERIA

We included all randomised controlled trials of CLI in which participants were randomly allocated to intramuscular administration of autologous adult BMMNCs or control (either no intervention or conventional conservative therapy). We excluded studies on patients with intermittent claudication.

DATA COLLECTION AND ANALYSIS

Two authors independently selected trials, assessed trials for eligibility and methodological quality, and extracted data. Disagreements were resolved by consensus or by the third author.

MAIN RESULTS

Only two small studies, with a combined total of 57 participants, met our inclusion criteria and were finally included. They were classified as having a moderate risk of bias with unclear issues regarding their methods, and according to the GRADE approach, the overall quality of the evidence would be considered as moderate. In one study the effects of intramuscular injections of BMMNCs in the ischaemic lower limbs of patients with CLI were compared with control (standard conservative treatment). No deaths were reported and no significant difference was observed between the two groups for either pain (P = 0.37) or the ankle brachial index (ABI) parameter. However, the treatment group showed a significantly smaller proportion of participants undergoing amputation compared with the control group (P = 0.026).In the other study, following subcutaneous injections of granulocyte colony-stimulating factor (G-CSF) for five days, peripheral blood derived mononuclear cells were collected and then transplanted by intramuscular injections into ischaemic lower limbs. The effects were compared with daily intravenous prostaglandin E1 injections (control group). No deaths were reported. Pain reduction was greater in the treatment group than in the control group (P < 0.001) as was increase in ABI (mean increase 0.13 versus 0.02, P < 0.01). The treatment group experienced a statistically significant increase in pain-free walking distance (PFWD) compared with the control group (mean increase 306.4 m versus 78.6 m, P = 0.007). A smaller proportion of participants underwent amputation in the treatment group compared with the control group (0% versus 36%, P = 0.007).

AUTHORS' CONCLUSIONS

The data from the published trials suggest that there is insufficient evidence to support this treatment. These results were based on only two trials which had a very small number of participants. Therefore evidence from larger randomised controlled trials is needed in order to provide adequate statistical power to assess the role of intramuscular mononuclear cell implantation in patients with CLI.

Imaging techniques to evaluate cell therapy in peripheral artery disease: state of the art and clinical trials

Cell-based therapies, as potential approach to cure peripheral artery disease (PAD), have been clinically investigated after promising results in preclinical models. The so far published studies are very heterogeneous, as different cell sources, cell types, amounts of administered cells and delivering strategies have been used. Overall, cell therapies for PAD bring about a general improvement of patient's clinical condition, even though conclusions cannot be established due to the small size and non-randomized design of these trials. In this context, non-invasive imaging techniques, aimed to monitor angiogenesis and neovascularization after cell therapy, will help the follow-up of clinical studies. However, still much work is needed to establish advanced imaging procedure to overcome the limitation of the current techniques and to accumulate more data in large populations of patients. Here, we report the main imaging techniques employed to evaluate the outcome of the different cell-based therapies in PAD. Moreover, we focus on both published and ongoing clinical trials utilizing cell therapy in PAD.

Mesenchymal Stem Cell Paracrine Factors in Vascular Repair and Regeneration

Mesenchymal stem cell therapy show great optimism in the treatment of several diseases. MSCs are attractive candidates for cell therapy because of easy isolation, high expansion potential giving unlimited pool of transplantable cells, low immunogenicity, amenability to ex vivo genetic modification, and multipotency. The stem cells orchestrate the repair process by various mechanisms such as transdifferentiation, cell fusion, microvesicles or exosomes and most importantly by secreting paracrine factors. The MSCs release several angiogenic, mitogenic, anti-apoptotic, anti-inflammatory and anti-oxidative factors that play fundamental role in regulating tissue repair in various vascular and cardiac diseases. The therapeutic release of these factors by the cells can be enhanced by several strategies like genetic modification, physiological and pharmacological preconditioning, improved cell culture and selection methods, and biomaterial based approaches. The current review describes the impact of paracrine factors released by MSCs on vascular repair and regeneration in myocardial infarction, restenosis and peripheral artery disease, and the various strategies adopted to enhance the release of these paracrine factors to enhance organ function.

Natural history of mesenchymal stem cells, from vessel walls to culture vessels

Mesenchymal stem/stromal cells (MSCs) can regenerate tissues by direct differentiation or indirectly by stimulating angiogenesis, limiting inflammation, and recruiting tissue-specific progenitor cells. MSCs emerge and multiply in long-term cultures of total cells from the bone marrow or multiple other organs. Such a derivation in vitro is simple and convenient, hence popular, but has long precluded understanding of the native identity, tissue distribution, frequency, and natural role of MSCs, which have been defined and validated exclusively in terms of surface marker expression and developmental potential in culture into bone, cartilage, and fat. Such simple, widely accepted criteria uniformly typify MSCs, even though some differences in potential exist, depending on tissue sources. Combined immunohistochemistry, flow cytometry, and cell culture have allowed tracking the artifactual cultured mesenchymal stem/stromal cells back to perivascular anatomical regions. Presently, both pericytes enveloping microvessels and adventitial cells surrounding larger arteries and veins have been described as possible MSC forerunners. While such a vascular association would explain why MSCs have been isolated from virtually all tissues tested, the origin of the MSCs grown from umbilical cord blood remains unknown. In fact, most aspects of the biology of perivascular MSCs are still obscure, from the emergence of these cells in the embryo to the molecular control of their activity in adult tissues. Such dark areas have not compromised intents to use these cells in clinical settings though, in which purified perivascular cells already exhibit decisive advantages over conventional MSCs, including purity, thorough characterization and, principally, total independence from in vitro culture. A growing body of experimental data is currently paving the way to the medical usage of autologous sorted perivascular cells for indications in which MSCs have been previously contemplated or actually used, such as bone regeneration and cardiovascular tissue repair.

Airway transplantation

No definitive solution has been discovered for replacing long segments or the entire trachea in humans. Most of this challenge stems from the specific function and mechanics that are almost impossible to replicate except in the setting of an allotransplantation, which requires lifelong immunosuppressive medication. Recently, tissue engineering provided significant evidence concerning the next promising therapeutic alternative for tracheal replacement. Underlying mechanism and pathways of cell-surface interactions, cell migration, and differentiation are essential to understand the complexity of tracheal tissue regeneration. Tracheal replacement remains challenging but initial steps toward an ideal therapeutic concept have been made.

Isolation, expansion and characterization of bone marrow-derived mesenchymal stromal cells in serum-free conditions

Bone marrow-derived mesenchymal stromal cells (BM-MSCs) heralded a new beginning for regenerative medicine and generated tremendous interest as the most promising source for therapeutic application. Most cell therapies require stringent regulatory compliance and prefer the use of serum-free media (SFM) or xeno-free media (XFM) for the MSC production process, starting from the isolation onwards. Here, we report on serum-free isolation and expansion of MSCs and compare them with cells grown in conventional fetal bovine serum (FBS)-containing media as a control. The isolation, proliferation and morphology analysis demonstrated significant differences between MSCs cultured in various SFM/XFM in addition to their difference with FBS controls. BD Mosaic™ Mesenchymal Stem Cell Serum-Free media (BD-SFM) and Mesencult-XF (MSX) supported the isolation, sequential passaging, tri-lineage differentiation potential and acceptable surface marker expression profile of BM-MSCs. Further, MSCs cultured in SFM showed higher immune suppression and hypo-immunogenicity properties, making them an ideal candidate for allogeneic cell therapy. Although cells cultured in control media have a significantly higher proliferation rate, BM-MSCs cultured in BD-SFM or MSX media are the preferred choice to meet regulatory requirements as they do not contain bovine serum. While BM-MSCs cultured in BD-SFM and MSX media adhered to all MSC characteristics, in the case of few parameters, the performance of cells cultured in BD-SFM was superior to that of MSX media. Pre-clinical safety and efficiency studies are required before qualifying SFM or XFM media-derived MSCs for therapeutic applications.

Mesenchymal stromal cells for the treatment of critical limb ischemia: context and perspective

Cell therapy using mesenchymal stromal cells (MSCs) is a promising new avenue of treatment for critical limb ischemia (CLI). Preclinical studies have suggested that MSCs enhance neovascularization in ischemic limbs. In this commentary, we discuss a recent study by Gupta and colleagues, one of the first human trials using allogeneic MSCs for CLI, in relation to the current state of knowledge regarding cell therapy for CLI.