PACE: randomized, controlled, multicentre, multinational, phase III study of PLX-PAD for critical limb ischaemia in patients unsuitable for revascularization: randomized clinical trial.

BACKGROUND: Revascularization is the primary treatment modality for chronic limb-threatening ischaemia (CLTI), but is not feasible in all patients. PLX-PAD is an off-the-shelf, placental-derived, mesenchymal stromal cell-like cell therapy. This study aimed to evaluate whether PLX-PAD would increase amputation-free survival in people with CLTI who were not candidates for revascularization. METHODS: People with CLTI and minor tissue loss (Rutherford 5) who were unsuitable for revascularization were entered into a randomized, parallel-group, placebo-controlled, multinational, blinded, trial, in which PLX-PAD was compared with placebo (2 : 1 randomization), with 30 intramuscular injections (0.5 ml each) into the index leg on days 0 and 60. Planned follow-up was 12-36 months, and included vital status, amputations, lesion size, pain and quality-of-life assessments, haemodynamic parameters, and adverse events. RESULTS: Of 213 patients enrolled, 143 were randomized to PLX-PAD and 70 to placebo. Demographics and baseline characteristics were balanced. Most patients were Caucasian (96.2%), male (76.1%), and ambulatory (85.9%). Most patients (76.6%) reported at least one adverse event, which were mostly expected events in CLTI, such as skin ulcer or gangrene. The probability of major amputation or death was similar for placebo and PLX-PAD (33 and 28.6% respectively; HR 0.93, 95% c.i. 0.53 to 1.63; P = 0.788). Revascularization and complete wound healing rates were similar in the two groups. A post hoc analysis of a subpopulation of 121 patients with a baseline haemoglobin A1c level below 6.5% showed improved 12-month amputation-free survival (HR 0.46, 0.21 to 0.99; P = 0.048). CONCLUSION: Although there was no evidence that PLX-PAD reduced amputation-free survival in the entire study population, benefit was observed in patients without diabetes mellitus or whose diabetes was well controlled; this requires confirmation in further studies. Trial registration: NCT03006770 (http://www.clinicaltrials.gov); 2015-005532-18 (EudraCT Clinical Trials register - Search for 2015-005532-18).

PLX-PAD Cell Treatment of Critical Limb Ischaemia: Rationale and Design of the PACE Trial.

BACKGROUND: Critical limb ischaemia (CLI) is a life threatening condition with a considerable risk of major amputation and death. Besides revascularisation, no treatment has been proven to reduce the risks. Therapeutic angiogenesis by gene or cell therapy has not demonstrated definitive evidence in randomised controlled trials. PLX-PAD is an "off the shelf" allogeneic placental derived, mesenchymal like cell therapy, which, in preclinical studies, has shown pro-angiogenic, anti-inflammatory, and regenerative properties. Favourable one year amputation free survival (AFS), and trends in reduction of pain scores and increase of tissue perfusion have been shown in two small, open label, phase I trials. METHODS: The PACE study is a phase III randomised, double blind, multicentre, multinational placebo controlled, parallel group study to evaluate the efficacy, tolerability, and safety of intramuscular injections of PLX-PAD cells to treat patients with atherosclerotic CLI with minor tissue loss (Rutherford Category 5) up to the ankle level, who are unsuitable for revascularisation or carry an unfavourable risk benefit for that treatment. The study will enroll 246 patients, who after screening are randomised in a ratio of 2:1 to treatment with intramuscular injections of PLX-PAD 300 × 106 cells or placebo on two occasions, eight weeks apart. The primary efficacy endpoint is time to major amputation or death (amputation free survival), which will be assessed in follow up of at least 12 months and up to 36 months. CONCLUSIONS: Based on favourable pre-clinical and initial clinical study results, the PACE phase III randomised controlled trial will evaluate placenta derived PLX-PAD cell treatment in patients with critical limb ischaemia, with an unfavourable risk benefit for revascularisation. Clinicaltrials.gov: NCT03006770.

Placenta-derived PLX-PAD mesenchymal-like stromal cells are efficacious in rescuing blood flow in hind limb ischemia mouse model by a dose- and site-dependent mechanism of action.

BACKGROUND: In peripheral artery disease (PAD), blockage of the blood supply to the limbs, most frequently the legs, leads to impaired blood flow and tissue ischemia. Pluristem's PLX-PAD cells are placenta-derived mesenchymal stromal-like cells currently in clinical trials for the treatment of peripheral artery diseases. METHODS: In this work, the hind limb ischemia (HLI) mouse model was utilized to study the efficacy and mechanism of action of PLX-PAD cells. ELISA assays were performed to characterize and quantitate PLX-PAD secretions in vitro. RESULTS: PLX-PAD cells administered intramuscularly rescued blood flow to the lower limb after HLI induction in a dose-dependent manner. While rescue of blood flow was site-dependent, numerous administration regimes enabled rescue of blood flow, indicating a systemic effect mediated by PLX-PAD secretions. Live PLX-PAD cells were more efficacious than cell lysate in rescuing blood flow, indicating the importance of prolonged cytokine secretion for maximal blood flow recovery. In vitro studies showed a multifactorial secretion profile including numerous pro-angiogenic proteins; these are likely involved in the PLX-PAD mechanism of action. DISCUSSION: Live PLX-PAD cells were efficacious in rescuing blood flow after the induction of HLI in the mouse model in a dose- and site-dependent manner. The fact that various administration routes of PLX-PAD rescued blood flow indicates that the mechanism of action likely involves one of systemic secretions which promote angiogenesis. Taken together, the data support the further clinical testing of PLX-PAD cells for PAD indications.

Human placental eXpanded (PLX) mesenchymal-like adherent stromal cells confer neuroprotection to nerve growth factor (NGF)-differentiated PC12 cells exposed to ischemia by secretion of IL-6 and VEGF.

Mesenchymal stem cells are potent candidates in stroke therapy due to their ability to secrete protective anti-inflammatory cytokines and growth factors. We investigated the neuroprotective effects of human placental mesenchymal-like adherent stromal cells (PLX) using an established ischemic model of nerve growth factor (NGF)-differentiated pheochromocytoma PC12 cells exposed to oxygen and glucose deprivation (OGD) followed by reperfusion. Under optimal conditions, 2 × 105 PLX cells, added in a trans-well system, conferred 30-60% neuroprotection to PC12 cells subjected to ischemic insult. PC12 cell death, measured by LDH release, was reduced by PLX cells or by conditioned medium derived from PLX cells exposed to ischemia, suggesting the active release of factorial components. Since neuroprotection is a prominent function of the cytokine IL-6 and the angiogenic factor VEGF165, we measured their secretion using selective ELISA of the cells under ischemic or normoxic conditions. IL-6 and VEGF165 secretion by co-culture of PC12 and PLX cells was significantly higher under ischemic compared to normoxic conditions. Exogenous supplementation of 10 ng/ml each of IL-6 and VEGF165 to insulted PC12 cells conferred neuroprotection, reminiscent of the neuroprotective effect of PLX cells or their conditioned medium. Growth factors as well as co-culture conditioned medium effects were reduced by 70% and 20% upon pretreatment with 240 ng/ml Semaxanib (anti VEGF165) and/or 400 ng/ml neutralizing anti IL-6 antibody, respectively. Therefore, PLX-induced neuroprotection in ischemic PC12 cells may be partially explained by IL-6 and VEGF165 secretion. These findings may also account for the therapeutic effects seen in clinical trials after treatment with these cells.

Human placenta-derived stromal cells decrease inflammation, placental injury and blood pressure in hypertensive pregnant mice.

Pre-eclampsia, the development of hypertension and proteinuria or end-organ damage during pregnancy, is a leading cause of both maternal and fetal morbidity and mortality, and there are no effective clinical treatments for pre-eclampsia aside from delivery. The development of pre-eclampsia is characterized by maladaptation of the maternal immune system, excessive inflammation and endothelial dysfunction. We have reported that detection of extracellular RNA by the Toll-like receptors (TLRs) 3 and 7 is a key initiating signal that contributes to the development of pre-eclampsia. PLacental eXpanded (PLX-PAD) cells are human placenta-derived, mesenchymal-like, adherent stromal cells that have anti-inflammatory, proangiogenic, cytoprotective and regenerative properties, secondary to paracrine secretion of various molecules in response to environmental stimulation. We hypothesized that PLX-PAD cells would reduce the associated inflammation and tissue damage and lower blood pressure in mice with pre-eclampsia induced by TLR3 or TLR7 activation. Injection of PLX-PAD cells on gestational day 14 significantly decreased systolic blood pressure by day 17 in TLR3-induced and TLR7-induced hypertensive mice (TLR3 144-111 mmHg; TLR7 145-106 mmHg; both P<0.05), and also normalized their elevated urinary protein:creatinine ratios (TLR3 5.68-3.72; TLR7 5.57-3.84; both P<0.05). On gestational day 17, aortic endothelium-dependent relaxation responses improved significantly in TLR3-induced and TLR7-induced hypertensive mice that received PLX-PAD cells on gestational day 14 (TLR3 35-65%; TLR7 37-63%; both P<0.05). In addition, markers of systemic inflammation and placental injury, increased markedly in both groups of TLR-induced hypertensive mice, were reduced by PLX-PAD cells. Importantly, PLX-PAD cell therapy had no effects on these measures in pregnant control mice or on the fetuses. These data demonstrate that PLX-PAD cell therapy can safely reverse pre-eclampsia-like features during pregnancy and have a potential therapeutic role in pre-eclampsia treatment.

HIPGEN: a randomized, multicentre phase III study using intramuscular PLacenta-eXpanded stromal cells therapy for recovery following hip fracture arthroplasty : a study design.

AIMS: The aim of the HIPGEN consortium is to develop the first cell therapy product for hip fracture patients using PLacental-eXpanded (PLX-PAD) stromal cells. METHODS: HIPGEN is a multicentre, multinational, randomized, double-blind, placebo-controlled trial. A total of 240 patients aged 60 to 90 years with low-energy femoral neck fractures (FNF) will be allocated to two arms and receive an intramuscular injection of either 150 × 106 PLX-PAD cells or placebo into the medial gluteal muscle after direct lateral implantation of total or hemi hip arthroplasty. Patients will be followed for two years. The primary endpoint is the Short Physical Performance Battery (SPPB) at week 26. Secondary and exploratory endpoints include morphological parameters (lean body mass), functional parameters (abduction and handgrip strength, symmetry in gait, weightbearing), all-cause mortality rate and patient-reported outcome measures (Lower Limb Measure, EuroQol five-dimension questionnaire). Immunological biomarker and in vitro studies will be performed to analyze the PLX-PAD mechanism of action. A sample size of 240 subjects was calculated providing 88% power for the detection of a 1 SPPB point treatment effect for a two-sided test with an α level of 5%. CONCLUSION: The HIPGEN study assesses the efficacy, safety, and tolerability of intramuscular PLX-PAD administration for the treatment of muscle injury following arthroplasty for hip fracture. It is the first phase III study to investigate the effect of an allogeneic cell therapy on improved mobilization after hip fracture, an aspect which is in sore need of addressing for the improvement in standard of care treatment for patients with FNF. Cite this article: Bone Jt Open 2022;3(4):340-347.

Pre-Administration of PLX-R18 Cells Protects Mice from Radiation-Induced Hematopoietic Failure and Lethality.

Acute Radiation Syndrome (ARS) is a syndrome involving damage to multiple organs caused by exposure to a high dose of ionizing radiation over a short period of time; even low doses of radiation damage the radiosensitive hematopoietic system and causes H-ARS. PLacenta eXpanded (PLX)-R18 is a 3D-expanded placenta-derived stromal cell product designated for the treatment of hematological disorders. These cells have been shown in vitro to secrete hematopoietic proteins, to stimulate colony formation, and to induce bone marrow migration. Previous studies in mice showed that PLX-R18 cells responded to radiation-induced hematopoietic failure by transiently secreting hematopoiesis related proteins to enhance reconstitution of the hematopoietic system. We assessed the potential effect of prophylactic PLX-R18 treatment on H-ARS. PLX-R18 cells were administered intramuscularly to C57BL/6 mice, −1 and 3 days after (LD70/30) total body irradiation. PLX R18 treatment significantly increased survival after irradiation (p < 0.0005). In addition, peripheral blood and bone marrow (BM) cellularity were monitored at several time points up to 30 days. PLX-R18 treatment significantly increased the number of colony-forming hematopoietic progenitors in the femoral BM and significantly raised peripheral blood cellularity. PLX-R18 administration attenuated biomarkers of bone marrow aplasia (EPO, FLT3L), sepsis (SAA), and systemic inflammation (sP-selectin and E-selectin) and attenuated radiation-induced inflammatory cytokines/chemokines and growth factors, including G-CSF, MIP-1a, MIP-1b, IL-2, IL-6 and MCP-1, In addition, PLX-R18 also ameliorated radiation-induced upregulation of pAKT. Taken together, prophylactic PLX-R18 administration may serve as a protection measure, mitigating bone marrow failure symptoms and systemic inflammation in the H-ARS model.

Intramuscular and intratendinous placenta-derived mesenchymal stromal-like cell treatment of a chronic quadriceps tendon rupture.

BACKGROUND: Quadriceps tendon ruptures (QTRs) are rare but debilitating injuries, often associated with chronic metabolic conditions or long-term steroid treatment. While the surgical treatment for acute QTRs is described thoroughly, no common strategy exists for the often frustrating treatment of chronic, reoccurring QTRs. The pro-angiogenic and immunomodulatory properties of placenta-derived adherent mesenchymal stromal-like (PLX-PAD) cells have been described to protect musculoskeletal tissues from inflammation and catabolic cytokine migration, yet little is known about the regenerative potential of PLX-PAD cells in repetitively damaged tendon tissue. CASE: We report the case of an 80-year-old male patient with a chronic three-time QTR of his right knee. The quadriceps tendon was reconstructed applying a conventional suture anchor repair procedure combined with a synthetic mesh augmentation and additional intramuscular and intratendineous PLX-PAD cell injections as an individualized treatment approach. No adverse events were reported, and excellent radiological and functional outcomes with a passive range of motion of 0/0/120° knee extension-flexion were observed at the 12 month follow-up. Gait analysis confirmed restoration of joint motion, including gait speed, deficit in step length, and knee extensor muscle strength (pre-surgery: 0.98 m/s, 40 cm, 42.4 ± 12.4 N; 9 months post-surgery: 1.07 m/s, 0 cm, 10.4 ± 18.9 N) as well as hyperextension throughout stance and late swing phases (pre-surgery: -11.2 ± 0.9°; 9 months post-surgery: -2.7 ± 1.6°). Postoperative lymphocyte and cytokine analyses from the patient's peripheral blood serum suggested a systemic short-term immunoregulatory reaction with postoperatively increased interleukin (IL)-6 (pre-surgery: 0.79 pg/mL; day 1: 139.97 pg/mL; day 5: 5.58 pg/mL; 9 months: 1.76 pg/mL) and IL-10 (pre-surgery: 0.9 pg/mL; day 1: 1.21 pg/ mL; day 5: 0.3 pg/mL; 9 months: 0.34 pg/mL) levels that decreased again over time. CONCLUSIONS: Herein, we demonstrate a successfully treated chronic QTR with a synergistic surgical and biological reconstructive treatment approach. This local add-on treatment with PLX-PAD cells may be considered in specific cases of chronic QTRs, not susceptible to traditional suture anchor procedures and which exhibit a high risk of treatment failure. Further scientific engagement is warranted to explore underlying immunomodulatory mechanisms of action behind PLX-PAD cell treatment for tendon injuries.

Higher Loading of Gold Nanoparticles in PAD Mesenchymal-like Stromal Cells Leads to a Decreased Exocytosis.

Cell therapy is an important new method in medicine and is being used for the treatment of an increasing number of diseases. The challenge here is the precise tracking of cells in the body and their visualization. One method to visualize cells more easily with current methods is their labeling with nanoparticles before injection. However, for a safe and sufficient cell labeling, the nanoparticles need to remain in the cell and not be exocytosed. Here, we test a glucose-PEG-coated gold nanoparticle for the use of such a cell labeling. To this end, we investigated the nanoparticle exocytosis behavior from PLX-PAD cells, a cell type currently in clinical trials as a potential therapeutic agent. We showed that the amount of exocytosed gold from the cells was influenced by the uptake time and loading amount. This observation will facilitate the safe labeling of cells with nanoparticles in the future and contribute to stem cell therapy research.

Placenta-Derived Mesenchymal-like Adherent Stromal Cells as an Effective Cell Therapy for Cocaine Addiction in a Rat Model.

Recent research points to mesenchymal stem cells' potential for treating neurological disorders, especially drug addiction. We examined the longitudinal effect of placenta-derived mesenchymal stromal-like cells (PLX-PAD) in a rat model for cocaine addiction. Sprague-Dawley male rats were trained to self-administer cocaine or saline daily until stable maintenance. Before the extinction phase, PLX-PAD cells were administered by intracerebroventricular or intranasal routes. Neurogenesis was evaluated, as was behavioral monitoring for craving. We labeled the PLX-PAD cells with gold nanoparticles and followed their longitudinal migration in the brain parallel to their infiltration of essential peripheral organs both by micro-CT and by inductively coupled plasma-optical emission spectrometry. Cell locations in the brain were confirmed by immunohistochemistry. We found that PLX-PAD cells attenuated cocaine-seeking behavior through their capacity to migrate to specific mesolimbic regions, homed on the parenchyma in the dentate gyrus of the hippocampus, and restored neurogenesis. We believe that intranasal cell therapy is a safe and effective approach to treating addiction and may offer a novel and efficient approach to rehabilitation.

A functional corona around extracellular vesicles enhances angiogenesis, skin regeneration and immunomodulation.

Nanoparticles can acquire a plasma protein corona defining their biological identity. Corona functions were previously considered for cell-derived extracellular vesicles (EVs). Here we demonstrate that nano-sized EVs from therapy-grade human placental-expanded (PLX) stromal cells are surrounded by an imageable and functional protein corona when enriched with permissive technology. Scalable EV separation from cell-secreted soluble factors via tangential flow-filtration (TFF) and subtractive tandem mass-tag (TMT) proteomics revealed significant enrichment of predominantly immunomodulatory and proangiogenic proteins. Western blot, calcein-based flow cytometry, super-resolution and electron microscopy verified EV identity. PLX-EVs partly protected corona proteins from protease digestion. EVs significantly ameliorated human skin regeneration and angiogenesis in vivo, induced differential signalling in immune cells, and dose-dependently inhibited T cell proliferation in vitro. Corona removal by size-exclusion or ultracentrifugation abrogated angiogenesis. Re-establishing an artificial corona by cloaking EVs with fluorescent albumin as a model protein or defined proangiogenic factors was depicted by super-resolution microscopy, electron microscopy and zeta-potential shift, and served as a proof-of-concept. Understanding EV corona formation will improve rational EV-inspired nano-therapy design.

Placenta-Expanded Stromal Cell Therapy in a Rodent Model of Simulated Weightlessness.

Long duration spaceflight poses potential health risks to astronauts during flight and re-adaptation after return to Earth. There is an emerging need for NASA to provide successful and reliable therapeutics for long duration missions when capability for medical intervention will be limited. Clinically relevant, human placenta-derived therapeutic stromal cells (PLX-PAD) are a promising therapeutic alternative. We found that treatment of adult female mice with PLX-PAD near the onset of simulated weightlessness by hindlimb unloading (HU, 30 d) was well-tolerated and partially mitigated decrements caused by HU. Specifically, PLX-PAD treatment rescued HU-induced thymic atrophy, and mitigated HU-induced changes in percentages of circulating neutrophils, but did not rescue changes in the percentages of lymphocytes, monocytes, natural killer (NK) cells, T-cells and splenic atrophy. Further, PLX-PAD partially mitigated HU effects on the expression of select cytokines in the hippocampus. In contrast, PLX-PAD failed to protect bone and muscle from HU-induced effects, suggesting that the mechanisms which regulate the structure of these mechanosensitive tissues in response to disuse are discrete from those that regulate the immune- and central nervous system (CNS). These findings support the therapeutic potential of placenta-derived stromal cells for select physiological deficits during simulated spaceflight. Multiple countermeasures are likely needed for comprehensive protection from the deleterious effects of prolonged spaceflight.

RESTORE Survey on the Public Perception of Advanced Therapies and ATMPs in Europe-Why the European Union Should Invest More!

Advanced therapy medicinal products (ATMPs) are potential game changers in modern medical care with an anticipated major impact for patients and society. They are a new drug class often referred to as "living drugs," and are based on complex components such as vectors, cells and even tissues. The production of such ATMPs involves innovative biotechnological methods. In this survey, we have assessed the perception of European citizens regarding ATMPs and health care in Europe, in relation to other important topics, such as safety and security, data protection, climate friendly energy supply, migration, and others. A crucial question was to determine to what extent European citizens wish to support public funding of innovations in healthcare and reimbursement strategies for ATMPs. To answer this, we conducted an online survey in 13 European countries (representative of 85.3% of the entire EU population including the UK in 2020), surveying a total of 7,062 European citizens. The survey was representative with respect to adult age groups and gender in each country. Healthcare had the highest ranking among important societal topics. We found that 83% of the surveyed EU citizens were in support of more public funding of technologies in the field of ATMPs. Interestingly, 74% of respondents are in support of cross-border healthcare for patients with rare diseases to receive ATMP treatments and 61% support the reimbursement of very expensive ATMPs within the European health care system despite the current lack of long-term efficacy data. In conclusion, healthcare is a top ranking issue for European Citizens, who additionally support funding of new technologies to enable the wider application of ATMPs in Europe.

Perinatal Cells: A Promising COVID-19 Therapy?

The COVID-19 pandemic has become a priority in the health systems of all nations worldwide. In fact, there are currently no specific drugs or preventive treatments such as vaccines. The numerous therapies available today aim to counteract the symptoms caused by the viral infection that in some subjects can evolve causing acute respiratory distress syndromes (ARDS) with consequent admission to intensive care unit. The exacerbated response of the immune system, through cytokine storm, causes extensive damage to the lung tissue, with the formation of edema, fibrotic tissues and susceptibility to opportunistic infections. The inflammatory picture is also aggravated by disseminated intravascular coagulation which worsens the damage not only to the respiratory system, but also to other organs. In this context, perinatal cells represent a valid strategy thanks to their strong immunomodulatory potential, their safety profile, the ability to reduce fibrosis and stimulate reparative processes. Furthermore, perinatal cells exert antibacterial and antiviral actions. This review therefore provides an overview of the characteristics of perinatal cells with a particular focus on the beneficial effects that they could have in patients with COVID-19, and more specifically for their potential use in the treatment of ARDS and sepsis.

Mesenchymal Stromal Cells from Fetal and Maternal Placenta Possess Key Similarities and Differences: Potential Implications for Their Applications in Regenerative Medicine.

Placenta-derived mesenchymal stromal cells (MSC) have attracted more attention for their immune modulatory properties and poor immunogenicity, which makes them suitable for allogeneic transplantation. Although MSC isolated from different areas of the placenta share several features, they also present significant biological differences, which might point to distinct clinical applications. Hence, we compared cells from full term placenta distinguishing them on the basis of their origin, either maternal or fetal. We used cells developed by Pluristem LTD: PLacenta expanded mesenchymal-like adherent stromal cells (PLX), maternal-derived cells (PLX-PAD), fetal-derived cells (PLX-R18), and amniotic membrane-derived MSC (hAMSC). We compared immune modulatory properties evaluating effects on T-lymphocyte proliferation, expression of cytotoxicity markers, T-helper and T-regulatory cell polarization, and monocyte differentiation toward antigen presenting cells (APC). Furthermore, we investigated cell immunogenicity. We show that MSCs and MSC-like cells from both fetal and maternal sources present immune modulatory properties versus lymphoid (T cells) and myeloid (APC) cells, whereby fetal-derived cells (PLX-R18 and hAMSC) have a stronger capacity to modulate immune cell proliferation and differentiation. Our results emphasize the importance of understanding the cell origin and characteristics in order to obtain a desired result, such as modulation of the inflammatory response that is critical in fostering regenerative processes.

Placenta-Derived Cell Therapy to Treat Patients With Respiratory Failure Due to Coronavirus Disease 2019.

OBJECTIVES: To determine whether placental cell therapy PLacental eXpanded (PLX)-PAD (Pluristem Therapeutics, Haifa, Israel) may be beneficial to treating critically ill patients suffering from acute respiratory distress syndrome due to coronavirus disease 2019. DESIGN: Retrospective case report of critically ill coronavirus disease 2019 patients treated with PLacental eXpanded (PLX)-PAD from March 26, 2020, to April 4, 2020, with follow-up through May 2, 2020. SETTING: Four hospitals in Israel (Rambam Health Care Campus, Bnai Zion Medical Center, and Samson Assuta Ashdod University Hospital), and Holy Name Medical Center in New Jersey. PATIENTS: Eight critically ill patients on invasive mechanical ventilation, suffering from acute respiratory distress syndrome due to coronavirus disease 2019. INTERVENTIONS: Intramuscular injection of PLacental eXpanded (PLX)-PAD (300 × 106 cells) given as one to two treatments. MEASUREMENTS AND MAIN RESULTS: Mortality, time to discharge, and changes in blood and respiratory variables were monitored during hospitalization to day 17 posttreatment. Of the eight patients treated (median age 55 yr, seven males and one female), five were discharged, two remained hospitalized, and one died. By day 3 postinjection, mean C-reactive protein fell 45% (240.3-131.3 mg/L; p = 0.0019) and fell to 77% by day 5 (56.0 mg/L; p < 0.0001). Pao2/Fio2 improved in 5:8 patients after 24-hour posttreatment, with similar effects 48-hour posttreatment. A decrease in positive end-expiratory pressure and increase in pH were statistically significant between days 0 and 14 (p = 0.0032 and p = 0.00072, respectively). A decrease in hemoglobin was statistically significant for days 0-5 and 0-14 (p = 0.015 and p = 0.0028, respectively), whereas for creatinine, it was statistically significant between days 0 and 14 (p = 0.032). CONCLUSIONS: Improvement in several variables such as C-reactive protein, positive end-expiratory pressure, and Pao2/Fio2 was observed following PLacental eXpanded (PLX)-PAD treatment, suggesting possible therapeutic effect. However, interpretation of the data is limited due to the small sample size, use of concomitant investigational therapies, and the uncontrolled study design. The efficacy of PLacental eXpanded (PLX)-PAD in coronavirus disease 2019 should be further evaluated in a controlled clinical trial.

The role of placental-derived adherent stromal cell (PLX-PAD) in the treatment of critical limb ischemia.

BACKGROUND AIMS: Mesenchymal stromal cells (MSC) are spindle-shaped plastic-adherent cells isolated from bone marrow (BM), adipose tissue and other organs, including the placenta. Autologous BM-derived MSC have been studied in animals with experimentally induced critical limb ischemia (CLI) as a model of end-stage peripheral vascular disease. While demonstrating therapeutic benefit, the use of these cells is limited by the need to surgically extract BM and the fear of thrombosis secondary to the use of granulocyte-colony-stimulating factor (G-CSF) to mobilize the cells. METHODS: We studied the use of placental-derived adherent stromal cells (ASC) in a standard limb ischemia model of male Balb/c mice. These placental-derived cells, termed PLX-PAD, share the adherence and marker expression of BM-derived MSC but lack their differentiation potential. PLX-PAD are isolated from human placenta following a Caesarean section and cultured in a bioreactor, termed the PluriX System. The PluriX System provides a three-dimensional (3-D) microenvironment that enables the large-scale growth of these cells. PLX-PAD are stable adhesive cells that can be expanded in vitro without the loss of phenotype and without showing signs of karyotypic changes. RESULTS: The intramuscular (i.m.) administration of PLX-PAD in our model significantly improved blood flow (BF) (P=0.0008), increased capillary density (P=0.021), reduced oxidative stress (P=0.034) and reduced endothelial damage (P=0.004), while increasing limb function versus the administration of a phosphate-buffered saline (PBS) control vehicle in the affected limb. CONCLUSIONS: Allogeneic placental-derived ASC may provide an off-the-shelf supply of therapeutic cells that would need no histocompatible tissue matching and be potentially less expensive and considerably more convenient than BM or adipose-derived MSC.

Placenta-Derived Adherent Stromal Cell Therapy for Hematopoietic Disorders: A Case Study of PLX-R18.

The ephemeral placenta provides a noncontroversial source of young, healthy cells of both maternal and fetal origin from which cell therapy products can be manufactured. The 2 advantages of using live cells as therapeutic entities are: (a) in their environmental-responsive, multifactorial secretion profile and (b) in their activity as a "slow-release drug delivery system," releasing secretions over a long time frame. A major difficulty in translating cell therapy to the clinic involves challenges of large-scale, robust manufacturing while maintaining product characteristics, identity, and efficacy. To address these concerns early on, Pluristem developed the PLacental eXpanded (PLX) platform, the first good manufacturing practice-approved, 3-dimensional bioreactor-based cell growth platform, to enable culture of mesenchymal-like adherent stromal cells harvested from the postpartum placenta. One of the products produced by Pluristem on this platform is PLX-R18, a product mainly comprising placental fetal cells, which is proven in vivo to alleviate radiation-induced lethality and to enhance hematopoietic cell counts after bone marrow (BM) failure. The identified mechanism of action of PLX-R18 cells is one of the cell-derived systemic pro-hematopoietic secretions, which upregulate endogenous secretions and subsequently rescue BM and peripheral blood cellularity, thereby boosting survival. PLX-R18 is therefore currently under study to treat both the hematopoietic syndrome of acute radiation (under the US Food and Drug Administration [FDA]'s Animal Rule) and the incomplete engraftment after BM transplantation (in a phase I study). In the future, they could potentially address additional hematological indications, such as aplastic anemia, myelodysplastic syndrome, primary graft failure, and acute or chronic graft versus host disease.

Human Placental-Derived Adherent Stromal Cells Co-Induced with TNF-α and IFN-γ Inhibit Triple-Negative Breast Cancer in Nude Mouse Xenograft Models.

Culturing 3D-expanded human placental-derived adherent stromal cells (ASCs) in the presence of tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) transiently upregulated the secretion of numerous anti-proliferative, anti-angiogenic and pro-inflammatory cytokines. In a 3D-spheroid screening assay, conditioned medium from these induced-ASCs inhibited proliferation of cancer cell lines, including triple-negative breast cancer (TNBC) lines. In vitro co-culture studies of induced-ASCs with MDA-MB-231 human breast carcinoma cells, a model representing TNBC, supports a mechanism involving immunomodulation and angiogenesis inhibition. In vivo studies in nude mice showed that intramuscular administration of induced-ASCs halted MDA-MB-231 cell proliferation, and inhibited tumor progression and vascularization. Thirty percent of treated mice experienced complete tumor remission. Murine serum concentrations of the tumor-supporting cytokines Interleukin-6 (IL-6), Vascular endothelial growth factor (VEGF) and Granulocyte-colony stimulating factor (G-CSF) were lowered to naïve levels. A somatic mutation analysis identified numerous genes which could be screened in patients to increase a positive therapeutic outcome. Taken together, these results show that targeted changes in the secretion profile of ASCs may improve their therapeutic potential.

Posttransplant Intramuscular Injection of PLX-R18 Mesenchymal-Like Adherent Stromal Cells Improves Human Hematopoietic Engraftment in A Murine Transplant Model.

Late-term complications of hematopoietic cell transplantation (HCT) are numerous and include incomplete engraftment. One possible mechanism of incomplete engraftment after HCT is cytokine-mediated suppression or dysfunction of the bone marrow microenvironment. Mesenchymal stromal cells (MSCs) elaborate cytokines that nurture or stimulate the marrow microenvironment by several mechanisms. We hypothesize that the administration of exogenous MSCs may modulate the bone marrow milieu and improve peripheral blood count recovery in the setting of incomplete engraftment. In the current study, we demonstrated that posttransplant intramuscular administration of human placental derived mesenchymal-like adherent stromal cells [PLacental eXpanded (PLX)-R18] harvested from a three-dimensional in vitro culture system improved posttransplant engraftment of human immune compartment in an immune-deficient murine transplantation model. As measured by the percentage of CD45+ cell recovery, we observed improvement in the peripheral blood counts at weeks 6 (8.4 vs. 24.1%, p < 0.001) and 8 (7.3 vs. 13.1%, p < 0.05) and in the bone marrow at week 8 (28 vs. 40.0%, p < 0.01) in the PLX-R18 cohort. As measured by percentage of CD19+ cell recovery, there was improvement at weeks 6 (12.6 vs. 3.8%) and 8 (10.1 vs. 4.1%). These results suggest that PLX-R18 may have a therapeutic role in improving incomplete engraftment after HCT.