From Blood to Lesioned Brain: An In Vitro Study on Migration Mechanisms of Human Nasal Olfactory Stem Cells

Pharmacokinetic characteristics of mesenchymal stem cells in translational challenges

Over the past two decades, mesenchymal stem/stromal cell (MSC) therapy has made substantial strides, transitioning from experimental clinical applications to commercial products. MSC therapies hold considerable promise for treating refractory and critical conditions such as acute graft-versus-host disease, amyotrophic lateral sclerosis, and acute respiratory distress syndrome. Despite recent successes in clinical and commercial applications, MSC therapy still faces challenges when used as a commercial product. Current detection methods have limitations, leaving the dynamic biodistribution, persistence in injured tissues, and ultimate fate of MSCs in patients unclear. Clarifying the relationship between the pharmacokinetic characteristics of MSCs and their therapeutic effects is crucial for patient stratification and the formulation of precise therapeutic regimens. Moreover, the development of advanced imaging and tracking technologies is essential to address these clinical challenges. This review provides a comprehensive analysis of the kinetic properties, key regulatory molecules, different fates, and detection methods relevant to MSCs and discusses concerns in evaluating MSC druggability from the perspective of integrating pharmacokinetics and efficacy. A better understanding of these challenges could improve MSC clinical efficacy and speed up the introduction of MSC therapy products to the market.

Transplantation of olfactory mucosa mesenchymal stromal cells repairs spinal cord injury by inducing microglial polarization

STUDY DESIGN

Animal studies OBJECTIVES: To evaluate the therapeutic effect of olfactory mucosa mesenchymal stem cell (OM-MSCs) transplantation in mice with spinal cord injury (SCI) and to explore the mechanism by which OM-MSCs inhibit neuroinflammation and improve SCI.

SETTING

Xiangya Hospital, Central South University; Affiliated Hospital of Guangdong Medical University.

METHODS

Mice (C57BL/6, female, 6-week-old) were randomly divided into sham, SCI, and SCI + OM-MSC groups. The SCI mouse model was generated using Allen's method. OM-MSCs were immediately delivered to the lateral ventricle after SCI using stereotaxic brain injections. One day prior to injury and on days 1, 5, 7, 14, 21, and 28 post-injury, the Basso Mouse Scale and Rivlin inclined plate tests were performed. Inflammation and microglial polarization were evaluated using histological staining, immunofluorescence, and qRT-PCR.

RESULTS

OM-MSCs originating from the neuroectoderm have great potential in the management of SCI owing to their immunomodulatory effects. OM-MSCs administration improved motor function, alleviated inflammation, promoted the transformation of the M1 phenotype of microglia into the M2 phenotype, facilitated axonal regeneration, and relieved spinal cord injury in SCI mice.

CONCLUSIONS

OM-MSCs reduced the level of inflammation in the spinal cord tissue, protected neurons, and repaired spinal cord injury by regulating the M1/M2 polarization of microglia.

Human nasal olfactory stem cells, purified as advanced therapy medicinal products, improve neuronal differentiation

BACKGROUND

Olfactory ecto-mesenchymal stem cells (OE-MSC) are mesenchymal stem cells derived from the lamina propria of the nasal mucosa. They display neurogenic and immunomodulatory properties and were shown to induce recovery in animal models of spinal cord trauma, hearing loss, Parkinsons's disease, amnesia, and peripheral nerve injury. As a step toward clinical practice, we sought to (i) devise a culture protocol that meets the requirements set by human health agencies and (ii) assess the efficacy of stem cells on neuron differentiation.

METHODS

Nasal olfactory mucosa biopsies from three donors were used to design and validate the good manufacturing process for purifying stem cells. All processes and procedures were performed by expert staff from the cell therapy laboratory of the public hospital of Marseille (AP-HM), according to aseptic handling manipulations. Premises, materials and air were kept clean at all times to avoid cross-contamination, accidents, or even fatalities. Purified stem cells were cultivated for 24 or 48 h and conditioned media were collected before being added to the culture medium of the neuroblastoma cell line Neuro2a.

RESULTS

Compared to the explant culture-based protocol, enzymatic digestion provides higher cell numbers more rapidly and is less prone to contamination. The use of platelet lysate in place of fetal calf serum is effective in promoting higher cell proliferation (the percentage of CFU-F progenitors is 15.5%), with the optimal percentage of platelet lysate being 10%. Cultured OE-MSCs do not show chromosomal rearrangement and, as expected, express the usual phenotypic markers of mesenchymal stem cells. When incorporated in standard culture medium, the conditioned medium of purified OE-MSCs promotes cell differentiation of Neuro2a neuroblastoma cells.

CONCLUSION

We developed a safer and more efficient manufacturing process for clinical grade olfactory stem cells. With this protocol, human OE-MSCs will soon be used in a Phase I clinical based on their autologous transplantation in digital nerves with a neglected injury. However, further studies are required to unveil the underlying mechanisms of action.

Human umbilical cord-derived mesenchymal stem cells promote repair of neonatal brain injury caused by hypoxia/ischemia in rats

Administration of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) is believed to be an effective method for treating neurodevelopmental disorders. In this study, we investigated the possibility of hUC-MSCs treatment of neonatal hypoxic/ischemic brain injury associated with maternal immune activation and the underlying mechanism. We established neonatal rat models of hypoxic/ischemic brain injury by exposing pregnant rats to lipopolysaccharide on day 16 or 17 of pregnancy. Rat offspring were intranasally administered hUC-MSCs on postnatal day 14. We found that polypyrimidine tract-binding protein-1 (PTBP-1) participated in the regulation of lipopolysaccharide-induced maternal immune activation, which led to neonatal hypoxic/ischemic brain injury. Intranasal delivery of hUC-MSCs inhibited PTBP-1 expression, alleviated neonatal brain injury-related inflammation, and regulated the number and function of glial fibrillary acidic protein-positive astrocytes, thereby promoting plastic regeneration of neurons and improving brain function. These findings suggest that hUC-MSCs can effectively promote the repair of neonatal hypoxic/ischemic brain injury related to maternal immune activation through inhibition of PTBP-1 expression and astrocyte activation.

Potential Therapeutic Strategies and Substances for Facial Nerve Regeneration Based on Preclinical Studies

Despite advances in microsurgical technology and an improved understanding of nerve regeneration, obtaining satisfactory results after facial nerve injury remains a difficult clinical problem. Among existing peripheral nerve regeneration studies, relatively few have focused on the facial nerve, particularly how experimental studies of the facial nerve using animal models play an essential role in understanding functional outcomes and how such studies can lead to improved axon regeneration after nerve injury. The purpose of this article is to review current perspectives on strategies for applying potential therapeutic methods for facial nerve regeneration. To this end, we searched Embase, PubMed, and the Cochrane library using keywords, and after applying exclusion criteria, obtained a total of 31 qualifying experimental studies. We then summarize the fundamental experimental studies on facial nerve regeneration, highlighting recent bioengineering studies employing various strategies for supporting facial nerve regeneration, including nerve conduits with stem cells, neurotrophic factors, and/or other therapeutics. Our summary of the methods and results of these previous reports reveal a common feature among studies, showing that various neurotrophic factors arising from injured nerves contribute to a microenvironment that plays an important role in functional recovery. In most cases, histological examinations showed that this microenvironmental influence increased axonal diameter as well as myelination thickness. Such an analysis of available research on facial nerve injury and regeneration represents the first step toward future therapeutic strategies.

Syngeneic Transplantation of Rat Olfactory Stem Cells in a Vein Conduit Improves Facial Movements and Reduces Synkinesis after Facial Nerve Injury

BACKGROUND

Posttraumatic facial paralysis is a disabling condition. Current surgical management by faciofacial nerve suture provides limited recovery. To improve the outcome, the authors evaluated an add-on strategy based on a syngeneic transplantation of nasal olfactory stem cells in a rat model of facial nerve injury. The main readouts of the study were the recording of whisking function and buccal synkinesis.

METHODS

Sixty rats were allocated to three groups. Animals with a 2-mm facial nerve loss were repaired with a femoral vein, filled or not with olfactory stem cells. These two groups were compared to similarly injured rats but with a faciofacial nerve suture. Olfactory stem cells were purified from rat olfactory mucosa. Three months after surgery, facial motor performance was evaluated using video-based motion analysis and electromyography. Synkinesis was assessed by electromyography, using measure of buccal involuntary movements during blink reflex, and double retrograde labeling of regenerating motoneurons.

RESULTS

The authors' study reveals that olfactory stem cell transplantation induces functional recovery in comparison to nontransplanted and faciofacial nerve suture groups. They significantly increase (1) maximal amplitude of vibrissae protraction and retraction cycles and (2) angular velocity during protraction of vibrissae. They also reduce buccal synkinesis, according to the two techniques used. However, olfactory stem cell transplantation did not improve axonal regrowth of the facial nerve, 3 months after surgery.

CONCLUSIONS

The authors show here that the adjuvant strategy of syngeneic transplantation of olfactory stem cells improves functional recovery. These promising results open the way for a phase I clinical trial based on the autologous engraftment of olfactory stem cells in patients with a facial nerve paralysis.

Insight into the proteomic profiling of exosomes secreted by human OM-MSCs reveals a new potential therapy

Mesenchymal stromal cells (MSCs) have been used for the treatment of neuronal injury and neurodegenerative diseases. Their underlying mechanism may involve increased secretion of paracrine factors, which promotes tissue repair. Presently, exosomes have been regarded as important components of paracrine secretion and paracrine factors. MSC exosomes represent a promising opportunity to develop novel cell-free therapy approaches. In this study, exosomes from nasal olfactory mucosa MSCs (OM-MSCs) were extracted and purified using ultracentrifugation, resulting in exosome diameters of 40-130 nm. Similar to other exosomes, OM-MSC exosomes were CD63- and CD81-positive and calnexin-negative. Functionally, OM-MSC exosomes promoted human brain microvascular endothelial cell (HBMEC) proliferation and migration. The present study analyzed the OM-MSC exosome paracrine proteome. A total of 304 exosome-associated proteins were identified by LC-MS/MS, including plasminogen activator inhibitor 1 (SERPINE 1), insulin-like growth factor binding protein family members (IGFBP 4 and 5), epidermal growth factor receptor (EGFR), neurogenic locus notch homolog protein 2 (NOTCH 2), apolipoprotein E (APOE), and heat shock protein HSP90-beta (HSP90AB1). These molecules are known to be important in neurotrophic, angiogenesis, cell growth, differentiation, apoptosis, and inflammation and are highly correlated with the mechanism of tissue repair and neural restoration. These observations may provide a basis for further evaluation of OM-MSC exosome potential as a novel therapeutic modality.

Immediate or Delayed Transplantation of a Vein Conduit Filled with Nasal Olfactory Stem Cells Improves Locomotion and Axogenesis in Rats after a Peroneal Nerve Loss of Substance

Over the recent years, several methods have been experienced to repair injured peripheral nerves. Among investigated strategies, the use of natural or synthetic conduits was validated for clinical application. In this study, we assessed the therapeutic potential of vein guides, transplanted immediately or two weeks after a peroneal nerve injury and filled with olfactory ecto-mesenchymal stem cells (OEMSC). Rats were randomly allocated to five groups. A3 mm peroneal nerve loss was bridged, acutely or chronically, with a 1 cm long femoral vein and with/without OEMSCs. These four groups were compared to unoperated rats (Control group). OEMSCs were purified from male olfactory mucosae and grafted into female hosts. Three months after surgery, nerve repair was analyzed by measuring locomotor function, mechanical muscle properties, muscle mass, axon number, and myelination. We observed that stem cells significantly (i) increased locomotor recovery, (ii) partially maintained the contractile phenotype of the target muscle, and (iii) augmented the number of growing axons. OEMSCs remained in the nerve and did not migrate in other organs. These results open the way for a phase I/IIa clinical trial based on the autologous engraftment of OEMSCs in patients with a nerve injury, especially those with neglected wounds.

Pharmacological Transdifferentiation of Human Nasal Olfactory Stem Cells into Dopaminergic Neurons

The discovery of novel drugs for neurodegenerative diseases has been a real challenge over the last decades. The development of patient- and/or disease-specific in vitro models represents a powerful strategy for the development and validation of lead candidates in preclinical settings. The implementation of a reliable platform modeling dopaminergic neurons will be an asset in the study of dopamine-associated pathologies such as Parkinson's disease. Disease models based on cell reprogramming strategies, using either human-induced pluripotent stem cells or transcription factor-mediated transdifferentiation, are among the most investigated strategies. However, multipotent adult stem cells remain of high interest to devise direct conversion protocols and establish in vitro models that could bypass certain limitations associated with reprogramming strategies. Here, we report the development of a six-step chemically defined protocol that drives the transdifferentiation of human nasal olfactory stem cells into dopaminergic neurons. Morphological changes were progressively accompanied by modifications matching transcript and protein dopaminergic signatures such as LIM homeobox transcription factor 1 alpha (LMX1A), LMX1B, and tyrosine hydroxylase (TH) expression, within 42 days of differentiation. Phenotypic changes were confirmed by the production of dopamine from differentiated neurons. This new strategy paves the way to develop more disease-relevant models by establishing reprogramming-free patient-specific dopaminergic cell models for drug screening and/or target validation for neurodegenerative diseases.

Rational use of mesenchymal stem cells in the treatment of autism spectrum disorders

Autism and autism spectrum disorders (ASD) refer to a range of conditions characterized by impaired social and communication skills and repetitive behaviors caused by different combinations of genetic and environmental influences. Although the pathophysiology underlying ASD is still unclear, recent evidence suggests that immune dysregulation and neuroinflammation play a role in the etiology of ASD. In particular, there is direct evidence supporting a role for maternal immune activation during prenatal life in neurodevelopmental conditions. Currently, the available options of behavioral therapies and pharmacological and supportive nutritional treatments in ASD are only symptomatic. Given the disturbing rise in the incidence of ASD, and the fact that there is no effective pharmacological therapy for ASD, there is an urgent need for new therapeutic options. Mesenchymal stem cells (MSCs) possess immunomodulatory properties that make them relevant to several diseases associated with inflammation and tissue damage. The paracrine regenerative mechanisms of MSCs are also suggested to be therapeutically beneficial for ASD. Thus the underlying pathology in ASD, including immune system dysregulation and inflammation, represent potential targets for MSC therapy. This review will focus on immune dysfunction in the pathogenesis of ASD and will further discuss the therapeutic potential for MSCs in mediating ASD-related immunological disorders.

Grafts of Olfactory Stem Cells Restore Breathing and Motor Functions after Rat Spinal Cord Injury

The transplantation of olfactory ecto-mesenchymal stem cells (OEMSCs) could be a helpful therapeutic strategy for spinal cord repair. Using an acute rat model of high cervical contusion that provokes a persistent hemidiaphragmatic and foreleg paralysis, we evaluated the therapeutic effect of a delayed syngeneic transplantation (two days post-contusion) of OEMSCs within the injured spinal cord. Respiratory function was assessed using diaphragmatic electromyography and neuroelectrophysiological recordings of phrenic nerves (innervating the diaphragm). Locomotor function was evaluated using the ladder-walking locomotor test. Cellular reorganization in the injured area was also studied using immunohistochemical and microscopic techniques. We report a substantial improvement in breathing movements, in activities of the ipsilateral phrenic nerve and ipsilateral diaphragm, and also in locomotor abilities four months post-transplantation with nasal OEMSCs. Moreover, in the grafted spinal cord, axonal disorganization and inflammation were reduced. Some grafted stem cells adopted a neuronal phenotype, and axonal sparing was observed in the injury site. The therapeutic effect on the supraspinal command is presumably because of both neuronal replacements and beneficial paracrine effects on the injury area. Our study provides evidence that nasal OEMSCs could be a first step in clinical application, particularly in patients with reduced breathing/locomotor movements.

Isolation and characterization of olfactory ecto-mesenchymal stem cells from eight mammalian genera

BACKGROUND

Stem cell-based therapies are an attractive option to promote regeneration and repair defective tissues and organs. Thanks to their multipotency, high proliferation rate and the lack of major ethical limitations, "olfactory ecto-mesenchymal stem cells" (OE-MSCs) have been described as a promising candidate to treat a variety of damaged tissues. Easily accessible in the nasal cavity of most mammals, these cells are highly suitable for autologous cell-based therapies and do not face issues associated with other stem cells. However, their clinical use in humans and animals is limited due to a lack of preclinical studies on autologous transplantation and because no well-established methods currently exist to cultivate these cells. Here we evaluated the feasibility of collecting, purifying and amplifying OE-MSCs from different mammalian genera with the goal of promoting their interest in veterinary regenerative medicine. Biopsies of olfactory mucosa from eight mammalian genera (mouse, rat, rabbit, sheep, dog, horse, gray mouse lemur and macaque) were collected, using techniques derived from those previously used in humans and rats. The possibility of amplifying these cells and their stemness features and differentiation capability were then evaluated.

RESULTS

Biopsies were successfully performed on olfactory mucosa without requiring the sacrifice of the donor animal, except mice. Cell populations were rapidly generated from olfactory mucosa explants. These cells displayed similar key features of their human counterparts: a fibroblastic morphology, a robust expression of nestin, an ability to form spheres and similar expression of surface markers (CD44, CD73). Moreover, most of them also exhibited high proliferation rates and clonogenicity with genus-specific properties. Finally, OE-MSCs also showed the ability to differentiate into mesodermal lineages.

CONCLUSIONS

This article describes for the first time how millions of OE-MSCs can be quickly and easily obtained from different mammalian genera through protocols that are well-suited for autologous transplantations. Moreover, their multipotency makes them relevant to evaluate therapeutic application in a wide variety of tissue injury models. This study paves the way for the development of new fundamental and clinical studies based on OE-MSCs transplantation and suggests their interest in veterinary medicine.