Olfactory Bulb-Derived Cells Seeded on 3D Scaffolds Exhibit Neurotrophic Factor Expression and Pro-Angiogenic Properties

Olfactory ensheathing cells as candidate cells for chronic pain treatment

Chronic pain is often accompanied by tissue damage and pain hypersensitivity. It easily relapses and is challenging to cure, which seriously affects the patients' quality of life and is an urgent problem to be solved. Current treatment methods primarily rely on morphine drugs, which do not address the underlying nerve injury and may cause adverse reactions. Therefore, in recent years, scientists have shifted their focus from chronic pain treatment to cell transplantation. This review describes the classification and mechanism of chronic pain through the introduction of the characteristics of olfactory ensheathing cells (OECs), an in-depth discussion of special glial cells through the phagocytosis of nerve debris, receptor-ligand interactions, providing nutrition, and other inhibition of neuroinflammation, and ultimately supporting axon regeneration and mitigation of chronic pain. This review summarizes the potential and limitations of OECs for treating chronic pain by objectively analyzing relevant clinical trials and methods to enhance efficacy and future development prospects.

Promotion of Adrenal Pheochromocytoma (PC-12) Cell Proliferation and Outgrowth Using Schwann Cell-Laden Gelatin Methacrylate Substrate

Peripheral nerve injuries cause different degrees of nerve palsy and function loss. Due to the limitations of autografts, nerve tissue engineering (TE) scaffolds incorporated with various neurotrophic factors and cells have been investigated to promote nerve regeneration. However, the molecular mechanism is still poorly understood. In this study, we co-cultured Schwann cells (SCs) and rat adrenal pheochromocytoma (PC-12) cells on 50% degrees of methacryloyl substitution gelatin methacrylate (GelMA) scaffold. The SCs were encapsulated within the GelMA, and PC-12 cells were on the surface. A 5% GelMA was used as the co-culture scaffold since it better supports SCs proliferation, viability, and myelination and promotes higher neurotrophic factors secretion than 10% GelMA. In the co-culture, PC-12 cells demonstrated a higher cell proliferation rate and axonal extension than culturing without SCs, indicating that the secretion of neurotrophic factors from SCs can stimulate PC-12 growth and axonal outgrowth. The mRNA level for neurotrophic factors of SCs in 5% GelMA was further evaluated. We found significant upregulation when compared with a 2D culture, which suggested that this co-culture system could be a potential scaffold to investigate the mechanism of how SCs affect neuronal behaviors.

Comparison of the effects of two therapeutic strategies based on olfactory ensheathing cell transplantation and repetitive magnetic stimulation after spinal cord injury in female mice

Spinal cord injury (SCI) is a debilitating condition, which leads to a permanent loss of functions below the injury site. The events which take place after SCI are characterized by cellular death, release of inhibitory factors, and inflammation. Many therapies have been studied to cure SCI, among them magnetic stimulation aims to reduce the secondary damages in particular by decreasing apoptosis, while, cellular transplantation promotes neuroregeneration by enhancing axonal regrowth. In the present study, we compared individually primary olfactory ensheathing cell (OEC) transplantation and repetitive trans‐spinal magnetic stimulation (rTSMS) and then, we combined these two therapeutic approaches on tissue repair and functional recovery after SCI. To do so, SCIs were performed at Th10 level on female C57BL/6 mice, which were randomized into four groups: SCI, SCI + primary bOECs, SCI + STM, SCI + primary bulbar olfactory ensheathing cells (bOECs) + stimulation (STM). On these animals bioluminescence, immunohistological, and behavioral experiments were performed after SCI. Our results show that rTSMS has beneficial effect on the modulation of spinal scar by reducing fibrosis, demyelination, and microglial cell activation and by increasing the astroglial component of the scar, while, primary bOEC transplantation decreases microglial reactivity. At the opposite, locotronic experiments show that both treatments induce functional recovery. We did not observed any additional effect by combining the two therapeutic approaches. Taken together, the present study indicates that primary bOEC transplantation and rTSMS treatment act through different mechanisms after SCI to induce functional recovery. In our experimental paradigm, the combination of the two therapies does not induce any additional benefit.

Prevascularized Scaffolds Bearing Human Dental Pulp Stem Cells for Treating Complete Spinal Cord Injury

The regeneration of injured spinal cord is hampered by the lack of vascular supply and neurotrophic support. Transplanting tissue-engineered constructs with developed vascular networks and neurotrophic factors, and further understanding the pattern of vessel growth in the remodeled spinal cord tissue are greatly desired. To this end, highly vascularized scaffolds embedded with human dental pulp stem cells (DPSCs) are fabricated, which possess paracrine-mediated angiogenic and neuroregenerative potentials. The potent pro-angiogenic effect of the prevascularized scaffolds is first demonstrated in a rat femoral bundle model, showing robust vessel growth and blood perfusion induced within these scaffolds postimplantation, as evidenced by laser speckle contrast imaging and 3D microCT dual imaging modalities. More importantly, in a rat complete spinal cord transection model, the implantation of these scaffolds to the injured spinal cords can also promote revascularization, as well as axon regeneration, myelin deposition, and sensory recovery. Furthermore, 3D microCT imaging and novel morphometric analysis on the remodeled spinal cord tissue demonstrate substantial regenerated vessels, more significantly in the sensory tract regions, which correlates with behavioral recovery following prevascularization treatment. Taken together, prevascularized DPSC-embedded constructs bear angiogenic and neurotrophic potentials, capable of augmenting and modulating SCI repair.

Impact of Dual Cell Co-culture and Cell-conditioned Media on Yield and Function of a Human Olfactory Cell Line for Regenerative Medicine

Olfactory ensheathing cells (OECs) are a promising candidate therapy for neuronal tissue repair. However, appropriate priming conditions to drive a regenerative phenotype are yet to be determined. We first assessed the effect of using a human fibroblast feeder layer and fibroblast conditioned media on primary rat olfactory mucosal cells (OMCs). We found that OMCs cultured on fibroblast feeders had greater expression of the key OEC marker p75NTR (25.1 ± 10.7 cells/mm²) compared with OMCs cultured on laminin (4.0 ± 0.8 cells/mm², p = 0.001). However, the addition of fibroblast-conditioned media (CM) resulted in a significant increase in Thy1.1 (45.9 ± 9.0 cells/mm² versus 12.5 ± 2.5 cells/mm² on laminin, p = 0.006), an undesirable cell marker as it is regarded to be a marker of contaminating fibroblasts. A direct comparison between human feeders and GMP cell line Ms3T3 was then undertaken. Ms3T3 cells supported similar p75NTR levels (10.7 ± 5.3 cells/mm²) with significantly reduced Thy1.1 expression (4.8 ± 2.1 cells/mm²). Ms3T3 cells were used as feeder layers for human OECs to determine whether observations made in the rat model were conserved. Examination of the OEC phenotype (S100β expression and neurite outgrowth from NG108-15 cells) revealed that co-culture with fibroblast feeders had a negative effect on human OECs, contrary to observations of rat OECs. CM negatively affected rat and human OECs equally. When the best and worst conditions in terms of supporting S100β expression were used in NG108-15 neuron co-cultures, those with the highest S100β expression resulted in longer and more numerous neurites (22.8 ± 2.4 μm neurite length/neuron for laminin) compared with the lowest S100β expression (17.9 ± 1.1 μm for Ms3T3 feeders with CM). In conclusion, this work revealed that neither dual co-culture nor fibroblast-conditioned media support the regenerative OEC phenotype. In our case, a preliminary rat model was not predictive of human cell responses.

Regenerative Therapies for Spinal Cord Injury

Spinal cord injury (SCI) is a serious problem that primarily affects younger and middle-aged adults at its onset. To date, no effective regenerative treatment has been developed. Over the last decade, researchers have made significant advances in stem cell technology, biomaterials, nanotechnology, and immune engineering, which may be applied as regenerative therapies for the spinal cord. Although the results of clinical trials using specific cell-based therapies have proven safe, their efficacy has not yet been demonstrated. The pathophysiology of SCI is multifaceted, complex and yet to be fully understood. Thus, combinatorial therapies that simultaneously leverage multiple approaches will likely be required to achieve satisfactory outcomes. Although combinations of biomaterials with pharmacologic agents or cells have been explored, few studies have combined these modalities in a systematic way. For most strategies, clinical translation will be facilitated by the use of minimally invasive therapies, which are the focus of this review. In addition, this review discusses previously explored therapies designed to promote neuroregeneration and neuroprotection after SCI, while highlighting present challenges and future directions. Impact Statement To date there are no effective treatments that can regenerate the spinal cord after injury. Although there have been significant preclinical advances in bioengineering and regenerative medicine over the last decade, these have not translated into effective clinical therapies for spinal cord injury. This review focuses on minimally invasive therapies, providing extensive background as well as updates on recent technological developments and current clinical trials. This review is a comprehensive resource for researchers working towards regenerative therapies for spinal cord injury that will help guide future innovation.

Implantation of 3D Constructs Embedded with Oral Mucosa-Derived Cells Induces Functional Recovery in Rats with Complete Spinal Cord Transection

Spinal cord injury (SCI), involving damaged axons and glial scar tissue, often culminates in irreversible impairments. Achieving substantial recovery following complete spinal cord transection remains an unmet challenge. Here, we report of implantation of an engineered 3D construct embedded with human oral mucosa stem cells (hOMSC) induced to secrete neuroprotective, immunomodulatory, and axonal elongation-associated factors, in a complete spinal cord transection rat model. Rats implanted with induced tissue engineering constructs regained fine motor control, coordination and walking pattern in sharp contrast to the untreated group that remained paralyzed (42 vs. 0%). Immunofluorescence, CLARITY, MRI, and electrophysiological assessments demonstrated a reconnection bridging the injured area, as well as presence of increased number of myelinated axons, neural precursors, and reduced glial scar tissue in recovered animals treated with the induced cell-embedded constructs. Finally, this construct is made of bio-compatible, clinically approved materials and utilizes a safe and easily extractable cell population. The results warrant further research with regards to the effectiveness of this treatment in addressing spinal cord injury.

Current Options for Cell Therapy in Spinal Cord Injury

Spinal cord injury (SCI) is a complex pathology that evolves after primary acute mechanical injury, causing further damage to the spinal cord tissue that exacerbates clinical outcomes. Based on encouraging results from preclinical experiments, some cell treatments being translated into clinical practice demonstrate promising and effective improvement in sensory/motor function. Combinatorial treatments of cell and drug/biological factors have been demonstrated to be more effective than cell treatments alone. Recent advances have led to the development of biomaterials aiming to promote in situ cell delivery for SCI, together with combinatorial strategies using drugs/biomolecules to achieve a maximized multitarget approach. This review provides an overview of single and combinatorial regenerative cell treatments as well as potential delivery options to treat SCI.

Olfactory-ensheathing cell transplantation for peripheral nerve repair: update on recent developments

A number of important advances have been made using transplantation of olfactory-ensheathing cells (OECs) to provide therapeutic effects with regard to peripheral nerve repair. In vivo studies have focused on transplanting OECs to stimulate axonal regeneration and sprouting, increase remyelination, confer neuroprotection, enhance neovascularization and replace lost cells. OECs support axonal regeneration and remyelination with appropriate formation of axonal nodes of Ranvier with improvement of nerve conduction velocity. Current work using gene profiling and proteomics is identifying potential therapeutic differences between OECs harvested from nasal mucosa and the olfactory bulb and genes that OECs express that may be conducive to neural repair. OECs derived from nasal mucosa are of clinical interest since the cells could potentially be harvested from a patient and used for autotransplantation. Various nerve scaffolds and materials have been used for nerve repair and recent studies have examined OECs in combination with various supportive materials, including nanoparticles and scaffolds for peripheral nerve substance defects. This review will discuss the use of OECs in nerve repair and nerve defect injuries with specific emphasis on differences between OECs derived from the olfactory bulb and the olfactory mucosa.

Olfactory bulb transplantation in complete spinal cord injury: axonal regeneration and locomotor recovery

OBJECTIVES: To determine whether the intervention in rats is effective in terms of spinal cord regeneration and locomotor recovery, in order to obtain sufficient evidence to apply the therapy in humans. METHODS: a randomized, controlled, experimental, prospective, randomized trial was conducted, with a sample of 15 adult female Sprague-Dawley rats weighing 250 gr. They were divided into three equal groups, and trained for 2 weeks based on Pavlov's classical conditioning method, to strengthen the muscles of the 4 legs, stimulate the rats mentally, and keep them healthy for the surgery. RESULTS: It was observed that implantation of these cells into the site of injury may be beneficial to the process of spinal cord regeneration after spinal trauma, to mediate secretion of neurotrophic and neuroprotective chemokines, and that the OECs have the ability to bridge the repair site and decrease the formation of gliosis, creating a favorable environment for axonal regeneration. CONCLUSION: It is emphasized that the olfactory ensheathing glial cells possess unique regenerative properties; however, it was not until recently that the activity of promoting central nervous system regeneration was recognized.

Fibrin, a scaffold material for islet transplantation and pancreatic endocrine tissue engineering

Fibrin is derived from fibrinogen during injury to produce a blood clot and thus promote wound repair. Composed of different domains, including Arg-Gly-Asp amino acid motifs, fibrin is used extensively as a hydrogel and sealant in the clinic. By binding to cell surface receptors like integrins and acting as a supportive 3D scaffold, fibrin has been useful in promoting cell differentiation, proliferation, function, and survival. In particular, fibrin has been able to maintain islet cell architecture, promote beta cell insulin secretion, and islet angiogenesis, as well as inducing a protective effect against cell death. During islet transplantation, fibrin improved neovascularization and islet function. These improvements resulted in reduced number of transplanted islets necessary to reverse diabetes. Therefore, fibrin, as a biocompatible and biodegradable scaffold, should be considered during subcutaneous islet transplantation and beta cell expansion in vitro to ensure maintenance of islet cell function, proliferation, and survival to develop effective cell-based therapies for the treatment of diabetes.

Co-grafting of neural stem cells with olfactory en sheathing cells promotes neuronal restoration in traumatic brain injury with an anti-inflammatory mechanism

BACKGROUND

We sought to investigate the effects of co-grafting neural stem cells (NSCs) with olfactory ensheathing cells (OECs) on neurological behavior in rats subjected to traumatic brain injury (TBI) and explore underlying molecular mechanisms.

METHODS

TBI was established by percussion device made through a weight drop (50 g) from a 30 cm height. Cultured NSCs and OECs isolated from rats were labeled by Hoechst 33342 (blue) and chloromethyl-benzamidodialkyl carbocyanine (CM-Dil) (red), respectively. Then, NSCs and/or OECs, separately or combined, were transplanted into the area surrounding the injury site. Fourteen days after transplantation, neurological severity score (NSS) were recorded. The brain tissue was harvested and processed for immunocytochemistry, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), and reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Significant neurological function improvement was observed in the three transplant groups, compared to the TBI group, and co-transplantation gave rise to the best improvement. Morphological evaluation showed that the number of neurons in cortex from combination implantation was more than for other groups (P <0.05); conversely, the number of apoptotic cells showed a significant decrease by TUNEL staining. Transplanted NSCs and OECs could survive and migrate in the brain, and the number of neurons differentiating from NSCs in the co-transplantation group was significantly greater than in the NSCs group. At the molecular level, the expressions of IL-6 and BAD in the co-graft group were found to be down regulated significantly, when compared to either the NSC or OEC alone groups.

CONCLUSION

The present study demonstrates for the first time the optimal effects of co-grafting NSCs and OECs as a new strategy for the treatment of TBI via an anti-inflammation mechanism.