Human placenta-derived mesenchymal stem cells loaded on linear ordered collagen scaffold improves functional recovery after completely transected spinal cord injury in canine

Regenerative medicine approaches for the treatment of spinal cord injuries: Progress and challenges

Spinal cord injury (SCI) is a profound medical condition that significantly hampers motor function, imposing substantial limitations on daily activities and exerting a considerable financial burden on patients and their families. The constrained regenerative capacity of endogenous spinal cord tissue, exacerbated by the inflammatory response following the initial trauma, poses a formidable obstacle to effective therapy. Recent advancements in the field, stem cells, biomaterials, and molecular therapy, show promising outcomes. This review provides a comprehensive analysis of tissue engineering and regenerative medicine approaches for SCI treatment, including cell transplantation, tissue-engineered construct implantation, and other potential therapeutic strategies. Additionally, it sheds light on preclinical animal studies and recent clinical trials incorporating these modalities, providing a glimpse into the evolving landscape of SCI management. STATEMENT OF SIGNIFICANCE: The investigation into spinal cord injury (SCI) treatments focuses on reducing long-term impacts by targeting scar inhibition and enhancing regeneration through stem cells, with or without growth factors. Induced pluripotent stem cells (iPSCs) show promise for autologous use, with clinical trials confirming their safety. Challenges include low cell viability and difficulty in targeted differentiation. Biomaterial scaffolds hold potential for improving cell viability and integration, and extracellular vesicles (EVs) are emerging as a novel therapy. While EV research is in its early stages, stem cell trials demonstrate safety and potential recovery. Advancing tissue engineering approaches with biomaterial scaffolds is crucial for human trials.

Influential factors on stem cell therapy success in canine model of spinal cord Injury: A systematic review and meta-analysis

Spinal cord injury (SCI) is a serious medical condition. The search for an effective cure remains a persistent challenge. Current treatments, unfortunately, are unable to sufficiently improve neurological function, often leading to lifelong disability. This systematic review and meta-analysis evaluated the effectiveness of stem cell therapy for SCI using canine models. It also explored the optimal protocol for implementing stem cell therapy. A comprehensive search of studies was conducted from 2000 to October 2022. This study focused on five outcomes: motor function score, histopathology, IHC, western blot, and SEP. The results demonstrated a significant improvement in locomotion post-SCI in dogs treated with stem cell therapy. The therapy also led to an average increase of 3.15 points in the Olby score of the treated dogs compared to the control group. These findings highlights stem cell therapy's potential as a promising SCI treatment. The meta-analysis suggests that using bone marrow stem cells, undergoing neural differentiation in vitro, applying a surgical implantation or intrathecal route of administration, associating matrigel in combination with stem cells, and a waiting period of two weeks before starting treatment can enhance SCI treatment effectiveness.

The Placenta as a Source of Human Material for Neuronal Repair

Stem cell therapy has the potential to meet unsolved problems in tissue repair and regeneration, particularly in the neural tissues. However, an optimal source has not yet been found. Growing evidence indicates that positive effects produced in vivo by mesenchymal stem cells (MSCs) can be due not only to their plasticity but also to secreted molecules including extracellular vesicles (EVs) and the extracellular matrix (ECM). Trophic effects produced by MSCs may reveal the key to developing effective tissue-repair strategies, including approaches based on brain implants or other implantable neural electrodes. In this sense, MSCs will become increasingly valuable and needed in the future. The placenta is a temporary organ devoted to protecting and supporting the fetus. At the same time, the placenta represents an abundant and extremely convenient source of MSCs. Nonetheless, placenta-derived MSCs (P-MSCs) remain understudied as compared to MSCs isolated from other sources. This review outlines the limited literature describing the neuroregenerative effects of P-MSC-derived biomaterials and advocates for exploiting the potential of this untapped source for human regenerative therapies.

Integrating hydrogels manipulate ECM deposition after spinal cord injury for specific neural reconnections via neuronal relays

A bioinspired hydrogel composed of hyaluronic acid-graft-dopamine (HADA) and a designer peptide HGF-(RADA)4-DGDRGDS (HRR) was presented to enhance tissue integration following spinal cord injury (SCI). The HADA/HRR hydrogel manipulated the infiltration of PDGFRβ+ cells in a parallel pattern, transforming dense scars into an aligned fibrous substrate that guided axonal regrowth. Further incorporation of NT3 and curcumin promoted axonal regrowth and survival of interneurons at lesion borders, which served as relays for establishing heterogeneous axon connections in a target-specific manner. Notable improvements in motor, sensory, and bladder functions resulted in rats with complete spinal cord transection. The HADA/HRR + NT3/Cur hydrogel promoted V2a neuron accumulation in ventral spinal cord, facilitating the recovery of locomotor function. Meanwhile, the establishment of heterogeneous neural connections across the hemisected lesion of canines was documented in a target-specific manner via neuronal relays, significantly improving motor functions. Therefore, biomaterials can inspire beneficial biological activities for SCI repair.

Decellularized extracellular matrix enriched with GDNF enhances neurogenesis and remyelination for improved motor recovery after spinal cord injury

Motor functional improvement represents a paramount treatment objective in the post-spinal cord injury (SCI) recovery process. However, neuronal cell death and axonal degeneration following SCI disrupt neural signaling, impeding the motor functional recovery. In this study, we developed a multifunctional decellularized spinal cord-derived extracellular matrix (dSECM), crosslinked with glial cell-derived neurotrophic factor (GDNF), to promote differentiation of stem cells into neural-like cells and facilitate axonogenesis and remyelination. After decellularization, the immunogenic cellular components were effectively removed in dSECM, while the crucial protein components were retained which supports stem cells proliferation and differentiation. Furthermore, sustained release of GDNF from the dSECM facilitated axonogenesis and remyelination by activating the PI3K/Akt and MEK/Erk pathways. Our findings demonstrate that the dSECM-GDNF platform promotes neurogenesis, axonogenesis, and remyelination to enhance neural signaling, thereby yielding promising therapeutic effects for motor functional improvement after SCI. STATEMENT OF SIGNIFICANCE: The dSECM promotes the proliferation and differentiation of MSCs or NSCs by retaining proteins associated with positive regulation of neurogenesis and neuronal differentiation, while eliminating proteins related to negative regulation of neurogenesis. After crosslinking, GDNF can be gradually released from the platform, thereby promoting neural differentiation, axonogenesis, and remyelination to enhance neural signaling through activation of the PI3K/Akt and MEK/Erk pathways. In vivo experiments demonstrated that dSECM-GDNF/MSC@GelMA hydrogel exhibited the ability to facilitate neuronal regeneration at 4 weeks post-surgery, while promoting axonogenesis and remyelination at 8 weeks post-surgery, ultimately leading to enhanced motor functional recovery. This study elucidates the ability of neural regeneration strategy to promote motor functional recovery and provides a promising approach for designing multifunctional tissue for SCI treatment.

Current Advances in Mesenchymal Stem Cell Therapies Applied to Wounds and Skin, Eye, and Neuromuscular Diseases in Companion Animals

Mesenchymal stem cells (MSCs) are considered a very promising alternative tool in cell therapies and regenerative medicine due to their ease of obtaining from various tissues and their ability to differentiate into different cell types. This manuscript provides a review of current knowledge on the use of MSC-based therapies as an alternative for certain common pathologies in dogs and cats where conventional treatments are ineffective. The aim of this review is to assist clinical veterinarians in making decisions about the suitability of each protocol from a clinical perspective, rather than focusing solely on research. MSC-based therapies have shown promising results in certain pathologies, such as spinal cord injuries, wounds, and skin and eye diseases. However, the effectiveness of these cell therapies can be influenced by a wide array of factors, leading to varying outcomes. Future research will focus on designing protocols and methodologies that allow more precise and effective MSC treatments for each case.

3D bioprinting approaches for spinal cord injury repair

Regenerative healing of spinal cord injury (SCI) poses an ongoing medical challenge by causing persistent neurological impairment and a significant socioeconomic burden. The complexity of spinal cord tissue presents hurdles to successful regeneration following injury, due to the difficulty of forming a biomimetic structure that faithfully replicates native tissue using conventional tissue engineering scaffolds. 3D bioprinting is a rapidly evolving technology with unmatched potential to create 3D biological tissues with complicated and hierarchical structure and composition. With the addition of biological additives such as cells and biomolecules, 3D bioprinting can fabricate preclinical implants, tissue or organ-like constructs, andin vitromodels through precise control over the deposition of biomaterials and other building blocks. This review highlights the characteristics and advantages of 3D bioprinting for scaffold fabrication to enable SCI repair, including bottom-up manufacturing, mechanical customization, and spatial heterogeneity. This review also critically discusses the impact of various fabrication parameters on the efficacy of spinal cord repair using 3D bioprinted scaffolds, including the choice of printing method, scaffold shape, biomaterials, and biological supplements such as cells and growth factors. High-quality preclinical studies are required to accelerate the translation of 3D bioprinting into clinical practice for spinal cord repair. Meanwhile, other technological advances will continue to improve the regenerative capability of bioprinted scaffolds, such as the incorporation of nanoscale biological particles and the development of 4D printing.

Spinal Cord Injury: Emerging Technologies

The mainstay of treatment for spinal cord injury includes decompressive laminectomy and elevation of mean arterial pressure. However, outcomes often remain poor. Extensive research and ongoing clinical trials seek to design new treatment options for spinal cord injury, including stem cell therapy, scaffolds, brain-spine interfaces, exoskeletons, epidural electrical stimulation, ultrasound, and cerebrospinal fluid drainage. Some of these treatments are targeted at the initial acute window of injury, during which secondary damage occurs; others are designed to help patients living with chronic injuries.

Mimicked Spinal Cord Fibers Trigger Axonal Regeneration and Remyelination after Injury

Spinal cord injury (SCI) causes tissue structure damage and composition changes of the neural parenchyma, resulting in severe consequences for spinal cord function. Mimicking the components and microstructure of spinal cord tissues holds promise for restoring the regenerative microenvironment after SCI. Here, we have utilized electrospinning technology to develop aligned decellularized spinal cord fibers (A-DSCF) without requiring synthetic polymers or organic solvents. A-DSCF preserves multiple types of spinal cord extracellular matrix proteins and forms a parallel-oriented structure. Compared to aligned collagen fibers (A-CF), A-DSCF exhibits stronger mechanical properties, improved enzymatic stability, and superior functionality in the adhesion, proliferation, axonal extension, and myelination of differentiated neural progenitor cells (NPCs). Notably, axon extension or myelination has been primarily linked to Agrin (AGRN), Laminin (LN), or Collagen type IV (COL IV) proteins in A-DSCF. When transplanted into rats with complete SCI, A-DSCF loaded with NPCs improves the survival, maturation, axon regeneration, and motor function of the SCI rats. These findings highlight the potential of structurally and compositionally biomimetic scaffolds to promote axonal extension and remyelination after SCI.

Microvascular endothelial cells derived from spinal cord promote spinal cord injury repair

Neural regeneration after spinal cord injury (SCI) closely relates to the microvascular endothelial cell (MEC)-mediated neurovascular unit formation. However, the effects of central nerve system-derived MECs on neovascularization and neurogenesis, and potential signaling involved therein, are unclear. Here, we established a primary spinal cord-derived MECs (SCMECs) isolation with high cell yield and purity to describe the differences with brain-derived MECs (BMECs) and their therapeutic effects on SCI. Transcriptomics and proteomics revealed differentially expressed genes and proteins in SCMECs were involved in angiogenesis, immunity, metabolism, and cell adhesion molecular signaling was the only signaling pathway enriched of top 10 in differentially expressed genes and proteins KEGG analysis. SCMECs and BMECs could be induced angiogenesis by different stiffness stimulation of PEG hydrogels with elastic modulus 50-1650 Pa for SCMECs and 50-300 Pa for BMECs, respectively. Moreover, SCMECs and BMECs promoted spinal cord or brain-derived NSC (SNSC/BNSC) proliferation, migration, and differentiation at different levels. At certain dose, SCMECs in combination with the NeuroRegen scaffold, showed higher effectiveness in the promotion of vascular reconstruction. The potential underlying mechanism of this phenomenon may through VEGF/AKT/eNOS- signaling pathway, and consequently accelerated neuronal regeneration and functional recovery of SCI rats compared to BMECs. Our findings suggested a promising role of SCMECs in restoring vascularization and neural regeneration.

Decellularized extracellular matrix in the treatment of spinal cord injury

Functional limitation caused by spinal cord injury (SCI) has the problem of significant clinical and economic burden. Damaged spinal axonal connections and an inhibitory environment severely hamper neuronal function. Regenerative biomaterials can fill the cavity and produce an optimal microenvironment at the site of SCI, inhibiting apoptosis, inflammation, and glial scar formation while promoting neurogenesis, axonal development, and angiogenesis. Decellularization aims to eliminate cells from the ultrastructure of tissues while keeping tissue-specific components that are similar to the structure of real tissues, making decellularized extracellular matrix (dECM) a suitable scaffold for tissue engineering. dECM has good biocompatibility, it can be widely obtained from natural organs of different species, and can be co-cultured with cells for 3D printing to obtain the target scaffold. In this paper, we reviewed the pathophysiology of SCI, the characteristics of dECM and its preparation method, and the application of dECM in the treatment of SCI. Although dECM has shown its therapeutic effect at present, there are still many indicators that need to be taken into account, such as the difficulty in obtaining materials and standardized production mode for large-scale use, the effect of decellularization on the physical and chemical properties of dECM, and the study on the synergistic effect of dECM and cells.

Engineered human spinal cord-like tissues with dorsal and ventral neuronal progenitors for spinal cord injury repair in rats and monkeys

Transplanting human neural progenitor cells is a promising method of replenishing the lost neurons after spinal cord injury (SCI), but differentiating neural progenitor cells into the diverse types of mature functional spinal cord neurons in vivo is challenging. In this study, engineered human embryonic spinal cord-like tissues with dorsal and ventral neuronal characters (DV-SC) were generated by inducing human neural progenitor cells (hscNPCs) to differentiate into various types of dorsal and ventral neuronal cells on collagen scaffold in vitro. Transplantation of DV-SC into complete SCI models in rats and monkeys showed better therapeutic effects than undifferentiated hscNPCs, including pronounced cell survival and maturation. DV-SC formed a targeted connection with the host's ascending and descending axons, partially restored interrupted neural circuits, and improved motor evoked potentials and the hindlimb function of animals with SCI. This suggests that the transplantation of pre-differentiated hscNPCs with spinal cord dorsal and ventral neuronal characteristics could be a promising strategy for SCI repair.

Cooperative assembly of a designer peptide and silk fibroin into hybrid nanofiber gels for neural regeneration after spinal cord injury

Local reconstruction of a permissive environment with biomaterials is a promising strategy to treat spinal cord injury (SCI). We reported a hybrid hydrogel fabricated from a small functional self-assembling peptide (F-SAP) and large silk fibroin (SF). The diffusion of SF micelles into F-SAP solution was driven by the dynamic synergy between osmotic pressure and F-SAP/SF electrostatic interactions, resulting in the rearrangement of SF micelles and the formation of rod-like filaments with axes nearly perpendicular to F-SAP nanofibers. Spectroscopy analysis, including circular dichroism, Raman and fluorescence, indicated conformation changes of SF from random coil to β sheet, which contributed to enhanced mechanical properties of the resultant hybrid hydrogel. Furthermore, the F-SAP/SF hybrid hydrogel coupled with controlled release of NT-3 provided a permissive environment for neural regeneration by providing nanofibrous substrates for regenerating axons, inflammatory modulation and remyelination, consequently resulting in improved locomotion and electrophysiological properties. This hydrogel could be used as a long-term stent in vivo for the treatment of SCI.

BMP-2 functional polypeptides relieve osteolysis via bi-regulating bone formation and resorption coupled with macrophage polarization

Osteolysis caused by wear debris around the prosthesis is the main reason for aseptic loosening. Extending prosthetic service life is still challenging. In this study, we first synthesized a bone morphogenetic protein-2 (BMP-2) functional polypeptide (BMP2pp), and evaluated the effects of BMP2pp on macrophage polarization and impaired osteogenesis caused by titanium (Ti) particles in vitro. Then, we delineated the impact of BMP2pp on bone formation and resorption in a mouse calvarial bone osteolysis model induced by Ti particles. The results showed that BMP2pp not only alleviated the Ti-induced inhibition of osteoblastic differentiation in human placenta-derived mesenchymal stem cells (hPMSCs) but also prevented Ti-induced M1 macrophage polarization and promoted M2 macrophage differentiation in mice. Conditioned medium from BMP2pp-activated macrophages increased the osteogenesis of hPMSCs. The western blot results indicated a significant decrease in the expression of NF-κB inducing kinase (NIK) and phospho-NF-κB p65 in bone marrow-derived macrophages treated with BMP2pp. Furthermore, we clarified the protective effect of BMP2pp on bone formation and the reduction in bone resorption coupled with the immunomodulatory properties of calvarial osteolysis in mice. In summary, BMP2pp ameliorated the Ti-mediated impairment in osteogenic potential of hPMSCs, suppressed the M1 polarization of macrophages by inhibiting the activation of the NF-κB signaling pathway, and ameliorated Ti-induced bone osteolysis. Our research suggests that BMP2pp may be a potential option for treating prosthetic loosening induced by wear debris from prostheses.

The Application of Biomaterials in Spinal Cord Injury

The spinal cord and the brain form the central nervous system (CNS), which is the most important part of the body. However, spinal cord injury (SCI) caused by external forces is one of the most difficult types of neurological injury to treat, resulting in reduced or even absent motor, sensory and autonomic functions. It leads to the reduction or even disappearance of motor, sensory and self-organizing nerve functions. Currently, its incidence is increasing each year worldwide. Therefore, the development of treatments for SCI is urgently needed in the clinic. To date, surgery, drug therapy, stem cell transplantation, regenerative medicine, and rehabilitation therapy have been developed for the treatment of SCI. Among them, regenerative biomaterials that use tissue engineering and bioscaffolds to transport cells or drugs to the injured site are considered the most promising option. In this review, we briefly introduce SCI and its molecular mechanism and summarize the application of biomaterials in the repair and regeneration of tissue in various models of SCI. However, there is still limited evidence about the treatment of SCI with biomaterials in the clinic. Finally, this review will provide inspiration and direction for the future study and application of biomaterials in the treatment of SCI.

Multifunctional hydrogel modulates the immune microenvironment to improve allogeneic spinal cord tissue survival for complete spinal cord injury repair

Transplantation of allogeneic adult spinal cord tissues (aSCTs) to replace the injured spinal cord, serves as a promising strategy in complete spinal cord injury (SCI) repair. However, in addition to allograft immune rejection, damage-associated molecular pattern (DAMP)-mediated inflammatory microenvironments greatly impair the survival and function of transplants. In this study, we aimed to regulate the immune microenvironment after aSCT implantation by developing a functional hybrid gelatin and hyaluronic acid hydrogel (F-G/H) modified with cationic polymers and anti-inflammatory cytokines that can gelatinize at both ends of the aSCT to glue the grafts for perfect matching at defects. The F-G/H hydrogel exhibited the capacities of DAMP scavenging, sustainably released anti-inflammatory cytokines, and reduced lymphocyte accumulation, thereby modulating the immune response and enhancing the survival and function of aSCTs. When the hydrogel was used in combination with a systemic immunosuppressive drug treatment, the locomotor functions of SCI rats were significantly improved after aSCTs and F-G/H transplantation. This biomaterial-based immunomodulatory strategy may provide the potential for spinal cord graft replacement for treating SCI. STATEMENT OF SIGNIFICANCE: In this study, we aimed to regulate the immune microenvironment by developing a functional hybrid gelatin and hyaluronic acid hydrogel (F-G/H) modified with cationic polymers and anti-inflammatory cytokines that can gelatinize at both ends of the aSCT to glue the grafts for perfect matching at defects. We found that with the treatment of F-G/H hydrogel, the aSCT survival and function was significantly improved, as a result of reducing recruitment and activation of immune cells through TLR- and ST-2- related signaling. With the combination of immunosuppressive drug treatment, the locomotor functions of SCI rats were significantly improved after aSCTs and F-G/H transplantation. Findings from this work suggest the potential application of the F-G/H as a biomaterial-based immunoregulatory strategy for improving the therapeutic efficiency of the transplanted spinal cord graft for spinal cord injury repair.

Can a Scaffold Enriched with Mesenchymal Stem Cells Be a Good Treatment for Spinal Cord Injury?

Spinal cord injury (SCI) is a worldwide highly crippling disease that can lead to the loss of motor and sensory neurons. Among the most promising therapies, there are new techniques of tissue engineering based on stem cells that promote neuronal regeneration. Among the different types of stem cells, mesenchymal stem cells (MSCs) seem the most promising. Indeed, MSCs are able to release trophic factors and to differentiate into the cell types that can be found in the spinal cord. Currently, the most common procedure to insert cells in the lesion site is infusion. However, this causes a low rate of survival and engraftment in the lesion site. For these reasons, tissue engineering is focusing on bioresorbable scaffolds to help the cells to stay in situ. Scaffolds do not only have a passive role but become fundamental for the trophic support of cells and the promotion of neuroregeneration. More and more types of materials are being studied as scaffolds to decrease inflammation and increase the engraftment as well as the survival of the cells. Our review aims to highlight how the use of scaffolds made from biomaterials enriched with MSCs gives positive results in in vivo SCI models as well as the first evidence obtained in clinical trials.

Application of Collagen-Based Scaffolds for the Treatment of Spinal Cord Injuries in Animal Models: A Literature Update

SCI is regarded as one of the most devastating central nervous system (CNS) injuries, exhibiting an alarmingly rising incidence rate, indirectly connected with the expansion of the global economy. The consequences of SCI are multidimensional: SCI injuries may result in permanent voluntary motor dysfunction and loss of sensation while incurring heavy economic and psychological burdens as part of the treatment. Thus, it is crucial to develop effective and suitable SCI treatment strategies. Collagen-based scaffold application is one of the most promising methods of SCI treatment.

This review compiles newer bibliographical data regarding the application of collagen scaffolds for the treatment of Spinal cord injury (SCI) in animal models. Recently, several relevant studies have been carried out using carefully selected animals with similar pathophysiology to humans. In mouse, rat and canine models that have undergone transection or hemisection, the stump connection, the transplanted cell differentiation, and the elimination of glial scar are promising. Also, encouraging results have been found regarding the increased neuronal growth, the decreased collagen deposition, the behavioral recovery, the improved electrophysiology, and the enhanced axonal regeneration. 

Reverse Adverse Immune Microenvironments by Biomaterials Enhance the Repair of Spinal Cord Injury

Spinal cord injury (SCI) is a severe and traumatic disorder that ultimately results in the loss of motor, sensory, and autonomic nervous function. After SCI, local immune inflammatory response persists and does not weaken or disappear. The interference of local adverse immune factors after SCI brings great challenges to the repair of SCI. Among them, microglia, macrophages, neutrophils, lymphocytes, astrocytes, and the release of various cytokines, as well as the destruction of the extracellular matrix are mainly involved in the imbalance of the immune microenvironment. Studies have shown that immune remodeling after SCI significantly affects the survival and differentiation of stem cells after transplantation and the prognosis of SCI. Recently, immunological reconstruction strategies based on biomaterials have been widely explored and achieved good results. In this review, we discuss the important factors leading to immune dysfunction after SCI, such as immune cells, cytokines, and the destruction of the extracellular matrix. Additionally, the immunomodulatory strategies based on biomaterials are summarized, and the clinical application prospects of these immune reconstructs are evaluated.

Interaction of Neural Stem Cells (NSCs) and Mesenchymal Stem Cells (MSCs) as a Promising Approach in Brain Study and Nerve Regeneration

Rapid developments in stem cell research in recent years have provided a solid foundation for their use in medicine. Over the last few years, hundreds of clinical trials have been initiated in a wide panel of indications. Disorders and injuries of the nervous system still remain a challenge for the regenerative medicine. Neural stem cells (NSCs) are the optimal cells for the central nervous system restoration as they can differentiate into mature cells and, most importantly, functional neurons and glial cells. However, their application is limited by multiple factors such as difficult access to source material, limited cells number, problematic, long and expensive cultivation in vitro, and ethical considerations. On the other hand, according to the available clinical databases, most of the registered clinical trials involving cell therapies were carried out with the use of mesenchymal stem/stromal/signalling cells (MSCs) obtained from afterbirth or adult human somatic tissues. MSCs are the multipotent cells which can also differentiate into neuron-like and glia-like cells under proper conditions in vitro; however, their main therapeutic effect is more associated with secretory and supportive properties. MSCs, as a natural component of cell niche, affect the environment through immunomodulation as well as through the secretion of the trophic factors. In this review, we discuss various therapeutic strategies and activated mechanisms related to bilateral MSC–NSC interactions, differentiation of MSCs towards the neural cells (subpopulation of crest-derived cells) under the environmental conditions, bioscaffolds, or co-culture with NSCs by recreating the conditions of the neural cell niche.

Are Cell-Based Therapies Safe and Effective in the Treatment of Neurodegenerative Diseases? A Systematic Review with Meta-Analysis

Over the past two decades, significant advances have been made in the field of regenerative medicine. However, despite being of the utmost clinical urgency, there remains a paucity of therapeutic strategies for conditions with substantial neurodegeneration such as (progressive) multiple sclerosis (MS), spinal cord injury (SCI), Parkinson's disease (PD) and Alzheimer's disease (AD). Different cell types, such as mesenchymal stromal cells (MSC), neuronal stem cells (NSC), olfactory ensheathing cells (OEC), neurons and a variety of others, already demonstrated safety and regenerative or neuroprotective properties in the central nervous system during the preclinical phase. As a result of these promising findings, in recent years, these necessary types of cell therapies have been intensively tested in clinical trials to establish whether these results could be confirmed in patients. However, extensive research is still needed regarding elucidating the exact mechanism of action, possible immune rejection, functionality and survival of the administered cells, dose, frequency and administration route. To summarize the current state of knowledge, we conducted a systematic review with meta-analysis. A total of 27,043 records were reviewed by two independent assessors and 71 records were included in the final quantitative analysis. These results show that the overall frequency of serious adverse events was low: 0.03 (95% CI: 0.01-0.08). In addition, several trials in MS and SCI reported efficacy data, demonstrating some promising results on clinical outcomes. All randomized controlled studies were at a low risk of bias due to appropriate blinding of the treatment, including assessors and patients. In conclusion, cell-based therapies in neurodegenerative disease are safe and feasible while showing promising clinical improvements. Nevertheless, given their high heterogeneity, the results require a cautious approach. We advocate for the harmonization of study protocols of trials investigating cell-based therapies in neurodegenerative diseases, adverse event reporting and investigation of clinical outcomes.

Recovery of motor function in rats with complete spinal cord injury following implantation of collagen/silk fibroin scaffold combined with human umbilical cord-mesenchymal stem cells

OBJECTIVE

This study aimed to assess the effect of the collagen/silk fibroin scaffolds seeded with human umbilical cord-mesenchymal stem cells on functional recovery after acute complete spinal cord injury.

METHODS

The fibroin and collagen were mixed (mass ratio, 3:7), and the composite scaffolds were produced. Forty rats were randomly divided into the Sham group (without spinal cord injury), spinal cord injury group (spinal cord transection without any implantation), collagen/silk fibroin scaffolds group (spinal cord transection with implantation of the collagen/silk fibroin scaffolds), and collagen/silk fibroin scaffolds + human umbilical cord-mesenchymal stem cells group (spinal cord transection with the implantation of the collagen/silk fibroin scaffolds co-cultured with human umbilical cord-mesenchymal stem cells). Motor evoked potential, Basso-Beattie-Bresnahan scale, modified Bielschowsky's silver staining, and immunofluorescence staining were performed.

RESULTS

The BBB scores in the collagen/silk fibroin scaffolds + human umbilical cord-mesenchymal stem cells group were significantly higher than those in the spinal cord injury and collagen/silk fibroin scaffolds groups (p<0.05 or p<0.01). The amplitude and latency were markedly improved in the collagen/silk fibroin scaffolds + human umbilical cord-mesenchymal stem cells group compared with the spinal cord injury and collagen/silk fibroin scaffolds groups (p<0.05 or p<0.01). Meanwhile, compared to the spinal cord injury and collagen/silk fibroin scaffolds groups, more neurofilament positive nerve fiber ensheathed by myelin basic protein positive structure at the injury site were observed in the collagen/silk fibroin scaffolds + human umbilical cord-mesenchymal stem cells group (p<0.01, p<0.05). The results of Bielschowsky's silver staining indicated more nerve fibers was observed at the lesion site in the collagen/silk fibroin scaffolds + human umbilical cord-mesenchymal stem cells group compared with the spinal cord injury and collagen/silk fibroin scaffolds groups (p<0.01, p< 0.05).

CONCLUSION

The results demonstrated that the transplantation of human umbilical cord-mesenchymal stem cells on a collagen/silk fibroin scaffolds could promote nerve regeneration, and recovery of neurological function after acute spinal cord injury.

The Unique Properties of Placental Mesenchymal Stromal Cells: A Novel Source of Therapy for Congenital and Acquired Spinal Cord Injury

Spinal cord injury (SCI) is a devasting condition with no reliable treatment. Spina bifida is the most common cause of congenital SCI. Cell-based therapies using mesenchymal stem/stromal cells (MSCS) have been largely utilized in SCI. Several clinical trials for acquired SCI use adult tissue-derived MSC sources, including bone-marrow, adipose, and umbilical cord tissues. The first stem/stromal cell clinical trial for spina bifida is currently underway (NCT04652908). The trial uses early gestational placental-derived mesenchymal stem/stromal cells (PMSCs) during the fetal repair of myelomeningocele. PMSCs have been shown to exhibit unique neuroprotective, angiogenic, and antioxidant properties, all which are promising applications for SCI. This review will summarize the unique properties and current applications of PMSCs and discuss their therapeutic role for acquired SCI.

The combination of nanoscaffolds and stem cell transplantation: Paving a promising road for spinal cord injury regeneration

Spinal cord injury (SCI), one of the most devastating traumas, has caused long-term disability in millions of people worldwide. The pathophysiology of SCI primarily occurs in two stages classified as primary injury and secondary injury. Due to the rupture of axons and the apoptosis of neurons, patients lose their motor, sensory, and reflex functions, which also imposes a huge burden on families and society. However, traditional surgery does not facilitate neuronal regeneration. Although neural stem cells (NSCs) have the potential for multidirectional differentiation, the probability of differentiation into neurons and survival are still low. Surprisingly, the unique properties of nanotechnologies enable targeted drug delivery while reducing adverse reactions, assisting NSCs in differentiating into neurons. Here, recent studies on promising nanoscaffolds are highlighted, and their strengths and drawbacks are evaluated. Although the treatment of SCI remains fraught with challenges, the combination of nanoscaffolds and NSCs pave a promising road for SCI regeneration.

Collagen/heparin sulfate scaffold combined with mesenchymal stem cells treatment for canines with spinal cord injury: A pilot feasibility study

BACKGROUND

Due to endogenous neuronal deficiency and glial scar formation, spinal cord injury (SCI) often leads to irreversible neurological loss. Accumulating evidence has shown that a suitable scaffold has important value for promoting nerve regeneration after SCI. Collagen/heparin sulfate scaffold (CHSS) has shown effect for guiding axonal regeneration and decreasing glial scar deposition after SCI. The current research aimed to evaluate the utility of the CHSSs adsorbed with mesenchymal stem cells (MSCs) on nerve regeneration, and functional recovery after acute complete SCI.

METHODS

CHSSs were prepared, and evaluated for biocompatibility. The CHSSs adsorbed with MSCs were transplanted into these canines with complete SCI.

RESULTS

We observed that MSCs had good biocompatibility with CHSSs. In complete transverse SCI models, the implantation of CHSS co-cultured with MSCs exhibited significant improvement in locomotion, motor evoked potential, magnetic resonance imaging, diffusion tensor imaging, and urodynamic parameters. Meanwhile, nerve fibers were markedly improved in the CHSS adsorbed with MSCs group. Moreover, we observed that the implantation of CHSS combined with MSCs modulated inflammatory cytokine levels.

CONCLUSIONS

The results preliminarily demonstrated that the transplantation of MSCs on a CHSS could improve the recovery of motor function after SCI. Thus, implanting the MSCs-laden CHSS is a promising combinatorial therapy for treatment in acute SCI.

Long-term clinical observation of patients with acute and chronic complete spinal cord injury after transplantation of NeuroRegen scaffold

Spinal cord injury (SCI) often results in an inhibitory environment at the injury site. In our previous studies, transplantation of a scaffold combined with stem cells was proven to induce neural regeneration in animal models of complete SCI. Based on these preclinical studies, collagen scaffolds loaded with the patients' own bone marrow mononuclear cells or human umbilical cord mesenchymal stem cells were transplanted into SCI patients. Fifteen patients with acute complete SCI and 51 patients with chronic complete SCI were enrolled and followed up for 2 to 5 years. No serious adverse events related to functional scaffold transplantation were observed. Among the patients with acute SCI, five patients achieved expansion of their sensory positions and six patients recovered sensation in the bowel or bladder. Additionally, four patients regained voluntary walking ability accompanied by reconnection of neural signal transduction. Among patients with chronic SCI, 16 patients achieved expansion of their sensation level and 30 patients experienced enhanced reflexive defecation sensation or increased skin sweating below the injury site. Nearly half of the patients with chronic cervical SCI developed enhanced finger activity. These long-term follow-up results suggest that functional scaffold transplantation may represent a feasible treatment for patients with complete SCI.

Scar tissue removal-activated endogenous neural stem cells aid Taxol-modified collagen scaffolds in repairing chronic long-distance transected spinal cord injury

Scar tissue removal combined with biomaterial implantation is considered an effective measure to repair chronic transected spinal cord injury (SCI). However, whether more scar tissue removal surgeries could affect the treatment effects of biomaterial implantation still needs to be explored. In this study, we performed the first scar tissue removal surgery in the 3^rd month and the second in the 6^th month after completely removing 1 cm of spinal tissue in canines. We found that Taxol-modified linear ordered collagen scaffold (LOCS + Taxol) implantation could promote axonal regeneration, neurogenesis, and electrophysiological and functional recovery only in canines at the first scar tissue removal surgery, but not in canines at the second scar tissue removal surgery. Interestingly, we found that more endogenous neural stem cells (NSCs) around the injured site could be activated in canines with the first rather than the second scar tissue removal. Furthermore, we demonstrated that Taxol could promote the neuronal differentiation of NSCs in the myelin inhibition microenvironment through the p38 MAPK signaling pathway in vitro. Therefore, we speculated that endogenous NSC activation by the first scar tissue removal surgery and its further differentiation into neurons induced by Taxol may contribute to functional recovery in canines. Together, LOCS + Taxol implantation in combination with the first scar tissue removal provides a promising therapy for chronic long-distance transected SCI repair with the help of scar tissue removal activated endogenous NSCs.

Upregulation of Apol8 by Epothilone D facilitates the neuronal relay of transplanted NSCs in spinal cord injury

BACKGROUND

Microtubule-stabilizing agents have been demonstrated to modulate axonal sprouting during neuronal disease. One such agent, Epothilone D, has been used to treat spinal cord injury (SCI) by promoting axonal sprouting at the lesion site after SCI. However, the role of Epothilone D in the differentiation of neural stem cells (NSCs) in SCI repair is unknown. In the present study, we mainly explored the effects and mechanisms of Epothilone D on the neuronal differentiation of NSCs and revealed a potential new SCI treatment.

METHODS

In vitro differentiation assays, western blotting, and quantitative real-time polymerase chain reaction were used to detect the effects of Epothilone D on NSC differentiation. Retrograde tracing using a pseudotyped rabies virus was then used to detect neuronal circuit construction. RNA sequencing (RNA-Seq) was valuable for exploring the target gene involved in the neuronal differentiation stimulated by Epothilone D. In addition, lentivirus-induced overexpression and RNA interference technology were applied to demonstrate the function of the target gene. Last, an Apol8-NSC-linear ordered collagen scaffold (LOCS) graft was prepared to treat a mouse model of SCI, and functional and electrophysiological evaluations were performed.

RESULTS

We first revealed that Epothilone D promoted the neuronal differentiation of cultured NSCs and facilitated neuronal relay formation in the injured site after SCI. Furthermore, the RNA-Seq results demonstrated that Apol8 was upregulated during Epothilone D-induced neuronal relay formation. Lentivirus-mediated Apol8 overexpression in NSCs (Apol8-NSCs) promoted NSC differentiation toward neurons, and an Apol8 interference assay showed that Apol8 had a role in promoting neuronal differentiation under the induction of Epothilone D. Last, Apol8-NSC transplantation with LOCS promoted the neuronal differentiation of transplanted NSCs in the lesion site as well as synapse formation, thus improving the motor function of mice with complete spinal cord transection.

CONCLUSIONS

Epothilone D can promote the neuronal differentiation of NSCs by upregulating Apol8, which may provide a promising therapeutic target for SCI repair.

Hydrogel from acellular porcine adipose tissue promotes survival of adipose tissue transplantation

Lipofilling is a popular technique for soft tissue augmentation, limited by unpredictable graft survival. This study aimed at exploring the effect of hydrogel from acellular porcine adipose tissue (HAPA) on angiogenesis and survival of adipose tissue used for lipofilling. The effect of HAPA on adipose-derived stem cells (ADSCs) proliferation, adipogenic differentiation, and vascular endothelial growth factor (VEGF) secretion were evaluated in hypoxia and normoxiain vitro. For thein vivostudy, adipose tissue with phosphate buffered saline, ADSCs, and HAPA (with or without ADSCs) were co-injected subcutaneously into nude mice. HAPA-ADSCs mixture (tissue engineering adipose tissue) was also grafted. Gross observation, volume measurement, and ultrasound observation were assessed. For histological assessment, hematoxylin and eosin, perilipin, cluster of differentiation 31 (CD31), Ki67, and transferase-mediated d-UTP nick end labelling (TUNEL) staining were performed. HAPA improved ADSCs proliferation, VEGF secretion, and adipogenic differentiation under normoxia and hypoxia conditionsin vitrostudy. For thein vivostudy, HAPA showed improved volume retention and angiogenesis, and reduced cell apoptosis when compared to ADSCs-assisted lipofilling and pure lipofilling. In conclusion, HAPA could maintain ADSCs viability and improve cell resistant to hypoxia and might be a promising biomaterial to assist lipofilling.

Collagen-based scaffolds: An auspicious tool to support repair, recovery, and regeneration post spinal cord injury

Spinal cord injury (SCI) is a perplexing traumatic disease that habitually gives ride to permanent disability, motor, and sensory impairment. Despite the existence of several therapeutic approaches for the injured motor or sensory neurons, they can't promote axonal regeneration. Whether prepared by conventional or rapid prototyping techniques, scaffolds can be applied to refurbish the continuity of the injured site, by creating a suitable environment for tissue repair, axonal regeneration, and vascularization. Collagen is a multi-sourced protein, found in animals skin, tendons, cartilage, bones, and human placenta, in addition to marine biomass. Collagen is highly abundant in the extracellular matrix and is known for its biocompatibility, biodegradability, porous structure, good permeability, low immunogenicity and thus is extensively applied in the pharmaceutical, cosmetic, and food industries as well as the tissue engineering field. Collagen in scaffolds is usually functionalized with different ligands and factors such as, stem cells, embryonic or human cells to augment its binding specificity and activity. The review summarizes the significance of collagen-based scaffolds and their influence on regeneration, repair and recovery of spinal cord injuries.

Lineage tracing reveals the origin of Nestin-positive cells are heterogeneous and rarely from ependymal cells after spinal cord injury

Nestin is expressed extensively in neural stem/progenitor cells during neural development, but its expression is mainly restricted to the ependymal cells in the adult spinal cord. After spinal cord injury (SCI), Nestin expression is reactivated and Nestin-positive (Nestin⁺) cells aggregate at the injury site. However, the derivation of Nestin⁺ cells is not clearly defined. Here, we found that Nestin expression was substantially increased in the lesion edge and lesion core after SCI. Using a tamoxifen inducible CreER(T2)-loxP system, we verified that ependymal cells contribute few Nestin⁺ cells either to the lesion core or the lesion edge after SCI. In the lesion edge, GFAP⁺ astrocytes were the main cell type that expressed Nestin; they then formed an astrocyte scar. In the lesion core, Nestin⁺ cells expressed αSMA or Desmin, indicating that they might be derived from pericytes. Our results reveal that Nestin⁺ cells in the lesion core and edge came from various cell types and rarely from ependymal cells after complete transected SCI, which may provide new insights into SCI repair.

Human Mesenchymal Stem Cells for Spinal Cord Injury

Spinal Cord Injury (SCI), as a devastating and life-altering neurological disorder, is one of the most serious health issues. Currently, the management of acute SCI includes pharmacotherapy and surgical decompression. Both the approaches have been observed to have adverse physiological effects on SCI patients. Therefore, novel therapeutic targets for the management of SCI are urgently required for developing cell-based therapies. Multipotent stem cells, as a novel strategy for the treatment of tissue injury, may provide an effective therapeutic option against many neurological disorders. Mesenchymal stem cells (MSCs) or multipotent stromal cells can typically self-renew and generate various cell types. These cells are often isolated from bone marrow (BM-MSCs), adipose tissues (AD-MSCs), umbilical cord blood (UCB-MSCs), and placenta (PMSCs). MSCs have remarkable potential for the development of regenerative therapies in animal models and humans with SCI. Herein, we summarize the therapeutic potential of human MSCs in the treatment of SCI.

Emerging and Adjunctive Therapies for Spinal Cord Injury Following Acute Canine Intervertebral Disc Herniation

Some dogs do not make a full recovery following medical or surgical management of acute canine intervertebral disc herniation (IVDH), highlighting the limits of currently available treatment options. The multitude of difficulties in treating severe spinal cord injury are well-recognized, and they have spurred intense laboratory research, resulting in a broad range of strategies that might have value in treating spinal cord-injured dogs. These include interventions that aim to directly repair the spinal cord lesion, promote axonal sparing or regeneration, mitigate secondary injury through neuroprotective mechanisms, or facilitate functional compensation. Despite initial promise in experimental models, many of these techniques have failed or shown mild efficacy in clinical trials in humans and dogs, although high quality evidence is lacking for many of these interventions. However, the continued introduction of new options to the veterinary clinic remains important for expanding our understanding of the mechanisms of injury and repair and for development of novel and combined strategies for severely affected dogs. This review outlines adjunctive or emerging therapies that have been proposed as treatment options for dogs with acute IVDH, including discussion of local or lesion-based approaches as well as systemically applied treatments in both acute and subacute-to-chronic settings. These interventions include low-level laser therapy, electromagnetic fields or oscillating electrical fields, adjunctive surgical techniques (myelotomy or durotomy), systemically or locally-applied hypothermia, neuroprotective chemicals, physical rehabilitation, hyperbaric oxygen therapy, electroacupuncture, electrical stimulation of the spinal cord or specific peripheral nerves, nerve grafting strategies, 4-aminopyridine, chondroitinase ABC, and cell transplantation.

Injectable collagen scaffold promotes swine myocardial infarction recovery by long-term local retention of transplanted human umbilical cord mesenchymal stem cells

Stem cell therapy is an attractive approach for recovery from myocardial infarction (MI) but faces the challenges of rapid diffusion and poor survival after transplantation. Here we developed an injectable collagen scaffold to promote the long-term retention of transplanted cells in chronic MI. Forty-five minipigs underwent left anterior descending artery (LAD) ligation and were equally divided into three groups 2 months later (collagen scaffold loading with human umbilical mesenchymal stem cell (hUMSC) group, hUMSC group, and placebo group (only phosphate-buffered saline (PBS) injection)). Immunofluorescence staining indicated that the retention of transplanted cells was promoted by the collagen scaffold. Echocardiography and cardiac magnetic resonance imaging (CMR) showed much higher left ventricular ejection fraction (LVEF) and lower infarct size percentage in the collagen/hUMSC group than in the hUMSC and placebo groups at 12 months after treatment. There were also higher densities of vWf-, α-sma-, and cTnT-positive cells in the infarct border zone in the collagen/cell group, as revealed by immunohistochemical analysis, suggesting better angiogenesis and more cardiomyocyte survival after MI. Thus, the injectable collagen scaffold was safe and effective on a large animal myocardial model, which is beneficial for constructing a favorable microenvironment for applying stem cells in clinical MI.

Stem Cell Conditioned Medium Treatment for Canine Spinal Cord Injury: Pilot Feasibility Study

Spinal cord injury (SCI) involves nerve damage and often leads to motor, sensory and autonomic dysfunctions. In the present study, we have designed a clinical protocol to assess the feasibility of systemic delivery of allogenic canine bone marrow tissue-derived mesenchymal stem cell conditioned medium (BMMSC CM) to dogs with SCI. Four client-owned dogs with chronic SCI lasting more than six months underwent neurological and clinical evaluation, MRI imaging and blood tests before being enrolled in this study. All dogs received four intravenous infusions with canine allogenic BMMSC CM within one month. Between the infusions the dogs received comprehensive physiotherapy, which continued for three additional months. No adverse effects or complications were observed during the one, three and six months follow-up periods. Neither blood chemistry panel nor hematology profile showed any significant changes. All dogs were clinically improved as assessed using Olby locomotor scales after one, three and six months of BMMSC CM treatment. Furthermore, goniometric measurements revealed partial improvement in the range of joint motion. Bladder function improved in two disabled dogs. We conclude that multiple delivery of allogenic cell-derived conditioned medium to dogs with chronic SCI is feasible, and it might be clinically beneficial in combination with physiotherapy.

Allotransplantation of adult spinal cord tissues after complete transected spinal cord injury: Long-term survival and functional recovery in canines

Spinal cord injury (SCI), especially complete transected SCI, leads to loss of cells and extracellular matrix and functional impairments. In a previous study, we transplanted adult spinal cord tissues (aSCTs) to replace lost tissues and facilitate recovery in a rat SCI model. However, rodents display considerable differences from human patients in the scale, anatomy and functions of spinal cord systems, and responses after injury. Thus, use of a large animal SCI model is required to examine the repair efficiency of potential therapeutic approaches. In this study, we transplanted allogenic aSCTs from adult dogs to the lesion area of canines after complete transection of the thoracic spinal cord, and investigated the long-term cell survival and functional recovery. To enhance repair efficiency, a growth factor cocktail was added during aSCT transplantation, providing a favorable microenvironment. The results showed that transplantation of aSCTs, in particular with the addition of growth factors, significantly improves locomotor function restoration and increases the number of neurofilament-, microtubule-associated protein 2-, 5-hydroxytryptamine-, choline acetyltransferase- and tyrosine hydroxylase-positive neurons in the lesion area at 6 months post-surgery. In addition, we demonstrated that donor neurons in aSCTs can survive for a long period after transplantation. This study showed for the first time that transplanting aSCTs combined with growth factor supplementation facilitates reconstruction of injured spinal cords, and consequently promotes long lasting motor function recovery in a large animal complete transected SCI model, and therefore could be considered as a possible therapeutic strategy in humans.

A combination of mesenchymal stem cells and scaffolds promotes motor functional recovery in spinal cord injury: a systematic review and meta-analysis

OBJECTIVE

There is controversy about the role of scaffolds as an adjunctive therapy to mesenchymal stem cell (MSC) transplantation in spinal cord injury (SCI). Thus, the authors aimed to design a meta-analysis on preclinical evidence to evaluate the effectiveness of combination therapy of scaffold + MSC transplantation in comparison with scaffolds alone and MSCs alone in improving motor dysfunction in SCI.

METHODS

Electronic databases including Medline, Embase, Scopus, and Web of Science were searched from inception until the end of August 2018. Two independent reviewers screened related experimental studies. Animal studies that evaluated the effectiveness of scaffolds and/or MSCs on motor function recovery following experimental SCI were included. The findings were reported as standardized mean difference (SMD) and 95% confidence interval (CI).

RESULTS

A total of 34 articles were included in the meta-analysis. Analyses show that combination therapy in comparison with the scaffold group alone (SMD 2.00, 95% CI 1.53-2.46, p < 0.0001), the MSCs alone (SMD 1.58, 95% CI 0.84-2.31, p < 0.0001), and the nontreated group (SMD 3.52, 95% CI 2.84-4.20, p < 0.0001) significantly improved motor function recovery. Co-administration of MSCs + scaffolds only in the acute phase of injury (during the first 3 days after injury) leads to a significant recovery compared to scaffold alone (SMD 2.18, p < 0.0001). In addition, the cotransplantation of scaffolds with bone marrow-derived MSCs (SMD 1.99, p < 0.0001) and umbilical cord-derived MSCs (SMD 1.50, p = 0.001) also improved motor function following SCI.

CONCLUSIONS

The findings showed that scaffolds + MSCs is more effective than scaffolds and MSCs alone in improving motor function following SCI in animal models, when used in the acute phase of injury.

Collagen scaffold combined with human umbilical cord-mesenchymal stem cells transplantation for acute complete spinal cord injury

Currently, there is no effective strategy to promote functional recovery after a spinal cord injury. Collagen scaffolds can not only provide support and guidance for axonal regeneration, but can also serve as a bridge for nerve regeneration at the injury site. They can additionally be used as carriers to retain mesenchymal stem cells at the injury site to enhance their effectiveness. Hence, we hypothesized that transplanting human umbilical cord-mesenchymal stem cells on collagen scaffolds would enhance healing following acute complete spinal cord injury. Here, we test this hypothesis through animal studies and a phase I clinical trial. (1) Animal experiments: Models of completely transected spinal cord injury were established in rats and canines by microsurgery. Mesenchymal stem cells derived from neonatal umbilical cord tissue were adsorbed onto collagen scaffolds and surgically implanted at the injury site in rats and canines; the animals were observed after 1 week–6 months. The transplantation resulted in increased motor scores, enhanced amplitude and shortened latency of the motor evoked potential, and reduced injury area as measured by magnetic resonance imaging. (2) Phase I clinical trial: Forty patients with acute complete cervical injuries were enrolled at the Characteristic Medical Center of Chinese People’s Armed Police Force and divided into two groups. The treatment group (n = 20) received collagen scaffolds loaded with mesenchymal stem cells derived from neonatal umbilical cord tissues; the control group (n = 20) did not receive the stem-cell loaded collagen implant. All patients were followed for 12 months. In the treatment group, the American Spinal Injury Association scores and activities of daily life scores were increased, bowel and urinary functions were recovered, and residual urine volume was reduced compared with the pre-treatment baseline. Furthermore, magnetic resonance imaging showed that new nerve fiber connections were formed, and diffusion tensor imaging showed that electrophysiological activity was recovered after the treatment. No serious complication was observed during follow-up. In contrast, the neurological functions of the patients in the control group were not improved over the follow-up period. The above data preliminarily demonstrate that the transplantation of human umbilical cord-mesenchymal stem cells on a collagen scaffold can promote the recovery of neurological function after acute spinal cord injury. In the future, these results need to be confirmed in a multicenter, randomized controlled clinical trial with a larger sample size. The clinical trial was approved by the Ethics Committee of the Characteristic Medical Center of Chinese People’s Armed Police Force on February 3, 2016 (approval No. PJHEC-2016-A8). All animal experiments were approved by the Ethics Committee of the Characteristic Medical Center of Chinese People’s Armed Police Force on May 20, 2015 (approval No. PJHEC-2015-D5).

Characterization and immunogenicity of bone marrow-derived mesenchymal stem cells under osteoporotic conditions

Mesenchymal stem cells (MSCs) are characterized by their multilineage potential and low immunogenicity. However, the properties of MSCs under pathological conditions are unclear. The current study investigated the differentiation potential and immunological characteristics of bone marrow-derived MSCs from ovariectomized-osteoporotic rats (OP-BMSCs). Although the expression of cell morphology- and stemness-related surface markers was similar between OP-BMSCs and BMSCs from healthy rats (H-BMSCs), the proliferation rate was significantly decreased compared with that of H-BMSCs. Regarding multilineage potential, osteogenesis and chondrogenesis abilities of OP-BMSCs decreased, but the adipogenesis ability was significantly enhanced compared with that of H-BMSCs. As expected, decreased osteogenesis following osteogenic induction resulted in reduced expression of β-catenin, osteocalcin, and runt-related transcription factor 2 in OP-BMSCs. Remarkably, the expression of the co-stimulatory proteins CD40 and CD80 was significantly higher, whereas the expression of the negative co-stimulatory molecule programmed cell death ligand 1 was significantly lower in the OP-BMSCs than that in H-BMSCs. Consequently, H-BMSCs inhibited the proliferation and secretion of inflammatory cytokines from anti-CD3 antibody-activated T cells, whereas OP-BMSCs did not. These results indicate that decreased osteogenesis and increased immunogenicity of OP-BMSCs contribute to bone loss in osteoporosis.

LncRNA Neat1 mediates miR-124-induced activation of Wnt/β-catenin signaling in spinal cord neural progenitor cells

BACKGROUND

Emerging evidence suggests that miR-124 performs important biological functions in neural stem cells (NSCs); it regulates NSC behavior and promotes the differentiation of NSCs into neurons, but the exact molecular mechanism remains unknown. And also, the role of miR-124 during spinal cord injury regeneration is unclear.

MATERIALS AND METHODS

In order to explore the function of miR-124 in neural differentiation, the molecular markers (Tuj1, Map2, and GFAP) correlated with the differentiation of NSCs were detected by immunofluorescence staining both in cultured mouse spinal cord progenitor cells (SC-NPCs) and in spinal cord injury (SCI) animal models. The migration ability and apoptosis of cultured SC-NPCs were also evaluated by Transwell migration assay and TUNEL assay. In addition, the relative expression of lnRNA Neat1- and Wnt/β-catenin signaling-related genes were detected by quantitative real-time PCR.

RESULTS

In this study, we revealed that lncRNA Neat1 is involved in regulating Wnt/β-catenin signaling that is activated by miR-124 in SC-NPCs. LncRNA Neat1 was also found to play an important role in regulating neuronal differentiation, apoptosis, and migration of SC-NPCs. Furthermore, we demonstrated that overexpression of miR-124 resulted in elevated Neat1 expression, accompanied with the functional recovery of locomotion in a mouse model of spinal cord injury.

CONCLUSIONS

Our results confirm the therapeutic effectiveness of miR-124 on the functional recovery of injured spinal cord, supporting the rationale and feasibility of miR-124 for spinal cord injury treatment in future clinical therapy. Furthermore, we concluded that the miR-124-Neat1-Wnt/β-catenin signaling axis is involved in regulating the cell function of SC-NPCs, and this may offer novel therapeutic avenues for future treatment of SCI.

Identification and characterization of two morphologically distinct stem cell subpopulations from human urine samples

Urine-derived stem cells (USCs) have shown potentials for the treatment of skeletal and urological disorders. Based on published literature and our own data, USCs consist of heterogeneous populations of cells. In this paper, we identify and characterize two morphologically distinct subpopulations of USCs from human urine samples, named as spindle-shaped USCs (SS-USCs) and rice-shaped USCs (RS-USCs) respectively. The two subpopulations showed similar clone-forming efficiency, while SS-USCs featured faster proliferation, higher motility, and greater potential for osteogenic and adipogenic differentiation, RS-USCs showed greater potential for chondrogenic differentiation. POU5F1 was strongly expressed in both subpopulations, but MYC was weakly expressed. Both subpopulations showed similar patterns of CD24, CD29, CD34, CD44, CD73, CD90 and CD105 expression, while a higher percentage of RS-USCs were positive for CD133. SS-USCs were positive for VIM, weakly positive for SLC12A1 and UMOD, and negative for KRT18, NPHS1, AQP1 and AQP2, indicating a renal mesenchyme origin; while RS-USCs are positive for VIM, partially positive for KRT18, NPHS1, AQP1, SLC12A1 and UMOD, and negative for AQP2, indicating a nephron tubule origin. The above results can facilitate understanding of the biological characteristics of subpopulations of USCs, and provide a basis for further research and applications of such cells.

Role and prospects of regenerative biomaterials in the repair of spinal cord injury

Axonal junction defects and an inhibitory environment after spinal cord injury seriously hinder the regeneration of damaged tissues and neuronal functions. At the site of spinal cord injury, regenerative biomaterials can fill cavities, deliver curative drugs, and provide adsorption sites for transplanted or host cells. Some regenerative biomaterials can also inhibit apoptosis, inflammation and glial scar formation, or further promote neurogenesis, axonal growth and angiogenesis. This review summarized a variety of biomaterial scaffolds made of natural, synthetic, and combined materials applied to spinal cord injury repair. Although these biomaterial scaffolds have shown a certain therapeutic effect in spinal cord injury repair, there are still many problems to be resolved, such as product standards and material safety and effectiveness.

Different functional bio-scaffolds share similar neurological mechanism to promote locomotor recovery of canines with complete spinal cord injury

Many studies have shown that rodents exhibit a certain degree of spontaneous motor function recovery even if they suffer from spinal cord complete transection injury. However, the characteristics of spontaneous locomotor recovery and its associated neurobiological mechanisms are unclear. In this study, we observed that spontaneous locomotor function recovery of hind limbs could also be detected in a canine thoracic (T8) spinal cord complete transection model. In addition, the spontaneous locomotor recovery of canines could be further promoted by chronic implantation of Taxol- or human bone marrow mesenchymal stem cell-modified bio-scaffolds. Moreover, functional bio-scaffolds implantation promoted locomotor outcome could be significantly weakened (drop to the spontaneous recovery level) but not totally abolished by resection in the lesion site. The neurological mechanism for functional bio-scaffolds improved locomotor outcome was primarily dependent on the formation of neuronal bridging but not the long-distance regeneration of descending motor axons throughout the lesion gap. Besides that, we found that spontaneously achieved locomotor recovery of hind limbs was unable to be weaken by repetitive resection of the lesion area, indicating the mechanism for spontaneous locomotor recovery was independent on functional neurological bridging throughout the lesion gap.

Polymer scaffolds facilitate spinal cord injury repair

During the past decades, improving patient neurological recovery following spinal cord injury (SCI) has remained a challenge. An effective treatment for SCI would not only reduce fractured elements and isolate developing local glial scars to promote axonal regeneration but also ameliorate secondary effects, including inflammation, apoptosis, and necrosis. Three-dimensional (3D) scaffolds provide a platform in which these mechanisms can be addressed in a controlled manner. Polymer scaffolds with favorable biocompatibility and appropriate mechanical properties have been engineered to minimize cicatrization, customize drug release, and ensure an unobstructed space to promote cell growth and differentiation. These properties make polymer scaffolds an important potential therapeutic platform. This review highlights the recent developments in polymer scaffolds for SCI engineering. STATEMENT OF SIGNIFICANCE: How to improve the efficacy of neurological recovery after spinal cord injury (SCI) is always a challenge. Tissue engineering provides a promising strategy for SCI repair, and scaffolds are one of the most important elements in addition to cells and inducing factors. The review highlights recent development and future prospects in polymer scaffolds for SCI therapy. The review will guide future studies by outlining the requirements and characteristics of polymer scaffold technologies employed against SCI. Additionally, the peculiar properties of polymer materials used in the therapeutic process of SCI also have guiding significance to other tissue engineering approaches.