Pro-angiogenic scaffold-free Bio three-dimensional conduit developed from human induced pluripotent stem cell-derived mesenchymal stem cells promotes peripheral nerve regeneration

Application of mesenchymal stem/stromal cells in periodontal regeneration: Opportunities and challenges

Guided tissue regeneration (GTR) has been widely used in the periodontal treatment of intrabony and furcation defects for nearly four decades. The treatment outcomes have shown effectiveness in reducing pocket depth, improving attachment gain and bone filling in periodontal tissue. Although applying GTR could reconstruct the periodontal tissue, the surgical indications are relatively narrow, and some complications and race ethic problems bring new challenges. Therefore, it is challenging to achieve a consensus concerning the clinical benefits of GTR. With the appearance of stem cell-based regenerative medicine, mesenchymal stem/stromal cells (MSCs) have been considered a promising cell resource for periodontal regeneration. In this review, we highlight preclinical and clinical periodontal regeneration using MSCs derived from distinct origins, including non-odontogenic and odontogenic tissues and induced pluripotent stem cells, and discuss the transplantation procedures, therapeutic mechanisms, and concerns to evaluate the effectiveness of MSCs.

Chiral MoS2@BC fibrous membranes selectively promote peripheral nerve regeneration

BACKGROUND

Molybdenum disulfide (MoS2) has excellent physical and chemical properties. Further, chiral MoS2 (CMS) exhibits excellent chiroptical and enantioselective effects, and the enantioselective properties of CMS have been studied for the treatment of neurodegenerative diseases. Intriguingly, left- and right-handed materials have different effects on promoting the differentiation of neural stem cells into neurons. However, the effect of the enantioselectivity of chiral materials on peripheral nerve regeneration remains unclear.

METHODS

In this study, CMS@bacterial cellulose (BC) scaffolds were fabricated using a hydrothermal approach. The CMS@BC films synthesized with L-2-amino-3-phenyl-1-propanol was defined as L-CMS. The CMS@BC films synthesized with D-2-amino-3-phenyl-1-propanol was defined as D-CMS. The biocompatibility of CMS@BC scaffolds and their effect on Schwann cells (SCs) were validated by cellular experiments. In addition, these scaffolds were implanted in rat sciatic nerve defect sites for three months.

RESULTS

These chiral scaffolds displayed high hydrophilicity, good mechanical properties, and low cytotoxicity. Further, we found that the L-CMS scaffolds were superior to the D-CMS scaffolds in promoting SCs proliferation. After three months, the scaffolds showed good biocompatibility in vivo, and the nerve conducting velocities of the L-CMS and D-CMS scaffolds were 51.2 m/s and 26.8 m/s, respectively. The L-CMS scaffolds showed a better regenerative effect than the D-CMS scaffolds. Similarly, the sciatic nerve function index and effects on the motor and electrophysiological functions were higher for the L-CMS scaffolds than the D-CMS scaffolds. Finally, the axon diameter and myelin sheath thickness of the regenerated nerves were improved in the L-CMS group.

CONCLUSION

We found that the CMS@BC can promote peripheral nerve regeneration, and in general, the L-CMS group exhibited superior repair performance. Overall, the findings of this study reveal that CMS@BC can be used as a chiral nanomaterial nerve scaffold for peripheral nerve repair.

Establishing stable and highly osteogenic hiPSC-derived MSCs for 3D-printed bone graft through microenvironment modulation by CHIR99021-treated osteocytes

Human induced pluripotent stem cell (hiPSC)-derived mesenchymal stem cells (iMSCs) are ideal candidates for the production of standardised and scalable bioengineered bone grafts. However, stable induction and osteogenic differentiation of iMSCs pose challenges in the industry. We developed a precise differentiation method to produce homogeneous and fully differentiated iMSCs. In this study, we established a standardised system to prepare iMSCs with increased osteogenic potential and improved bioactivity by introducing a CHIR99021 (C91)-treated osteogenic microenvironment (COOME). COOME enhances the osteogenic differentiation and mineralisation of iMSCs via canonical Wnt signalling. Global transcriptome analysis and co-culturing experiments indicated that COOME increased the pro-angiogenesis/neurogenesis activity of iMSCs. The superior osteogenic differentiation and mineralisation abilities of COOME-treated iMSCs were also confirmed in a Bio3D module generated using a polycaprolactone (PCL) and cell-integrated 3D printing (PCI3D) system, which is the closest model to in vivo research. This COOME-treated iMSCs differentiation system offers a new perspective for generating highly osteogenic, bioactive, and anatomically matched grafts for clinical applications.

Statement of significance

Although human induced pluripotent stem cell-derived MSCs (iMSCs) are ideal seed cells for synthetic bone implants, the challenges of stable induction and osteogenic differentiation hinder their clinical application. This study established a standardised system for the scalable preparation of iMSCs with improved osteogenic potential by combining our precise iMSC differentiation method with the CHIR99021 (C91)-treated osteocyte osteogenic microenvironment (COOME) through the activation of canonical Wnt signalling. Moreover, COOME upregulated the pro-angiogenic and pro-neurogenic capacities of iMSCs, which are crucial for the integration of implanted bone grafts. The superior osteogenic ability of COOME-treated iMSCs was confirmed in Bio3D modules generated using PCL and cell-integrated 3D printing systems, highlighting their functional potential in vivo. This study contributes to tissue engineering by providing insights into the functional differentiation of iMSCs for bone regeneration.

Multichannel Conduits with Fascicular Complementation: Significance in Long Segmental Peripheral Nerve Injury

Despite the advances in tissue engineering approaches, reconstruction of long segmental peripheral nerve defects remains unsatisfactory. Although autologous grafts with proper fascicular complementation have shown meaningful functional recovery according to the Medical Research Council Classification (MRCC), the lack of donor nerve for such larger defect sizes (>30 mm) has been a serious clinical issue. Further clinical use of hollow nerve conduits is limited to bridging smaller segmental defects of denuded nerve ends (<30 mm). Recently, bioinspired multichannel nerve guidance conduits (NGCs) gained attention as autograft substitutes as they mimic the fascicular connective tissue microarchitecture in promoting aligned axonal outgrowth with desirable innervation for complete sensory and motor function restoration. This review outlines the hierarchical organization of nerve bundles and their significance in the sensory and motor functions of peripheral nerves. This review also emphasizes the major challenges in addressing the longer nerve defects with the role of fascicular arrangement in the multichannel nerve guidance conduits and the need for fascicular matching to accomplish complete functional restoration, especially in treating long segmental nerve defects. Further, currently available fabrication strategies in developing multichannel nerve conduits and their inconsistency in existing preclinical outcomes captured in this review would seed a new process in designing an ideal larger nerve conduit for peripheral nerve repair.

Potential Application of Orofacial MSCs in Tissue Engineering Nerve Guidance for Peripheral Nerve Injury Repair

Injury to the peripheral nerve causes potential loss of sensory and motor functions, and peripheral nerve repair (PNR) remains a challenging endeavor. The current clinical methods of nerve repair, such as direct suture, autografts, and acellular nerve grafts (ANGs), exhibit their respective disadvantages like nerve tension, donor site morbidity, size mismatch, and immunogenicity. Even though commercially available nerve guidance conduits (NGCs) have demonstrated some clinical successes, the overall clinical outcome is still suboptimal, especially for nerve injuries with a large gap (≥ 3 cm) due to the lack of biologics. In the last two decades, the combination of advanced tissue engineering technologies, stem cell biology, and biomaterial science has significantly advanced the generation of a new generation of NGCs incorporated with biological factors or supportive cells, including mesenchymal stem cells (MSCs), which hold great promise to enhance peripheral nerve repair/regeneration (PNR). Orofacial MSCs are emerging as a unique source of MSCs for PNR due to their neural crest-origin and easy accessibility. In this narrative review, we have provided an update on the pathophysiology of peripheral nerve injury and the properties and biological functions of orofacial MSCs. Then we have highlighted the application of orofacial MSCs in tissue engineering nerve guidance for PNR in various preclinical models and the potential challenges and future directions in this field.

A Cartilaginous Construct with Bone Collar Exerts Bone-Regenerative Property Via Rapid Endochondral Ossification

Three-dimensional clumps of mesenchymal stem cells (MSCs)/extracellular matrix (ECM) complexes (C-MSCs) can be implanted into tissue defects with no artificial scaffolds. In addition, the cellular properties and characteristics of the ECM in C-MSCs can be regulated in vitro. Most bone formation in the developmental and healing process is due to endochondral ossification, which occurs after bone collar formation surrounding cartilage derived from MSCs. Thus, to develop a rapid and reliable bone-regenerative cell therapy, the present study aimed to generate cartilaginous tissue covered with a mineralized bone collar-like structure from human C-MSCs by combining chondrogenic and osteogenic induction. Human bone marrow-derived MSCs were cultured in xeno-free/serum-free (XF) growth medium. Confluent cells that formed cellular sheets were detached from the culture plate using a micropipette tip. The floating cellular sheet contracted to round clumps of cells (C-MSCs). C-MSCs were maintained in XF-chondro-inductive medium (CIM) and XF-osteo-inductive medium (OIM). The biological and bone-regenerative properties of the generated cellular constructs were assessed in vitro and in vivo. C-MSCs cultured in CIM/OIM formed cartilaginous tissue covered with a mineralized matrix layer, whereas CIM treatment alone induced cartilage with no mineralization. Transplantation of the cartilaginous tissue covered with a mineralized matrix induced more rapid bone reconstruction via endochondral ossification in the severe combined immunodeficiency mouse calvarial defect model than that of cartilage generated using only CIM. These results highlight the potential of C-MSC culture in combination with CIM/OIM to generate cartilage covered with a bone collar-like structure, which can be applied for novel bone-regenerative cell therapy.

Clinical Trials of Stem Cell Therapy in Japan: The Decade of Progress under the National Program

Stem cell therapy is a current world-wide topic in medical science. Various therapies have been approved based on their effectiveness and put into practical use. In Japan, research and development-related stem cell therapy, generally referred to as regenerative medicine, has been led by the government. The national scheme started in 2002, and support for the transition to clinical trials has been accelerating since 2011. Of the initial 18 projects that were accepted in the budget for preclinical research, 15 projects have begun clinical trials so far. These include the transplantation of retinal, cardiac, and dopamine-producing cells differentiated from human induced pluripotent stem (iPS) cells and hepatocyte-like cells differentiated from human embryonic stem (ES) cells. The distinctive feature of the stem cell research in Japan is the use of iPS cells. A national framework was also been set-up to attain the final goal: health insurance coverage. Now, insurance covers cell transplantation therapies for the repair and recovery of damaged skin, articular cartilage, and stroke as well as therapies introduced from abroad, such as allogeneic mesenchymal stem cells for graft-versus-host disease and chimeric antigen receptor-T (CAR-T) cell therapy. To prepare this review, original information was sought from Japanese authentic websites, which are reliable but a little hard to access due to the fact of multiple less-organized databases and the language barrier. Then, each fact was corroborated by citing its English version or publication in international journals as much as possible. This review provides a summary of progress over the past decade under the national program and a state-of-the-art factual view of research activities, government policy, and regulation in Japan for the realization of stem cell therapy.

Induction of functional xeno-free MSCs from human iPSCs via a neural crest cell lineage

Mesenchymal stem/stromal cells (MSCs) are adult multipotent stem cells. Here, we induced MSCs from human induced pluripotent stem cells (iPSCs) via a neural crest cell (NCC) lineage under xeno-free conditions and evaluated their in vivo functions. We modified a previous MSC induction method to work under xeno-free conditions. Bovine serum albumin-containing NCC induction medium and fetal bovine serum-containing MSC induction medium were replaced with xeno-free medium. Through our optimized method, iPSCs differentiated into MSCs with high efficiency. To evaluate their in vivo activities, we transplanted the xeno-free-induced MSCs (XF-iMSCs) into mouse models for bone and skeletal muscle regeneration and confirmed their regenerative potency. These XF-iMSCs mainly promoted the regeneration of surrounding host cells, suggesting that they secrete soluble factors into affected regions. We also found that the peroxidasin and IGF2 secreted by the XF-iMSCs partially contributed to myotube differentiation. These results suggest that XF-iMSCs are important for future applications in regenerative medicine.

Nerve regeneration using the Bio 3D nerve conduit fabricated with spheroids

Autologous nerve grafting is the gold standard method for peripheral nerve injury with defects. Artificial nerve conduits have been developed to prevent morbidity at the harvest site. However, the artificial conduit regeneration capacity is not sufficient. A Bio 3D printer is technology that creates three-dimensional tissue using only cells. Using this technology, a three-dimensional nerve conduit (Bio 3D nerve conduit) was created from several cell spheroids. We reported the first application of the Bio 3D nerve conduit for peripheral nerve injury. A Bio 3D nerve conduit that was created from several cells promotes peripheral nerve regeneration. The Bio 3D nerve conduit may be useful clinically to treat peripheral nerve defects.

GAP-43 Induces the Differentiation of Bone Marrow-Derived Mesenchymal Stem Cells into Retinal Ganglial-Like Cells

Optic neuritis (ON) is a common neurological disease, and the transplant of retinal ganglion cells (RGCs) has been thought as a promising strategy for improving the injury of the optic nerve system. Bone mesenchymal stem cells (BMSCs) have the potential to differentiate into neural cells. Several studies have indicated that GAP-43 is related with the regeneration of nerve cells, while the effect of GAP-43 on inducing BMSC differentiation remains unclear. In this study, the BMSCs were separated from the rats and identified with flow cytometry assay. The GAP-43 expressed vectors were transfected into the BMSCs, and the biomarkers of RGCs such as PAX6, LHX2, and ATOH7 were used to observe by qRT-PCR. Moreover, the effect of GAP-43-induced BMSCs (G-BMSCs) on ON improvement was also verified with rat models, and the activity of MAPK pathway was measured with western blot. Here, it was found that GAP-43 could obviously promote the differentiation of BMSCs, and increased PAX6, LHX2, ATOH7, BRN3A, and BRN3B were observed in the process of cell differentiation. Moreover, it was also found that G-BMSCs significantly increased the abundances of NFL and NFM in G-BMSCs, and GAP-43 could also enhance the activity of MAPK pathways in BMSCs. Therefore, this study suggested that GAP-43 could induce the differentiation of bone marrow-derived mesenchymal stem cells into retinal ganglial cells.

Multi-Factorial Nerve Guidance Conduit Engineering Improves Outcomes in Inflammation, Angiogenesis and Large Defect Nerve Repair

Nerve guidance conduits (NGCs) are sub-optimal for long-distance injuries with inflammation and poor vascularization related to poor axonal repair. This study used a multi-factorial approach to create an optimized biomaterial NGC to address each of these issues. Through stepwise optimization, a collagen-chondroitin-6-sulphate (Coll-CS) biomaterial was functionalized with extracellular matrix (ECM) components; fibronectin, laminin 1 and laminin 2 (FibL1L2) in specific ratios. A snap-cooled freeze-drying process was then developed with optimal pore architecture and alignment to guide axonal bridging. Culture of adult rat dorsal root ganglia on NGCs demonstrated significant improvements in inflammation, neurogenesis and angiogenesis in the specific Fib:L1:L2 ratio of 1:4:1. In clinically relevant, large 15 mm rat sciatic nerve defects, FibL1L2-NGCs demonstrated significant improvements in axonal density and angiogenesis compared to unmodified NGCs with functional equivalence to autografts. Therefore, a multiparameter ECM-driven strategy can significantly improve axonal repair across large defects, without exogenous cells or growth factors.

Clumps of Mesenchymal Stem Cells/Extracellular Matrix Complexes Generated with Xeno-Free Chondro-Inductive Medium Induce Bone Regeneration via Endochondral Ossification

Three-dimensional clumps of mesenchymal stem cells (MSCs)/extracellular matrix (ECM) complexes (C-MSCs) can be transplanted into tissue defect site with no artificial scaffold. Importantly, most bone formation in the developing process or fracture healing proceeds via endochondral ossification. Accordingly, this present study investigated whether C-MSCs generated with chondro-inductive medium (CIM) can induce successful bone regeneration and assessed its healing process. Human bone marrow-derived MSCs were cultured with xeno-free/serum-free (XF) growth medium. To obtain C-MSCs, confluent cells that had formed on the cellular sheet were scratched using a micropipette tip and then torn off. The sheet was rolled to make a round clump of cells. The cell clumps, i.e., C-MSCs, were maintained in XF-CIM. C-MSCs generated with XF-CIM showed enlarged round cells, cartilage matrix, and hypertrophic chondrocytes genes elevation in vitro. Transplantation of C-MSCs generated with XF-CIM induced successful bone regeneration in the SCID mouse calvaria defect model. Immunofluorescence staining for human-specific vimentin demonstrated that donor human and host mouse cells cooperatively contributed the bone formation. Besides, the replacement of the cartilage matrix into bone was observed in the early period. These findings suggested that cartilaginous C-MSCs generated with XF-CIM can induce bone regeneration via endochondral ossification.

In vivo regeneration of rat laryngeal cartilage with mesenchymal stem cells derived from human induced pluripotent stem cells via neural crest cells

The laryngotracheal cartilage is a cardinal framework for the maintenance of the airway for breathing, which occasionally requires reconstruction. Because hyaline cartilage has a poor intrinsic regenerative ability, various regenerative approaches have been attempted to regenerate laryngotracheal cartilage. The use of autologous mesenchymal stem cells (MSCs) for cartilage regeneration has been widely investigated. However, long-term culture may limit proliferative capacity. Human-induced pluripotent stem cell-derived MSCs (iMSCs) can circumvent this problem due to their unlimited proliferative capacity. This study aimed to investigate the efficacy of iMSCs in the regeneration of thyroid cartilage in immunodeficient rats. Herein, we induced iMSCs through neural crest cell intermediates. For the relevance to prospective future clinical application, induction was conducted under xeno-free/serum-free conditions. Then, clumps fabricated from an iMSC/extracellular matrix complex (C-iMSC) were transplanted into thyroid cartilage defects in immunodeficient rats. Histological examinations revealed cartilage-like regenerated tissue and human nuclear antigen (HNA)-positive surviving transplanted cells in the regenerated lesion. HNA-positive cells co-expressed SOX9, and type II collagen was identified around HNA-positive cells. These results indicated that the transplanted C-iMSCs promoted thyroid cartilage regeneration and some of the iMSCs differentiated into chondrogenic lineage cells. Induced MSCs may be a promising candidate cell therapy for human laryngotracheal reconstruction.

Long-Term Outcome of Sciatic Nerve Regeneration Using Bio3D Conduit Fabricated from Human Fibroblasts in a Rat Sciatic Nerve Model

Previously, we developed a Bio3D conduit fabricated from human fibroblasts and reported a significantly better outcome compared with artificial nerve conduit in the treatment of rat sciatic nerve defect. The purpose of this study is to investigate the long-term safety and nerve regeneration of Bio3D conduit compared with treatments using artificial nerve conduit and autologous nerve transplantation.We used 15 immunodeficient rats and randomly divided them into three groups treated with Bio3D (n = 5) conduit, silicon tube (n = 5), and autologous nerve transplantation (n = 5). We developed Bio3D conduits composed of human fibroblasts and bridged the 5 mm nerve gap created in the rat sciatic nerve. The same procedures were performed to bridge the 5 mm gap with a silicon tube. In the autologous nerve group, we removed the 5 mm sciatic nerve segment and transplanted it. We evaluated the nerve regeneration 24 weeks after surgery.Toe dragging was significantly better in the Bio3D group (0.20 ± 0.28) than in the silicon group (0.6 ± 0.24). The wet muscle weight ratios of the tibial anterior muscle of the Bio3D group (79.85% ± 5.47%) and the autologous nerve group (81.74% ± 2.83%) were significantly higher than that of the silicon group (66.99% ± 3.51%). The number of myelinated axons and mean myelinated axon diameter was significantly higher in the Bio3D group (14708 ± 302 and 5.52 ± 0.44 μm) and the autologous nerve group (14927 ± 5089 and 6.04 ± 0.85 μm) than the silicon group (7429 ± 1465 and 4.36 ± 0.21 μm). No tumors were observed in any of the rats in the Bio3D group at 24 weeks after surgery.The Bio3D group showed significantly better nerve regeneration and there was no significant difference between the Bio3D group and the nerve autograft group in all endpoints.

Development of pluripotent stem cell-based human tenocytes

Human pluripotent stem cells (PSCs) are used as a platform for therapeutic purposes such as cell transplantation therapy and drug discovery. Another motivation for studying PSCs is to understand human embryogenesis and development. All cell types that make up the body tissues develop through defined trajectories during embryogenesis. For example, paraxial mesoderm is considered to differentiate into several cell types including skeletal muscle cells, chondrocytes, osteocytes, dermal fibroblasts, and tenocytes. Tenocytes are fibroblast cells that constitute the tendon. The step-wise narrowing fate decisions of paraxial mesoderm in the embryo have been modeled in vitro using PSCs; however, deriving tenocytes from human-induced PSCs and their application in cell therapy have long been challenging. PSC-derived tenocytes can be used for a source of cell transplantation to treat a damaged or ruptured tendon due to injury, disorder, or aging. In this review, we discuss the latest research findings on the use of PSCs for studying the biology of tenocyte development and their application in therapeutic settings.