Engineering tubular bone using mesenchymal stem cell sheets and coral particles

Sustainably cultured coral scaffold supports human bone marrow mesenchymal stromal cell osteogenesis

The current gold standard grafting material is autologous bone due to its osteoinductive and osteoconductive properties. Autograft harvesting results in donors site morbidity. Coral scaffolds offer a natural autograft alternative, sharing the density and porosity of human bone. This study investigated the biocompatibility and osteogenic potential of a novel, sustainably grown Pocillopora scaffold with human bone marrow-derived mesenchymal stromal cells (MSCs). The coral-derived scaffold displays a highly textured topography, with concavities of uniform size and a high calcium carbonate content. Large scaffold samples exhibit compressive and diametral tensile strengths in the range of trabecular bone, with strengths likely increasing for smaller particulate samples. Following the in vitro seeding of MSCs adjacent to the scaffold, the MSCs remained viable, continued proliferating and metabolising, demonstrating biocompatibility. The seeded MSCs densely covered the coral scaffold with organized, aligned cultures with a fibroblastic morphology. In vivo coral scaffolds with MSCs supported earlier bone and blood vessel formation as compared to control constructs containing TCP-HA and MSCs. This work characterized a novel, sustainably grown coral scaffold that was biocompatible with MSCs and supports their in vivo osteogenic differentiation, advancing the current repertoire of biomaterials for bone grafting.

Engineering of axially vascularized bone tissue using natural coral scaffold and osteogenic bone marrow mesenchymal stem cell sheets

INTRODUCTION

Blood supply remains one of the obstacles to large bone tissue engineering. This study aimed to generate vascularized bone tissue by inducing axial vascularization into a construct combining natural coral scaffold and a bone marrow mesenchymal stem cells (BMSCs) sheet.

MATERIAL AND METHODS

Isolated BMSCs were cultured to form an osteogenic cell sheet using a continuous culture method. Natural coral scaffolds were prepared into customized shape with a cylinder of 20 mm length, 8 mm in outer diameter and 5 mm in inner diameter. Then, the freed superficial inferior epigastric vessel of rabbits was first wrapped with a cell sheet, and then inserted into the central passage of the scaffold, after being wrapped with another cell sheet, the complexes were implanted subcutaneously into a rabbit groin area. In contrast, the sheet-scaffold construct that implanted into groin subcutaneous area of the other side of the same rabbit with the distal end of the blood vessel was ligated, which was considered as control. New bone and vascularization formation were evaluated at 12 weeks postoperatively.

RESULTS

The volume of new bone formation and amount of capillary infiltration in the vascular circulation group were significantly greater than that in the vascular ligation group, which suggested that insertion of axial vessels could significantly promote angiogenesis and osteogenesis of the tissue-engineered bone.

CONCLUSIONS

These findings indicate that inserting an arteriovenous bundle into the constructs of mesenchymal stem cell sheet and coral has great potential for clinical applications to repair large bone defects.

Scaffold-free human mesenchymal stem cell construct geometry regulates long bone regeneration

Biomimetic bone tissue engineering strategies partially recapitulate development. We recently showed functional restoration of femoral defects using scaffold-free human mesenchymal stem cell (hMSC) condensates featuring localized morphogen presentation with delayed in vivo mechanical loading. Possible effects of construct geometry on healing outcome remain unclear. Here, we hypothesized that localized presentation of transforming growth factor (TGF)-β1 and bone morphogenetic protein (BMP)-2 to engineered hMSC tubes mimicking femoral diaphyses induces endochondral ossification, and that TGF-β1 + BMP-2-presenting hMSC tubes enhance defect healing with delayed in vivo loading vs. loosely packed hMSC sheets. Localized morphogen presentation stimulated chondrogenic priming/endochondral differentiation in vitro. Subcutaneously, hMSC tubes formed cartilage templates that underwent bony remodeling. Orthotopically, hMSC tubes stimulated more robust endochondral defect healing vs. hMSC sheets. Tissue resembling normal growth plate was observed with negligible ectopic bone. This study demonstrates interactions between hMSC condensation geometry, morphogen bioavailability, and mechanical cues to recapitulate development for biomimetic bone tissue engineering.

Herberg et al. previously showed functional healing of femoral defects using scaffold-free human mesenchymal stem cell (hMSC) condensates with localized morphogen presentation. In this study, they report the importance of the tubular geometry of MSC condensates in long bone regeneration. Unlike loosely packed hMSC sheets, only hMSC tubes induced regenerate tissue partially resembling normal growth plate.

Mesenchymal stem cell-derived extracellular matrix (mECM): a bioactive and versatile scaffold for musculoskeletal tissue engineering

Mesenchymal stem cell-derived extracellular matrix (mECM) has received increased attention in the fields of tissue engineering and scaffold-assisted regeneration. mECM exhibits many unique characteristics, such as robust bioactivity, biocompatibility, ease of use, and the potential for autologous tissue engineering. As the use of mECM has increased in musculoskeletal tissue engineering, it should be noted that mECM generated from current methods has inherited insufficiencies, such as low mechanical properties and lack of internal architecture. In this review, we first summarize the development and use of mECM as a scaffold for musculoskeletal tissue regeneration and highlight our current progress on moving this technology toward clinical application. Then we review recent methods to improve the properties of mECM that will overcome current weaknesses. Lastly, we propose future studies that will pave the road for mECM application in regenerating tissues in humans.

Osteogenesis and bone remodeling: A focus on growth factors and bioactive peptides

Bone is one of the most frequently transplanted tissues. The bone structure and its physiological function and stem cells biology were known to be closely related to each other for many years. Bone is considered a home to the well-known systems of postnatal mesenchymal stem cells (MSCs). These bone resident MSCs provide a range of growth factors (GF) and cytokines to support cell growth following injury. These GFs include a group of proteins and peptides produced by different cells which are regulators of important cell functions such as division, migration, and differentiation. GF signaling controls the formation and development of the MSCs condensation and plays a critical role in regulating osteogenesis, chondrogenesis, and bone/mineral homeostasis. Thus, a combination of both MSCs and GFs receives high expectations in regenerative medicine, particularly in bone repair applications. It is known that the delivery of exogenous GFs to the non-union bone fracture site remarkably improves healing results. Here we present updated information on bone tissue engineering with a specific focus on GF characteristics and their application in cellular functions and tissue healing. Moreover, the interrelation of GFs with the damaged bone microenvironment and their mechanistic functions are discussed.

3D Bioprinting Strategies for the Regeneration of Functional Tubular Tissues and Organs

It is difficult to fabricate tubular-shaped tissues and organs (e.g., trachea, blood vessel, and esophagus tissue) with traditional biofabrication techniques (e.g., electrospinning, cell-sheet engineering, and mold-casting) because these have complicated multiple processes. In addition, the tubular-shaped tissues and organs have their own design with target-specific mechanical and biological properties. Therefore, the customized geometrical and physiological environment is required as one of the most critical factors for functional tissue regeneration. 3D bioprinting technology has been receiving attention for the fabrication of patient-tailored and complex-shaped free-form architecture with high reproducibility and versatility. Printable biocomposite inks that can facilitate to build tissue constructs with polymeric frameworks and biochemical microenvironmental cues are also being actively developed for the reconstruction of functional tissue. In this review, we delineated the state-of-the-art of 3D bioprinting techniques specifically for tubular tissue and organ regeneration. In addition, this review described biocomposite inks, such as natural and synthetic polymers. Several described engineering approaches using 3D bioprinting techniques and biocomposite inks may offer beneficial characteristics for the physiological mimicry of human tubular tissues and organs.

Local Application of Semaphorin 3A Combined with Adipose-Derived Stem Cell Sheet and Anorganic Bovine Bone Granules Enhances Bone Regeneration in Type 2 Diabetes Mellitus Rats

Bone tissue regeneration is considered to be the optimal solution for bone loss. However, diabetic patients have a greater risk of poor bone healing or bone grafting failure than nondiabetics. The purpose of this study was to investigate the influence of the complexes of an adipose-derived stem cell sheet (ASC sheet) and Bio-Oss® bone granules on bone healing in type 2 diabetes mellitus (T2DM) rats with the addition of semaphorin 3A (Sema3A). The rat ASC sheets showed stronger osteogenic ability than ASCs in vitro, as indicated by the extracellular matrix mineralization and the expression of osteogenesis-related genes at mRNA level. An ASC sheet combined with Bio-Oss® bone granules promoted bone formation in T2DM rats as indicated by microcomputed tomography (micro-CT) and histological analysis. In addition, Sema3A promoted the osteogenic differentiation of ASC sheets in vitro and local injection of Sema3A promoted T2DM rats' calvarial bone regeneration based on ASC sheet and Bio-Oss® bone granule complex treatment. In conclusion, the local injection of Sema3A and the complexes of ASC sheet and Bio-Oss® bone granules could promote osseous healing and are potentially useful to improve bone healing for T2DM patients.

Mesenchymal stem cell sheets: a new cell-based strategy for bone repair and regeneration

Mesenchymal stem cells (MSCs), a class of adult stem cells, are considered a promising source for bone regeneration. Although combining MSCs with biomaterial scaffolds offers an interesting clinical strategy for bone tissue engineering, the presence of the scaffolds could induce an undesirable effect on cell-cell interactions. Moreover, before the application of scaffold materials in bone tissue reconstruction, cells must be manipulated with proteolytic enzymes, such as trypsin or dispase that degrade extracellular matrix (ECM) molecules and cell surface proteins, which can result in the cell damage and loss of cellular activity. Therefore, the development of alternative strategies for bone regeneration is required to solve these problems. Recently, a novel tissue engineering technology named 'cell sheet' has been efficaciously utilized in the regeneration of bone, corneal, cardiac, tracheal and periodontal ligament-like tissues. The cell sheet is a layer of cells, which contains intact ECM and cell surface proteins such as growth factor receptors, ion channels and cell-to-cell junction proteins. MSC sheets can be easily fabricated by layering the recovered cell sheets without any scaffolds or complicated manipulation. This review summarizes the current state of the literature regarding the use of MSCs to produce cell sheets and assesses their applicability in bone tissue regeneration and repair.

Synthetic and Marine-Derived Porous Scaffolds for Bone Tissue Engineering

Bone is a vascularized and connective tissue. The cortical bone is the main part responsible for the support and protection of the remaining systems and organs of the body. The trabecular spongy bone serves as the storage of ions and bone marrow. As a dynamic tissue, bone is in a constant remodelling process to adapt to the mechanical demands and to repair small lesions that may occur. Nevertheless, due to the increased incidence of bone disorders, the need for bone grafts has been growing over the past decades and the development of an ideal bone graft with optimal properties remains a clinical challenge. This review addresses the bone properties (morphology, composition, and their repair and regeneration capacity) and puts the focus on the potential strategies for developing bone repair and regeneration materials. It describes the requirements for designing a suitable scaffold material, types of materials (polymers, ceramics, and composites), and techniques to obtain the porous structures (additive manufacturing techniques like robocasting or derived from marine skeletons) for bone tissue engineering applications. Overall, the main objective of this review is to gather the knowledge on the materials and methods used for the production of scaffolds for bone tissue engineering and to highlight the potential of natural porous structures such as marine skeletons as promising alternative bone graft substitute materials without any further mineralogical changes, or after partial or total transformation into calcium phosphate.

Different Bone Healing Effects of Undifferentiated and Osteogenic Differentiated Mesenchymal Stromal Cell Sheets in Canine Radial Fracture Model

Cell sheets technology is being available for fracture healing. This study was performed to clarify bone healing mechanism of undifferentiated (UCS) and osteogenic (OCS) differentiated mesenchymal stromal cell (MSC) sheets in the fracture model of dogs. UCS and OCS were harvested at 10 days of culture. Transverse fractures at the radius of six beagle dogs were assigned into three groups (n = 4 in each group) i.e. UCS, OCS and control. The fractures were fixed with a 2.7 mm locking plate and six screws. Cell sheets were wrapped around the fracture site. Bones were harvested 8 weeks after operation, then scanned by micro-computed tomography (micro-CT) and analyzed histopathologically. The micro-CT revealed different aspects of bone regeneration among the groups. The percentages of external callus volume out of total bone volume in control, UCS, and OCS groups were 42.1, 13.0 and 4.9% (p < 0.05) respectively. However, the percentages of limbs having connectivity of gaps were 25, 12.5 and 75% respectively. In histopathological assessments, OCS group showed well organized and mature woven bone with peripheral cartilage at the fracture site, whereas control group showed cartilage formation without bone maturation or ossification at the fracture site. Meanwhile, fracture site was only filled with fibrous connective tissue without endochondral ossification and bone formation in UCS group. It was suggested that the MSC sheets reduced the quantity of external callus, and OCS induced the primary bone healing.

A Concise Review on the Use of Mesenchymal Stem Cells in Cell Sheet-Based Tissue Engineering with Special Emphasis on Bone Tissue Regeneration

The integration of stem cell technology and cell sheet engineering improved the potential use of cell sheet products in regenerative medicine. This review will discuss the use of mesenchymal stem cells (MSCs) in cell sheet-based tissue engineering. Besides their adhesiveness to plastic surfaces and their extensive differentiation potential in vitro, MSCs are easily accessible, expandable in vitro with acceptable genomic stability, and few ethical issues. With all these advantages, they are extremely well suited for cell sheet-based tissue engineering. This review will focus on the use of MSC sheets in osteogenic tissue engineering. Potential application techniques with or without scaffolds and/or grafts will be discussed. Finally, the importance of osteogenic induction of these MSC sheets in orthopaedic applications will be demonstrated.

Is there a role of coral bone substitutes in bone repair?

Xenogeneic bone graft materials are an alternative to autologous bone grafting. Among such implants, coralline-derived bone grafts substitutes have a long track record as safe, biocompatible and osteoconductive graft materials. In this review, we present the available literature surrounding their use with special focus on the commercially available graft materials. Corals thanks to their chemical and structural characteristics similar to those of the human cancellous bone have shown great potential but clinical data presented to date is ambiguous with both positive and negative outcomes reported. Correct formulation and design of the graft to ensure adequate osteo-activity and resorption appear intrinsic to a successful outcome.

Scaffold-Based Delivery of Bone Marrow Mesenchymal Stem Cell Sheet Fragments Enhances New Bone Formation In Vivo

PURPOSE

Stem cell therapy is becoming a potent strategy to shorten the consolidation time and reduce potential complications during distraction osteogenesis (DO). However, the conventional local injection or scaffold-based delivery of bone marrow mesenchymal stem cell (BMSC) suspension deprives the cells of their endogenous extracellular matrix, which might dampen cell differentiation and tissue regeneration after implantation. Therefore, in our study, a BMSC sheet was established and was then minced into fragments and loaded onto a hydroxyapatite (HA) scaffold for grafting.

MATERIALS AND METHODS

The purified and characterized BMSCs were grown into a cell sheet, and bone formation and mineralization capacity, as well as the cell sheet composition, were analyzed. Afterward, the in vivo osteogenic ability of cell sheet fragments (CSFs) was evaluated in immunocompromised mouse and rabbit models of DO.

RESULTS

The BMSC sheet exhibited higher alkaline phosphatase activity than osteogenic cell suspension cultures. Alkaline phosphatase activity and mineral particles in the cell sheet increased further after osteogenic induction. Moreover, calcium and phosphorus were present only in the osteogenic cell sheet, along with the common elements carbon, oxygen, chlorine, sodium, and sulfur, as indicated by x-ray photoelectron spectroscopy analysis. In a mouse model, the CSF-HA complex was injected subcutaneously. Micro-computed tomography analysis showed that the osteogenic CSF-HA complex led to a considerably higher bone volume than the BMSC-HA or CSF-HA complex. The osteogenic CSF-HA specimens showed increased angiogenesis and deposition of type I collagen compared with the non-osteogenic CSF-HA or BMSC-HA specimens. Moreover, the osteogenic CSF-HA markedly improved bone consolidation and increased bone mass in DO rabbits.

CONCLUSIONS

Collectively, the incorporation of osteogenic BMSC sheets into HA particles greatly promoted bone regeneration, which offers therapeutic alternatives for DO.

Chm-1 gene-modified bone marrow mesenchymal stem cells maintain the chondrogenic phenotype of tissue-engineered cartilage

BACKGROUND

Marrow mesenchymal stem cells (MSCs) can differentiate into specific phenotypes, including chondrocytes, and have been widely used for cartilage tissue engineering. However, cartilage grafts from MSCs exhibit phenotypic alternations after implantation, including matrix calcification and vascular ingrowth.

METHODS

We compared chondromodulin-1 (Chm-1) expression between chondrocytes and MSCs. We found that chondrocytes expressed a high level of Chm-1. We then adenovirally transduced MSCs with Chm-1 and applied modified cells to engineer cartilage in vivo.

RESULTS

A gross inspection and histological observation indicated that the chondrogenic phenotype of the tissue-engineered cartilage graft was well maintained, and the stable expression of Chm-1 was detected by immunohistological staining in the cartilage graft derived from the Chm-1 gene-modified MSCs.

CONCLUSIONS

Our findings defined an essential role for Chm-1 in maintaining chondrogenic phenotype and demonstrated that Chm-1 gene-modified MSCs may be used in cartilage tissue engineering.

Prospect of Stem Cells in Bone Tissue Engineering: A Review

Mesenchymal stem cells (MSCs) have been the subject of many studies in recent years, ranging from basic science that looks into MSCs properties to studies that aim for developing bioengineered tissues and organs. Adult bone marrow-derived mesenchymal stem cells (BM-MSCs) have been the focus of most studies due to the inherent potential of these cells to differentiate into various cell types. Although, the discovery of induced pluripotent stem cells (iPSCs) represents a paradigm shift in our understanding of cellular differentiation. These cells are another attractive stem cell source because of their ability to be reprogramed, allowing the generation of multiple cell types from a single cell. This paper briefly covers various types of stem cell sources that have been used for tissue engineering applications, with a focus on bone regeneration. Then, an overview of some recent studies making use of MSC-seeded 3D scaffold systems for bone tissue engineering has been presented. The emphasis has been placed on the reported scaffold properties that tend to improve MSCs adhesion, proliferation, and osteogenic differentiation outcomes.

Utility of tricalcium phosphate and osteogenic matrix cell sheet constructs for bone defect reconstruction

AIM: To determine the effects of transplanting osteogenic matrix cell sheets and beta-tricalcium phosphate (TCP) constructs on bone formation in bone defects.

METHODS: Osteogenic matrix cell sheets were prepared from bone marrow stromal cells (BMSCs), and a porous TCP ceramic was used as a scaffold. Three experimental groups were prepared, comprised of TCP scaffolds (1) seeded with BMSCs; (2) wrapped with osteogenic matrix cell sheets; or (3) both. Constructs were implanted into a femoral defect model in rats and bone growth was evaluated by radiography, histology, biochemistry, and mechanical testing after 8 wk.

RESULTS: In bone defects, constructs implanted with cell sheets showed callus formation with segmental or continuous bone formation at 8 wk, in contrast to TCP seeded with BMSCs, which resulted in bone non-union. Wrapping TCP constructs with osteogenic matrix cell sheets increased their osteogenic potential and resulting bone formation, compared with conventional bone tissue engineering TCP scaffolds seeded with BMSCs. The compressive stiffness (mean ± SD) values were 225.0 ± 95.7, 30.0 ± 11.5, and 26.3 ± 10.6 MPa for BMSC/TCP/Sheet constructs with continuous bone formation, BMSC/TCP/Sheet constructs with segmental bone formation, and BMSC/TCP constructs, respectively. The compressive stiffness of BMSC/TCP/Sheet constructs with continuous bone formation was significantly higher than those with segmental bone formation and BMSC/TCP constructs.

CONCLUSION: This technique is an improvement over current methods, such as TCP substitution, and is useful for hard tissue reconstruction and inducing earlier bone union in defects.

Osteoblastic mesenchymal stem cell sheet combined with Choukroun platelet-rich fibrin induces bone formation at an ectopic site

AIMS

To analyze the effects of platelet-rich fibrin (PRF) on mesenchymal stem cells (MSCs) in vitro and investigate in vivo bone formation by MSC sheets with PRF.

MATERIALS AND METHODS

Cell proliferation and expression of osteogenesis-related genes within MSC sheets were assessed upon exposure to PRF from the same donors. We then injected MSC sheet fragments with or without PRF subcutaneously in nude mice and assessed bone formation by micro-computed tomography and histological analyses.

RESULTS

PRF significantly stimulated MSC proliferation and osteogenesis in vitro. MSC sheets injected with or without PRF formed new bone, but those with PRF produced significantly more and denser bone.

CONCLUSIONS

MSC sheets can be used to generate tissue engineered bone upon injection, and PRF increases the osteogenic capacity of MSC sheets in vitro and in vivo.

Scleractinium coral aquaculture skeleton: a possible 3D scaffold for cell cultures and bone tissue engineering

Cytocompatibility of 5 coral aquaculture skeleton species derived from two families (Acroporidae and Pocilloporidae) was studied over the course of in vitro culturing in continuous human fibroblast culture by the MMT test. Biocompatibility and capacity of scaffold to "transfer" cell cultures (specifically, multipotent mesenchymal stromal cells) to sites of implantation were studied in vivo by subcutaneous implantation of skeletal fragments to rats. All coral skeleton aquaculture specimens were cytocompatible (nontoxic and with surface matrix characteristics satisfactory for cells), biocompatible, and could be tried as 3D matrices for bone tissue engineering.