Cell sheet injection as a technique of osteogenic supply

Chondroprotective Effects of Chondrogenic Differentiated Adipose-Derived Mesenchymal Stem Cells Sheet on Degenerated Articular Cartilage in an Experimental Rabbit Model

Adipose-derived stem cells (ADSCs) have been studied for many years as a therapeutic option for osteoarthritis (OA); however, their efficacy remains insufficient. Since platelet-rich plasma (PRP) induces chondrogenic differentiation in ADSCs and the formation of a sheet structure by ascorbic acid can increase the number of viable cells, we hypothesized that the injection of chondrogenic cell sheets combined with the effects of PRP and ascorbic acid may hinder the progression of OA. The effects of induction of differentiation by PRP and formation of sheet structure by ascorbic acid on changes in chondrocyte markers (collagen II, aggrecan, Sox9) in ADSCs were evaluated. Changes in mucopolysaccharide and VEGF-A secretion from cells injected intra-articularly in a rabbit OA model were also evaluated. ADSCs treated by PRP strongly chondrocyte markers, including type II collagen, Sox9, and aggrecan, and their gene expression was maintained even after sheet-like structure formation induced by ascorbic acid. In this rabbit OA model study, the inhibition of OA progression by intra-articular injection was improved by inducing chondrocyte differentiation with PRP and sheet structure formation with ascorbic acid in ADSCs.

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.

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.

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.

Calcium Concentration in Culture Medium as a Nondestructive and Rapid Marker of Osteogenesis

Artificial bones made of β-tricalcium phosphate (β-TCP) combined with bone marrow-derived mesenchymal stromal cells (BM-MSCs) are used for effective reconstruction of bone defects caused by genetic defects, traumatic injury, or surgical resection of bone tumors. However, the selection of constructs with high osteogenic potential before implantation is challenging. The purpose of this study was to determine whether the calcium concentration in BM-MSC culture medium can be used as a nondestructive and simple osteogenic marker for selecting tissue-engineered grafts constructed using β-TCP and BM-MSCs. We prepared three cell passages of BM-MSCs derived from three 7-week-old, male Fischer 344 rats; the cells were cultured in osteoinductive medium in the presence of β-TCP for 15 days. The medium was replaced with fresh medium on day 1 in culture and subsequently changed every 48 h; it was collected for measurement of osteocalcin secretion and calcium concentration by enzyme-linked immunosorbent assay and X-ray fluorescence spectrometry, respectively. After cultivation, the constructs were implanted subcutaneously into the backs of recipient rats. Four weeks after implantation, the alkaline phosphatase (ALP) activity and osteocalcin content of the constructs were measured. A strong inverse correlation was observed between the calcium concentration in the medium and the ALP activity and osteocalcin content of the constructs, with Pearson's correlation coefficients of 0.92 and 0.90, respectively. These results indicate that tissue-engineered bone with high osteogenic ability can be selected before implantation based on low calcium content of the culture medium, resulting in successful bone formation after implantation. This nondestructive, simple method shows great promise for assessing the osteogenic ability of tissue-engineered bone.

Culturing bone marrow cells with dexamethasone and ascorbic acid improves osteogenic cell sheet structure

Objectives

To assess the structure and extracellular matrix molecule expression of osteogenic cell sheets created via culture in medium with both dexamethasone (Dex) and ascorbic acid phosphate (AscP) compared either Dex or AscP alone.

Methods

Osteogenic cell sheets were prepared by culturing rat bone marrow stromal cells in a minimal essential medium (MEM), MEM with AscP, MEM with Dex, and MEM with Dex and AscP (Dex/AscP). The cell number and messenger (m)RNA expression were assessed in vitro, and the appearance of the cell sheets was observed after mechanical retrieval using a scraper. β-tricalcium phosphate (β-TCP) was then wrapped with the cell sheets from the four different groups and subcutaneously implanted into rats.

Results

After mechanical retrieval, the osteogenic cell sheets from the MEM, MEM with AscP, and MEM with Dex groups appeared to be fragmented or incomplete structures. The cell sheets cultured with Dex/AscP remained intact after mechanical retrieval, without any identifiable tears. Culture with Dex/AscP increased the mRNA and protein expression of extracellular matrix proteins and cell number compared with those of the other three groups. More bridging bone formation was observed after transplantation of the β-TCP scaffold wrapped with cell sheets cultured with Dex/AscP, than in the other groups.

Conclusions

These results suggest that culture with Dex/AscP improves the mechanical integrity of the osteogenic cell sheets, allowing retrieval of the confluent cells in a single cell sheet structure. This method may be beneficial when applied in cases of difficult tissue reconstruction, such as nonunion, bone defects, and osteonecrosis.

Cite this article: M. Akahane, T. Shimizu, T. Kira, T. Onishi, Y. Uchihara, T. Imamura, Y. Tanaka. Culturing bone marrow cells with dexamethasone and ascorbic acid improves osteogenic cell sheet structure. Bone Joint Res 2016;5:569–576. DOI: 10.1302/2046-3758.511.BJR-2016-0013.R1.

Osteogenesis of cryopreserved osteogenic matrix cell sheets

Cryopreservation of tissue engineered bone (TEB), whilst maintaining its osteogenic ability, is imperative for large-scale clinical application. We previously reported a novel cell transplantation method, in which bone-marrow-derived mesenchymal stem cells (BMSCs) were cultured to confluence and differentiated down the osteogenic lineage to form osteogenic matrix cell sheets (OMCS). OMCS have high alkaline phosphatase (ALP) activity and osteocalcin (OC) contents and can be easily used for producing TEB. The aim of the present study was to investigate whether TEB produced by cryopreserved OMCS maintains sufficient osteogenic potential in vivo. OMCS were prepared and divided into three groups according to storage period of cryopreservation (fresh (no cryopreservation), 4 week and 12 week cryopreservation groups). OMCS were cryopreserved by storage in freezing medium (Cell Banker 1®) at -80 °C. Cryopreserved OMCSs were rapidly thawed at room temperature and wrapped around Hydroxyapatite (HA) scaffolds prior to implantation into subcutaneous sites in rats, to determine their in vivo bone-forming capability. The constructs were harvested 4 weeks after transplantation and examined histologically and biochemically. Histological analysis of the constructs showed extensive bone formation in the HA pores with high ALP activity and OC content detected in the cryopreservation groups. The present study clearly indicates that cryopreserved/thawed OMCS are still capable of producing mineralized matrix on scaffolds, resulting in bone formation. This cryopreservation technique could be applied for hard tissue reconstruction to ease the cell preparation method prior to time of use.

Secretory osteocalcin as a nondestructive osteogenic marker of tissue-engineered bone

BACKGROUND AND PURPOSE

The constructs of mesenchymal stem cells and ceramics form bone tissue after implantation. Therefore, the constructs can include cultured bone (tissue-engineered bone) as bone grafts. However, the selection of constructs, prior to implantation, with high osteogenic potential is still difficult. We used a rat model to measure the secretory osteocalcin level in culture medium to verify that monitoring osteocalcin levels enables the selection of constructs with high osteogenic potential.

METHODS

We prepared constructs of rat hydroxyapatite/cells and used different cell passages of P-1 and P-3 as well as different cell numbers: 1 × 10(5) and 1 × 10(6) cells/ml suspension. These constructs were cultured for 14 days under osteoinductive or nonosteoinductive conditions and implanted subcutaneously in the recipient rat. Secretory osteocalcin in the culture medium was measured using an enzyme-linked immunosorbent assay system during the culture period until day 14, and the osteocalcin content of the harvested construct at 4 weeks was also measured.

RESULTS AND CONCLUSION

All constructs except the hydroxyapatite/P-3 construct showed abundant bone formation by histology and both high secretory osteocalcin level in the medium and high osteocalcin content after implantation. Our study revealed that secretory osteocalcin level in vitro was related to osteocalcin content in vivo. The study clearly showed that measuring secretory osteocalcin is a nondestructive method of assessing the osteogenic potential of tissue-engineered bone. One can choose tissue-engineered bone with high osteogenic potential by integrating secretory osteocalcin measurement into the process of bone-tissue regeneration.