Use of isolated mature osteoblasts in abundance acts as desired-shaped bone regeneration in combination with a modified poly-DL-lactic-co-glycolic acid (PLGA)-collagen sponge

Biomimetic Polymer-Based Engineered Scaffolds for Improved Stem Cell Function

Scaffolds are considered promising materials for tissue engineering applications due to their unique physiochemical properties. The high porosity and adequate mechanical properties of the scaffolds facilitate greater cell adhesion, proliferation, and differentiation. Stem cells are frequently applied in tissue engineering applications due to their excellent potential. It has been noted that cell functions are profoundly affected by the nature of the extracellular matrix (ECM). Naturally derived ECM contains the bioactive motif that also influences the immune response of the organism. The properties of polymer scaffolds mean they can resemble the native ECM and can regulate cellular responses. Various techniques such as electrospinning and 3D printing, among others, are frequently used to fabricate polymer scaffolds, and their cellular responses are different with each technique. Furthermore, enhanced cell viability, as well as the differentiation ability of stem cells on the surface of scaffolds, opens a fascinating approach to the formation of ECM-like environments for tissue engineering applications.

Biomaterials for the Delivery of Growth Factors and Other Therapeutic Agents in Tissue Engineering Approaches to Bone Regeneration

Bone fracture followed by delayed or non-union typically requires bone graft intervention. Autologous bone grafts remain the clinical "gold standard". Recently, synthetic bone grafts such as Medtronic's Infuse Bone Graft have opened the possibility to pharmacological and tissue engineering strategies to bone repair following fracture. This clinically-available strategy uses an absorbable collagen sponge as a carrier material for recombinant human bone morphogenetic protein 2 (rhBMP-2) and a similar strategy has been employed by Stryker with BMP-7, also known as osteogenic protein-1 (OP-1). A key advantage to this approach is its "off-the-shelf" nature, but there are clear drawbacks to these products such as edema, inflammation, and ectopic bone growth. While there are clinical challenges associated with a lack of controlled release of rhBMP-2 and OP-1, these are among the first clinical examples to wed understanding of biological principles with biochemical production of proteins and pharmacological principles to promote tissue regeneration (known as regenerative pharmacology). After considering the clinical challenges with such synthetic bone grafts, this review considers the various biomaterial carriers under investigation to promote bone regeneration. This is followed by a survey of the literature where various pharmacological approaches and molecular targets are considered as future strategies to promote more rapid and mature bone regeneration. From the review, it should be clear that pharmacological understanding is a key aspect to developing these strategies.

Circulating miRNAs as diagnostic biomarkers for adolescent idiopathic scoliosis

The aetiology of adolescent idiopathic scoliosis (AIS) has been linked to many factors, such as asymmetric growth, neuromuscular condition, bone strength and genetic background. Recently, epigenetic factors have been proposed as contributors of AIS physiopathology, but information about the molecular mechanisms and pathways involved is scarce. Regarding epigenetic factors, microRNAs (miRNAs) are molecules that contribute to gene expression modulation by regulating important cellular pathways. We herein used Next-Generation Sequencing to discover a series of circulating miRNAs detected in the blood samples of AIS patients, which yielded a unique miRNA biomarker signature that diagnoses AIS with high sensitivity and specificity. We propose that these miRNAs participate in the epigenetic control of signalling pathways by regulating osteoblast and osteoclast differentiation, thus modulating the genetic background of AIS patients. Our study yielded two relevant results: 1) evidence for the deregulated miRNAs that participate in osteoblast/osteoclast differentiation mechanisms in AIS; 2) this miRNA-signature can be potentially used as a clinical tool for molecular AIS diagnosis. Using miRNAs as biomarkers for AIS diagnostics is especially relevant since miRNAs can serve for early diagnoses and for evaluating the positive effects of applied therapies to therefore reduce the need of high-risk surgical interventions.

Bone Regeneration using Silk Hydroxyapatite Hybrid Composite in a Rat Alveolar Defect Model

Background: To overcome the limited source of autogenous bone in bone grafting, many efforts have been made to find bone substitutes. The use of hybrid composites of silk and hydroxyapatite to simulate natural bone tissue can overcome the softness and brittleness of the individual components. Methods: Critical-sized, 7 x 4 x 1.5 mm alveolar defects were created surgically in 36 Sprague-Dawley rats. Three treatment groups were tested: an empty defect group (group I), a silk fibrin scaffold group (group II), and a hydroxyapatite-conjugated silk fibrin scaffold group (group III). New bone formation was assessed using computed tomography and histology at 4, 8, and 12 weeks, and semi-quantitative western blot analysis was done to confirm bone protein formation at 12weeks. Statistical analysis of new bone formation was done using the Kruskal-Wallis test. Results: Radiomorphometric volume analysis revealed that new bone formation was 64.5% in group I, 77.4% in group II, and 84.8% in group III (p=0.027) at 12 weeks. Histologically, the osteoid tissues were surrounded by osteoblasts not only at the border of the bone defect but in the center of the scaffold implanted area in group III from week 8 on. Semi-quantitative western blotting revealed that osteocalcin expression in group III was 1.8 times higher than group II and 2.6 times higher than group I. Conclusions: New bone formation was higher in hybrid scaffolds. Both osteoconduction at the defect margin and osteoinduction at the center of the defect were confirmed. There were no detected complications related to foreign body implantation.

Functional and histological evidence for the targeted therapy using biocompatible polycaprolactone beads and autologous myoblasts in a dog model of fecal incontinence

BACKGROUND

Injection of bulking agents into the anal canal is limited by several factors, including biological resorption, particle migration, and ongoing degradation of the injected bulking agent.

OBJECTIVE

We investigated whether an injection of polycaprolactone beads containing autologous myoblasts could improve sphincter function in a dog model of fecal incontinence.

DESIGN

The control sham surgery group underwent skin incision around the anal sphincter (n = 5). Fecal incontinence was induced by resecting 25% of the posterior internal/external anal sphincter in another 10 dogs. After 1 month of sphincter injury, dogs were then treated with (n = 5) or without (n = 5) polycaprolactone beads containing PKH-26-labeled autologous myoblasts.

SETTING

This study was conducted at the department of surgery in collaboration with the department of advanced materials.

OUTCOME MEASURES

Three months after injection treatment, the resting and contractile pressure differences of the anal sphincter were compared, and histopathological studies were performed.

RESULTS

The anal pressures in untreated dogs were significantly lower than those in the sham surgery group (p < 0.05). The resting and contractile pressure differences were higher in treated dogs than in untreated dogs (resting pressure difference: 0.7 ± 0.5 vs -0.6 ± 0.8 mmHg; coefficient of the difference in recovery rate, 0.38; 95% CI, 0.15-0.61, p = 0.001; contractile pressure difference: 1.1 ± 4.2 vs -3.9 ± 2.6 mmHg; coefficient, 1.63; 95% CI, 0.55-2.71, p = 0.003). Immunofluorescent staining confirmed that the myoblasts had differentiated and synthesized myosin heavy chain, as observed in vitro.

LIMITATIONS

This study was limited by the lack of comparison of injecting beads containing autologous myoblasts with injecting myoblasts alone.

CONCLUSION

This study shows that an injection of polycaprolactone beads containing autologous myoblasts may improve anal sphincter function in an animal model of fecal incontinence.

Coadministration of basic fibroblast growth factor-loaded polycaprolactone beads and autologous myoblasts in a dog model of fecal incontinence

PURPOSE

Basic fibroblastic growth factor (bFGF), a member of the heparin-binding growth factor family, regulates muscle differentiation. We investigated whether coadministration of autologous myoblasts and bFGF-loaded polycaprolactone beads could improve sphincter recovery in a dog model of fecal incontinence (FI).

METHODS

FI was induced by resecting 25% of the posterior anal sphincter in ten mongrel dogs. One month later, the dogs were randomized to receive either PKH-26-labeled autologous myoblasts alone (M group, five dogs) or autologous myoblasts and bFGF-loaded polycaprolactone beads (MBG group, five dogs). The outcomes included anal manometry, compound muscle action potentials (CMAPs) of the pudendal nerve, and histology.

RESULTS

The increase in anal contractile pressure over 3 months was significantly greater in the MBG group (from 4.85 to 6.83 mmHg) than that in the M group (from 4.94 to 4.25 mmHg), with a coefficient for the difference in recovery rate of 2.672 (95% confidence interval [CI] 0.962 to 4.373, p = 0.002). The change in the CMAP amplitude was also significantly greater in the MBG group (from 0.59 to 1.56 mV) than that in the M group (from 0.81 to 0.67 mV) (coefficient 1.114, 95% CI 0.43 to 1.80, p = 0.001). Labeled cells were detected in 2/5 (40%) and 5/5 (100%) dogs in the M and MBG groups, respectively.

CONCLUSION

Coadministration of bFGF-loaded PCL beads and autologous myoblasts improved the recovery of sphincter function in a dog model of FI and had better outcomes than cell-based therapy alone.

Physicochemical properties and applications of poly(lactic-co-glycolic acid) for use in bone regeneration

Poly(lactic-co-glycolic acid) (PLGA) is the most often used synthetic polymer within the field of bone regeneration owing to its biocompatibility and biodegradability. As a consequence, a large number of medical devices comprising PLGA have been approved for clinical use in humans by the American Food and Drug Administration. As compared with the homopolymers of lactic acid poly(lactic acid) and poly(glycolic acid), the co-polymer PLGA is much more versatile with regard to the control over degradation rate. As a material for bone regeneration, the use of PLGA has been extensively studied for application and is included as either scaffolds, coatings, fibers, or micro- and nanospheres to meet various clinical requirements.

OstemiR: a novel panel of microRNA biomarkers in osteoblastic and osteocytic differentiation from mesencymal stem cells

MicroRNAs (miRNAs) are small RNA molecules of 21–25 nucleotides that regulate cell behavior through inhibition of translation from mRNA to protein, promotion of mRNA degradation and control of gene transcription. In this study, we investigated the miRNA expression signatures of cell cultures undergoing osteoblastic and osteocytic differentiation from mesenchymal stem cells (MSC) using mouse MSC line KUSA-A1 and human MSCs. Ninety types of miRNA were quantified during osteoblastic/osteocytic differentiation in KUSA-A1 cells utilizing miRNA PCR arrays. Coincidently with mRNA induction of the osteoblastic and osteocytic markers, the expression levels of several dozen miRNAs including miR-30 family, let-7 family, miR-21, miR-16, miR-155, miR-322 and Snord85 were changed during the differentiation process. These miRNAs were predicted to recognize osteogenic differentiation-, stemness-, epinegetics-, and cell cycle-related mRNAs, and were thus designated OstemiR. Among those OstemiR, the miR-30 family was classified into miR-30b/c and miR-30a/d/e groups on the basis of expression patterns during osteogenesis as well as mature miRNA structures. In silico prediction and subsequent qRT-PCR in stable miR-30d transfectants clarified that context-dependent targeting of miR-30d on known regulators of bone formation including osteopontin/spp1, lifr, ccn2/ctgf, ccn1/cyr61, runx2, sox9 as well as novel key factors including lin28a, hnrnpa3, hspa5/grp78, eed and pcgf5. In addition, knockdown of human OstemiR miR-541 increased Osteopontin/SPP1 expression and calcification in hMSC osteoblastic differentiation, indicating that miR-541 is a negative regulator of osteoblastic differentiation. These observations indicate stage-specific roles of OstemiR especially miR-541 and the miR-30 family on novel targets in osteogenesis.

Regulating synthetic gene networks in 3D materials

Combining synthetic biology and materials science will enable more advanced studies of cellular regulatory processes, in addition to facilitating therapeutic applications of engineered gene networks. One approach is to couple genetic inducers into biomaterials, thereby generating 3D microenvironments that are capable of controlling intrinsic and extrinsic cellular events. Here, we have engineered biomaterials to present the genetic inducer, IPTG, with different modes of activating genetic circuits in vitro and in vivo. Gene circuits were activated in materials with IPTG embedded within the scaffold walls or chemically linked to the matrix. In addition, systemic applications of IPTG were used to induce genetic circuits in cells encapsulated into materials and implanted in vivo. The flexibility of modifying biomaterials with genetic inducers allows for patterned placement of these inducers that can be used to generate distinct patterns of gene expression. Together, these genetically interactive materials can be used to characterize genetic circuits in environments that more closely mimic cells' natural 3D settings, to better explore complex cell-matrix and cell-cell interactions, and to facilitate therapeutic applications of synthetic biology.

High-strength silk protein scaffolds for bone repair

Biomaterials for bone tissue regeneration represent a major focus of orthopedic research. However, only a handful of polymeric biomaterials are utilized today because of their failure to address critical issues like compressive strength for load-bearing bone grafts. In this study development of a high compressive strength (~13 MPa hydrated state) polymeric bone composite materials is reported, based on silk protein-protein interfacial bonding. Micron-sized silk fibers (10-600 µm) obtained utilizing alkali hydrolysis were used as reinforcement in a compact fiber composite with tunable compressive strength, surface roughness, and porosity based on the fiber length included. A combination of surface roughness, porosity, and scaffold stiffness favored human bone marrow-derived mesenchymal stem cell differentiation toward bone-like tissue in vitro based on biochemical and gene expression for bone markers. Further, minimal in vivo immunomodulatory responses suggested compatibility of the fabricated silk-fiber-reinforced composite matrices for bone engineering applications.

Mechanical improvements to reinforced porous silk scaffolds

Load-bearing porous biodegradable scaffolds are required to engineer functional tissues such as bone. Mechanical improvements to porogen leached scaffolds prepared from silk proteins were systematically studied through the addition of silk particles in combination with silk solution concentration, exploiting interfacial compatibility between the two components. Solvent solutions of silk up to 32 w/v % were successfully prepared in hexafluoroisopropanol (HFIP) for the study. The mechanical properties of the reinforced silk scaffolds correlated to the material density and matched by a power law relationship, independent of the ratio of silk particles to matrix. These results were similar to the relationships previously shown for cancellous bone. From these data we conclude that the increased mechanical properties were due to a densification effect and not due to the inclusion of stiffer silk particles into the softer silk matrix. A continuous interface between the silk matrix and the silk particles, as well as homogeneous distribution of the silk particles within the matrix was observed. Furthermore, we note that the roughness of the pore walls was controllable by varying the ratio of the particles matrix, providing a route to control topography. The rate of proteolytic hydrolysis of the scaffolds decreased with increase in mass of silk used in the matrix and with increasing silk particle content.

Polymeric Scaffolds in Tissue Engineering Application: A Review

Current strategies of regenerative medicine are focused on the restoration of pathologically altered tissue architectures by transplantation of cells in combination with supportive scaffolds and biomolecules. In recent years, considerable interest has been given to biologically active scaffolds which are based on similar analogs of the extracellular matrix that have induced synthesis of tissues and organs. To restore function or regenerate tissue, a scaffold is necessary that will act as a temporary matrix for cell proliferation and extracellular matrix deposition, with subsequent ingrowth until the tissues are totally restored or regenerated. Scaffolds have been used for tissue engineering such as bone, cartilage, ligament, skin, vascular tissues, neural tissues, and skeletal muscle and as vehicle for the controlled delivery of drugs, proteins, and DNA. Various technologies come together to construct porous scaffolds to regenerate the tissues/organs and also for controlled and targeted release of bioactive agents in tissue engineering applications. In this paper, an overview of the different types of scaffolds with their material properties is discussed. The fabrication technologies for tissue engineering scaffolds, including the basic and conventional techniques to the more recent ones, are tabulated.

A cell leakproof PLGA-collagen hybrid scaffold for cartilage tissue engineering

A cell leakproof porous poly(DL-lactic-co-glycolic acid) (PLGA)-collagen hybrid scaffold was prepared by wrapping the surfaces of a collagen sponge except the top surface for cell seeding with a bi-layered PLGA mesh. The PLGA-collagen hybrid scaffold had a structure consisting of a central collagen sponge formed inside a bi-layered PLGA mesh cup. The hybrid scaffold showed high mechanical strength. The cell seeding efficiency was 90.0% when human mesenchymal stem cells (MSCs) were seeded in the hybrid scaffold. The central collagen sponge provided enough space for cell loading and supported cell adhesion, while the bi-layered PLGA mesh cup protected against cell leakage and provided high mechanical strength for the collagen sponge to maintain its shape during cell culture. The MSCs in the hybrid scaffolds showed round cell morphology after 4 weeks culture in chondrogenic induction medium. Immunostaining demonstrated that type II collagen and cartilaginous proteoglycan were detected in the extracellular matrices. Gene expression analyses by real-time PCR showed that the genes encoding type II collagen, aggrecan, and SOX9 were upregulated. These results indicated that the MSCs differentiated and formed cartilage-like tissue when being cultured in the cell leakproof PLGA-collagen hybrid scaffold. The cell leakproof PLGA-collagen hybrid scaffolds should be useful for applications in cartilage tissue engineering.

The biodegradability of poly(Pro-Hyp-Gly) synthetic polypeptide and the promotion of a dermal wound epithelialization using a poly(Pro-Hyp-Gly) sponge

Collagens are widely used in medical applications, but animal-derived collagens have several drawbacks, such as low thermal stability, nonspecific cell attachment, and susceptibility to contamination by infectious pathogens, such as prions, which may transfect humans. We have previously reported the chemical synthesis of polypeptides consisting of a Pro-Hyp-Gly sequence and the high thermostability of their triple-helical structure. To clarify the biomaterial characteristics of the poly(Pro-Hyp-Gly) polypeptide, we assessed its biodegradability and its capability for skin regeneration. Eight weeks after implantation, a poly(Pro-Hyp-Gly) freeze-dried sponge embedded subcutaneously into a rat dorsal area degraded at the same rate as Terudermis, which is made from bovine type I atelocollagen and is used as an artificial dermis. Surprisingly, compared with Terudermis, the poly(Pro-Hyp-Gly) sponge significantly promoted epithelialization of a full-thickness wound on a rabbit's ear pad. This chemically synthesized polypeptide may be useful as a scaffold for tissue engineering and tissue regeneration.

Bone tissue engineering with premineralized silk scaffolds

Silk fibroin biomaterials are being explored as novel protein-based systems for cell and tissue culture. In the present study, biomimetic growth of calcium phosphate on porous silk fibroin polymeric scaffolds was explored to generate organic/inorganic composites as scaffolds for bone tissue engineering. Aqueous-derived silk fibroin scaffolds were prepared with the addition of polyaspartic acid during processing, followed by the controlled deposition of calcium phosphate by exposure to CaCl(2) and Na(2)HPO(4). These mineralized protein-composite scaffolds were subsequently seeded with human bone marrow stem cells (hMSC) and cultured in vitro for 6 weeks under osteogenic conditions with or without BMP-2. The extent of osteoconductivity was assessed by cell numbers, alkaline phosphatase and calcium deposition, along with immunohistochemistry for bone-related outcomes. The results suggest increased osteoconductive outcomes with an increase in initial content of apatite and BMP-2 in the silk fibroin porous scaffolds. The premineralization of these highly porous silk fibroin protein scaffolds provided enhanced outcomes for the bone tissue engineering.

Bone Regeneration on Macroporous Aqueous-Derived Silk 3-D Scaffolds

Spinner flask culture under osteogenic conditions was used to study osteogenic outcomes from human bone marrow-derived mesenchymal stem cells (hMSCs) seeded on aqueous-derived porous silk scaffolds. Of particular novelty was the use of larger sized scaffolds (15 mm diameter, 5 mm thick) and large pore sizes ( approximately 900-1 000 micron diameter). Cultures were maintained for 84 d in the spinner flasks and compared to static controls under otherwise similar conditions. The spinner flask cultures demonstrated enhanced cell proliferation compared to static cultures and the improved fluid flow promoted significantly improved osteogenic related outcomes based on elevated alkaline phosphatase (ALP) activity and the deposition of mineralized matrix. The expression of osteogenic differentiation associated markers based on real time PCR also demonstrated increased responses under the dynamic spinner flask culture conditions. Histological analysis showed organized bone-like structures in the constructs cultured in the spinner flasks after 56 d of culture. These structures stained intensely with von Kossa. The combination of improved transport due to spinner flask culture and the use of macroporous 3D aqueous-derived silk scaffolds with large pore sizes resulted in enhanced outcomes related to bone tissue engineering, even with the use of large sized scaffolds in the study. These results suggest the importance of the structure of the silk biomaterial substrate (water vs. solvent based preparation) and large pore sizes in improved bone-like outcomes during dynamic cultivation.

Hyaline cartilage formation and enchondral ossification modeled with KUM5 and OP9 chondroblasts

What is it that defines a bone marrow-derived chondrocyte? We attempted to identify marrow-derived cells with chondrogenic nature and immortality without transformation, defining "immortality" simply as indefinite cell division. KUM5 mesenchymal cells, a marrow stromal cell line, generated hyaline cartilage in vivo and exhibited enchondral ossification at a later stage after implantation. Selection of KUM5 chondroblasts based on the activity of the chondrocyte-specific cis-regulatory element of the collagen alpha2(XI) gene resulted in enhancement of their chondrogenic nature. Gene chip analysis revealed that OP9 cells, another marrow stromal cell line, derived from macrophage colony-stimulating factor-deficient osteopetrotic mice and also known to be niche-constituting cells for hematopoietic stem cells expressed chondrocyte-specific or -associated genes such as type II collagen alpha1, Sox9, and cartilage oligomeric matrix protein at an extremely high level, as did KUM5 cells. After cultured OP9 micromasses exposed to TGF-beta3 and BMP2 were implanted in mice, they produced abundant metachromatic matrix with the toluidine blue stain and formed type II collagen-positive hyaline cartilage within 2 weeks in vivo. Hierarchical clustering and principal component analysis based on microarray data of the expression of cell surface markers and cell-type-specific genes resulted in grouping of KUM5 and OP9 cells into the same subcategory of "chondroblast," that is, a distinct cell type group. We here show that these two cell lines exhibit the unique characteristics of hyaline cartilage formation and enchondral ossification in vitro and in vivo.

Historic and current strategies in bone tissue engineering: do we have a hope in Hench?

Professors Larry Hench and Julia Polak formed the Tissue Engineering and Regenerative Medicine Centre (TERM) at Imperial College London to foster collaborations between biologists and materials scientists. Early work at the center elucidated the biomolecular interactions between primary human osteoblasts and 45S5 Bioglass . As research efforts expanded, the team discovered that the dissolution products of both 45S5 Bioglass and 58S sol-gel bioactive glasses had osteoblastic stimulatory properties. To address the shortage of appropriate cells for bone tissue engineering applications, TERM scientists also demonstrated the differentiation of embryonic stem (ES) cells to osteoblasts when treated with the dissolution products of bioactive glasses. They also found that the soluble factors ascorbic acid, beta -glycerophosphate, and dexamethasone preferentially differentiated ES cells to osteoblasts, and their combination with the dissolution products of bioactive glasses stimulated differentiation even further. Taken together, these results demonstrate the suitability of bioactive glasses as scaffolds for bone tissue engineering as they not only provide an osteoconductive and osteoproductive substrate, but also actively stimulate cells to express appropriate osteoblastic phenotypes. Professor Hench's vision to pioneer regenerative medicine research continues with the aim of developing novel therapeutics to treat musculoskeletal disability.

Mechanism of bone induction by KUSA/A1 cells using atelocollagen honeycomb scaffold

In order to induce new bone formation, mesenchymal stem cells were seeded onto atelocollagen honeycomb scaffold. We evaluated the mechanism of bone induction by KUSA/A1 cells combined with honeycomb atelocollagen scaffold. Scaffold alone, KUSA/A1 cells alone and with scaffold were implanted in the subcutaneous pockets of 4-week-old male SCID mice. The transplants were subjected to radiographical, histological and immunohistochemical examinations after 2 and 4 weeks of implantation. Radiographically, both KUSA/A1 cells alone and KUSA/A1-Scaffold showed some radiopaque areas formation but the latter disclosed a larger amount. Scaffold alone did not show any radiopacity. Histologically, Scaffold alone demonstrated only fibrous connective tissues in the periphery of the scaffold. KUSA/A1 cells alone showed few small islands of new bone formation surrounded by a thin layer of cellular proliferation. On the other hand, KUSA/A1-Scaffold revealed abundant new bone formation as well as cellular proliferation. We also determined the immunolocalization of type I collagen, CD34, Osteocalcin and PCNA in this newly formed bone. Our results indicated that less amount of stem cells are capable to induce the more amount of new bone in tissue engineering. This study support that atelocollagen honeycomb scaffold plays an important role in cellular anchorage and in vessel invasion, giving the precise shape and size for the new bone formation.

Bone-Like Tissue Formation by Three-Dimensional Culture of MG63 Osteosarcoma Cells in Gelatin Hydrogels Using Calcium-Enriched Medium

The aim of this study was to investigate the effect of Ca(2+) concentration in culture medium on the promotion of osteogenesis by MG63 osteoblast-like cells and to prepare bone-like tissues by supplying Ca(2+)-enriched medium to MG63 cells immobilized in three-dimensional gelatin hydrogels. Human osteosarcoma MG63 cells were cultured on tissue culture dish under various Ca(2+) concentrations to evaluate the effect of Ca(2+) concentration on calcium deposition. When Ca(2+) concentration was 8 mM, the maximum calcium deposition was obtained at day 28. Then MG63 cells were entrapped in gelatin hydrogels cross-linked by transglutaminase and cultured for 28 days, either in a standard culture medium or in medium containing 8 mM Ca(2+). Effects of Ca(2+)-enriched medium on osteoblastic phenotype of MG63 cells in gelatin hydrogels were analyzed in terms of cell number, calcium deposition content, and alkaline phosphatase (ALP) activity. The characteristics of calcified gelatin hydrogels were evaluated by x-ray diffraction (XRD), histological analysis, and scanning electron microscopy (SEM). After 28 days of culture, no significant difference in cell numbers was found between the different culture conditions. However, calcium content of gelatin hydrogels with cells cultured in Ca(2+)-enriched media was significantly higher than that of hydrogels with cells cultured in standard Ca(2+) concentration medium. After 14 days of culture, ALP activity of cells cultured in Ca(2+)-enriched media was down-regulated compared with that of cells cultured in standard Ca(2+) concentration media. XRD analysis indicated the formation of hydroxyapatite in gelatin hydrogels cultured in the Ca(2+)-enriched media at day 14, and the XRD pattern of the composite at day 21 was almost similar to that of mouse tibia. Moreover, histological analysis and SEM analysis revealed that cross-sections of hydrogels cultured in Ca(2+)-enriched media had an organic/mineral layer structure analogous to that of mouse tibia.

Biodegradable polymer composite grafts promote the survival and differentiation of retinal progenitor cells

Retinal progenitor cells (RPCs) are multipotent central nervous system precursors that give rise to all of the cell types of the retina during development. Several groups have reported that mammalian RPCs can be isolated and expanded in culture and can differentiate into retinal neurons upon grafting to the mature, diseased eye. However, cell delivery and survival remain formidable obstacles to application of RPCs in a clinical setting. Because biodegradable polymer/progenitor constructs have been shown to be capable of tissue generation in other compartments, we evaluated the survival, migration, and differentiation of RPCs delivered on PLLA/PLGA polymer substrates to the mouse subretinal space and compared these results to conventional injections of RPCs. Polymer composite grafts resulted in a near 10-fold increase in the number of surviving cells after 4 weeks, with a 16-fold increase in cell delivery. Grafted RPCs migrated into the host retina and expressed the mature markers neurofilament-200, glial fibrillary acidic protein, protein kinase C-alpha, recoverin, and rhodopsin. We conclude that biodegradable polymer/progenitor cell composite grafts provide an effective means of increasing progenitor cell survival and overall yield when transplanting to sites within the central nervous system such as the retina.

The State of the Art of Nanobioscience in Japan

This paper reviews a part of the state of the art of nanobioscience in Japan. The importance of combination and integration of interdisciplinary principles is emphasized for the development of nanobioscience. Biomagnetics, biomechanics, nanomachining, self-replicating cell model, neuronal network, drug delivery system, and tissue engineering are discussed.

Efficacy of atelocollagen honeycomb scaffold in bone formation using KUSA/A1 cells

To induce new bone formation, mesenchymal stem cells were seeded onto atelocollagen honeycomb scaffold. We evaluated the efficacy of this scaffold combined with KUSA/A1 cells in vivo. KUSA/A1 cells alone and with atelocollagen were implanted in the subcutaneous pockets of 4-week-old male SCID mice. The transplants were subjected to radiographical, histological, and immunohistochemical examinations after 2 and 4 weeks of implantation. Radiographically, both KUSA/A1 cells alone and KUSA/A1-atelocollagen showed some radiopaque areas formation but the latter disclosed a larger amount. Histologically, KUSA/A1 cells alone showed few small islands of new bone formation surrounded by a thin layer of cellular proliferation. On the other hand, KUSA/A1-atelocollagen revealed abundant new bone formation as well as cellular proliferation. We also determined the immunolocalization of type I collagen, CD34, osteocalcin, osteopontin, and PCNA in this newly formed bone. Our results indicated that collagen scaffold plays an important role allowing vessel formation and cell anchorage, especially through the proliferation and differentiation process in a confined space. This study supports tissue engineering as an alternative for treating different target diseases, such as trauma or congenital defects, and enhances existing therapeutic applications.

A predominantly articular cartilage-associated gene, SCRG1, is induced by glucocorticoid and stimulates chondrogenesis in vitro

OBJECTIVE

Cartilage tissue engineering using multipotential human mesenchymal stem cells (hMSCs) is a promising approach to develop treatment for degenerative joint diseases. A key requirement is that the engineered tissues maintain their hyaline articular cartilage phenotype and not proceed towards hypertrophy. It is noteworthy that osteoarthritic articular cartilage frequently contains limited regions of reparative cartilage, suggesting the presence of bioactive factors with regenerative activity. Based on this idea, we recently performed cDNA microarray analysis to identify genes that are strongly expressed only in articular cartilage and encode secreted gene products. One of the genes that met our criteria was SCRG1. This study aims to analyze SCRG1 function in cartilage development using an in vitro mesenchymal chondrogenesis system.

METHODS

Full-length SCRG1 cDNA was subcloned into pcDNA5 vector, and transfected into hMSCs and murine C3H10T1/2 mesenchymal cells, placed in pellet cultures and micromass cultures, respectively. The cultures were analyzed by reverse transcription-polymerase chain reaction for the expression of SCRG1 and cartilage marker genes, and by histological staining for cartilage phenotype.

RESULTS

Induction of SCRG1 expression was seen during in vitro chondrogenesis, and was dependent on dexamethasone (DEX) known to promote chondrogenesis. Immunohistochemistry revealed that SCRG1 protein was localized to the extracellular matrix. Forced expression of SCRG1 in hMSCs suppressed their proliferation, and stimulated chondrogenesis in C3H10T1/2 cells, confirmed by reduced collagen type I and elevated collagen type IIB expression.

CONCLUSION

These results suggest that SCRG1 is involved in cell growth suppression and differentiation during DEX-dependent chondrogenesis. SCRG1 may be of utility in gene-mediated cartilage tissue engineering.

A three-layered nano-carbonated hydroxyapatite/collagen/PLGA composite membrane for guided tissue regeneration

Functional graded materials (FGM) provided us one new concept for guided tissue regeneration (GTR) membrane design with graded component and graded structure where one face of the membrane is porous thereby allowing cell growth thereon and the opposite face of the membrane is smooth, thereby inhibiting cell adhesion in periodontal therapy. The goal of the present study was to develop a three-layered graded membrane, with one face of 8% nano-carbonated hydroxyapatite/collagen/poly(lactic-co-glycolic acid) (nCHAC/PLGA) porous membrane, the opposite face of pure PLGA non-porous membrane, the middle layer of 4% nCHAC/PLGA as the transition through layer-by-layer casting method. Then the three layers were combined well with each other with flexibility and enough high mechanical strength as membrane because the three layers all contained PLGA polymer that can be easily used for practical medical application. This high biocompatibility and osteoconductivity of this biodegraded composite membrane was enhanced by the nCHAC addition, for the same component and nano-level crystal size with natural bone tissue. The osteoblastic MC3T3-E1 cells were cultured on the three-layered composite membrane, the primary result shows the positive response compared with pure PLGA membrane.

Synthesis of poly(Pro-Hyp-Gly)(n) by direct poly-condensation of (Pro-Hyp-Gly)(n), where n=1, 5, and 10, and stability of the triple-helical structure

Pro-Hyp-Gly is a characteristic amino acid sequence found in fibrous collagens, and (Pro-Hyp-Gly)(10), which has been widely used as a collagen-model peptide, forms a stable triple-helical structure. Here, we synthesized polypeptides consisting of the Pro-Hyp-Gly sequence by direct poly-condensation of (Pro-Hyp-Gly)(n), where n=1, 5, and 10, using 1-hydroxybenzotriazole and 1-ethyl-3-(3-dimethyl-aminopropyl)-carbodiimide hydrochloride in both phosphate buffer (pH=7.4) and dimethylsulfoxide (DMSO) solutions for 48 h at 20 degrees C. The reaction of (Pro-Hyp-Gly)(5) and (Pro-Hyp-Gly)(10) in DMSO successfully gave polypeptides with molecular weights over 10,000, whereas low molecular weight products were obtained by reaction in phosphate buffer (pH=7.4). In contrast, Pro-Hyp-Gly at a concentration of 50 mg/mL in phosphate buffer (pH=7.4) gave polypeptides with molecular weights over 10,000. The Fourier transform infrared (FTIR) and (1)H nuclear magnetic resonance (NMR) spectra of poly(Pro-Hyp-Gly)(10) revealed that the polymerization of (Pro-Hyp-Gly)(10) described in this report had no side reactions. Each polypeptide obtained shows a collagen-like triple-helical structure, and the triple-helical structures of poly(Pro-Hyp-Gly) and poly(Pro-Hyp-Gly)(10) were stable up to T=80 degrees C, which suggests that the high molecular weight promotes stability of the triple-helical structure, in addition to the high Hyp content. Furthermore, transmission electron microscopy (TEM) observations show that poly(Pro-Hyp-Gly)(10) aggregates to form nanofiber-like structures about 10 nm in width, which suggests that a Pro-Hyp-Gly repeating sequence contains enough information for triple-helix formation, and for subsequent nanofiber-like structure formation.

Repair of osteochondral defect with tissue-engineered chondral plug in a rabbit model

PURPOSE

The purpose of this study was to evaluate the macroscopic and histologic results of transplanting a tissue-engineered chondral plug made of atelocollagen sponge and PLLA mesh to treat osteochondral defects.

TYPE OF STUDY

Controlled experimental study.

METHODS

Twelve-week-old male Japanese white rabbits were used. Fresh articular cartilage slices were taken from the humeral head, and isolated chondrocytes were embedded in atelocollagen gel which does not have antigenic portions of collagen (2.0 x 10(6) cells/mL). They were seeded on the top of the atelocollagen sponge/PLLA mesh composite and cultured for 2 weeks. The culture medium was changed every 3 days and L-ascorbic acid (50 microg/mL) was added every 2 days. Culturing the composites for 2 weeks produced tissue-engineered chondral plugs. These tissue-engineered chondral plugs (4-mm diameter, 4-mm thick) were transplanted into the osteochondral defects (4 mm diameter, 4 mm deep) in the patellar grooves of the same rabbits from which the chondrocytes had been harvested (the experimental group). In the control group, the defects were treated with the plugs without chondrocytes. The rabbits were killed 4 and 12 weeks after transplantation. The repaired tissues were evaluated macroscopically and histologically, and analyzed immunohistochemically for expression of type II collagen.

RESULTS

Four weeks after transplantation in the experimental group, the defects were partially repaired with cartilage-like tissue with good subchondral bone formation. Twelve weeks after transplantation, the defects were repaired with hyaline cartilage-like tissue densely stained by Safranin O. Well-organized subchondral bone formation was also observed. In the control group, the defects were covered with only soft fibrous tissue at 4 and 12 weeks macroscopically. Immunohistochemically, type II collagen was detected in about 90% of the repaired area. Histologic scores in the experimental group were significantly higher than those in the control group at both 4 and 12 weeks after transplantation.

CONCLUSIONS

This study shows that the defects treated with tissue engineered chondral plug developed type II collagen in about 90% of the repaired area.

CLINICAL RELEVANCE

The transplantation of a tissue-engineered chondral plug will be one option for treating osteochondral defects. The next step in testing our hypothesis is to evaluate the repaired tissue biomechanically and biochemically over a longer period of time.

Membranous osteogenesis system modeled with KUSA-A1 mature osteoblasts

Several stromal cells were established from murine bone marrow cultures. One of the KUSA subclones, KUSA-A1 cells, displays osteogenic characteristics in vitro and in vivo. The calcium deposition, osteocalcin release, and parathyroid hormone (PTH) responsiveness of KUSA-A1 cells indicate that they are mature osteoblasts or osteocytes. Bone had formed in subcutaneous tissue 1 week after subcutaneous injection of cells into immunodeficient mice. The osteogenesis by KUSA-A1 was not mediated by chondrogenesis and thus was considered to be membranous ossification. These unique characteristics of KUSA-A1 cells provide an opportunity to analyze the process of membranous ossification in detail.

Osteogenic differentiation is inhibited and angiogenic expression is enhanced in MC3T3-E1 cells cultured on three-dimensional scaffolds

Osteogenic differentiation of osteoprogenitor cells in three-dimensional (3D) in vitro culture remains poorly understood. Using quantitative real-time RT-PCR techniques, we examined mRNA expression of alkaline phosphatase, osteocalcin, and vascular endothelial growth factor (VEGF) in murine preosteoblastic MC3T3-E1 cells cultured for 48 h and 14 days on conventional two-dimensional (2D) poly(l-lactide-co-glycolide) (PLGA) films and 3D PLGA scaffolds. Differences in VEGF secretion and function between 2D and 3D culture systems were examined using Western blots and an in vitro Matrigel-based angiogenesis assay. Expression of both alkaline phosphatase and osteocalcin in cells cultured on 3D scaffolds was significantly downregulated relative to 2D controls in 48 h and 14 day cultures. In contrast, elevated levels of VEGF expression in 3D culture were noted at every time point in short- and long-term culture. VEGF protein secretion in 3D cultures was triple the amount of secretion observed in 2D controls. Conditioned medium from 3D cultures induced an enhanced level of angiogenic activity, as evidenced by increases in branch points observed in in vitro angiogenesis assays. These results collectively indicate that MC3T3-E1 cells commit to osteogenic differentiation at a slower rate when cultured on 3D PLGA scaffolds and that VEGF is preferentially expressed by these cells when they are cultured in three dimensions.

Combination of hTERT and bmi-1, E6, or E7 induces prolongation of the life span of bone marrow stromal cells from an elderly donor without affecting their neurogenic potential

Murine bone marrow stromal cells differentiate not only into mesodermal derivatives, such as osteocytes, chondrocytes, adipocytes, skeletal myocytes, and cardiomyocytes, but also into neuroectodermal cells in vitro. Human bone marrow stromal cells are easy to isolate but difficult to study because of their limited life span. To overcome this problem, we attempted to prolong the life span of bone marrow stromal cells and investigated whether bone marrow stromal cells modified with bmi-1, hTERT, E6, and E7 retained their differentiated capability, or multipotency. In this study, we demonstrated that the life span of bone marrow stromal cells derived from a 91-year-old donor could be extended and that the stromal cells with an extended life span differentiated into neuronal cells in vitro. We examined the neuronally differentiated cells morphologically, physiologically, and biologically and compared the gene profiles of undifferentiated and differentiated cells. The neuronally differentiated cells exhibited characteristics similar to those of midbrain neuronal progenitors. Thus, the results of this study support the possible use of autologous-cell graft systems to treat central nervous system diseases in geriatric patients.

Influence of macroporous protein scaffolds on bone tissue engineering from bone marrow stem cells

The aim of this study was to investigate the effect of three-dimensional silk fibroin scaffold preparation methods (aqueous and solvent) on osteogenic responses by human bone marrow stem cells (hMSCs). Macroporous 3D protein scaffolds with similar sized pores of 900+/-50 microm were prepared either by an organic solvent process (hexafluoro-2-propanol, HFIP) or an aqueous process. hMSCs were expanded, seeded on the scaffolds, and cultured up to 28 days under static conditions in osteogenic media. hMSCs seeded onto the water-based silk scaffolds showed a significant increase in cell numbers (p<0.01) vs. the HFIP-prepared silk scaffolds. Significantly higher (p<0.01) alkaline phosphatase (ALPase) activity and calcium deposition were apparent after 28 days of culture in the water-based silk scaffolds when compared to the HFIP-derived silk scaffolds. Transcript levels for collagen type I (Col I), ALP, and osteopontin (OP) increased (p<0.05) in the water-based silk scaffolds in comparison to the HFIP-derived materials. At early stages of culture, increased expression of OP and collagen type II (Col II) were also observed in both scaffolds. Expression of Col II, MMP 13, Col I, and OP proteins increased in the water-based silk scaffolds in comparison to the HFIP-derived scaffolds while bone sialoprotein (BSP) proteins increased in the HFIP-derived silk scaffolds in comparison to the water-based scaffolds after 28 days of culture. Histological analysis showed the development of bone-like trabeculae with cuboid cells in an extracellular matrix (ECM) in the water-based silk scaffolds with more organization than in the HFIP-derived material after 28 days of culture. Alcian blue staining demonstrated the presence of proteoglycan in the ECM formed in the water-based scaffolds but not in the HFIP-prepared silk scaffolds. The results suggest that macroporous 3D aqueous-derived silk fibroin scaffolds provide improved bone-related outcomes in comparison to the HFIP-derived systems. These data illustrate the importance of materials processing on biological outcomes, as the same protein, silk fibroin, was used in both preparations.

Embryonic stem cell-derived embryoid bodies in three-dimensional culture system form hepatocyte-like cells in vitro and in vivo

Pluripotent embryonic stem (ES) cells can be a source of hepatocytes for bioartificial livers or transplantation. In this study, embryoid bodies (EBs) were formed from ES cells cultured in polypropylene conical tubes. The EBs were then inserted into a collagen scaffold three-dimensional culture system and stimulated with exogenous growth factors and hormones to induce hepatic histogenesis. The EB-derived cells expressed liver-specific genes, and albumin-positive cells formed cord-like structures that were not present in two-dimensional monolayer culture systems. However, these albumin- positive cells were not cytokeratin 18 positive. Electron microscopy showed immature hepatocyte- like cells having tight junctions, rough endoplasmic reticulum, and intercellular canaliculi. The scaffold including EB-derived hepatocyte-like cells was transplanted into the median lobes of partially hepatectomized nude mice. After 7 and 14 days, cells positive for both albumin and cytokeratin 18 appeared in the transplant and formed clustered aggregates. Thus the collagen scaffold three-dimensional culture system and the liver regeneration environment induced hepatocyte-like cells and hepatic lobule-like aggregates from EBs. Therefore, differentiating EBs in the scaffold culture system may be useful in developing bioartificial livers, secondary livers, and as pharmaceutical models.

Solvent effects on the microstructure and properties of 75/25 poly(D,L-lactide-co-glycolide) tissue scaffolds

Poly(lactide-co-glycolide) (PLGA) is used in many biomedical applications because it is biodegradable, biocompatible, and FDA approved. PLGA can also be processed into porous tissue scaffolds, often through the use of organic solvents. A static light scattering experiment showed that 75/25 PLGA is well solvated in acetone and methylene chloride, but forms aggregates in chloroform. This led to an investigation of whether the mechanical properties of the scaffolds were affected by solvent choice. Porous 75/25 PLGA scaffolds were created with the use of the solvent casting/particulate leaching technique with three different solvents: acetone, chloroform, and methylene chloride. Compression testing resulted in stiffness values of 21.7 +/- 4.8 N/mm for acetone, 18.9 +/- 4.2 N/mm for chloroform, and 30.2 +/- 9.6 N/mm for methylene chloride. Permeability testing found values of 3.9 +/- 1.9 x 10(-12) m2 for acetone, 3.6 +/- 1.3 x 10(-12) m2 for chloroform, and 2.4 +/- 1.0 x 10(-12) m2 for methylene chloride. Additional work was conducted to uncouple polymer/solvent interactions from evaporation dynamics, both of which may affect the scaffold properties. The results suggest that solvent choice creates small but significant differences in scaffold properties, and that the rate of evaporation is more important in affecting scaffold microstructure than polymer/solvent interactions.