Trehalose maintains bioactivity and promotes sustained release of BMP-2 from lyophilized CDHA scaffolds for enhanced osteogenesis in vitro and in vivo

Oral trehalose improves histological and behavior symptoms of mucopolysaccharidosis type II in iduronate 2-sulfatase deficient mice

Mucopolysaccharidosis type II (MPS II) is caused by a deficiency in iduronate-2-sulfatase (Ids), an enzyme that catabolizes glycosaminoglycan (GAG). Ids insufficiency results in the accumulation of GAG in various organs, ultimately resulting in multisystemic disease. Trehalose, a non-reducing disaccharide, has shown protective effects against various diseases. However, its potential utility through oral administration in MPS II has not yet been explored. In the present study, to investigate the efficacy of oral trehalose in Ids-knock-out (KO) mice, Ids-KO and wild type (WT) mice were treated with 2% trehalose dissolved in distilled water ad libitum for 24 weeks. Histological analysis revealed that almost all tissues from Ids-KO mice exhibited abnormal changes, including large vacuolization, inflammatory cell infiltration, and GAG deposition. However, oral administration of trehalose significantly suppressed GAG levels, vacuolization, inflammation and apoptosis in the spleen and brain. Additionally, oral trehalose considerably improved cognitive functions, such as short-term spatial learning and working memory, alongside limited improvements in walking capacity in Ids-KO mice. These results suggest that oral trehalose can reduce GAG accumulation, vacuolization and the number of apoptotic and inflammatory cells in pathological tissues including the brain, ultimately considerably improving spontaneous alteration behavior and could be a promising treatment option for MPS II.

A novel cryopreservation solution for adipose tissue based on metformin

BACKGROUND

Autologous fat grafting (AFG) often needs multiple sessions due to low volume retention. Young adipose tissue demonstrates a more pronounced therapeutic effect; thus, the cryopreservation of adipose tissue of young origin is particularly crucial. This study investigated the protective effect of a new cryopreservation solution combining trehalose, glycerol, and metformin on adipose tissue.

METHODS

This study initially examined the effect of various concentrations of metformin (0, 1, 2, 4, and 8 mM) on oxidative damage in adipose tissue to identify the optimal concentration. Subsequently, 1.5 mL of fresh human adipose tissue was subjected to freezing using trehalose + glycerol (TG group), trehalose + glycerol + metformin (TGM group), and the common cryoprotectant dimethyl sulfoxide (DMSO) + fetal bovine serum (FBS) (DF group). Samples were cryopreserved in liquid nitrogen for 2 weeks. After thawing, 1 mL of adipose tissue from each group was transplanted subcutaneously into the backs of nude mice. The cryoprotective effects on adipose tissue viability were evaluated during transplantation one month after transplantation.

RESULTS

The 2 mM concentration of metformin exhibited the lowest reactive oxygen species (ROS) level (29.20 ± 1.73) compared to other concentrations (P < 0.05). Cell proliferation and migration assays also supported the superior performance of the 2 mM concentration. Apoptotic analyses of stromal vascular fraction (SVF) cells showed the lowest levels in the 2 mM group. Compared to other cryopreservation groups, the adipose tissue in the TGM group closely resembled fresh adipose tissue in terms of gross structure and histological characteristics, with the lowest apoptosis rate of SVF cells. In vivo analysis revealed the highest tissue retention rate in the TGM group, with histological examination indicating robust structural integrity.

CONCLUSION

The TGM cryopreservation solution, containing metformin, greatly preserves adipose tissue, reduces apoptosis, and improves tissue retention rates. This solution was non-toxic and safe, making it well-suited for tissue cryopreservation in clinical settings.

The use of mesenchymal stromal cell secretome to enhance guided bone regeneration in comparison with leukocyte and platelet-rich fibrin

OBJECTIVES

Secretomes of mesenchymal stromal cells (MSC) represent a novel strategy for growth-factor delivery for tissue regeneration. The objective of this study was to compare the efficacy of adjunctive use of conditioned media of bone-marrow MSC (MSC-CM) with collagen barrier membranes vs. adjunctive use of conditioned media of leukocyte- and platelet-rich fibrin (PRF-CM), a current growth-factor therapy, for guided bone regeneration (GBR).

METHODS

MSC-CM and PRF-CM prepared from healthy human donors were subjected to proteomic analysis using mass spectrometry and multiplex immunoassay. Collagen membranes functionalized with MSC-CM or PRF-CM were applied on critical-size rat calvaria defects and new bone formation was assessed via three-dimensional (3D) micro-CT analysis of total defect volume (2 and 4 weeks) and 2D histomorphometric analysis of central defect regions (4 weeks).

RESULTS

While both MSC-CM and PRF-CM revealed several bone-related proteins, differentially expressed proteins, especially extracellular matrix components, were increased in MSC-CM. In rat calvaria defects, micro-CT revealed greater total bone coverage in the MSC-CM group after 2 and 4 weeks. Histologically, both groups showed a combination of regular new bone and 'hybrid' new bone, which was formed within the membrane compartment and characterized by incorporation of mineralized collagen fibers. Histomorphometry in central defect sections revealed greater hybrid bone area in the MSC-CM group, while the total new bone area was similar between groups.

CONCLUSION

Based on the in vitro and in vivo investigations herein, functionalization of membranes with MSC-CM represents a promising strategy to enhance GBR.

Osteoimmune-modulating and BMP-2-eluting anodised 3D printed titanium for accelerated bone regeneration

3D printing of titanium (Ti) metal has potential to transform the field of personalised orthopaedics and dental implants. However, the impacts of controlled surface topographical features of 3D printed Ti implants on their interactions with the cellular microenvironment and incorporation of biological growth factors, which are critical in guiding the integration of implants with bone, are not well studied. In the present study, we explore the role of surface topological features of 3D printed Ti implants using an anodised titania nanotube (TiNT) surface layer in guiding their immune cell interaction and ability to deliver bioactive form of growth factors. TiNT layers with precisely controlled pore diameter (between 21and 130 nm) were anodically grown on 3D printed Ti surfaces to impart a nano-micro rough topology. Immune biomarker profiles at gene and protein levels show that anodised 3D Ti surfaces with smaller pores resulted in classical activation of macrophages (M1-like), while larger pores (i.e., >100 nm) promoted alternate activation of macrophages (M2-like). The in vitro bone mineralisation studies using the conditioned media from the immunomodulatory studies elucidate a clear impact of pore diameter on bone mineralisation. The tubular structure of TiNTs was utilised as a container to incorporate recombinant human bone morphogenetic protein-2 (BMP-2) in the presence of various sugar and polymeric cryoprotectants. Sucrose offered the most sustainable release of preserved BMP-2 from TiNTs. Downstream effects of released BMP-2 on macrophages as well as bone mineralisation were assessed showing bioactivity retention of the released rhBMP-2. Overall, the TiNT surface topography in combination with controlled, sustained, and local release of bioactive growth factors can potentially enhance the osseointegration outcomes of custom 3D printed Ti implants in the clinic.

Functionalizing Collagen Membranes with MSC-Conditioned Media Promotes Guided Bone Regeneration in Rat Calvarial Defects

Functionalizing biomaterials with conditioned media (CM) from mesenchymal stromal cells (MSC) is a promising strategy for enhancing the outcomes of guided bone regeneration (GBR). This study aimed to evaluate the bone regenerative potential of collagen membranes (MEM) functionalized with CM from human bone marrow MSC (MEM-CM) in critical size rat calvarial defects. MEM-CM prepared via soaking (CM-SOAK) or soaking followed by lyophilization (CM-LYO) were applied to critical size rat calvarial defects. Control treatments included native MEM, MEM with rat MSC (CEL) and no treatment. New bone formation was analyzed via micro-CT (2 and 4 weeks) and histology (4 weeks). Greater radiographic new bone formation occurred at 2 weeks in the CM-LYO group vs. all other groups. After 4 weeks, only the CM-LYO group was superior to the untreated control group, whereas the CM-SOAK, CEL and native MEM groups were similar. Histologically, the regenerated tissues showed a combination of regular new bone and hybrid new bone, which formed within the membrane compartment and was characterized by the incorporation of mineralized MEM fibers. Areas of new bone formation and MEM mineralization were greatest in the CM-LYO group. Proteomic analysis of lyophilized CM revealed the enrichment of several proteins and biological processes related to bone formation. In summary, lyophilized MEM-CM enhanced new bone formation in rat calvarial defects, thus representing a novel 'off-the-shelf' strategy for GBR.

Enhanced Biocompatibility and Osteogenic Activity of Marine-Plankton-Derived Whitlockite Bone Granules through Bone Morphogenetic Protein 2 Incorporation

Whitlockite (WH) is a calcium-phosphate-based Mg-containing ceramic with good mechanical properties, rapid resorption, and good osteogenicity. Recently, we successfully synthesized highly porous WH granules using a marine plankton exoskeleton (MP-WH). In the present study, we improved the osteoinductive activity of MP-WH granules by bone morphogenetic protein2 (BMP2) (MP-WH/BMP2). The surface morphology and composition of the fabricated MP-WH/BMP2 granules were characterized using scanning electron microscopy (SEM), X-ray diffraction, and Fourier transform infrared (FT-IR) spectroscopy. The biocompatibility and osteogenic effects were evaluated using human mesenchymal stem cells (hMSCs). BMP2 was absorbed on the surfaces of the MP-WH/BMP2 granules. Immobilized BMP2 was released at a moderate rate over 30 days. hMSCs seeded on MP-WH/BMP2 granules became biocompatible, with a better proliferation and adhesion for MP-WH/BMP2, compared with MP-WH. Bone-specific markers Runx2, type I collagen, osteocalcin, and osteopontin were significantly upregulated following BMP2 incorporation. Similar observations were made regarding the alkaline phosphatase activity. This study suggests that BMP2 incorporation improves the osteoinductive activity of marine-plankton-derived WH granules for bone tissue repair.

Active bone material containing modified recombinant human bone morphogenetic protein 2 induces bone regeneration in the alveolar process cleft in rabbits

The clinical application of most materials used to fill severe bone defects is limited owing to the insufficient ability of such materials to induce bone regeneration over a long repair period. The purpose of this study was to establish a model for the alveolar process cleft in rabbits to evaluate the effect of active bone material in bone defect repair. The active bone material used in this study is a new bone repair material composed of a heterogeneous collagen membrane implanted with modified recombinant human bone morphogenetic protein 2. This proposed active bone material can specifically bind to collagen. Twenty-four young Japanese white rabbits (JWRs) were selected and randomly divided into four groups (normal, control, material, and bone morphogenetic protein groups). The alveolar process cleft model was established by removing an equal volume bone at the left maxillary position. Blood samples were collected from the JWRs 3 and 6 months after the surgery to evaluate the biocompatibility of the active bone materials. Subsequently, the skull model was established, and the appearance was observed. Imaging methods (including X-ray examination and micro-computerized tomography scanning), tissue staining, and immunohistochemistry were employed for the evaluation. The bone collagen material and active bone material exhibited high biocompatibility. In addition, the ability of the active bone material to induce bone repair and regeneration was higher than that of the bone collagen material. The active bone material exhibited satisfactory bone regeneration performance in rabbits, indicating its potential as an active material for repairing congenital alveolar process clefts in humans.

The combination of trehalose and glycerol: an effective and non-toxic recipe for cryopreservation of human adipose-derived stem cells

Background

Adipose-derived stem cells (ADSCs) promote tissue regeneration and repair. Cryoprotective agents (CPAs) protect cells from cryodamage during cryopreservation. Safe and efficient cryopreservation of ADSCs is critical for cell-based therapy in clinical applications. However, most CPAs are used at toxic concentrations, limiting their clinical application.

Objective

The aim of this study is to develop a non-toxic xeno-free novel CPA aiming at achieving high-efficiency and low-risk ADSC cryopreservation.

Methods

We explored different concentrations of trehalose (0.3 M, 0.6 M, 1.0 M, and 1.25 M) and glycerol (10%, 20%, and 30% v/v) for optimization and evaluated and compared the outcomes of ADSCs cryopreservation between a combination of trehalose and glycerol and the commonly used CPA DMSO (10%) + FBS (90%). All samples were slowly frozen and stored in liquid nitrogen for 30 days. The effectiveness was evaluated by the viability, proliferation, migration, and multi-potential differentiation of the ADSCs after thawing.

Results

Compared with the groups treated with individual reagents, the 1.0 M trehalose (Tre) + 20% glycerol (Gly) group showed significantly higher efficiency in preserving ADSC activities after thawing, with better outcomes in both cell viability and proliferation capacity. Compared with the 10% DMSO + 90% FBS treatment, the ADSCs preserved in 1.0 M Tre + 20% Gly showed similar cell viability, surface markers, and multi-potential differentiation but a significantly higher migration capability. The results indicated that cell function preservation can be improved by 1.0 M Tre + 20% Gly.

Conclusions

The 1.0 M Tre + 20% Gly treatment preserved ADSCs with a higher migration capability than 10% DMSO + 90% FBS and with viability higher than that with trehalose or glycerol alone but similar to that with 10% DMSO + 90% FBS and fresh cells. Moreover, the new CPA achieves stemness and multi-potential differentiation similar to those in fresh cells. Our results demonstrate that 1.0 M Tre + 20% Gly can more efficiently cryopreserve ADSCs and is a non-toxic CPA that may be suitable for clinical applications.

Lyophilized Autologous Serum Eyedrops: Experimental and Comparative Study

PURPOSE

To analyze the biological stability of autologous serum eyedrops after lyophilization.

DESIGN

Prospective, comparative experimental study.

METHODS

This was a comparative study with serum obtained from 12 healthy volunteers. The concentrations of different epitheliotropic factors (eg, transforming growth factor-β [TGF-β1], epidermal growth factor [EGF], platelet-derived growth factor AB [PDGF-AB], and albumin) were measured in fresh and lyophilized serum. The samples were studied after serum preparation (fresh serum) and immediately after saline solution reconstitution of lyophilized serum (0), 15, and 30 days later. The biological effects of both serum samples were also compared on conjunctival and corneal cell cultures. The pH, osmolarity, and serum density were also determined.

RESULTS

No significant differences were found in the concentration of growth factors between fresh serum and re-dissolved serum samples after lyophilization. The concentration of growth factors remained stable during 1 month at 4°C in re-dissolved lyophilized form with saline solution. No differences were found related to osmolarity, pH, and density between fresh and lyophilized serum. In addition, no differences were found on the conjunctival and corneal cells proliferation and differentiation in cells cultures between either serum preparation.

CONCLUSIONS

The properties of autologous serum remain after lyophilization. The lyophilized serum can be easily stored without temperature restrictions and easily reconstituted for preparation of eyedrops for standard clinical use.

Porous PolyHIPE microspheres for protein delivery from an injectable bone graft

Delivery of osteoinductive factors such as bone morphogenetic protein 2 (BMP-2) has emerged as a prominent strategy to improve regeneration in bone grafting procedures. However, it remains challenging to identify a carrier that provides the requisite loading efficiency and release kinetics without compromising the mechanical properties of the bone graft. Previously, we reported on porous, polymerized high internal phase emulsion (polyHIPE) microspheres fabricated using controlled fluidics. Uniquely, this solvent-free method provides advantages over current microsphere fabrication strategies including in-line loading of growth factors to improve loading efficiency. In the current study, we utilized this platform to fabricate protein-loaded microspheres and investigated the effect of particle size (∼400 vs ∼800 μm) and pore size (∼15 vs 30 μm) on release profiles. Although there was no significant effect of these variables on the substantial burst release profile of the microspheres, the incorporation of the protein-loaded microspheres within the injectable polyHIPE resulted in a sustained release of protein from the bulk scaffold over a two-week period with minimal burst release. Bioactivity retention of encapsulated BMP-2 was confirmed first using a genetically-modified osteoblast reporter cell line. A functional assay with human mesenchymal stem cells established that the BMP-2 release from microspheres induced osteogenic differentiation. Finally, microsphere incorporation had minimal effect on the cure and compressive properties of an injectable polyHIPE bone graft. Overall, this work demonstrates that these microsphere-polyHIPE composites have strong potential to enhance bone regeneration through controlled release of BMP-2 and other growth factors. STATEMENT OF SIGNIFICANCE: This manuscript describes a method for solvent-free fabrication of porous microspheres from high internal phase emulsions using a controlled fluids setup. The principles of emulsion templating and fluid dynamics provide exceptional control of particle size and pore architecture. In addition to the advantage of solvent-free fabrication, this method provides in-line loading of protein directly into the pores of the microspheres with high loading efficiencies. The incorporation of the protein-loaded microspheres within an injectable polyHIPE scaffold resulted in a sustained release of protein over a two-week period with minimal burst release. Retention of BMP-2 bioactivity and incorporation of microspheres with minimal effect on scaffold compressive properties highlights the potential of these new bone grafts.

Stabilization of enzyme-immobilized hydrogels for extended hypoxic cell culture

In this work, glucose oxidase (GOx)-immobilized hydrogels are developed and optimized as an easy and convenient means for creating solution hypoxia in a regular incubator. Specifically, acrylated GOx co-polymerizes with poly(ethylene glycol) diacrylate (PEGDA) to form PEGDA-GOx hydrogels. Results show that freeze-drying and reaction by-products, hydrogen peroxide, negatively affect oxygen-consuming activity of network-immobilized GOx. However, the negative effects of freeze-drying can be mitigated by addition of trehalose/raffinose in the hydrogel precursor solution, whereas the inhibition of GOx caused by hydrogen peroxide can be prevented via addition of glutathione (GSH) in the buffer/media. The ability to preserve enzyme activity following freeze-drying and during long-term incubation permits facile application of this material to induce long-term solution/media hypoxia in cell culture plasticware placed in a regular CO₂ incubator.

Bone repair scaffold coated with bone morphogenetic protein-2 for bone regeneration in murine calvarial defect model: Systematic review and quality evaluation

To systematically assess the effects of hydroxyapatite bone repair scaffold coated with bone morphogenetic protein-2 on murine calvarial defect models and to determine the quality of studies according to the Animal Research Reporting in In Vivo Experiments guidelines. Internet search was performed in duplicate using PubMed, MEDLINE, Ovid and Embase databases (without restrictions on publication date). The Animal Research Reporting in In Vivo Experiments guidelines were used to evaluate the quality of selected studies. Following screening, 12 studies were eligible for the review. Studies with average quality coefficients predominated (66.67%), followed by poor (25%) and excellent (8.33%) quality coefficients. Minimum quality scores were assigned to the Animal Research Reporting in In Vivo Experiments guideline items: housing and husbandry (9), allocation (11), outcomes (12), interpretation (18) and generalizability (19). Sprague–Dawley rats were the most frequently used (50%) species, and most studies had a sample size of more than 30 (58.33%). A defect dimension of 5 mm was the most common (33.33%). The biological hydroxyapatite composite scaffold was common (50%), and the bioactive factors were bone morphogenetic protein-2 (50%) and recombinant human bone morphogenetic protein-2 (50%). Histomorphometric results showed that bone morphogenetic protein-2 enhanced the capacity to regenerate bone considerably. In addition, scaffolds with bone morphogenetic protein-2 resulted in a significant increase in the blood vessel in the new bone. The findings suggested that data on animal experiments of hydroxyapatite scaffold coated with bone morphogenetic protein-2 in murine calvarial defect models lack homogeneity. Animal experiment should follow the Animal Research Reporting in In Vivo Experiments guidelines to promote the high quality, integrity and reproducibility. This systematic review suggested that bone morphogenetic protein-2 enhanced the capacity to regenerate bone and the angiogenesis in the new bone.

Dose reduction of bone morphogenetic protein-2 for bone regeneration using a delivery system based on lyophilization with trehalose

Introduction

To induce sufficient new bone formation, high doses of bone morphogenetic protein-2 (BMP-2) are applied in regenerative medicine that often induce serious side effects. Therefore, improved treatment strategies are required. Here, we investigate whether the delivery of BMP-2 lyophilized in the presence of trehalose reduced the dose of BMP-2 required for bone regeneration.

Materials and methods

A new growth factor delivery system was fabricated using BMP-2-loaded TiO₂ nanotubes by lyophilization with trehalose (TiO₂-Lyo-Tre-BMP-2). We measured BMP-2 release characteristics, bioactivity, and stability, and determined the effects on the osteogenic differentiation of bone marrow stromal cells in vitro. Additionally, we evaluated the ability of this formulation to regenerate new bone around implants in rat femur defects by micro-computed tomography (micro-CT), sequential fluorescent labelling, and histological analysis.

Results

Compared with absorbed BMP-2-loaded TiO₂ nanotubes (TiO₂-BMP-2), TiO₂-Lyo-Tre-BMP-2 exhibited sustained release, consistent bioactivity, and higher stability of BMP-2, and resulted in greater osteogenic differentiation of BMSCs. Eight weeks post-operation, TiO₂-Lyo-Tre-BMP-2 nanotubes, with various dosages of BMP-2, regenerated larger amounts of new bone than TiO₂-BMP-2 nanotubes.

Conclusion

Our findings indicate that delivery of BMP-2 lyophilized with trehalose may be a promising method to reduce the dose of BMP-2 and avoid the associated side effects.

Potency Biomarker Signature Genes from Multiparametric Osteogenesis Assays: Will cGMP Human Bone Marrow Mesenchymal Stromal Cells Make Bone?

In skeletal regeneration approaches using human bone marrow derived mesenchymal stromal cells (hBM-MSC), functional evaluation before implantation has traditionally used biomarkers identified using fetal bovine serum-based osteogenic induction media and time courses of at least two weeks. However, emerging pre-clinical evidence indicates donor-dependent discrepancies between these ex vivo measurements and the ability to form bone, calling for improved tests. Therefore, we adopted a multiparametric approach aiming to generate an osteogenic potency assay with improved correlation. hBM-MSC populations from six donors, each expanded under clinical-grade (cGMP) conditions, showed heterogeneity for ex vivo growth response, mineralization and bone-forming ability in a murine xenograft assay. A subset of literature-based biomarker genes was reproducibly upregulated to a significant extent across all populations as cells responded to two different osteogenic induction media. These 12 biomarkers were also measurable in a one-week assay, befitting clinical cell expansion time frames and cGMP growth conditions. They were selected for further challenge using a combinatorial approach aimed at determining ex vivo and in vivo consistency. We identified five globally relevant osteogenic signature genes, notably TGF-ß1 pathway interactors; ALPL, COL1A2, DCN, ELN and RUNX2. Used in agglomerative cluster analysis, they correctly grouped the bone-forming cell populations as distinct. Although donor #6 cells were correlation slope outliers, they contrastingly formed bone without showing ex vivo mineralization. Mathematical expression level normalization of the most discrepantly upregulated signature gene COL1A2, sufficed to cluster donor #6 with the bone-forming classification. Moreover, attenuating factors causing genuine COL1A2 gene down-regulation, restored ex vivo mineralization. This suggested that the signature gene had an osteogenically influential role; nonetheless no single biomarker was fully deterministic whereas all five signature genes together led to accurate cluster analysis. We show proof of principle for an osteogenic potency assay providing early characterization of primary cGMP-hBM-MSC cultures according to their donor-specific bone-forming potential.

Controlled release of NELL-1 protein from chitosan/hydroxyapatite-modified TCP particles

NEL-like molecule-1 (NELL-1) is a novel osteogenic protein that showing high specificity to osteochondral cells. It was widely used in bone regeneration research by loading onto carriers such as tricalcium phosphate (TCP) particles. However, there has been little research on protein controlled release from this material and its potential application. In this study, TCP was first modified with a hydroxyapatite coating followed by a chitosan coating to prepare chitosan/hydroxyapatite-coated TCP particles (Chi/HA-TCP). The preparation was characterized by SEM, EDX, FTIR, XRD, FM and Zeta potential measurements. The NELL-1 loaded Chi/HA-TCP particles and the release kinetics were investigated in vitro. It was observed that the Chi/HA-TCP particles prepared with the 0.3% (wt/wt) chitosan solution were able to successfully control the release of NELL-1 and maintain a slow, steady release for up to 28 days. Furthermore, more than 78% of the loaded protein's bioactivity was preserved in Chi/HA-TCP particles over the period of the investigation, which was significantly higher than that of the protein released from hydroxyapatite coated TCP (HA-TCP) particles. Collectively, this study suggests that the osteogenic protein NELL-1 showed a sustained release pattern after being encapsulated into the modified Chi/HA-TCP particles, and the NELL-1 integrated composite of Chi/HA-TCP showed a potential to function as a protein delivery carrier and as an improved bone matrix for use in bone regeneration research.

Overcoming physical constraints in bone engineering: ‘the importance of being vascularized’

Bone plays several physiological functions and is the second most commonly transplanted tissue after blood. Since the treatment of large bone defects is still unsatisfactory, researchers have endeavoured to obtain scaffolds able to release growth and differentiation factors for mesenchymal stem cells, osteoblasts and endothelial cells in order to obtain faster mineralization and prompt a reliable vascularization. Nowadays, the application of osteoblastic cultures spans from cell physiology and pharmacology to cytocompatibility measurement and osteogenic potential evaluation of novel biomaterials. To overcome the simple traditional monocultures in vitro, co-cultures of osteogenic and vasculogenic precursors were introduced with very interesting results. Increasingly complex culture systems have been developed, where cells are seeded on proper scaffolds and stimulated so as to mimic the physiological conditions more accurately. These bioreactors aim at enabling bone regeneration by incorporating different cells types into bio-inspired materials within a surveilled habitat. This review is focused on the most recent developments in the organomimetic cultures of osteoblasts and vascular endothelial cells for bone tissue engineering.

Rapid bone regeneration by Escherichia coli-derived recombinant human bone morphogenetic protein-2 loaded on a hydroxyapatite carrier in the rabbit calvarial defect model

Background

The aim of this study was to determine the osteoconductivity of hydroxyapatite particles (HAP) as a carrier for Escherichia coli-derived recombinant human bone morphogenetic protein-2 (ErhBMP-2). Two 8-mm diameter bicortical calvarial defects were created in each of 20 rabbits. One of each pair of defects was randomly assigned to be filled with HAP only (HAP group) or ErhBMP-2 loaded HAP (ErhBMP-2/HAP group), while the other defect was left untreated (control group). The animals were killed after either 2 weeks (n = 10) or 8 weeks (n = 10) of healing, and histological, histomorphometric, and tomographic analyses were performed.

Results

All experimental sites showed uneventful healing during the postoperative healing period. In both histomorphometric and tomographic analyses, the new bone area or volume of the ErhBMP-2/HAP group was significantly greater than that of the HAP and control groups at 2 weeks (p < 0.05). However, at 8 weeks, no significant difference in new bone area or volume was observed between the ErhBMP-2/HAP and HAP groups. The total augmented area or volume was not significantly different between the ErhBMP-2/HAP and HAP groups at 2 and 8 weeks.

Conclusions

Combining ErhBMP-2 with HAP could significantly promote rapid initial new bone formation. Moreover, HAP graft could increase new bone formation and space maintenance, therefore it might be one of the effective carriers of ErhBMP-2.

Successful cryopreservation of whole sheep ovary by using DMSO-free cryoprotectant

PURPOSE

The study aims to assess the protective effects of dimethyl sulfoxide (DMSO)-free solution based on trehalose on the cryopreservation of a whole sheep ovary and evaluate its use as an efficient cryoprotectant.

METHOD

Twenty-one ovaries collected from 6- to 8-month-old non-pregnant female sheep were randomly distributed into three groups, namely, a fresh group, a DMSO-free group, and a DMSO group. The morphology, cell apoptosis (by hematoxylin and eosin (HE) staining and terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL) assay), and mRNA transcript of Bcl-2-associated X protein (BAX) and cold inducible RNA-binding protein (CIRP) (by real-time PCR) of the thawed sheep ovaries and fresh controls were tested to establish a criterion for appraising the results of the cryopreservation.

RESULTS

(i) The histological assessment indicated that the structure of the DMSO-free ovaries remained largely intact and comparable to those of the fresh control groups; whereas, significant damage was observed in the ovaries of the DMSO group (P < 0.05). (ii) The TUNEL assay and mRNA transcript of the BAX assessment showed that the apoptosis parameter in the fresh group was the lowest among all the groups (P < 0.05), and the parameter in the DMSO-free group was significantly lower than that in the DMSO group (P < 0.05). (iii) The level of the CIRP transcripts increased the most in the DMSO-free group followed by the DMSO group and the fresh control group (P < 0.05).

CONCLUSIONS

These results indicate that a DMSO-free cryoprotectant solution, especially a trehalose cryoprotectant, is an efficient cryoprotectant and has a beneficial effect on the cryopreservation of whole sheep ovaries.

Trehalose maintains vitality of mouse epididymal epithelial cells and mediates gene transfer

In the present study, trehalose was utilized to improve primary culture of mouse epididymal epithelial cells in vitro, and to enhance naked DNA delivery in epididymis in vivo. During the six-day culture, the proliferation activity of the cells in the medium with addition of trehalose was higher than that of those cells cultured in absence of trehalose (p<0.01). To determine the optimal concentration for cell proliferation, a series of trehalose concentrations (0, 60, 120, 180 mM) were tested, and the result indicated that the cell in the medium with 120 mM trehalose showed the highest proliferation potential. The epididymis epithelial cells were cultured in the medium containing 120 mM trehalose upon 16^th passage, and they continued expressing markers of epididymal epithelial cell, such as rE-RABP, AR and ER-beta. Our study also indicated that trehalose concentrations of 120–240 mM, especially 180 mM, could effectively enhance DNA delivery into the mouse epididymis epithelial cell in vitro. Moreover, trehalose could induce in vivo expression of exogenous DNA in epididymal epithelial cells and help to internalize plasmid into sperm,which did not influence motility of sperm when the mixture of trehalose (180 mM) and DNA was injected into epididymal lumen through efferent tubule. This study suggested that trehalose, as an effective and safer reagent, could be employed potentially to maintain vitality of mouse epididymal epthetial cells during long-term culture in vitro and to mediate in vitro and in vivo gene transfer.

The importance of implementing proper selection of excipients in lupus clinical trials

Peptide therapeutics hold attractive potential. However, the proper stabilization of such therapeutics remains a major challenge. Some peptides are marginally stable and are prone to degradation. Therefore, in addition to chemical modifications that can be introduced in their sequence, a wide variety of excipients are added in the formulation to stabilize them, as is also done routinely for protein therapeutics. These substances are supposed to suppress peptide/protein aggregation and surface adsorption, facilitate their dispersion and additionally to provide physiological osmolality. Particular attention has to be paid to the choice of such excipients. Here we highlight the observation that in certain clinical situations, an excipient that is not totally inert can play a highly damaging role and mask (or even reverse) the beneficial effect of a molecule in clinical evaluation. This is the case, for instance, of trehalose, a normally safe excipient, which notably has proven to act as an activator of autophagy. This excipient, although used efficiently in several therapeutics, adversely impacted a phase IIb clinical trial for human and murine lupus, a systemic autoimmune disease in which it has been recently discovered that at the base line, autophagy is already abnormally enhanced in lymphocytes. Thus, in this particular pathology, while the peptide that was tested was active in lupus patients when formulated in mannitol, it was not efficient when formulated in trehalose. This observation is important, since autophagy is enhanced in a variety of pathological situations, such as obesity, diabetes, certain neurological diseases, and cancer.