Osteoinduction within BMP-2 transduced muscle tissue fragments with and without a fascia layer: implications for bone tissue engineering

Biological Evaluation of the Osteoinductive Potential of Dry Teeth after Chemical Demineralization Treatment Using the Tooth Transformer Device

Several studies have already demonstrated the biocompatibility of a tooth as a grafting material in the regeneration of bone tissue, showing its osteoconductive potential, while no studies have verified whether the osteoinductive potential of a tooth remains constant or is altered after its treatment with the Tooth Transformer (TT) device. The aim of the study was to demonstrate that the treatment with the TT device did not alter the osteoinductivity of an extracted tooth that was stored dry. Twelve extracted human teeth were collected from real patients. Caries, tartar and filling materials were removed from each tooth; each tooth was coarsely cut and stored at room temperature (RT) until use. Each sample was shredded, demineralized and disinfected, using the TT device. Protein extraction was carried out for each sample, and Western Blot analysis was performed to test the presence of mineralization protein LIM-1 and transforming growth factor-β. The presence of the human Bone Morphogenetic Protein 2 (BMP-2) and human collagen Type I (COL-I) was found in dry tooth samples processed with the TT device and subjected to Enzyme-Linked Immunosorbent Assay (ELISA) testing. The treatment of chemical demineralization using the TT device does not alter the osteoinductive potential of a dry tooth.

Osteochondrogenesis by TGF-β3, BMP-2 and noggin growth factor combinations in an ex vivo muscle tissue model: Temporal function changes affecting tissue morphogenesis

In the absence of clear molecular insight, the biological mechanism behind the use of growth factors applied in osteochondral regeneration is still unresolved. The present study aimed to resolve whether multiple growth factors applied to muscle tissue in vitro, such as TGF-β3, BMP-2 and Noggin, can lead to appropriate tissue morphogenesis with a specific osteochondrogenic nature, thereby revealing the underlying molecular interaction mechanisms during the differentiation process. Interestingly, although the results showed the typical modulatory effect of BMP-2 and TGF-β3 on the osteochondral process, and Noggin seemingly downregulated specific signals such as BMP-2 activity, we also discovered a synergistic effect between TGF-β3 and Noggin that positively influenced tissue morphogenesis. Noggin was observed to upregulate BMP-2 and OCN at specific time windows of culture in the presence of TGF-β3, suggesting a temporal time switch causing functional changes in the signaling protein. This implies that signals change their functions throughout the process of new tissue formation, which may depend on the presence or absence of specific singular or multiple signaling cues. If this is the case, the signaling cascade is far more intricate and complex than originally believed, warranting intensive future investigations so that regenerative therapies of a critical clinical nature can function properly.

Osteogenic Differentiation of Human Adipose-Derived Stem Cells Seeded on a Biomimetic Spongiosa-like Scaffold: Bone Morphogenetic Protein-2 Delivery by Overexpressing Fascia

Human adipose-derived stem cells (hADSCs) have the capacity for osteogenic differentiation and, in combination with suitable biomaterials and growth factors, the regeneration of bone defects. In order to differentiate hADSCs into the osteogenic lineage, bone morphogenetic proteins (BMPs) have been proven to be highly effective, especially when expressed locally by route of gene transfer, providing a constant stimulus over an extended period of time. However, the creation of genetically modified hADSCs is laborious and time-consuming, which hinders clinical translation of the approach. Instead, expedited single-surgery gene therapy strategies must be developed. Therefore, in an in vitro experiment, we evaluated a novel growth factor delivery system, comprising adenoviral BMP-2 transduced fascia tissue in terms of BMP-2 release kinetics and osteogenic effects, on hADSCs seeded on an innovative biomimetic spongiosa-like scaffold. As compared to direct BMP-2 transduction of hADSCs or addition of recombinant BMP-2, overexpressing fascia provided a more uniform, constant level of BMP-2 over 30 days. Despite considerably higher BMP-2 peak levels in the comparison groups, delivery by overexpressing fascia led to a strong osteogenic response of hADSCs. The use of BMP-2 transduced fascia in combination with hADSCs may evolve into an expedited single-surgery gene transfer approach to bone repair.

Optimizations for identifying reference genes in bone and cartilage bioengineering

BACKGROUND

Reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) remains one of the best-established techniques to assess gene expression patterns. However, appropriate reference gene(s) selection remains a critical and challenging subject in which inappropriate reference gene selction can distort results leading to false interpretations. To date, mixed opinions still exist in how to choose the most optimal reference gene sets in accodrance to the Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guideline. Therefore, the purpose of this study was to investigate which schemes were the most feasible for the identification of reference genes in a bone and cartilage bioengineering experimental setting. In this study, rat bone mesenchymal stem cells (rBMSCs), skeletal muscle tissue and adipose tissue were utilized, undergoing either chondrogenic or osteogenic induction, to investigate the optimal reference gene set identification scheme that would subsequently ensure stable and accurate interpretation of gene expression in bone and cartilage bioengineering.

RESULTS

The stability and pairwise variance of eight candidate reference genes were analyzed using geNorm. The V_0.15- vs. V_min-based normalization scheme in rBMSCs had no significant effect on the eventual normalization of target genes. In terms of the muscle tissue, the results of the correlation of NF values between the V_0.15 and V_min schemes and the variance of target genes expression levels generated by these two schemes showed that different schemes do indeed have a significant effect on the eventual normalization of target genes. Three selection schemes were adopted in terms of the adipose tissue, including the three optimal reference genes (Opt₃), V_0.20 and V_min schemes, and the analysis of NF values with eventual normalization of target genes showed that the different selection schemes also have a significant effect on the eventual normalization of target genes.

CONCLUSIONS

Based on these results, the proposed cut-off value of Vn/n + 1 under 0.15, according to the geNorm algorithm, should be considered with caution. For cell only experiments, at least rBMSCs, a Vn/n + 1 under 0.15 is sufficient in RT-qPCR studies. However, when using certain tissue types such as skeletal muscle and adipose tissue the minimum Vn/n + 1 should be used instead as this provides a far superior mode of generating accurate gene expression results. We thus recommended that when the stability and variation of a candidate reference genes in a specific study is unclear the minimum Vn/n + 1 should always be used as this ensures the best and most accurate gene expression value is achieved during RT-qPCR assays.

Trauma induced tissue survival in vitro with a muscle-biomaterial based osteogenic organoid system: a proof of concept study

BACKGROUND

The translation from animal research into the clinical environment remains problematic, as animal systems do not adequately replicate the human in vivo environment. Bioreactors have emerged as a good alternative that can reproduce part of the human in vivo processes at an in vitro level. However, in vitro bone formation platforms primarily utilize stem cells only, with tissue based in vitro systems remaining poorly investigated. As such, the present pilot study explored the tissue behavior and cell survival capability within a new in vitro skeletal muscle tissue-based biomaterial organoid bioreactor system to maximize future bone tissue engineering prospects.

RESULTS

Three dimensional printed β-tricalcium phosphate/hydroxyapatite devices were either wrapped in a sheet of rat muscle tissue or first implanted in a heterotopic muscle pouch that was then excised and cultured in vitro for up to 30 days. Devices wrapped in muscle tissue showed cell death by day 15. Contrarily, devices in muscle pouches showed angiogenic and limited osteogenic gene expression tendencies with consistent TGF-ß₁, COL4A1, VEGF-A, RUNX-2, and BMP-2 up-regulation, respectively. Histologically, muscle tissue degradation and fibrin release was seen being absorbed by devices acting possibly as a support for new tissue formation in the bioceramic scaffold that supports progenitor stem cell osteogenic differentiation.

CONCLUSIONS

These results therefore demonstrate that the skeletal muscle pouch-based biomaterial culturing system can support tissue survival over a prolonged culture period and represents a novel organoid tissue model that with further adjustments could generate bone tissue for direct clinical transplantations.

A promising material for bone repair: PMMA bone cement modified by dopamine-coated strontium-doped calcium polyphosphate particles

Polymethyl methacrylate (PMMA) bone cement has been widely used in clinics as bone repair materials for its excellent mechanical properties and good injection properties. However, it also has defects such as poor biological performance, high temperature, and the monomer has certain toxicity. Our study tried to modify the PMMA bone cement by doping with various particle weight fractions (5, 10 and 15%) of SCPP particles and polydopamine-coated SCPP particles (D/SCPP) to overcome its clinical application disadvantages. Our study showed that all results of physical properties of samples are in accordance with ISO 5833. The 15% D/SCPP/PMMA composite bone cement had much better biocompatibility compared with pure PMMA bone cement and SCPP/PMMA composite bone cement due to the best cell growth-promoting mineralization deposition on the surface of 15% D/SCPP/PMMA composite bone cements and Sr²⁺ released from SCPP particles. Our research also revealed that the reaction temperature was found to be reduced with an increase in doped particles after incorporating the particles into composite bone cements. The novel PMMA bone cements modified by D/SCPP particles are promising materials for bone repair.