A new semi-orthotopic bone defect model for cell and biomaterial testing in regenerative medicine

Synergistic influences of BMP9 and NGF on the osteogenic differentiation of C3H10T1/2 mesenchymal stem cells

BACKGROUND

Bone morphogenetic protein 9 (BMP9) and nerve growth factor (NGF) are critical factors influencing osteogenic differentiation in mesenchymal stem cells (MSCs). While BMP9 has been recognized for its potent osteogenic capabilities, NGF's role in bone tissue engineering is less understood. This investigation delineated the synergistic link of BMP9 with NGF in driving osteogenic differentiation in C3H10T1/2 MSCs.

OBJECTIVE

To evaluate the combined impact of BMP9 and NGF on osteogenic markers' expression levels and the formation of calcified nodules in C3H10T1/2 cells, providing a basis for the enhanced bone regeneration strategies in tissue engineering.

METHODS

C3H10T1/2 cells were subjected to treatment regimens incorporating NGF at variable concentrations (10, 50, and 100 ng/ml) and BMP9, either as monotherapies or in combination. Osteogenic differentiation' comprehensive assessment was undertaken by quantifying early-stage markers (Runx2, Col I) and late-stage markers (OPN) via RT-PCR, Western blotting, ALP staining, and Alizarin Red S staining for mineralized matrix deposition.

RESULTS

NGF elicited a concentration-dependent augmentation of early osteogenic markers, with the 10 ng/ml dosage demonstrating maximal efficacy. BMP9 independently facilitated robust osteogenic differentiation, whereas the combinatorial treatment with BMP9 and NGF synergistically amplified the expression levels of Runx2, Col I, and OPN. Notably, this combined treatment yielded a remarkable enhancement in the deposition of mineralized extracellular matrix, as evidenced by a notable escalation in the size and density of calcified nodules relative to monotherapies.

CONCLUSION

The findings unveiled the remarkable synergistic link of BMP9 with NGF in potentiating osteogenic differentiation in C3H10T1/2 MSCs. This dual-factor approach presents a compelling paradigm for advancing bone regeneration strategies, providing substantial promise for utilization in bone tissue engineering plus regenerative medicine.

A miR-activated hydrogel for the delivery of a pro-chondrogenic microRNA-221 inhibitor as a minimally invasive therapeutic approach for articular cartilage repair

Articular cartilage has limited capacity for repair (or for regeneration) under pathological conditions, given its non-vascularized connective tissue structure and low cellular density. Our group has successfully developed an injectable hydrogel for cartilage repair, composed of collagen type I (Col I), collagen type II (Col II), and methacrylated-hyaluronic acid (MeHA), capable of supporting chondrogenic differentiation of mesenchymal stem cells (MSCs) towards articular cartilage-like phenotypes. Recent studies have demonstrated that silencing miR-221 may be an effective approach in promoting improved MSC chondrogenesis. Thus, this study aimed to develop a miR-activated hydrogel capable of offering a more effective and less invasive therapeutic approach to articular cartilage repair by delivering a pro-chondrogenic miR-221 inhibitor to MSCs using our MeHA-Col I/Col II hydrogel. The MeHA-Col I/Col II hydrogel was cast as previously shown and incorporated with cells transfected with miR-221 inhibitor (using a non-viral peptide delivery vector) to produce the miR-activated hydrogel. Down-regulation of miR-221 did not affect cell viability and enhanced MSCs-mediated chondrogenesis, as evidenced by significantly upregulated expression of key pro-chondrogenic articular cartilage genes (COL2A1 and ACAN) without promoting hypertrophic events (RUNX2 and COL10A1). Furthermore, miR-221 down-regulation improved cartilage-like matrix formation in the MeHA-Col I/Col II hydrogel, with significantly higher levels of sulfated glycosaminoglycans (sGAG) and Col II produced by MSCs in the hydrogel. These results provide evidence of the potential of the miR-activated hydrogel as a minimally invasive therapeutic strategy for articular cartilage repair.

Cisplatin-functionalized dual-functional bone substitute granules for bone defect treatment after bone tumor resection

Invasive bone tumors pose a significant healthcare challenge, often requiring systemic chemotherapy and limb salvage surgery. However, these strategies are hampered by severe side effects, complex post-resection bone defects, and high local recurrence rates. To address this, we developed dual-functional bone substitute biomaterials by functionalizing commercially available bone substitute granules (Bio-Oss® and MBCP®+) with the established anticancer agent cisplatin. Physicochemical characterization revealed that Bio-Oss® granules possess a higher surface area and lower crystallinity compared to MBCP®+ granules, which enhances their capacity for cisplatin adsorption and release. In co-cultures with metastatic breast and prostate cancer cells (MDA-MB-231 and PC3) and bone marrow stromal cells (hBMSCs), cisplatin-functionalized granules and their releasates exhibited dose-dependent cytotoxic effects on cancer cells while having less impact on hBMSCs. Furthermore, investigations on the mechanism of action indicated that cisplatin induced significant cell cycle arrest and apoptosis in MDA-MB-231 and PC3 cells, contrasting with minimal effects on hBMSCs. In a rat femoral condyle defect model, cisplatin-functionalized granules did not evoke adverse effects on bone tissue ingrowth or new bone formation. Importantly, local application of cisplatin-functionalized granules resulted in negligible cisplatin accumulation without signs of apoptotic damage in kidneys and livers. Taken together, we here provide hard evidence that cisplatin-functionalized granules maintain a favorable balance between biosafety, anticancer efficacy, and bone regenerative capacity. Consequently, loading granular bone substitutes with cisplatin holds promise for local treatment of bone defects following bone tumor resections, presenting a safe and potentially more effective alternative to systemic cisplatin administration. STATEMENT OF SIGNIFICANCE: Current treatments in combating malignant bone tumors are hampered by severe side effects, high local tumor recurrence, and complex bone defects after surgery. This study explores a facile manufacturing method to render two types of commercially available bone substitute granules (Bio-Oss® and MBCP®+) suitable for local delivery of cisplatin. The use of cisplatin-functionalized granules has shown promising results both in killing cancer cells in a dose-dependent manner and in aiding bone regeneration. Importantly, this local treatment strategy avoids the systemic toxicity associated with traditional chemotherapy to excretory organs. This dual-functional strategy represents a significant advancement in bone cancer treatment, offering a safe and more efficient alternative that could improve outcomes for patients following bone tumor resection.

Effect of Surface Morphologies on the In Vitro and In Vivo Properties of Biomedical Metallic Materials

Metallic biomaterials, including traditional bioinert materials (such as stainless steel, cobalt-chromium alloys, pure titanium, and titanium alloys), novel biodegradable metals (such as pure magnesium and magnesium alloys, pure zinc and zinc alloys, and pure iron and iron alloys), and biomedical metallic glasses, have been widely used and studied as various biomedical implants and devices. Many scientists and researchers have investigated their superior biomechanical properties, corrosion behavior, and biocompatibility. However, their surface characteristics are of extreme importance due to continuing interactions between the surface/interface of an implanted metallic biomaterial and the surrounding physiological environment. Surface morphologies on these metallic biomaterials can modulate their in vitro and in vivo biological responses. In this review, we have summarized and investigated the effect of various surface morphologies on the corrosion behavior, cellular response, antibacterial activity, and osteogenesis of biomedical metallic materials. In addition, future research directions and challenges of surface morphologies on biomedical metallic materials have been elaborated. This review can lay a theoretical and practical foundation for further research and development on biomedical metallic materials.

Why Animal Experiments Are Still Indispensable in Bone Research: A Statement by the European Calcified Tissue Society

Major achievements in bone research have always relied on animal models and in vitro systems derived from patient and animal material. However, the use of animals in research has drawn intense ethical debate and the complete abolition of animal experimentation is demanded by fractions of the population. This phenomenon is enhanced by the reproducibility crisis in science and the advance of in vitro and in silico techniques. 3D culture, organ-on-a-chip, and computer models have improved enormously over the last few years. Nevertheless, the overall complexity of bone tissue cross-talk and the systemic and local regulation of bone physiology can often only be addressed in entire vertebrates. Powerful genetic methods such as conditional mutagenesis, lineage tracing, and modeling of the diseases enhanced the understanding of the entire skeletal system. In this review endorsed by the European Calcified Tissue Society (ECTS), a working group of investigators from Europe and the US provides an overview of the strengths and limitations of experimental animal models, including rodents, fish, and large animals, as well the potential and shortcomings of in vitro and in silico technologies in skeletal research. We propose that the proper combination of the right animal model for a specific hypothesis and state-of-the-art in vitro and/or in silico technology is essential to solving remaining important questions in bone research. This is crucial for executing most efficiently the 3R principles to reduce, refine, and replace animal experimentation, for enhancing our knowledge of skeletal biology, and for the treatment of bone diseases that affect a large part of society. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Evaluating material-driven regeneration in a tissue engineered human in vitro bone defect model

Advanced in vitro human bone defect models can contribute to the evaluation of materials for in situ bone regeneration, addressing both translational and ethical concerns regarding animal models. In this study, we attempted to develop such a model to study material-driven regeneration, using a tissue engineering approach. By co-culturing human umbilical vein endothelial cells (HUVECs) with human bone marrow-derived mesenchymal stromal cells (hBMSCs) on silk fibroin scaffolds with in vitro critically sized defects, the growth of vascular-like networks and three-dimensional bone-like tissue was facilitated. After a model build-up phase of 28 days, materials were artificially implanted and HUVEC and hBMSC migration, cell-material interactions, and osteoinduction were evaluated 14 days after implantation. The materials physiologically relevant for bone regeneration included a platelet gel as blood clot mimic, cartilage spheres as soft callus mimics, and a fibrin gel as control. Although the in vitro model was limited in the evaluation of immune responses, hallmarks of physiological bone regeneration were observed in vitro. These included the endothelial cell chemotaxis induced by the blood clot mimic and the mineralization of the soft callus mimic. Therefore, the present in vitro model could contribute to an improved pre-clinical evaluation of biomaterials while reducing the need for animal experiments.

MicroRNA-196a-5p overexpression in Wharton's jelly umbilical cord stem cells promotes their osteogenic differentiation and new bone formation in bone defects in the rat calvarium

The peri-tooth root alveolar loss often does not have sufficient space for repair material transplantation and plasticity. Mesenchymal stem cell (MSC) sheets have an advantage in providing more extracellular matrix (ECM) and may prove to be a new therapeutic consideration for this bone defect repair. The identification of key regulators that stimulate MSCs' osteogenic potential and sheet-derived ECM deposition is the key to promoting its application. In this study, we found that inhibition or overexpression of miR-196a-5p led to a decline or enhancement, respectively, in the alkaline phosphatase (ALP) activity, mineralization, and the levels of osteogenic markers, Osteocalcin (OCN), Dentin Matrix Protein 1 (DMP1), Bone Sialoprotein (BSP), and Dentin Sialophosphoprotein (DSPP) of Wharton's jelly of umbilical cord stem cells (WJCMSCs) in vitro. Moreover, the 5,6-Carboxyfluorescein Diacetate Succinimidyl Ester (CFSE) analysis revealed inhibition of the WJCMSCs' proliferative ability upon miR-196a-5p overexpression. Characterization of the sheet formation by picrosirius red and Masson staining indicated that miR-196a-5p overexpression significantly promoted the collagen content in whole WJCMSC sheet-derived ECM. Furthermore, micro-CT and histopathology results indicated that the miR-196a-5p-overexpressed WJCMSC sheets significantly promoted new bone regeneration and rat calvarial bone defect closure 12 weeks following transplantation. The mRNA microarray analysis of miR-196a-5p-overexpressed WJCMSCs revealed 959 differentially expressed genes (DEGs) (34 upregulated and 925 downregulated). Moreover, 241 genes targeted by miR-196a-5p were predicted by using miRNA function websites of which only 19 predicted genes were consistent with the microarray revealed DEGs. Hence, one unrevealed downregulated DEG Serpin Family B Member 2 (SERPINB2) was investigated. And the deletion of SERPINB2 enhanced the ALP activity and mineralization of WJCMSCs in vitro. In conclusion, our study found that miR-196a-5p, as a key regulator, could repress the proliferation tendency, while stimulating osteogenic ability and WJCMSC sheet-derived ECM deposition, thus promoting new bone formation and rat calvarial bone defect closure. Furthermore, SERPINB2 is a key downstream gene involved in the miR-196a-5p-promoted WJCMSC osteogenesis.