Tips and techniques for processing and sectioning undecalcified murine bone specimens

3D Biomimetic Porous Titanium (Ti6Al4V ELI) Scaffolds for Large Bone Critical Defect Reconstruction: An Experimental Study in Sheep

Simple Summary

The authors propose a new reconstructive technique that proved to be suitable to reach this purpose through the use of a custom-made biomimetic porous titanium scaffold. An in vivo study was undertaken where a complete critical defect was experimentally created in the diaphysis of the right tibia of twelve sheep and replaced with a five-centimeter porous scaffold of electron beam melting (EBM)-manufactured titanium alloy or a porous hydroxyapatite scaffold. Our results show that EBM-formed titanium devices, if used to repair critical bone defects in a large animal model, can guarantee immediate body weight-bearing, a rapid functional recovery, and a good osseointegration. The porous hydroxyapatite scaffolds proved to be not suitable in this model of large bone defect due to their known poor mechanical properties.

Abstract

The main goal in the treatment of large bone defects is to guarantee a rapid loading of the affected limb. In this paper, the authors proposed a new reconstructive technique that proved to be suitable to reach this purpose through the use of a custom-made biomimetic porous titanium scaffold. An in vivo study was undertaken where a complete critical defect was experimentally created in the diaphysis of the right tibia of twelve sheep and replaced with a five-centimeter porous scaffold of electron beam melting (EBM)-sintered titanium alloy (EBM group n = 6) or a porous hydroxyapatite scaffold (CONTROL group, n = 6). After surgery, the sheep were allowed to move freely in the barns. The outcome was monitored for up to 12 months by periodical X-ray and clinical examination. All animals in the CONTROL group were euthanized for humane reasons within the first month after surgery due to the onset of plate bending due to mechanical overload. Nine months after surgery, X-ray imaging showed the complete integration of the titanium implant in the tibia diaphysis and remodeling of the periosteal callus, with a well-defined cortical bone. At 12 months, sheep were euthanized, and the tibia were harvested and subjected to histological analysis. This showed bone tissue formations with bone trabeculae bridging titanium trabeculae, evidencing an optimal tissue-metal interaction. Our results show that EBM-sintered titanium devices, if used to repair critical bone defects in a large animal model, can guarantee immediate body weight-bearing, a rapid functional recovery, and a good osseointegration. The porous hydroxyapatite scaffolds proved to be not suitable in this model of large bone defect due to their known poor mechanical properties.

A modified tape transfer approach for rapidly preparing high-quality cryosections of undecalcified adult rodent bones

Background/Objective

Histology-based analyses are important tools to dissect cellular and molecular mechanisms of skeletal homeostasis, diseases, and regeneration. The success of these efforts is highly dependent on rapidly obtaining high-quality sections of mineralized skeletal tissues suitable for various analyses. However, the current techniques for preparing such sections are still far from satisfactory. This study aimed to develop a new approach for preparing high-quality undecalcified bone sections applicable to various histological analyses.

Methods

Two important modifications were made to the conventional Cryojane Tape-Transfer System, including utilization of an optimized adhesive to prepare adhesive glass slides for improving the transfer efficiency, and a cheap conventional benchtop UV transilluminator for UV curing. Cryosections of undecalcified rodent bones were prepared using this modified tape transfer approach, and their tissue morphology and structural integrity were visually examined. A variety of histological analyses, including calcein labeling, Von kossa staining, immunofluorescence, and enzymatic activity staining as well as 5-Ethynyl-2’-deoxyuridine (EdU) and TUNEL assays, were performed on these sections.

Results

We developed a modified version of tape transfer approach that can prepare cryosections of undecalcified rodent adult bones within 4 days at a low cost. Bone sections prepared by this approach exhibited good tissue morphology and structural integrity. Moreover, these sections were applicable to a variety of histological analyses, including calcein labeling, Von kossa staining, immunofluorescence, and enzymatic activity staining as well as EdU and TUNEL assays.

Conclusion

The tape transfer approach we developed provides a rapid, affordable, and easy learning method for preparing high-quality undecalcified bone sections valuable for bone research.

The translational potential of this article

Our research provides a rapid, affordable, and easy learning method for preparing high-quality undecalcified bone sections that can be potentially used for accurate diagnosis of various bone disorders and evaluation of the efficacy of different therapies in the treatment of these diseases.

Fluorescent Sulfonate-Based Inorganic-Organic Hybrid Nanoparticles for Staining and Imaging

Sulfonate-based inorganic-organic hybrid nanoparticles (IOH-NPs) with the general saline composition [Gd(OH)]²⁺_n/2[ R_dye(SO₃) _n] ^n- showing optical absorption and emission in the blue to red spectral regime are presented for the first time. All IOH-NPs are prepared via straightforward aqueous synthesis and instantaneously result in colloidally highly stable suspensions with mean particle diameters of 40-50 nm and high zeta potentials (-20 to -40 mV at pH 7.0). Specifically, the IOH-NPs comprise [Gd(OH)]²⁺₂[CSB]^4-, [Gd(OH)]²⁺₂[DB71]^4-, [Gd(OH)]²⁺[NFR]^2-, [Gd(OH)]²⁺[AR97]^2-, and [Gd(OH)]²⁺₂[EB]^4- showing blue, orange, red, and infrared absorption and emission ([CSB]: Chicago Sky Blue; [DB71]: Direct Blue 71; [NFR]: Nuclear Fast Red; [AR97]: Acid Red 97; [EB]: Evans Blue). The novel IOH-NPs are characterized by electron microscopy, dynamic light scattering, infrared spectroscopy, energy-dispersive X-ray analysis, thermogravimetry, elemental analysis, and fluorescence spectroscopy. In vitro studies based on HeLa and HUVEC cells were exemplarily performed with [Gd(OH)]²⁺₂[EB]^4- IOH-NPs and show intense fluorescence and only moderate toxicity at concentrations of 1 to 10 μg/mL. Based on aqueous synthesis, good colloidal stability, absence of severely toxic metals (e.g., Cd²⁺, Pb²⁺), use of molecular dyes that are already known for staining in cell biology and histology, extremely high dye load per nanoparticle (70-80 wt %), and blue to red absorption and fluorescence, the sulfonate-based IOH-NPs can be highly interesting for staining, fluorescence microscopy, and optical imaging.

Effects of fructose-induced metabolic syndrome on rat skeletal cells and tissue, and their responses to metformin treatment

AIMS

Deleterious effects of metabolic syndrome (MS) on bone are still controversial. In this study we evaluated the effects of a fructose-induced MS, and/or an oral treatment with metformin on the osteogenic potential of bone marrow mesenchymal stromal cells (MSC), as well as on bone formation and architecture.

METHODS

32 male 8week-old Wistar rats were assigned to four groups: control (C), control plus oral metformin (CM), rats receiving 10% fructose in drinking water (FRD), and FRD plus metformin (FRDM). Samples were collected to measure blood parameters, and to perform pQCT analysis and static and dynamic histomorphometry. MSC were isolated to determine their osteogenic potential.

RESULTS

Metformin improved blood parameters in FRDM rats. pQCT and static and dynamic histomorphometry showed no significant differences in trabecular and cortical bone parameters among groups. FRD reduced TRAP expression and osteocyte density in trabecular bone and metformin only normalized osteocyte density. FRD decreased the osteogenic potential of MSC and metformin administration could revert some of these parameters.

CONCLUSIONS

FRD-induced MS shows reduction in MSC osteogenic potential, in osteocyte density and in TRAP activity. Oral metformin treatment was able to prevent trabecular osteocyte loss and the reduction in extracellular mineralization induced by FRD-induced MS.