Impact of Release Kinetics on Efficacy of Locally Delivered Parathyroid Hormone for Bone Regeneration Applications

The local pulsatile parathyroid hormone delivery system induces the osteogenic differentiation of dental pulp mesenchymal stem cells to reconstruct mandibular defects

BACKGROUND

Tumors and injuries often lead to large mandibular defects. Accelerating the osteogenesis of large bone defect areas is a major concern in current research. In this study, dental pulp mesenchymal stem cells (DPSCs) were used as seed cells, and the local pulsatile parathyroid hormone (PTH) delivery system was used as an osteogenic-inducing active ingredient to act on DPSCs and osteoblasts, which were applied to the jaw defect area to evaluate its therapeutic effect on bone regeneration.

METHODS

Pulsatile delivery systems, both with and without PTH, were developed following the protocols outlined in our previous study. In vitro, the biocompatibility of the pulsatile delivery system with DPSCs was assessed using the Cell Counting Kit-8 (CCK8) assay and live/dead cell staining. Osteogenic differentiation was evaluated through alkaline phosphatase staining and alizarin red staining. In vivo, critical bone defects with a diameter of 10 mm were created in the mandibles of white rabbits. The osteogenic effect was further assessed through gross observation, X-ray imaging, and histological examination.

RESULTS

In vitro experiments using CCK8 assays and live/dead cell staining demonstrated that DPSCs successfully adhered to the surface of the PTH pulsatile delivery system, showing no significant difference compared to the control group. Furthermore, alkaline phosphatase staining and Alizarin Red staining confirmed that the localized pulsatile parathyroid hormone delivery system effectively induced the differentiation of DPSCs into osteoblasts, leading to the secretion of abundant calcium nodules. Animal studies further revealed that the PTH pulsatile delivery system promoted the osteogenic differentiation of DPSCs, facilitating the repair of critical mandibular bone defects.

CONCLUSION

The rhythmic release of PTH from the pulsatile delivery system effectively induces the osteogenic differentiation of DPSCs. By leveraging the synergistic interaction between PTH and DPSCs, this approach facilitates the repair of extensive mandibular bone defects.

Hydrogel-Based Scaffolds: Advancing Bone Regeneration Through Tissue Engineering

Bone tissue engineering has emerged as a promising approach to addressing the limitations of traditional bone grafts for repairing bone defects. This regenerative medicine strategy leverages biomaterials, growth factors, and cells to create a favorable environment for bone regeneration, mimicking the body's natural healing process. Among the various biomaterials explored, hydrogels (HGs), a class of three-dimensional, hydrophilic polymer networks, have gained significant attention as scaffolds for bone tissue engineering. Thus, this review aimed to investigate the potential of natural and synthetic HGs, and the molecules used for its functionalization, for enhanced bone tissue engineering applications. HGs offer several advantages such as scaffolds, including biocompatibility, biodegradability, tunable mechanical properties, and the ability to encapsulate and deliver bioactive molecules. These properties make them ideal candidates for supporting cell attachment, proliferation, and differentiation, ultimately guiding the formation of new bone tissue. The design and optimization of HG-based scaffolds involve adapting their composition, structure, and mechanical properties to meet the specific requirements of bone regeneration. Current research focuses on incorporating bioactive molecules, such as growth factors and cytokines, into HG scaffolds to further enhance their osteoinductive and osteoconductive properties. Additionally, strategies to improve the mechanical strength and degradation kinetics of HGs are being explored to ensure long-term stability and support for new bone formation. The development of advanced HG-based scaffolds holds great potential for revolutionizing bone tissue engineering and providing effective treatment options for patients with bone defects.

Stimulation of fracture mineralization by salt-inducible kinase inhibitors

Introduction

Over 6.8 million fractures occur annually in the US, with 10% experiencing delayed- or non-union. Anabolic therapeutics like PTH analogs stimulate fracture repair, and small molecule salt inducible kinase (SIK) inhibitors mimic PTH action. This study tests whether the SIK inhibitor YKL-05-099 accelerates fracture callus osteogenesis.

Methods

126 female mice underwent femoral shaft pinning and midshaft fracture, receiving daily injections of PBS, YKL-05-099, or PTH. Callus tissues were analyzed via RT-qPCR, histology, single-cell RNA-seq, and μCT imaging. Biomechanical testing evaluated tissue rigidity. A hydrogel-based delivery system for PTH and siRNAs targeting SIK2/SIK3 was developed and tested.

Results

YKL-05-099 and PTH-treated mice showed higher mineralized callus volume fraction and improved structural rigidity. RNA-seq indicated YKL-05-099 increased osteoblast subsets and reduced chondrocyte precursors. Hydrogel-released siRNAs maintained target knockdown, accelerating callus mineralization.

Discussion

YKL-05-099 enhances fracture repair, supporting selective SIK inhibitors' development for clinical use. Hydrogel-based siRNA delivery offers targeted localized treatment at fracture sites.

Enhanced bone tissue regeneration with hydrogel-based scaffolds by embedding parathyroid hormone in mesoporous bioactive glass

OBJECTIVES

To evaluate hydrogel-based scaffolds embedded with parathyroid hormone (PTH)-loaded mesoporous bioactive glass (MBG) on the enhancement of bone tissue regeneration in vitro.

MATERIALS AND METHODS

MBG was produced via sol-gel technique followed by PTH solution imbibition. PTH-loaded MBG was blended into the hydrogels and submitted to a lyophilisation process associated with a chemical crosslinking reaction to the production of the scaffolds. Characterisation of the MBG and PTH-loaded MBG scaffolds, including the scanning electron microscope (SEM) connected with an X-ray detector (EDX), Fourier transform infrared (FTIR), compression strength, rheological measurements, swelling and degradation rates, and PTH release analysis, were performed. Also, bioactivity using simulated-body fluid (SBF), biocompatibility (MTT), and osteogenic differentiation analyses (von Kossa and Alizarin Red stainings, and μ-computed tomography, μCT) of the scaffolds were carried out.

RESULTS

SEM images demonstrated MBG particles dispersed into the hydrogel-based scaffold structure, which was homogeneously porous and well interconnected. EDX and FTIR revealed large amounts of carbon, oxygen, sodium, and silica in the scaffold composition. Bioactivity experiments revealed changes on sample surfaces over the analysed period, indicating the formation of carbonated hydroxyapatite; however, the chemical composition remained stable. PTH-loaded hydrogel-based scaffolds were biocompatible for stem cells from human-exfoliated deciduous teeth (SHED). A high quantity of calcium deposits on the extracellular matrix of SHED was found for PTH-loaded hydrogel-based scaffolds. μCT images showed MBG particles dispersed into the scaffolds' structure, and a porous, lamellar, and interconnected hydrogel architecture.

CONCLUSIONS

PTH-loaded hydrogel-based scaffolds demonstrated consistent morphology and physicochemical properties for bone tissue regeneration, as well as bioactivity, biocompatibility, and osteoinductivity in vitro. Thus, the scaffolds presented here are recommended for future studies on 3D printing.

CLINICAL RELEVANCE

Bone tissue regeneration is still a challenge for several approaches to oral and maxillofacial surgeries, though tissue engineering applying SHED, scaffolds, and osteoinductive mediators might help to overcome this clinical issue.

Effects of local single dose administration of parathormone on the early stages of osseointegration: A pre-clinical study

The present study aimed to evaluate the effect of parathormone (PTH) administered directly to the implant's surface prior to insertion, using a large translational animal model. Sixty titanium implants were divided into four groups: (i) Collagen, control group, where implants were coated with Type-I Bovine-collagen, and three experimental groups, where implants received varying doses of PTH: (ii) 12.5, (iii) 25, and (iv) 50 μg, prior to placement. Fifteen female sheep (~2 years old, weighing ~65 kg) received four implants in an interpolated fashion in C3, C4 or C5 vertebral bodies. After 3-, 6- and 12-weeks, samples were harvested, histologically processed, qualitatively and quantitatively assessed for bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). BIC yielded lower values at 6-weeks for 50 μg relative to the control group, with no significant differences, when compared to the 12.5- and 25-μg. No significant differences were detected at 6-weeks between collagen, 12.5- and 25-μg groups. At 3- and 12-weeks, no differences were detected for BIC among PTH groups. With respect to BAFO, no significant differences were observed between the control and experimental groups independent of PTH concentration and time in vivo. Qualitative observations at 3-weeks indicated the presence of a more mature bone near the implant's surface with the application of PTH, however, no significant differences in new bone formation or healing patterns were observed at 6- and 12-weeks. Single local application of different concentrations of PTH on titanium implant's surface did not influence the osseointegration at any time-point evaluation in low-density bone.

Clinical Application of Bone Marrow Mesenchymal Stem/Stromal Cells to Repair Skeletal Tissue

There has been an escalation in reports over the last decade examining the efficacy of bone marrow derived mesenchymal stem/stromal cells (BMSC) in bone tissue engineering and regenerative medicine-based applications. The multipotent differentiation potential, myelosupportive capacity, anti-inflammatory and immune-modulatory properties of BMSC underpins their versatile nature as therapeutic agents. This review addresses the current limitations and challenges of exogenous autologous and allogeneic BMSC based regenerative skeletal therapies in combination with bioactive molecules, cellular derivatives, genetic manipulation, biocompatible hydrogels, solid and composite scaffolds. The review highlights the current approaches and recent developments in utilizing endogenous BMSC activation or exogenous BMSC for the repair of long bone and vertebrae fractures due to osteoporosis or trauma. Current advances employing BMSC based therapies for bone regeneration of craniofacial defects is also discussed. Moreover, this review discusses the latest developments utilizing BMSC therapies in the preclinical and clinical settings, including the treatment of bone related diseases such as Osteogenesis Imperfecta.