Dual-functional thermosensitive hydrogel for reducing infection and enhancing bone regeneration in infected bone defects

The contamination of bone defects is a serious therapeutic problem. The treatment of infected bone defects involves rigorous infection control followed by bone reconstruction. Considering these two processes, the development of biomaterials possessing antibacterial and osteogenic properties offers a promising approach for the treatment of infected bone defects. In this study, a dual-functional, thermosensitive, and injectable hydrogel composed of chitosan (CS), quaternized CS (QCS), and nano-hydroxyapatite (nHA) was designed, and the ratio of CS to QCS in the hydrogel was optimized to enhance the antibacterial efficacy of CS while reducing the cytotoxicity of QCS. In vitro studies demonstrated that the hydrogel with an 85 %:15 % ratio of CS to QCS exhibited excellent biocompatibility and antibacterial properties while also possessing suitable mechanical characteristics and degradability. The incorporation of nHA into the hydrogel enhanced MC3T3-E1 proliferation and osteogenic differentiation. Moreover, this hydrogel demonstrated superior in vivo therapeutic effectiveness in a rabbit model of infected bone defect. In summary, this study provides a promising material design and a comprehensive one-step treatment strategy for infected bone defects.

Nanoparticle-Based Drug Delivery Systems for Enhancing Bone Regeneration

The treatment of bone defects has been a long-standing challenge in clinical practice. Among the various bone tissue engineering approaches, there has been substantial progress in the development of drug delivery systems based on functional drugs and appropriate carrier materials owing to technological advances in recent years. A large number of materials based on functional nanocarriers have been developed and applied to improve the complex osteogenic microenvironment, including for promoting osteogenic activity, inhibiting osteoclast activity, and exerting certain antibacterial effects. This Review discusses the physicochemical properties, drug loading mechanisms, advantages and disadvantages of nanoparticles (NPs) used for constructing drug delivery systems. In addition, we provide an overview of the osteogenic microenvironment regulation mechanism of drug delivery systems based on nanoparticle (NP) carriers and the construction strategies of drug delivery systems. Finally, the advantages and disadvantages of NP carriers are summarized along with their prospects and future research trends in bone tissue engineering. This Review thus provides advanced strategies for the design and application of drug delivery systems based on NPs in the treatment of bone defects.

Drug delivery systems based on polyethylene glycol hydrogels for enhanced bone regeneration

Drug delivery systems composed of osteogenic substances and biological materials are of great significance in enhancing bone regeneration, and appropriate biological carriers are the cornerstone for their construction. Polyethylene glycol (PEG) is favored in bone tissue engineering due to its good biocompatibility and hydrophilicity. When combined with other substances, the physicochemical properties of PEG-based hydrogels fully meet the requirements of drug delivery carriers. Therefore, this paper reviews the application of PEG-based hydrogels in the treatment of bone defects. The advantages and disadvantages of PEG as a carrier are analyzed, and various modification methods of PEG hydrogels are summarized. On this basis, the application of PEG-based hydrogel drug delivery systems in promoting bone regeneration in recent years is summarized. Finally, the shortcomings and future developments of PEG-based hydrogel drug delivery systems are discussed. This review provides a theoretical basis and fabrication strategy for the application of PEG-based composite drug delivery systems in local bone defects.

Minimally invasive plate osteosynthesis for complex comminuted bone fractures in the Fraser's type II floating knee: a case report

Objective

Floating knee type IIC, according to Fraser’s classification, is an uncommon severe injury that typically occurs in polytrauma. In such cases, intra-articular fracture and the high degree of comminution and deformity of the mid-distal femur make fixation challenging. The purpose of this study was to demonstrate that minimally invasive plate osteosynthesis (MIPO) technology can simplify these complex problems and improve patient prognosis.

Case presentation

A 38-year-old man injured his left leg in a car accident, causing pain, swelling, deformity, and limited mobility on his left knee and thigh, and two small open wounds were noted mainly of the anterior aspect of the mid-distal thigh. Physical examination and computed tomography angiography of the lower limb confirmed that there was no damage to the neurovascular system. The clinical diagnosis was closed intra-articular fracture of the proximal tibia, open intra-articular fracture of the distal femur with extension to the diaphysis, and a patellar fracture on the ipsilateral knee. The treatment strategy involved a locking plate system applying MIPO technology. Postoperative evaluation of the patient was satisfactory, with immediate functional exercise, full weight-bearing after three months, and return to daily activity without pain. Final follow-up taken 3 years after surgery showed good lower limb alignment and complete plasticity of the bone structure, by which time the patient showed good limb function.

Conclusions

Minimally invasive techniques can provide a simple and effective treatment for some complex fractures.

Abstract P2-09-34: An mRNA-based method to measure PI3K activity in cancer tissue using a computational pathway model to assess FOXO transcriptional activity

Introduction

The PI3K signaling pathway is frequently active in breast cancer, and therapeutic inhibitors have been developed. However, it has proven difficult to correctly predict treatment response. We developed a method that measures functional activity of the PI3K pathway using a computational model that infers transcriptional FOXO activity (downstream of PI3K) from expression levels of its target genes. In principle, PI3K pathway activity inhibits transcriptional FOXO activity, hence inactive FOXO is indicative of active PI3K.

Method

We developed a knowledge-based computational model to infer transcriptional FOXO activity from cancer tissue mRNA expression levels, using a Bayesian network approach (Verhaegh et al., Cancer Res 2014). Model calibration was done on microarray data from HUVEC cells with inducible FOXO3.A3-ER (GSE16573).

Results

The FOXO model was biologically validated with in-house microarray data from independent breast cancer cell lines. ER positive, PIK3CAE545K mutant MCF7 and triple negative MDA-MB-231 cells were stably transduced with a doxycycline inducible FOXO3.A3 expression vector, allowing controlled induction of FOXO3 protein activity. FOXO activity was determined to be low in untreated and 20% FBS treated MCF7 cells, and high after doxycycline, LY294002, and combination treatment.

Next, we tested our FOXO model on independent MCF7, BT-20 and MDA-MB-453 cell line data treated with EGFR inhibitor erlotinib (GSE30516), showing an increase of FOXO activity upon treatment, due to reduced PI3K pathway activity (combined Wilcox rank sum test p = 7.8x10−5).

We further analyzed independent publicly available data from breast cancer patients. FOXO was generally active in healthy breast tissue. Compared to healthy breast tissue, FOXO activity was higher in normal-like and luminal A breast cancer samples (p = 1.9x10−6 and 0.025, resp.), and lower in luminal B samples (p = 4.2x10−7).

In addition to the above mechanism for regulating FOXO activity, literature suggests that FOXO can also be activated by cellular oxidative stress, which is often associated with PI3K signaling. This may be assessed using expression levels of the FOXO target gene SOD2, which is differentially expressed between the two FOXO activity modes, and whose function is to reduce oxidative stress. Public data shows an increasing percentage of elevated SOD2 levels among FOXO-active samples with increasing breast cancer aggressiveness: 7% in normal-like, 5% in luminal A, 18% in luminal B, 31% in HER2-enriched and 74% in basal like breast cancer.

Conclusion

Our computational model to measure PI3K activity using FOXO target gene mRNA levels was able to measure increased FOXO activity in multiple cancer cell lines after PI3K inhibition. FOXO activity was measured high in healthy breast tissue and in normal-like and luminal A breast cancer, and lower in luminal B, indicating PI3K activity in the latter group. In more aggressive subtypes, FOXO activity was increasingly accompanied by high SOD2 expression, suggesting oxidative stress with associated PI3K activity as the FOXO activating mechanism.

Clinical utility for improved response prediction and monitoring of PI3K pathway inhibitors is being investigated with clinical partners.

Citation Format: Verhaegh W, van Ooijen H, Hornsveld M, Dam C, Eijkelenboom A, Dou M, Velter R, Burgering B, van de Stolpe A. An mRNA-based method to measure PI3K activity in cancer tissue using a computational pathway model to assess FOXO transcriptional activity [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-09-34.

TAT‑fused IP3R‑derived peptide enhances cisplatin sensitivity of ovarian cancer cells by increasing ER Ca2+ release

Ovarian cancer is the most common gynecological malignancy. At present, cisplatin is used to treat ovarian cancer; however, the development of cisplatin resistance during therapy is a common obstacle to achieving favorable outcomes. Recently, the B‑cell lymphoma 2 (Bcl‑2) BH4 domain has been reported to mediate the prosurvival activity of Bcl‑2 in cancer; however, the involvement of the BH4 domain of Bcl‑2 in the cisplatin resistance of ovarian carcinoma cells is not entirely clear. In this study, we observed the cytoplasmic and mitochondrial levels of Ca2+ by confocal laser microscopy. We also detected cell apoptosis using western blot analysis and flow cytometry. The present study demonstrated that TAT‑fused inositol 1,4,5‑trisphosphate receptor‑derived peptide (TAT‑IDPS), which targets the BH4 domain of Bcl‑2, increased cisplatin‑induced Ca2+ flux from the endoplasmic reticulum (ER) into the cytosol and mitochondria. In addition, TAT‑IDPS increased cisplatin‑induced expression of mitochondrial apoptosis‑associated proteins and ER stress‑associated proteins. These results indicated that TAT‑IDPS may enhance the cytotoxicity of cisplatin toward ovarian carcinoma cells by increasing ER Ca2+ release.

Thawed human hepatocytes in primary culture

In drug metabolism studies, isolated and cultured human hepatocytes provide a useful model for overcoming the difficulty of extrapolating from animal data. In vitro studies with human hepatocytes are scarce because of the lack of livers and suitable methods of storage. After developing a new method for cryopreservation of human hepatocytes, we evaluated the effects of deep freezing storage on their viability, morphology, and functional and toxicological capabilities in classical culture conditions. Freshly isolated human hepatocytes were cryopreserved in medium containing 10% Me2SO and 20% fetal calf serum, using a Nicool ST20 programmable freezer (-1.9 degrees C/min for 18 min and -30 degrees C/min for 4 min). Cells were stored in liquid nitrogen. Viability of thawed human hepatocytes was 50-65% as assessed by erythrosin exclusion test prior to purification on a Percoll density gradient. Morphological criteria showed that thawed human hepatocytes require an adaptation period to the medium after seeding. Functional assessments showed that human hepatocytes which survive freezing and thawing preserve their protein synthesis capabilities and are able to secrete a specific protein, anionic peptidic fraction, which is involved in the hepatic uptake of bile-destined cholesterol. We then studied Midazolam biotransformation to test metabolic functions, and erythromycin toxicity by Neutral Red test (cell viability) and 3-(4,5-dimethylthiazol-2-yl)-diphenyl tetrazolium bromide test (cell metabolism). All of these experiments indicated that thawed human hepatocytes should be used 38 h after seeding for optimum recovery of their functions: membrane integrity, protein synthesis, and stabilization of drug metabolism enzymes.