Bioactive composite hydrogels as 3D mesenchymal stem cell encapsulation environment for bone tissue engineering: in vitro and in vivo studies

Although decellularized bone matrix (DBM) has often been used in scaffold form for osteogenic applications, its use as a stem cell encapsulation matrix adaptable to surgical shaping procedures has been neglected. This study aimed to investigate the feasibility of utilizing solubilized DBM and nanohydroxyapatite (nHAp)-incorporated DBM hydrogels as encapsulation matrix for bone marrow-derived MSCs (BM-MSCs). First, DBM and DBM/nHAp hydrogels were assessed by physical, chemical, turbidimetric, thermal, and mechanical methods; then, in vitro cytocompatibility and in vitro hemocompatibility were investigated. An in vivo study was performed to evaluate the osteogenic properties of hydrogels alone or with BM-MSCs encapsulated in them. The findings revealed that hydrogels retained high levels of collagen and glycosaminoglycans after successful decellularization. They were found to be cytocompatible and hemocompatible in vitro, and were able to gel with sufficient mechanical stability at physiological temperature. BM-MSCs survived in culture for at least 2 weeks as metabolically active when encapsulated in both DBM and DBM/nHAp. Preliminary in vivo study showed that DBM-nHAp has higher osteogenicity than DBM. Moreover, BM-MSC encapsulated DMB/nHAp showed predominant bone-like tissue formation at 30 days in the rat ectopic site compared to its cell-free form.

[The 3D-printed surgical guides used during genioplasty]

Genioplasty is a seemingly simple procedure performed to correct the bony chin. The results of the procedure are, however, strongly correlated with the experience of the surgeon. 3D-printed surgical guides could act as a transfer modality to translate the preoperative planning directly into the achieved result. Prospective studies evaluating the usefulness of the 3D-printed surgical guides have not yet been carried out and consensus regarding the best design is lacking. In order to become more familiar with working with surgical guides, a genioplasty using 3D-printed surgical guides was performed. The postoperative analysis of the achieved result showed minor differences compared to preoperative planning. Surgical guides have the potential to improve the accuracy and predictability of genioplasty. The design should be further refined and the added value of the guides should be confirmed by means of prospective research.

Decellularized liver ECM-based 3D scaffolds: Compositional, physical, chemical, rheological, thermal, mechanical, and in vitro biological evaluations

The extracellular matrix (ECM) is involved in many critical cellular interactions through its biological macromolecules. In this study, a macroporous 3D scaffold originating from decellularized bovine liver ECM (dL-ECM), with defined compositional, physical, chemical, rheological, thermal, mechanical, and in vitro biological properties was developed. First, protocols were determined that effectively remove cells and DNA while ECM retains biological macromolecules collagen, elastin, sGAGs in tissue. Rheological analysis revealed the elastic properties of pepsin-digested dL-ECM. Then, dL-ECM hydrogel was neutralized, molded, formed into macroporous (~100-200 μm) scaffolds in aqueous medium at 37 °C, and lyophilized. The scaffolds had water retention ability, and were mechanically stable for at least 14 days in the culture medium. The findings also showed that increasing the dL-ECM concentration from 10 mg/mL to 20 mg/mL resulted in a significant increase in the mechanical strength of the scaffolds. The hemolysis test revealed high in vitro hemocompatibility of the dL-ECM scaffolds. Studies investigating the viability and proliferation status of human adipose stem cells seeded over a 2-week culture period have demonstrated the suitability of dL-ECM scaffolds as a cell substrate. Prospective studies may reveal the extent to which 3D dL-ECM sponges have the potential to create a biomimetic environment for cells.

Decellularized Cell Culture ECMs Act as Cell Differentiation Inducers

Decellularized tissues and organs have aroused considerable interest for developing functional bio-scaffolds as natural templates in tissue engineering applications. More recently, the use of natural extracellular matrix (ECM) extracted from the in vitro cell cultures for cellular applications have come into question. It is well known that the microenvironment largely defines cellular properties. Thus, we have anticipated that the ECMs of the cells with different potency levels should likely possess different effects on cell cultures. To test this, we have comparatively evaluated the differentiative effects of ECMs derived from the cultures of human somatic dermal fibroblasts, human multipotent bone marrow mesenchymal stem cells, and human induced pluripotent stem cells on somatic dermal fibroblasts. Although challenges remain, the data suggest that the use of cell culture-based extracellular matrices perhaps may be considered as an alternative approach for the differentiation of even somatic cells into other cell types.

Magneto-sensitive decellularized bone matrix with or without low frequency-pulsed electromagnetic field exposure for the healing of a critical-size bone defect

Bioactive ECM-based materials mimic the complex composition and structure of natural tissues. Decellularized cancellous bone matrix (DBM) has potential for guiding new bone formation and accelerating the regeneration process. On the other hand, low frequency-pulsed electromagnetic field (LF-PEMF) has been shown to enhance the regeneration capacity of bone defects. The present study sought to explore the feasibility of using DBM and DBM/MNP, and LF-PEMF for treating critical-size bone defects. Firstly, decellularization protocol was optimized to obtain a bioactive DBM, then MNPs were incorporated. Later, the physical, chemical and biological properties of DBM and DBM/MNP were assessed in vitro. MNPs homogeneously distributed into the DBM were not found to be toxic to human osteoblast cultures. Finally, an in vivo study was carried out with DBM and DBM/MNP composites in a bilateral critical-size rat cranial defect model (n = 48) with or without LF-PEMF exposure for 45 and 90 days. The histomorphometric and radiographic evaluations revealed that, while the collagen (positive control) and Sham (negative control) groups showed high incidence of fibrous connective tissue together with low level of osteogenic activity, both the DBM and DBM/MNP-grafted groups significantly promoted new bone tissue formation and angiogenesis, by the appropriate use of LF-PEMF for 90 days.

Development of a multicellular 3D-bioprinted microtissue model of human periodontal ligament-alveolar bone biointerface: Towards a pre-clinical model of periodontal diseases and personalized periodontal tissue engineering

While periodontal (PD) disease is among principal causes of tooth loss worldwide, regulation of concomitant soft and mineralized PD tissues, and PD pathogenesis have not been completely clarified yet. Besides, relevant pre-clinical models and in vitro platforms have limitations in simulating human physiology. Here, we have harnessed three-dimensional bioprinting (3DBP) technology for developing a multi-cellular microtissue model resembling PD ligament-alveolar bone (PDL-AB) biointerface for the first time. 3DBP parameters were optimized; the physical, chemical, rheological, mechanical, and thermal properties of the constructs were assessed. Constructs containing gelatin methacryloyl (Gel-MA) and hydroxyapatite-magnetic iron oxide nanoparticles showed higher level of compressive strength when compared with that of Gel-MA constructs. Bioprinted self-supporting microtissue was cultured under flow in a microfluidic platform for >10 days without significant loss of shape fidelity. Confocal microscopy analysis indicated that encapsulated cells were homogenously distributed inside the matrix and preserved their viability for >7 days under microfluidic conditions. Immunofluorescence analysis showed the cohesion of stromal cell surface marker-1+ human PDL fibroblasts containing PDL layer with the osteocalcin+ human osteoblasts containing mineralized layer in time, demonstrating some permeability of the printed constructs to cell migration. Preliminary tetracycline interaction study indicated the uptake of model drug by the cells inside the 3D-microtissue. Also, the non-toxic levels of tetracycline were determined for the encapsulated cells. Thus, the effects of tetracyclines on PDL-AB have clinical significance for treating PD diseases. This 3D-bioprinted multi-cellular periodontal/osteoblastic microtissue model has potential as an in vitro platform for studying processes of the human PDL.

A CD34+ Cell Enrichment Protocol of Hematopoietic Stem Cells in a Well-Established Quality Management System

Allogeneic stem cell transplantation applications have improved tremendously over the past quarter of a century. The use of new immunosuppressive protocols and elimination of T cells by CD34+ cell enrichment or T cell depletion on apheresis products increases the chance of using partially matched or haploidentical grafts. This is without increasing the risk of graft-versus-host disease, which is observed as a major complication of hematopoietic stem cell transplantation. The aim of this protocol is to evaluate the results obtained from 6 different process cycles performed on 6 different days. We used the CliniMACS Plus system located in our Cell and Tissue Manufacturing Center Quality Control Unit which is already calibrated as a class D room and includes a class A microbiological safety cabinet inside. The average purity of the end products was 95.66%, excluding only one end product which was 70%; this was higher than the values in current studies in the field. Superior to the reported studies, the CD3 quantity in each end product was below the dedicated thresholds. BactecTM FX40 blood culture system test results were detected as negative for each end product. Endotoxin testing suggested the absence of endotoxin within the products. The consistent outcomes obtained from these 6 different process cycles confirmed that the CliniMACS® Plus process cycles performed in accordance with our well-defined quality management system procedure is sufficient for the routine application of high-quality and safe CD34+ enrichment processes within our clean room area.

Investigations on clonazepam-loaded polymeric micelle-like nanoparticles for safe drug administration during pregnancy

Medication during pregnancy is often a necessity for women to treat their acute or chronic diseases. The goal of this study is to evaluate the potential of micelle-like nanoparticles (MNP) for providing safe drug usage in pregnancy and protect both foetus and mother from medication side effects. Clonazepam-loaded MNP were prepared from copolymers [polystyrene-poly(acrylic acid) (PS-PAA), poly(ethylene glycol)-b-poly(lactic acid) (PEG-PLA) and distearyl-sn-glycero-3-phosphoethanolamine-N-[methoxy-poly(ethylene glycol) (PEG-DSPE)] with varying monomer ratios and their drug-loading efficiency, drug release ratio, particle size, surface charge and morphology were characterised. The cellular transport and cytotoxicity experiments were conducted on clonazepam and MNP formulations using placenta-choriocarcinoma-BeWo and brain-endothelial-bEnd3 cells. Clonazepam-loaded PEG₅₀₀₀-PLA₄₅₀₀ MNP reduced the drug transport through BeWo cells demonstrating that MNP may lower foetal drug exposure, thus reduce the drug side effects. However, lipofectamine modified MNP improved the transport of clonazepam and found to be promising for brain and in-utero-specific drug treatment.

Decellularization of Bovine Small Intestinal Submucosa

Decellularization technology promises to overcome some of the significant limitations in the regenerative medicine field by providing functional biocompatible grafts. The technique involves removal of the cells from the biological tissues or organs for further use in tissue engineering and clinical interventions. There are significant differences between decellularization protocols due to the intrinsic properties of different tissue types and purpose of use. This multistep, chemical-solution-based protocol is optimized for the preparation of decellularized bovine small intestinal submucosa (SIS).

Time-Resolved Fluorescence Resonance Energy Transfer [TR-FRET] Assays for Biochemical Processes

Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) is a fluorescence based technique which enables the analysis of molecular interactions in biochemical processes. Principle of TR-FRET is based on time-resolved fluorescence (TRF) measurement and fluorescence resonance energy transfer (FRET) between donor and acceptor molecules. To generate FRET signal, donor and acceptor molecules must show spectral overlap and should be in close proximity to each other and display suitable dipole orientation. The specific signal is acquired from molecules of interest via interactions of donor and acceptor molecules. TR-FRET technique is widely used for studying kinase assays, cellular signaling pathways, protein-protein interactions, DNA-protein interactions, and receptor-ligand binding. There are various propriety applications of TR-FRET. Two different sample protocols are summarized in this review.