Osteogenic capacity of human BM-MSCs, AT-MSCs and their co-cultures using HUVECs in FBS and PL supplemented media

Unraveling mRNA delivery bottlenecks of ineffective delivery vectors by co-transfection with effective carriers

The messenger RNA (mRNA) SARS-CoV-2 vaccines have demonstrated the therapeutic potential of this novel drug modality. Protein expression is the consequence of a multistep delivery process that relies on proper packaging into nanoparticle carriers to protect the mRNA against degradation enabling effective cellular uptake and endosomal release, and liberating the mRNA in the cytosol. Bottlenecks along this route remain challenging to pinpoint. Although methods to assess endosomal escape of carriers have been developed, versatile strategies to identify bottlenecks along the delivery trajectory are missing. Here, it is shown that co-incubating an inefficient nanoparticle formulation with an efficient one solves this problem. Cells were co-incubated with mRNA nanoparticles formed with either the efficient cell-penetrating peptide (CPP) PepFect14 or the inefficient CPP nona-arginine (R9). Co-transfection enhanced cellular uptake and endosomal escape of R9-formulated mRNA, resulting in protein expression, demonstrating that both vectors enter cells along the same route. In addition, cells were transfected with a galectin-9-mCherry fusion protein to detect endosomal rupture. Remarkably, despite endosomal release, mRNA remained confined to punctate structures, identifying mRNA liberation as a further bottleneck. In summary, co-transfection offers a rapid means to identify bottlenecks in cytosolic mRNA delivery, supporting the rational design and optimization of intracellular mRNA delivery systems.

Modelling bone metastasis in spheroids to study cancer progression and screen cisplatin efficacy

Most bone metastases are caused by primary breast or prostate cancer cells settling in the bone microenvironment, affecting normal bone physiology and function and reducing 5-year survival rates to 10% and 6%, respectively. To expedite clinical availability of novel and effective bone metastases treatments, reliable and predictive in vitro models are urgently required to screen for novel therapies as current in vitro 2D planar mono-culture models do not accurately predict the clinical efficacy. We herein engineered a novel human in vitro 3D co-culture model based on spheroids to study dynamic cellular quantities of (breast or prostate) cancer cells and human bone marrow stromal cells and screen chemotherapeutic efficacy and specificity of the common anticancer drug cisplatin. Bone metastatic spheroids (BMSs) were formed rapidly within 24 h, while the morphology of breast versus prostate cancer BMS differed in terms of size and circularity upon prolonged culture periods. Prestaining cell types prior to BMS formation enabled confocal imaging and quantitative image analysis of in-spheroid cellular dynamics for up to 7 days of BMS culture. We found that cancer cells in BMS proliferated faster and were less susceptible to cisplatin treatment compared to 2D control cultures. Based on these findings and the versatility of our methodology, BMS represent a feasible 3D in vitro model for screening of new bone cancer metastases therapies.

Assembled/Disassembled Modular Scaffolds for Multicellular Tissue Engineering

The behavior of tissue resident cells can be influenced by the spatial arrangement of cellular interactions. Therefore, it is of significance to precisely control the spatial organization of various cells within multicellular constructs. It remains challenging to construct a versatile multicellular scaffold with ordered spatial organization of multiple cell types. Herein, a modular multicellular tissue engineering scaffold with ordered spatial distribution of different cell types is constructed by assembling varying cell-laden modules. Interestingly, the modular scaffolds can be disassembled into individual modules to evaluate the specific contribution of each cell type in the system. Through assembling cell-laden modules, the macrophage-mesenchymal stem cell (MSC), endothelial cell-MSC, and chondrocyte-MSC co-culture models are successfully established. The in vitro results indicate that the intercellular cross-talk can promote the proliferation and differentiation of each cell type in the system. Moreover, MSCs in the modular scaffolds may regulate the behavior of chondrocytes through the nuclear factor of activated T-Cells (NFAT) signaling pathway. Furthermore, the modular scaffolds loaded with co-cultured chondrocyte-MSC exhibit enhanced regeneration ability of osteochondral tissue, compared with other groups. Overall, this work offers a promising strategy to construct a multicellular tissue engineering scaffold for the systematic investigation of intercellular cross-talk and complex tissue engineering.

Characterization and Safety Profile of a New Combined Advanced Therapeutic Medical Product Platelet Lysate-Based Fibrin Hydrogel for Mesenchymal Stromal Cell Local Delivery in Regenerative Medicine

Adipose-derived mesenchymal stromal cells (ASC) transplant to recover the optimal tissue structure/function relationship is a promising strategy to regenerate tissue lesions. Because filling local tissue defects by injection alone is often challenging, designing adequate cell carriers with suitable characteristics is critical for in situ ASC delivery. The aim of this study was to optimize the generation phase of a platelet-lysate-based fibrin hydrogel (PLFH) as a proper carrier for in situ ASC implantation and (1) to investigate in vitro PLFH biomechanical properties, cell viability, proliferation and migration sustainability, and (2) to comprehensively assess the local in vivo PLFH/ASC safety profile (local tolerance, ASC fate, biodistribution and toxicity). We first defined the experimental conditions to enhance physicochemical properties and microscopic features of PLFH as an adequate ASC vehicle. When ASC were mixed with PLFH, in vitro assays exhibited hydrogel supporting cell migration, viability and proliferation. In vivo local subcutaneous and subgingival PLFH/ASC administration in nude mice allowed us to generate biosafety data, including biodegradability, tolerance, ASC fate and engraftment, and the absence of biodistribution and toxicity to non-target tissues. Our data strongly suggest that this novel combined ATMP for in situ administration is safe with an efficient local ASC engraftment, supporting the further development for human clinical cell therapy.

Effects of Nanofiber Scaffolds Coated with Nanoparticulate and Microparticulate Freeze Dried Bone Allograft on the Morphology, Adhesion, and Proliferation of Human Mesenchymal Stem Cells

Background:

Freeze dried bone allograft nanoparticles on a nanofiber membrane may serve as an ideal scaffold for bone regeneration. This study aimed to assess the biological behavior of human MSCs in terms of proliferation and adhesion to nanoparticulate and microparticulate FDBA scaffolds on PLLA nanofiber membrane.

Methods:

In this experimental study, PLLA nanofiber scaffolds were synthesized by the electrospinning method. The FDBA nanoparticles were synthesized mechanically. The FDBA nanoparticles and microparticles were loaded on the surface of PLLA nanofiber membrane. A total of 64 scaffold samples in four groups of n-FDBA/PLLA, FDBA/PLLA, PLLA and control were placed in 24-well polystyrene tissue culture plates; 16 wells were allocated to each group. Data were analyzed using one-way ANOVA and Bonferroni test.

Results:

The proliferation rate of MSCs was significantly higher in the nanoparticulate group compared to the microparticulate group at five days (p = 0.034). Assessment of cell morphology at 24 hours revealed spindle-shaped cells with a higher number of appendages in the nanoparticulate group compared to other groups.

Conclusion:

MSCs on n-FDBA/PLLA scaffold were morphologically more active and flatter with a higher number of cellular appendages, as compared to FDBA/PLLA. It seems that the nanoparticulate scaffold is superior to the microparticulate scaffold in terms of proliferation, attachment, and morphology of MSCs in vitro.

Biologically Relevant In Vitro 3D-Model to Study Bone Regeneration Potential of Human Adipose Stem Cells

Standard cell cultures may not predict the proliferation and differentiation potential of human mesenchymal stromal cells (MSCs) after seeding on a scaffold and implanting this construct in a bone defect. We aimed to develop a more biologically relevant in vitro 3D-model for preclinical studies on the bone regeneration potential of MSCs. Human adipose tissue-derived mesenchymal stromal cells (hASCs; five donors) were seeded on biphasic calcium phosphate (BCP) granules and cultured under hypoxia (1% O2) for 14 days with pro-inflammatory TNFα, IL4, IL6, and IL17F (10 mg/mL each) added during the first three days, simulating the early stages of repair (bone construct model). Alternatively, hASCs were cultured on plastic, under 20% O2 and without cytokines for 14 days (standard cell culture). After two days, the bone construct model decreased total DNA (3.9-fold), COL1 (9.8-fold), and RUNX2 expression (19.6-fold) and metabolic activity (4.6-fold), but increased VEGF165 expression (38.6-fold) in hASCs compared to standard cultures. After seven days, the bone construct model decreased RUNX2 expression (64-fold) and metabolic activity (2.3-fold), but increased VEGF165 (54.5-fold) and KI67 expression (5.7-fold) in hASCs compared to standard cultures. The effect of the bone construct model on hASC proliferation and metabolic activity could be largely mimicked by culturing on BCP alone (20% O2, no cytokines). The effect of the bone construct model on VEGF165 expression could be mimicked by culturing hASCs under hypoxia alone (plastic, no cytokines). In conclusion, we developed a new, biologically relevant in vitro 3D-model to study the bone regeneration potential of MSCs. Our model is likely more suitable for the screening of novel factors to enhance bone regeneration than standard cell cultures.

Platinum-loaded, selenium-doped hydroxyapatite nanoparticles selectively reduce proliferation of prostate and breast cancer cells co-cultured in the presence of stem cells

Chemotherapeutic treatment of patients with bone tumors or bone metastases often leads to severe side effects such as high drug toxicity, lack of tumor specificity and induced drug resistance. A novel strategy to treat early stages of bone metastases involves local co-delivery of multiple chemotherapeutic agents to synergistically improve the curative effect and overcome shortcomings of traditional chemotherapy. Herein we show that selenite-doped hydroxyapatite nanoparticles loaded with a hydroxyapatite-binding anti-tumor platinum complex (PtPP-HASe) selectively reduce proliferation of cancer cells without reducing proliferation of bone marrow stem cells. These PtPP-HASe particles were nanocrystalline with selenium (Se) and platinum (Pt) contents ranging between 0-10 and 1.5-3 wt%, respectively. Release kinetics of Se and Pt from PtPP-HASe nanoparticles resulted in a cumulative release of ∼10 and ∼66 wt% after 7 days, respectively. At a Pt/Se ratio of 8, released Pt and Se species selectively reduced cell number of human prostate (PC3) and human breast cancer cells (MDA-MB-231) by a factor of >10 with limited effects on co-cultured human bone marrow stem cells (hBMSc). These novel nanoparticles demonstrate high anti-cancer selectivity, which offers ample opportunities for the design of novel biomaterials with potent and selective chemotherapeutic efficacy against cancer cells.

Selenium-doped hydroxyapatite nanoparticles for potential application in bone tumor therapy

In the present study we have studied the incorporation and release of selenite ions (SeO₃^2-) in hydroxyapatite nanoparticles for the treatment of bone tumors. Two types of selenium-doped hydroxyapatite (HASe) nanoparticles (NPs) with a nominal Se/(P + Se) molar ratio ranging from 0.01 up to 0.40 have been synthesized by a new and mild wet method. The two series of samples were thoroughly characterized and resulted to be slightly different in chemical composition, but they had similar properties in terms of morphology and degree of crystallinity. Selenium release from HASe was investigated under neutral and acidic conditions to simulate both healthy tissues and the low-pH environment surrounding a tumor mass, respectively. The comparison of the release profiles at two pH values clearly showed the possibility of modulating the Se release by simply changing the amount of Se in the HASe particles. The correlation between the physicochemical properties of HASe and their dissolution as a function of pH has been also investigated to facilitate future application of the NPs as chemotherapeutic adjuvant agents. Finally, the cytotoxic activity of HASe was evaluated using prostate (PC3) and breast (MDA-MB-231) cancer cells as well as healthy human bone marrow stem cells (hBMSc). HASe NPs exerted a good cytocompatibility at low concentration of Se but, with high Se doping concentration, they displayed strong cytotoxicity.

Coculture with monocytes/macrophages modulates osteogenic differentiation of adipose-derived mesenchymal stromal cells on poly(lactic-co-glycolic) acid/polycaprolactone scaffolds

The effects of immune cells, in particular macrophages, on the behaviour of mesenchymal stromal cells (MSCs) have recently gained much attention for MSCs‐based tissue‐engineered constructs. This study aimed to evaluate the effect of monocytes/macrophages on the osteogenic differentiation of adipose‐derived mesenchymal stromal cells (ADMSCs) in three‐dimensional (3D) cocultures. For this, we cocultured THP‐1 monocytes, M1 macrophages, or M2 macrophages with ADMSCs on 3D poly(lactic‐co‐glycolic) acid (PLGA)/polycaprolactone (PCL) scaffolds using osteogenic medium for up to 42 days. We found that osteogenic differentiation of ADMSCs was inhibited by monocytes and both macrophage subtypes in 3D scaffolds. Furthermore, coculture of monocytes/macrophages with ADMSCs resulted in downregulated secretion of oncostatin M (OSM) and bone morphogenetic protein 2 (BMP‐2) and inhibited expression of osteogenic markers alkaline phosphatase (ALP), bone sialoprotein (BSP), and runt‐related transcription factor 2 (RUNX2). Compared with both macrophage subtypes, monocytes inhibited osteogenic differentiation of ADMSCs more significantly. These data suggest that the mutual interactions between monocytes/macrophages and ADMSCs negatively affect MSC osteogenic differentiation and thus possibly bone healing capacity, which highlights the importance of the micro‐environment in influencing cell‐based constructs to treat bone defects and the potential to improve their performance by resolving the inflammation ahead of treatment.

Efficacy of intraoperatively prepared cell-based constructs for bone regeneration

BACKGROUND

Conventional cell-based bone regeneration suffers from the major disadvantage of limited cell supply, time-consuming in vitro expansion cultures, and limited patient-friendliness related to cell isolation and multiple visits to the clinic. Here, we utilized an alternative concept using "easy access cells" that can be obtained in an intraoperative manner to prepare cell-based constructs.

METHODS

We used stromal vascular fraction (SVF) from human adipose tissue and human monocytes for intraoperative preparation of bone constructs. Conventional constructs grafted with expanded human adipose tissue mesenchymal stem cells (ADMSCs) derived from the same donor were set as positive controls. Additionally, we combined both cell types either or not with monocytes. The cellular interaction of human SVF and ADMSCs with human monocytes was evaluated in vitro. The feasibility and bone-regenerative capacity of intraoperative constructs were determined histologically and histomorphometrically in a rat femoral condyle bone defect model.

RESULTS

SVF displayed equal in vitro osteogenic differentiation compared to donor-matched expanded ADMSCs, which for both was significantly enhanced upon co-culture with monocytes. Moreover, SVF and ADMSCs displayed different immunoregulatory effects on monocytes/macrophages. Upon implantation in rat femoral bone defects, SVF constructs demonstrated superior bone formation compared to ADMSC constructs and cell-free controls; no effects of monocyte addition were observed.

CONCLUSION

In conclusion, we here demonstrate the feasibility of intraoperative SVF construct preparation and superior bone-regenerative capacity thereof compared to donor-matched ADMSC constructs. The superiority of SVF constructs was found to be linked to the distinct differences between immunoregulatory effects of SVF and ADMSCs.

Effect of Nano-HA/Collagen Composite Hydrogels on Osteogenic Behavior of Mesenchymal Stromal Cells

This study aimed to comparatively evaluate the in vitro effect of nanosized hydroxyapatite and collagen (nHA/COL) based composite hydrogels (with different ratios of nHA and COL) on the behavior of human mesenchymal stromal cells (MSCs), isolated from either adipose tissue (AT-MSCs) or bone marrow (BM-MSCs). We hypothesized that (i) nHA/COL composite hydrogels would promote the osteogenic differentiation of MSCs in an nHA concentration dependent manner, and that (ii) AT-MSCs would show higher osteogenic potential compared to BM-MSCs, due to their earlier observed higher proliferation and osteogenic differentiation potential in 2D in vitro cultures [1]. The obtained results indicated that AT-MSCs show indeed high proliferation, differentiation and mineralization capacities in nHA/COL constructs compared to BM-MSCs, but this effect was irrespective of nHA concentration. Based on the results of alkaline phosphatase (ALP) activity and osteocalcin (OCN) protein level, the osteogenic differentiation of BM-MSCs started in the beginning of the culture period and for AT-MSCs at the end of the culture period. At a molecular level, both cell types showed high expression of osteogenic markers (bone morphogenic protein 2 [BMP2], runt-related transcription factor 2 [RUNX2], OCN or COL1) in both an nHA concentration and time dependent manner. In conclusion, AT-MSCs demonstrated higher osteogenic potential in nHA/COL based 3D micro-environments compared to BM-MSCs, in which proliferation and osteogenic differentiation were highly promoted in a time dependent manner, irrespective of nHA amount in the constructs. The fact that AT-MSCs showed high proliferation and mineralization potential is appealing for their application in future pre-clinical research as an alternative cell source for BM-MSCs.

Effect of monocytes/macrophages on the osteogenic differentiation of adipose-derived mesenchymal stromal cells in 3D co-culture spheroids

This study aimed to investigate the distinctive roles of the monocytes and macrophages on osteogenic differentiation of adipose-derived mesenchymal stromal cells (ADMSCs) in 3D spheroid co-cultures. We hypothesized that monocytes or macrophages (subtypes pro-inflammatory M1 and pro-wound healing M2) would affect the osteogenic differentiation of ADMSCs in 3D spheroids and that cell-cell interactions between monocytes/macrophages and ADMSCs play an important role in the osteogenic differentiation process of ADMSCs. The obtained results indicated that the osteogenic differentiation of ADMSCs was inhibited by monocytes and both macrophage subtypes in 3D spheroids. Monocytes and M2 macrophages had a stronger inhibiting effect than M1 macrophages. Cell-cell interactions mediated by N-cadherin likely played a role in the inhibiting effect of monocytes/macrophages on the osteogenic differentiation of ADMSCs.

Macrophage type modulates osteogenic differentiation of adipose tissue MSCs

Since the reconstruction of large bone defects remains a challenge, knowledge about the biology of bone healing is desirable to develop novel strategies for improving the treatment of bone defects. In osteoimmunology, macrophages are the central component in the early stage of physiological response after bone injury and bone remodeling in the late stage. During this process, a switch of macrophage phenotype from pro-inflammatory (M1) to anti-inflammatory (M2) is observed. An appealing option for bone regeneration would be to exploit this regulatory role for the benefit of osteogenic differentiation of osteoprogenitor cells (e.g., mesenchymal stem cells; MSCs) and to eventually utilize this knowledge to improve the therapeutic outcome of bone regenerative treatment. In view of this, we focused on the in vitro interaction of different macrophage subtypes with adipose tissue MSCs to monitor the behavior (i.e. proliferation, differentiation and mineralization) of the latter in dedicated co-culture models. Our data show that co-culture of MSCs with M2 macrophages, but not with M1 macrophages or M0 macrophages, results in significantly increased MSC mineralization caused by soluble factors. Specifically, M2 macrophages promoted the proliferation and osteogenic differentiation of MSCs, while M0 and M1 macrophages solely stimulated the osteogenic differentiation of MSCs in the early and middle stages during co-culture. Secretion of the soluble factors oncostatin M (OSM) and bone morphogenetic protein 2 (BMP-2) by macrophages showed correlation with MSC gene expression levels for OSM-receptor and BMP-2, suggesting the involvement of both signaling pathways in the osteogenic differentiation of MSCs.

Coculture effects on the osteogenic differentiation of human mesenchymal stromal cells

Cell-based bone regeneration is generally pursued based on single cell type approaches, for which human adipose tissue-derived mesenchymal stromal cells (AT-MSCs) are frequently used, owing to their easy accessibility and relatively large yield. In view of multiple cell types involved in physiological bone regeneration, this study aimed to evaluate the osteogenic differentiation of AT-MSCs upon co-culture with endothelial cells or macrophages in a direct or indirect in vitro co-culture set-up. Our hypotheses were that 1) endothelial cells and macrophages stimulate AT-MSCs proliferation and osteogenic differentiation and that 2) these two cell types will more profoundly affect osteogenic differentiation of AT-MSCs in a direct compared to an indirect co-culture set-up, because of the possibility for both cell-cell interactions and effects of secreted soluble factors in the former. Osteogenic differentiation of AT-MSCs was stimulated by endothelial cells, particularly in direct co-cultures. Although initial numbers of AT-MSCs in co-culture with endothelial cells were 50% compared to monoculture controls, equal levels of mineralization were achieved. Macrophages showed a variable effect on AT-MSCs behavior for indirect co-cultures and a negative effect on osteogenic differentiation of AT-MSCs in direct co-cultures, the latter likely due to species differences of the cell types used. The results of this study demonstrate potential for cell combination strategies in bone regenerative therapies.

Cell Cotransplantation Strategies for Vascularized Craniofacial Bone Tissue Engineering: A Systematic Review and Meta-Analysis of Preclinical In Vivo Studies

The regenerative potential of tissue-engineered bone constructs may be enhanced by in vitro coculture and in vivo cotransplantation of vasculogenic and osteogenic (progenitor) cells. The objective of this study was to systematically review the literature to answer the focused question: In animal models, does cotransplantation of osteogenic and vasculogenic cells enhance bone regeneration in craniofacial defects, compared with solely osteogenic cell-seeded constructs? Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, electronic databases were searched for controlled animal studies reporting cotransplantation of endothelial cells (ECs) with mesenchymal stem cells (MSCs) or osteoblasts in craniofacial critical size defect (CSD) models. Twenty-two studies were included comparing outcomes of MSC/scaffold versus MSC+EC/scaffold (co)transplantation in calvarial (n = 15) or alveolar (n = 7) CSDs of small (rodents, rabbits) and large animal (minipigs, dogs) models. On average, studies presented with an unclear to high risk of bias. MSCs were derived from autologous, allogeneic, xenogeneic, or human (bone marrow, adipose tissue, periosteum) sources; in six studies, ECs were derived from MSCs by endothelial differentiation. In most studies, MSCs and ECs were cocultured in vitro (2-17 days) before implantation. Coculture enhanced MSC osteogenic differentiation and an optimal MSC:EC seeding ratio of 1:1 was identified. Alloplastic copolymer or composite scaffolds were most often used for in vivo implantation. Random effects meta-analyses were performed for histomorphometric and radiographic new bone formation (%NBF) and vessel formation in rodents' calvarial CSDs. A statistically significant benefit in favor of cotransplantation versus MSC-only transplantation for radiographic %NBF was observed in rat calvarial CSDs (weighted mean difference 7.80% [95% confidence interval: 1.39-14.21]); results for histomorphometric %NBF and vessel formation were inconclusive. Overall, heterogeneity in the meta-analyses was high (I² > 80%). In summary, craniofacial bone regeneration is enhanced by cotransplantation of vasculogenic and osteogenic cells. Although the direction of treatment outcome is in favor of cotransplantation strategies, the magnitude of treatment effect does not seem to be of relevance, unless proven otherwise in clinical studies.

Platelet lysate supports the in vitro expansion of human periodontal ligament stem cells for cytotherapeutic use

Human platelet lysate (PL) produced under optimal conditions of standardization and safety has been increasingly suggested as the future 'gold standard' supplement to replace fetal bovine serum (FBS) for the ex vivo propagation of mesenchymal stem cells for translational medicine and cell therapy applications. However, the multifaceted effects of PL on tissue-specific stem cells remain largely unexplored. In the present study, we investigated the stem cell behaviours of human periodontal ligament stem cells (PDLSCs) in media with or without PL. Our data indicate that human PL, either as an adjuvant for culture media or as a substitute for FBS, supports the proliferation and expansion of human PDLSCs derived from either 'young' or 'old' donors to the same extent as FBS, without interfering with their immunomodulatory capacities. Although PL appears to inhibit the in vitro differentiation of 'young' or 'old' PDLSCs, their decreased osteogenic potential may be restored to similar or higher levels compared with FBS-expanded cells. PL- and FBS-expanded PDLSCs exhibited a similar potential to form mineralized nodules and expressed similar levels of osteogenic genes. Our data indicate that large clinically relevant quantities of PDLSCs may be yielded by the use of human PL; however, further analysis of its precise composition and function will pave the way for determining optimized, defined culture conditions. In addition to the potential increase in patient safety, our findings highlight the need for further research to develop the potential of PL-expanded PDLSCs for clinical use. Copyright © 2016 John Wiley & Sons, Ltd.