Role of growth factors and oxygen to limit hypertrophy and impact of high magnetic nanoparticles dose during stem cell chondrogenesis

Promotion of hMDSC differentiation by combined action of scaffold material and TGF-β superfamily growth factors

Objective

Herein we propose a combined action of collagen type I (CA) or synthetic collagen-like-peptide functionalized with the cell adhesive RGD motif (PEG-CLP-RGD) hydrogels and selected growth factors to promote chondrogenic differentiation of human muscle-derived stem cells (hMDSCs) under normal and reduced oxygen conditions.

Methods

hMDSCs were set for differentiation towards chondrogenic lineage using BMP-7 and TGF-β3. Cells were seeded onto hydrogels loaded with growth factors (75ng/scaffold) and cultured for 28 days under normal (21%) and severe hypoxic (1%) conditions. Chondrogenesis was evaluated by monitoring collagen type II and GAG deposition, and quantification of ACAN expression by RT-PCR.

Results

Sustained release of TGFβ3 from the hydrogels was observed, 8.7 ± 0.5% of the initially loaded amount diffused out after 24 h from both substrates. For the BMP-7 growth factor, 14.8 ± 0.3% and 18.2 ± 0.6% of the initially loaded amount diffused out after 24 h from CA and CLP-RGD, respectively. The key findings of this study are: i) the self-supporting hydrogels themselves can stimulate hMDSC chondrogenesis by inducing gene expression of cartilage-specific proteoglycan aggrecan and ECM production; ii) the effect of dual BMP-7 and TGF-β3 loading was more pronounced on CA hydrogel under normal oxygen conditions; iii) dual loading on PEG-CLP-RGD hydrogels did not have the synergistic effect, TGF-β3 was more effective under both oxygen conditions; iv) BMP-7 can improve chondrogenic effect of TGF-β3 on CA scaffolds, and hydrogels loaded with both growth factors can induce cartilage formation in hMDSC cultures.

Conclusion

Our results support the potential strategy of combining implantable hydrogels functionalized with differentiation factors toward improving cartilaginous repair.

Rapidly Degrading Hydrogels to Support Biofabrication and 3D Bioprinting Using Cartilage Microtissues

In recent years, there has been increased interest in the use of cellular spheroids, microtissues, and organoids as biological building blocks to engineer functional tissues and organs. Such microtissues are typically formed by the self-assembly of cellular aggregates and the subsequent deposition of a tissue-specific extracellular matrix (ECM). Biofabrication and 3D bioprinting strategies using microtissues may require the development of supporting hydrogels and bioinks to spatially localize such biological building blocks in 3D space and hence enable the engineering of geometrically defined tissues. Therefore, the aim of this work was to engineer scaled-up, geometrically defined cartilage grafts by combining multiple cartilage microtissues within a rapidly degrading oxidized alginate (OA) supporting hydrogel and maintaining these constructs in dynamic culture conditions. To this end, cartilage microtissues were first independently matured for either 2 or 4 days and then combined in the presence or absence of a supporting OA hydrogel. Over 6 weeks in static culture, constructs engineered using microtissues that were matured independently for 2 days generated higher amounts of glycosaminoglycans (GAGs) compared to those matured for 4 days. Histological analysis revealed intense staining for GAGs and negative staining for calcium deposits in constructs generated by using the supporting OA hydrogel. Less physical contraction was also observed in constructs generated in the presence of the supporting gel; however, the remnants of individual microtissues were more observable, suggesting that even the presence of a rapidly degrading hydrogel may delay the fusion and/or the remodeling of the individual microtissues. Dynamic culture conditions were found to modulate ECM synthesis following the OA hydrogel encapsulation. We also assessed the feasibility of 3D bioprinting of cartilage microtissues within OA based bioinks. It was observed that the microtissues remained viable after extrusion-based bioprinting and were able to fuse after 48 h, particularly when high microtissue densities were used, ultimately generating a cartilage tissue that was rich in GAGs and negative for calcium deposits. Therefore, this work supports the use of OA as a supporting hydrogel/bioink when using microtissues as biological building blocks in diverse biofabrication and 3D bioprinting platforms.

Craniofacial chondrogenesis in organoids from human stem cell-derived neural crest cells

Knowledge of cell signaling pathways that drive human neural crest differentiation into craniofacial chondrocytes is incomplete, yet essential for using stem cells to regenerate craniomaxillofacial structures. To accelerate translational progress, we developed a differentiation protocol that generated self-organizing craniofacial cartilage organoids from human embryonic stem cell-derived neural crest stem cells. Histological staining of cartilage organoids revealed tissue architecture and staining typical of elastic cartilage. Protein and post-translational modification (PTM) mass spectrometry and snRNA-seq data showed that chondrocyte organoids expressed robust levels of cartilage extracellular matrix (ECM) components: many collagens, aggrecan, perlecan, proteoglycans, and elastic fibers. We identified two populations of chondroprogenitor cells, mesenchyme cells and nascent chondrocytes, and the growth factors involved in paracrine signaling between them. We show that ECM components secreted by chondrocytes not only create a structurally resilient matrix that defines cartilage, but also play a pivotal autocrine cell signaling role in determining chondrocyte fate.

Evaluating the Effect of Hypoxia on Human Adult Mesenchymal Stromal Cell Chondrogenesis In Vitro: A Systematic Review

Human adult mesenchymal stromal cells (MSCs) from a variety of sources may be used to repair defects in articular cartilage by inducing them into chondrogenic differentiation. The conditions in which optimal chondrogenic differentiation takes place are an area of interest in the field of tissue engineering. Chondrocytes exist in vivo in a normally hypoxic environment and thus it has been suggested that exposing MSCs to hypoxia may also contribute to a beneficial effect on their differentiation. There are two main stages in which MSCs can be exposed to hypoxia, the expansion phase when cells are cultured, and the differentiation phase when cells are induced with a chondrogenic medium. This systematic review sought to explore the effect of hypoxia at these two stages on human adult MSC chondrogenesis in vitro. A literature search was performed on PubMed, EMBASE, Medline via Ovid, and Cochrane, and 24 studies were ultimately included. The majority of these studies showed that hypoxia during the expansion phase or the differentiation phase enhances at least some markers of chondrogenic differentiation in adult MSCs. These results were not always demonstrated at the protein level and there were also conflicting reports. Studies evaluating continuous exposure to hypoxia during the expansion and differentiation phases also had mixed results. These inconsistent results can be explained by the heterogeneity of studies, including factors such as different sources of MSCs used, donor variability, level of hypoxia used in each study, time exposed to hypoxia, and differences in culture methodology.

Generation of hyaline-like cartilage tissue from human mesenchymal stromal cells within the self-generated extracellular matrix

Chondrocytic hypertrophy, a phenotype not observed in healthy hyaline cartilage, is often concomitant with the chondrogenesis of human mesenchymal stromal cells (hMSCs). This undesired feature represents one of the major obstacles in applying hMSCs for hyaline cartilage repair. Previously, we developed a method to induce hMSC chondrogenesis within self-generated extracellular matrix (mECM), which formed a cartilage tissue with a lower hypertrophy level than conventional hMSC pellets. In this study, we aimed to test the utility of hypoxia and insulin-like growth factor-1 (IGF1) on further reducing hypertrophy. MSC-mECM constructs were first subjected to chondrogenic culture in normoxic or hypoxic (5%) conditions. The results indicated that hMSC-derived cartilage formed in hypoxic culture displayed a significantly reduced hypertrophy level than normoxic culture. However, hMSC chondrogenesis was also suppressed under hypoxic culture, partially due to the reduced activity of the IGF1 pathway. IGF1 was then supplemented in the chondrogenic medium, which promoted remarkable hMSC chondrogenesis under hypoxic culture. Interestingly, the IGF1-enhanced hMSC chondrogenesis, under hypoxic culture, was not at the expense of promoting significantly increased hypertrophy. Lastly, the cartilage tissues created by hMSCs with different conditions were implanted into osteochondral defect in rats. The results indicated that the tissue formed under hypoxic condition and induced with IGF1-supplemented chondrogenic medium displayed the best reparative results with minimal hypertrophy level. Our results demonstrate a new method to generate hyaline cartilage-like tissue from hMSCs without using exogenous scaffolds, which further pave the road for the clinical application of hMSC-based cartilage tissue engineering. STATEMENT OF SIGNIFICANCE: In this study, hyaline cartilage-like tissues were generated from human mesenchymal stromal cells (hMSCs), which displayed robust capacity in repairing the osteochondral defect in rats. In particular, the extracellular matrix created by hMSCs was used, so no exogenous scaffold was needed. Through a series of optimization, we defined that hypoxic culture and supplementation of insulin-like growth factor-1 (IGF-1) in chondrogenic medium resulted in robust cartilage formation with minimal hypertrophy. We also demonstrated that hypoxic culture suppressed chondrogenesis and hypertrophy through modulating the Wnt/β-catenin and IGF1 pathways, respectively. Our results demonstrate a new method to generate hyaline cartilage-like tissue from hMSCs without using exogenous scaffolds, which will further pave the road for the clinical application of hMSCs-based cartilage tissue engineering.

Perichondrium-inspired permeable nanofibrous tube well promoting differentiation of hiPSC-derived pellet toward hyaline-like cartilage pellet

The pellet formation has been regarded as a golden standard forin vitrochondrogenic differentiation. However, a spatially inhomogeneous chondrogenic microenvironment around a pellet resulted from the use of a traditional impermeable narrow tube, such as the conical tube, undermines the differentiation performance and therapeutic potential of differentiated cartilage pellet in defective articular cartilage treatment. To address this drawback, a perichondrium-inspired permeable nanofibrous tube (PINaT) well with a nanofibrous wall permeable to gas and soluble molecules is proposed. The PINaT well was fabricated with a micro deep drawing process where a flat thin nanofibrous membrane was transformed to a 3.5 mm deep tube well with a ∼50µm thick nanofibrous wall. Similar toin vivoperichondrium, the PINaT well was found to allow oxygen and growth factor diffusion required for chondrogenic differentiation across the entire nanofibrous wall. Analyses of gene expressions (COL2A1, COL10A1, ACAN, and SOX9), proteins (type II and X collagen), and glycosaminoglycans contents were conducted to assess the differentiation performance and clinical efficacy of differentiated cartilage pellet. The regulated spatially homogeneous chondrogenic microenvironment around the human induced pluripotent stem cell-derived pellet (3 × 10⁵cells per pellet) in the PINaT well remarkably improved the quality of the differentiated pellet toward a more hyaline-like cartilage pellet. Furthermore, an accelerated chondrogenic differentiation process of the pellet produced by the PINaT well was achieved for 14 days, demonstrating a hyaline cartilage-specific marker similar to the control pellet differentiated for 20 days. Finally, the enhanced clinical efficacy of the hyaline-like cartilage pellet was confirmed using an osteochondral defect rat model, with the repaired tissue resembling hyaline cartilage rather than fibrous cartilage after 8 weeks of regeneration.

Magnetic nanoparticle loaded human adipose derived mesenchymal cells spheroids in levitated culture

Magnetic nanoparticles (MNP) are intensely scrutinized for biomedical applications due to their excellent biocompatibility and adjustable magnetic field (MF) responsiveness. Three-dimensional spheroid culture of ADSC improves stem cell proliferation and differentiation, increasing their potential for clinical applications. In this study we aimed to detect if MF levitated culture of ADSC loaded with proprietary MNP maintain the properties of ADSC and improve their performances. Levitated ADSC-MNP formed aggregates with increased volume and reduced number compared to nonlevitated ones. ADSC-MNP from levitated spheroid displayed higher viability, proliferation and mobility compared to nonlevitated and 2D culture. Levitated and nonlevitated ADSC-MNP spheroids underwent three lineage differentiation, demonstrating preserved ADSC stemness. Quantitative osteogenesis showed similar values in MNP-loaded levitated and nonlevitated spheroids. Significant increases in adipogenic conversion was observed for all 3D formulation. Chondrogenic conversion in levitated and nonlevitated spheroids produced comparable ratio glucosaminoglycan (GAG)/DNA. Increased chondrogenesis could be observed for ADSC-MNP in both levitated and nonlevitated condition. Taken together, ADSC-MNP levitated spheroids retain stemness and display superior cell viability and migratory capabilities. Furthermore, the method consistently increases spheroid maneuverability, potentially facilitating large scale manufacturing and automation. Levitated spheroid culture of ADSC-MNP can be further tested for various application in regenerative medicine and organ modeling.

Ever-Evolving Identity of Magnetic Nanoparticles within Human Cells: The Interplay of Endosomal Confinement, Degradation, Storage, and Neocrystallization

Considerable knowledge has been acquired in inorganic nanoparticles' synthesis and nanoparticles' potential use in biomedical applications. Among different materials, iron oxide nanoparticles remain unrivaled for several reasons. Not only do they respond to multiple physical stimuli (e.g., magnetism, light) and exert multifunctional therapeutic and diagnostic actions but also they are biocompatible and integrate endogenous iron-related metabolic pathways. With the aim to optimize the use of (magnetic) iron oxide nanoparticles in biomedicine, different biophysical phenomena have been recently identified and studied. Among them, the concept of a "nanoparticle's identity" is of particular importance. Nanoparticles' identities evolve in distinct biological environments and over different periods of time. In this Account, we focus on the remodeling of magnetic nanoparticles' identities following their journey inside cells. For instance, nanoparticles' functions, such as heat generation or magnetic resonance imaging, can be highly impacted by endosomal confinement. Structural degradation of nanoparticles was also evidenced and quantified in cellulo and correlates with the loss of magnetic nanoparticle properties. Remarkably, in human stem cells, the nonmagnetic products of nanoparticles' degradation could be subsequently reassembled into neosynthesized, endogenous magnetic nanoparticles. This stunning occurrence might account for the natural presence of magnetic particles in human organs, especially the brain. However, mechanistic details and the implication of such phenomena in homeostasis and disease have yet to be completely unraveled.This Account aims to assess the short- and long-term transformations of magnetic iron oxide nanoparticles in living cells, particularly focusing on human stem cells. Precisely, we herein overview the multiple and ever-evolving chemical, physical, and biological magnetic nanoparticles' identities and emphasize the remarkable intracellular fate of these nanoparticles.

Dose-Dependent Effects of Platelet-Rich Plasma Powder on Chondrocytes In Vitro

BACKGROUND

Platelet-rich plasma (PRP) is widely used in sports medicine. However, neither preparation nor parameters for clinical application, such as concentration, timing, and number of applications, are standardized, making research and clinical utilization challenging.

PURPOSE

To investigate the effect of varying doses of PRP powder in terms of different concentrations, timing, and number of applications on human chondrocytes in a reproducible cell culture model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A standardized lyophilized platelet growth factor preparation (PRP powder) was used to stimulate human chondrocytes. Chondrocytes were cultivated for 2 weeks with different stimulation frequencies (2×, 3×, 6×) and different concentrations of PRP powders (0.5%, 1%, 5%). Cell proliferation and metabolic cell activity were analyzed on days 7 and 14. Phenotypic changes were visualized through live-dead staining. Chondrogenic differentiation was quantified with enzyme-linked immunosorbent assay to assess the synthesis of procollagen types 1 and 2. Furthermore, sulfated proteoglycans and glycosaminoglycans were analyzed.

RESULTS

Human chondrocytes exhibited a significant dose- and time-dependent increase after 14 days in cell number (1% and 5% PRP powder vs unstimulated control: 7.95- and 15.45-fold increase, respectively; 2× vs 6× stimulation with 5% PRP powder: 4.00-fold increase) and metabolic cell activity (1% and 5% PRP powder vs unstimulated control: 3.27-fold and 3.58-fold change, respectively). Furthermore, cells revealed a significant increase in the amount of bone-specific procollagen type 1 (14 days, 1.94-fold) and sulfated glycosaminoglycans (14 days, 2.69-fold); however, no significant change was observed in the amount of cartilage-specific collagen type 2.

CONCLUSION

We showed that chondrocytes exhibit a significant dose- and time-dependent increase in cell number and metabolic cell activity. The standardized use of growth factor concentrates in cell culture models can contribute to clinical knowledge in terms of dosage and timing of PRP applications.

CLINICAL RELEVANCE

Problems with PRP, such as the absence of standardization, lack of consistency among studies, and unknown dosage, could be solved by using characterized PRP powder made by pooling and lyophilizing multiple platelet concentrates. The innovative PRP powder generates new possibilities for PRP research, as well as for the treatment of patients.

Mesenchymal stem cells for cartilage regeneration in dogs

Articular cartilage damage and osteoarthritis (OA) are common orthopedic diseases in both humans and dogs. Once damaged, the articular cartilage seldom undergoes spontaneous repair because of its avascular, aneural, and alymphatic state, and the damage progresses to a chronic and painful situation. Dogs have distinctive characteristics compared to other laboratory animal species in that they share an OA pathology with humans. Dogs can also require treatment for naturally developed OA; therefore, effective treatment methods for OA are desired in veterinary medicine as well as in human medicine. Recently, interest has grown in regenerative medicine that includes the use of mesenchymal stem cells (MSCs). In cartilage repair, MSCs are a promising therapeutic tool due to their self-renewal capacity, ability to differentiate into cartilage, potential for trophic factor production, and capacity for immunomodulation. The MSCs from dogs (canine MSCs; cMSCs) share various characteristics with MSCs from other animal species, but they show some deviations, particularly in their differentiation ability and surface epitope expression. In vivo studies of cMSCs have demonstrated that intraarticular cMSC injection into cartilage lesions results in excellent hyaline cartilage regeneration. In clinical situations, cMSCs have shown great therapeutic effects, including amelioration of pain and lameness in dogs suffering from OA. However, some issues remain, such as a lack of regulations or guidelines and a need for unified methods for the use of cMSCs. This review summarizes what is known about cMSCs, including their in vitro characteristics, their therapeutic effects in cartilage lesion treatment in preclinical in vivo studies, their clinical efficacy for treatment of naturally developed OA in dogs, and the current limitations of cMSC studies.