Isogenic-induced endothelial cells enhance osteogenic differentiation of mesenchymal stem cells on silk fibroin scaffold

3D Bioprintable Hypoxia-Mimicking PEG-Based Nano Bioink for Cartilage Tissue Engineering

As hypoxia plays a significant role in the formation and maintenance of cartilage tissue, aiming to develop native hypoxia-mimicking tissue engineering scaffolds is an efficient method to treat articular cartilage (AC) defects. Cobalt (Co) is documented for its hypoxic-inducing effects in vitro by stabilizing the hypoxia-inducible factor-1α (HIF-1α), a chief regulator of stem cell fate. Considering this, we developed a novel three-dimensional (3D) bioprintable hypoxia-mimicking nano bioink wherein cobalt nanowires (Co NWs) were incorporated into the poly(ethylene glycol) diacrylate (PEGDA) hydrogel system as a hypoxia-inducing agent and encapsulated with umbilical cord-derived mesenchymal stem cells (UMSCs). In the current study, we investigated the impact of Co NWs on the chondrogenic differentiation of UMSCs in the PEGDA hydrogel system. Herein, the hypoxia-mimicking nano bioink (PEGDA+Co NW) was rheologically optimized to bioprint geometrically stable cartilaginous constructs. The bioprinted 3D constructs were evaluated for their physicochemical characterization, swelling-degradation behavior, mechanical properties, cell proliferation, and the expression of chondrogenic markers by histological, immunofluorescence, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) methods. The results disclosed that, compared to the control (PEGDA) group, the hypoxia-mimicking nano bioink (PEGDA+Co NW) group outperformed in print fidelity and mechanical properties. Furthermore, live/dead staining, double-stranded DNA (dsDNA) content, and glycosaminoglycans (GAGs) content demonstrated that adding low amounts of Co NWs (<20 ppm) into PEGDA hydrogel system supported UMSC adhesion, proliferation, and differentiation. Histological and immunofluorescence staining of the PEGDA+Co NW bioprinted structures revealed the production of type 2 collagen (COL2) and sulfated GAGs, rendering it a feasible option for cartilage repair. It was further corroborated by a significant upregulation of the hypoxia-mediated chondrogenic and downregulation of the hypertrophic/osteogenic marker expression. In conclusion, the hypoxia-mimicking hydrogel system, including PEGDA and Co²⁺ ions, synergistically directs the UMSCs toward the chondrocyte lineage without using expensive growth factors and provides an alternative strategy for translational applications in the cartilage tissue engineering field.

Bioengineering strategies for 3D bioprinting of tubular construct using tissue-specific decellularized extracellular matrix

The goal of the current study is to develop an extracellular matrix bioink that could mimic the biochemical components present in natural blood vessels. Here, we have used an innovative approach to recycle the discarded varicose vein for isolation of endothelial cells and decellularization of the same sample to formulate the decellularized extracellular matrix (dECM) bioink. The shift towards dECM bioink observed as varicose vein dECM provides the tissue-specific biochemical factors that will enhance the regeneration capability. Interestingly, the encapsulated umbilical cord mesenchymal stem cells expressed the markers of vascular smooth muscle cells because of the cues present in the vein dECM. Further, in vitro immunological investigation of dECM revealed a predominant M2 polarization which could further aid in tissue remodeling. A novel approach was used to fabricate vascular construct using 3D bioprinting without secondary support. The outcomes suggest that this could be a potential approach for patient- and tissue-specific blood vessel regeneration.

Biocompatibility-on-a-chip: Characterization and evaluation of decellularized tendon extracellular matrix (tdECM) hydrogel for 3D stem cell culture in a microfluidic device

Researchers have always tried expensive in vitro tests to show the 3D usability of dECM. The use of tissue-specific hydrogels in a microfluidic device is rarely studied. In this study, we have used ECM obtained from goat digital flexor tendons by decellularization technique. The tdECM was characterized for its structural properties using Scanning Electron Microscopy (SEM). Collagen, dsDNA, GAGs, and protein contents were quantified using spectrophotometric assays. The cell viability and proliferation of human umbilical cord-derived mesenchymal stem cells (hUMSCs) encapsulated in the tdECM hydrogel inside the microfluidic device were checked using Calcein-AM/PI. The FTIR data showed prominent peaks of the amide group, indicating the presence of collagen. The SEM data showed intact fiber morphology after the decellularization process. There was a 95 % reduction in double-stranded DNA (dsDNA) content, proving the effectiveness of the decellularization technique. There was no significant difference in the collagen content of tdECM and the GAGs were also in the acceptable range compared to the native tissue. Over 90 % cell viability in hUMSCs was observed qualitatively and quantitatively in vitro and inside a microfluidic device. In conclusion, we characterized the tdECM hydrogel and demonstrated its compatibility with the microfluidic device.

Modulation of 3D Printed Calcium-Deficient Apatite Constructs with Varying Mn Concentrations for Osteochondral Regeneration via Endochondral Differentiation

Osteochondral regeneration remains a vital problem in clinical situations affecting both bone and cartilage tissues due to the low regeneration ability of cartilage tissue. Additionally, the simultaneous regeneration of bone and cartilage is difficult to attain due to their dissimilar nature. Thus, fabricating a single scaffold for both bone and cartilage regeneration remains challenging. Biomaterials are frequently employed to promote tissue restoration, but they still cannot replicate the structure of native tissue. This study aims to create a single biomaterial that could be used to regenerate both bone and cartilage. This study focuses on synthesizing calcium-deficient apatite (CDA) with the gradual addition of manganese. The phase stability and the effect of heat treatment on manganese-doped CDA were studied using X-ray diffraction (XRD) and Rietveld refinement. The obtained powders were tested for their 3-dimensional (3D) printing ability by fabricating cuboidal 3D structures. The 3D printed scaffolds were examined for external topography using field-emission scanning electron microscopy (FE-SEM) and were subjected to compression testing. In vitro biocompatibility and differentiation studies were performed to access their biocompatibility and differentiation capabilities. Reverse transcription-quantitative PCR (RT-qPCR) analysis was done to determine the gene expression of bone- and cartilage-specific markers. Mn helps in stabilizing the β-TCP phase beyond its sintering temperature without being degraded to α-TCP. Mn addition in CDA improves the compressive strength of the fabricated scaffolds while keeping them biocompatible. The concentrations of Mn in the CDA ceramic were found to influence the differentiation behavior of MSCs in the fabricated scaffolds. Mn-doped CDA is a promising candidate to be used as a substitute material for bone, cartilage, and osteochondral defects to facilitate repair and regeneration via endochondral differentiation. 3D printing can assist in the fabrication of a multifunctional single-unit scaffold with varied Mn concentrations, which might be able to generate the two tissues in situ in an osteochondral defect.

Mechanically tunable photo-cross-linkable bioinks for osteogenic differentiation of MSCs in 3D bioprinted constructs

3D bioprinting technique renders a plausible solution to tissue engineering applications, mainly bone tissue regeneration, which could provide the microenvironment with desired physical, chemical, and mechanical properties. However, the mechanical and structural stability of current natural polymers is a critical issue in the fabrication of bone tissue-engineered scaffolds. To overcome these issues, we have developed 3D bioprintable semi-synthetic polymers derived from natural (sodium alginate, A) and synthetic (polyethylene glycol, PEG) biopolymers. In order to enhance the cross-linking properties and biocompatibility, we have functionalized these polymers with acrylate and methacrylate chemical moieties. These selected combination of natural and synthetic polymers improved the mechanical strength due to the synergistic effect of covalent as well as ionic bond formation in the hydrogel system, which is evident from the tested tensile data. Further, the feasibility of 3D bioprinting of acrylate and methacrylate functionalized PEG and hydrogels have been tested for the biocompatibility of the fabricated structures with human umbilical cord mesenchymal stem cells (UMSCs). Further, these bioprinted scaffolds were investigated for osteogenic differentiation of UMSCs in two types of culture conditions: namely, i) with osteoinduction media (with OIM), ii) without osteoinduction media (w/o OIM). We have examined the osteoinductivity of scaffolds with the activity of alkaline phosphatase (ALP) content, and significant changes in the ALP activity was observed with the stiffness of developed materials. The extent osteogenic differentiation was observed by alizarin red staining and reverse transcription PCR analysis. Elevated levels of ALP, RUNX2 and COL1 gene expression has been observed in without OIM samples on week 1 and week 3. Further, our study showed that the synthesized alginate methacrylate (AMA) without osteoinduction supplement with young's modulus of 0.34 MPa has a significant difference in ALP quantity and gene expression over the other reported literature. Thus, this work plays a pivotal role in the development of 3D bioprintable and photo-cross-linkable hydrogels in osteogenic differentiation of mesenchymal stem cells.

Human Umbilical Cord-Derived Mesenchymal Stem Cells Promote Corneal Epithelial Repair In Vitro

Corneal injuries are among the leading causes of blindness and vision impairment. Trauma, infectious keratitis, thermal and chemical (acids and alkali burn) injuries may lead to irreversible corneal scarring, neovascularization, conjunctivalization, and limbal stem cell deficiency. Bilateral blindness constitutes 12% of total global blindness and corneal transplantation remains a stand-alone treatment modality for the majority of end-stage corneal diseases. However, global shortage of donor corneas, the potential risk of graft rejection, and severe side effects arising from long-term use of immunosuppressive medications, demands alternative therapeutic approaches. Umbilical cord-derived mesenchymal stem cells can be isolated in large numbers using a relatively less invasive procedure. However, their role in injury induced corneal repair is largely unexplored. Here, we isolated, cultured and characterized mesenchymal stem cells from human umbilical cord, and studied the expression of mesenchymal (CD73, CD90, CD105, and CD34), ocular surface and epithelial (PAX6, WNT7A, and CK-8/18) lineage markers through immunofluorescence. The cultured human limbal and corneal epithelial cells were used as controls. Scratch assay was used to study the corneal epithelial repair potential of umbilical cord-derived mesenchymal stem cells, in vitro. The in vitro cultured umbilical cord-derived mesenchymal stem cells were plastic adherent, showed trilineage differentiation and expressed: mesenchymal markers CD90, CD105, CD73; epithelial marker CK-8/18, and ocular lineage developmental markers PAX6 and WNT-7A. Our findings suggest that umbilical cord-derived mesenchymal stem cells promote repair of the injured corneal epithelium by stimulating the proliferation of corneal epithelial cells, in vitro. They may serve as a potential non-ocular source of stem cells for treating injury induced bilateral corneal diseases.

Indirect co-culture of lung carcinoma cells with hyperthermia-treated mesenchymal stem cells influences tumor spheroid growth in a collagen-based 3-dimensional microfluidic model

BACKGROUND

Mesenchymal stem cells (MSCs) have paradoxically been reported to exert either pro- or anti-tumor effects in vitro. Hyperthermia, in combination with chemotherapy, has tumor-inhibiting effects; however, its role, together with MSCs, so far is not well understood. Furthermore, a lot of research is conducted using conventional 2-dimensional in vitro models that do not mimic the actual tumor microenvironment.

AIM

In light of this fact, an indirect method of co-culturing human amniotic membrane-derived MSCs (AMMSCs) with collagen-encapsulated human lung carcinoma cells (A549) was performed using a 3-dimensional (3D) tumor-on-chip device.

METHODS

The conditioned medium of AMMSCs (AMMSC-CM) or heat-treated AMMSCs (heat-AMMSC-CM) was utilized to create indirect co-culture conditions. Tumor spheroid growth characterization, immunocytochemistry and cytotoxicity assays, and anti-cancer peptide (P1) screening were performed to determine the effects of the conditioned medium.

RESULTS

The A549 cells cultured inside the 3D microfluidic chip developed into multicellular tumor spheroids over five days of culture. The AMMSC-CM, contrary to previous reports claiming its tumor-inhibiting potential, led to significant proliferation of tumor spheroids. Heat-AMMSC-CM led to reductions in both spheroid diameter and cell proliferation. The medium containing the P1 peptide was found to be the least cytotoxic to tumor spheroids in co-culture compared with the monoculture and heat-co-culture groups.

CONCLUSIONS

Hyperthermia, in combination with the anticancer peptide, exhibited highest cytotoxic effects. This study highlights the growing importance of 3D microfluidic tumor models for testing stem-cell-based and other anti-cancer therapies.

Selective Cytotoxicity of a Novel Trp-Rich Peptide against Lung Tumor Spheroids Encapsulated inside a 3D Microfluidic Device

There is a globally rising healthcare need to develop new anticancer therapies as well as to test them on biologically relevant in vitro cancer models instead of overly simplistic 2D models. To address both these needs, a 3D lung cancer spheroid model is developed using human A549 cells trapped inside a collagen gel in a compartmentalized microfluidic device and homogenously sized (35-45 µm) multicellular tumor spheroids are obtained in 5 days. The novel tryptophan-rich peptide P1, identified earlier as a potential anticancer peptide (ACP), shows enhanced cytotoxic efficacy against A549 tumor spheroids (>75%) in clinically relevant low concentrations, while it does not affect human amniotic membrane mesenchymal stem cells at the same concentrations (<15%). The peptide also inhibits the formation of tumor spheroids by reducing cell viability as well as lowering the proliferative capacity, which is confirmed by the expression of cell proliferation marker Ki-67. The ACP offers a novel therapeutic strategy against lung cancer cells without affecting healthy cells. The microfluidic device used is likely to be useful in helping develop models for several other cancer types to test new anticancer agents.