Bone defect healing is induced by collagen sponge/polyglycolic acid.

We have evaluated the capability of a collagen/poly glycolic acid (PGA) scaffold in regeneration of a calvarial bone defects in rabbits. 4 bone critical size defects (CSD) were created in the calvarial bone of each rabbit. The following 4 treatment modalities were tested (1) a collagen/PGA scaffold (0.52% w/w); (2) the collagen/PGA scaffold (0.52% w/w) seeded with adipose-derived mesenchymal stem cells (AD-MSCs, 1 × 106 cells per each defect); (3) AD-MSCs (1 × 106 cells) no scaffold material, and (4) blank control. The rabbits were then divided into 3 random groups (of 5) and the treatment outcomes were evaluated at 4, 8 and 12 weeks. New bone formation was histologically assessed. Experimental groups were analyzed by CT scan and real-time PCR. Histological analysis of bone defects treated with collagen/PGA alone exhibited significant fibrous connective tissue formation at the 12 weeks of treatments (P ≤ 0.05). There was no significant difference between collagen/PGA alone and collagen/PGA + AD-MSCs groups. The results were confirmed by CT scan data showing healing percentages of 34.20% for the collage/PGA group alone as compared to the control group and no difference with collagen/PGA containing AD-MSCs (1 × 106 cells). RT-PCR analysis also indicated no significant differences between collagen/PGA and collagen/PGA + AD-MSC groups, although both scaffold containing groups significantly express ALP and SIO rather than groups without scaffolds. Although there was no significant difference between the scaffolds containing cells with non-cellular scaffolds, our results indicated that the Collagen/PGA scaffold itself had a significant effect on wound healing as compared to the control group. Therefore, the collagen/PGA scaffold seems to be a promising candidate for research in bone regeneration.

Injectable hydrogel delivery plus preconditioning of mesenchymal stem cells: exploitation of SDF-1/CXCR4 axis toward enhancing the efficacy of stem cells' homing.

Clinical applications of mesenchymal stem cells (MSCs) rely on their capacity to home and engraft in the appropriate target injury tissues for the long term. However, their homing efficiency has been observed to be very poor because of the lack or modifications of homing factors SDF-1α and CXCR4 receptors. Hence, this study was designed to investigate the homing and retention of pretreated human adipose tissue-derived MSCs (hASCs) from three different delivery routes in response to SDF-1α, released from chitosan-based injectable hydrogels. After stimulation of ASCs with a hypoxia mimicking agent, the expression level and functionality of CXCR4 were analyzed by flowcytometric analysis (FACS), transwell migration assay and qPCR. Then, the homing/retention of pretreated DiI-labeled hASCs were compared through three different in vivo delivery routes, 2 weeks after transplantation in Wistar rats. The cells were tracked histologically by fluorescent microscope and by PCR for human-specific CXCR4 gene. Results showed CXCR4 has dynamic expression pattern and pretreatment of hASCs significantly up-regulates CXCR4, leading to an increase in migration capacity toward 100 ng/mL SDF-1α in vitro and homing into the subcutaneously implanted hydrogel releasing SDF-1α in vivo. Furthermore, it seems that SDF-1α is particularly important in the retention of ASCs, in addition to its chemoattraction role. In summary, the delivery route in which the ASCs were mixed with the hydrogel rather than systemic delivery and local injection and preconditioning undertaken to increase CXCR4 expression concomitant with SDF-1α delivery by the injectable hydrogel, allowed for further homing/retention of ASCs. This might be a promising way to get better therapeutic outcomes in stem cell therapy.

Decellularized human amniotic membrane reinforced by MoS2-Polycaprolactone nanofibers, a novel conductive scaffold for cardiac tissue engineering.

In order to regenerate myocardial tissues with functional characteristics, we need to copy some properties of the myocardium, such as its extracellular matrix and electrical conductivity. In this study, we synthesized nanosheets of Molybdenum disulfide (MoS2), and integrated them into polycaprolactone (PCL) and electrospun on the surface of decellularized human amniotic membrane (DHAM) with the purpose of improving the scaffolds mechanical properties and electrical conductivity. For in vitro studies, we seeded the mouse embryonic cardiac cells, mouse Embryonic Cardiac Cells (mECCs), on the scaffolds and then studied the MoS2 nanocomposites by scanning electron microscopy and Raman spectroscopy. In addition, we characterized the DHAM/PCL and DHAM/PCL-MoS2 by SEM, transmission electron microscopy, water contact angle measurement, electrical conductivity, and tensile test. Besides, we confirmed the scaffolds are biocompatible by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, MTT assay. Furthermore, by means of SEM images, it was shown that mECCs attached to the DHAM/PCL-MoS2 scaffold have more cell aggregations and elongated morphology. Furthermore, through the Real-Time PCR and immunostaining studies, we found out cardiac genes were maturated and upregulated, and they also included GATA-4, c-TnT, NKX 2.5, and alpha-myosin heavy chain in cells cultured on DHAM/PCL-MoS2 scaffold in comparison to DHAM/PCL and DHAM. Therefore, in terms of cardiac tissue engineering, DHAM nanofibrous scaffolds reinforced by PCL-MoS2 can be suggested as a proper candidate.

Cartilage tissue engineering by co-transplantation of chondrocyte extracellular vesicles and mesenchymal stem cells, entrapped in chitosan-hyaluronic acid hydrogel.

Mesenchymal stem cells (MSCs) on injectable hydrogels are mostly used to regenerate articular cartilage, which would have a variety of outcomes. Chondrocyte extracellular vesicles (EVs) have attracted many attentions for their chondrogenic differentiation capacity; however, the roles of EVs in both chondrogenic differentiation of MSCs and cartilage regeneration are poorly understood yet. In the current study, to investigate the differentiation effects of human articular chondrocyte EVs on adipose-derived MSCs, they were cultured in injectable chitosan-hyaluronic acid (CS-HA) hydrogel and then treated with chondrocyte EVs for 21 days. The continuous treatment of EVs performed on MSCs increased chondrogenic genes' expressions ofSOX9andCOL2A1and induced expression of Col II protein. In addition, glycosaminoglycans secretion was detected in the EV-treated MSCs after about 14 days. The therapeutic efficiency of this hydrogel and EVs was studied in a rabbit osteochondral defect model. MRI results revealed that the cartilage regeneration capacity of EV-treated MSCs with CS-HA hydrogel was greater than the untreated MSCs or the EV-treated MSCs without hydrogel. Moreover, histological results showed hyaline-like cartilage in the CS-HA/MSC and CS-HA/EV/MSC groups in the cartilage defect sites. These findings suggested that the chondrocyte-EVs and CS-HA hydrogel could provide the preferable niche for chondrogenic differentiation of MSCs and cartilage regeneration in osteoarthritis cartilage injuries.

Microfluidic-Based Droplets for Advanced Regenerative Medicine: Current Challenges and Future Trends.

Microfluidics is a promising approach for the facile and large-scale fabrication of monodispersed droplets for various applications in biomedicine. This technology has demonstrated great potential to address the limitations of regenerative medicine. Microfluidics provides safe, accurate, reliable, and cost-effective methods for encapsulating different stem cells, gametes, biomaterials, biomolecules, reagents, genes, and nanoparticles inside picoliter-sized droplets or droplet-derived microgels for different applications. Moreover, microenvironments made using such droplets can mimic niches of stem cells for cell therapy purposes, simulate native extracellular matrix (ECM) for tissue engineering applications, and remove challenges in cell encapsulation and three-dimensional (3D) culture methods. The fabrication of droplets using microfluidics also provides controllable microenvironments for manipulating gametes, fertilization, and embryo cultures for reproductive medicine. This review focuses on the relevant studies, and the latest progress in applying droplets in stem cell therapy, tissue engineering, reproductive biology, and gene therapy are separately evaluated. In the end, we discuss the challenges ahead in the field of microfluidics-based droplets for advanced regenerative medicine.

PGA-incorporated collagen: Toward a biodegradable composite scaffold for bone-tissue engineering.

Nowadays composite scaffolds based on synthetic and natural biomaterials have got attention to increase healing of non-union bone fractures. To this end, different aspects of collagen sponge incorporated with poly(glycolic acid) (PGA) fiber were investigated in this study. Collagen solution (6.33 mg/mL) with PGA fibers (collagen/fiber ratio [w/w]: 4.22, 2.11, 1.06, 0.52) was freeze-dried, followed by dehydrothermal cross-linking to obtain collagen sponge incorporating PGA fibers. Properties of scaffold for cell viability, proliferation, and differentiation of mesenchymal stem cells (MSCs) were evaluated. Scanning electron microscopy showed that collagen sponge exhibited an interconnected pore structure with an average pore size of 190 µm, irrespective of PGA fiber incorporation. The collagen-PGA sponge was superior to the original collagen sponge in terms of the initial attachment, proliferation rate, and osteogenic differentiation of the bone marrow-MSCs (BM-MSC). The shrinkage of sponges during cell culture was significantly suppressed by fiber incorporation. Incorporation of PGA fiber is a simple and promising way to reinforce collagen sponge without impairing biocompatibility. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2020-2028, 2016.