Abstract:We developed collagen (COL) and collagen/beta tricalcium phosphate (COL/b-TCP) scaffolds with a b-TCP/collagen weight ratio of 4 by freeze-drying. Mouse bone marrowderived mesenchymal stem cells (BMMSCs) were cultured on these scaffolds for 14 days. Samples were characterized by physicochemical analyses and their biological properties such as cell viability and alkaline phosphatase (ALP) activity was, also, examined. Additionally, the vascularization potential of the prepared scaffolds was tested subcutaneously in Wistar rats. We observed a microporous structure with large porosity (95-98%) and appropriate pore size (120-200 mm). The COL/b-TCP scaffolds had a much higher compressive modulus (970 6 1.20 KPa) than pure COL (0.8 6 1.82 KPa). In vitro model of apatite formation was established by immersing the composite scaffold in simulated body fluid for 7 days. An ALP assay revealed that porous COL/b-TCP can effectively activate the differentiation of BMMSCs into osteoblasts. The composite scaffolds also promoted vascularization with good integration with the surrounding tissue. Thus, introduction of b-TCP powder into the porous collagen matrix effectively improved the mechanical and biological properties of the collagen scaffolds, making them potential bone substitutes for enhanced bone regeneration in orthopedic and dental applications.

Bioactive glasses (BGs) have attracted added attention in the structure of the scaffolds for bone repair applications. Different metal ions could be doped in BGs to induce specific biological responses. Among these ions, strontium (Sr) is considered as an effective and safe doping element with promising effects on bone formation and regeneration. In this experiment, we evaluated the antibacterial activities of the gelatin-BG (Gel-BG) and Gel-BG/Sr scaffolds in vitro. The osteogenic properties of the prepared scaffolds were also assessed in rabbit calvarial bone defects for 12 weeks. Both scaffolds showed in vivo bone formation during 12 weeks with the newly formed bone area in Gel-BG/Sr scaffold was higher than that in Gel-BG scaffolds after the whole period. Based on the histological results, Gel-BG/Sr exhibited acceleration of early-stage bone formation in vivo. The results of antibacterial investigation for both scaffolds showed complete growth inhibition against Escherichia coli (E. coli). Although Gel-BG revealed no antibacterial effect on Staphylococcus aureus (S. aureus), the Gel-BG/Sr was able to partially inhibit the growth of S. aureus, as detected by threefold reduction in growth index. Our results confirmed that Sr doped BG is a favorable candidate for bone tissue engineering with superior antibacterial activity and bone regeneration capacity compared with similar counterparts having no Sr ion.

Bone defects remain a significant health issue and a major cause of morbidity in elderly patients. Composites based on collagen/calcium phosphate have been widely used for bone repair in clinical applications, owing to their comparability to bone extracellular matrix. This study aimed to evaluate the effects of a scaffold of collagen/calcium phosphate (COL/β-TCP) on bone formation to assess its potential use as a bone substitute to repair bone defects. Bilateral full-thickness critically sized calvarial defects (8 mm in diameter) were created in New Zealand white rabbits and treated with COL/β-TCP or COL scaffolds. One defect was also left unfilled as a control. Bone regeneration was assessed through histological evaluation using hematoxylin and eosin and Masson's trichrome staining after 4 and 8 weeks. Alizarin Red staining was also utilized to observe the mineralization process. Our findings indicated that COL/β-TCP implantation could better enhance bone regeneration than COL and exhibited both new bone growth and scaffold material degradation.

No abstract

Spermatogenesis is a process in which animals generate spermatozoa from spermatogonial stem cells (SSCs). Successful in vitro differentiation of SSCs towards spermatids holds a significant promise for regeneration of impaired spermatogenesis. The present study aims to evaluate the efficiency of a 3D culture containing naringenin on proliferation and differentiation potentials of mouse SSCs. In this study, multiwalled carbon nanotubes (MWCNTs) were incorporated into poly(L-lactic acid) (PLLA) fibers via electrospinning technique. The fibrous PLLA/MWCNTs were studied by Fourier-transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), water contact angle measurements, electrical conductivity, and mechanical properties. Next, the SSCs were seeded into the PLLA/MWCNTs scaffolds and exhibited preferable survival and differentiation efficiency to subsequent cell lines. To shed more light on this matter, the immunocytochemistry, reverse-transcription polymerase chain reaction (RT-PCR), and qRT-PCR results showed that the aforementioned cells on the 3D fabrics overexpressed the C-kit and SYCP3 proteins. In addition, the reactive oxygen species (ROS) measurement data demonstrated that naringenin, an effective antioxidant, plays an important role in in vitro spermatogenesis. Taken together, the results of this study revealed the synergistic effects of 3D scaffolds and naringenin for efficient spermatogenesis in laboratories. KEYWORDS antioxidants, in vitro spermatogenesis, naringenin, PLLA/MWCNTs scaffolds, spermatogonial stem cells (SSCs) Abbreviations: bp, base pairs; C-Kit, proto-oncogene c-Kit or tyrosine-protein kinase Kit; DMEM, Dulbecco's modified eagle medium; DMF, N, N-dimethyl formamide; ECM, natural extra cellular matrix; FTIR, Fourier transform-infrared spectroscopy; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; ICSI, intra-cytoplasmic sperm injection; Id4, inhibitor of differentiation 4; IVM, in vitro oocyte maturation; m-TESE, testicular sperm extraction; PLLA/MWCNTs, poly (L-lactic acid)/multi-walled carbon nanotube; PLZF, promyelocytic leukemia zinc finger; ROS, reactive oxygen species; ROSI, round spermatid injection; RT-PCR, reverse-transcription polymerase chain reaction; SEM, scanning electron microscopy; SSCs, spermatogonial stem cells; SYCP3, synaptonemal complex protein 3