Fabricating ideal scaffolds for bone tissue engineering is a great challenge to researchers. To better mimic the mineral component and the microstructure of natural bone, several kinds of materials were adopted in our study, namely gelatin, polycaprolactone (PCL), nanohydroxyapatite (nHA), and bone powder. Three types of scaffolds were fabricated using electrospinning; gelatin/PCL, gelatin/PCL/nHA, and gelatin/PCL/bone powder. Scaffolds were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. Then, Adipose-derived Stem Cells (ADSCs) were seeded on these scaffolds to study cell morphology, cell viability, and proliferation. Through this study, we found that nHA and bone powder can be successfully united in gelatin/PCL fibers. When compared with gelatin/PCL and gelatin/PCL/nHA, the gelatin/PCL/bone powder scaffolds could provide a better environment to increase ADSCs’ growth, adhesion, and proliferation. Thus, we think that gelatin/PCL/bone powder has good biocompatibility, and, when compared with nHA, bone powder may be more effective in bone tissue engineering due to the bioactive factors contained in it.

Background: The physical factors of the extracellular matrix have a profound influence on the differentiation behavior of mesenchymal stem cells. In this study, the effect of the biophysical microenvironment on rat bone marrow mesenchymal stem cell (BMSC) osteogenesis was studied both in vitro and in vivo. Methods: To prepare cell culture scaffolds of varying stiffness, increasing amounts of hydroxyapatite (HAp) were mixed into a polyethylene glycol/silk fibroin (PEG/SF) solution. The amount of HAp ranged from 25 to 100 mg, which provided for different ratios between HAp and the PEG/SF composite. In vitro, the effect of stiffness on the osteogenic differentiation of rat BMSCs was studied. The outcome measures, which were verified in vivo, included the protein expression of runt-related transcription factor 2 and osteocalcin, alkaline phosphatase activity, and the mRNA expression of osteogenesis-related markers. Results: Increasing amounts of HAp resulted in an increased elastic modulus of the cell culture scaffolds. The PEG/SF/HAp fabricated with HAp (50 mg) significantly increased cell adhesion and viability (p < 0.05) as well as the expression of all the osteogenesis-related markers (p < 0.05). Conclusions: We developed a novel cell culture scaffold and demonstrated that substrate stiffness influenced the osteogenic differentiation of rat BMSCs.

Adipose-derived stem cells (ASCs) that show multidifferentiation and anti-immune rejection capacities have been widely used in plastic and reconstructive surgery. Previous studies have indicated that mechanical and biophysical interactions between cells and their surrounding environment regulate essential processes, such as growth, survival, and differentiation, and the cytoskeleton system plays an important role in the mechanotransduction. However, the role of mechanical force in the determination of lineage fate is still unclear. Human ASCs (hASCs) were obtained from three different donors by liposuction. Adipogenesis and osteogenesis were determined by Oil Red O and Alizarin Red staining, respectively. The mRNA levels of the cytoskeleton system, PPARγ, and C/EBPα were determined by real-time polymerase chain reaction (RT-PCR). The level of cytoskeleton, PPARγ, and C/EBPα protein levels were measured by Western blotting. The morphology of the cytoskeleton system during adipogenesis was observed with confocal microscopy. hASCs were transfected with a SUN2-specific shRNA to knockdown sun2, and a nontargeting shRNA was used as a control. We found that disrupting the physiological balance between the cytoskeleton and the linker of the nucleoskeleton and cytoskeleton (LINC) complex (especially SUN2) could impact the adipogenesis of hASCs in vitro. Microtubule (MT) depolymerization with nocodazole (which interferes with the polymerization of MTs) increased the expression of SUN2 and PPARγ, while taxol (an inhibitor of MT disassembly) showed the opposite results. Meanwhile, hASCs with sun2 knockdown overexpressed MTs and decreased PPARγ expression, thereby inhibiting the adipogenesis. Furthermore, knockdown of sun2 changed the structure of perinuclear MTs. We demonstrated the presence of cross-talk between MT and SUN2, and this cross-talk plays a critical role in the rebalance of the mechanical environment and is involved in the regulation of PPARγ transport during adipogenic differentiation of hASCs.

Cyclin-dependent kinase 2 (CDK2) has been garnering considerable interest as a target to develop new cancer treatments and to ameliorate resistance to CDK4/6 inhibitors. However, a selective CDK2 inhibitor has yet to be clinically approved. With the desire to discover novel, potent, and selective CDK2 inhibitors, the phenylsulfonamide moiety of our previous lead compound 1 was bioisosterically replaced with pyrazole derivatives, affording a novel series of N,4-di(1H-pyrazol-4-yl)pyrimidin-2-amines that exhibited potent CDK2 inhibitory activity. Among them, 15 was the most potent CDK2 inhibitor (K_i = 0.005 µM) with a degree of selectivity over other CDKs tested. Meanwhile, this compound displayed sub-micromolar antiproliferative activity against a panel of 13 cancer cell lines (GI₅₀ = 0.127–0.560 μM). Mechanistic studies in ovarian cancer cells revealed that 15 reduced the phosphorylation of retinoblastoma at Thr821, arrested cells at the S and G2/M phases, and induced apoptosis. These results accentuate the potential of the N,4-di(1H-pyrazol-4-yl)pyrimidin-2-amine scaffold to be developed into potent and selective CDK2 inhibitors for the treatment of cancer.