Solution blow spinning of PLLA/hydroxyapatite composite scaffolds for bone tissue engineering.

Composite poly-L-lactide acid-based scaffolds with hydroxyapatite (HAp) content up to 75 wt.% were fabricated via solution blow spinning. The influence of HAp concentration on structure, wettability, mechanical properties and chemical and phase composition of the produced materials was examined. It was found that with an increase of HAp content the average fiber diameter was increased, the uniaxial strength and relative elongation were reduced, while the phase composition and surface wettability did not change. The performance of the scaffolds during implantation in the parietal bone of a rat skull for a period from 15 to 90 days was studied. The materials have shown high ability to integrate with both soft and hard tissues. It was found that scaffolds with 25 wt.% HAp content significantly enhance osteogenesis during scarification (damage) of the periosteum. Overall, the fabricated scaffolds proved to be highly efficient for replacing bone defects in long tubular bones.

Breast tumour cell subpopulations with expression of the MYC and OCT4 proteins.

The MYC and OCT4 genes are known factors associated with maintaining pluripotency and are linked with a more aggressive course, progression, and resistance to therapy in cancer. Determining the subpopulations of tumour cells expressing the Myc and Oct4 proteins will provide an opportunity to understand which tumour cell subpopulations expressing MYC and OCT4 are associated with metastasis and resistance and which subpopulations can be targeted by anti-MYC and anti-OCT4 therapy. The study included paraffin-embedded tissue from tumours from 27 patients with luminal B breast cancer obtained after neoadjuvant chemotherapy (NACT). Immunofluorescence staining was used to identify subpopulations of tumour cells expressing Myc, Oct4 and Snai2 (Opal™ 7-Color Kit (PerkinElmer, Hopkinton, MA). The following tumour cell subpopulations were identified with the Myc and Oct4 proteins and the Snai2 EMT marker: stem/progenitor tumour cells with/without Myc, Oct4 or Snai2 expression; differentiated tumour cells with/without Myc, Oct4 or Snai2 expression; and other nontumour cells (CK7-EpCAM-CD44+/-Myc+/-(Oct4, Snai2)+/-) within the inflammatory infiltrate in the tumour parenchyma and stroma. The circulating tumour cell subpopulations with Oct4 protein expression in the bloodstream were studied by flow cytometry. It was found that in patients with partial regression (PR) in response to NACT, the frequency of tumour stem cells was 3.6-fold increased (p = 0.038) in the non-EMT state (CK7+EpCam+CD44+Snai2-). In patients with metastases, there was a statistically significant 2.5-fold increase in the frequency of differentiated tumour cells with Myc expression (CK7+EpCam+CD44-Myc+) and a 2.7-fold increase in the frequency of cells with Oct4 expression (CK7+EpCam+CD44-OCT4+). In the next stage, the frequencies of subpopulations with expression of the Oct4 protein and signs of EMT among circulating tumour cells (CTCs) were determined. In patients with metastases, the frequency of tumour stem cells in the EMT state (CD326+CD44+CD24-CD325+) (p = 0.015) was more than fourfold increased, and the frequency of progenitor tumour cells with expression of the Oct4 stem protein (CD326+CD44+CD24+Oct4+) (p = 0.016) was almost sixfold higher than that in patients without metastases. Nonstem (differentiated) tumour cells with expression of the stemness proteins Myc and Oct4 were present in the breast tumour. Their content was significantly higher in residual tumours after NACT in patients who subsequently developed metastases compared with that in patients without metastases. Such cells are a new in situ marker of metastasis.