No abstract

The cellular response to hypoxia is vital for skeletal tissue development and regeneration. Numerous processes, including progenitor cell recruitment, proliferation and differentiation, are activated through the hypoxia pathway in a low oxygen pressure environment. Novel materials-based strategies designed to activate the hypoxia pathway are therefore of great interest for orthopaedic tissue engineering.Here resorbable bioactive glasses (BG) were designed to activate the hypoxia pathway by substitution of Co 2+ for Ca 2+ in the BG and substitution of Co 2+ and Ca 2+ /+2Na + for Si 4+ . This allowed for the controlled release of cobalt, whilst controlling BG bioactivity (apatite-forming ability). Two series of soda-lime-phosphosilicate glasses were manufactured with increasing concentrations of cobalt. Compositions were calculated to maintain constant network connectivity (2.13) by considering cobalt as an intermediate oxide in the first series, and as a network modifier in the second series. Mg 2+ and Zn 2+ were added to one of the Co 2+ -containing glasses to inhibit HCA formation since delay or inhibition of HCA formation is essential for the use of BG in soft tissues, as is the case of cartilage.Cobalt was present in both the silicate and phosphate phases of the BG. In addition, evidence was found for it playing a dual role in the silicate phase, acting as both an intermediate oxide and taking part in the network as well as being a network modifying oxide. Consistent with an intermediate oxide role, the presence of cobalt in the BG was shown to decrease ion release. HCA formation was delayed with cobalt additions. Mg 2+ and Zn 2+ further delayed HCA formation.Cobalt release was found to be proportional to cobalt content of the BGs enabling the controlled delivery of cobalt in therapeutic active doses.

Esta es la versión de autor del artículo publicado en: This is an author produced version of a paper published in: Gut 64.12 (2015Gut 64.12 ( ): 1921Gut 64.12 ( -1935 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Results:We found that hCAP-18/LL-37 was strongly expressed in the stroma of advanced primary and secondary PDAC tumours and is secreted by immune cells of the stroma (eg, tumour-associated macrophages) in response to TGF-β1 and particularly CSC-secreted Nodal/ActivinA. Treatment of pancreatic CSC with recombinant LL-37 increased pluripotency-associated gene expression, self-renewal, invasion, and tumourigenicity via formyl peptide receptor 2 (FPR2)-and P2X purinoceptor 7 receptor (P2X7R)-dependent mechanisms, which could be reversed by inhibiting these receptors. Importantly, in a genetically engineered mouse model of K-Ras-driven pancreatic tumourigenesis, we also showed that tumour formation was inhibited by either reconstituting these mice with bone marrow from CRAMP (i.e murine homolog of hCAP-18/LL-37) knockout mice or by pharmacologically inhibiting FPR2 and P2X7R. Conclusion:Thus, hCAP-18/LL-37 represents a previously unrecognized PDAC micro-environment factor that plays a critical role in pancreatic CSC-mediated tumourigenesis. SIGNIFICANCE OF THE STUDYWhat is already known on this subject?• Pancreatic ductal adenocarcinoma (PDAC) is the most lethal cancer with limited therapeutic options.• Pancreatic cancer stem cells (CSCs) are exclusively tumourigenic and highly resistant to chemotherapy.• Tumour-associated macrophages are important for the progression and metastatic spread of many solid tumours. What are the new findings?• The immuno-modulatory cationic antimicrobial peptide 18/leucine leucine-37 (hCAP-18/LL-37) is over expressed in the stroma of PDAC and acts on CSCs to potentiate their inherent biological properties.• Tumour-associated macrophages secrete hCAP-18/LL-37 in direct response to CSC-secreted NODAL/ACTIVINA/TGF-β1.• Small molecule targeting of the LL-37 receptors formyl peptide receptor 2 (FPR2) and P2X purinoceptor 7 receptor (P2X7R), present on pancreatic CSCs, negatively impacts tumour growth and circulating tumour cell numbers. How might it impact on clinical practice in the foreseeable future?• The discovery of the crucial role of hCAP-18/LL-37 in cancer stem cell biology represents an important advancement in our understanding of the PDAC tumour microenvironment.• Targeting pancreatic CSCs using inhibitors of the LL-37 receptors FPR2 and P2X7R may represent a specific therapeutic approach to block the tumour promoting cross-talk that exists within the tumour microenviro...

Oxygen tension is a known regulator of mesenchymal stem cell (MSC) plasticity, differentiation, proliferation, and recruitment to sites of injury. Materials capable of affecting the MSC oxygen-sensing pathway, independently of the environmental oxygen pressure, are therefore of immense interest to the tissue engineering (TE) and regenerative medicine community. In this study, we describe the evaluation of the effect of hypoxia inducible factor (HIF)-stabilizing bioactive glasses (BGs) on human MSCs. The dissolution products from these hypoxia-mimicking BGs stabilized HIF-1α in a concentration-dependent manner, altered cell proliferation and metabolism, and upregulated a number of genes involved in the hypoxic response (HIF1A, HIF2A, and VHL), MSC survival (SAG and BCL2), extracellular matrix remodeling (MMP1), and angiogenesis (VEGF and PDGF). These HIF-stabilizing materials can therefore be used to improve MSC survival and enhance regeneration in a number of TE strategies.