Emine Kilic

A 6-month in vivo study of polymer/mesenchymal stem cell constructs for cranial defects

Two biodegradable polymers, poly(L-lactide) and poly(ε-caprolactone) were blended (50/50) and used to produce polymeric scaffolds by the dual porogen approach using a salt leaching technique to create pores within the matrix, while supercritical-CO 2 treatment was used to enhance the interconnectivity and to remove impurities from synthesis steps. The scaffolds were highly porous (porosity >90%) with interconnected pore morphologies. These biodegradable scaffolds were evaluated in Sprague Dawley rats for osteoconductive properties over a 6-month period. Bone specimens were analyzed after 1, 3, and 6 months, for bone healing and tissue response. The cortical bone remodeling by controlled osteoblastic and osteoclastic activities as well as the bone marrow elements recovery were semi-quantitatively examined for each group. Excellent integration and biocompatibility behavior was observed in all groups. No adverse tissue responses were observed.

Stem cell suspension injected HEMA-lactate-dextran cryogels for regeneration of critical sized bone defects

Abstract HEMA-Lactate-Dextran cryogel scaffolds were produced by cryogelation. Mesencyhmal stem cells (MSC) were isolated from rat bone marrow. Critical sized cranial bone defects were created in rat cranium. Stem cells were injected inside the macropores of the cryogel scaffolds prepared from HEMA-Lactate-Dextran possessing the same dimensions with the defect and placed in the cranial bone. The cryogels placed in the defect without stem cells served as control. After selected time intervals the experimental sites were removed from the animals and new bone formation and tissue integration were investigated by histological analysis. The in vivo results exhibited osseous tissue integration within the implant and mineralized functionally stable bone restoration of the cranial defects. Tissue formation started in the macrospores of the scaffold starting from periphery to the center. A significant ingrowth of connective tissue cells and new blood vessels allowed new bone formation. Histological data demonstrated that new bone per total defect area ratio, were not significantly different in “scaffold-stem cells” group compared to that of “scaffold only” group on all time points. However, the blood vessel density was significantly higher in “scaffold-stem cells” group comparing to that of the “scaffold only” group on day 30. “Scaffold-stem cells” given group gave better tissue response score when compared to “scaffold only” group on day 180.

Adipocyte differentiation defect in mesenchymal stromal cells of patients with malignant infantile osteopetrosis.

BACKGROUND Malignant infantile osteopetrosis (MIOP) is a disorder of osteoclasts characterized by defective bone resorption and death in infancy. The multipotent mesenchymal stromal cells (MSC) and their progeny (osteoblasts) are major components of the bone marrow (BM) microenvironment and are found in close contact with cells of hematopoietic origin, including osteoclasts. We hypothesized that MSC defects may be associated with osteoclast dysfunction and osteopetrosis phenotype. METHODS BM MSC, obtained from six patients with MIOP, were expanded in vitro and characterized by morphology, plastic-adherence, immunophenotype and multilineage differentiation potential. RESULTS Physical and immunophenotypic characteristics of patient MSC were similar to healthy age-matched controls. However, an isolated in vitro differentiation defect toward adipogenic lineage was demonstrated in patient MSC and confirmed by low or absent expression of adipogenic transcripts (peroxisome proliferator-activated receptor-gamma, adipophilin, stearoyl-CoA desaturase, leptin and adiponectin) upon induction of adipogenesis. Following BM transplantation, minimal improvement in adipogenic potency of MSC was demonstrated by Oil Red O staining. DISCUSSION MIOP is associated in vitro with a failure of MSC to differentiate into an adipogenic lineage, suggesting a BM microenvironment defect. The defect may contribute to osteoclast dysfunction, or may be attributed to the effect of the osteopetrotic marrow environment. Further investigations should determine the pathophysiologic importance of this novel defect, and could perhaps contribute to consideration of MSC therapy in MIOP.

Lactobacillus rhamnosus could inhibit Porphyromonas gingivalis derived CXCL8 attenuation

ABSTRACT An increasing body of evidence suggests that the use of probiotic bacteria is a promising intervention approach for the treatment of inflammatory diseases with a polymicrobial etiology. P. gingivalis has been noted to have a different way of interacting with the innate immune response of the host compared to other pathogenic bacteria, which is a recognized feature that inhibits CXCL8 expression. Objective The aim of the study was to determine if P. gingivalis infection modulates the inflammatory response of gingival stromal stem cells (G-MSSCs), including the release of CXCL8, and the expression of TLRs and if immunomodulatory L. rhamnosus ATCC9595 could prevent CXCL8 inhibition in experimental inflammation. Material and Methods G-MSSCs were pretreated with L. rhamnosus ATCC9595 and then stimulated with P. gingivalis ATCC33277. CXCL8 and IL-10 levels were investigated with ELISA and the TLR-4 and 2 were determined through flow cytometer analysis. Results CXCL8 was suppressed by P. gingivalis and L. rhamnosus ATCC9595, whereas incubation with both strains did not abolish CXCL8. L. rhamnosus ATCC9595 scaled down the expression of TLR4 and induced TLR2 expression when exposed to P. gingivalis stimulation (p<0.01). Conclusions These findings provide evidence that L. rhamnosus ATCC9595 can modulate the inflammatory signals and could introduce P. gingivalis to immune systems by inducing CXCL8 secretion.