Biomineral/Agarose Composite Gels Enhance Proliferation of Mesenchymal Stem Cells with Osteogenic Capability.

Hydroxyapatite (HA) or calcium carbonate (CaCO3) formed on an organic polymer of agarose gel is a biomaterial that can be used for bone tissue regeneration. However, in critical bone defects, the regeneration capability of these materials is limited. Mesenchymal stem cells (MSCs) are multipotent cells that can differentiate into bone forming osteoblasts. In this study, we loaded MSCs on HA- or CaCO3-formed agarose gel and cultured them with dexamethasone, which triggers the osteogenic differentiation of MSCs. High alkaline phosphatase activity was detected on both the HA- and CaCO3-formed agarose gels; however, basal activity was only detected on bare agarose gel. Bone-specific osteocalcin content was detected on CaCO3-formed agarose gel on Day 14 of culture, and levels subsequently increased over time. Similar osteocalcin content was detected on HA-formed agarose on Day 21 and levels increased on Day 28. In contrast, only small amounts of osteocalcin were found on bare agarose gel. Consequently, osteogenic capability of MSCs was enhanced on CaCO3-formed agarose at an early stage, and both HA- and CaCO3-formed agarose gels well supported the capability at a later stage. Therefore, MSCs loaded on either HA- or CaCO3-formed agarose could potentially be employed for the repair of critical bone defects.

[The effect of routine professional oral care on oral mucositis in hematologic chemotherapy patients].

BACKGROUND: According to the literature, 40%of all oral complications associated with chemotherapy are due to oral mucositis. Moreover, such complications increase the difficulties associated with oral intake, leading to deterioration of the patient's nutritional condition and increasing the risk of systemic infection. Therefore, oral mucositis prevention and proper treatment are very important. PATIENTS AND METHODS: The conditions of intra-oral cavities and effects of oral care in patients with hematological malignancies were retrospectively evaluated by dental hygienists from April 2008 to March 2011. RESULTS: Eleven of 28 patients(39.3%)who received routine professional oral care developed oral mucositis. In many such patients, intra-oral cavity deterioration, evidenced by a coated tongue and Candida infection, was observed. Although 25 of 28 patients with hematologic malignancies received specific oral mucositis care after chemotherapy initiation, those receiving continuous oral care subsequently made a full recovery. CONCLUSIONS: These results suggest that early and continuous professional oral health care may play an important role in the effective chemotherapy of patients with hematologic malignancies.

Mesenchymal stromal cells improve the osteogenic capabilities of mineralized agarose gels in a rat full-thickness cranial defect model.

The authors previously created HAp or CaCO(3) formed on or in agarose gels (HAp and CaCO(3) gels, respectively) as biocompatible and biodegradable bone graft materials. However, these gels have limitations for bone regeneration. Mesenchymal stromal cells (MSCs) have osteogenic potential and are considered useful for bone tissue engineering. The purpose of this study was to clarify the osteogenic abilities of MSCs loaded in HAp or CaCO(3) gels (MSC/HAp and MSC/CaCO(3) gels, respectively) using a rat cranial defect model compared to HAp and CaCO(3) gels alone. HAp, CaCO(3) , MSC/Hap, and MSC/CaCO(3) gels were prepared for in vivo analyses and implanted into full-thickness bone defects created in the rat cranium. All samples were assessed radiologically and histologically at 4 and 8 weeks after implantation. Using microfocus-computed tomography, an increase in bone formation was observed in the MSC-loaded gels compared to the gels alone. In addition, peripheral quantitative computed tomography revealed higher bone mineral contents in the MSC-loaded gels compared to the gels alone. After transmission X-ray diffraction analyses, the degree of apatite c-axis orientation as a bone quality index of newly formed bone in the MSC-loaded gels was close to that of living cranial bone. Histologically, more extensive bone formation was detected in the MSC-loaded gels compared to gels alone. Overall, MSC/HAp and MSC/CaCO(3) gels showed equivalent efficacy for bone regeneration. These findings demonstrate that loading of MSCs into the gels strengthened their osteogenic ability and improved the quality of the newly formed bone. As a result, MSC-loaded gels could represent viable therapeutic biomaterials for bone tissue engineering.

Regenerative behavior of biomineral/agarose composite gels as bone grafting materials in rat cranial defects.

The main objective of this study was to evaluate the biological behavior of Hydroxyapatite (HAp)/agarose and calcium carbonate (CaCO3)/agarose composite gels by an alternate soaking process used for the treatment of surgically produced bone defects in rat cranium. We designed the following four groups: (i) HAp (HAp/agarose composite gel), (ii) CaCO3 (CaCO3/agarose composite gel), (iii) Agarose (bare agarose gel), and (iv) Defect (no filling materials). We subdivided (i) (ii) (iii) into two application types as a (I) Homogenized Group (homogenized materials) and a (II) Disk Group (disk shaped materials). We assessed samples by radiological and histological analyses 0, 4, and 8 weeks after implantation. The results indicated that the composite gels showed higher radiopacity in microfocus-computed tomography (muCT) images and showed higher volume in quantitative analyses using Dual Energy X-ray Absorptiometry (DEXA) and Peripheral Quantitative Computed Tomography (pQCT) than the Agarose and Defect groups. The histological examination showed characteristic images due to each application form. Consequently, HAp and CaCO3/agarose composite gels can be expected to accelerate the speed of producing more new bone associated with osteogenesis. These novel biomaterials play an important role as an alternative biocompatible and biodegradable bone grafting filler material for autogenous bone.

Identification and molecular characterization of an N-acetylmuramyl-L-alanine amidase Sle1 involved in cell separation of Staphylococcus aureus.

We purified a peptidoglycan hydrolase involved in cell separation from a Staphylococcus aureus atl null mutant and identified its gene. Characterization of the gene product shows a 32 kDa N-acetylmuramyl-L-alanine amidase that we designated Sle1. Analysis of peptidoglycan digests showed Sle1 preferentially cleaved N-acetylmuramyl-L-Ala bonds in dimeric cross-bridges that interlink the two murein strands in the peptidoglycan. An insertion mutation of sle1 impaired cell separation and induced S. aureus to form clusters suggesting Sle1 is involved in cell separation of S. aureus. The Sle1 mutant revealed a significant decrease in pathogenesis using an acute infection mouse model. Atl is the major autolysin of S. aureus, which has been implicated in cell separation of S. aureus. Generation of an atl/sle1 double mutant revealed that the mutant cell separation was heavily impaired suggesting that S. aureus uses two peptidoglycan hydrolases, Atl and Sle1, for cell separation. Unlike Atl, Sle1 is not directly involved in autolysis of S. aureus.