Recent development of biomedical engineering as well as basic biology and medicine has enabled us to induce cell-based regeneration of body tissue assisted with the self-repairing potential tissue or substitute biological functions of damaged organs with cells. For successful tissue regeneration, it is indispensable to give cells an environment suitable for induction of cell-based tissue regeneration. Tissue engineering is a newly emerging biomedical technology to create the environment for tissue regeneration with various biomaterials. This paper overviews recent researches and clinical data about oral tissues regeneration based on tissue engineering briefly explaining the key technologies of tissue engineering.

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The adverse effects of smoking on wound healing of the skin are known clinically. Recently, an endogenous cholinergic pathway for angiogenesis mediated by endothelial nicotinic acetylcholine receptors was discovered. The objective of this study was to investigate the appropriate concentration of nicotine that accelerated angiogenesis and wound healing. Experiments on tube formation were conducted using an Angiogenesis Kit. Basic fibroblast growth factor (10ng/ml) and nicotine (10^-10M, 10^-9M, 10^-8M, 10^-7M, 10^-6M, 10^-4M, 10^-2M) were added to the conditioned medium. The conditioned medium was used as a control. The area and length of each tube were calculated using an Angiogenesis Image Analyzer. Full-thickness skin defects (8mm) were created on the dorsum of C57BL mice and a silicone sheet (8mm) was sutured. PBS (10μl), bFGF (1μg), and nicotine (10^-1M, 10^-4M, 10^-7M) were topically injected for seven days (n=5). Significant differences in area and length of newly formed tubes were seen between the control group and bFGF and the 10^-10M nicotine-added groups. The wound area was significantly decreased in the wound treated with bFGF and 10^-4M of nicotine. The epithelium length was significantly longer in the wounds treated with bFGF and 10^-4M of nicotine. In this study, nicotine accelerated angiogenesis and promoted wound healing.

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According to the World Health Organization(WHO) guidelines for patients with moderate or severe pain, morphine has been used as a “gold standard” treatment for cancer pain. However, the use of morphine for the treatment of pain was sometimes accompanied with side effects such as emesis, constipation and drowsiness.
We showed that morphine at the dose of which had no antinociceptive effect produced emetic response and gastrointestinal transit inhibition. It should be mentioned that morphine with lower doses produces severe side effects without antinociception/analgesia.
Recent clinical studies have demonstrated that when morphine is used to control pain, psychological dependence is not a major concern. We confirmed that animals with chronic pain failed to exhibit the morphine-induced rewarding effect. It should be pointed out that the endogenous κ-opioidergic system in the nucleus accumbens may be directly involved in the suppression of the morphine-induced rewarding effect under an inflammatory pain-like state. In contrast, the reduction of μ-opioid receptor function in the ventral tegmental area may contribute to the suppression of the rewarding effect induced by morphine under an neuropathic pain-like state. These findings strongly suggest that treatment of morphine with the adequate dose could be highly recommended for the relief of severe chronic pain.

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Mammalian myeloid and epithelial cell express several antibacterial peptides (defensins and cathelicidins) that contribute to the innate host defense by killing invaded microorganisms. CAP11 (cationic antibacterial polypeptide of 11kDa), which was isolated from guinea pig neutrophils, has been shown to possess the potent bactericidal and LPS-neutralizing activities. CAP11 is a homodimer of Gly¹-Ile⁴³ joined with one disulfide bond. In this study, we revealed that the dimerization of the peptides is not essential for its biological activity, and 18mer peptide of CAP11(G¹-R¹⁸) is the most potent among various peptide derivatives. However, its biological activities were much lower compared with native CAP11. Furthermore, we tried to enhance the biological activities of CAP11(G¹-R¹⁸) by substituting amino acids. Two novel peptides, CAP11(1-18m) and CAP11(1-18m2), whose hydrophobicity and positive charge were modified by the amino acid substitutions, exhibited more potent bactericidal activities against S.aureus and E.coli, and more strongly inhibited the LPS-binding to CD14⁺ RAW264.7 cells, compared with CAP11; i.e. the bactericidal and LPS-neutralizing activities of CAP11(1-18m2) was about 10-fold greater than those of CAP11, and CAP11(1-18m2) completely killed both methicillin-sensitive S.aureus (MSSA) and methicillin-resistant S.aureus (MRSA) even at 0.1μg/ml.
Thus, the bactericidal and LPS-neutralizing activities of CAP11-derived antibacterial peptides could be enhanced by the modification of their hydrophobicity and positive charge via the amino acid substitutions.

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ADP-ribosylation factors(ARFs) are 20-kDa GTP-binding proteins involved in the vesicular trafficking, the activation of phospholipase D and phosphatidylinositol 4-phosphate 5-kinase, and the modulation of phagocyte functions. Like other GTP-binding proteins, ARFs cycle between GTP-bound, active and GDP-bound, inactive status. Guanine nucleotide-exchange proteins(GEPs), which catalyze the change of bound GDP for GTP, are necessary for the activation of ARFs. Previously, we found a novel GEP with 100kDa, named ARF-GEP₁₀₀. In this study, we elucidated the role in ARF-GEP₁₀₀ on phagocyte functions by transfection of ARF-GEP₁₀₀.
Overexpression of ARF-GEP₁₀₀ induced apoptosis of mouse macrophage RAW264.7 cells and phorbol 12- myristate 13-acetate treated human monocyte U937 cells, which could be detected by morphological changes (nuclear condensation and formation of apoptotic bodies), annexin V-staining and TUNEL assay. ARF-GEP₁₀₀- induced apoptosis was not inhibited by a caspase inhibitor zVAD-FMK. Furthermore, mutant analysis of ARFGEP₁₀₀ revealed that two regions (N- and C- termini) of ARF-GEP₁₀₀ were essential for the induction of apoptosis, but the mutant defective in GDP-GTP exchange domain induced apoptosis. These results suggest that ARFGEP₁₀₀ induces apoptosis of monocytic phagocytes independent of both the caspase activation and GDP-GTP exchange activity.

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PC-SOD (Lecithinized superoxide dismutase) is 4 molecules of a lecithin derivative-bound SOD, an enzyme of scavenging superoxide anion (O₂^-). Intravenous administration of PC-SOD (1 mg/kg) promoted the recovery from spinal cord injury (SCI)-induced motor dysfunction, when evaluated by BBB (Basso Beattie Bresnahan) score. The potency of PC-SOD was superior to that of methylprednisolone (MP) (30 mg/kg), which is now in clinical use. PC-SOD as well as MP inhibited SCI-induced neutrophil infiltration. The damaged area in PC-SOD treated spinal cord was less, as compared to that in MP-treated one. PC-SOD had only a little effect on gene expression of inflammatory cytokines and neurotrophic factors. However, MP suppressed not only gene expression but production. Different from MP, PC-SOD significantly promoted the production of GDNF. These data indicated that one reason why PC-SOD was superior might be ascribed partly to the increase of GDNF production.

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