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PubMed1994

The role of guided tissue regeneration and guided bone regeneration.

The goal of periodontal therapy includes not only the halting of the progressive loss of connective tissue attachment but also the restitution of those parts of the supporting apparatus which have been destroyed. The cells which repopulate this area may originate from any number of the different tissue components of the periodontium: the dentogingival epithelium, the gingival connective tissue, the alveolar bone, and the periodontal ligament (PDL). The size and shape of the wound and the potential of the different types of tissues cells to migrate, determines the type of healing. Previous studies have revealed that root resorption was found to occur when granulation tissue derived from the gingival connective tissue or alveolar bone was proliferating into contact with the root surface, while re-epithelialization of the surface prevented both connective tissue attachment and root resorption. The only cells which appear to have the capacity to form a new attachment were cells originating from the PDL. Based on this knowledge of the biological behaviour of the different periodontal tissues during wound healing, the principle of Guided Tissue Regeneration (GTR) was introduced and tested. A membrane section was placed over the debrided root surface in such a way that all periodontal tissues except the PDL cells were prevented from reaching contact with the root. Healing resulted in extensive amounts of new connective tissue attachment, that is, the formation of new cementum with inserting collagen fibres. The objective was, and is, assessment of how predictably new attachment may form when treatment included GTR.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar Bone Loss↗
PubMed2005

The neuronal growth and regeneration associated Cntn1 (F3/F11/Contactin) gene is duplicated in fish: expression during development and retinal axon regeneration.

The Cntn1 (Contactin/F3/F11) cell adhesion molecule is involved in axon growth and guidance, fasciculation, synapse formation, and myelination in birds and mammals. We identified Cntn1 genes in goldfish, zebrafish, and fugu, and provide evidence for a fish-specific duplication leading to Cntn1a and Cntn1b. Our analyses suggest a subfunctionalization for the Cntn1 paralogs in zebrafish compared to other vertebrates which have a single Cntn1 gene. Similar to Cntn1a, Cntn1b transcripts are found in subsets of sensory and motor neurons. However, Cntn1b is detected later and more restricted than Cntn1a. This spatio-temporal expression pattern of the two zebrafish Cntn1 paralogs suggests functions related to those of mammalian Cntn1. In adult goldfish, Cntn1b is expressed in oligodendrocytes and is upregulated in retinal ganglion cells after optic nerve transection, which is consistent with an additional role during regeneration.

Animals↗
PubMed2002

A systematic review of guided tissue regeneration for periodontal furcation defects. What is the effect of guided tissue regeneration compared with surgical debridement in the treatment of furcation defects?

OBJECTIVES: To systematically review the evidence of effectiveness of guided tissue regeneration (GTR) for furcation defects. BACKGROUND: The evidence for the effectiveness of GTR in furcation defects has not yet been systematically appraised. METHODS: We searched for randomized controlled trials with at least 6 months' follow-up comparing GTR with surgical debridement (open flap debridement, OFD). Data sources included electronic databases, hand-searched journals and contact with experts. Screening, data abstraction and quality assessment were conducted independently by multiple reviewers. The primary outcome measure was reduction in open horizontal furcation depth, secondary outcomes were frequency of furcation closure, gain in horizontal and vertical probing attachment and reduction of vertical probing depth. RESULTS: For the primary outcome, reduction in horizontal furcation depth assessed during re-entry, the weighted mean difference between GTR and control was 1.51 mm (95% CI [0.39-2.62], chi-square for heterogeneity 67.6 (df = 3), P < 0.001) in mandibular class II furcations, 1.05 mm (95% CI [0.46-1.64, chi-square for heterogeneity 34.9 (df = 3), P < 0.001) in maxillary class II furcations, and 0.87 mm (95% CI [-0.08-1.82], chi-square for heterogeneity 0.1 (df = 4), P = 0.991) in studies that had combined mandibular and maxillary class II furcations. For the secondary outcomes, GTR treatment led to significantly better results than open flap debridement. No meta-analysis could be performed for frequency of furcation closure because of sparse data. CONCLUSIONS: Overall, GTR was consistently more effective than OFD in reducing open horizontal furcation depths, horizontal and vertical attachment levels and pocket depths for mandibular or maxillary class II furcation defects. However, these improvements were modest, variable and there was only a limited number of studies available to appraise the effects, thus limiting general conclusions about the clinical benefit of GTR. Future studies should aim to identify factors associated with achieving consistent and more pronounced benefits over open flap debridement.

Furcation Defects↗
PubMedDate not supplied

Autogenous injectable bone for regeneration with mesenchymal stem cells and platelet-rich plasma: tissue-engineered bone regeneration.

We have attempted to regenerate bone in a significant osseous defect with minimal invasiveness and good plasticity, and to provide a clinical alternative to autogenous bone grafts. Platelet-rich plasma (PRP) may enhance the formation of new bone and is nontoxic, nonimmunoreactive, and accelerates existing wound-healing pathways. We have used a combination of PRP as an autologous scaffold with in vitro-expanded mesenchymal stem cells (MSCs) to increase osteogenesis, compared with using the scaffold alone or autogenous particulate cancellous bone and marrow (PCBM). The newly formed bones were evaluated by radiography, histology, and histomorphometric analysis in the defects at 2, 4, and 8 weeks. According to the histological observations, the dog MSCs (dMSCs)/PRP group had well-formed mature bone and neovascularization compared with the control (defect only), PRP, and PCBM groups at 2 and 4 weeks. Histometrically, at 8 weeks newly formed bone areas were 18.3 +/- 4.84% (control), 29.2 +/- 5.47% (PRP), 61.4 +/- 3.38% (PCBM), and 67.3 +/- 2.06% (dMSCs/PRP). There were significant differences between the PCBM, dMSCs/PRP, and control groups. These results demonstrate that the dMSCs/PRP mixture is useful as a osteogenic bone substitute.

Animals↗
PubMed2006

Differentiation and regeneration of adrenal tissues: An initial step toward regeneration therapy for steroid insufficiency.

In animal experiments, adrenal cortical tissue has been successfully regenerated through xenotransplantation of cloned adrenocortical cells, suggesting that the intraadrenal stem cells required for such tissue formation may be present in the adrenal cortex. Stable expression of Ad4BP/SF-1, a key factor for adrenal and gonadal development and steroidogenesis, has been shown to direct embryonic stem cells toward the steroidogenic lineage. However, this steroidogenic capacity was very limited since progesterone was only produced in the presence of an exogenous substrate. Bone marrow mesenchymal cells are thought to contain pluripotent progenitor cells, which differentiate into multiple lineages. We have demonstrated that adenovirus-mediated forced expression of SF-1 in long-term cultured bone marrow cells can produce steroidogenic cells with the capacity for de novo synthesis of various steroid hormones in response to ACTH. This discovery may represent the first step in autologous cell transplantation therapy for patients with steroid hormone deficiency.

Adrenal Cortex↗
PubMed1990

[Adrenal regeneration hypertension--effects of vascular connective tissue protein and plasma corticosterone on hypertension in rats with adrenal regeneration hypertension].

In young rats consuming 1% NaCl drinking solution, unilateral nephrectomy and bilateral adrenal enucleation caused a hypertension. Plasma corticosterone concentration in hypertensive rats was not significantly higher than that of normotensive control rats in early hypertensive or chronic hypertensive stage. At the end of experiment, each rat received an intravenous injection of 0.4 microCi/g of 3H-lysine and was sacrificed 2 hours after the injection. Incorporation of 3H-lysine into collagen or elastin of the mesenteric artery and heart in hypertensive rats was greater than that of normotensive rats. Administration of phenoxybenzamine hydrochloride lower the blood pressure of hypertensive rats and reduced the incorporation of 3H-lysine into collagen and elastin of the mesenteric artery and heart. From these findings, increased protein synthesis of collagen and elastin in hypertensive rats appears to play an important role for the maintenance of adrenal regeneration hypertension.

Adrenal Glands↗
PubMed2003

[Clinical comparison between guided tissue regeneration and induced tissue regeneration].

AIM: The aim of the present study was to evaluate, over a period of 1 y, 3 different surgical methods for the treatment of periodontal bone defects. METHODS: Thirty-six infrabone defects, at least 4 mm in depth, in non-smokers were enrolled in the study. Of these, 12 were treated with guided tissue regeneration (GTR) using a resorbable membrane with collagen, 12 with enamel matrix derivative (EMD) gel and 12 with a modified Widman flap (MWF). The pocket depth, attachment loss and gingival recession both before commencement of therapy and after an interval of 1 y are reported. RESULTS: The reduction in pocket depth was 4 mm, 4.4 mm, and 4.5 mm, respectively, for the control group, GTR group and EMD group. The attachment gain for the respective treatments was: MWF, 2 mm; GTR, 2.8 mm; EMD, 2.9 mm. Gingival recession was: MWF, 1.8 mm; GTR, 1.5 mm; EMD, 1.1 mm. CONCLUSION: These findings show the efficacy of the 3 methods in the treatment of bone defects, but none of the 3 emerges as being statistically superior to the others 2.

Adult↗
PubMed1990

[Liver regeneration and immune system--morphological and cytochemical studies of activated spleen cells during the liver regeneration after partial hepatectomy].

Morphological and cytochemical changes were investigated in spleen cells after 70% hepatectomy in mice. During liver regeneration after the hepatectomy, the spleen weight gradually rose to a peak at 6 day. In the spleen, the number of POD-positive myelocytic cells and NCAE-positive granulocytic cells also reached a peak 4 days after the operation and then decreased. On the other hand, ANBE-positive monocytic cells gradually increased up to 9 day and didn't decrease for this period. On day 9 of the culture, the boundary between the red and the white pulps of the spleen became unclear. In this spleen, the clusters of blast cells were sporadically observed. Splenic T cells cocultured with nonparenchymal adherent normal liver cell or nonparenchymal adherent normal liver cell supernatant developed into granulocyte colonies in earlier periods and monocyte colonies in later periods. These findings suggest that the factors released from liver cells may regulate strictly spleen cell activation. Blast cell formation in the culture with nonparenchymal adherent normal liver cell supernatant was amplified by anti interferon (alpha + beta) antibody. These facts indicate that the functional network of cytokines is formed by the interaction of various cytokines (IL-1, IL-6, CSF, IFN, etc.) in nonparenchymal adherent normal liver cell supernatant.

Animals↗
PubMed1983

[Peculiarities of nuclear genome transcription in the early stages of liver regeneration. Complex nature of the activating effect of the cytoplasmic regenerating factor on transcription in isolated rat liver nuclei].

The cytosol fractions from resting rat liver and from the liver 1 hour after partial hepatectomy which were not adsorbed on DEAE-cellulose were subjected to gel filtration with a view of elucidating the mechanism of its activating effect on the RNA-synthesizing ability of isolated nuclei of resting liver. The activating effect of this fraction is a complex one and includes both specific and non-specific factors. A subfraction typical for regenerating liver was detected, which activates RNA elongation in a synthesizing system with isolated nuclei of resting liver.

Animals↗
PubMed1980

[Studies on regeneration and adhesion of the tendon. Part 7: Influence of the vincula on regeneration of the tendon (author's transl)].

Repair of the flexor digitorum profundus (FDP) of the chicken was studied by light microscopic and microangiographic examination. The effects of altered circulation in the vincula breve were related to repair processes of tendon. Sixty young-adult chickens weighing 2 to 3 kg were used. The FDP tendons of the third toes were incised and sutured without anesthesia, then the vincula breve was cut and ligated. In the control group, no procedure was performed to the vincula breve. Samples were obtained at the fixed time intervals up to 8 weeks after the operation. For microangiography, Micropaque solution was injected into the femoral artery after perfusion of physiological saline. The amputated legs were fixed in 10% formalin, subcutaneous tissues removed, then soft X-ray examination performed using Softex-CMB. Histological specimens were stained with hematoxylin-eosin. The results were as follows: 1) In the group with ligated vincula, delay of cellular reaction in the repair process was histologically evident in the early stages. There were little granulation and proliferation of the dorsal epitenon, which formed adhesion with surrounding tissues in the later stages. 2) In the angiographic examination, the sutured site of the tendon was not avascular, and compensatory proliferation of the periosteal and capsular vessels was found around the suture although the vincula breve had been ligated. However, there was a somewhat impaired circulatory pattern in the group with ligated vincula during the early stages. Later, normalization of the circulation was delayed compared to the control samples. 3) Damage of the vincula was thought to delay regeneration in tendon injuries. Poor circulation, if present, may also influence the healing process by inducing adhesion of the surrounding tissues.

Animals↗
PubMed1977

[Quantitative studies on the regeneration of myelinated nerve fibers. III. Variations in the number and size of regenerated fibers after localized freezing].

The number and size of myelinated nerve fibers have been determined at standard levels in the nerve to medial head of right and left gastroenemius muscles of 45 rats in which the left sciatic nerve had suffered an localized freezing. The nerves have been observed from 10 to 720 days after the operation. In the contralateral nerve, the number of myelinated fibers decreased in average to 18.8%, the mean diameter to 11,2%. Male rats appeared to be more sensitive than female to the effects of the operation. In the regenerating nerve, the number of myelinated fibers returned to normal during 4th week and later increased up to a mean of 124%. Their distribution became bimodal after the 60th day. Both histograms could be superposed by the 330th day and the mean diameter came back to normal soon afterwards.

Animals↗
PubMed1982

Regeneration of RNase A from the reduced protein: models of regeneration pathways.

Two models of protein-folding pathways are proposed on the basis of equilibrium and kinetic data in the literature. One is a growth-type model--i.e., nucleation of the native-like structure occurs in the folding process, in the rate-limiting step(s), and subsequent folding around the nucleation sites proceeds smoothly to form the native disulfide bonds and conformation. The other is a rearrangement-type model--i.e., proper nucleation does not occur in the folding process; instead, non-native interactions play a significant role in the folding pathways and lead to metastable intermediate species. Such non-native interactions, including incorrect disulfide bonds and proline cis-trans isomerization, must be disrupted or rearranged to nucleate the native interactions [a process that is included in the rate-limiting step(s)] for the protein to fold. The rate-limiting steps in the pathways for regeneration of RNase A from the reduced protein are classified as growth- or rearrangement-type pathways. The growth-type pathway is the one accompanying the formation of an intramolecular disulfide bond in the rate-limiting step. The rearrangement-type pathway is the one accompanying the reshuffling or disruption of a disulfide bond in the rate-limiting step. The folding of other proteins, accompanying oxidation of the reduced form, and the folding of denatured proteins with intact disulfide bonds are discussed in terms of the growth- and rearrangement-type models.

Endoribonucleases↗