Wnt/ß-Catenin Signaling Promotes the Formation of Preodontoblasts In Vitro.

Odontoblast differentiation is a complex and multistep process regulated by signaling pathways, including the Wnt/ß-catenin signaling pathway. Both positive and negative effects of Wnt/ß-catenin signaling on dentinogenesis have been reported, but the underlying mechanisms of these conflicting results are still unclear. To gain a better insight into the role of Wnt/ß-catenin in dentinogenesis, we used dental pulp cells from a panel of transgenic mice, in which fluorescent protein expression identifies cells at different stages of odontoblast and osteoblast differentiation. Our results showed that exposure of pulp cells to WNT3a at various times and durations did not induce premature differentiation of odontoblasts. These treatments supported the survival of undifferentiated cells in dental pulp and promoted the formation of 2.3GFP+ preodontoblasts and their rapid transition into differentiated odontoblasts expressing DMP1-Cherry and DSPP-Cerulean transgenes. WNT3a also promoted osteogenesis in dental pulp cultures. These findings provide critical information for the development of improved treatments for vital pulp therapy and dentin regeneration.

Comparison of osteogenic and dentinogenic potentials of mice incisor and molar pulps in vitro.

OBJECTIVE: In the present study, we compared the in vitro osteogenic and dentinogenic potential of pulp cells from incisors and molars. DESIGN: Primary pulp cultures were established from DSPP-Cerulean/DMP1-Cherry and BSP-GFPtpz reporter mouse lines and processed for various assays. RESULTS: Our results showed marked differences in dentinogenic and osteogenic potentials of primary cultures from unerupted molars and incisors isolated from 5 to 7 days old pups. While primary cultures from both incisors and molars differentiated into odontoblasts and osteoblasts, cultures from molars differentiated into more DSPP-Cerulean + cells (∼5.5 %) compared to incisor cultures (∼0.7 %) at Day 14 and appear to be more committed to the odontogenic lineage. On the other hand, cultures from incisors show more differentiation into BSP-GFPtpz + cells (∼25 %) compared to molar cultures (∼16 %) and were more committed to the osteogenic lineage. Data were analyzed by Student's t-test and statistical significance was set at P ≤ 0.05. CONCLUSION: Since in the dental pulp, MSCs are the primary source of progenitors capable of giving rise to osteoblasts and odontoblasts, our results provide evidence for differences in the commitment of MSCs in molars and incisors to the odontogenic and osteogenic lineages, respectively.

Expression of BSP-GFPtpz Transgene during Osteogenesis and Reparative Dentinogenesis.

Bone sialoprotein (BSP) is a member of the SIBLING family with essential roles in skeletogenesis. In the developing teeth, although the expression and function of BSP in the formation of acellular cementum and periodontal attachment are well documented, there are uncertainties regarding the expression and function of BSP by odontoblasts and dentin. Reporter mice are valuable animal models for biological research, providing a gene expression readout that can contribute to cellular characterization within the context of a developmental process. In the present study, we examined the expression of a BSP-GFPtpz reporter mouse line during odontoblast differentiation, reparative dentinogenesis, and bone. In the developing teeth, BSP-GFPtpz was expressed at high levels in cementoblasts but not in odontoblasts or dentin. In bones, the transgene was highly expressed in osteoblasts at an early stage of differentiation. Interestingly, despite its lack of expression in odontoblasts and dental pulp during tooth development, the BSP-GFPtpz transgene was detected during in vitro mineralization of primary pulp cultures and during reparative dentinogenesis following pulp exposures. Importantly, under these experimental contexts, the expression of BSP-GFPtpz was still exclusive to DSPP-Cerulean, an odontoblast-specific reporter gene. This suggests that the combinatorial use of BSP-GFPtpz and DSPP-Cerulean can be a valuable experimental tool to distinguish osteogenic from dentinogenic cells, thereby providing an avenue to investigate mechanisms that distinctly regulate the lineage progression of progenitors into odontoblasts versus osteoblasts.

Activation of αSMA expressing perivascular cells during reactionary dentinogenesis.

AIM: To examine the contribution of perivascular cells expressing αSMA to reactionary dentinogenesis. METHODOLOGY: An inducible, Cre-loxP in vivo fate-mapping approach was used to examine the contribution of the descendants of cells expressing the αSMA-CreERT2 transgene to reactionary dentinogenesis in mice molars. Reactionary dentinogenesis was induced by experimental mild injury to dentine without pulp exposure. The Student's t test was used to determine statistical significance at *P ≤ 0.05. RESULTS: The lineage tracing experiments revealed that mild injury to dentine first led to activation of αSMA-tdTomato+ cells in the entire pulp chamber. The percentage of areas occupied by αSMA-tdTomato+ in injured (7.5 ± 0.7%) teeth were significantly higher than in teeth without injury (2 ± 0.5%). After their activation, αSMA-tdTomato+ cells migrated towards the site of injury, gave rise to pulp cells and a few odontoblasts that became integrated into the existing odontoblast layer expressing Col2.3-GFP and Dspp. CONCLUSION: Mild insult to dentine activated perivascular αSMA-tdTomato+ cells giving rise to pulp cells as well as a few odontoblasts that were integrated into the pre-existing odontoblast layer.

FGF2 Enhances Odontoblast Differentiation by αSMA+ Progenitors In Vivo.

The goal of this study was to examine the effects of early and limited exposure of perivascular cells expressing α (αSMA) to fibroblast growth factor 2 (FGF2) in vivo. We performed in vivo fate mapping by inducible Cre-loxP and experimental pulp injury in molars to induce reparative dentinogenesis. Our results demonstrate that early delivery of exogenous FGF2 to exposed pulp led to proliferative expansion of αSMA-tdTomato+ cells and their accelerated differentiation into odontoblasts. In vivo lineage-tracing experiments showed that the calcified bridge/reparative dentin in FGF2-treated pulps were lined with an increased number of Dspp+ odontoblasts and devoid of BSP+ osteoblasts. The increased number of odontoblasts derived from αSMA-tdTomato+ cells and the formation of reparative dentin devoid of osteoblasts provide in vivo evidence for the stimulatory effects of FGF signaling on odontoblast differentiation from early progenitors in dental pulp.

An unusual presentation of LCAT deficiency as nephrotic syndrome with normal serum HDL-C level.

Clinical and biochemical manifestations of lecithin-cholesterol acyltransferase (LCAT) deficiency include an abnormal lipid profile (characterized by hypercholesterolemia with markedly decreased high-density lipoprotein cholesterol [HDL-C] and hypertriglyceridemia), corneal opacities, hematologic abnormalities (normochromic anemia of varying intensity), splenomegaly, variable early coronary artery disease and nephropathy (initially proteinuria followed by progressive deterioration of renal function). We presented a patient with nephrotic syndrome, which renal biopsy revealed classic features of LCAT deficiency. To our knowledge, the present case is the first reported case of LCAT deficiency presenting with symptoms related to nephrotic syndrome in a patient with no obvious family history without any corneal deposits and normal HDL-C levels.

Influence of organic wastes on the biology of epigeic earthworm, Perionyx excavatus during different seasons.

Epigeic earthworm, Perionyx excavatus were cultured on a variety of organic wastes amended with cattle manure in different seasons to know the influence of different organic waste-diets and seasonal environmental factors on life activities of epigeic earthworm, Perionyx excavatus. Results showed that growth and reproductive strategies of P. excavatus varied with different organic waste-diets and seasons. Growth, maturity and reproduction of worms in all waste-diets were significantly more during monsoon followed by winter and summer seasons. All agricultural and garden organic wastes served as a source of balanced diet for this worm during all three seasons. Further, mixed organic waste and soft (straw-based) wastes appeared more congenial for overall life activities of this worm than that of hard (pod-based) wastes (P < 0.001, P < 0.05).

Impact of changed trophic status on the zooplankton composition in six water bodies of Dharwad district, Karnataka state (South India).

The present paper cites results of zooplankton composition that carried out in the six water bodies of Dharwad district during September-November 2004 (post monsoon) and February-April 2005 (pre monsoon). Comparison of the obtained results with those of earlier investigations performed during 1978-1979 showed that changes have occurred in the interval. The total zooplankton composition is significantly changed in all the six water bodies. The lower value of Sorenson and Jaccard indices suggests that significant changes have occurred in the group rotifera and cladocera whereas the higher values for copepoda group suggests least changes. Concurrent occurrence of six Brachionus species in Unkal Lake, four species in Kelgeri, Nuggikeri and Navalur tanks indicate intensified eutrophication. If these habitats have to be preserved for their intended use there is a need for sustainable and holistic management.