Direct pulp capping is an effective treatment for preserving dental pulp against carious or traumatic pulp exposure via the formation of protective reparative dentin by odontoblast-like cells. Reparative dentin formation can be stimulated by several signaling molecules; therefore, we investigated the effects of secreted frizzled-related protein (SFRP) 1 that was reported to be strongly expressed in odontoblasts of newborn molar tooth germs on odontoblastic differentiation and reparative dentin formation. In developing rat incisors, cells in the dental pulp, cervical loop, and inner enamel epithelium, as well as ameloblasts and preodontoblasts, weakly expressed Sfrp1; however, Sfrp1 was strongly expressed in mature odontoblasts. Human dental pulp cells (hDPCs) showed stronger expression of SFRP1 compared with periodontal ligament cells and gingival cells. SFRP1 knockdown in hDPCs abolished calcium chloride-induced mineralized nodule formation and odontoblast-related gene expression and decreased BMP-2 gene expression. Conversely, SFRP1 stimulation enhanced nodule formation and expression of BMP-2. Direct pulp capping treatment with SFRP1 induced the formation of a considerable amount of reparative dentin that has a structure similar to primary dentin. Our results indicate that SFRP1 is crucial for dentinogenesis and is important in promoting reparative dentin formation in response to injury.

We aimed to generate periodontal ligament (PDL) tissue-like structures from a multipotent human PDL cell line using three-dimensional (3D) bioprinting technology and to incorporate these structures with bioactive core materials to develop a new biohybrid implant system. After 3D bioprinting, single-cell spheroids were able to form 3D tubular structures (3DTBs). We established three types of complexes using 3DTBs and different core materials: 3DTB-titanium core (TIC), 3DTB-hydroxyapatite core (HAC), and 3DTB without a core material (WOC). The expressions of PDL-, angiogenesis-, cementum-, and bone-related genes were significantly increased in the three complexes compared with monolayer-cultured cells. Abundant collagen fibers and cells positive for the above markers were confirmed in the three complexes. However, more positive cells were detected in HAC than in WOC or TIC. The present results suggest that 3D-bioprinted structures and hydroxyapatite core materials can function similarly to the PDL and may be useful for the development of a new biohybrid implant system.

White mineral trioxide aggregate (WMTA) is a root canal treatment material, which is known to exhibit a dark brown color when in contact with sodium hypochlorite solution (NaOCl). This study aimed to investigate the effects of NaOCl on the surface properties of WMTA discs and WMTA-induced osteoblastic differentiation of periodontal ligament stem cells (PDLSCs). Mixed WMTA (ProRoot MTA) was filled into the molds to form WMTA discs. These discs were immersed in distilled water (D-WMTA) or 5% NaOCl (Na-WMTA). Their surface structures and Ca2+ release level was investigated. Moreover, they were cultured with a clonal human PDLSC line (line 1–17 cells). The main crystal structures of Na-WMTA were identical to the structures of D-WMTA. Globular aggregates with polygonal and needle-like crystals were found on D-WMTA and Na-WMTA, which included Ca, Si, Al, C and O. However, many amorphous structures were also identified on Na-WMTA. These structures consisted of Na and Cl, but did not include Ca. NaOCl immersion also reduced Ca2+ release level from whole WMTA discs. Line 1–17 cells cultured with D-WMTA formed many mineralized nodules and exhibited high expression levels of osteoblast-related genes. However, cells incubated with Na-WMTA generated a small number of nodules and showed low expression levels of osteoblast-related genes. These results indicated that NaOCl reduced Ca2+ release from WMTA by generating amorphous structures and changing its elemental distribution. NaOCl may also partially abolish the ability of WMTA to stimulate osteoblastic differentiation of PDLSCs.

Myelodysplasia syndrome 1 (MDS1) and Ecotropic viral integration site 1 (EVI1) complex (MECOM) locus encode multiple isoforms of the EVI1 protein that are essential for normal vertebrate development and when inappropriately expressed play a significant role in malignancy and in particular leukaemias. However, the function of individual EVI1 isoforms is not fully understood. Recently, EVI1 or PRDM3, which is structurally closely related to the brown adipose tissue determining factor PRDM16, was shown to be required for differentiation of adipocytes. In this study, we show that 3T3-L1 preadipocytes sustain expression of all Evi1 isoforms examined, including Mds1-Evi1, Evi1FL, Evi1Δ324, Evi1FL + 9 and Evi1Δ105 throughout the adipogenesis differentiation programme. We also show that differentiation markers are enhanced by enforced expression of either Evi1, Evi1FL + 9 or Evi1Δ105 isoforms. Interestingly 3T3-L1 differentiation markers are also moderately enhanced by enforced expression of Evi1Δ324, which lacks part of the N-terminal zinc finger domain (ZF1), demonstrating a biological activity for this particular isoform. Enforced expression of an Evi1 mutant lacking C-terminal binding protein (CtBP) co-repressor protein binding activity fails to stimulate 3T3-L1 differentiation markers and may have dominant negative activity, causing partial inhibition of this developmental programme. These studies show that multiple EVI1 isoforms are expressed in adipocytes and can stimulate adipogenic markers in a manner that is partially independent of the ZF1 DNA binding domain but fully dependent upon interaction with co-repressor CtBP proteins.