Pattern and distribution of extracellular matrix proteins in human reparative dentin by an immunohistochemical approach

Dentin is a large and complex component of the tooth synthesized by odontoblasts during the process of dentinogenesis. Dentin formed, before the completion of root formation, is define primary dentin (PD), while dentin formed after and associated with the normal aging process is designated secondary dentin (SD). Tertiary dentin (TD) is produced in reaction to external noxious stimulus/injury, such as attrition or dental caries, adjacent to the preexisting dentin layer and further classified reparative dentin (RD) (1, 2). Aim this study was to compare pattern and distribution of extracellular matrix proteins, produced by odontoblast cells during dentin mineralization and during reparative process, in response to stimulus in human sound dentin vs human reparative dentin matrix. Sixteen sound carious human molars were selected, demineralized, fixed in paraformaldehyde and then processed for immunohistochemical approach to detect extracellular matrix proteins. In particular specimens were submitted to an immunolabeling technique by using primary antibodies anti dentin matrix protein 1 (DMP1), dentin sialophosphoprotein (DSPP), bone sialoprotein (BSP), osteoponti (OPN). Results indicate that the region of the exposed pulp, formed a layer of reparative dentin bridge sealing the communication between the cavity and pulp chamber. In addition results indicate that in RD is present a lower levels of DMP1 and DSP than PD layer, while BSP and OPN are present in RD but absent in PD layer. The expression of BSP and OPN in RD indicates that the odontoblast-like cells were attempting to produce a hard tissue at a very rapid process. In according with previous scientific literature, our results suggested that the deposition of OPN and BSP at the calcification front is essential for the type I collagen secretion by newly differentiated odontoblast-like cells to form reparative dentin during pulpal healing following cavity preparation

Enhancing Osteoconduction of PLLA-Based Nanocomposite Scaffolds for Bone Regeneration Using Different Biomimetic Signals to MSCs

In bone engineering, the adhesion, proliferation and differentiation of mesenchymal stromal cells rely on signaling from chemico-physical structure of the substrate, therefore prompting the design of mimetic “extracellular matrix”-like scaffolds. In this study, three-dimensional porous poly-L-lactic acid (PLLA)-based scaffolds have been mixed with different components, including single walled carbon nanotubes (CNT), micro-hydroxyapatite particles (HA), and BMP2, and treated with plasma (PT), to obtain four different nanocomposites: PLLA + CNT, PLLA + CNTHA, PLLA + CNT + HA + BMP2 and PLLA + CNT + HA + PT. Adult bone marrow mesenchymal stromal cells (MSCs) were derived from the femur of orthopaedic patients, seeded on the scaffolds and cultured under osteogenic induction up to differentiation and mineralization. The release of specific metabolites and temporal gene expression profiles of marrow-derived osteoprogenitors were analyzed at definite time points, relevant to in vitro culture as well as in vivo differentiation. As a result, the role of the different biomimetic components added to the PLLA matrix was deciphered, with BMP2-added scaffolds showing the highest biomimetic activity on cells differentiating to mature osteoblasts. The modification of a polymeric scaffold with reinforcing components which also work as biomimetic cues for cells can effectively direct osteoprogenitor cells differentiation, so as to shorten the time required for mineralization