Umadevi Kandalam

Swelling and Mechanical Properties of Modified HEMA-based Superporous Hydrogels

Superporous hydrogels (SPHs), based on poly(2-hydroxyethyl methacrylate) (PHEMA), were prepared by adding minute amounts of an ion-complexable hydrophilic acrylic acid. PHEMA SPHs are generally strong, but their swelling is minimal. To improve the swelling, different poly(HEMA-co-acrylic acid) hydrogels were polymerized and crosslinked, then physically treated with divalent calcium and trivalent aluminum cations. The incorporation of acrylic acid copolymer into the SPH, followed by crosslinking of the copolymer with calcium or aluminum ions produced SPHs with improved swelling and strength. Cells in the presence of hydrogel showed high viability indicating the absence of cytotoxicity and stimulatory effect.

Optimized Platelet Rich Fibrin With the Low Speed Concept: Growth Factor Release, Biocompatibility and Cellular Response.

BACKGROUND Over the past decade, use of leukocyte platelet-rich fibrin (L-PRF) has gained tremendous momentum in regenerative dentistry as a low-cost fibrin matrix used for tissue regeneration. This study characterizes how centrifugation speed (G-force) along with centrifugation time influence growth factor release from fibrin clots, as well as the cellular activity of gingival fibroblasts exposed to each PRF matrix. METHODS Standard L-PRF served as a control (2,700 revolutions per minute [rpm]-12 minutes). Two test groups using low-speed (1,300 rpm-14 minutes, termed advanced PRF [A-PRF]) and low-speed + time (1,300 rpm-8 minutes; A-PRF+) were investigated. Each PRF matrix was tested for growth factor release up to 10 days (eight donor samples) as well as biocompatibility and cellular activity. RESULTS The low-speed concept (A-PRF, A-PRF+) demonstrated a significant increase in growth factor release of platelet-derived growth factor (PDGF), transforming growth factor (TGF)-β1, epidermal growth factor, and insulin-like growth factor, with A-PRF+ being highest of all groups. Although all PRF formulations were extremely biocompatible due to their autogenous sources, both A-PRF and A-PRF+ demonstrated significantly higher levels of human fibroblast migration and proliferation compared with L-PRF. Furthermore, gingival fibroblasts cultured with A-PRF+ demonstrated significantly higher messenger RNA (mRNA) levels of PDGF, TGF-β, and collagen1 at either 3 or 7 days. CONCLUSIONS The findings from the present study demonstrate modifications to centrifugation speed and time with the low-speed concept favor an increase in growth factor release from PRF clots. This, in turn, may directly influence tissue regeneration by increasing fibroblast migration, proliferation, and collagen mRNA levels. Future animal and clinical studies are now necessary.

Mesenchymal stem cells and alginate microcarriers for craniofacial bone tissue engineering: A review

Craniofacial bone is a complex structure with an intricate anatomical and physiological architecture. The defects that exist in this region therefore require a precise control of osteogenesis in their reconstruction. Unlike traditional surgical intervention, tissue engineering techniques mediate bone development with limited postoperative risk and cost. Alginate stands as the premier polymer in bone repair because of its mild ionotropic gelation and excellent biocompatibility, biodegradability, and injectability. Alginate microcarriers are candidates of choice to mediate cells and accommodate into 3-D environment. Several studies reported the use of alginate microcarriers for delivering cells, drugs, and growth factors. This review will explore the potential use of alginate microcarrier for stem cell systems and its application in craniofacial bone tissue engineering.

Viability of human umbilical cord–derived mesenchymal stem cells in G-rich and M-rich alginates

In this study, the effect of pharmaceutical-grade alginates on the cell viability of human mesenchymal stem cells derived from umbilical cord was examined and their use in tissue engineering applications was evaluated. The effects of the ratio of the copolymer building blocks (guluronic and mannuronic acids) and their interactions with divalent calcium, the purity of alginates (proteins and polyphenol content), and gelation factors (calcium concentration and sol content) were examined. The high guluronic acid content in the alginates improved the viability of the human mesenchymal stem cells derived from umbilical cord and supported cell growth significantly. It was confirmed that the sol fraction of alginate reduced cell viability. Cells in the presence of alginate beads cross-linked with 50 and 100 mM calcium chloride showed maximum viability; the protein and polyphenol content of the alginates did not affect the viability of the human mesenchymal stem cells derived from umbilical cord, while the monomer ratio did have an obvious effect.

Angiotensin II induces cell growth and IL-6 mRNA expression through the JAK2-STAT3 pathway in rat cerebellar astrocytes

The pleiotrophic effects of angiotensin II (Ang II) play important roles in astrocyte growth and inflammatory responses. We investigated whether Ang II induces astrocyte growth and interleukin-6 (IL-6) mRNA expression in rat cerebellar astrocytes through Janus kinase 2-signal transduction activator of transcription (JAK2-STAT3). Ang II increased JAK2 and STAT3 phosphorylation in a time- and a dose-dependent manner. One hundred nanomolar Ang II induced maximal phosphorylation of both JAK2 and STAT3 between 15 min and 30 min. The Ang II-mediated phosphorylation of both JAK2 and STAT3 was blocked by AG490, a selective JAK2 inhibitor. Losartan, a selective AT1 receptor antagonist, inhibited Ang II-mediated JAK2 and STAT3 phosphorylation, while pretreatment with an AT2 receptor blocker, PD123319, was ineffective. Ang II increased the mRNA expression of IL-6 in a concentration-and time-dependent manner. Maximal IL-6 mRNA expression occurred with 100 nM Ang II, and the peak effect occurred in a biphasic manner at 3 h and between 12 and 24 h. Moreover, pretreatments with AG490 attenuated Ang II-induced IL-6 mRNA levels, and Ang II-induced astrocyte growth. This study has demonstrated that Ang II induced the phosphorylation of both JAK2 and STAT3 via the AT1 receptor in cerebellar astrocytes. In addition, our results suggest that JAK2 and STAT3 are upstream signals that mediate Ang II-induced IL-6 mRNA expression and astrocyte growth. These findings represent a novel non-classical mechanism of Ang II signaling in cerebellar astrocytes.

Swelling, strength, and biocompatibility of acrylate-based superporous hydrogel hybrids

A hydrogel hybrid of chemically cross-linked hydroxyethyl acrylate interpenetrated with physically cross-linked carboxymethylcellulose was prepared as a superporous structure with swelling rates ranging from a few seconds to minutes depending on the swelling medium. A new method was adopted to evaluate the swelling capacity and rate in superporous hydrogel hybrid using a modified texture analyzer. Based on the extensive data acquisition, swelling data at any time point were obtainable and fit into a Voigt viscoelastic model. Moreover, the two mechanisms by which a superporous hydrogel hybrid swells in an aqueous medium were differentiated and used to estimate the onset of the diffusion-controlled swelling, which was found to be dependent on the actual composition of the swelling medium. A correlation was found between the mechanical strength of the fully swollen hydrogels and their respective swelling force in different swelling media. The concentration of alcohol in the medium was a critical factor in the swelling characteristics and strength of these hydrogels. Two HeLa and mesenchymal stem cells derived from human umbilical cord cell lines were used to evaluate biocompatibility of the prepared hydrogels.

Angiotensin III induces signal transducer and activator of transcription 3 and interleukin-6 mRNA levels in cultured rat astrocytes

Introduction: Recently we established that pro-inflammatory actions of angiotensin (Ang) II in astrocytes involved Janus kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3), and interleukin-6 (IL-6). Materials and methods: In our current study, we determined in brainstem and cerebellum whether Ang III also activates STAT3 leading to IL-6 mRNA expression and astrocyte proliferation. Results: Ang III induced STAT3 phosphorylation in a concentration- and time-dependent manner. Significant STAT3 phosphorylation was rapid and was maximal within 10 min, and with 100 nM Ang III. The Ang AT1 receptor was shown to mediate this action of Ang III. Ang III also significantly induced IL-6 mRNA expression within an hour, and maximal Ang III-mediated IL-6 mRNA expression occurred in the presence of 100 nM Ang III. Ang III-mediated IL-6 mRNA expression occurred by the interaction of the peptide with the Ang AT1 receptor and was mediated by STAT3. In addition, STAT3 was shown to mediate Ang III astrocyte proliferation. Conclusions: These findings suggest that Ang III, similar to Ang II, has pro-inflammatory effects since it induces STAT3 leading to an induction of IL-6 mRNA expression, outcomes that lend relevance to the physiological importance of central Ang III.

Three-dimensional macroporous materials for tissue engineering of craniofacial bone

Repair of critical-size defects caused by trauma, removal of a tumour, or congenital abnormalities is a challenge in the craniomaxillofacial region because of the limitations associated with treatment. We have reviewed research papers and updated information relevant to the various types of macroporous scaffolds. We have included papers on several biomaterials and their use in various craniofacial defects such as mandibular, calvarial, and others, as well as the latest technological developments such as 3-dimensional printed scaffolds. We selected all papers about scaffolds, stem cells, and growth factors for review. Initial selection was by review of titles and abstracts, and the full texts of potentially suitable articles were then assessed. Methods of tissue engineering for repair of critical-size defects in the craniofacial bones seem to be viable options for surgical treatment in the future. Macroporous scaffolds with interconnected pores are of great value in regeneration of bone in the craniofacial region. In recent years, various natural or synthetic materials, or both, have been developed, on which macroporous scaffolds can be based. In this review we present a review on the various types of three-dimensional macroporous scaffolds that have been developed in recent years, and evaluate their potential for regeneration of craniofacial bone.

Comparative assessment of growth supporting potential of different alginic acid salts

ABSTRACT This study compares the cell survival of HeLa, osteoblasts (MG 63), and human umbilical cord stem cells (hUMSCs) in three different salts of alginic acid including sodium, potassium, and triethanolamine. While the treatment of the cells with wide range of concentrations of potassium and triethanolamine alginate did not adversely affect the cell growth, higher concentrations of sodium alginate inhibited cell growth on all the cell types tested. Furthermore, the cells encapsulated in potassium alginate beads showed enhanced cell survival compared to the growth in other salts. Our results indicated that potassium alginate can be used with wide varieties of cell types. GRAPHICAL ABSTRACT