Peyman Dinarvand

New approach to bone tissue engineering: simultaneous application of hydroxyapatite and bioactive glass coated on a poly(L-lactic acid) scaffold.

A combination of bioceramics and polymeric nanofibers holds promising potential for bone tissue engineering applications. In the present study, hydroxyapatite (HA), bioactive glass (BG), and tricalcium phosphate (TCP) particles were coated on the surface of electrospun poly(L-lactic acid) (PLLA) nanofibers, and the capacity of the PLLA, BG-PLLA, HA-PLLA, HA-BG-PLLA, and TCP-PLLA scaffolds for bone regeneration was investigated in rat critical-size defects using digital mammography, multislice spiral-computed tomography (MSCT) imaging, and histological analysis. Electrospun scaffolds exhibited a nanofibrous structure with a homogeneous distribution of bioceramics along the surface of PLLA nanofibers. A total of 8 weeks after implantation, no sign of complication or inflammation was observed at the site of the calvarial bone defect. On the basis of imaging analysis, a higher level of bone reconstruction was observed in the animals receiving HA-, BG-, and TCP-coated scaffolds compared to an untreated control group. In addition, simultaneous coating of HA and BG induced the highest regeneration among all groups. Histological staining confirmed these findings and also showed an efficient osseointegration in HA-BG-coated nanofibers. On the whole, it was demonstrated that nanofibrous structures could serve as an appropriate support to guide the healing process, and coating their surface with bioceramics enhanced bone reconstruction. These bioceramic-coated scaffolds can be used as new bone-graft substitutes capable of efficiently inducing osteoconduction and osseointegration in orthopedic fractures and defects.

Polyphosphate amplifies proinflammatory responses of nuclear proteins through interaction with receptor for advanced glycation end products and P2Y1 purinergic receptor

The extracellular nuclear proteins, histone H4 (H4) and high mobility group box 1 (HMGB1), released by injured cells during the activation of inflammation and coagulation pathways provoke potent inflammatory responses through interaction with pathogen-related pattern recognition receptors (ie, Toll-like receptors [TLRs] and receptor for advanced glycation end products [RAGE]) present on vascular and innate immune cells. Inorganic polyphosphate (polyP) has emerged as a key modulator of coagulation and inflammation. Here, we demonstrate that polyP binds to both H4 and HMGB1 with high affinity, thereby dramatically potentiating their proinflammatory properties in cellular and in vivo models. By using small interfering RNA knockdowns, pharmacologic inhibitors and extracellular domains of the receptors TLR2, TLR4, RAGE, and P2Y1 as competitive inhibitors, we demonstrate that polyP amplifies H4- and HMGB1-mediated inflammatory signaling in human umbilical vein endothelial cells specifically through interaction with the RAGE and P2Y1 receptors, thereby eliciting intracellular Ca(2+) release. Finally, we demonstrate that the natural anticoagulant protease, activated protein C, potently inhibits polyP-mediated proinflammatory effects of both nuclear proteins in cellular and in vivo systems.

Adenosine regulates the proinflammatory signaling function of thrombin in endothelial cells.

The plasma level of the regulatory metabolite adenosine increases during the activation of coagulation and inflammation. Here we investigated the effect of adenosine on modulation of thrombin‐mediated proinflammatory responses in HUVECs. We found that adenosine inhibits the barrier‐disruptive effect of thrombin in HUVECs by a concentration‐dependent manner. Analysis of cell surface expression of adenosine receptors revealed that A2A and A2B are expressed at the highest level among the four receptor subtypes (A2B > A2A > A1 > A3) on HUVECs. The barrier‐protective effect of adenosine in response to thrombin was recapitulated by the A2A specific agonist, CGS 21680, and abrogated both by the siRNA knockdown of the A2A receptor and by the A2A‐specific antagonists, ZM‐241385 and SCH‐58261. The thrombin‐induced RhoA activation and its membrane translocation were both inhibited by adenosine in a cAMP‐dependent manner, providing a molecular mechanism through which adenosine exerts a barrier‐protective function. Adenosine also inhibited thrombin‐mediated activation of NF‐κB and decreased adhesion of monocytic THP‐1 cells to stimulated HUVECs via down‐regulation of expression of cell surface adhesion molecules, VCAM‐1, ICAM‐1, and E‐selectin. Moreover, adenosine inhibited thrombin‐induced elevated expression of proinflammatory cytokines, IL‐6 and HMGB‐1; and chemokines, MCP‐1, CXCL‐1, and CXCL‐3. Taken together, these results suggest that adenosine may inhibit thrombin‐mediated proinflammatory signaling responses, thereby protecting the endothelium from injury during activation of coagulation and inflammation. J. Cell. Physiol. 229: 1292–1300, 2014.

Coating of electrospun poly(lactic-co-glycolic acid) nanofibers with willemite bioceramic: improvement of bone reconstruction in rat model

We have investigated the combination effects of bioceramics and poly(lactide‐co‐glycolide) (PLGA) on bone reconstruction in calvarial critical size defects using a rat model. Willemite (Zn2SiO4) ceramics were prepared and coated on the surface of electrospun fabricated scaffolds. After scaffolds and nanoparticles characterization, osteoconductivity of the construct was analyzed using digital mammography, multislice spiral‐computed tomography (MSCT) imaging, and histological analysis. Eight weeks after implantation, no sign of inflammation was observed at the site of the osseous defect. The results showed that the ceramics supported bone regeneration and highest bone reconstruction were observed in willemite‐coated PLGA. This suggests that electrospun PLGA nanofibers coated with BG are potential candidate implants for bone tissue engineering applications.

A comparison of pluripotency and differentiation status of four mesenchymal adult stem cells.

The self-renewal and differentiation status of a stem cell is very important in the applications concerning regenerative medicine. Proliferation capacity, differentiation potentials and epigenetic properties of stem cells differ between sources. Studies have shown the high potentials of stem cells in iPS reprogramming. To examine this; we have compared the stem-ness and differential potential of four adult stem cells from common sources. We show a correlation between pluripotency and differentiation status of each stem cell with available data on the reprogramming efficiency. Four human adult stem cells including, adipose tissue-mesenchymal stem cells (AT-MSC), bone marrow mesenchymal stem cells (BM-MSCs), nasal septum derived multipotent progenitors (NSP) and umbilical cord blood stem cells (USSCs) were isolated and characterized. The self- renewal and differentiation potentials of each stem cell were assessed. Stem-ness transcription factors and the propagation potentials of all cells were analyzed. Furthermore the differentiation potentials were evaluated using treatment with induction factors and specific MicroRNA profile. Real-time PCR results showed that our stem cells express innate differentiation factors, miR145 and Let7g, which regulate the stem-ness and also the reprogramming potentials of each stem cell. To complete our view, we compared the propagation and differentiation potentials by correlating the stem-ness gene expression with differentiation MicroRNAs, also the direct effect of these factors on reprogramming. Our results suggest that the potentials of adipose tissue stem cells for GMP (Good Manufacturing Practice) compliant starting material are adequate for clinical applications. Our results indicate a low risk potential for AT-MSCs as starting material for iPS production. Although let7g and mir145 are well known for their differentiation promoting effects, but function more of a fine tuning system between self-renewal and differentiation status.

Inorganic polyphosphate elicits pro-inflammatory responses through activation of the mammalian target of rapamycin complexes 1 and 2 in vascular endothelial cells.

Inorganic polyphosphate (polyP) elicits pro‐inflammatory signaling responses in endothelial cells through interaction with two receptors, RAGE and P2Y1. It is known that polyP activates mTOR signaling in breast cancer cells.

Inorganic polyphosphate promotes cyclin D1 synthesis through activation of mTOR/Wnt/β-catenin signaling in endothelial cells.

Essentials Polyphosphate (polyP) activates mTOR but its role in Wnt/β‐catenin signaling is not known. PolyP‐mediated cyclin D1 expression (β‐catenin target gene) was monitored in endothelial cells. PolyP and boiled platelet‐releasates induced the expression of cyclin D1 by similar mechanisms. PolyP establishes crosstalk between mTOR and Wnt/β‐catenin signaling in endothelial cells.

Isolation, characterization, and mesodermic differentiation of stem cells from adipose tissue of camel (Camelus dromedarius)

Adipose-derived stem cells are an attractive alternative as a source of stem cells that can easily be extracted from adipose tissue. Isolation, characterization, and multi-lineage differentiation of adipose-derived stem cells have been described for human and a number of other species. Here we aimed to isolate and characterize camel adipose-derived stromal cell frequency and growth characteristics and assess their adipogenic, osteogenic, and chondrogenic differentiation potential. Samples were obtained from five adult dromedary camels. Fat from abdominal deposits were obtained from each camel and adipose-derived stem cells were isolated by enzymatic digestion as previously reported elsewhere for adipose tissue. Cultures were kept until confluency and subsequently were subjected to differentiation protocols to evaluate adipogenic, osteogenic, and chondrogenic potential. The morphology of resultant camel adipose-derived stem cells appeared to be spindle-shaped fibroblastic morphology, and these cells retained their biological properties during in vitro expansion with no sign of abnormality in karyotype. Under inductive conditions, primary adipose-derived stem cells maintained their lineage differentiation potential into adipogenic, osteogenic, and chondrogenic lineages during subsequent passages. Our observation showed that like human lipoaspirate, camel adipose tissue also contain multi-potent cells and may represent an important stem cell source both for veterinary cell therapy and preclinical studies as well.

Novel approach to reduce postsurgical adhesions to a minimum: Administration of losartan plus atorvastatin intraperitoneally

BACKGROUND Intraperitoneal adhesions are the most important cause of intestinal obstruction, pelvic pain, and female infertility. MATERIALS AND METHODS Losartan (1, 5, and 10 mg/kg), atorvastatin (1, 20, and 30 mg/kg), losartan (10 mg/kg) plus atorvastatin (20 mg/kg), and sodium hyaluronate/carboxymethylcellulose (HA/CMC) were administered intraperitoneally in 90 male NMRI mice. After 7 d, the grade of adhesions was scored by two scaling methods and the concentrations of TGF-β1, tPA, and PAI-1 were also evaluated. RESULTS Simultaneous intraperitoneal administration of losartan and atorvastatin led to a much higher reduction of adhesions compared with that in the HA/CMC group (P < 0.05). When losartan plus atorvastatin was administered, significant changes in the serum concentration and mRNA expression, including the increase of tPA and the decrease of TGF-β1 and PAI-1, were observed compared with those in other groups. CONCLUSIONS Our findings suggest that the simultaneous application of losartan and atorvastatin leads to an enhanced reduction in adhesion bands more than that of HA/CMC treatment, compared with the control group, possibly through balancing the expression of TGF-β1, tPA, and PAI-1.

Intraperitoneal administration of activated protein C prevents postsurgical adhesion band formation

Postsurgical peritoneal adhesion bands are the most important causes of intestinal obstruction, pelvic pain, and female infertility. In this study, we used a mouse model of adhesion and compared the protective effect of activated protein C (APC) to that of the Food and Drug Administration-approved antiadhesion agent, sodium hyaluronate/carboxymethylcellulose (Seprafilm) by intraperitoneal administration of either APC or Seprafilm to experimental animals. Pathological adhesion bands were graded on day 7, and peritoneal fluid concentrations of tissue plasminogen activator (tPA), d-dimer, thrombin-antithrombin complex, and cytokines (IL-1β, IL-6, interferon-γ, tumor necrosis factor-α, transforming growth factor-β1) were evaluated. Inflammation scores were also measured based on histologic data obtained from peritoneal tissues. Relative to Seprafilm, intraperitoneal administration of human APC led to significantly higher reduction of postsurgical adhesion bands. Moreover, a markedly lower inflammation score was obtained in the adhesive tissues of the APC-treated group, which correlated with significantly reduced peritoneal concentrations of proinflammatory cytokines and an elevated tPA level. Further studies using variants of human APC with or without protease-activated receptor 1 (PAR1) signaling function and mutant mice deficient for either endothelial protein C receptor (EPCR) or PAR1 revealed that the EPCR-dependent signaling activity of APC is primarily responsible for its protective activity in this model. These results suggest APC has therapeutic potential for preventing postsurgical adhesion bands.