A Macroscopic Mathematical Model For Cell Migration Assays Using A Real-Time Cell Analysis

Experiments of cell migration and chemotaxis assays have been classically performed in the so-called Boyden Chambers. A recent technology, xCELLigence Real Time Cell Analysis, is now allowing to monitor the cell migration in real time. This technology measures impedance changes caused by the gradual increase of electrode surface occupation by cells during the course of time and provide a Cell Index which is proportional to cellular morphology, spreading, ruffling and adhesion quality as well as cell number. In this paper we propose a macroscopic mathematical model, based on \emph{advection-reaction-diffusion} partial differential equations, describing the cell migration assay using the real-time technology. We carried out numerical simulations to compare simulated model dynamics with data of observed biological experiments on three different cell lines and in two experimental settings: absence of chemotactic signals (basal migration) and presence of a chemoattractant. Overall we conclude that our minimal mathematical model is able to describe the phenomenon in the real time scale and numerical results show a good agreement with the experimental evidences

Improving the Therapeutic Potential of G-CSF through Compact Circular PEGylation Based on Orthogonal Conjugations

: In this study, a circular conjugate of granulocyte colony-stimulating factor (G-CSF) was prepared by conjugating the two end-chains of poly(ethylene glycol) (PEG) to two different sites of the protein. For the orthogonal conjugation, a heterobifunctional PEG chain was designed and synthesized, bearing the dipeptide ZGln-Gly (ZQG) at one end-chain, for transglutaminase (TGase) enzymatic selective conjugation at Lys41 of G-CSF, and an aldehyde group at the opposite end-chain, for N-terminal selective reductive alkylation of the protein. The cPEG-Nter/K41-G-CSF circular conjugate was characterized by physicochemical methods and compared with native G-CSF and the corresponding linear monoconjugates of G-CSF, PEG-Nter-G-CSF, and PEG-K41-G-CSF. The results demonstrated that the circular conjugate had improved physicochemical and thermal stability, prolonged pharmacokinetic interaction, and retained the biological activity of G-CSF. The PEGylation strategy employed in this study has potential applications in the design of novel protein-based therapeutics

Treatment with a Urokinase Receptor-derived Cyclized Peptide Improves Experimental Colitis by Preventing Monocyte Recruitment and Macrophage Polarization

Leukocyte migration across the blood barrier and into tissues represents a key process in the pathogenesis of inflammatory bowel diseases. The urokinase receptor (urokinase-type plasminogen activator receptor) is a master regulator of leukocyte recruitment. We recently found that cyclization of the urokinase-type plasminogen activator receptor-derived peptide Ser-Arg-Ser-Arg-Tyr [SRSRY] inhibits transendothelial migration of monocytes. Now, we have explored the effects of [SRSRY] administration during experimental colitis

Poly(L-glutamic acid)-co-poly(ethylene glycol) block copolymers for protein conjugation

Poly(L-glutamic acid)-co-poly(ethylene glycol) block copolymers (PLE-PEG) are here investigated as polymers for conjugation to therapeutic proteins such as granulocyte colony stimulating factor (G-CSF) and human growth hormone (hGH). PLE-PEG block copolymers are able to stabilize and protect proteins from degradation and to prolong their residence time in the blood stream, features that are made possible thanks to PEG's intrinsic properties and the simultaneous presence of the biodegradable anionic PLE moiety. When PLE-PEG copolymers are selectively tethered to the N-terminus of G-CSF and hGH, they yield homogeneous monoconjugates that preserve the protein's secondary structure. During the current study the pharmacokinetics of PLE10-PEG20k-G-CSF and PLE20-PEG20k-G-CSF derivatives and their ability to induce granulopoiesis were, respectively, assessed in Sprague-Dawley rats and in C57BL6 mice. Our results show that the bioavailability and bioactivity of the derivatives are comparable to or better than those of PEG20k-Nter-G-CSF (commercially known as Pegfilgrastim). The therapeutic effects of PLE10-PEG20k-hGH and PLE20-PEG20k-hGH derivatives tested in hypophysectomized rats demonstrate that the presence of a negatively charged PLE block enhances the biological properties of the conjugates additionally with respect to PEG20k-Nter-hGH

Role of Microenvironment on the Fate of Disseminating Cancer Stem Cells.

Disseminating Cancer Stem Cells (CSCs) initiate growth in specific niches of the host tissues, the cellular and molecular components of which sustain signaling pathways that support their survival, self-renewal dormancy and reactivation. In the metastatic niche, tumor cells may enter in a dormant state to survive and, consequently, the metastasis can remain latent for years. Despite the clinical importance of metastatic latency, little is known about what induces CSCs to enter a dormant state and what allows them to remain viable for years in this state. CSCs exhibit genetic, epigenetic and cellular adaptations that confer resistance to classical therapeutic approaches. The identification of potential CSC targets is complicated by the fact that CSCs may arise as a consequence of their relationship with the local microenvironment into the metastatic niches. Indeed, microenvironment modulates the capability of CSCs to evade the innate immune response and survive. Some new therapeutic options that include drugs targeting microenvironment components are achieving encouraging results in reducing the number of CSCs in tumors and/or overcoming their resistance in preclinical studies. This review will focus on specific CSC features with an emphasis on the role of tumor microenvironment in supporting metastatic dissemination of CSCs. In addition, it sheds light on potential microenvironment-targeted therapies aimed to counteract seeding and survival of CSCs in the metastatic niche

Sensitivity analysis for the parameters of the mathematical model.

<p>Sensitivity analysis for the parameters of the mathematical model.</p

Initial data and parameters of the mathematical model.

<p>Initial data and parameters of the mathematical model.</p

Numerical simulations on Sarc, HT1080, and A375 cell lines.

<p>For each cell line, panels on the left (a),(c),(e) show the basal migration in absence of chemoattractant. Numerical curves (blue) were compared with experimental data (red). Panels on the right (b),(d),(f) show the migration curves. The simulated values of Cell Index (blue) were compared with experiments (green). Here and in the following figures the experimental curves were obtained as the average of at least three experiments in quadruplicate (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0162553#pone.0162553.s002" target="_blank">S2 Fig</a>). About the MSE value on the Cell Index, defined in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0162553#pone.0162553.e022" target="_blank">Eq (15)</a>, we estimated, respectively, the following values: panels (a)-(b) MSE_basal = 0.0376 and MSE_migr = 0.0052; panels (c)-(d) MSE_basal = 0.0166 and MSE_migr = 0.0068; panels (e)-(f) MSE_basal = 0.0083 and MSE_migr = 0.0054.</p

Urokinase receptor derived peptides as potent inhibitors of the formyl peptide receptor type 1-triggered cell migration

The receptor for the urokinase-type plasminogen activator (uPAR) is a widely recognized master regulator of cell migration. We and others have previously documented that the uPAR(84–95) sequence, interacts with the formyl peptide receptors (FPR)s, henceforth inducing cell migration of several cell lines, including leukocytes, and the synthetic shorter peptide (Ser88-Arg-Ser-Arg-Tyr92, SRSRY) retains chemotactic activity in vitro and in vivo. Recently, we have developed the head-to-tail cyclic analog [SRSRY], a new potent and stable inhibitor of monocyte trafficking. This prompted us to develop novel cyclic and linear analogs of [SRSRY] with the aim to broaden the knowledge about structure-activity relationships of peptide [SRSRY]. Herein we report their synthesis, effects on cell migration, conformational and docking analyses which served to envisage a new pharmacophore model for inhibitors of FPR1-triggered cell migration

Schematic representation of a well of the CIM-plate.

<p>An upper and a lower chamber are separated by a permeable membrane Γ_M. In the migration assay in presence of chemoattractant, cells are placed in the upper chamber, and the chemoattractant is added in the lower chamber (directional migration). When measuring the basal migration experiment the well contains only cells (in the upper chamber) and a serum-free medium. In the mathematical formulation the spatial <i>x</i>−<i>axis</i> is oriented from the top to the bottom.</p