Biomedical subjects

Lorenzo Soletti

Publications and source records attributed to Lorenzo Soletti.

3 recordsLinked to original sources

PubMed2007

Mechanical stimulation induces morphological and phenotypic changes in bone marrow-derived progenitor cells within a three-dimensional fibrin matrix.

One of the major limitations in tissue engineering is cell sourcing. Multipotent progenitor cells appear to have many promising features for that purpose. Mechanical stimulation is known to play an important role in determining cell phenotype. The aim of this work was to investigate the effects of cyclic stretch on rat bone marrow derived progenitor cell (BMPC) morphology and smooth muscle-directed differentiation within a three-dimensional fibrin matrix. BMPCs were suspended in a fibrin gel, pipetted into the trough of Flexcell Tissue-Train plates, and stimulated with 10% longitudinal cyclic stretch at 1 Hz for 6 days. Unconstrained (stress- and strain-free) and static anchored (constrained but not stretched) samples were used as controls. Stress filament area per cell was increased in the stretched samples compared to static anchored and free-float controls. Cells in the free float controls were randomly aligned, while they aligned parallel to the direction of the stress or strain in the other groups. Immunofluorescence suggested an increased expression of smooth muscle markers (smooth muscle alpha actin and h1-calponin) in both stretched and constrained control samples, but not in unconstrained controls. Qualitative assessment suggested that collagen production was increased in both mechanically stimulated samples. Proliferation was inhibited in stretched samples compared to the constrained controls. This work suggests an ability of rat BMPCs to differentiate toward a smooth-muscle-cell-like lineage when exposed to biomechanical stimulation in a three-dimensional model. The observation that the constrained samples induced changes in BMPCs suggests that stress alone may be stimulatory, but addition of cyclic stretch appears to augment the responses.

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PubMed2007

A new experimental system for the extended application of cyclic hydrostatic pressure to cell culture.

Mechanical forces have been shown to be important stimuli for the determination and maintenance of cellular phenotype and function. Many cells are constantly exposed in vivo to cyclic pressure, shear stress, and/or strain. Therefore, the ability to study the effects of these stimuli in vitro is important for understanding how they contribute to both normal and pathologic states. While there exist commercial as well as custom-built devices for the extended application of cyclic strain and shear stress, very few cyclic pressure systems have been reported to apply stimulation longer than 48 h. However, pertinent responses of cells to mechanical stimulation may occur later than this. To address this limitation, we have designed a new cyclic hydrostatic pressure system based upon the following design variables: minimal size, stability of pressure and humidity, maximal accessibility, and versatility. Computational fluid dynamics (CFD) was utilized to predict the pressure and potential shear stress within the chamber during the first half of a 1.0 Hz duty cycle. To biologically validate our system, we tested the response of bone marrow progenitor cells (BMPCs) from Sprague Dawley rats to a cyclic pressure stimulation of 120/80 mm Hg, 1.0 Hz for 7 days. Cellular morphology was measured using Scion Image, and cellular proliferation was measured by counting nuclei in ten fields of view. CFD results showed a constant pressure across the length of the chamber and no shear stress developed at the base of the chamber where the cells are cultured. BMPCs from Sprague Dawley rats demonstrated a significant change in morphology versus controls by reducing their size and adopting a more rounded morphology. Furthermore, these cells increased their proliferation under cyclic hydrostatic pressure. We have demonstrated that our system imparts a single mechanical stimulus of cyclic hydrostatic pressure and is capable of at least 7 days of continuous operation without affecting cellular viability. Furthermore, we have shown for the first time that BMPCs respond to cyclic hydrostatic pressure by alterations in morphology and increased proliferation.

Animals↗

PubMed2006

A seeding device for tissue engineered tubular structures.

One of the challenges in the tissue engineering of tubular tissues and organs is the efficient seeding of porous scaffolds with the desired cell type and density in a short period of time, without affecting cell viability. Though different seeding techniques have been investigated, a fast, reproducible, and efficient bulk seeding method with uniform cellular distribution has yet to be reported. In this paper, a novel seeding device utilizing the synergistic effects of vacuum, centrifugal force and flow has been developed and analyzed. The device allows porous tubular scaffolds to be uniformly bulk seeded as well as luminally surface-seeded with cells. Porous tubular polymer scaffolds were bulk and surface-seeded with cell suspensions, and cell viability and seeding efficiency were subsequently assessed. A rigorous quantitative analysis of shear stresses acting on the cells during the seeding process, and of cell location within the scaffolds following seeding was also performed. Our results showed that the scaffolds were uniformly seeded along the longitudinal and circumferential directions within the tube wall without affecting cell viability or exposing them to excessive shear stresses.

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