RESUMO
The ultimate goal of this research is to develop an injectable cell-scaffold system capable of permitting adipogenesis to abrogate soft tissue deficiencies resulting from trauma, tumor resection, and congenital abnormalities. The present work compares the efficacy of photopolymerizable poly(ethylene glycol) and specific derivatives as a scaffold for preadipocyte (adipocyte precursor cell) viability, adhesion, and proliferation. Four variations of a poly(ethylene glycol) scaffold are prepared and examined. The first scaffold consists of poly(ethylene glycol) diacrylate, which is not susceptible to hydrolysis or enzymatic degradation. Preadipocyte death is observed over 1 week in this hydrogel configuration. Adhesion sites, specifically the laminin-binding peptide sequence YIGSR, were incorporated into the second scaffold to promote cellular adhesion as a prerequisite for preadipocyte proliferation. Preadipocytes remain viable in this scaffold system, but do not proliferate in this nondegradable hydrogel. The third scaffold system studied consists of poly(ethylene glycol) modified with the peptide sequence LGPA to permit polymer degradation by cell-secreted collagenase. No adhesion peptide is incorporated into this scaffold system. Cellular proliferation is initially observed, followed by cell death. The previous three scaffold configurations do not permit preadipocyte adhesion and proliferation. In contrast, the fourth system studied, poly(ethylene glycol) modified to incorporate both LGPA and YIGSR, permits preadipocyte adherence and proliferation subsequent to polymer degradation. Our results indicate that a scaffold system containing specific degradation sites and cell adhesion ligands permits cells to adhere and proliferate, thus providing a potential cell-scaffold system for adipogenesis.
Assuntos
Adipócitos , Materiais Biocompatíveis/química , Proliferação de Células , Hidrogéis/química , Polietilenoglicóis/química , Células-Tronco , Engenharia Tecidual/métodos , Acrilatos/química , Adipócitos/citologia , Adipócitos/metabolismo , Adipócitos/fisiologia , Animais , Adesão Celular , Técnicas de Cultura de Células , Sobrevivência Celular , Células Cultivadas , DNA/análise , DNA/metabolismo , Masculino , Peso Molecular , Ratos , Ratos Endogâmicos Lew , Fatores de TempoRESUMO
The viscosity and elastic and viscous moduli of poly(ethylene glycol) diacrylate (PEGDA) hydrogels and human abdominal adipose tissue are measured as a function of shear rate and frequency. Results indicate that both materials exhibit shear thinning and are viscoelastic in nature. Rheological tests suggest that the hydrogels become firmer as strain and frequency increase. Adipose tissue, however, begins to fail at higher strains and frequencies. This behavior is confirmed by measuring the complex modulus of both materials as a function of strain. Recovery properties are also measured for each material as a function of deformation. Although PEGDA hydrogels are able to recover up to 78% of their original height after 15% deformation, adipose tissue is not able to recover over the range of deformations tested. The frequencies and strains over which the tests are conducted are those physiologically experienced by the human body. The hydrogels are able to withstand this range of forces and, hence, are appropriate for use as a soft tissue filler material. In addition, the hydrogels swell 38.1% +/- 0.9% independent of surface area. The complex modulus of hydrogels of varying polymer concentrations is also measured as a function of strain to determine the effects of changing polymer content. These results indicate that as polymer content increases, the hydrogels become firmer due to the higher number of polymer chains and behave more elastically.
