Abstract
Electrospun poly(lactic-co-glycolic acid) (PLGA) scaffolds with highly aligned fibers (ha-PLGA) represent promising materials in the field of tendon tissue engineering (TE) due to their characteristics in mimicking fibrous extracellular matrix (ECM) of tendon native tissue. Among these properties, scaffold biodegradability must be controlled allowing its replacement by a neo-formed native tendon tissue in a controlled manner. In this study, ha-PLGA were subjected to hydrolytic degradation up to 20 weeks, under di-H2O and PBS conditions according to ISO 10993-13:2010. These were then characterized for their physical, morphological, and mechanical features. In vitro cytotoxicity tests were conducted on ovine amniotic epithelial stem cells (oAECs), up to 7 days, to assess the effect of non-buffered and buffered PLGA by-products at different concentrations on cell viability and their stimuli on oAECs’ immunomodulatory properties. The ha-PLGA scaffolds degraded slowly as evidenced by a slight decrease in mass loss (14%) and average molecular weight (35%), with estimated degradation half-time of about 40 weeks under di-H2O. The ultrastructure morphology of the scaffolds showed no significant fiber degradation even after 20 weeks, but alteration of fiber alignment was already evident at week 1. Moreover, mechanical properties decreased throughout the degradation times under wet as well as dry PBS conditions. The influence of acid degradation media on oAECs was dose-dependent, with a considerable effect at 7 days’ culture point. This effect was notably reduced by using buffered media. To a certain level, cells were able to compensate the generated inflammation-like microenvironment by upregulating IL-10 gene expression and favoring an anti-inflammatory rather than pro-inflammatory response. These in vitro results are essential to better understand the degradation behavior of ha-PLGA in vivo and the effect of their degradation by-products on affecting cell performance. Indeed, buffering the degradation milieu could represent a promising strategy to balance scaffold degradation. These findings give good hope with reference to the in vivo condition characterized by physiological buffering systems.
Highlights
Ascaffold implanted in the body should provide sufficient mechanical properties and structural integrity to support the loads applied during the early stage of reparation until the engineered cells or autologous cells, attracted by the neighboring tissues, are able to synthesize sufficient extracellular matrix (ECM) [1,2]
The variation of fiber diameter size and surface morphology of the ha-poly(lactic-co-glycolic acid) (PLGA) scaffolds subjected to the in vitro hydrolytic degradation procedure was evaluated using Scanning Electron Microscopy (SEM) before and after 1, 10, and 20 weeks of degradation under di-H2 O and phosphate buffer saline solution (PBS) conditions (Figure 1)
The obtained results showed that the fabricated ha-PLGA constructs exhibited a slow degradation profile with a degradation half-time of about 40 weeks under di-H2 O, confirmed by a slight decrease in the mass loss and average molecular weight with a faster kinetic under di-H2 O compared to PBS conditions that could be related to different factors characterizing the studied material
Summary
Ascaffold implanted in the body should provide sufficient mechanical properties and structural integrity to support the loads applied during the early stage of reparation until the engineered cells or autologous cells, attracted by the neighboring tissues, are able to synthesize sufficient ECM [1,2]. PLA and PCL are two biocompatible polymers, they are characterized by high hydrophobic properties that decreased cell adhesion due to the lack of cell recognition sites on their surfaces [9,15,16]. This might lead to a long in vivo degradation rate, which restricts their target applications depending on the regeneration time of the damaged tissue [9,15,16]. PLA is a crystalline polymer that degrades in vivo in degradable fragments leading to considerable inflammatory response in the body [16]
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