Growth factor release from a chemically modified elastomeric poly(1,8‐octanediol‐co‐citrate) thin film promotes angiogenesisin vivo

Abstract

The ultimate success of in vivo organ formation utilizing ex vivo expanded "starter" tissues relies heavily upon the level of vascularization provided by either endogenous or artificial induction of angiogenic or vasculogenic events. To facilitate proangiogenic outcomes and promote tissue growth, an elastomeric scaffold previously shown to be instrumental in the urinary bladder regenerative process was modified to release proangiogenic growth factors. Carboxylic acid groups on poly(1,8-octanediol-co-citrate) films (POCfs) were modified with heparan sulfate creating a heparan binding POCf (HBPOCf). Release of proangiogenic growth factors vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF2), and insulin-like growth factor 1 (IGF-1) from HBPOCfs demonstrated an approximate threefold increase over controls during a 30-day time course in vitro. Atomic force microscopy demonstrated significant topological differences between films. Subcutaneous implantation of POCf alone, HBPOCf, POCf-VEGF, and HBPOCf-VEGF within the dorsa of nude rats yielded increased vascular growth in HBPOCf-VEGF constructs. Vessel quantification studies revealed that POCfs alone contained 41.1 ± 4.1 vessels/mm², while HBPOCf, POCf-VEGF, and HBPOCF-VEGF contained 41.7 ± 2.6, 76.3 ± 9.4, and 167.72 ± 15.3 vessels/mm², respectively. Presence of increased vessel growth was demonstrated by CD31 and vWF immunostaining in HBPOCf-VEGF implanted areas. Data demonstrate that elastomeric POCfs can be chemically modified and possess the ability to promote angiogenesis in vivo.

Annular puncture with tumor necrosis factor-alpha injection enhances painful behavior with disc degeneration in vivo

“…The findings revealed that the level of structural disc degeneration is most strongly related to the amount of disc tissue disruptions due to the puncture rather than the injectate. The concentrations of TNFα and NGF/VEGF were adopted from previous in vivo or in vitro studies [37–40], and were sufficient to induce observable changes in pain behavior in this study. The deeper annular puncture induced both NP and AF injury with no herniation observed in all injected discs by MRI or histology, although the full AF depth injury could result in some NP exposure in the anterior region.…”

“…All intradiscal injections used a 26-gauge needle at a depth of 1.5 mm (shallow) or 3 mm (deep) as guided by a needle stopper. A total of 2.5 μL of PBS, TNFα (0.25 ng in 2.5 uL) [37], or NGF/VEGF (50 ng/250 ng in 2.5 uL) were slowly injected into each disc using a calibrated microliter syringe (Hamilton Company, Reno, NV, USA) with doses taken from the literature [38–40]. The volume and method of intradiscal injection were determined from thorough preliminary studies on motion segments of live animals that titrated the injection volume down to 2.5 μL and demonstrated that there was no fluid leakage or nerve root irritation were visible.…”

Citrate-Based Biomaterials and Their Applications in Regenerative Engineering

“…After 10 weeks of implantation to augment partially cystectomized nude rats, POC-augmented bladders seeded with mesenchymal stem and urothelial cells displayed normal tissue architecture and 1.75 times greater muscle/collagen ratios than did films seeded with smooth muscle and urothelial cells, thus demonstrating their potential to support partial bladder regeneration in vivo. To promote angiogenesis and improve bladder regeneration, the carboxylic acid groups of POC were modified with heparan sulfate to create heparan-binding domains for the subsequent conjugation of proangiogenic growth factors (126). A threefold increase in release of vascular endothelial growth factor, fibroblast growth factor 2, and insulin-like growth factor 1 was observed for heparan-modified POC versus controls during a 30-day time course in vitro.…”

Inosculation of Blood Vessels Allows Early Perfusion and Vitality of Bladder Grafts—Implications for Bioengineered Bladder Wall

“…Bioengineering of blood vessels has been investigated for nonbladder tissues, while cells (mesenchymal stem cells, endothelial cells) and growth factors have been used to enhance vascular growth into bladder grafts. [22][23][24][25][26][27][28] The results of this study suggest that pre-existing vessels in bioengineered grafts might facilitate early perfusion and enhance graft regeneration and function in the long term. As such, the engineering of graft blood vessels and the promotion of inosculation between host and donor vessels, either endogenous or engineered, might promote graft success, thereby potentiating the use of bioengineered bladder tissue for transplantation.…”