Early in-situ cellularization of a supramolecular vascular graft is modified by synthetic stromal cell-derived factor-1α derived peptides
Introduction
Replacement of small diameter blood vessels relies mainly on autologous tissue, which is often limited by availability and requires invasive harvesting. Common non-living prostheses for vascular structures have considerable drawbacks such as high risk of occlusion, lack of growth potential, the consequent need for re-operation in pediatric patients, and life-long anti-coagulation therapy [1]. In an in-situ tissue engineering approach, synthetic scaffolds are implanted that provide the necessary mechanical support. Ideally, scaffold material will contain bioactive molecules capable of instructing cells of the recipient to migrate into the graft and stimulate the development of living, growing tissue [2]. Molecules involved in cellular adhesion have largely been the focus to be introduced in synthetic materials [3]. Chemokines play a considerable role in the process of tissue repair by attracting progenitor cells but also by modulating the inflammatory environment. Therefore, immobilization of chemokines on synthetic grafts may simultaneously allow for both specific cell retention and subsequent stimulation of cellular development [2]. Stromal cell derived factor 1 alpha (SDF1α) is a potent chemoattractant of lymphocytes [4], monocytes and progenitor cells but not neutrophils [5]. It is important for the homing of bone-marrow resident stem cells [6], and plays a central role in tissue repair signaling [5]. Importantly, following implantation the systemic response to a cell-free vascular graft material involves the influx of immune cells. The nature and amount of these cells can be influenced by SDF1α [7]. Short SDF1α-peptides that are homologous to the receptor-activating domain of the full protein, have been shown to improve damage repair after local delivery in ischemic tissue [8]. This indicates that short peptide sequences, which are synthetically more accessible compared to full-length proteins, are capable of retaining specific SDF1α activity. Maintaining a stable local gradient of SDF1α and avoiding a burst release of bioactive molecules after implantation has been shown to further improve the retention of progenitor cells under fluid flow conditions [9]. In addition to inducing cellular mobilization as a soluble factor, SDF1a is an important anchoring molecule for progenitor cells in bone marrow stroma [10] as well as a homing beacon bound to the ECM in the vicinity of tissue damage, guiding the migration of cells towards the site of repair [11]. Therefore an approach to anchor the SDF1α protein to a scaffold material may be advantageous for biological signaling at the site of graft implantation.
In this study we apply a synthetic cell-free scaffold based on the supramolecular modification of poly(l-lactic acid caprolactone) (PLLCL) functionalized with quadruple hydrogen bonding ureido-pyrimidinone (UPy) units [12], with SDF1α-derived peptide sequences also modified with these UPy-moieties, in order to facilitate the early cellularization of a vascular graft [2]. The base material consists of PLLCL prepolymers modified with UPy-moieties in the main chain yielding a chain-extended UPy-PLLCL (or CE-UPy-PLLCL) polymer (Fig. 1) [13]. To prevent rapid proteolytic degradation of the SDF1α-derived peptides, we abolished the cleavage sites for the enzymes MMP2 and CD26, which are capable of abrogating the SDF1α signal and are abundant in an inflammatory environment [8], [14]. The second valine in the natural sequence was substituted with a serine residue, leading to two peptide sequences: SKPVSLSYR and SKPVVLSYR, i.e. the proteolytically resistant and non-resistant peptides, respectively (after UPy-modification UPy-SDF1α(R) and UPy-SDF1α(NR), respectively). The material was processed into fibrous scaffolds by electrospinning. Using a previously developed mesofluidic device [15] applying a physiological pulsatile fluid flow of medium-suspended human peripheral blood mononuclear cells (PBMCs) the homing of cells into the scaffolds functionalized with short SDF1α peptides was analyzed. As a proof-of-concept to investigate the in vivo specific recruitment of circulating cells, we implanted electrospun tubular scaffolds in a abdominal aorta interposition graft rat model and analyzed the cellular influx after 24 h and 7 days.
Section snippets
Synthesis of the SDF1α peptides
The synthesis of the investigated peptides is described in the supplemental files (See supplemental Materials & Methods).
Synthesis of CE-UPy-PLLCLa
The CE-UPy-PLLCL polymer was obtained using the same procedure as described for polymer 2 described in Ref. [13] (chain-extended UPy-poly[2-methyl–1,3-propylene adipate) in which the poly[2-methyl–1,3-propylene adipate diol is replaced with poly(l-lactic acid caprolactone) diol (purchased from SyMO-Chem BV) with a Mn of 1 kDa. The CE-UPy-PLLCL polymer was obtained as an
Synthetic SDF1α-derived peptides are biologically active through CXCR4 and are resistant to proteolytic degradation by MMP2
The ability of the SDF1α-derived peptides to induce receptor-mediated migration was analyzed to confirm biological activity though the SDF1α-CXCR4 axis. In a Boyden chamber migration assay both SDF1α(R) and SDF1α(NR) peptides induced significant migration of PBMCs compared to the non-peptide control condition and to a similar degree to full-length SDF1α. Pre-incubation of PBMCs with the CXCR4-specific antagonist AMD-3100 significantly reduced the number of migrating cells (Fig. 2A). This
Discussion
Previous efforts to use biofunctionalized synthetic materials for vascular grafting have mostly focused on ECM derived peptides such as RGD to enhance cellular adhesion [17]. Considering their ability to simultaneously attract and stimulate targeted cell populations chemokines may provide more specific biological activity. We report, for the first time, that the supramolecular bioactivation of a fully synthetic material using short peptides based on the chemokine SDF1α can attract and stimulate
Acknowledgments
This research forms part of the Project P1.01 iValve of the research program of the BioMedical Materials institute, co-funded by the Dutch Ministry of Economic Affairs.
The financial contribution of the Nederlandse Hartstichting is gratefully acknowledged.
Part of this research is funded by the Ministry of Education, Culture and Science (Gravity program 024.001.035), the Netherlands Organisation for Scientific Research (NWO), the European Research Council (FP7/2007–2013), ERC Grant Agreement
References (33)
- et al.
Luminal surface engineering, “micro and nanopatterning”: potential for self endothelialising vascular grafts?
Eur. J. Vasc. Endovasc. Surg.
(2014) - et al.
Chemokine stromal cell-derived factor-1alpha modulates VLA-4 integrin-dependent adhesion to fibronectin and VCAM-1 on bone marrow hematopoietic progenitor cells
Exp. Hematol.
(2001) - et al.
The effect of stromal cell-derived factor-1α/heparin coating of biodegradable vascular grafts on the recruitment of both endothelial and smooth muscle progenitor cells for accelerated regeneration
Biomaterials
(2012) - et al.
Maintenance of the hematopoietic stem cell pool by CXCL12-CXCR4 chemokine signaling in bone marrow stromal cell niches
Immunity
(2006) - et al.
Electrospun bilayer fibrous scaffolds for enhanced cell infiltration and vascularization in vivo
Acta Biomater.
(2015) - et al.
Preserved bioactivity and tunable release of a SDF1-GPVI bi-specific protein using photo-crosslinked PEGda hydrogels
Biomaterials
(2014) - et al.
Immune responses to implants – a review of the implications for the design of immunomodulatory biomaterials
Biomaterials
(2011) - et al.
Macrophage phenotype as a predictor of constructive remodeling following the implantation of biologically derived surgical mesh materials
Acta Biomater.
(2012) - et al.
The effect of thick fibers and large pores of electrospun poly(ε-caprolactone) vascular grafts on macrophage polarization and arterial regeneration
Biomaterials
(2014) - et al.
The chemokine CXCL12 regulates monocyte-macrophage differentiation and RUNX3 expression
Blood
(2011)
DPP-4 inhibition ameliorates atherosclerosis by priming monocytes into M2 macrophages
Int. J. Cardiol.
Synergy between CD26/DPP-IV inhibition and G-CSF improves cardiac function after acute myocardial infarction
Cell Stem Cell
Matrix metalloproteinase activity inactivates the CXC chemokine stromal cell-derived factor-1
J. Biol. Chem.
Concise review: tissue-engineered vascular grafts for cardiac surgery: past, present, and future
Stem Cells Transl. Med.
Combining tissue repair and tissue engineering; bioactivating implantable cell-free vascular scaffolds
Heart
CXCL12 mediates immunosuppression in the lymphoma microenvironment after allogeneic transplantation of hematopoietic cells
Cancer Res.
Cited by (84)
Translational tissue-engineered vascular grafts: From bench to bedside
2023, BiomaterialsSupramolecular polymer materials based on ureidopyrimidinone quadruple hydrogen bonding units
2023, Progress in Polymer ScienceThermosensitive hydrogel for cartilage regeneration via synergistic delivery of SDF-1α like polypeptides and kartogenin
2023, Carbohydrate PolymersCitation Excerpt :Stromal-derived factor-1α (SDF-1α) is a chemokine that plays an important role in stem-cell homing for tissue repair (Chen et al., 2015). However, although SDF-1α has been widely used for stem-cell recruitment, it is costly and difficult to store and transport (Muylaert et al., 2016). SDF-1α-like polypeptide (SDFP) is a short chemotactic peptide chain (sequence: SKPVVLSYR) of SDF-1α that has the same receptor activation domain as the complete protein.
Combined effect of SDF-1 peptide and angiogenic cues in co-axial PLGA/gelatin fibers for cutaneous wound healing in diabetic rats
2023, Colloids and Surfaces B: BiointerfacesPeptides-tethered vascular grafts enable blood vessel regeneration via endogenous cell recruitment and neovascularization
2023, Composites Part B: EngineeringSupramolecular polymer materials bring restorative heart valve therapy to patients
2022, Materials Today
- 1
These authors contributed equally to this work.