Bioengineered 3D ovarian model for long-term multiple development of preantral follicle: bridging the gap for poly(ε-caprolactone) (PCL)-based scaffold reproductive applications

BACKGROUND

Assisted Reproductive Technologies (ARTs) have been validated in human and animal to solve reproductive problems such as infertility, aging, genetic selection/amplification and diseases. The persistent gap in ART biomedical applications lies in recapitulating the early stage of ovarian folliculogenesis, thus providing protocols to drive the large reserve of immature follicles towards the gonadotropin-dependent phase. Tissue engineering is becoming a concrete solution to potentially recapitulate ovarian structure, mostly relying on the use of autologous early follicles on natural or synthetic scaffolds. Based on these premises, the present study has been designed to validate the use of the ovarian bioinspired patterned electrospun fibrous scaffolds fabricated with poly(ε-caprolactone) (PCL) for multiple preantral (PA) follicle development.

METHODS

PA follicles isolated from lamb ovaries were cultured on PCL scaffold adopting a validated single-follicle protocol (Ctrl) or simulating a multiple-follicle condition by reproducing an artificial ovary engrafted with 5 or 10 PA (AO5PA and AO10PA). The incubations were protracted for 14 and 18 days before assessing scaffold-based microenvironment suitability to assist in vitro folliculogenesis (ivF) and oogenesis at morphological and functional level.

RESULTS

The ivF outcomes demonstrated that PCL-scaffolds generate an appropriate biomimetic ovarian microenvironment supporting the transition of multiple PA follicles towards early antral (EA) stage by supporting follicle growth and steroidogenic activation. PCL-multiple bioengineering ivF (AO10PA) performed in long term generated, in addition, the greatest percentage of highly specialized gametes by enhancing meiotic competence, large chromatin remodeling and parthenogenetic developmental competence.

CONCLUSIONS

The study showcased the proof of concept for a next-generation ART use of PCL-patterned scaffold aimed to generate transplantable artificial ovary engrafted with autologous early-stage follicles or to advance ivF technologies holding a 3D bioinspired matrix promoting a physiological long-term multiple PA follicle protocol.

Micro- and Nanostructured Fibrous Composites via Electro-Fluid Dynamics: Design and Applications for Brain

The brain consists of an interconnected network of neurons tightly packed in the extracellular matrix (ECM) to form complex and heterogeneous composite tissue. According to recent biomimicry approaches that consider biological features as active components of biomaterials, designing a highly reproducible microenvironment for brain cells can represent a key tool for tissue repair and regeneration. Indeed, this is crucial to support cell growth, mitigate inflammation phenomena and provide adequate structural properties needed to support the damaged tissue, corroborating the activity of the vascular network and ultimately the functionality of neurons. In this context, electro-fluid dynamic techniques (EFDTs), i.e., electrospinning, electrospraying and related techniques, offer the opportunity to engineer a wide variety of composite substrates by integrating fibers, particles, and hydrogels at different scales-from several hundred microns down to tens of nanometers-for the generation of countless patterns of physical and biochemical cues suitable for influencing the in vitro response of coexistent brain cell populations mediated by the surrounding microenvironment. In this review, an overview of the different technological approaches-based on EFDTs-for engineering fibrous and/or particle-loaded composite substrates will be proposed. The second section of this review will primarily focus on describing current and future approaches to the use of composites for brain applications, ranging from therapeutic to diagnostic/theranostic use and from repair to regeneration, with the ultimate goal of providing insightful information to guide future research efforts toward the development of more efficient and reliable solutions.

Magnetic Nanofibrous Hydrogels for Dynamic Control of Stem Cell Differentiation

The extracellular matrix in tissue consists of complex heterogeneous soft materials with hierarchical structure and dynamic mechanical properties dictating cell and tissue level function. In many natural matrices, there are nanofibrous structures that serve to guide cell activity and dictate the form and function of tissue. Synthetic hydrogels with integrated nanofibers can mimic the structural properties of native tissue; however, model systems with dynamic mechanical properties remain elusive. Here we demonstrate modular nanofibrous hydrogels that can be reversibly stiffened in response to applied magnetic fields. Iron oxide nanoparticles were incorporated into gelatin nanofibers through electrospinning, followed by chemical stabilization and fragmentation. These magnetoactive nanofibers can be mixed with virtually any hydrogel material and reversibly stiffen the matrix at a low fiber content (≤3%). In contrast to previous work, where a large quantity of magnetic material disallowed cell encapsulation, the low nanofiber content allows matrix stiffening with cells in 3D. Using adipose derived stem cells, we show how nanofibrous matrices are beneficial for both osteogenesis and adipogenesis, where stiffening the hydrogel with applied magnetic fields enhances osteogenesis while discouraging adipogenesis. Skeletal myoblast progenitors were used as a model of tissue morphogenesis with matrix stiffening augmenting myogenesis and multinucleated myotube formation. The ability to reversibly stiffen fibrous hydrogels through magnetic stimulation provides a useful tool for studying nanotopography and dynamic mechanics in cell culture, with a scope for stimuli responsive materials for tissue engineering.

When Electrospun Fiber Support Matters: In Vitro Ovine Long-Term Folliculogenesis on Poly (Epsilon Caprolactone) (PCL)-Patterned Fibers

Current assisted reproduction technologies (ART) are insufficient to cover the slice of the population needing to restore fertility, as well as to amplify the reproductive performance of domestic animals or endangered species. The design of dedicated reproductive scaffolds has opened the possibility to better recapitulate the reproductive 3D ovarian environment, thus potentially innovating in vitro folliculogenesis (ivF) techniques. To this aim, the present research has been designed to compare ovine preantral follicles in vitro culture on poly(epsilon-caprolactone) (PCL)-based electrospun scaffolds designed with different topology (Random vs. Patterned fibers) with a previously validated system. The ivF performances were assessed after 14 days under 3D-oil, Two-Step (7 days in 3D-oil and on scaffold), or One-Step PCL protocols (14 days on PCL-scaffold) by assessing morphological and functional outcomes. The results show that Two- and One-Step PCL ivF protocols, when performed on patterned scaffolds, were both able to support follicle growth, antrum formation, and the upregulation of follicle marker genes leading to a greater oocyte meiotic competence than in the 3D-oil system. In conclusion, the One-Step approach could be proposed as a practical and valid strategy to support a synergic follicle-oocyte in vitro development, providing an innovative tool to enhance the availability of matured gametes on an individual basis for ART purposes.

Marrying the incompatible for better: Incorporation of hydrophobic payloads in superhydrophilic hydrogels

HYPOTHESIS

The entrapment of lyophobic in superhydrophilic hydrogels is challenging because of the intrinsic incompatibility between hydrophobic and hydrophilic molecules. To achieve such entrapment without affecting the hydrogel's formation, the electrospinning of nanodroplets or nanoparticles with a water-soluble polymer could reduce the incompatibility through the reduction of interfacial tension and the formation of a barrier film preventing coalescence or aggregation.

EXPERIMENTS

Nanodroplets or nanoparticles dispersion are electrospun in the presence of a hydrophilic polymer in hydrogel precursors. The dissolution of the hydrophilic nanofibers during electrospinning allows a redispersion of emulsion droplets and nanoparticles in the hydrogel's matrix.

FINDINGS

Superhydrophilic hydrogels with well-distributed hydrophobic nanodroplets or nanoparticles are obtained without detrimentally imparting the viscosity of hydrogel's precursors and the mechanical properties of the hydrogels. Compared with the incorporation of droplets without electrospinning, higher loadings of hydrophobic payload are achieved without premature leakage. This concept can be used to entrap hydrophobic agrochemicals, drugs, or antibacterial agents in simple hydrogels formulation.

3D Printed Multiphasic Scaffolds for Osteochondral Repair: Challenges and Opportunities

Osteochondral (OC) defects are debilitating joint injuries characterized by the loss of full thickness articular cartilage along with the underlying calcified cartilage through to the subchondral bone. While current surgical treatments can provide some relief from pain, none can fully repair all the components of the OC unit and restore its native function. Engineering OC tissue is challenging due to the presence of the three distinct tissue regions. Recent advances in additive manufacturing provide unprecedented control over the internal microstructure of bioscaffolds, the patterning of growth factors and the encapsulation of potentially regenerative cells. These developments are ushering in a new paradigm of 'multiphasic' scaffold designs in which the optimal micro-environment for each tissue region is individually crafted. Although the adoption of these techniques provides new opportunities in OC research, it also introduces challenges, such as creating tissue interfaces, integrating multiple fabrication techniques and co-culturing different cells within the same construct. This review captures the considerations and capabilities in developing 3D printed OC scaffolds, including materials, fabrication techniques, mechanical function, biological components and design.

Engineering a Highly Biomimetic Chitosan-Based Cartilage Scaffold by Using Short Fibers and a Cartilage-Decellularized Matrix

Engineering scaffolds with structurally and biochemically biomimicking cues is essential for the success of tissue-engineered cartilage. Chitosan (CS)-based scaffolds have been widely used for cartilage regeneration due to its chemostructural similarity to the glycosaminoglycans (GAGs) found in the extracellular matrix of cartilage. However, the weak mechanical properties and inadequate chondroinduction capacity of CS give rise to compromised efficacy of cartilage regeneration. In this study, we incorporated short fiber segments, processed from electrospun aligned poly(lactic-co-glycolic acid) (PLGA) fiber arrays, into a citric acid-modified chitosan (CC) hydrogel scaffold for mechanical strengthening and structural biomimicking and meanwhile introduced cartilage-decellularized matrix (CDM) for biochemical signaling to promote the chondroinduction activity. We found that the incorporation of PLGA short fibers and CDM remarkably strengthened the mechanical properties of the CC hydrogel (+349% in compressive strength and +153% in Young's modulus), which also exhibited a large pore size, appropriate porosity, and fast water absorption ability. Biologically, the engineered CDM-Fib/CC scaffold significantly promoted the adhesion and proliferation of chondrocytes and supported the formation of matured cartilage tissue with a cartilagelike structure and deposition of abundant cartilage ECM-specific GAGs and type II collagen (+42% in GAGs content and +295% in type II collagen content). The enhanced mechanical competency and chondroinduction capacity with the engineered CDM-Fib/CC scaffold eventually fulfilled successful in situ osteochondral regeneration in a rabbit model. This study thereby demonstrated a great potential of the engineered highly biomimetic chitosan-based scaffold in cartilage tissue repair and regeneration.

Role of bone 1stem cell-seeded 3D polylactic acid/polycaprolactone/hydroxyapatite scaffold on a critical-sized radial bone defect in rat

Osteoconductive biomaterials were used to find the most reliable materials in bone healing. Our focus was on the bone healing capacity of the stem cell-loaded and unloaded PLA/PCL/HA scaffolds. The 3D scaffold of PLA/PCL/HA was characterized by scanning electron microscopy (SEM), rheology, X-ray diffraction (XRD), and Fourier transform-infrared (FT-IR) spectroscopy. Bone marrow stem cells (BMSCs) have multipotential differentiation into osteoblasts. Forty Wistar male rats were used to organize four experimental groups: control, autograft, scaffold, and BMSCs-loaded scaffold groups. qRT-PCR showed that the BMSCs-loaded scaffold had a higher expression level of CD31 and osteogenic markers compared with the control group (P < 0.05). Radiology and computed tomography (CT) scan evaluations showed significant improvement in the BMSCs-loaded scaffold compared with the control group (P < 0.001). Biomechanical estimation demonstrated significantly higher stress (P < 0.01), stiffness (P < 0.001), and ultimate load (P < 0.01) in the autograft and BMSCs-loaded scaffold groups compared with the untreated group and higher strain was seen in the control group than the other groups (P < 0.01). Histomorphometric and immunohistochemical (IHC) investigations showed significantly improved regeneration scores in the autograft and BMSCs-loaded scaffold groups compared with the control group (P < 0.05). Also, there was a significant difference between the scaffold and control groups in all tests (P < 0.05). The results depicted that our novel approach will allow to develop PLA/PCL/HA 3D scaffold in bone healing via BMSC loading.

Organogel Coupled with Microstructured Electrospun Polymeric Nonwovens for the Effective Cleaning of Sensitive Surfaces

Hydrogels and organogels are widely used as cleaning materials, especially when a controlled solvent release is necessary to prevent substrate damage. This situation is often encountered in the personal care and electronic components fields and represents a challenge in restoration, where the removal of a thin layer of aged varnish from a painting may compromise the integrity of the painting itself. There is an urgent need for new and effective cleaning materials capable of controlling and limiting the use of solvents, achieving at the same time high cleaning efficacy. In this paper, new sandwich-like composites that fully address these requirements are developed by using an organogel (poly(3-hydroxybutyrate) + γ-valerolactone) in the core and two external layers of electrospun nonwovens made of continuous submicrometric fibers produced by electrospinning (either poly(vinyl alcohol) or polyamide 6,6). The new composite materials exhibit an extremely efficient cleaning action that results in the complete elimination of the varnish layer with a minimal amount of solvent adsorbed by the painting layer after the treatment. This demonstrates that the combined materials exert a superficial action that is of utmost importance to safeguard the painting. Moreover, we found that the electrospun nonwoven layers act as mechanically reinforcement components, greatly improving the bending resistance of organogels and their handling. The characterization of these innovative cleaning materials allowed us to propose a mechanism to explain their action: electrospun fibers play the leading role by slowing down the diffusion of the solvent and by conferring to the entire composite a microstructured rough superficial morphology, enabling to achieve outstanding cleaning performance.

PCL-Based Composite Scaffold Matrices for Tissue Engineering Applications

Biomaterial-based scaffolds are important cues in tissue engineering (TE) applications. Recent advances in TE have led to the development of suitable scaffold architecture for various tissue defects. In this narrative review on polycaprolactone (PCL), we have discussed in detail about the synthesis of PCL, various properties and most recent advances of using PCL and PCL blended with either natural or synthetic polymers and ceramic materials for TE applications. Further, various forms of PCL scaffolds such as porous, films and fibrous have been discussed along with the stem cells and their sources employed in various tissue repair strategies. Overall, the present review affords an insight into the properties and applications of PCL in various tissue engineering applications.

Nanofibers and Microfibers for Osteochondral Tissue Engineering

The use of fibers into scaffolds is a way to mimic natural tissues, in which fibrils are embedded in a matrix. The use of fibers can improve the mechanical properties of the scaffolds and may act as structural support for cell growth. Also, as the morphology of fibrous scaffolds is similar to the natural extracellular matrix, cells cultured on these scaffolds tend to maintain their phenotypic shape. Different materials and techniques can be used to produce micrfibers- and nanofibers for scaffolds manufacturing; cells, in general, adhere and proliferate very well on PCL, chitosan, silk fibroin, and other nanofibers. One of the most important techniques to produce microfibers/nanofibers is electrospinning. Nanofibrous scaffolds are receiving increasing attention in bone tissue engineering, because they are able to offer a favorable microenvironment for cell attachment and growth. Different polymers can be electrospun, i.e., polyester, polyurethane, PLA, PCL, collagen, and silk. Other materials such as bioglass fibers, nanocellulose, and even carbon fiber and fabrics have been used to help increase bioactivity, mechanical properties of the scaffold, and cell proliferation. A compilation of mechanical properties and most common biological tests performed on fibrous scaffolds is included in this chapter.

HIGHLIGHTS

The use of microfibers and nanofibers allows for tailoring the scaffold properties. Electrospinning is one of the most important techniques nowadays to produce fibrous scaffolds. Microfibers and nanofibers use in scaffolds is a promising field to improve the behavior of scaffolds in osteochondral applications.

Advancements and Challenges in Multidomain Multicargo Delivery Vehicles

Reparative and regenerative processes are well-orchestrated temporal and spatial events that are governed by multiple cells, molecules, signaling pathways, and interactions thereof. Yet again, currently available implantable devices fail largely to recapitulate nature's complexity and sophistication in this regard. Herein, success stories and challenges in the field of layer-by-layer, composite, self-assembly, and core-shell technologies are discussed for the development of multidomain/multicargo delivery vehicles.

Poly (lactic acid)-based biomaterials for orthopaedic regenerative engineering

Regenerative engineering converges tissue engineering, advanced materials science, stem cell science, and developmental biology to regenerate complex tissues such as whole limbs. Regenerative engineering scaffolds provide mechanical support and nanoscale control over architecture, topography, and biochemical cues to influence cellular outcome. In this regard, poly (lactic acid) (PLA)-based biomaterials may be considered as a gold standard for many orthopaedic regenerative engineering applications because of their versatility in fabrication, biodegradability, and compatibility with biomolecules and cells. Here we discuss recent developments in PLA-based biomaterials with respect to processability and current applications in the clinical and research settings for bone, ligament, meniscus, and cartilage regeneration.

Assessment of polycaprolacton (PCL) nanocomposite scaffold compared with hydroxyapatite (HA) on healing of segmental femur bone defect in rabbits

Segmental bone loss due to trauma, infection, and tumor resection and even non-union results in the vast demand for replacement and restoration of the function of the lost bone. The objective of this study is to utilize novel inorganic-organic nanocomposites for biomedical applications. Biodegradable implants have shown great promise for the repair of bone defects and have been commonly used as bone substitutes, which traditionally would be treated using metallic implants. In this study, 45 mature male New Zealand white rabbits 6-8 months and weighting 3-3.5 kg were examined. Rabbits were divided into three groups. Surgical procedures were done after an intramuscular injection of Ketamine 10% (ketamine hydrochloride, 50 mg/kg), Rompun 5% (xylazine, 5 mg/kg). Then an approximately 6 mm diameter - 5 mm cylinder bone defect was created in the femur of one of the hind limbs. After inducing the surgical wound, all rabbits were colored and randomly divided into three experimental groups of nine animals each: Group 1 received medical pure nanocomposite polycaprolactone (PCL) granules, Group 2 received hydroxyapatite and Group 3 was a control group with no treatment. Histopathological evaluation was performed on days 15, 30 and 45 after surgery. On day 45 after surgery, the quantity of newly formed lamellar bone in the healing site in PCL group was better than onward compared with HA and control groups. Finally, nanocomposite PCL granules exhibited a reproducible bone-healing potential.

Monocyte chemoattractant protein-1 released from polycaprolactone/chitosan hybrid membrane to promote angiogenesis in vivo

We have fabricated a hybrid membrane composed of polycaprolactone and a natural polysaccharide, chitosan. The incorporation of chitosan enabled heparinization of the material via electrostatic interaction between heparin and chitosan. More importantly, since multiple cytokines have exhibited binding affinity towards heparin, heparinization of the polycaprolactone/chitosan compound also facilitated immobilization of monocyte chemoattractant protein-1, which is a well-reported pro-angiogenic chemokine. Results demonstrated that the heparinized polycaprolactone/chitosan membrane with monocyte chemoattractant protein-1 immobilization was able to release monocyte chemoattractant protein-1 in a controlled and sustained manner. Bioactivity of the released monocyte chemoattractant protein-1 was uncompromised as shown by a chemotaxis chamber assay using isolated rat peripheral blood mononuclear cells. Enhanced local angiogenesis was subsequently observed in vivo after subcutaneous implantation of the heparinized polycaprolactone/chitosan membrane with monocyte chemoattractant protein-1-releasing property and the mechanisms underlying the angiogenic role of monocyte chemoattractant protein-1 were also investigated. We propose that the monocyte chemoattractant protein-1-induced local capillary formation is attributable to increased recruitment of macrophages, particularly the alternatively activated M2 macrophages, which have been implicated in wound healing. Moreover, a direct effect of monocyte chemoattractant protein-1 on angiogenesis was also observed, mainly via monocyte chemoattractant protein-1-stimulated vascular endothelial growth factor expression and activity. In summary, we report here a feasible way to fabricate a polycaprolactone/chitosan hybrid material that could be functionalized with angiogenic signalling agents, such as monocyte chemoattractant protein-1. Implantation of this material promoted angiogenesis and may therefore be developed into scaffold or dressing materials in treating local ischemia injuries or cutaneous wound.

In vitro degradation and in vivo biocompatibility of chitosan–poly(butylene succinate) fiber mesh scaffolds

In tissue engineering, the evaluation of the host response to the biomaterial implantation must be assessed to determine the extent of the inflammatory reaction. We studied the degradation of poly(butylene succinate) and chitosan in vitro using lipase and lysozyme enzymes, respectively. The subcutaneous implantation of the scaffolds was performed to assess tissue response. The type of inflammatory cells present in the surrounding tissue, as well as within the scaffold, was determined histologically and by immunohistochemistry. In the presence of lipase or lysozyme, the water uptake of the scaffolds increased. Based on the weight loss data and scanning electron microscopy analysis, the lysozyme combined with lipase had a notable effect on the in vitro degradation of the scaffolds. The in vivo implantation showed a normal inflammatory response, with presence of neutrophils, in a first stage, and macrophages, lymphocytes, and giant cells in a later stage. Vascularization in the surrounding tissue and within the implant increased with time. Moreover, the collagen deposition increased with time inside the implant. In vivo, the scaffolds maintained the structural integrity. The degradation in vitro was faster and greater compared to that observed in vivo within the same time periods.

Preparation of collagen scaffolds with controlled pore structures and improved mechanical property for cartilage tissue engineering

Appropriate pore structures and mechanical properties are required for scaffolds that are used for tissue engineering and regenerative medicine. In this study, pre-prepared ice particulates were used as a porogen material to prepare collagen porous scaffolds with well-controlled pore structures and improved mechanical properties. Porogen ice particulates initiated the formation of interconnected large spherical pores surrounded by small pores. The large spherical pores were well compacted and increased the elastic modulus of the scaffolds. The unique pore structures facilitated cell penetration, resulting in a homogeneous cell distribution throughout the scaffolds. The excellent mechanical properties protected the scaffolds from deformation during cell culturing and implantation. The collagen porous scaffolds facilitated cartilage regeneration when bovine articular chondrocytes were cultured in these scaffolds. The use of pre-prepared ice particulates as a porogen material proved to be a useful method to control the pore structure and improve the mechanical properties of collagen-based porous scaffolds.