Current Pharmaceutical Design - Volume 21, Issue 12, 2015

Recent advances in tissue engineering and regenerative medicine have shown that controlling cells microenvironment during growth is a key element to the development of successful therapeutic system. To achieve such control, researchers have first proposed the use of polymeric scaffolds that were able to support cellular growth and, to a certain extent, favor cell organization and tissue structure. With nowadays availability of a large pool of stem cell lines, such approach has appeared to be rather limited since it does not offer the fine control of the cell micro-environment in space and time (4D). Therefore, researchers are currently focusing their efforts on developing strategies that include active compound delivery systems in order to add a fourth dimension to the design of 3D scaffolds. This review will focus on recent concepts and applications of 2D and 3D techniques that have been used to control the load and release of active compounds used to promote cell differentiation and proliferation in or out of a scaffold. We will first present recent advances in the design of 2D polymeric scaffolds and the different techniques that have been used to deposit molecular cues and cells in a controlled fashion. We will continue presenting the recent advances made in the design of 3D scaffolds based on hydrogels as well as polymeric fibers and we will finish by presenting some of the research avenues that are still to be explored.

Traumatic Spinal Cord Injuries (TSCI), due to their devastating nature, present several interventional challenges (extensive inflammation, axonal tethering, scar formation, neuronal degeneration and functional loss) that need to be addressed before even a slight neuronal recovery can be achieved. Recent post-TSCI investigational approaches include a combination of “support and therapeutic” strategies capable of providing localized delivery of therapeutic molecules along with specialized architecture to allow axonal growth and conformal repair. This review provides a brief overview of multifunctional therapeutic delivery strategies for effective neuroregeneration post-TSCI with special emphasis on intrathecal hydrogel-based injectable systems, chondroitinase ABC releasing matrices, micro/nano-sized particulate strategies, 3D-scaffold architectures, biopolymeric channeled bridges for directed neuronal growth, functionalized nerve conduits, nano- and micro-fibrous scaffolds and multicomponent combinatorial paradigms for localized delivery to spinal cord. In addition; a comprehensive account of most widely employed macromolecules and the related neuro-pharmacological, -anatomical, and -functionaloutcomes conferred by the abovementioned neural tissue engineering approaches is provided. Furthermore, the performance of individual delivery systems towards the enhancement of effectiveness, efficiency, and stability of therapeutic molecules and neurotrophic factors is discussed. In conclusion, it is suggested that a multifunctional combinatorial device assimilating the biomaterial, cellular, molecular, structural and functional aspects altogether is the best way forward for effective neuroregeneration post-TSCI.

Reconstituted high density lipoprotein (rHDL) is an excellent and highly biocompatible nanovector mimicking the physical, chemical as well as physiological properties of native high density lipoprotein (HDL), and is originally widely used as the substitute in HDL related studies. Over the past decades, rHDL has increasingly been exploited into vehicles for targeted delivery of numerous drugs, therapeutic genes, etc., and is playing a more and more important role in drug delivery design for regenerative medicine. As such, a systematic review of this promising carrier will be of great importance for subsequent studies. In this article, the term “rHDL-based nanoparticles (rHDLbased NPs)” is employed to refer to rHDL and its modified form. This review highlights four aspects of rHDL-based NPs: current applications in regenerative medicine, preparation methods, conventional evaluation methods, and future trends on co-delivery of drugs for synergic effects.

The importance of growth factor delivery in cartilage tissue engineering is nowadays widely recognized. However, when growth factors are administered by a bolus injection, they undergo rapid clearance before they could stimulate the cells of interest at promoting cartilage repair. Their short half-lives make growth factors ineffective, unless administered at supraphysiological doses, with potentially harmful consequences on patient safety. Recently, new tissue engineering strategies relying on the combination of biodegradable scaffolds and specific biological cues, such as growth or adhesive factors or genetic material, have demonstrated that controlled release is the key factor for achieving effective cartilage repair at lower drug doses. Among all biomaterials, hydrogels have emerged as promising cartilage tissue engineering scaffolds for simultaneous cell growth and drug delivery. In fact, hydrogels can be easily loaded with cells and drugs, that are subsequently released in a controlled fashion. The success of hydrogels in controlled drug delivery for tissue engineering originates from their biocompatibility and capacity to integrate well with the host tissue. This review overviews the hydrogels technologies now available for the regeneration of cartilage that base their efficacy on the controlled release of bioactive substances able to modulate cellular behavior and to eventually lead to successful tissue repair.

Wound healing is a complex regenerative process of great importance in clinical medicine, controlled by temporal interactions between cells, extracellular matrix components and signalling molecules. Localised delivery of therapeutic active agents viz. antimicrobials, soothing minerals and/or vitamins and growth factors at the site of injury/trauma/wound are expected to be more effective and will always manifest milder toxic concerns than those observed upon systemic administration of these agents. Since ancient times, search is on for suitable materials which may restore or reproduce a favourable and a natural milieu required for skin regeneration, so as to prevent infections, and make the process fast and less painful. The journey started with the use of natural materials with a simple function of covering or dressing the wounds to more advanced materials of present times, which are designed for specific and extraordinary functions. Natural and modified or synthetic polymers; alone or in combination are commonly used as dressing (couture) materials for wound healing. This article offers a review of materials that have been used to design and develop wound dressings.

Musculoskeletal metabolic diseases such as osteoporosis have become the major public health problems worldwide in our aging society. Pharmaceutical therapy is one of the approaches to prevent and treat related medical conditions. Most of the clinically used anti-osteoporotic drugs are administered systemically and have demonstrated some side effects in non-skeletal tissues. One of the innovative approaches to prevent potential adverse effects is the development of bone-targeting drug delivery technologies that not only minimizes the systemic toxicity but also improves the pharmacokinetic profile and therapeutic efficacy of chemical drugs. This paper reviews the currently available bone targeting drug delivery systems with emphasis as bone-targeting moieties, including the bonesurface- site-specific (bone formation dominant or bone resorption dominant) and cell-specific moieties. In addition, the connections of drug-bone-targeting moieties-carrier are also summarized, and the newly developed liposomes and nanoparticles are discussed for their potential use and main challenges in delivering therapeutic agents to bone tissue. As a rapid-developing biotechnology, systemic bonetargeting delivery system is promising but still in its infancy where challenges are ahead of us, including the stability and the toxicity issues, especially to fulfill the regulatory requirement to realize bench-to-bedside translation. Newly developed biomaterials and technologies with potential for safer and more effective drug delivery require multidisciplinary collaborations with preclinical and clinical scientists that are essential to facilitate their clinical applications.

Heart failure is one of the most prominent causes of morbidity and mortality worldwide. According to the World Health Organization, coronary artery disease and myocardial infarction (MI) are responsible for 29% of deaths worldwide. MI results in obstruction of the blood supply to the heart and scar formation, and causes substantial death of cardiomyocytes in the infarct zone followed by an inflammatory response. Current treatment methodologies of MI and heart failure include organ transplantation, coronary artery bypass grafting, ventricular remodeling, cardiomyoplasty, and cellular therapy. Each of these methodologies has associated risks and benefits. Cellular cardiomyoplasty is a viable option to decrease the fibrosis of infarct scars, adverse post-ischemic remodeling, and improve heart function. However, the low rate of cell survival, shortage of cell sources and donors, tumorigenesis, and ethical issues hamper full exploitation of cell therapy for MI treatment. Consequently, the mobilization and recruitment of endogenous stem/progenitor cells from bone marrow, peripheral circulation, and cardiac tissues has immense potential through harnessing the host’s own reparative capacities that result from interplay among cytokines, chemokines, and adhesion molecules. Therapeutic treatments to enhance the mobilization and homing of stem cells are under development. In this review, we present state-of-the-art approaches that are being pursued for stem cell mobilization and recruitment to regenerate infarcted myocardium. Potential therapeutic interventions and delivery strategies are discussed in detail.

1, 2-Distearoyl-sn-glycero-3-phosphoethanolamine-Poly(ethylene glycol) (DSPE- PEG) is a widely used phospholipids-polymer conjugate in drug delivery applications. It is a biocompatible, biodegradable and amphiphilic material which can also be functionalized with various biomolecules for specific functions. With the emerging interest in use of nanocarriers for therapeutic drug delivery and imaging DSPE-PEG has become a very useful material for the formulation of these nanocarriers for achieving prolonged blood circulation time, improved stability and enhanced encapsulation efficiency. This review will focus on the relationships between the structure of DSPEPEG and its noticeable effects on these nanocarriers’ properties, and the recent progress on the development of DSPE-PEG and its derivatives in delivery systems.

Many researchers have attempted to use computer-aided design (CAD) and computer-aided manufacturing (CAM) to realize a scaffold that provides a three-dimensional (3D) environment for regeneration of tissues and organs. As a result, several 3D printing technologies, including stereolithography, deposition modeling, inkjet-based printing and selective laser sintering have been developed. Because these 3D printing technologies use computers for design and fabrication, and they can fabricate 3D scaffolds as designed; as a consequence, they can be standardized. Growth of target tissues and organs requires the presence of appropriate growth factors, so fabrication of 3Dscaffold systems that release these biomolecules has been explored. A drug delivery system (DDS) that administrates a pharmaceutical compound to achieve a therapeutic effect in cells, animals and humans is a key technology that delivers biomolecules without side effects caused by excessive doses. 3D printing technologies and DDSs have been assembled successfully, so new possibilities for improved tissue regeneration have been suggested. If the interaction between cells and scaffold system with biomolecules can be understood and controlled, and if an optimal 3D tissue regenerating environment is realized, 3D printing technologies will become an important aspect of tissue engineering research in the near future.

Regenerative medicine holds much promise in assisting patients to recover from injured or lost tissues and organs through organism reconstruction. Three-dimensional (3D) biomimetic models via various approaches can be used by pharmaceutical industry for controlled drug delivery. With proper biomaterials and engineering technologies, drugs can be released in a rate-manipulated manner towards targeted regions with spatial and temporal effects. Much of the success is a result of a combination of growth factors, stem cells, biomaterials, nanotechnologies, electrospinning and 3D printing techniques mimicking in vivo angiogenesis, histogenesis and tumorigenesis processes. This interdisciplinary field on biomimetic drug delivery and regenerative medicine has already opened up a new avenue for medical progress and reformation. This article presents a comprehensive review of the 3D biomimetic models in the pertinent fields of tissue and organ manufacturing, cell-material mutual interactions, bioactive agent carrier systems and anti-cancer drug delivery methods. Particularly, the potential trends and challenges of tissue and organ manufacturing are discussed from different perspectives.

How to release growth factors (GFs) scientifically to promote stem cell proliferation and differentiation is one of the most significant research focuses in the field of regenerative medicine. In a controlled release system, growth factors, extracellular matrices or biomaterial carriers, and sometimes stem cells together form a geometric entirety. Biomaterial carriers provide GFs with a support structure to be adhered, immobilized, encapsulated or/and protected. As a unity, the release rate and rhythm of GFs on cells are normally very delicate and precise. Up to now, the best strategy for clinical applications is the combination systems that encapsulate GFs in microspheres, particularly the nano- or micro-encapsulation techniques integrated GFs with biomaterial carriers. In this mini review, we summarize the current progress in GF delivery systems for regenerative medicine and provide an outlook on two main aspects: one is the classes of stem cells and GFs that have been used frequently in regenerative medicine, including their respective application conditions and functions; the other is the controlled GF release systems, in which various GFs are released orderly and continuously without diffusing simply and rapidly, including their respective opportunities and challenges.

Nano-sized systems have shown promise for efficient vaginal drug delivery providing sustained drug release and enhanced permeation. In parallel with advancements in drug discovery of new vaginal therapeutic agents, such as peptides, proteins, nucleic material, antigens, hormones, and microbicides, nanoplatforms are gaining momentum as prospective vectors for these agents. Thus far, extensive research in this arena has been focused on local delivery to the mucus vagina. However, an improved understanding of vaginal route, advantages offered by the vaginal route including being non-invasive and bypassing hepatic first-effect metabolism, and recent success achieved by vaginal drug nanocarriers may open the door for extensive nanotechnology- based research to explore the viability of systemic administration via this route. The review analyzes the possibilities given by nanoplatform-based delivery systems in the vaginal delivery of active agents. Special insight is given to the most important aspects to be considered during nanomedicine development and preclinical evaluation, i.e., the anatomy and physiology of the vagina, advantages of vaginal route of drug administration, and barriers to vaginal drug delivery. Finally, an updated analysis of the recent advancements of nanomedicine technologies and their potential progress into the clinic is compiled in this work.

The mammalian target of rapamycin (mTOR), which assembles into two distinct multiprotein complexes, called mTORC1 and mTORC2, is known as a central regulator of cellular proliferation and maturation. Rictor is one of the key components of mTORC2 and acts as a scaffolding protein to maintain and stabilize mTORC2. Currently, mTORC2 and/or Rictor are increasingly being recognized as attractive targets for novel modalities of anti-cancer therapy. Unfortunately, the safety profile of Rictor- or mTORC2-targeting strategies has been poorly understood due to the lack of an ideal animal model. In the present study, we used zebrafish as an in vivo model system to evaluate the safety of Rictor inhibition. Our data showed that the Rictor of zebrafish was identified to have high sequence homology with mouse Rictor and human Rictor, which validates the rationale of using zebrafish as a research model. Rictor was dispensable in neonatal hematopoiesis and angiogenesis and was not required for vasculogenesis and other organs. These data are consistent with those of previous observations of using tissue-specific Rictor knockout mice model and have potentially important clinical implications. Our findings highlight a good in vivo safety profile for Rictor- or mTORC2-targeting therapy and point to the feasibility and advantages of using the zebrafish model to evaluate the safety of the therapeutic target.