Modulating the immune system towards a functional chronic wound healing: A biomaterials and Nanomedicine perspective

Chronic non-healing wounds persist as a substantial burden for healthcare systems, influenced by factors such as aging, diabetes, and obesity. In contrast to the traditionally pro-regenerative emphasis of therapies, the recognition of the immune system integral role in wound healing has significantly grown, instigating an approach shift towards immunological processes. Thus, this review explores the wound healing process, highlighting the engagement of the immune system, and delving into the behaviors of innate and adaptive immune cells in chronic wound scenarios. Moreover, the article investigates biomaterial-based strategies for the modulation of the immune system, elucidating how the adjustment of their physicochemical properties or their synergistic combination with other agents such as drugs, proteins or mesenchymal stromal cells can effectively modulate the behaviors of different immune cells. Finally this review explores various strategies based on synthetic and biological nanostructures, including extracellular vesicles, to finely tune the immune system as natural immunomodulators or therapeutic nanocarriers with promising biophysical properties.

Genetically engineered loaded extracellular vesicles for drug delivery

The use of extracellular vesicles (EVs) for drug delivery is being widely explored by scientists from several research fields. To fully exploit their therapeutic potential, multiple methods for loading EVs have been developed. Although exogenous methods have been extensively utilized, in recent years the endogenous method has gained significant attention. This approach, based on parental cell genetic engineering, is suitable for loading large therapeutic biomolecules such as proteins and nucleic acids. We review the most commonly used EV loading methods and emphasize the inherent advantages of the endogenous method over the others. We also examine the most recent advances and applications of this innovative approach to inform on the diverse therapeutic opportunities that lie ahead in the field of EV-based therapies.

PLGA-PEI nanoparticle covered with poly(I:C) for personalised cancer immunotherapy

Melanoma is the main cause of death among skin cancers and its incidence worldwide has been experiencing an appalling increase. However, traditional treatments lack effectiveness in advanced or metastatic patients. Immunotherapy, meanwhile, has been shown to be an effective treatment option, but the rate of cancers responding remains far from ideal. Here we have developed a personalized neoantigen peptide-based cancer vaccine by encapsulating patient derived melanoma neoantigens in polyethylenimine (PEI)-functionalised poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) and coating them with polyinosinic:polycytidylic acid (poly(I:C)). We found that PLGA NPs can be effectively modified to be coated with the immunoadjuvant poly(I:C), as well as to encapsulate neoantigens. In addition, we found that both dendritic cells (DCs) and lymphocytes were effectively stimulated. Moreover, the developed NP was found to have a better immune activation profile than NP without poly(I:C) or without antigen. Our results demonstrate that the developed vaccine has a high capacity to activate the immune system, efficiently maturing DCs to present the antigen of choice and promoting the activity of lymphocytes to exert their cytotoxic function. Therefore, the immune response generated is optimal and specific for the elimination of melanoma tumour cells.

3D-printed Laponite/Alginate hydrogel-based suppositories for versatile drug loading and release

Traditional approaches to solid rectal therapies have halted progress, leading to a continual decline in the use of conventional suppositories. Additive manufacturing techniques have been recently explored as a suitable innovative tool for suppository fabrication. However, little advancement has been made in composition materials for 3D-printed suppository (3DPS) manufacturing and still, conventional vehicles are often used for construct fabrication, hindering the growth in the field. As a novelty, this study unveils a ground-breaking Laponite-alginate hydrogel-based 3DPS. Interestingly, this study proposes a novel approach for loading drugs into the 3DPS employing for the first time the post-printing loading. Thus, a passive loading strategy of molecular models is developed, demonstrating the versatility and capacity to load molecules of different charges and molecular sizes within the matrix systems. This novel strategy allows adapting the load of a wide range of drugs into a single ink, which simplifies and speeds up the 3DPS technological development process for drugs with different physico-chemical properties. Additionally, in this research, a displacement strategy of the three-dimensional Laponite matrices is developed in order to enhance the drug release capacity through the 3DPS and their disintegration capacity, resulting in a significant improvement of the drug diffusion through the hydrogel matrix and a rapid disintegration of the 3DPS. Finally, our study demonstrates that the obtained 3DPS have a suitable in vivo behavior, being non-obstructive and allowing the normal motility of the rats intestine.

Soy protein/β-chitin sponge-like scaffolds laden with human mesenchymal stromal cells from hair follicle or adipose tissue promote diabetic chronic wound healing

Chronic wounds are a worldwide problem that affect >40 million people every year. The constant inflammatory status accompanied by prolonged bacterial infections reduce patient's quality of life and life expectancy drastically. An important cell type involved in the wound healing process are mesenchymal stromal cells (MSCs) due to their long-term demonstrated immunomodulatory and pro-regenerative capacity. Thus, in this work, we leveraged and compared the therapeutic properties of MSCs derived from both adipose tissue and hair follicle, which we combined with sponge-like scaffolds (SLS) made of valorized soy protein and β-chitin. In this regard, the combination of these cells with biomaterials permitted us to obtain a multifunctional therapy that allowed high cell retention and growing rates while maintaining adequate cell-viability for several days. Furthermore, this combined therapy demonstrated to increase fibroblasts and keratinocytes migration, promote human umbilical vein endothelial cells angiogenesis and protect fibroblasts from highly proteolytic environments. Finally, this combined therapy demonstrated to be highly effective in reducing wound healing time in vivo with only one treatment change during all the experimental procedure, also promoting a more functional and native-like healed skin.

Extracellular vesicles released by hair follicle and adipose mesenchymal stromal cells induce comparable neuroprotective and anti-inflammatory effects in primary neuronal and microglial cultures

BACKGROUND AIMS

Despite intensive research, to date, there is no effective treatment for neurodegenerative diseases. Among the different therapeutic approaches, recently, the use of extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) has gained attention.

METHODS

In the present work, we focused on medium/large extracellular vesicles (m/lEVs) derived from hair follicle--derived (HF) MSCs, comparing their potential neuroprotective and anti-inflammatory effect against adipose tissue (AT)-MSC-derived m/lEVs.

RESULTS

The obtained m/lEVs were similar in size with comparable expression of surface protein markers. The neuroprotective effect of both HF-m/lEVs and AT-m/lEVs was statistically significant in dopaminergic primary cell cultures, increasing cell viability after the incubation with 6-hidroxydopamine neurotoxin. Moreover, the administration of HF-m/lEVs and AT-m/lEVs counteracted the lipopolysaccharide-induced inflammation in primary microglial cell cultures, decreasing the levels of pro-inflammatory cytokines, tumor necrosis factor-α and interleukin-1β.

CONCLUSIONS

Taken together, HF-m/lEVs demonstrated comparable potential with that of AT-m/lEVs as multifaceted biopharmaceuticals for neurodegenerative disease treatment.

Targeting the central nervous system: From synthetic nanoparticles to extracellular vesicles-Focus on Alzheimer's and Parkinson's disease

Neurodegenerative diseases (NDs) such as Alzheimer's disease (AD) and Parkinson's disease (PD) are an accelerating global health problem as life expectancy rises worldwide. Despite their significant burden in public health systems to date, the existing treatments only manage the symptoms without slowing down disease progression. Thus, the ongoing neurodegenerative process remains untreated. Moreover, the stronghold of the brain-the blood-brain barrier (BBB)-prevents drug penetrance and dwindles effective treatments. In the last years, nanotechnology-based drug delivery systems (DDS) have become a promising approach to target and treat these disorders related to the central nervous system (CNS). PLGA based nanoparticles (NPs) were the first employed DDS for effective drug delivery. However, the poor drug loading capacity and localized immunogenicity prompted the scientific community to move to another DDS such as lipid-based NPs. Despite the lipid NPs' safety and effectiveness, their off-target accumulation together with the denominated CARPA (complement activation-related pseudo allergy) reaction has limited their complete clinical translation. Recently, biological NPs naturally secreted by cells, termed as extracellular vesicles (EVs) have emerged as promising more complex biocompatible DDS. In addition, EVs act as dual players in NDs treatment, as a "cell free" therapy themselves, as well as new biological NPs with numerous characteristics that qualify them as promising carriers over synthetic DDS. The present review aims to display advantages, drawbacks, current limitations and future prospective of the previously cited synthetic and biological DDS to enter the brain and treat one of 21st century most challenging diseases, NDs. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease.

Agar/gelatin hydro-film containing EGF and Aloe vera for effective wound healing

In the current study, we produced a hydro-film dressing for the treatment of chronic wounds. The hydro-film structure was composed of gelatin cross-linked with citric acid, agar and Aloe vera extract (AV); additionally epidermal growth factor (EGF) was loaded to promote wound healing. Due to the excellent hydrogel-forming ability of gelatin, the obtained hydro-film was able to swell 884 ± 36% of its dry weight, which could help controlling wound moisture. To improve gelatin mechanical properties, polymer chains were cross-linked with citric acid and agar, reaching an ultimate tensile strength that was in the highest range of human skin. In addition, it showed a slow degradation profile that resulted in a remaining weight of 28 ± 8% at day 28. Regarding, biological activity, the addition of AV and citric acid provided the ability to reduce human macrophage activation, which could help reverse the permanent inflammatory state of chronic wounds. Moreover, loaded EGF, together with the structural AV of the hydro-film, promoted human keratinocyte and fibroblast migration, respectively. Furthermore, the hydro-films presented excellent fibroblast adhesiveness, so they could be useful as provisional matrices for cell migration. Accordingly, these hydro-films showed suitable physicochemical characteristics and biological activity for chronic wound healing applications.

Computational and Experimental Evaluation of the Immune Response of Neoantigens for Personalized Vaccine Design

In the last few years, the importance of neoantigens in the development of personalized antitumor vaccines has increased remarkably. In order to study whether bioinformatic tools are effective in detecting neoantigens that generate an immune response, DNA samples from patients with cutaneous melanoma in different stages were obtained, resulting in a total of 6048 potential neoantigens gathered. Thereafter, the immunological responses generated by some of those neoantigens ex vivo were tested, using a vaccine designed by a new optimization approach and encapsulated in nanoparticles. Our bioinformatic analysis indicated that no differences were found between the number of neoantigens and that of non-mutated sequences detected as potential binders by IEDB tools. However, those tools were able to highlight neoantigens over non-mutated peptides in HLA-II recognition (p-value 0.03). However, neither HLA-I binding affinity (p-value 0.08) nor Class I immunogenicity values (p-value 0.96) indicated significant differences for the latter parameters. Subsequently, the new vaccine, using aggregative functions and combinatorial optimization, was designed. The six best neoantigens were selected and formulated into two nanoparticles, with which the immune response ex vivo was evaluated, demonstrating a specific activation of the immune response. This study reinforces the use of bioinformatic tools in vaccine development, as their usefulness is proven both in silico and ex vivo.

Tumour-derived extracellular vesicle based vaccines for melanoma treatment

The interest of extracellular vesicles (EVs) in cancer immunotherapy is increasing every day. EVs are lipid bilayer vesicles released by most cells, which contain the molecular signature of their parent cell. Melanoma-derived EVs present antigens specific to this aggressive type of cancer, but they also exert immunomodulatory and pro-metastatic activity. Until now, most reviews focus on the immunoevasive characteristics of tumour-derived EVs, but do not help to overcome the issues related to them. In this review, we describe isolation methods of EVs from melanoma patients and most interesting markers to oversee their effect if they are used as antigen carriers. We also discuss the methods developed so far to overcome the lack of immunogenicity of melanoma-derived EVs, which includes EV modification or adjuvant co-administration. In summary, we conclude that EVs can be an interesting antigen source for immunotherapy development once EV obtaining is optimised and the understanding of the mechanisms behind their multiple effects is further understood.

High resolution and fidelity 3D printing of Laponite and alginate ink hydrogels for tunable biomedical applications

The formulation of hydrogels that meet the necessary flow characteristics for their extrusion-based 3D printing while providing good printability, resolution, accuracy and stability, requires long development processes. This work presents the technological development of a hydrogel-based ink of Laponite and alginate and evaluates its printing capacity. As a novelty, this article reports a standardizable protocol to quantitatively define the best printing parameters for the development of novel inks, providing new printability evaluation parameters such as the Printing Accuracy Escalation Index. As a result, this research develops a printable Laponite-Alginate hydrogel that presents printability characteristics. This ink is employed for the reproducible manufacture of 3D printed scaffolds with versatile and complex straight or curved printing patterns for a better adaptation to different final applications. Obtained constructs prove to be stable over time thanks to the optimization of a curing process. In addition, the study of the swelling and degradation behavior of the Laponite and alginate 3D printed scaffolds in different culture media allows the prediction of their behavior in future in vitro or in vivo developments. Finally, this study demonstrates the absence of cytotoxicity of the printed formulations, hence, setting the stage for their use in the field of biomedicine.

Colistin- and amikacin-loaded lipid-based drug delivery systems for resistant gram-negative lung and wound bacterial infections

Antimicrobial resistance (AMR) is a global health issue, which needs to be tackled without further delay. The World Health Organization(WHO) has classified three gram-negative bacteria, Pseudomonas aeruginosa, Klebsiella pneumonia and Acinetobacter baumannii, as the principal responsible for AMR, mainly causing difficult to treat nosocomial lung and wound infections. In this regard, the need for colistin and amikacin, the re-emerged antibiotics of choice for resistant gram-negative infections, will be examined as well as their associated toxicity. Thus, current but ineffective clinical strategies designed to prevent toxicity related to colistin and amikacin will be reported, highlighting the importance of lipid-based drug delivery systems (LBDDSs), such as liposomes, solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs), as efficient delivery strategies for reducing antibiotic toxicity. This review reveals that colistin- and amikacin-NLCs are promising carriers with greater potential than liposomes and SLNs to safely tackle AMR, especially for lung and wound infections.

Extracellular vesicles from hair follicle-derived mesenchymal stromal cells: isolation, characterization and therapeutic potential for chronic wound healing

BACKGROUND

Mesenchymal stromal cells (MSCs) and their extracellular vesicles (MSC-EVs) have demonstrated to elicit immunomodulatory and pro-regenerative properties that are beneficial for the treatment of chronic wounds. Thanks to different mediators, MSC-EVs have shown to play an important role in the proliferation, migration and cell survival of different skin cell populations. However, there is still a big bid to achieve the most effective, suitable and available source of MSC-EVs.

METHODS

We isolated, characterized and compared medium-large EVs (m-lEVs) and small EVs (sEVs) obtained from hair follicle-derived MSCs (HF-MSCs) against the gold standard in regenerative medicine, EVs isolated from adipose tissue-derived MSCs (AT-MSCs).

RESULTS

We demonstrated that HF-EVs, as well as AT-EVs, expressed typical MSC-EVs markers (CD9, CD44, CD63, CD81 and CD105) among other different functional markers. We showed that both cell types were able to increase human dermal fibroblasts (HDFs) proliferation and migration. Moreover, both MSC-EVs were able to increase angiogenesis in human umbilical vein endothelial cells (HUVECs) and protect HDFs exposed to a hyperglycemic environment from oxidative stress and cytotoxicity.

CONCLUSIONS

Taken together, HF-EVs demonstrated to exhibit comparable potential to that of AT-EVs as promising candidates in the treatment of chronic wounds.

Cell-based dressings: A journey through chronic wound management

The field of regenerative medicine has undergone a paradigm shift in recent decades thanks to the emergence of novel therapies based on the use of living organisms. The development of cell-based strategies has become a trend for the treatment of different conditions and pathologies. In this sense, the need for more adequate, biomimetic and well-planned treatments for chronic wounds has found different and innovative strategies, based on the combination of cells with dressings, which seek to revolutionize the wound healing management. Therefore, the objective of this review is to analyze the current state and the latest advances in the research of cell-based dressings for chronic wounds, ranging from traditional and "second generation" bioengineered living skin equivalents to mesenchymal stem cell dressings; the latter include biopolymeric porous scaffolds, electrospun nanofiber meshes, hydrogels and 3D printed bio-printed dressings. Finally, this review updates the completed and ongoing clinical trials in this field and encourages researchers to rethink these new approaches, manufacturing processes and mechanisms of action, as well as their administration strategies and timings.

Green hemostatic sponge-like scaffold composed of soy protein and chitin for the treatment of epistaxis

Epistaxis is one of the most common otorhinolaryngology emergencies worldwide. Although there are currently several treatments available, they present several disadvantages. This, in addition to the increasing social need of being environmentally respectful, led us to investigate whether a sponge-like scaffold (SP–CH) produced from natural by-products of the food industry — soy protein and β-chitin — can be employed as a nasal pack for the treatment of epistaxis. To evaluate the potential of our material as a nasal pack, it was compared with two of the most commonly used nasal packs in the clinic: a basic gauze and the gold standard Merocel®. Our SP-CH presented great physicochemical and mechanical properties, lost weight in aqueous medium, and could even partially degrade when incubated in blood. It was shown to be both biocompatible and hemocompatible in vitro, clearing up any doubt about its safety. It showed increased blood clotting capacity in vitro, as well as increased capacity to bind both red blood cells and platelets, compared to the standard gauze and Merocel®. Finally, a rat-tail amputation model revealed that our SP-CH could even reduce bleeding time in vivo. This work, carried out from a circular economy approach, demonstrates that a green strategy can be followed to manufacture nasal packs using valorized by-products of the food industry, with equal or even better hemostatic properties than the gold standard in the clinic.

Dual effect of TAT functionalized DHAH lipid nanoparticles with neurotrophic factors in human BBB and microglia cultures

Background

Neurodegenerative diseases (NDs) are an accelerating global health problem. Nevertheless, the stronghold of the brain- the blood–brain barrier (BBB) prevents drug penetrance and dwindles effective treatments. Therefore, it is crucial to identify Trojan horse-like drug carriers that can effectively cross the blood–brain barrier and reach the brain tissue. We have previously developed polyunsaturated fatty acids (PUFA)-based nanostructured lipid carriers (NLC), namely DHAH-NLC. These carriers are modulated with BBB-permeating compounds such as chitosan (CS) and trans-activating transcriptional activator (TAT) from HIV-1 that can entrap neurotrophic factors (NTF) serving as nanocarriers for NDs treatment. Moreover, microglia are suggested as a key causative factor of the undergoing neuroinflammation of NDs. In this work, we used in vitro models to investigate whether DHAH-NLCs can enter the brain via the BBB and investigate the therapeutic effect of NTF-containing DHAH-NLC and DHAH-NLC itself on lipopolysaccharide-challenged microglia.

Methods

We employed human induced pluripotent stem cell-derived brain microvascular endothelial cells (BMECs) to capitalize on the in vivo-like TEER of this BBB model and quantitatively assessed the permeability of DHAH-NLCs. We also used the HMC3 microglia cell line to assess the therapeutic effect of NTF-containing DHAH-NLC upon LPS challenge.

Results

TAT-functionalized DHAH-NLCs successfully crossed the in vitro BBB model, which exhibited high transendothelial electrical resistance (TEER) values (≈3000 Ω*cm²). Specifically, the TAT-functionalized DHAH-NLCs showed a permeability of up to 0.4% of the dose. Furthermore, using human microglia (HMC3), we demonstrate that DHAH-NLCs successfully counteracted the inflammatory response in our cultures after LPS challenge. Moreover, the encapsulation of glial cell-derived neurotrophic factor (GNDF)-containing DHAH-NLCs (DHAH-NLC-GNDF) activated the Nrf2/HO-1 pathway, suggesting the triggering of the endogenous anti-oxidative system present in microglia.

Conclusions

Overall, this work shows that the TAT-functionalized DHAH-NLCs can cross the BBB, modulate immune responses, and serve as cargo carriers for growth factors; thus, constituting an attractive and promising novel drug delivery approach for the transport of therapeutics through the BBB into the brain.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-022-00315-1.

Human Hair Follicle-Derived Mesenchymal Stromal Cells from the Lower Dermal Sheath as a Competitive Alternative for Immunomodulation

Mesenchymal stromal cells (MSCs) have unique immunomodulatory capacities. We investigated hair follicle-derived MSCs (HF-MSCs) from the dermal sheath, which are advantageous as an alternative source because of their relatively painless and minimally risky extraction procedure. These cells expressed neural markers upon isolation and maintained stemness for a minimum of 10 passages. Furthermore, HF-MSCs showed responsiveness to pro-inflammatory environments by expressing type-II major histocompatibility complex antigens (MHC)-II to a lesser extent than adipose tissue-derived MSCs (AT-MSCs). HF-MSCs effectively inhibited the proliferation of peripheral blood mononuclear cells equivalently to AT-MSCs. Additionally, HF-MSCs promoted the induction of CD4+CD25+FOXP3+ regulatory T cells to the same extent as AT-MSCs. Finally, HF-MSCs, more so than AT-MSCs, skewed M0 and M1 macrophages towards M2 phenotypes, with upregulation of typical M2 markers CD163 and CD206 and downregulation of M1 markers such as CD64, CD86, and MHC-II. Thus, we conclude that HF-MSCs are a promising source for immunomodulation.

Mesenchymal Stromal Cell Secretome for the Treatment of Immune-Mediated Inflammatory Diseases: Latest Trends in Isolation, Content Optimization and Delivery Avenues

Considering the high prevalence and the complex pharmacological management of immune-mediated inflammatory diseases (IMIDs), the search for new therapeutic approaches for their treatment is vital. Although the immunomodulatory and anti-inflammatory effects of mesenchymal stromal cells (MSCs) have been extensively studied as a potential therapy in this field, direct MSC implantation presents some limitations that could slow down the clinical translation. Since the beneficial effects of MSCs have been mainly attributed to their ability to secrete a plethora of bioactive factors, their secretome has been proposed as a new and promising pathway for the treatment of IMIDs. Formed from soluble factors and extracellular vesicles (EVs), the MSC-derived secretome has been proven to elicit immunomodulatory effects that control the inflammatory processes that occur in IMIDs. This article aims to review the available knowledge on the MSC secretome, evaluating the advances in this field in terms of its composition, production and application, as well as analyzing the pending challenges in the field. Moreover, the latest research involving secretome administration in IMIDs is discussed to provide an updated state-of-the-art for this field. Finally, novel secretome delivery alternatives are reviewed, paying special attention to hydrogel encapsulation as one of the most convenient and promising strategies.

Immunomodulatory Biomaterials for Tissue Repair

All implanted biomaterials are targets of the host's immune system. While the host inflammatory response was once considered a detrimental force to be blunted or avoided, in recent years, it has become a powerful force to be leveraged to augment biomaterial-tissue integration and tissue repair. In this review, we will discuss the major immune cells that mediate the inflammatory response to biomaterials, with a focus on how biomaterials can be designed to modulate immune cell behavior to promote biomaterial-tissue integration. In particular, the intentional activation of monocytes and macrophages with controlled timing, and modulation of their interactions with other cell types involved in wound healing, have emerged as key strategies to improve biomaterial efficacy. To this end, careful design of biomaterial structure and controlled release of immunomodulators can be employed to manipulate macrophage phenotype for the maximization of the wound healing response with enhanced tissue integration and repair, as opposed to a typical foreign body response characterized by fibrous encapsulation and implant isolation. We discuss current challenges in the clinical translation of immunomodulatory biomaterials, such as limitations in the use of in vitro studies and animal models to model the human immune response. Finally, we describe future directions and opportunities for understanding and controlling the biomaterial-immune system interface, including the application of new imaging tools, new animal models, the discovery of new cellular targets, and novel techniques for in situ immune cell reprogramming.

Cell microencapsulation technologies for sustained drug delivery: Latest advances in efficacy and biosafety

The development of cell microencapsulation systems began several decades ago. However, today few systems have been tested in clinical trials. For this reason, in the last years, researchers have directed efforts towards trying to solve some of the key aspects that still limit efficacy and biosafety, the two major criteria that must be satisfied to reach the clinical practice. Regarding the efficacy, which is closely related to biocompatibility, substantial improvements have been made, such as the purification or chemical modification of the alginates that normally form the microspheres. Each of the components that make up the microcapsules has been carefully selected to avoid toxicities that can damage the encapsulated cells or generate an immune response leading to pericapsular fibrosis. As for the biosafety, researchers have developed biological circuits capable of actively responding to the needs of the patients to precisely and accurately release the demanded drug dose. Furthermore, the structure of the devices has been subject of study to adequately protect the encapsulated cells and prevent their spread in the body. The objective of this review is to describe the latest advances made by scientist to improve the efficacy and biosafety of cell microencapsulation systems for sustained drug delivery, also highlighting those points that still need to be optimized.

3D Bioprinting of Functional Skin Substitutes: From Current Achievements to Future Goals

The aim of this review is to present 3D bioprinting of skin substitutes as an efficient approach of managing skin injuries. From a clinical point of view, classic treatments only provide physical protection from the environment, and existing engineered scaffolds, albeit acting as a physical support for cells, fail to overcome needs, such as neovascularisation. In the present work, the basic principles of bioprinting, together with the most popular approaches and choices of biomaterials for 3D-printed skin construct production, are explained, as well as the main advantages over other production methods. Moreover, the development of this technology is described in a chronological manner through examples of relevant experimental work in the last two decades: from the pioneers Lee et al. to the latest advances and different innovative strategies carried out lately to overcome the well-known challenges in tissue engineering of skin. In general, this technology has a huge potential to offer, although a multidisciplinary effort is required to optimise designs, biomaterials and production processes.

Characterization of Bio-Inspired Electro-Conductive Soy Protein Films

Protein-based conductive materials are gaining attention as alternative components of electronic devices for value-added applications. In this regard, soy protein isolate (SPI) was processed by extrusion in order to obtain SPI pellets, subsequently molded into SPI films by hot pressing, resulting in homogeneous and transparent films, as shown by scanning electron microscopy and UV-vis spectroscopy analyses, respectively. During processing, SPI denatured and refolded through intermolecular interactions with glycerol, causing a major exposition of tryptophan residues and fluorescence emission, affecting charge distribution and electron transport properties. Regarding electrical conductivity, the value found (9.889 × 10⁻⁴ S/m) is characteristic of electrical semiconductors, such as silicon, and higher than that found for other natural polymers. Additionally, the behavior of the films in contact with water was analyzed, indicating a controlled swelling and a hydrolytic surface, which is of great relevance for cell adhesion and spreading. In fact, cytotoxicity studies showed that the developed SPI films were biocompatible, according to the guidelines for the biological evaluation of medical devices. Therefore, these SPI films are uniquely suited as bioelectronics because they conduct both ionic and electronic currents, which is not accessible for the traditional metallic conductors.

3D encapsulation and inflammatory licensing of mesenchymal stromal cells alter the expression of common reference genes used in real-time RT-qPCR

Human mesenchymal stromal cells (hMSCs) hold great promise in the treatment of inflammatory and immune diseases, due to their immunomodulatory capacity. Their therapeutic activity is often assessed measuring levels of expression of immunomodulatory genes such as indoleamine 2,3-dioxygenase 1 (IDO1) and real-time RT-qPCR is most predominantly the method of choice due to its high sensitivity and relative simplicity. Currently, multiple strategies are explored to promote hMSC-mediated immunomodulation, overlooking the effects they pose in the expression of genes commonly used as internal calibrators in real-time RT-qPCR analyses. However, variations in their expression could introduce significant errors in the evaluation of the therapeutic potential of hMSCs. This work investigates, for the first time, how some of these strategies - 3D encapsulation, the mechanical properties of the 3D matrix and inflammatory licensing - influence the expression of common reference genes in hMSCs. Both 3D encapsulation and inflammatory licensing alter significantly the expression of β-actin (ACTB) and Ubiquitin C (UBC), respectively. Using them as normalization factors leads to an erroneous assessment of IDO1 mRNA levels, therefore resulting in over or underestimation of the therapeutic potential of hMSCs. In contrast, the range of mechanical properties of the matrix encapsulating the cells did not significantly affect the expression of any of the reference genes studied. Moreover, we identify RPS13 and RPL30 as reference genes of choice under these particular experimental conditions. These results demonstrate the vital importance of validating the expression of reference genes to correctly assess the therapeutic potential of hMSCs by real-time RT-qPCR.

Cell microencapsulation technologies for sustained drug delivery: Clinical trials and companies

In recent years, cell microencapsulation technology has advanced, mainly driven by recent developments in the use of stem cells or the optimization of biomaterials. Old challenges have been addressed from new perspectives, and systems developed and improved for decades are now being transferred to the market by novel start-ups and consolidated companies. These products are mainly intended for the treatment of diabetes mellitus (DM), but also cancer, central nervous system (CNS) disorders or lysosomal diseases, among others. In this review, we analyze the results obtained in clinical trials to date and define the global key players that will lead the cell microencapsulation market to bring this technology to the clinic in the future.

Nanostructured Lipid Carriers Made of Ω-3 Polyunsaturated Fatty Acids: In Vitro Evaluation of Emerging Nanocarriers to Treat Neurodegenerative Diseases

Neurodegenerative diseases (ND) are one of the main problems of public health systems in the 21st century. The rise of nanotechnology-based drug delivery systems (DDS) has become in an emerging approach to target and treat these disorders related to the central nervous system (CNS). Among others, the use of nanostructured lipid carriers (NLCs) has increased in the last few years. Up to today, most of the developed NLCs have been made of a mixture of solid and liquid lipids without any active role in preventing or treating diseases. In this study, we successfully developed NLCs made of a functional lipid, such as the hydroxylated derivate of docohexaenoic acid (DHAH), named DHAH-NLCs. The newly developed nanocarriers were around 100 nm in size, with a polydispersity index (PDI) value of <0.3, and they exhibited positive zeta potential due to the successful chitosan (CS) and TAT coating. DHAH-NLCs were shown to be safe in both dopaminergic and microglia primary cell cultures. Moreover, they exhibited neuroprotective effects in dopaminergic neuron cell cultures after exposition to 6-hydroxydopamine hydrochloride (6-OHDA) neurotoxin and decreased the proinflammatory cytokine levels in microglia primary cell cultures after lipopolysaccharide (LPS) stimuli. The levels of the three tested cytokines, IL-6, IL-1β and TNF-α were decreased almost to control levels after the treatment with DHAH-NLCs. Taken together, these data suggest the suitability of DHAH-NLCs to attaining enhanced and synergistic effects for the treatment of NDs.

Multifunctional biomimetic hydrogel systems to boost the immunomodulatory potential of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) hold great therapeutic potential, in part because of their immunomodulatory properties. However, these properties can be transient and depend on multiple factors. Here, we developed a multifunctional hydrogel system to synergistically enhance the immunomodulatory properties of MSCs, using a combination of sustained inflammatory licensing and three-dimensional (3D) encapsulation in hydrogels with tunable mechanical properties. The immunomodulatory extracellular matrix hydrogels (iECM) consist of an interpenetrating network of click functionalized-alginate and fibrillar collagen, in which interferon γ (IFN-γ) loaded heparin-coated beads are incorporated. The 3D microenvironment significantly enhanced the expression of a wide panel of pivotal immunomodulatory genes in bone marrow-derived primary human MSCs (hMSCs), compared to two-dimensional (2D) tissue culture. Moreover, the inclusion of IFN-γ loaded heparin-coated beads prolonged the expression of key regulatory genes upregulated upon licensing, including indoleamine 2,3-dioxygenase 1 (IDO1) and galectin-9 (GAL9). At a protein level, iECM hydrogels enhanced the secretion of the licensing responsive factor Gal-9 by hMSCs. Its presence in hydrogel conditioned media confirmed the correct release and diffusion of the factors secreted by hMSCs from the system. Furthermore, co-culture of iECM-encapsulated hMSCs and activated human T cells resulted in suppressed proliferation, demonstrating direct regulation on immune cells. These data highlight the potential of iECM hydrogels to enhance the immunomodulatory properties of hMSCs in cell therapies.

In vitro and in vivo antimicrobial activity of sodium colistimethate and amikacin-loaded nanostructured lipid carriers (NLC)

Sodium colistimethate (SCM) and amikacin (AMK) are among the few antibiotics effective against resistant P. aeruginosa, K. pneumoniae and A. baumannii; however, their toxicity severely limits their use. Enclosing antibiotics into nanostructured lipid carriers (NLC) might decrease drug toxicity and improve antibiotic disposition. In this work, SCM or AMK was loaded into different NLC formulations, through high pressure homogenization, and their in vitro and in vivo effectiveness was analyzed. The encapsulation process did not reduce drug effectiveness since in vitro SCM-NLC and AMK-NLC drug activity was equal to that of the free drugs. As cryoprotectant, trehalose showed better properties than dextran. Instead, positive chitosan coating was discarded due to its limited cost-efficiency. Finally, the in vivo study in acute pneumonia model revealed that intraperitoneal administration was superior to the intramuscular route and confirmed that (-) SCM-NLC with trehalose, was the most suitable formulation against an extensively drug-resistant A. baumannii strain.

Structure-properties relationship of chitosan/collagen films with potential for biomedical applications

Chitosan/collagen films were developed and characterized in order to assess the suitability of these films for biomedical applications. Hence, physicochemical, thermal, barrier and mechanical properties were analyzed and related to the film structure, which showed the prevalence of the triple helix of native collagen after the addition of chitosan. Furthermore, collagen fiber diameter changed from 3.9 ± 0.6 μm, for collagen films without chitosan, to 1.8 ± 0.5 μm, for collagen films with low molecular weight chitosan. These results suggested interactions between collagen and chitosan molecules, as observed by Fourier transform infrared (FTIR) analysis. Regarding film barrier properties, chitosan/collagen films showed a water vapor transmission rate around 1174 g m^-2 day^-1, suitable for biomedical applications such as wound healing. Additionally, biological tests confirmed that the chitosan/collagen films developed are suitable for biomedical applications.

Mesenchymal stromal cell based therapies for the treatment of immune disorders: recent milestones and future challenges

Introduction: Mesenchymal stromal cells (MSCs) present unique immunomodulatory properties that make them promising candidates for the treatment of inflammatory and immune disorders. MSC-mediated immunomodulation is a complex combination of mechanisms, in which the secretome plays a fundamental role. The plethora of bioactive molecules MSCs produce, such as indoleamine 2,3-dioxygenase (IDO) or prostaglandin E2 (PGE2), efficiently regulates innate and adaptive immunity. As a result, MSCs have been extensively employed in preclinical studies, leading to the conduction of multiple clinical trials.Areas covered: This review summarizes the effects of some of the key biomolecules in the MSC secretome and the advances in preclinical studies exploring the treatment of disorders including graft-versus-host disease (GvHD) or inflammatory bowel disease (IBD). Further, late-stage clinical trials and the first MSC-based therapies that recently obtained regulatory approval are discussed.Expert opinion: Extensive research supports the potential of MSC-based immunomodulatory therapies. However, to establish the bases for clinical translation, the future of study lies in the standardization of protocols and in the development of strategies that boost the therapeutic properties of MSCs.

Clinical Applications of Cell Encapsulation Technology

Cell encapsulation comprises immunoisolation three-dimensional systems for housing therapeutic cells that secrete bioactive compounds de novo and in a sustained manner. This allows transplantation of multiple allo- or xenogeneic cells without the aid of immunosuppressant drugs. Recent advances in the field have provided improvements to these cell-based drug delivery systems, which have gained the attention of the scientific community and inspired many biotechnological companies to develop their own product candidates. From micro- to macroencapsulation devices, this chapter describes some of the most important approaches that are being currently tested in late-stage clinical trials and are likely to reach the market as future game changers. Most studies involve the treatment of diabetes, eye disorders, and diseases of the central nervous system. However, many other pathologies are also amenable to benefit from this technology. Latest advances to overcome major pending challenges related to biosafety and efficacy are also discussed.

Force spectroscopy-based simultaneous topographical and mechanical characterization to study polymer-to-polymer interactions in coated alginate microspheres

Cell-laden hydrogel microspheres have shown encouraging outcomes in the fields of drug delivery, tissue engineering or regenerative medicine. Beyond the classical single coating with polycations, many other different coating designs have been reported with the aim of improving mechanical properties and in vivo performance of the microspheres. Among the most common strategies are the inclusion of additional polycation coatings and the covalent bonding of the semi-permeable membranes with biocompatible crosslinkers such as genipin. However, it remains challenging to characterize the effects of the interactions between the polycations and the hydrogel microspheres over time in vitro. Here we use a force spectroscopy-based simultaneous topographical and mechanical characterization to study polymer-to-polymer interactions in alginate microspheres with different coating designs, maintaining the hydrogels in liquid. In addition to classical topography parameters, we explored, for the first time, the evolution of peak/valley features along the z axis via thresholding analysis and the cross-correlation between topography and stiffness profiles with resolution down to tens of nanometers. Thus, we demonstrated the importance of genipin crosslinking to avoid membrane detachment in alginate microspheres with double polycation coatings. Overall, this methodology could improve hydrogel design rationale and expedite in vitro characterization, therefore facilitating clinical translation of hydrogel-based technologies.

Development of Bioinspired Gelatin and Gelatin/Chitosan Bilayer Hydrofilms for Wound Healing

In the current study, we developed a novel gelatin-based bilayer wound dressing. We used different crosslinking agents to confer unique properties to each layer, obtaining a bioinspired multifunctional hydrofilm suitable for wound healing. First, we produced a resistant and non-degradable upper layer by lactose-mediated crosslinking of gelatin, which provided mechanical support and protection to overall design. For the lower layer, we crosslinked gelatin with citric acid, resulting in a porous matrix with a great swelling ability. In addition, we incorporated chitosan into the lower layer to harness its wound healing ability. FTIR and SEM analyses showed that lactose addition changed the secondary structure of gelatin, leading to a more compact and smoother structure than that obtained with citric acid. The hydrofilm was able to swell 384.2 ± 57.2% of its dry weight while maintaining mechanical integrity. Besides, its water vapour transmission rate was in the range of commercial dressings (1381.5 ± 108.6 g/m2·day). In vitro, cytotoxicity assays revealed excellent biocompatibility. Finally, the hydrofilm was analysed through an ex vivo wound healing assay in human skin. It achieved similar results to the control in terms of biocompatibility and wound healing, showing suitable characteristics to be used as a wound dressing.

Monitoring implantable immunoisolation devices with intrinsic fluorescence of genipin

Imaging of implanted hydrogel-based biosystems usually requires indirect labeling of the vehicle or cargo, adding complexity and potential risk of altering functionality. Here, for the first time, it is reported that incorporation of genipin into the design of immunoisolation devices can be harnessed for in vivo imaging. Using cell-compatible in situ cross-linking reactions, a fast, efficient and noncytotoxic procedure is shown to maximize fluorescence of microcapsules. Moreover, genipin is validated as a quantitative imaging probe by injecting increasing doses of microcapsules in the subcutaneous space of mice, obtaining strong, stable fluorescence with good linearity of signal to microcapsule dose over several weeks. This allows immediate assessment of the actual injected dose and monitoring of its position over time, thereby significantly enhancing the efficacy and biosafety of the therapy. These outcomes may facilitate clinical translation and optimize medical applications of multiple hydrogel-based biotechnologies.

Safety and effectiveness of sodium colistimethate-loaded nanostructured lipid carriers (SCM-NLC) against P. aeruginosa: in vitro and in vivo studies following pulmonary and intramuscular administration

The usefulness of nanotechnology to increase the bioavailability of drugs and decrease their toxicity may be a tool to deal with multiresistant P. aeruginosa (Mr-Pa) respiratory infections. We describe the preparation and the in vivo efficacy and safety of sodium colistimethate-loaded nanostructured lipid carriers (SCM-NLC) by the pulmonary and intramuscular routes. Nanoparticles showed 1-2 mg/L minimum inhibitory concentration against eight extensively drug-resistant P. aeruginosa strains. In vivo, SCM-NLC displayed significantly lower CFU/g lung than the saline and similar to that of the free SCM, even the dose in SCM-NLC group was lower than free SCM. There was no tissue damage related to the treatments. Biodistribution assessments showed a mild systemic absorption after nebulization and a notorious absorption after IM route. Altogether, it could be concluded that SCM-NLC were effective against P. aeruginosa in vivo, not toxic and distribute efficiently to the lung and liver after pulmonary or intramuscular administrations.

Cell Microencapsulation and Cryopreservation with Low Molecular Weight Hyaluronan and Dimethyl Sulfoxide

Cryopreservation is commonly used for the storage of cells, tissues, organs or 3D cell-based products using ultra-low temperatures, which involves the immersion in liquid nitrogen for their long-term preservation. The cryopreservation of several microencapsulated cells is usually performed by the slow freezing with the dimethyl sulfoxide (DMSO) as a cryoprotectant agent (CPA). In this study, we cryopreserved several microencapsulated cells with the natural, non-toxic low molecular-weight hyaluronan (LMW-HA) at 5% and DMSO 10% solution assessing cell viability and metabolic activity after thawing. The cryopreservation of microencapsulated D1 mesenchymal stem cells (D1MSC) and murine myoblast cells (C2C12) with the LMW-HA 5% presented similar outcomes after thawing compared to the DMSO solution, showing the low molecular weight hyaluronan as a natural, non-toxic CPA that can be used preventing the DMSO related adverse effects after the implantation of the cryopreserved cell-based products.

Beneficial effects of n-3 polyunsaturated fatty acids administration in a partial lesion model of Parkinson's disease: The role of glia and NRf2 regulation

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been widely associated to beneficial effect over different neurodegenerative diseases. In the present study, we tested the potential therapeutic effect of docohexanoic acid (DHA) and its hydroxylated derivate, DHAH, in a partial lesion model of Parkinson's disease (PD). One month before and four months after the striatal lesion with 6-OHDA was made, the animals were daily treated with DHA (50 mg/kg), DHAH (50 mg/kg), vehicle or saline, by intragastric administration. Animal groups under n-3 PUFA treatments exhibited a trend to improve in amphetamine-induced rotations and cylinder test. The beneficial effect seen in behavioral studies were confirmed with TH immunostaining. TH⁺ fibers and TH⁺ neurons increased in the experimental groups treated with both n-3 PUFAs, DHA and DHAH. Moreover, the n-3 PUFAs administration decreased the astrogliosis and microgliosis, in both the striatum and substantia nigra (SN), with a higher decrease of GFAP⁺ and Iba-1⁺ cells for the DHAH treated group. This experimental group also revealed a positive effect on Nrf2 pathway regulation, decreasing the positive Nrf2 immmunostaining in the striatum and SN, which revealed a potential antioxidant effect of this compound. Taking together, these data suggest a positive effect of n-3 PUFAs administration, and more concretely of DHAH, for PD treatment as it exhibited positive results on dopaminergic system, neuroinflammation and oxidative stress.

Low molecular-weight hyaluronan as a cryoprotectant for the storage of microencapsulated cells

The low-temperature storage of therapeutic cell-based products plays a crucial role in their clinical translation for the treatment of diverse diseases. Although dimethylsulfoxide (DMSO) is the most successful cryoprotectant in slow freezing of microencapsulated cells, it has shown adverse effects after cryopreserved cell-based products implantation. Therefore, the search of alternative non-toxic cryoprotectants for encapsulated cells is continuously investigated to move from bench to the clinic. In this work, we investigated the low molecular-weight hyaluronan (low MW-HA), a natural non-toxic and non-sulfated glycosaminoglycan, as an alternative non-permeant cryoprotectant for the slow freezing cryopreservation of encapsulated cells. Cryopreservation with low MW-HA provided similar metabolic activity, cell dead and early apoptotic cell percentage and membrane integrity after thawing, than encapsulated cells stored with either DMSO 10% or Cryostor 10. However, the beneficial outcomes with low MW-HA were not comparable to DMSO with some encapsulated cell types, such as the human insulin secreting cell line, 1.1B4, maybe explained by the different expression of the CD44 surface receptor. Altogether, we can conclude that low MW-HA represents a non-toxic natural alternative cryoprotectant to DMSO for the cryopreservation of encapsulated cells.

The role of osmolarity adjusting agents in the regulation of encapsulated cell behavior to provide a safer and more predictable delivery of therapeutics

Transplantation of cells within alginate microspheres has been extensively studied for sustained drug delivery. However, the lack of control over cell behavior represents a major concern regarding the efficacy and the safety of the therapy. Here, we demonstrated that when formulating the biosystem, an adequate selection of osmolarity adjusting agents significantly contributes to the regulation of cell responses. Our data showed that these agents interact in the capsule formation process, influencing the alginate crosslinking degree. Therefore, when selecting inert or electrolyte-based osmolarity adjusting agents to encapsulate D1 multipotent mesenchymal stromal cells (MSCs), alginate microcapsules with differing mechanical properties were obtained. Since mechanical forces acting on cells influence their behavior, contrasting cell responses were observed both, in vitro and in vivo. When employing mannitol as an inert osmolarity adjusting agent, microcapsules presented a more permissive matrix, allowing a tumoral-like behavior. This resulted in the formation of enormous cell-aggregates that presented necrotic cores and protruding peripheral cells, rendering the therapy unpredictable, dysfunctional, and unsafe. Conversely, the use of electrolyte osmolarity adjusting agents, including calcium or sodium, provided the capsule with a suitable crosslinking degree that established a tight control over cell proliferation and enabled an adequate therapeutic regimen in vivo. The crucial impact of these agents was confirmed when gene expression studies reported pivotal divergences not only in proliferative pathways, but also in genes involved in survival, migration, and differentiation. Altogether, our results prove osmolarity adjusting agents as an effective tool to regulate cell behavior and obtain safer and more predictable therapies.

Microencapsulated macrophages releases conditioned medium able to prevent epithelial to mesenchymal transition

Epithelial to mesenchymal transition (EMT) has emerged as a key process in the development of renal fibrosis. In fact, EMT-derived fibroblasts contribute to the progression of chronic renal disease. In addition, anti-inflammatory M2 macrophages have exhibited a great influence on renal fibrosis. However, because of the high impact that the inputs of different environmental cytokines have on their phenotype, macrophages can easily lose this property. We aim to known if microencapsulated macrophages on M2-inducing alginate matrices could preserve macrophage phenotype and thus release factors able to act on epithelial cells to prevent the epithelial differentiation towards mesenchymal cells. We reproduced an in vitro model of EMT by treating adipose-derived stem cells with all-trans retinoic acid (ATRA) and induced their transformation toward epithelia. Dedifferentiation of epithelial cells into a mesenchymal phenotype occurred when ATRA was retired, thus simulating EMT. Results indicate that induction of M2 phenotype by IL-10 addition in the alginate matrix produces anti-inflammatory cytokines and increases the metabolic activity and the viability of the encapsulated macrophages. The released conditioned medium modulates EMT and maintains healthy epithelial phenotype. This could be used for in vivo cell transplantation, or alternatively as an external releaser able to prevent epithelial to mesenchymal transformation for future anti-fibrotic therapies.

Ultra thin hydro-films based on lactose-crosslinked fish gelatin for wound healing applications

This study focuses on the development and characterization of an ultra thin hydro-film based on lactose-mediated crosslinking of fish gelatin by Maillard reaction. Lactose results in the only efficient crosslinker able to produce resistant to handling hydro-films when compared to conventional crosslinkers such as glutaraldehyde or genipin (tested at 25 and 37°C in phosphate buffer saline solution (PBS)).The disappearance of the peak related to the N-containing groups (XPS) and the images obtained by SEM and AFM demonstrate the highly ordered nano-scaled structure of lactose-crosslinked gelatin, confirming the crosslinking efficiency. This dressing presents high hydrophilicity and mild occlusivity, as shown by the swelling curve (max swelling at 5min) and by the occlusion factor of 25.17±0.99%, respectively. It demonstrates high stability to hydrolysis or cell-mediated degradation. Moreover, ISO 10993-5:2009 biocompatibility assay results in undetectable cytotoxicity effects. Spreading, adhesion and proliferation assays confirm the excellent adaptability of the cells onto the hydro-film surface without invading the dressing. Finally, the hydro-film enables the controlled delivery of therapeutic factors, such as the epidermal growth factor (EGF). This study demonstrates that lactose-mediated crosslinking is able to produce ultra thin gelatin hydro-films with suitable properties for biomedical applications, such as wound healing.

Enhanced Hippocampal Neurogenesis in APP/Ps1 Mouse Model of Alzheimer's Disease After Implantation of VEGF-loaded PLGA Nanospheres

During adult life, hippocampus is an important brain region involved in neurogenesis. The generation and cell death of newly generated neuronal cells in this region have critical roles in brain maintenance and alterations in these processes are seen in Alzheimer's disease (AD). For the purpose of carrying out a neuroregenerative strategy, we propose a novel approach based on the encapsulation of vascular endothelial growth factor (VEGF) in poly (lactic co-glycolic acid) (PLGA) biodegradable nanospheres (NS) administered by craniotomy to stimulate the proliferation of neuronal precursors in a transgenic mouse model of AD. VEGF loaded nanospheres were prepared by double emulsion solvent evaporation technique, obtaining 200 nm nanospheres with a biphasic release profile. After demonstrating their efficacy in the proliferation and differentiation of neuronal cell cultures, in vivo studies were carried out. 3 months after VEGF-NS were implanted directly into the cerebral cortex of APP/Ps1 mice, the determination of BrdU(+) cells in the whole hippocampal region and specifically in the dentate gyrus, demonstrated a significantly enhanced cellular proliferation in VEGF-NS treated group. These results were also confirmed showing an increased number of DCX(+) and NeuN(+) cells. Hence, PLGA-VEGF nanospheres may be a potential strategy to modulate proliferative neuronal progenitors in the hippocampal region, and therefore, provide new insight for future therapeutic approaches in AD.