Standardized Method to Functionalize Plasma-Extracellular Vesicles via Copper-Free Click Chemistry for Targeted Drug Delivery Strategies

Extracellular vesicles (EVs) have emerged as potential vehicles for targeted drug delivery and diagnostic applications. However, achieving consistent and reliable functionalization of EV membranes remains a challenge. Copper-catalyzed click chemistry, commonly used for EV surface modification, poses limitations due to cytotoxicity and interference with biological systems. To overcome these limitations, we developed a standardized method for functionalizing an EV membrane via copper-free click chemistry. EVs derived from plasma hold immense potential as diagnostic and therapeutic agents. However, the isolation and functionalization of EVs from such a complex biofluid represent considerable challenges. We compared three different EV isolation methods to obtain an EV suspension with an optimal purity/yield ratio, and we identified sucrose cushion ultracentrifugation (sUC) as the ideal protocol. We then optimized the reaction conditions to successfully functionalize the plasma-EV surface through a copper-free click chemistry strategy with a fluorescently labeled azide, used as a proof-of-principle molecule. Click-EVs maintained their identity, size, and, more importantly, capacity to be efficiently taken up by responder tumor cells. Moreover, once internalized, click EVs partially followed the endosomal recycling route. The optimized reaction conditions and characterization techniques presented in this study offer a foundation for future investigations and applications of functionalized EVs in drug delivery, diagnostics, and therapeutics.

Pilot study investigating BP-180 in extracellular vesicles derived from blister fluid of bullous pemphigoid patients

Bullous pemphigoid (BP) is an autoimmune blistering disease that targets the haemidesmosomal proteins, mainly BP180. Extracellular vesicles (EVs) have been demonstrated to carry tissue-specific autoantigens in the setting of autoimmune diseases and transplant organ rejection; this phenomenon was demonstrated to have pathogenic implications in autoimmune diseases and to correlate with transplant rejection severity. The purpose of this study was to identify the presence of BP targeted autoantigens in blister fluid derived EVs. We isolated, by size exclusion chromatography, EVs derived from blisters of BP-patients and from suction blisters of healthy donors. EV characterization was performed by flow cytometry and nanoparticle tracking analysis. Western blot analysis was used to investigate the presence of autoantigens. A suspension enriched in EVs was efficiently obtained from blister fluid from patients and healthy donors. EV-enriched fractions were enriched in particles with a size distribution characterizing small-EVs (main peak was present at 94.5 nm). BP180 was found, by western blot analysis, in EVs derived from blister fluid of 3 out 6 BP patients and in none of EVs isolated from suction blister fluid of healthy donors. BP230 and Dsg1 were not detectable in EVs of any of the samples. No specific clinical characteristics seemed to correlate to the presence of BP180 in EVs. The discovery of BP180 in EVs derived from blister fluid might help understanding BP pathogenesis.

Investigating the Paracrine Role of Perinatal Derivatives: Human Amniotic Fluid Stem Cell-Extracellular Vesicles Show Promising Transient Potential for Cardiomyocyte Renewal

Cardiomyocyte renewal represents an unmet clinical need for cardiac regeneration. Stem cell paracrine therapy has attracted increasing attention to resurge rescue mechanisms within the heart. We previously characterized the paracrine effects that human amniotic fluid–derived stem cells (hAFSC) can exert to provide cardioprotection and enhance cardiac repair in preclinical models of myocardial ischemia and cardiotoxicity. Here, we analyze whether hAFSC secretome formulations, namely, hAFSC conditioned medium (hAFSC-CM) over extracellular vesicles (hAFSC-EVs) separated from it, can induce cardiomyocyte renewal. c-KIT+ hAFSC were obtained by leftover samples of II trimester prenatal amniocentesis (fetal hAFSC) and from clinical waste III trimester amniotic fluid during scheduled C-section procedures (perinatal hAFSC). hAFSC were primed under 1% O₂ to enrich hAFSC-CM and EVs with cardioactive factors. Neonatal mouse ventricular cardiomyocytes (mNVCM) were isolated from cardiac tissue of R26pFUCCI2 mice with cell cycle fluorescent tagging by mutually exclusive nuclear signal. mNVCM were stimulated by fetal versus perinatal hAFSC-CM and hAFSC-EVs to identify the most promising formulation for in vivo assessment in a R26pFUCCI2 neonatal mouse model of myocardial infarction (MI) via intraperitoneal delivery. While the perinatal hAFSC secretome did not provide any significant cardiogenic effect, fetal hAFSC-EVs significantly sustained mNVCM transition from S to M phase by 2-fold, while triggering cytokinesis by 4.5-fold over vehicle-treated cells. Treated mNVCM showed disorganized expression of cardiac alpha-actinin, suggesting cytoskeletal re-arrangements prior to cell renewal, with a 40% significant downregulation of Cofilin-2 and a positive trend of polymerized F-Actin. Fetal hAFSC-EVs increased cardiomyocyte cell cycle progression by 1.8-fold in the 4-day-old neonatal left ventricle myocardium short term after MI; however, such effect was lost at the later stage. Fetal hAFSC-EVs were enriched with a short isoform of Agrin, a mediator of neonatal heart regeneration acting by YAP-related signaling; yet in vitro application of YAP inhibitor verteporfin partially affected EV paracrine stimulation on mNVCM. EVs secreted by developmentally juvenile fetal hAFSC can support cardiomyocyte renewal to some extension, via intercellular conveyance of candidates possibly involving Agrin in combination with other factors. These perinatal derivative promising cardiogenic effects need further investigation to define their specific mechanism of action and enhance their potential translation into therapeutic opportunity.

Targeting PIK3CA Actionable Mutations in the Circulome: A Proof of Concept in Metastatic Breast Cancer

The study of circulating cancer-derived components (circulome) is considered the new frontier of liquid biopsy. Despite the recognized role of circulome biomarkers, their comparative molecular profiling is not yet routine. In advanced breast cancer (BC), approximately 40% of hormone-receptor-positive, HER2-negative BC cases harbor druggable PIK3CA mutations suitable for combined alpelisib/fulvestrant treatment. This pilot study investigates PIK3CA mutations in circulating tumor DNA (ctDNA), tumor cells (CTCs), and extracellular vesicles (EVs) with the aim of determining which information on molecular targetable profiling could be recollected in each of them. The in-depth molecular analysis of four BC patients demonstrated, as a proof-of-concept study, that it is possible to retrieve mutational information in the three components. Patient-specific PIK3CA mutations were found in both tissue and ctDNA and in 3/4 cases, as well as in CTCs, in the classical population (large-sized CD45−/EpCAM+/− cells), and/or in the “non-conventional” sub-population (smaller-sized CD44+/EpCAM−/CD45− cells). Consistent mutational profiles of EVs with CTCs suggest that they may have been released by CTCs. This preliminary evidence on the molecular content of the different circulating biomaterials suggests their possible function as a mirror of the intrinsic heterogeneity of BC. Moreover, this study demonstrates, through mutational assessment, the tumor origin of the different CTC sub-populations sustaining the translational value of the circulome for a more comprehensive picture of the disease.

Circulating miRNAs in Breast Cancer Diagnosis and Prognosis

Great improvement has been made in the diagnosis and therapy of breast cancer patients. However, the identification of biomarkers for early diagnosis, prognosis, therapy assessment and monitoring, including drug resistance and the early detection of micro-metastases, is still lacking. Recently, circulating microRNAs (miRNAs), circulating freely in the blood stream or entrapped in extracellular vesicles (EVs), have been shown to have a potential diagnostic, prognostic or predictive power. In this review, recent findings are summarized, both at a preclinical and clinical level, related to miRNA applicability in the context of breast cancer. Different aspects, including clinical and technical challenges, are discussed, describing the potentialities of miRNA use in breast cancer. Even though more methodological standardized studies conducted in larger and selected patient cohorts are needed to support the effective clinical utility of miRNA as biomarkers, they could represent novel and accessible tools to be transferred into clinical practice.

Small Extracellular Vesicles from Human Amniotic Fluid Samples as Promising Theranostics

Since the first evidence that stem cells can provide pro-resolving effects via paracrine secretion of soluble factors, growing interest has been addressed to define the most ideal cell source for clinical translation. Leftover or clinical waste samples of human amniotic fluid obtained following prenatal screening, clinical intervention, or during scheduled caesarean section (C-section) delivery at term have been recently considered an appealing source of mesenchymal progenitors with peculiar regenerative capacity. Human amniotic fluid stem cells (hAFSC) have been demonstrated to support tissue recovery in several preclinical models of disease by exerting paracrine proliferative, anti-inflammatory and regenerative influence. Small extracellular vesicles (EVs) concentrated from the hAFSC secretome (the total soluble trophic factors secreted in the cell-conditioned medium, hAFSC-CM) recapitulate most of the beneficial cell effects. Independent studies in preclinical models of either adult disorders or severe diseases in newborns have suggested a regenerative role of hAFSC-EVs. EVs can be eventually concentrated from amniotic fluid (hAF) to offer useful prenatal information, as recently suggested. In this review, we focus on the most significant aspects of EVs obtained from either hAFSC and hAF and consider the current challenges for their clinical translation, including isolation, characterization and quantification methods.

The Human Fetal and Adult Stem Cell Secretome Can Exert Cardioprotective Paracrine Effects against Cardiotoxicity and Oxidative Stress from Cancer Treatment

Simple Summary

Anthracyclines, such as doxorubicin (Dox), are an important class of chemotherapeutic drugs. However, their use is hampered by the risk of developing heart failure. The aim of this study was to assess and compare the cardioprotective effects exerted by a set of factors, collectively named secretomes, secreted by either adult or fetal human stem cells. Both secretome formulations were effective in counteracting Dox-induced apoptosis and mitochondrial impairment in cardiomyocytes and cardiac fibroblasts. In vivo experiments in a mouse model of Dox-induced cardiomyopathy (DIC) indicated that early administration of both secretomes during Dox treatment exerted beneficial long-term effects, preserving cardiac function and body mass. These findings suggest that the stem cell secretome could represent a feasible option for future paracrine cardioprotective therapy against Dox-related cardiotoxicity during cancer treatment.

Abstract

Cardiovascular side effects are major shortcomings of cancer treatments causing cardiotoxicity and late-onset cardiomyopathy. While doxorubicin (Dox) has been reported as an effective chemotherapy agent, unspecific impairment in cardiomyocyte mitochondria activity has been documented. We demonstrated that the human fetal amniotic fluid-stem cell (hAFS) secretome, namely the secreted paracrine factors within the hAFS-conditioned medium (hAFS-CM), exerts pro-survival effects on Dox-exposed cardiomyocytes. Here, we provide a detailed comparison of the cardioprotective potential of hAFS-CM over the secretome of mesenchymal stromal cells from adipose tissue (hMSC-CM). hAFS and hMSC were preconditioned under hypoxia to enrich their secretome. The cardioprotective effects of hAFS/hMSC-CM were evaluated on murine neonatal ventricular cardiomyocytes (mNVCM) and on their fibroblast counterpart (mNVFib), and their long-term paracrine effects were investigated in a mouse model of Dox-induced cardiomyopathy. Both secretomes significantly contributed to preserving mitochondrial metabolism within Dox-injured cardiac cells. hAFS-CM and hMSC-CM inhibited body weight loss, improved myocardial function, reduced lipid peroxidation and counteracted the impairment of mitochondrial complex I activity, oxygen consumption, and ATP synthesis induced by Dox. The hAFS and hMSC secretomes can be exploited for inhibiting cardiotoxic detrimental side effects of Dox during cancer therapy, thus ensuring cardioprotection via combinatorial paracrine therapy in association with standard oncological treatments.

Comprehensive Profiling of Secretome Formulations from Fetal- and Perinatal Human Amniotic Fluid Stem Cells

We previously reported that c-KIT+ human amniotic-fluid derived stem cells obtained from leftover samples of routine II trimester prenatal diagnosis (fetal hAFS) are endowed with regenerative paracrine potential driving pro-survival, anti-fibrotic and proliferative effects. hAFS may also be isolated from III trimester clinical waste samples during scheduled C-sections (perinatal hAFS), thus offering a more easily accessible alternative when compared to fetal hAFS. Nonetheless, little is known about the paracrine profile of perinatal hAFS. Here we provide a detailed characterization of the hAFS total secretome (i.e., the entirety of soluble paracrine factors released by cells in the conditioned medium, hAFS-CM) and the extracellular vesicles (hAFS-EVs) within it, from II trimester fetal- versus III trimester perinatal cells. Fetal- and perinatal hAFS were characterized and subject to hypoxic preconditioning to enhance their paracrine potential. hAFS-CM and hAFS-EV formulations were analyzed for protein and chemokine/cytokine content, and the EV cargo was further investigated by RNA sequencing. The phenotype of fetal- and perinatal hAFS, along with their corresponding secretome formulations, overlapped; yet, fetal hAFS showed immature oxidative phosphorylation activity when compared to perinatal ones. The profiling of their paracrine cargo revealed some differences according to gestational stage and hypoxic preconditioning. Both cell sources provided formulations enriched with neurotrophic, immunomodulatory, anti-fibrotic and endothelial stimulating factors, and the immature fetal hAFS secretome was defined by a more pronounced pro-vasculogenic, regenerative, pro-resolving and anti-aging profile. Small RNA profiling showed microRNA enrichment in both fetal- and perinatal hAFS-EV cargo, with a stably- expressed pro-resolving core as a reference molecular signature. Here we confirm that hAFS represents an appealing source of regenerative paracrine factors; the selection of either fetal or perinatal hAFS secretome formulations for future paracrine therapy should be evaluated considering the specific clinical scenario.

Dissecting the effects of preconditioning with inflammatory cytokines and hypoxia on the angiogenic potential of mesenchymal stromal cell (MSC)-derived soluble proteins and extracellular vesicles (EVs)

Mesenchymal stromal cells (MSCs) are characterized by a regulatory phenotype and respond promptly to the environmental signals modulating their secretory activity. An appropriate preconditioning may induce MSCs to release secretomes with an enhanced regenerative potential. However, it fails to take into account that secretomes are composed by both soluble factors and extracellular vesicles (EVs), whose functions could be altered differently by the preconditioning approach. Here we demonstrate that the MSC secretome is strongly modulated by the simultaneous stimulation with hypoxia and pro-inflammatory cytokines, used to mimic the harsh environment present at the site of injury. We observed that the environmental variations strongly influenced the angiogenic potential of the different secretome fractions. Upon inflammation, the pro-angiogenic capacity of the soluble component of the MSC secretome was strongly inhibited, regardless of the oxygen level, while the EV-encapsulated component was not significantly affected by the inflammatory stimuli. These effects were accompanied by the modulation of the secreted proteins. On one hand, inflammation-activated MSCs release proteins mainly involved in the interaction with innate immune cells and in tissue remodeling/repair; on the other hand, when MSCs are not exposed to an inflamed environment, they respond to the different oxygen levels modulating the expression of proteins involved in the angiogenic process. The cargo content (in terms of miRNAs) of the corresponding EV fractions was less sensitive to the influence of the external stimuli. Our findings suggest that the therapeutic efficacy of MSC-based therapies could be enhanced by selecting the appropriate preconditioning approach and carefully discriminating its effects on the different secretome components.

Young at Heart: Combining Strategies to Rejuvenate Endogenous Mechanisms of Cardiac Repair

True cardiac regeneration of the injured heart has been broadly described in lower vertebrates by active replacement of lost cardiomyocytes to functionally and structurally restore the myocardial tissue. On the contrary, following severe injury (i.e., myocardial infarction) the adult mammalian heart is endowed with an impaired reparative response by means of meager wound healing program and detrimental remodeling, which can lead over time to cardiomyopathy and heart failure. Lately, a growing body of basic, translational and clinical studies have supported the therapeutic use of stem cells to provide myocardial regeneration, with the working hypothesis that stem cells delivered to the cardiac tissue could result into new cardiovascular cells to replenish the lost ones. Nevertheless, multiple independent evidences have demonstrated that injected stem cells are more likely to modulate the cardiac tissue via beneficial paracrine effects, which can enhance cardiac repair and reinstate the embryonic program and cell cycle activity of endogenous cardiac stromal cells and resident cardiomyocytes. Therefore, increasing interest has been addressed to the therapeutic profiling of the stem cell-derived secretome (namely the total of cell-secreted soluble factors), with specific attention to cell-released extracellular vesicles, including exosomes, carrying cardioprotective and regenerative RNA molecules. In addition, the use of cardiac decellularized extracellular matrix has been recently suggested as promising biomaterial to develop novel therapeutic strategies for myocardial repair, as either source of molecular cues for regeneration, biological scaffold for cardiac tissue engineering or biomaterial platform for the functional release of factors. In this review, we will specifically address the translational relevance of these two approaches with ad hoc interest in their feasibility to rejuvenate endogenous mechanisms of cardiac repair up to functional regeneration.

Extracellular Vesicles as Natural, Safe and Efficient Drug Delivery Systems

Extracellular vesicles (EVs) are particles naturally released from cells, delimited by a lipid bilayer, carrying functionally active biological molecules. In addition to their physiological role in cellular communication, the interest of the scientific community has recently turned to the use of EVs as vehicles for delivering therapeutic molecules. Several attempts are being made to ameliorate drug encapsulation and targeting, but these efforts are thwarted if the starting material does not meet stringent quality criteria. Here, we take a step back to the sources and isolation procedures that could guarantee significant improvements in the purification of EVs to be used as drug carriers, highlighting the advantages and shortcomings of each approach.

Isolation and Flow Cytometry Characterization of Extracellular-Vesicle Subpopulations Derived from Human Mesenchymal Stromal Cells

This unit describes protocols for isolating subpopulations of extracellular vesicles (EVs) purified from human adipose tissue-derived mesenchymal stromal cells by density gradient centrifugation and for characterizing them by flow cytometry (FCM). Determining the optimal strategy for isolating EVs is a critical step toward retrieving the maximal amount while ensuring the recovery of different vesicular subtypes. The first protocol details density gradient centrifugation to isolate both exosomes and microvesicles. In the second protocol, characterization of EV subpopulations by FCM is depicted, taking advantage of non-conventional modalities, in accordance with the latest technical indications. The procedures described here can be easily reproduced and can be employed regardless of the cell type used to obtain EVs. © 2019 by John Wiley & Sons, Inc.

Topographical Features of Graphene-Oxide-Functionalized Substrates Modulate Cancer and Healthy Cell Adhesion Based on the Cell Tissue of Origin

Graphene-derived materials, such as graphene oxide (GO), have been widely explored for biomedical and biological applications, including cancer research. Despite some recent works proving that GO inhibits the migration and invasion of different cancer cells, so far most of these in vitro studies have been conducted using GO sheets dispersed in solution or as a planar film. On the contrary, little is known about cellular activities, such as cell viability, adhesion, and spreading, when cancer cells interface with GO functionalized hydrogel-based surfaces, biomechanically and structurally more similar to the tumor environment. Here, we evaluate the interactions of human breast cancer cells (MDA-MB-231) with alginate (Alg)/GO hydrogel-based substrates, and compare them with a cancer cell line from human osteosarcoma (HOS) and healthy murine fibroblasts (3T3). We observed that GO addition selectively inhibits malignant breast cancer cell adhesion efficiency and spreading area, while promotes HOS and 3T3 adhesive processes. Furthermore, we did not observe the same results over Alg substrates with GO nanosheets dispersed in the medium, without embedment into the Alg. This suggests that cancer (MDA-MB-231 and HOS) and healthy (3T3) cell adhesion efficacy does not depend on the cellular tumoral nature and it is driven by the topographical cues provided by the GO-based substrates, whose physical-mechanical characteristics better mimic those of the cell native tissue. We envision that this study can provide a rational for future design and use of graphene-based nanomaterials for cancer research by deepening the knowledge of graphene-cancer cell specific interactions.

Circulating healing (CH) cells expressing BST2 are functionally activated by the injury-regulated systemic factor HGFA

Background

Restoration of damaged tissues through the activation of endogenous progenitors is an attractive therapeutic option. A deep evaluation of the intrinsic stem/progenitor cell properties as well as the reciprocal interactions with injured environments is of critical importance.

Methods

Here, we show that bone marrow stromal cell antigen 2 (BST2) allows the isolation of a population of circulating progenitors, the circulating healing (CH) cells, characterized by a distinctive core signature. The bone marrow (BM) origin of BST2^pos CH cells has been strengthened by the co-expression of leptin receptor, the hallmark of a subpopulation of BM-skeletal stem cells.

Results

BST2^pos CH cells retained the capacity to (i) respond to injury signals generated by a bone fracture, (ii) modify the expression of cell motility genes following damage, and (iii) react to hepatocyte growth factor-activator (HGFA), an injury-related stimulus sufficient to induce their transition into G_ALERT, a state in which cells are functionally activated and participate in tissue repair.

Conclusions

Taken together, these results could pave the way for the identification of new strategies to enhance and potentiate endogenous regenerative mechanisms for future therapies.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1056-1) contains supplementary material, which is available to authorized users.

"Green-reduced" graphene oxide induces in vitro an enhanced biomimetic mineralization of polycaprolactone electrospun meshes

A novel green method for graphene oxide (GO) reduction via ascorbic acid has been adopted to realize bio-friendly reduced graphene oxide (RGO)/polycaprolactone (PCL) nanofibrous meshes, as substrates for bone tissue engineering applications. PCL fibrous mats enriched with either RGO or GO (0.25 wt%) were fabricated to recapitulate the fibrillar structure of the bone extracellular matrix (ECM) and the effects of RGO incorporation on the structural proprieties, biomechanics and bioactivity of the nano-composites meshes were evaluated. RGO/PCL fibrous meshes displayed superior mechanical properties (i.e. Young's Modulus and ultimate tensile strength) besides supporting noticeably improved cell adhesion, spreading and proliferation of fibroblasts and osteoblast-like cell lines. Furthermore, RGO-based electrospun substrates enhanced in vitro calcium deposition in the ECM produced by osteoblast-like cells, which was paralleled, in human mesenchymal stem cells grown onto the same substrates, by an increased expression of the osteogenic markers mandatory for mineralization. In this respect, the capability of graphene-based materials to adsorb osteogenic factors cooperates synergically with the rougher surface of RGO/PCL-based materials, evidenced by AFM analysis, to ignite mineralization of the neodeposited matrix and to promote the osteogenic commitment of the cultured cell in the surrounding microenvironment.

A Three-Dimensional Traction/Torsion Bioreactor System for Tissue Engineering

Purpose

The aim of this study was to design, develop and validate a simple, compact bioreactor system for tissue engineering. The resulting bioreactor was designed to achieve ease-of-use and low costs for automated cell-culturing procedures onto three-dimensional scaffolds under controlled torsion/traction regimes.

Methods

Highly porous poly-caprolactone-based scaffolds were used as substrates colonized by fibroblast cells (3T3 cell line). Constructs were placed within the cylindrical culture chamber, clumped at the ends and exposed to controlled sequences of torsional stimuli (forward/back-forward sequential cycles of 100° from neutral position at a rate of 600°/min) through a stepper-motor; working settings were defined via PC by an easy user-interface. Cell adhesion, morphology, cytoskeletal fiber orientation and gene expression of extracellular matrix proteins (collagen type I, tenascin C, collagen type III) were evaluated after three days of torsional stimulation in the bioreactor system.

Results and Conclusions

The 3D bioreactor system was validated in terms of sterility, experimental reproducibility and flexibility. Cells adhered well onto the polymeric scaffolds. Collagen type I, tenascin C and collagen type III gene expression were significantly up-regulated when cells were cultured under torsion in the bioreactor for three days. In conclusion, we have developed a simple, efficient and versatile 3D cell-culture system to engineer ligament grafts. This system can be used either as a model to investigate mechanisms of tissue development or as a graft manufacturing system for possible clinical use in the field of regenerative medicine.

Osteogenic Differentiation of Human Mesenchymal Stromal Cells on Surface-Modified Titanium Alloys for Orthopedic and Dental Implants

Purpose

Surface properties of titanium alloys, used for orthopedic and dental applications, are known to affect implant interactions with host tissues. Osteointegration, bone growth and remodeling in the area surrounding the implants can be implemented by specific biomimetic treatments; these allow the preparation of micro/nanostructured titanium surfaces with a thickened oxide layer, doped with calcium and phosphorus ions. We have challenged these experimental titanium alloys with primary human bone marrow stromal cells to compare the osteogenic differentiation outcomes of the cells once they are seeded onto the modified surfaces, thus simulating a prosthetic device-biological interface of clinical relevance.

Methods

A specific anodic spark discharge was the biomimetic treatment of choice, providing experimental titanium disks treated with different alkali etching approaches. The disks, checked by electron microscopy and spectroscopy, were subsequently used as substrates for the proliferation and osteogenic differentiation of human cells. Expression of markers of the osteogenic lineage was assessed by means of qualitative and quantitative PCR, by cytochemistry, immunohistochemistry Western blot and matrix metalloprotease activity analyses.

Results

Metal surfaces were initially less permissive for cell growth. Untreated control substrates were less efficient in sustaining mineralized matrix deposition upon osteogenic induction of the cells. Interestingly, bone sialo protein and matrix metalloprotease 2 levels were enhanced on experimental metals compared to control surfaces, particularly for titanium oxide coatings etched with KOH.

Discussion

As a whole, the KOH-modification of titanium surfaces seems to allow the best osteogenic differentiation of human mesenchymal stromal cells, representing a possible plus for future clinical prosthetic applications.

Exposure to reversine affects the chondrocyte morphology and phenotype in vitro

Articular chondrocytes derived from osteoarthritic tissues (OA HAC) show a severely reduced chondrogenic commitment. This impairment undermines their use for tissue-engineered cartilage repair, which relies on cell proliferation and growth to meet therapeutic needs, but also on efficient cell plasticity to recover the chondrogenic phenotype. Reversine (Rev), a 2,6-disubstituted purine inhibitor of spindle-assembly checkpoints, was described to convert differentiated mesenchymal cells to their undifferentiated precursors. We hypothesized that Rev exposure could divert OA HAC to more plastic cells, re-boosting their subsequent commitment. HAC were enzymatically released from OA cartilage specimens, expanded for 2 weeks and treated with 5 μm Rev in dimethylsulphoxide (DMSO) or with DMSO alone for 6 days. Cell growth was assessed using the AlamarBlue^TM assay. Cytoskeletal structure, endoproliferation and caspase-3-immunopositivity were assayed by epifluorescence microscopy. The OA HAC chondrogenic performance was evaluated by quantitative reverse transcription-polymerase chain reaction (RT-PCR) for glyceraldehyde-3-phosphate dehydrogenase, Sox9, Aggrecan (Agg), type II collagen (Col2), Ki67, cyclinD1, transforming growth factor-β1 (TGF-β1), -2 and -3, interleukin-1β (IL-1β) and -6 , SMAD3 and -7, and vascular endothelial growth factor. Rev-treated OA HAC recovered polygonal morphology and reduced Ki67 expression and proliferation. Cell-cycle impairment accounted for altered cytoskeletal organization, endoproliferation and apoptosis, whereas a compensatory mechanism sustained the increased cyclinD1 transcript levels. Sox9, Agg and TGFs were overexpressed, but not Col2. IL transcripts were massively downregulated. These events were dose-related and transient. Overall, in spite of a higher Rev-induced transcriptional activity for extracellular matrix components and in spite of a Rev-treated cell phenotype closer to that of the three-dimensional native articular chondrocyte, Rev effects seem unleashed from a full regained chondrogenic potential.

Skin Rejuvenation and Volume Enhancement with the Micro Superficial Enhanced Fluid Fat Injection (M-SEFFI) for Skin Aging of the Periocular and Perioral Regions

BACKGROUND

Adipose-derived stromal and stem cells (ADSC) in autologous fat promises regenerative advantages, and injected into the dermal and subdermal layers, enhances rejuvenation and volume. However, extremely superficial fat injection with current techniques is limited.

OBJECTIVES

Efficacy and viability evaluation of fat harvested with extremely small side port (0.3 mm) cannulae without further tissue manipulation for the correction of aging/thin skin in the periocular and perioral regions.

METHODS

Micro-superficial enhanced fluid fat injection (M-SEFFI) harvests adipose tissue with a multi-perforated cannula (0.3 mm), and autologous platelet rich plasma (PRP) is added. The tissue is injected into the dermal region of the periocular and perioral zones. Efficacy and viability were evaluated by histological and cell culture analysis. Clinical assessment included retrospective evaluation according to 1 = no effect, 2 = fair effect, 3 = good effect, 4 = excellent effect.

RESULTS

Between June 2014 and July 2015, 65 patients (7 men; mean age 49.7 years) were treated with M-SEFFI. No intraoperative complications or visible lumpiness were recorded. Analysis demonstrated mature, viable adipocytes with a strong stromal component. Following PRP addition, there was a greater proliferation noted in the M-SEFFI compared to the SEFFI (0.5 mm). Mean follow-up was 4.1 months. Clinical assessment by surgeons and patients at 1 month was 3.52 and 3.74, and 6 months 3.06 and 2.6 respectively.

CONCLUSIONS

M-SEFFI is effective and viable for lump free skin rejuvenation and volume enhancement, through the extraction of smoother ADSC rich, autologous fat tissue that does not require further tissue manipulation, to correct skin aging.

LEVEL OF EVIDENCE

4 Therapeutic.

Generation of a Functional Human Neural Network by NDM29 Overexpression in Neuroblastoma Cancer Cells

Recent advances in life sciences suggest that human and rodent cell responses to stimuli might differ significantly. In this context, the results achieved in neurotoxicology and biomedical research practices using neural networks obtained from mouse or rat primary culture of neurons would benefit of the parallel evaluation of the same parameters using fully differentiated neurons with a human genetic background, thus emphasizing the current need of neuronal cells with human origin. In this work, we developed a human functionally active neural network derived by human neuroblastoma cancer cells genetically engineered to overexpress NDM29, a non-coding RNA whose increased synthesis causes the differentiation toward a neuronal phenotype. These cells are here analyzed accurately showing functional and morphological traits of neurons such as the expression of neuron-specific proteins and the possibility to generate the expected neuronal current traces and action potentials. Their morphometrical analysis is carried out by quantitative phase microscopy showing soma and axon sizes compatible with those of functional neurons. The ability of these cells to connect autonomously forming physical junctions recapitulates that of hippocampal neurons, as resulting by connect-ability test. Lastly, these cells self-organize in neural networks able to produce spontaneous firing, in which spikes can be clustered in bursts. Altogether, these results show that the neural network obtained by NDM29-dependent differentiation of neuroblastoma cells is a suitable tool for biomedical research practices.

Chemical and morphological gradient scaffolds to mimic hierarchically complex tissues: From theoretical modeling to their fabrication

Porous multiphase scaffolds have been proposed in different tissue engineering applications because of their potential to artificially recreate the heterogeneous structure of hierarchically complex tissues. Recently, graded scaffolds have been also realized, offering a continuum at the interface among different phases for an enhanced structural stability of the scaffold. However, their internal architecture is often obtained empirically and the architectural parameters rarely predetermined. The aim of this work is to offer a theoretical model as tool for the design and fabrication of functional and structural complex graded scaffolds with predicted morphological and chemical features, to overcome the time-consuming trial and error experimental method. This developed mathematical model uses laws of motions, Stokes equations, and viscosity laws to describe the dependence between centrifugation speed and fiber/particles sedimentation velocity over time, which finally affects the fiber packing, and thus the total porosity of the 3D scaffolds. The efficacy of the theoretical model was tested by realizing engineered graded grafts for osteochondral tissue engineering applications. The procedure, based on combined centrifugation and freeze-drying technique, was applied on both polycaprolactone (PCL) and collagen-type-I (COL) to test the versatility of the entire process. A functional gradient was combined to the morphological one by adding hydroxyapatite (HA) powders, to mimic the bone mineral phase. Results show that 3D bioactive morphologically and chemically graded grafts can be properly designed and realized in agreement with the theoretical model. Biotechnol. Bioeng. 2016;113: 2286-2297. © 2016 Wiley Periodicals, Inc.

Interaction Between Breast Cancer Cells and Adipose Tissue Cells Derived from Fat Grafting

BACKGROUND

Adipose tissue transplantation has the benefit of providing both regenerative and aesthetic outcomes in breast cancer treatment. However, the transplanted tissue can stimulate the growth of residual cancer cells.

OBJECTIVES

The aim of this study is to identify the interactions between adipose tissue cell subpopulations and human cancer cell lines.

METHODS

Intact adipose tissue from lipofilling procedures as well as fibroblasts derived from adipose tissue, were cocultured in the presence of MDA-MB-231, MCF-7 e ZR-75-1 breast cancer cell lines. The influence on cancer cell lines of fibroblasts, induced to differentiate into specific adipocytes, was also assayed.

RESULTS

All cancer cell lines displayed a significant increase in proliferation rate when cocultured in the presence of either intact adipose tissue or induced adipocytes. To a lesser extent, uninduced fibroblasts stimulate breast cancer cell proliferation.

CONCLUSIONS

Recent studies have shown that the microenvironment surrounding breast cancer cells may stimulate growth and promote progression of residual cancer cells when surgery is performed on the main tumor mass. Accordingly, the graft of adipose tissue could potentially promote or accelerate the development of a subclinical tumor or support its locoregional recurrence. Our data suggest that adipocytes have a remarkable influence on the proliferation of cancer cell lines. The oncological safety of the lipofilling procedure outcome is still debated; thus, further studies and consistent follow-up examination are needed.

C6: A Monoclonal Antibody Specific for a Fibronectin Epitope Situated at the Interface between the Oncofoetal Extra-Domain B and the Repeat III8

Background

Fibronectin (FN) is a large multidomain molecule that is involved in many cellular processes. Different FN isoforms arise from alternative splicing of the pre-mRNA including, most notably, the FN isoform that contains the “extra-domain-B” (ED-B). The FN isoform containing ED-B (known as B-FN) is undetectable in healthy adult tissues but is present in large amounts in neoplastic and foetal tissues as well as on the blood vessels during angiogenesis. Thus, antibodies specific for B-FN can be useful for detecting and targeting neoplastic tissues in vivo. We previously characterised C6, a new monoclonal antibody specific for human B-FN and we suggested that it reacts with the B-C loop of the type III repeat 8 which is masked in FN isoforms lacking ED-B and that the insertion of ED-B in FN molecules unmasked it. Here we have now consolidated and refined the characterization of this B-FN specific antibody demonstrating that the epitope recognized by C6 also includes loop E-F of ED-B.

Methodology

We built the three dimensional model of the variable regions of the mAb C6 and of the FN fragment EDB-III8 and performed protein:protein docking simulation using the web server ClusPro2.0. To confirm the data obtained by protein:protein docking we generated mutant fragments of the recombinant FN fragment EDB-III8 and tested their reactivity with C6.

Conclusion

The monoclonal antibody C6 reacts with an epitope formed by the B-C loop of domain III8 and the E-F loop of ED-B. Both loops are required for an immunological reaction, thus this monoclonal is strictly specific for B-FN but the part of the epitope on III8 confers the human specificity.

Bone Tissue Engineering: Past-Present-Future

Bone is one of the few tissues to display a true potential for regeneration. Fracture healing is an obvious example where regeneration occurs through tightly regulated sequences of molecular and cellular events which recapitulate tissue formation seen during embryogenesis. Still in some instances, bone regeneration does not occur properly (i.e. critical size lesions) and an appropriate therapeutic intervention is necessary. Successful replacement of bone by tissue engineering will likely depend on the recapitulation of this flow of events. In fact, bone regeneration requires cross-talk between microenvironmental factors and cells; for example, resident mesenchymal progenitors are recruited and properly guided by soluble and insoluble signaling molecules. Tissue engineering attempts to reproduce and to mimic this natural milieu by delivering cells capable of differentiating into osteoblasts, inducing growth factors and biomaterials to support cellular attachment, proliferation, migration, and matrix deposition. In the last two decades, a significant effort has been made by the scientific community in the development of methods and protocols to repair and regenerate tissues such as bone, cartilage, tendons, and ligaments. In this same period, great advancements have been achieved in the biology of stem cells and on the mechanisms governing "stemness". Unfortunately, after two decades, effective clinical translation does not exist, besides a few limited examples. Many years have passed since cell-based regenerative therapies were first described as "promising approaches", but this definition still engulfs the present literature. Failure to envisage translational cell therapy applications in routine medical practice evidences the existence of unresolved scientific and technical struggles, some of which still puzzle researchers in the field and are presented in this chapter.

Rheological properties, biocompatibility and in vivo performance of new hydrogel-based bone fillers

Three different heterologous substitutes for bone regeneration, manufactured with equine-derived cortical powder, cancellous chips and demineralized bone matrix granules, were compared in vitro and in vivo.

Superficial Enhanced Fluid Fat Injection (SEFFI) to Correct Volume Defects and Skin Aging of the Face and Periocular Region

BACKGROUND

Although recent research on micro fat has shown the potential advantages of superficial implantation and high stem cell content, clinical applications thus far have been limited.

OBJECTIVES

The authors report their experience with superficial enhanced fluid fat injection (SEFFI) for the correction of volume loss and skin aging of the face in general and in the periocular region.

METHODS

The finer SEFFI preparation (0.5 mL) was injected into the orbicularis in the periorbital and perioral areas, and the 0.8-mL preparation was injected subdermally elsewhere in the face.

RESULTS

The records of 98 consecutive patients were reviewed. Average follow-up time was 6 months, and average volume of implanted fat was 20 mL and 51.4 mL for the 0.5-mL and 0.8-mL preparations, respectively. Good or excellent results were achieved for volume restoration and skin improvement in all patients. Complications were minor and included an oil cyst in 3 patients. The smaller SEFFI quantity (0.5 mL) was well suited to correct volume loss in the eyelids, especially the deep upper sulcus and tear trough, whereas the larger SEFFI content was effective for larger volume deficits in other areas of the face, including the brow, temporal fossa, zygomatic-malar region, nasolabial folds, marionette lines, chin, and lips.

CONCLUSIONS

The fat administered by SEFFI is easily harvested via small side-port cannulae, yielding micro fat that is rich in viable adipocytes and stem cells. Both volumes of fat (0.5 mL and 0.8 mL) were effective for treating age-related lipoatrophy, reducing facial rhytids, and improving skin quality.

LEVEL OF EVIDENCE

4 Therapeutic.

A novel scaffold geometry for chondral applications: theoretical model and in vivo validation

A theoretical model of the 3D scaffold internal architecture has been implemented with the aim to predict the effects of some geometrical parameters on total porosity, Young modulus, buckling resistance and permeability of the graft. This model has been adopted to produce porous poly-caprolacton based grafts for chondral tissue engineering applications, best tuning mechanical and functional features of the scaffolds. Material prototypes were produced with an internal geometry with parallel oriented cylindrical pores of 200 μm of radius (r) and an interpore distance/pores radius (d/r) ratio of 1. The scaffolds have been then extensively characterized; progenitor cells were then used to test their capability to support cartilaginous matrix deposition in an ectopic model. Scaffold prototypes fulfill both the chemical-physical requirements, in terms of Young's modulus and permeability, and the functional needs, such as surface area per volume and total porosity, for an enhanced cellular colonization and matrix deposition. Moreover, the grafts showed interesting chondrogenic potential in vivo, besides offering adequate mechanical performances in vitro, thus becoming a promising candidate for chondral tissues repair. Finally, a very good agreement was found between the prediction of the theoretical model and the experimental data. Many assumption of this theoretical model, hereby applied to cartilage, may be transposed to other tissue engineering applications, such as bone substitutes.

Defining an optimal stromal derived factor-1 presentation for effective recruitment of mesenchymal stem cells in 3D

In "situ" tissue engineering is a promising approach in regenerative medicine, envisaging to potentiate the physiological tissue repair processes by recruiting the host's own cellular progenitors at the lesion site by means of bioactive materials. Despite numerous works focused the attention in characterizing novel chemoattractant molecules, only few studied the optimal way to present signal in the microenvironment, in order to recruit cells more effectively. In this work, we have analyzed the effects of gradients of stromal derived factor-1 (SDF-1) on the migratory behavior of human mesenchymal stem cells (MSCs). We have characterized the expression of the chemokine-associated receptor, CXCR4, using cytofluorimetric and real-time PCR analyses. Gradients of SDF-1 were created in 3D collagen gels in a chemotaxis chamber. Migration parameters were evaluated using different chemoattractant concentrations. Our results show that cell motion is strongly affected by the spatio-temporal features of SDF-1 gradients. In particular, we demonstrated that the presence of SDF-1 not only influences cell motility but alters the cell state in terms of SDF-1 receptor expression and productions, thus modifying the way cells perceive the signal itself. Our observations highlight the importance of a correct stimulation of MSCs by means of SDF-1 in order to implement on effective cell recruitment. Our results could be useful for the creation of a "cell instructive material" that is capable to communicate with the cells and control and direct tissue regeneration. Biotechnol. Bioeng. 2014;111: 2303-2316. © 2014 Wiley Periodicals, Inc.

Chronic lymphocytic leukemia nurse-like cells express hepatocyte growth factor receptor (c-MET) and indoleamine 2,3-dioxygenase and display features of immunosuppressive type 2 skewed macrophages

Hepatocyte growth factor, produced by stromal and follicular dendritic cells, and present at high concentrations in the sera of patients with chronic lymphocytic leukemia, prolongs the survival of leukemic B cells by interacting with their receptor, c-MET. It is, however, unknown whether hepatocyte growth factor influences microenvironmental cells, such as nurse-like cells, which deliver survival signals to the leukemic clone. We evaluated the expression of c-MET on nurse-like cells and monocytes from patients with chronic lymphocytic leukemia and searched for phenotypic/functional features supposed to be influenced by the hepatocyte growth factor/c-MET interaction. c-MET is expressed at high levels on nurse-like cells and at significantly higher levels than normal on monocytes from patients. Moreover, the hepatocyte growth factor/c-MET interaction activates STAT3(TYR705) phosphorylation in nurse-like cells. Indoleamine 2,3-dioxygenase, an enzyme modulating T-cell proliferation and induced on normal monocytes after hepatocyte growth factor treatment, was detected together with interleukin-10 on nurse-like cells, and on freshly-prepared patients' monocytes. Immunohistochemical/immunostaining analyses demonstrated the presence of c-MET(+) and indoleamine 2,3-dioxygenase(+) cells in lymph node biopsies, co-expressed with CD68 and vimentin. Furthermore nurse-like cells and chronic lymphocytic monocytes significantly inhibited T-cell proliferation, prevented by anti-transforming growth factor beta and interleukin-10 antibodies and indoleamine 2,3-dioxygenase inhibitors, and supported CD4(+)CD25(high+)/FOXP3(+) T regulatory cell expansion. We suggest that nurse-like cells display features of immunosuppressive type 2 macrophages: higher hepatocyte growth factor levels, produced by leukemic or other microenvironmental surrounding cells, may cooperate to induce M2 polarization. Hepatocyte growth factor may thus have a dual pathophysiological role: directly through enhancement of survival of the leukemic clone and indirectly by favoring T-cell immunosuppression.

Response of osteoblast-like MG63 on neoglycosylated collagen matrices

Collagen matrices modified in order to expose galactose residues to cells were studied for their interaction with osteosarcoma-derived cell line MG63.

Composite electrospun nanofibers for influencing stem cell fate

The design of new bioactive materials, provided with "instructive properties" and able to regulate stem cell behavior, is the goal for several research groups involved in tissue engineering. This new function, commonly reserved for growth factors, can lead to the development of a new class of implantable scaffolds, useful for accelerating tissue regeneration in a controlled manner. In this scenario, the likely most versatile and effective tools for the realization of such scaffolds are based on nano- and microtechnology. Here, we show how exploiting the electrostatic spinning (ES) technique for producing a nanofibrillar composite structure, by mimicking topographically the extracellular matrix environment, can influence the fate of human bone marrow mesenchymal stem cells, inducing osteogenic differentiation in the absence of chemical treatments or cellular reprogramming. Basic cues on the choice of the materials and useful experimental instructions for realizing composite nanofibrous scaffolds will be given as well as fundamental tips.

Design and characterization of a tissue-engineered bilayer scaffold for osteochondral tissue repair

Treatment of full-thickness cartilage defects relies on osteochondral bilayer grafts, which mimic the microenvironment and structure of the two affected tissues: articular cartilage and subchondral bone. However, the integrity and stability of the grafts are hampered by the presence of a weak interphase, generated by the layering processes of scaffold manufacturing. We describe here the design and development of a bilayer monolithic osteochondral graft, avoiding delamination of the two distinct layers but preserving the cues for selective generation of cartilage and bone. A highly porous polycaprolactone-based graft was obtained by combining solvent casting/particulate leaching techniques. Pore structure and interconnections were designed to favour in vivo vascularization only at the bony layer. Hydroxyapatite granules were added as bioactive signals at the site of bone regeneration. Unconfined compressive tests displayed optimal elastic properties and low residual deformation of the graft after unloading (< 3%). The structural integrity of the graft was successfully validated by tension fracture tests, revealing high resistance to delamination, since fractures were never displayed at the interface of the layers (n = 8). Ectopic implantation of grafts in nude mice, after seeding with bovine trabecular bone-derived mesenchymal stem cells and bovine articular chondrocytes, resulted in thick areas of mature bone surrounding ceramic granules within the bony layer, and a cartilaginous alcianophilic matrix in the chondral layer. Vascularization was mostly observed in the bony layer, with a statistically significant higher blood vessel density and mean area. Thus, the easily generated osteochondral scaffolds, since they are mechanically and biologically functional, are suitable for tissue-engineering applications for cartilage repair.

The influence of plasma technology coupled to chemical grafting on the cell growth compliance of 3D hydroxyapatite scaffolds

The development of advanced materials with biomimetic features in order to elicit desired biological responses and to guarantee tissue biocompatibility is recently gaining attention for tissue engineering applications. Bioceramics, such as hydroxyapatite-based biomaterials are now used in a number of different applications throughout the body, covering all areas of the skeleton, due to their biological and chemical similarity to the inorganic phases of bones. When bioactive sintered hydroxyapatite (HA) is desired, biomolecular modification of these materials is needed. In the present work, we investigated the influence of plasma surface modification coupled to chemical grafting on the cell growth compliance of HA 3D scaffolds.

TGF β-1 administration during ex vivo expansion of human articular chondrocytes in a serum-free medium redirects the cell phenotype toward hypertrophy

Cell-based cartilage resurfacing requires ex vivo expansion of autologous articular chondrocytes. Defined culture conditions minimize expansion-dependent phenotypic alterations but maintenance of the cells' differentiation potential must be carefully assessed. Transforming growth factor β-1 (TGF β-1) positively regulates the expression of several cartilage proteins, but its therapeutic application in damaged cartilage is controversial. Thus we evaluated the phenotypic outcomes of cultured human articular chondrocytes exposed to TGF β-1 during monolayer expansion in a serum-free medium. After five doublings cells were transferred to micromass cultures to assess their chondrogenic differentiation, or replated in osteogenic medium. Immunocytostainings of micromasses of TGF-expanded cells showed loss of aggrecan and type II collagen. Positivity was evidenced for RAGE, IHH, type X collagen and for apoptotic cells, paralleling a reduction of BCL-2 levels, suggesting hypertrophic differentiation. TGF β-1-exposed cells also evidenced increased mRNA levels for bone sialoprotein, osteopontin, matrix metalloproteinase-13, TIMP-3, VEGF and SMAD7, enhanced alkaline phosphatase activity and pyrophosphate availability. Conversely, SMAD3 mRNA and protein contents were reduced. After osteogenic induction, only TGF-expanded cells strongly mineralized and impaired p38 kinase activity, a contributor of chondrocytes' differentiation. To evaluate possible endochondral ossification progression, we seeded the chondrocytes on hydroxyapatite scaffolds, subsequently implanted in an in vivo ectopic setting, but cells failed to reach overt ossification; nonetheless, constructs seeded with TGF-exposed cells displayed blood vessels of the host vascular supply with enlarged diameters, suggestive of vascular remodeling, as in bone growth. Thus TGF-exposure during articular chondrocytes expansion induces a phenotype switch to hypertrophy, an undesirable effect for cells possibly intended for tissue-engineered cartilage repair.

MgCHA particles dispersion in porous PCL scaffolds: in vitro mineralization and in vivo bone formation

In this work, we focus on the in vitro and in vivo response of composite scaffolds obtained by incorporating Mg,CO3 -doped hydroxyapatite (HA) particles in poly(ε-caprolactone) (PCL) porous matrices. After a complete analysis of chemical and physical properties of synthesized particles (i.e. SEM/EDS, DSC, XRD and FTIR), we demonstrate that the Mg,CO3 doping influences the surface wettability with implications upon cell-material interaction and new bone formation mechanisms. In particular, ion substitution in apatite crystals positively influences the early in vitro cellular response of human mesenchymal stem cells (hMSCs), i.e. adhesion and proliferation, and promotes an extensive mineralization of the scaffold in osteogenic medium, thus conforming to a more faithful reproduction of the native bone environment than undoped HA particles, used as control in PCL matrices. Furthermore, we demonstrate that Mg,CO3 -doped HA in PCL scaffolds support the in vivo cellular response by inducing neo-bone formation as early as 2 months post-implantation, and abundant mature bone tissue at the sixth month, with a lamellar structure and completely formed bone marrow. Together, these results indicate that Mg(2+) and CO3 (2-) ion substitution in HA particles enhances the scaffold properties, providing the right chemical signals to combine with morphological requirements (i.e. pore size, shape and interconnectivity) to drive osteogenic response in scaffold-aided bone regeneration.

Order versus Disorder: in vivo bone formation within osteoconductive scaffolds

In modern biomaterial design the generation of an environment mimicking some of the extracellular matrix features is envisaged to support molecular cross-talk between cells and scaffolds during tissue formation/remodeling. In bone substitutes chemical biomimesis has been particularly exploited; conversely, the relevance of pre-determined scaffold architecture for regenerated bone outputs is still unclear. Thus we aimed to demonstrate that a different organization of collagen fibers within newly formed bone under unloading conditions can be generated by differently architectured scaffolds. An ordered and confined geometry of hydroxyapatite foams concentrated collagen fibers within the pores, and triggered their self-assembly in a cholesteric-banded pattern, resulting in compact lamellar bone. Conversely, when progenitor cells were loaded onto nanofibrous collagen-based sponges, new collagen fibers were distributed in a nematic phase, resulting mostly in woven isotropic bone. Thus specific biomaterial design relevantly contributes to properly drive collagen fibers assembly to target bone regeneration.

Mesenchymal stem cells induce functionally active T-regulatory lymphocytes in a paracrine fashion and ameliorate experimental autoimmune uveitis

PURPOSE

Mesenchymal stem/progenitor cells (MSCs) have regenerative and immunomodulatory properties, exerted by cell-cell contact and in a paracrine fashion. Part of their immunosuppressive activity has been ascribed to their ability to promote the induction of CD4+CD25+FoxP3+ T lymphocytes with regulatory functions (Treg). Here the authors studied the effect of MSCs on the induction of Treg and on the development of autoimmunity, and they examined the possibility that MSC-mediated Treg induction could be attributed to the secretion of soluble factors.

METHODS

The authors induced experimental autoimmune uveitis (EAU) in mice by immunization with the 1-20 peptide of the intraphotoreceptor binding protein. At the same time, some of the animals were treated intraperitoneally with syngeneic MSCs. The authors checked T-cell responses and in vitro Treg conversion by cell proliferation and blocking assays, in cell-cell contact and transwell settings. TGFβ and TGFβ receptor gene expression analyses were performed by real-time PCR.

RESULTS

The authors found that a single intraperitoneal injection of MSCs was able to significantly attenuate EAU and that a significantly higher percentage of adaptive Treg was present in MSC-treated mice than in MSC-untreated animals. In vitro blocking of antigen presentation by major histocompatibility complex class II precluded priming and clonal expansion of antigen-specific Treg, whereas blockade of TGFβ impaired the expression of FoxP3, preventing the conversion of CD4+ T cells into functionally active Treg.

CONCLUSIONS

The authors demonstrated that MSCs can inhibit EAU and that their immunomodulatory function is due at least in part to the induction of antigen-specific Treg in a paracrine fashion by secreting TGFβ.

In vivo lamellar bone formation in fibre coated MgCHA-PCL-composite scaffolds

Bio-inspired materials with controlled topography have gained increasing interest in regenerative medicine, because of their ability to reproduce the physical features of natural extracellular matrix, thus amplifying certain biological responses both in vitro and in vivo, such as contact guidance and differentiation. However, information on the ability to adapt this high cell potential to 3D scaffolds, effective to be implanted in clinical bone defect, is still missing. Here, we examine the pattern of bone tissue generated within the implant in an ectopic model, seeding bone marrow progenitor cells onto PCL-MgCHA scaffolds. This composite material presented a porous structure with micro/nanostructured surfaces obtained by combining phase inversion/salt leaching and electrospinning techniques. Histological analysis of grafts harvested after 1-2-6 months from implantation highlights an extent of lamellar bone tissue within interconnected pores of fibre coated PCL-MgCHA composites, whereas uncoated scaffolds displayed sparse deposition of bone. Pure PCL scaffolds did not reveal any trace of bone for the overall 6 months of observation. In conclusion, we show that a structural modification in scaffold design is able to enhance bone regeneration possibly mimicking some physiological cues of the natural tissue.

Osteoinduction of human mesenchymal stem cells by bioactive composite scaffolds without supplemental osteogenic growth factors

The development of a new family of implantable bioinspired materials is a focal point of bone tissue engineering. Implant surfaces that better mimic the natural bone extracellular matrix, a naturally nano-composite tissue, can stimulate stem cell differentiation towards osteogenic lineages in the absence of specific chemical treatments. Herein we describe a bioactive composite nanofibrous scaffold, composed of poly-caprolactone (PCL) and nano-sized hydroxyapatite (HA) or beta-tricalcium phosphate (TCP), which was able to support the growth of human bone marrow mesenchymal stem cells (hMSCs) and guide their osteogenic differentiation at the same time. Morphological and physical/chemical investigations were carried out by scanning, transmission electron microscopy, Fourier-transform infrared (FTIR) spectroscopy, mechanical and wettability analysis. Upon culturing hMSCs on composite nanofibers, we found that the incorporation of either HA or TCP into the PCL nanofibers did not affect cell viability, meanwhile the presence of the mineral phase increases the activity of alkaline phosphatase (ALP), an early marker of bone formation, and mRNA expression levels of osteoblast-related genes, such as the Runt-related transcription factor 2 (Runx-2) and bone sialoprotein (BSP), in total absence of osteogenic supplements. These results suggest that both the nanofibrous structure and the chemical composition of the scaffolds play a role in regulating the osteogenic differentiation of hMSCs.

Regulatory influence of scaffolds on cell behavior: how cells decode biomaterials

A stem cell is defined as a cell able to self-renew and at the same time to generate one or more specialized progenies. In the adult organism, stem cells need a specific microenvironment where to reside. This tissue-specific instructive microenvironment, hosting stem cells and governing their fate, is composed of extracellular matrix and soluble molecules. Cell-matrix and cell-cell interactions also contribute to the specifications of this milieu, regarded as a whole unitary system and referred to as "niche". For many stem cell systems a niche has been identified, but only partially defined. In regenerative medicine and tissue engineering, biomaterials are used to deliver stem cells in specific anatomical sites where a regenerative process is needed. In this context, biomaterials have to provide informative microenvironments mimicking a physiological niche. Stem cells may read and decode any biomaterial and modify their behavior and fate accordingly. Any material is therefore informative in the sense that its intrinsic nature and structure will anyway transmit a signal that will have to be decoded by colonizing cells. We still know very little of how to create local microenvironments, or artificial niches, that will govern stem cells behavior and their terminal fate. Here we will review some characteristics identifying specific niches and some of the requirements allowing stem cells differentiation processes. We will discuss on those biomaterials that are being projected/engineered/manufactured to gain the informative status necessary to drive proper molecular cross-talk and cell differentiation; specific examples will be proposed for bone and cartilage substitutes.

Study of the in vitro corrosion behavior and biocompatibility of Zr-2.5Nb and Zr-1.5Nb-1Ta (at%) crystalline alloys

The in vitro corrosion behavior and biocompatibility of two Zr alloys, Zr-2.5Nb, employed for the manufacture of CANDU reactor pressure tubes, and Zr-1.5Nb-1Ta (at%), for use as implant materials have been assessed and compared with those of Grade 2 Ti, which is known to be a highly compatible metallic biomaterial. The in vitro corrosion resistance was investigated by open circuit potential and electrochemical impedance spectroscopy (EIS) measurements, as a function of exposure time to an artificial physiological environment (Ringer's solution). Open circuit potential values indicated that both the Zr alloys and Grade 2 Ti undergo spontaneous passivation due to spontaneously formed oxide film passivating the metallic surface, in the aggressive environment. It also indicated that the tendency for the formation of a spontaneous oxide is greater for the Zr-1.5Nb-1Ta alloy and that this oxide has better corrosion protection characteristics than the ones formed on Grade 2 Ti or on the Zr-2.5Nb alloy. EIS study showed high impedance values for all samples, increasing with exposure time, indicating an improvement in corrosion resistance of the spontaneous oxide film. The fit obtained suggests a single passive film presents on the metals surface, improving their resistance with exposure time, presenting the highest values to the Zr-1.5Nb-1Ta alloy. For the biocompatibility analysis human osteosarcoma cell line (Saos-2) and human primary bone marrow stromal cells (BMSC) were used. Biocompatibility tests showed that Saos-2 cells grow rapidly, independently of the surface, due to reduced dependency from matrix deposition and microenvironment recognition. BMSC instead display a reduced proliferation, possibly caused by a reduced crosstalk with the metal surface microenvironment. However, once the substrate has been colonized, BMSC seem to respond properly to osteoinduction stimuli, thus supporting a substantial equivalence in the biocompatibility among the Zr alloys and Grade 2 titanium. In summary, high in vitro corrosion resistance together with satisfactory biocompatibility make the Zr-2.5Nb and Zr-1.5Nb-1Ta crystalline alloys promising biomaterials for surgical implants.

An interaction between hepatocyte growth factor and its receptor (c-MET) prolongs the survival of chronic lymphocytic leukemic cells through STAT3 phosphorylation: a potential role of mesenchymal cells in the disease

BACKGROUND

Chronic lymphocytic leukemia cells are characterized by an apparent longevity in vivo which is lost when they are cultured in vitro. Cellular interactions and factors provided by the microenvironment appear essential to cell survival and may protect leukemic cells from the cytotoxicity of conventional therapies. Understanding the cross-talk between leukemic cells and stroma is of interest for identifying signals supporting disease progression and for developing novel therapeutic strategies.

DESIGN AND METHODS

Different cell types, sharing a common mesenchymal origin and representative of various bone marrow components, were used to challenge the viability of leukemic cells in co-cultures and in contact-free culture systems. Using a bioinformatic approach we searched for genes shared by lineages prolonging leukemic cell survival and further analyzed their biological role in signal transduction experiments.

RESULTS

Human bone marrow stromal cells, fibroblasts, trabecular bone-derived cells and an osteoblast-like cell line strongly enhanced survival of leukemic cells, while endothelial cells and chondrocytes did not. Gene expression profile analysis indicated two soluble factors, hepatocyte growth factor and CXCL12, as potentially involved. We demonstrated that hepatocyte growth factor and CXCL12 are produced only by mesenchymal lineages that sustain the survival of leukemic cells. Indeed chronic lymphocytic leukemic cells express a functional hepatocyte growth factor receptor (c-MET) and hepatocyte growth factor enhanced the viability of these cells through STAT3 phosphorylation, which was blocked by a c-MET tyrosine kinase inhibitor. The role of hepatocyte growth factor was confirmed by its short interfering RNA-mediated knock-down in mesenchymal cells.

CONCLUSIONS

The finding that hepatocyte growth factor prolongs the survival of chronic lymphocytic leukemic cells is novel and we suggest that the interaction between hepatocyte growth factor-producing mesenchymal and neoplastic cells contributes to maintenance of the leukemic clone.

Regulation of human mesenchymal stem cell functions by an autocrine loop involving NAD+ release and P2Y11-mediated signaling

In several cell types, a regulated efflux of NAD(+) across Connexin 43 hemichannels (Cx43 HC) can occur, and extracellular NAD(+) (NAD(+)(e)) affects cell-specific functions. We studied the capability of bone marrow-derived human mesenchymal stem cells (MSC) to release intracellular NAD(+) through Cx43 HC. NAD(+) efflux, quantified by a sensitive enzymatic cycling assay, was significantly upregulated by low extracellular Ca(2+) (5-6-fold), by shear stress (13-fold), and by inflammatory conditions (3.1- and 2.5-fold in cells incubated with lipopolysaccharide (LPS) or at 39°C, respectively), as compared with untreated cells, whereas it was downregulated in Cx43-siRNA-transfected MSC (by 53%) and by cell-to-cell contact (by 45%). Further, we show that NAD(+)(e) activates the purinergic receptor P2Y(11) and a cyclic adenosin monophosphate (cAMP)/cyclic ADP-ribose/[Ca(2+)](i) signaling cascade, involving the opening, unique to MSC, of L-type Ca(2+) channels. Extracellular NAD(+) enhanced nuclear translocation of cAMP/Ca(2+)-dependent transcription factors. Moreover, NAD(+), either extracellularly added or autocrinally released, resulted in stimulation of MSC functions, including proliferation, migration, release of prostaglandin E(2) and cytokines, and downregulation of T lymphocyte proliferation compared with controls. No detectable modifications of MSC markers and of adipocyte or osteocyte differentiation were induced by NAD(+)(e). Controls included Cx43-siRNA transfected and/or NAD(+)-glycohydrolase-treated MSC (autocrine effects), and NAD(+)-untreated or P2Y(11)-siRNA-transfected MSC (exogenous NAD(+)). These findings suggest a potential beneficial role of NAD(+)(e) in modulating MSC functions relevant to MSC-based cell therapies.

Short-time survival and engraftment of bone marrow stromal cells in an ectopic model of bone regeneration

In tissue-engineered applications bone marrow stromal cells (BMSCs) are combined with scaffolds to target bone regeneration; animal models have been devised and the cells' long-term engraftment has been widely studied. However, in regenerated bone, the cell number is severely reduced with respect to the initially seeded BMSCs. This reflects the natural low cellularity of bone but underlines the selectivity of the differentiation processes. In this respect, we evaluated the short-term survival of BMSCs, transduced with the luciferase gene, after implantation of cell-seeded scaffolds in a nude mouse model. Cell proliferation/survival was assessed by bioluminescence imaging: light production was decreased by 30% on the first day, reaching a 50% loss within 48 h. Less than 5% of the initial signal remained after 2 months in vivo. Apoptotic BMSCs were detected within the first 2 days of implantation. Interestingly, the initial frequency of clonogenic progenitors matched the percentage of in vivo surviving cells. Cytokines and inflammation may contribute to the apoptotic onset at the implant milieu. However, preculturing cells with tumor necrosis factor alpha enhanced survival, allowing detection of 8.1% of the seeded BMSCs 2 months after implantation. Thus culturing conditions may reduce the apoptotic overload of seeded osteoprogenitors, strengthening the constructs' osteogenic potential.

Novel nanostructured scaffold for osteochondral regeneration: pilot study in horses

The present in vivo preliminary experiment is aimed at testing mechanical and biological behaviour of a new nano-structured composite multilayer biomimetic scaffold for the treatment of chondral and osteochondral defects. The three-dimensional biomimetic scaffold (Fin-Ceramica Faenza S.p.A., Faenza-Italy) was obtained by nucleating collagen fibrils with hydroxyapatite nanoparticles, in two configurations, bi- and tri-layered, to reproduce, respectively, chondral and osteochondral anatomy. Chondral defects (lateral condyle) and deep osteochondral defects (medial condyle) were made in the distal epiphysis of the third metacarpal bone of both forelimbs of two adult horses and treated respectively with the chondral and osteochondral grafts. Both animals were euthanised six months follow up. The images obtained at the second look arthroscopy evaluation, performed two months after surgery, demonstrated good filling of the chondral and osteo-chondral defects without any inflammatory reaction around and inside the lesions. At the histological analysis the growth of trabecular bone in the osteochondral lesion was evident. Only in one case, the whole thickness of the osteochondral lesion was filled by fibrocartilaginous tissue. The formation of a tidemark line was evident at the interface with the newly formed bone. Newly formed fibrocartilaginous tissue was present in the area of the chondral defect. Initial alignment of the collagen fibres was recognisable with polarised light in both groups. The results of the present pilot study showed that this novel osteochondral and chondral scaffold may act as a suitable matrix to facilitate orderly regeneration of bone and hyaline-like cartilage.