Poor Cell Retention Research Articles

Development of a Smart Wireless Multisensor Platform for an Optogenetic Brain Implant.

Implantable cell replacement therapies promise to completely restore the function of neural structures, possibly changing how we currently perceive the onset of neurodegenerative diseases. One of the major clinical hurdles for the routine implementation of stem cell therapies is poor cell retention and survival, demanding the need to better understand these mechanisms while providing precise and scalable approaches to monitor these cell-based therapies in both pre-clinical and clinical scenarios. This poses significant multidisciplinary challenges regarding planning, defining the methodology and requirements, prototyping and different stages of testing. Aiming toward an optogenetic neural stem cell implant controlled by a smart wireless electronic frontend, we show how an iterative development methodology coupled with a modular design philosophy can mitigate some of these challenges. In this study, we present a miniaturized, wireless-controlled, modular multisensor platform with fully interfaced electronics featuring three different modules: an impedance analyzer, a potentiostat and an optical stimulator. We show the application of the platform for electrical impedance spectroscopy-based cell monitoring, optical stimulation to induce dopamine release from optogenetically modified neurons and a potentiostat for cyclic voltammetry and amperometric detection of dopamine release. The multisensor platform is designed to be used as an opto-electric headstage for future in vivo animal experiments.

Engineered biomaterials in stem cell-based regenerative medicine

Abstract Stem cell-based regenerative therapies, which harness the self-renewal and differentiation properties of stem cells, have been in the spotlight due to their widespread applications in treating degenerative, aging, and other, generally intractable diseases. Therapeutically effective hematopoietic stem cells, mesenchymal stem cells, embryonic stem cells, and induced pluripotent stem cells have been used in numerous basic and translational studies with exciting results. However, pre-/post-transplantation issues of poor cell survival and retention, uncontrolled differentiation, and insufficient numbers of cells engrafted into host tissues are the major challenges in stem cell-based regenerative therapies. Engineered biomaterials have adjustable biochemical and biophysical properties that significantly affect cell behaviors, such as cell engraftment, survival, migration, and differentiation outcomes, thereby enhancing the engraftment of implanted stem cells and guiding tissue regeneration. Therefore, the combination of stem cell biology with bioengineered materials is a promising strategy to improve the therapeutic outcomes of stem cell-based regenerative therapy. In this review, we summarize the advances in the modulation of behaviors of stem cells via engineered biomaterials. We then present different approaches to harnessing bioengineered materials to enhance the transplantation of stem cells. Finally, we will provide future directions in regenerative therapy using stem cells.

Stem cells derived exosomes and biomaterials to modulate autophagy and mend broken hearts

Autophagy maintains cellular homeostasis and plays a crucial role in managing pathological conditions including ischemic myocardial injury leading to heart failure (HF). Despite treatments, no intervention can replace lost cardiomyocytes. Stem cell therapy offers potential for post-myocardial infarction repair but struggles with poor cell retention due to immune rejection. In the search for effective therapies, stem cell-derived extracellular vesicles (EVs), especially exosomes, have emerged as promising tools. These tiny bioactive molecule carriers play vital roles in intercellular communication and tissue engineering. They offer numerous therapeutic benefits including modulating immune responses, promoting tissue repair, and boosting angiogenesis. Additionally, biomaterials provide a conducive 3D microenvironment for cell, exosome, and biomolecule delivery, and enhance heart muscle strength, making it a comprehensive cardiac repair strategy. In this regard, the current review delves into the intricate application of extracellular vesicles (EVs) and biomaterials for managing autophagy in the heart muscle during cardiac injury. Central to our investigation is the exploration of how these elements interact within the context of cardiac repair and regeneration. Additionally, this review also casts light on the formidable challenges that plague this field, such as the issues of safety, efficacy, controlled delivery, and acceptance of these therapeutic strategies for effective clinical translation. Addressing these challenges is crucial for unlocking the full therapeutic potential of EV and biomaterial-based therapies and ensuring their successful translation from bench to bedside.

A composite hydrogel improves the survival and differentiation of human iPSC-derived neural stem cells after ischemic stroke

Stem cell transplantation can replace lost and damaged neurons after ischemic stroke and has been proposed as a potential treatment for stroke. However, stem cell therapy is challenged by poor cell retention, survival, and differentiation following transplantation. In this study, we developed a composite hydrogel incorporating brain decellularized extracellular matrix (dECM) and a matrix metallopeptidase (MMP)-responsive host–guest (HG) hydrogel that acts as a platform for human induced pluripotent stem cell-derived neural stem cells (iPSC-NSCs) delivery to improve transplant stem cell survival and differentiation. The optimized composite hydrogel ratio was screened by rheology analysis and neurite outgrowth assessment. We then examined the effects of HG/dECM composite hydrogels on iPSC-NSCs survival and differentiation on two-dimensional surfaces modified with hydrogel and in a three-dimensional hydrogel network. Moreover, iPSC-NSCs-laden composite hydrogels were injected into the infarct cavity in an ischemic stroke model to replace lost and damaged nerve cells. As expected, the HG/dECM composite hydrogels better facilitated the survival and differentiation of iPSC-NSC in vivo than the control. Likewise, the iPSC-NSCs loaded in HG/dECM composite hydrogels showed superior retention and survival in the cortical infarct cavity, and the composite hydrogels promoted the differentiation of iPSC-NSCs into neurons. Overall, HG/dECM composite hydrogels are a promising platform to regulate stem cell survival and differentiation.

Degradable Biocompatible Porous Microtube Scaffold for Extended Donor Cell Survival and Activity.

Cell therapy has significant therapeutic potential but is often limited by poor donor cell retention and viability at the host implantation site. Biomaterials can improve cell retention by providing cells with increased cell-cell and cell-matrix contacts and materials that allow three-dimensional cell culture to better recapitulate native cell morphology and function. In this study, we engineered a scaffold that allows for cell encapsulation and sustained three-dimensional cell culture. Since cell therapy is largely driven by paracrine secretions, the material was fabricated by electrospinning to have a large internal surface area, micrometer-thin walls, and nanoscale surface pores to allow for nutrient exchange without early cell permeation. The material is degradable, which allows for less invasive removal of the implant. Here, a biodegradable poly(lactic-co-glycolic acid) (PLGA) microtube array membrane was fabricated. In vitro testing showed that the material supported the culture of human dermal fibroblasts for at least 21 days, with paracrine secretion of pro-angiogenic FGF2. In vivo xenotransplantation of human cells in an immunocompetent mouse showed that donor cells could be maintained for more than one month and the material showed no obvious toxicity. Analysis of gene expression and tissue histology surrounding the implant showed that the material produced muted inflammatory and immune responses compared to a permanent implant and increased markers of angiogenesis.

Bioinspired drug delivery strategies for repurposing conventional antibiotics against intracellular infections.

Bacteria have developed a wealth of strategies to avoid and resist the action of antibiotics, one of which involves pathogens invading and forming reservoirs within host cells. Due to the poor cell membrane permeability, stability and retention of conventional antibiotics, this renders current treatments largely ineffective, since achieving a therapeutically relevant antibiotic concentration at the site of intracellular infection is not possible. To overcome such challenges, current antibiotics are 'repurposed' via reformulation using micro- or nano-carrier systems that effectively encapsulate and deliver therapeutics across cellular membranes of infected cells. Bioinspired materials that imitate the uptake of biological particulates and release antibiotics in response to natural stimuli are recently explored to improve the targeting and specificity of this 'nanoantibiotic' approach. In this review, the mechanisms of internalization and survival of intracellular bacteria are elucidated, effectively accentuating the current treatment challenges for intracellular infections and the implications for repurposing conventional antibiotics. Key case studies of nanoantibiotics that have drawn inspiration from natural biological particles and cellular uptake pathways to effectively eradicate intracellular pathogens are detailed, clearly highlighting the rational for harnessing bioinspired drug delivery strategies.

Dual Stem Cell Therapy Improves the Myocardial Recovery Post-Infarction through Reciprocal Modulation of Cell Functions.

Mesenchymal stromal cells (MSC) are promising candidates for regenerative therapy of the infarcted heart. However, poor cell retention within the transplantation site limits their potential. We hypothesized that MSC benefits could be enhanced through a dual-cell approach using jointly endothelial colony forming cells (ECFC) and MSC. To assess this, we comparatively evaluated the effects of the therapy with MSC and ECFC versus MSC-only in a mouse model of myocardial infarction. Heart function was assessed by echocardiography, and the molecular crosstalk between MSC and ECFC was evaluated in vitro through direct or indirect co-culture systems. We found that dual-cell therapy improved cardiac function in terms of ejection fraction and stroke volume. In vitro experiments showed that ECFC augmented MSC effector properties by increasing Connexin 43 and Integrin alpha-5 and the secretion of healing-associated molecules. Moreover, MSC prompted the organization of ECFC into vascular networks. This indicated a reciprocal modulation in the functionality of MSC and ECFC. In conclusion, the crosstalk between MSC and ECFC augments the therapeutic properties of MSC and enhances the angiogenic properties of ECFC. Our data consolidate the dual-cell therapy as a step forward for the development of effective treatments for patients affected by myocardial infarction.

Selective Proliferation of Highly Functional Adipose-Derived Stem Cells in Microgravity Culture with Stirred Microspheres.

Therapeutic effects of adult stem-cell transplantations are limited by poor cell-retention in target organs, and a reduced potential for optimal cell differentiation compared to embryonic stem cells. However, contemporary studies have indicated heterogeneity within adult stem-cell pools, and a novel culturing technique may address these limitations by selecting those for cell proliferation which are highly functional. Here, we report the preservation of stemness in human adipose-derived stem cells (hASCs) by using microgravity conditions combined with microspheres in a stirred suspension. The cells were bound to microspheres (100−300 μm) and cultured using a wave-stirring shaker. One-week cultures using polystyrene and collagen microspheres increased the proportions of SSEA-3(+) hASCs 4.4- and 4.3-fold (2.7- and 2.9-fold increases in their numbers), respectively, compared to normal culture conditions. These cultured hASCs expressed higher levels of pluripotent markers (OCT4, SOX2, NANOG, MYC, and KLF), and had improved abilities for proliferation, colony formation, network formation, and multiple-mesenchymal differentiation. We believe that this novel culturing method may further enhance regenerative therapies using hASCs.

Effect of Intramyocardial Grafting Collagen Scaffold With Mesenchymal Stromal Cells in Patients With Chronic Ischemic Heart Disease

Cell therapy may be helpful for cardiac disease but has been fraught with poor cell retention and survival after transplantation. To determine whether cell-laden hydrogel treatment is safe and feasible for patients with chronic ischemic heart disease (CIHD). This randomized, double-blind clinical trial was conducted between March 1, 2016, and August 31, 2019, at a single hospital in Nanjing, China. Among 115 eligible patients with CIHD, 50 patients with left ventricular ejection fraction of 45% or less were selected to receive elective coronary artery bypass grafting (CABG) and additionally randomized to cell-plus-collagen treatment (collagen/cell group), cell treatment alone (cell group), or a control group. Sixty-five patients were excluded because of severe comorbidities or unwillingness to participate. Forty-four participants (88%) completed the study. The last patient completed 12 months of follow-up in August 2019. Analyses were prespecified and included all patients with available data. During CABG, patients in the collagen/cell group were treated with human umbilical cord-derived mesenchymal stromal cell (hUC-MSC)-laden collagen hydrogel intramyocardial injection, and the cell group was treated with hUC-MSCs alone. Patients in the control group underwent CABG alone. The primary outcome was safety of the cell-laden collagen hydrogel assessed by the incidence of serious adverse events. The secondary end point was the efficacy of treatment, according to cardiovascular magnetic resonance imaging-based left ventricular ejection fraction and infarct size. Fifty patients (mean [SD] age, 62.6 [8.3] years; 38 men [76%]) were enrolled, of whom 18 were randomized to the collagen/cell group, 17 to the cell group, and 15 to the control group. Patient characteristics did not differ among groups at baseline. For the primary end point, no significant differences in serious adverse events, myocardial damage markers, and renal or liver function were observed among all groups after treatment; the collagen/cell and cell groups each had 1 case of hospitalization because of heart failure, and no serious adverse events were seen in the control group. At 12 months after treatment, the mean infarct size percentage change was -3.1% (95% CI, -6.20% to -0.02%; P = .05) in the collagen/cell group, 5.19% (-1.85% to 12.22%, P = .35) in the cell group, and 8.59% (-3.06% to 20.25%, P = .21) in the control group. This study provides, to our knowledge, the first clinical evidence that the use of collagen hydrogel is safe and feasible for cell delivery. These findings provide a basis for larger clinical studies. ClinicalTrials.gov Identifier: NCT02635464.

Stem cell viability and proliferation is maintained in vivo using an alginate patch designed for epicardial administration

Background & Aim Cell-based therapies for the regeneration of the heart have demonstrated clinical safety but failed to show efficacy. This was attributed to poor cell retention and low integration of the cells into the tissue. We aim at developing a cardiac patch that will preserve cell viability and deliver functional cells into the heart. Methods, Results & Conclusion We employed the cryo-gelation method for the cross-linking of methacrylate alginate patches using free radical polymerization. Epicardial cells derived from human embryonic stem cells (epi-hESC) on differentiation day 12 were seeded on the patch. Their in vitro viability (Alamar blue proliferation assay, confocal imaging by the LIVE/DEAD® staining) and migratory potential were assessed over time. Patches loaded with luciferase-expressing mouse mesenchymal stem cells (mMSC) were injected subcutaneously in the dorsal area of BALB/c mice. Cells were monitored in vivo by bioluminescence and cell integration in the muscle was assessed by histology. An ultrasound guided injection method in the pericardial space of rodents was developed and cell-loaded radiolabelled patches were administered on the heart of BALB/c mice. The patches and the cells were monitored over 7 days using SPECT and bioluminesce. The patches were successfully seeded with 20’000 per mm2 epi-hESC. The cells formed clusters that were homogenously distributed within the patch, and their viability and proliferation were preserved over 4 days in vitro. The cells acquired a spindle shape migratory morphology by day 5. When administered in mice, the patch deployed and adhered on the dorsal muscle. The mMSC loaded in the patch survived in vivo over more than 8 days. When administered in the pericardial space of the rat, the patch deployed and remained confined between the pericardium and the surface of the heart. The viability of stem cell-derived somatic cells can be preserved in vivo using shape memory alginate scaffolds. These cardiac cells could enhance cardiac regeneration through paracrine signalling or integration of the cells in the heart.

Healing the Broken Heart; The Immunomodulatory Effects of Stem Cell Therapy.

Cardiovascular Disease (CVD) is a leading cause of mortality within the United States. Current treatments being administered to patients who suffered a myocardial infarction (MI) have increased patient survival, but do not facilitate the replacement of damaged myocardium. Recent studies demonstrate that stem cell-based therapies promote myocardial repair; however, the poor engraftment of the transferred stem cell populations within the infarcted myocardium is a major limitation, regardless of the cell type. One explanation for poor cell retention is attributed to the harsh inflammatory response mounted following MI. The inflammatory response coupled to cardiac repair processes is divided into two distinct phases. The first phase is initiated during ischemic injury when necrosed myocardium releases Danger Associated Molecular Patterns (DAMPs) and chemokines/cytokines to induce the activation and recruitment of neutrophils and pro-inflammatory M1 macrophages (MΦs); in turn, facilitating necrotic tissue clearance. During the second phase, a shift from the M1 inflammatory functional phenotype to the M2 anti-inflammatory and pro-reparative functional phenotype, permits the resolution of inflammation and the establishment of tissue repair. T-regulatory cells (Tregs) are also influential in mediating the establishment of the pro-reparative phase by directly regulating M1 to M2 MΦ differentiation. Current studies suggest CD4+ T-lymphocyte populations become activated when presented with autoantigens released from the injured myocardium. The identity of the cardiac autoantigens or paracrine signaling molecules released from the ischemic tissue that directly mediate the phenotypic plasticity of T-lymphocyte populations in the post-MI heart are just beginning to be elucidated. Stem cells are enriched centers that contain a diverse paracrine secretome that can directly regulate responses within neighboring cell populations. Previous studies identify that stem cell mediated paracrine signaling can influence the phenotype and function of immune cell populations in vitro, but how stem cells directly mediate the inflammatory microenvironment of the ischemic heart is poorly characterized and is a topic of extensive investigation. In this review, we summarize the complex literature that details the inflammatory microenvironment of the ischemic heart and provide novel insights regarding how paracrine mediated signaling produced by stem cell-based therapies can regulate immune cell subsets to facilitate pro-reparative myocardial wound healing.

High oxygen preservation hydrogels to augment cell survival under hypoxic condition

Cell therapy is a promising approach for ischemic tissue regeneration. However, high death rate of delivered cells under low oxygen condition, and poor cell retention in tissues largely limit the therapeutic efficacy. Using cell carriers with high oxygen preservation has potential to improve cell survival. To increase cell retention, cell carriers that can quickly solidify at 37 °C so as to efficiently immobilize the carriers and cells in the tissues are necessary. Yet there lacks cell carriers with these combined properties. In this work, we have developed a family of high oxygen preservation and fast gelation hydrogels based on N-isopropylacrylamide (NIPAAm) copolymers. The hydrogels were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of NIPAAm, acrylate-oligolactide (AOLA), 2-hydroxyethyl methacrylate (HEMA), and methacrylate-poly(ethylene glycol)-perfluorooctane (MAPEGPFC). The hydrogel solutions exhibited sol-gel temperatures around room temperature and were flowable and injectable at 4°C. They can quickly solidify (≤6 s) at 37°C to form flexible gels. These hydrogels lost 9.4~29.4% of their mass after incubation in Dulbecco's Phosphate-Buffered Saline (DPBS) for 4 weeks. The hydrogels exhibited a greater oxygen partial pressure than DPBS after being transferred from a 21% O2 condition to a 1% O2 condition. When bone marrow mesenchymal stem cells (MSCs) were encapsulated in the hydrogels and cultured under 1% O2, the cells survived and proliferated during the 14-day culture period. In contrast, the cells experienced extensive death in the control hydrogel that had low oxygen preservation capability. The hydrogels possessed excellent biocompatibility. The final degradation products did not provoke cell death even when the concentration was as high as 15 mg/ml, and the hydrogel implantation did not induce substantial inflammation. These hydrogels are promising as cell carriers for cell transplantation into ischemic tissues. Statement of SignificanceStem cell therapy for ischemic tissues experiences low therapeutic efficacy largely due to poor cell survival under low oxygen condition. Using cell carriers with high oxygen preservation capability has potential to improve cell survival. In this work, we have developed a family of hydrogels with this property. These hydrogels promoted the encapsulated stem cell survival and growth under low oxygen condition.

Injectable supramolecular polymer-nanoparticle hydrogels enhance human mesenchymal stem cell delivery.

Stem cell therapies have emerged as promising treatments for injuries and diseases in regenerative medicine. Yet, delivering stem cells therapeutically can be complicated by invasive administration techniques, heterogeneity in the injection media, and/or poor cell retention at the injection site. Despite these issues, traditional administration protocols using bolus injections in a saline solution or surgical implants of cell‐laden hydrogels have highlighted the promise of cell administration as a treatment strategy. To address these limitations, we have designed an injectable polymer–nanoparticle (PNP) hydrogel platform exploiting multivalent, noncovalent interactions between modified biopolymers and biodegradable nanoparticles for encapsulation and delivery of human mesenchymal stem cells (hMSCs). hMSC‐based therapies have shown promise due to their broad differentiation capacities and production of therapeutic paracrine signaling molecules. In this work, the fundamental hydrogel mechanical properties that enhance hMSC delivery processes are elucidated using basic in vitro models. Further, in vivo studies in immunocompetent mice reveal that PNP hydrogels enhance hMSC retention at the injection site and retain administered hMSCs locally for upwards of 2 weeks. Through both in vitro and in vivo experiments, we demonstrate a novel scalable, synthetic, and biodegradable hydrogel system that overcomes current limitations and enables effective cell delivery.

Abstract 418: Ready-made Microvessels Robustly Integrate Into the Infarcted Coronary Vasculature Promoting Graft Perfusion, Enhancing Cardiac Remuscularization and Function

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) offer an unprecedented opportunity to remuscularize infarcted hearts. However, the majority of hiPSC-CMs die post transplantation into the ischemic environment, limiting their regenerative potential. CM death occurs in the first few days post-transplantation due to ischemia. Attempts to promote intramyocardial vascularization (i.e. delivery of growth factors or cells) have not led to significant improvements due to poor cell retention and the long time required for new vessels to form and carry blood compared to the rapid death of transplanted CMs. Here, we used ready-made microvessels harvested from adipose tissue - that form a vasculature and carry blood within the first days post subcutaneous implantation - to re-vascularize ischemic rat hearts and improve hiPSC-CM survival. We performed left anterior descending artery ligation in immunocompromised rats to model MI. hiPSC-CMs (10 x10 6 ) with (CM+V) or without (CM-only, control) microvessels were delivered by intra-myocardial injection 2 weeks post MI. Cardiac function was assessed by echocardiography and pressure-volume loop. Delivery of microvessels from GFP rats allowed assessment of microvessel persistence. Compared to hiPSC-CM transplantation alone, microvessels promoted a 6-fold increase in hiPSC-CM survival, with reduction in scar size and a significantly superior functional recovery. While delivery of CM-only stabilized the heart preventing further fractional shortening decline, delivery of CM+V resulted in reversal of fractional shortening loss. This was supported by PV-loop data (ejection fraction: sham, ~20%; CM-only, ~31%; CM+V, ~39%; 4 wks). Moreover, microvessels showed unprecedented persistence and integration (>60%, 4 wks), resulting in 2-fold increase in vessel area and graft perfusion (as early as day 5 post-transplantation). This was achieved despite the very low number of cells (~2 x10 5 ) delivered in the form of microvessels. These findings provide a novel approach to cell-based therapies for MI whereby incorporation of ready-made microvessels can serve as a personalized delivery system to improve functional outcomes in cell replacement therapies.

Intravascular Stem Cell Bioreactor for Prevention of Adverse Remodeling After Myocardial Infarction.

BackgroundPrevention of adverse remodeling after myocardial infarction (MI) is an important goal of stem cell therapy. Clinical trial results vary, however, and poor cell retention and survival after delivery likely limit the opportunity to exert beneficial effects. To overcome these limitations, we built an implantable intravascular bioreactor (IBR) designed to protect contained cells from washout, dilution, and immune attack while allowing sustained release of beneficial paracrine factors.Methods and Results IBRs were constructed using semipermeable membrane adhered to a clinical‐grade catheter shaft. Mesenchymal stem cell (MSC) viability in and paracrine factor release from IBRs were assessed in vitro and IBR biocompatibility and immune protection confirmed in vivo. In a porcine anterior MI model, IBRs containing 25 million allogeneic MSCs (IBR‐MSCs) were compared with IBRs containing media alone (IBR‐Placebo; n=8 per group) with adverse remodeling assessed by magnetic resonance imaging. Four weeks after MI, IBR‐MSCs had no significant change in end‐diastolic volume (+0.33±4.32 mL; P=0.89), end‐systolic volume (+2.14±4.13 mL; P=0.21), and left ventricular ejection fraction (−2.27±2.94; P=0.33) while IBR‐Placebo had significant increases in end‐diastolic volume (+10.37±3.84 mL; P=0.01) and ESV (+11.35±2.88 mL; P=0.01), and a significant decrease in left ventricular ejection fraction (−5.78±1.70; P=0.025). Eight weeks after MI, adherent pericarditis was present in 0 of 8 IBR‐MSCs versus 4 of 8 IBR‐Placebo (P=0.02), suggesting an anti‐inflammatory effect. In a separate study, 25 million allogeneic pig MSCs directly injected in the peri‐infarct zone 3 days after MI (n=6) showed no significant benefit in adverse remodeling at 4 weeks compared with IBR‐MSCs.Conclusions MSCs deployed inside an implantable, removable, and potentially rechargeable bioreactor in a large animal model remain viable, are immunoprotected, and attenuate adverse remodeling 4 weeks after MI.

Encapsulation of macrophages enhances their retention and angiogenic potential

Cell therapies to treat critical limb ischaemia have demonstrated only modest results in clinical trials, and this has been partly attributed to poor cell retention following their delivery directly into the ischaemic limb. The aim of this study was to determine whether alginate encapsulation of therapeutic pro-angio/arteriogenic macrophages enhances their retention and ultimately improves limb perfusion. A reproducible GMP-compliant method for generating 300 µm alginate capsules was developed to encapsulate pro-angio/arteriogenic macrophages. Longitudinal analysis revealed no detrimental effect of encapsulation on cell number or viability in vitro, and macrophages retained their pro-angio/arteriogenic phenotype. Intramuscular delivery of encapsulated macrophages into the murine ischaemic hindlimb demonstrated increased cell retention compared with injection of naked cells (P = 0.0001), and that this was associated both enhanced angiogenesis (P = 0.02) and arteriogenesis (P = 0.03), and an overall improvement in limb perfusion (P = 0.0001). Alginate encapsulation of pro-angio/arteriogenic macrophages enhances cell retention and subsequent limb reperfusion in vivo. Encapsulation may therefore represent a means of improving the efficacy of cell-based therapies currently under investigation for the treatment of limb ischaemia.

Transcutaneously refillable, 3D-printed biopolymeric encapsulation system for the transplantation of endocrine cells

Autologous cell transplantation holds enormous promise to restore organ and tissue functions in the treatment of various pathologies including endocrine, cardiovascular, and neurological diseases among others. Even though immune rejection is circumvented with autologous transplantation, clinical adoption remains limited due to poor cell retention and survival. Cell transplant success requires homing to vascularized environment, cell engraftment and importantly, maintenance of inherent cell function. To address this need, we developed a three dimensional (3D) printed cell encapsulation device created with polylactic acid (PLA), termed neovascularized implantable cell homing and encapsulation (NICHE).In this paper, we present the development and systematic evaluation of the NICHE in vitro, and the in vivo validation with encapsulated testosterone-secreting Leydig cells in Rag1−/− castrated mice. Enhanced subcutaneous vascularization of NICHE via platelet-rich plasma (PRP) hydrogel coating and filling was demonstrated in vivo via a chorioallantoic membrane (CAM) assay as well as in mice. After establishment of a pre-vascularized bed within the NICHE, transcutaneously transplanted Leydig cells, maintained viability and robust testosterone secretion for the duration of the study. Immunohistochemical analysis revealed extensive Leydig cell colonization in the NICHE. Furthermore, transplanted cells achieved physiologic testosterone levels in castrated mice. The promising results provide a proof of concept for the NICHE as a viable platform technology for autologous cell transplantation for the treatment of a variety of diseases.

Retention and Functional Effect of Adipose-Derived Stromal Cells Administered in Alginate Hydrogel in a Rat Model of Acute Myocardial Infarction.

Background Cell therapy for heart disease has been proven safe and efficacious, despite poor cell retention in the injected area. Improving cell retention is hypothesized to increase the treatment effect. In the present study, human adipose-derived stromal cells (ASCs) were delivered in an in situ forming alginate hydrogel following acute myocardial infarction (AMI) in rats. Methods ASCs were transduced with luciferase and tested for ASC phenotype. AMI was inducted in nude rats, with subsequent injection of saline (controls), 1 × 106 ASCs in saline or 1 × 106 ASCs in 1% (w/v) alginate hydrogel. ASCs were tracked by bioluminescence and functional measurements were assessed by magnetic resonance imaging (MRI) and 82rubidium positron emission tomography (PET). Results ASCs in both saline and alginate hydrogel significantly increased the ejection fraction (7.2% and 7.8% at 14 days and 7.2% and 8.0% at 28 days, resp.). After 28 days, there was a tendency for decreased infarct area and increased perfusion, compared to controls. No significant differences were observed between ASCs in saline or alginate hydrogel, in terms of retention and functional salvage. Conclusion ASCs improved the myocardial function after AMI, but administration in the alginate hydrogel did not further improve retention of the cells or myocardial function.

Recombinant human collagen-based microspheres mitigate cardiac conduction slowing induced by adipose tissue-derived stromal cells.

BackgroundStem cell therapy to improve cardiac function after myocardial infarction is hampered by poor cell retention, while it may also increase the risk of arrhythmias by providing an arrhythmogenic substrate. We previously showed that porcine adipose tissue-derived-stromal cells (pASC) induce conduction slowing through paracrine actions, whereas rat ASC (rASC) and human ASC (hASC) induce conduction slowing by direct coupling. We postulate that biomaterial microspheres mitigate the conduction slowing influence of pASC by interacting with paracrine signaling.AimTo investigate the modulation of ASC-loaded recombinant human collagen-based microspheres, on the electrophysiological behavior of neonatal rat ventricular myocytes (NRVM).MethodUnipolar extracellular electrograms, derived from microelectrode arrays (8x8 electrodes) containing NRVM, co-cultured with ASC or ASC loaded microspheres, were used to determine conduction velocity (CV) and conduction heterogeneity. Conditioned medium (Cme) of (co)cultures was used to assess paracrine mechanisms.ResultsMicrospheres did not affect CV in control (NRVM) monolayers. In co-cultures of NRVM and rASC, hASC or pASC, CV was lower than in controls (14.4±1.0, 13.0±0.6 and 9.0± 1.0 vs. 19.5±0.5 cm/s respectively, p<0.001). Microspheres loaded with either rASC or hASC still induced conduction slowing compared to controls (13.5±0.4 and 12.6±0.5 cm/s respectively, p<0.001). However, pASC loaded microspheres increased CV of NRVM compared to pASC and NRMV co-cultures (16.3±1.3 cm/s, p< 0.001) and did not differ from controls (p = NS). Cme of pASC reduced CV in control monolayers of NRVM (10.3±1.1 cm/s, p<0.001), similar to Cme derived from pASC-loaded microspheres (11.1±1.7 cm/s, p = 1.0). The presence of microspheres in monolayers of NRVM abolished the CV slowing influence of Cme pASC (15.9±1.0 cm/s, p = NS vs. control).ConclusionThe application of recombinant human collagen-based microspheres mitigates indirect paracrine conduction slowing through interference with a secondary autocrine myocardial factor.

Adipose Extracellular Matrix/Stromal Vascular Fraction Gel: A Novel Adipose Tissue-Derived Injectable for Stem Cell Therapy.

Adipose-derived stem cells and other stromal vascular fraction cells were used more often for stem cell therapy, even though limitations such as poor cell retention rate, complicated and expensive isolation processes, and the use of specific laboratory equipment need to be overcome. Here, the authors developed a novel but simple method for generating an injectable mixture of stromal vascular fraction cells and native adipose extracellular matrix. It is a purely mechanical process in which lipoaspirate is processed into an extracellular matrix/stromal vascular fraction gel. The standard processing procedure was established using quantized tests. The therapeutic potential of the product for wound healing was then tested. Extracellular matrix/stromal vascular fraction gel derived from lipoaspirate and processed using a standard Coleman technique, followed by 1 minute of mechanical processing by passage back and forth between two 10-ml syringes at a flow rate of 10 ml/second, showed the highest adipose-derived stem cell and endothelial cell density. The stromal vascular fraction cells within the product also showed potential for multipotent differentiation similar to that of normal fat samples. In addition, the product showed better therapeutic results than stromal vascular fraction cell suspension when used to treat a nude mouse model of wound healing. Extracellular matrix/stromal vascular fraction gel is an autologous injectable derived from native extracellular matrix and is a functional cellular component generated using a simple mechanical process. As such, it may offer a novel mode of tissue repair suitable for clinical application in stem cell therapies.