Ali OA, Mooney DJ. 13. From tissue engineering to therapeutic cancer vaccines: Original research article: Bioabsorbable polymer scaffolds for tissue engineering capable of sustained growth factor delivery, 2000. J Control Release. 2014;190 :54-6.
Kim J, Bencherif SA, Li WA, Mooney DJ. Cell-friendly inverse opal-like hydrogels for a spatially separated co-culture system. Macromol Rapid Commun. 2014;35 (18) :1578-86.Abstract
Three-dimensional macroporous scaffolds have extensively been studied for cell-based tissue engineering but their use is mostly limited to mechanical support for cell adhesion and growth on the surface of macropores. Here, a templated fabrication method is described to prepare cell-friendly inverse opal-like hydrogels (IOHs) allowing both cell encapsulation within the hydrogel matrix and cell seeding on the surface of macropores. Ionically crosslinked alginate microbeads and photocrosslinkable biocompatible polymers are used as a sacrificial template and as a matrix, respectively. The alginate microbeads are easily removed by a chelating agent, with minimal toxicity for the encapsulated cells during template removal. The outer surface of macropores in IOHs can also provide a space for cell adherence. The cells encapsulated or attached in IOHs are able to remain viable and to proliferate over time. The elastic modulus and cell-adhesion properties of IOHs can be easily controlled and tuned. Finally, it is demonstrated that IOH can be used to co-culture two distinct cell populations in different spatial positions. This cell-friendly IOH system provides a 3D scaffold for organizing different cell types in a controllable microenvironment to investigate biological processes such as stem cell niches or tumor microenvironments.
Branco da Cunha C, Klumpers DD, Li WA, Koshy ST, Weaver JC, Chaudhuri O, Granja PL, Mooney DJ. Influence of the stiffness of three-dimensional alginate/collagen-I interpenetrating networks on fibroblast biology. Biomaterials. 2014;35 (32) :8927-36.Abstract
Wound dressing biomaterials are increasingly being designed to incorporate bioactive molecules to promote healing, but the impact of matrix mechanical properties on the biology of resident cells orchestrating skin repair and regeneration remains to be fully understood. This study investigated whether tuning the stiffness of a model wound dressing biomaterial could control the behavior of dermal fibroblasts. Fully interpenetrating networks (IPNs) of collagen-I and alginate were fabricated to enable gel stiffness to be tuned independently of gel architecture, polymer concentration or adhesion ligand density. Three-dimensional cultures of dermal fibroblasts encapsulated within matrices of different stiffness were shown to promote dramatically different cell morphologies, and enhanced stiffness resulted in upregulation of key-mediators of inflammation such as IL-10 and COX-2. These findings suggest that simply modulating the matrix mechanical properties of a given wound dressing biomaterial deposited at the wound site could regulate the progression of wound healing.
Fonseca KB, Gomes DB, Lee K, Santos SG, Sousa A, Silva EA, Mooney DJ, Granja PL, Barrias CC. Injectable MMP-sensitive alginate hydrogels as hMSC delivery systems. Biomacromolecules. 2014;15 (1) :380-90.Abstract
Hydrogels with the potential to provide minimally invasive cell delivery represent a powerful tool for tissue-regeneration therapies. In this context, entrapped cells should be able to escape the matrix becoming more available to actively participate in the healing process. Here, we analyzed the performance of proteolytically degradable alginate hydrogels as vehicles for human mesenchymal stem cells (hMSC) transplantation. Alginate was modified with the matrix metalloproteinase (MMP)-sensitive peptide Pro-Val-Gly-Leu-Iso-Gly (PVGLIG), which did not promote dendritic cell maturation in vitro, neither free nor conjugated to alginate chains, indicating low immunogenicity. hMSC were entrapped within MMP-sensitive and MMP-insensitive alginate hydrogels, both containing cell-adhesion RGD peptides. Softer (2 wt % alginate) and stiffer (4 wt % alginate) matrices were tested. When embedded in a Matrigel layer, hMSC-laden MMP-sensitive alginate hydrogels promoted more extensive outward cell migration and invasion into the tissue mimic. In vivo, after 4 weeks of subcutaneous implantation in a xenograft mouse model, hMSC-laden MMP-sensitive alginate hydrogels showed higher degradation and host tissue invasion than their MMP-insensitive equivalents. In both cases, softer matrices degraded faster than stiffer ones. The transplanted hMSC were able to produce their own collagenous extracellular matrix, and were located not only inside the hydrogels, but also outside, integrated in the host tissue. In summary, injectable MMP-sensitive alginate hydrogels can act as localized depots of cells and confer protection to transplanted cells while facilitating tissue regeneration.
Arany PR, Huang GX, Gadish O, Feliz J, Weaver JC, Kim J, Yuen WW, Mooney DJ. Multi-lineage MSC differentiation via engineered morphogen fields. J Dent Res. 2014;93 (12) :1250-7.Abstract
Tissue loss due to oral diseases requires the healing and regeneration of tissues of multiple lineages. While stem cells are native to oral tissues, a current major limitation to regeneration is the ability to direct their lineage-specific differentiation. This work utilizes polymeric scaffold systems with spatiotemporally controlled morphogen cues to develop precise morphogen fields to direct mesenchymal stem cell differentiation. First, a simple three-layer scaffold design was developed that presented two spatially segregated, lineage-specific cues (Dentinogenic TGF-β1 and Osteogenic BMP4). However, this system resulted in diffuse morphogen fields, as assessed by the in vitro imaging of cell-signaling pathways triggered by the morphogens. Mathematical modeling was then exploited, in combination with incorporation of specific inhibitors (neutralizing antibodies or a small molecule kinase inhibitor) into each morphogen in an opposing spatial pattern as the respective morphogen, to design a five-layer scaffold that was predicted to yield distinct, spatially segregated zones of morphogen signaling. To validate this system, undifferentiated MSCs were uniformly seeded in these scaffold systems, and distinct mineralized tissue differentiation were noted within these morphogen zones. Finally, to demonstrate temporal control over morphogen signaling, latent TGF-β1 was incorporated into one region of a concentric scaffold design, and laser treatment was used to activate the morphogen on-demand and to induce dentin differentiation solely within that specific spatial zone. This study demonstrates a significant advance in scaffold design to generate precise morphogen fields that can be used to develop in situ models to explore tissue differentiation and may ultimately be useful in engineering multi-lineage tissues in clinical dentistry.
Sonpavde G, Pond GR, Armstrong AJ, Galsky MD, Leopold L, Wood BA, Wang S-L, Paolini J, Chen I, Chow-Maneval E, et al. Radiographic progression by Prostate Cancer Working Group (PCWG)-2 criteria as an intermediate endpoint for drug development in metastatic castration-resistant prostate cancer. BJU Int. 2014;114 (6b) :E25-E31.Abstract
OBJECTIVE: To investigate the association of radiographic progression defined by Prostate Cancer Working Group (PCWG)-2 guidelines and overall survival (OS) in men with metastatic castration-resistant prostate cancer (mCRPC). PATIENTS AND METHODS: Two trials that used PCWG-2 guidelines to define progression were analysed: a randomized phase II trial (n = 221) comparing first-line docetaxel-prednisone plus AT-101 or placebo, and a phase III trial (n = 873) comparing prednisone plus sunitinib or placebo after docetaxel-based chemotherapy. Cox proportional hazards regression models were used to estimate the association of radiographic progression with OS. Landmark analyses compared progressing patients with those who had not progressed. Sub-analyses compared patients removed from trial for progression vs other reasons. RESULTS: An increased risk of death was seen for radiographic progression at landmark times from 6 to 12 months with docetaxel-based therapy (hazard ratio [HR] >1.7 at all time-points). An increased risk of death was also seen with post-docetaxel prednisone alone or with sunitinib for progression at landmark times from 2 to 8 months (HR >2.7 at all time-points). Kendall's τ was 0.50 (P < 0.001) in the setting of docetaxel-based therapy and 0.34 (P < 0.001) in the post-docetaxel setting for association between radiographic progression and death amongst patients with both events. Removal from study due to radiographic progression was associated with a significantly lower OS compared with removal for other reasons in both trials. Limitations of a retrospective analysis apply and there was no central radiology review. CONCLUSIONS: Radiographic progression by PCWG-2 criteria was significantly associated with OS in patients with mCRPC receiving first-line docetaxel-based chemotherapy or post-docetaxel therapy. With external validation as a surrogate endpoint in trials showing survival benefits, the use of radiographic progression-free survival may expedite drug development in mCRPC, which has been hampered by the lack of intermediate endpoints.
Reinhart-King CA, Mooney DJ, Schaffer DV. The Young Innovators of Cellular and Molecular Bioengineering. Cell Mol Bioeng. 2014;7 (3) :291-292.
Kennedy S, Bencherif S, Norton D, Weinstock L, Mehta M, Mooney D. Rapid and extensive collapse from electrically responsive macroporous hydrogels. Adv Healthc Mater. 2014;3 (4) :500-7.Abstract
Electrically responsive hydrogels are created with interconnected macropores, which greatly enhance their ability to rapidly undergo volumetric collapse when subjected to moderate electric fields. When optimized, these electrogels are easily integrated into arrays capable of rapid configurational and chromatic optical modulations, and when loaded with drugs, are able to coordinate the delivery profile of multiple drugs.
Arany PR, Cho A, Hunt TD, Sidhu G, Shin K, Hahm E, Huang GX, Weaver J, Chen AC-H, Padwa BL, et al. Photoactivation of endogenous latent transforming growth factor-β1 directs dental stem cell differentiation for regeneration. Sci Transl Med. 2014;6 (238) :238ra69.Abstract
Rapid advancements in the field of stem cell biology have led to many current efforts to exploit stem cells as therapeutic agents in regenerative medicine. However, current ex vivo cell manipulations common to most regenerative approaches create a variety of technical and regulatory hurdles to their clinical translation, and even simpler approaches that use exogenous factors to differentiate tissue-resident stem cells carry significant off-target side effects. We show that non-ionizing, low-power laser (LPL) treatment can instead be used as a minimally invasive tool to activate an endogenous latent growth factor complex, transforming growth factor-β1 (TGF-β1), that subsequently differentiates host stem cells to promote tissue regeneration. LPL treatment induced reactive oxygen species (ROS) in a dose-dependent manner, which, in turn, activated latent TGF-β1 (LTGF-β1) via a specific methionine residue (at position 253 on LAP). Laser-activated TGF-β1 was capable of differentiating human dental stem cells in vitro. Further, an in vivo pulp capping model in rat teeth demonstrated significant increase in dentin regeneration after LPL treatment. These in vivo effects were abrogated in TGF-β receptor II (TGF-βRII) conditional knockout (DSPP(Cre)TGF-βRII(fl/fl)) mice or when wild-type mice were given a TGF-βRI inhibitor. These findings indicate a pivotal role for TGF-β in mediating LPL-induced dental tissue regeneration. More broadly, this work outlines a mechanistic basis for harnessing resident stem cells with a light-activated endogenous cue for clinical regenerative applications.
Park LK, Maione AG, Smith A, Gerami-Naini B, Iyer LK, Mooney DJ, Veves A, Garlick JA. Genome-wide DNA methylation analysis identifies a metabolic memory profile in patient-derived diabetic foot ulcer fibroblasts. Epigenetics. 2014;9 (10) :1339-49.Abstract
Diabetic foot ulcers (DFUs) are a serious complication of diabetes. Previous exposure to hyperglycemic conditions accelerates a decline in cellular function through metabolic memory despite normalization of glycemic control. Persistent, hyperglycemia-induced epigenetic patterns are considered a central mechanism that activates metabolic memory; however, this has not been investigated in patient-derived fibroblasts from DFUs. We generated a cohort of patient-derived lines from DFU fibroblasts (DFUF), and site- and age-matched diabetic foot fibroblasts (DFF) and non-diabetic foot fibroblasts (NFF) to investigate global and genome-wide DNA methylation patterns using liquid chromatography/mass spectrometry and the Illumina Infinium HumanMethylation450K array. DFFs and DFUFs demonstrated significantly lower global DNA methylation compared to NFFs (p = 0.03). Hierarchical clustering of differentially methylated probes (DMPs, p = 0.05) showed that DFFs and DFUFs cluster together and separately from NFFs. Twenty-five percent of the same probes were identified as DMPs when individually comparing DFF and DFUF to NFF. Functional annotation identified enrichment of DMPs associated with genes critical to wound repair, including angiogenesis (p = 0.07) and extracellular matrix assembly (p = 0.035). Identification of sustained DNA methylation patterns in patient-derived fibroblasts after prolonged passage in normoglycemic conditions demonstrates persistent metabolic memory. These findings suggest that epigenetic-related metabolic memory may also underlie differences in wound healing phenotypes and can potentially identify therapeutic targets.
Duda GN, Grainger DW, Frisk ML, Bruckner-Tuderman L, Carr A, Dirnagl U, Einhäupl KM, Gottschalk S, Gruskin E, Huber C, et al. Changing the mindset in life sciences toward translation: a consensus. Sci Transl Med. 2014;6 (264) :264cm12.Abstract
Participants at the recent Translate! 2014 meeting in Berlin, Germany, reached a consensus on the rate-limiting factor for advancing translational medicine.
Brudno Y, Silva EA, Kearney CJ, Lewin SA, Miller A, Martinick KD, Aizenberg M, Mooney DJ. Refilling drug delivery depots through the blood. Proc Natl Acad Sci U S A. 2014;111 (35) :12722-7.Abstract
Local drug delivery depots have significant clinical utility, but there is currently no noninvasive technique to refill these systems once their payload is exhausted. Inspired by the ability of nanotherapeutics to target specific tissues, we hypothesized that blood-borne drug payloads could be modified to home to and refill hydrogel drug delivery systems. To address this possibility, hydrogels were modified with oligodeoxynucleotides (ODNs) that provide a target for drug payloads in the form of free alginate strands carrying complementary ODNs. Coupling ODNs to alginate strands led to specific binding to complementary-ODN-carrying alginate gels in vitro and to injected gels in vivo. When coupled to a drug payload, sequence-targeted refilling of a delivery depot consisting of intratumor hydrogels completely abrogated tumor growth. These results suggest a new paradigm for nanotherapeutic drug delivery, and this concept is expected to have applications in refilling drug depots in cancer therapy, wound healing, and drug-eluting vascular grafts and stents.
Roche ET, Wohlfarth R, Overvelde JTB, Vasilyev NV, Pigula FA, Mooney DJ, Bertoldi K, Walsh CJ. A bioinspired soft actuated material. Adv Mater. 2014;26 (8) :1200-6.Abstract
A class of soft actuated materials that can achieve lifelike motion is presented. By embedding pneumatic actuators in a soft material inspired by a biological muscle fibril architecture, and developing a simple finite element simulation of the same, tunable biomimetic motion can be achieved with fully soft structures, exemplified here by an active left ventricle simulator.
Silva EA, Eseonu C, Mooney DJ. Endothelial cells expressing low levels of CD143 (ACE) exhibit enhanced sprouting and potency in relieving tissue ischemia. Angiogenesis. 2014;17 (3) :617-30.Abstract
The sprouting of endothelial cells from pre-existing blood vessels represents a critical event in the angiogenesis cascade. However, only a fraction of cultured or transplanted endothelial cells form new vessels. Moreover, it is unclear whether this results from a stochastic process or instead relates to certain endothelial cells having a greater angiogenic potential. This study investigated whether there exists a sub-population of cultured endothelial cells with enhanced angiogenic potency in vitro and in vivo. First, endothelial cells that participated in sprouting, and non-sprouting cells, were separately isolated from a 3D fibrin gel sprouting assay. Interestingly, the sprouting cells, when placed back into the same assay, displayed a sevenfold increase in the number of sprouts, as compared to control cells. Angiotensin-converting enzyme (CD143) was significantly down regulated on sprouting cells, as compared to regular endothelial cells. A subset of endothelial cells with low CD143 expression was then prospectively isolated from an endothelial cell culture. Finally, these cells were found to have greater potency in alleviating local ischemia, and restoring regional blood perfusion when transplanted into ischemic hindlimbs, as compared to unsorted endothelial cells. In summary, this study indicates that low expression of CD143 can be used as a biomarker to identify an endothelial cell sub-population that is more capable to drive neovascularization.
Koshy ST, Ferrante TC, Lewin SA, Mooney DJ. Injectable, porous, and cell-responsive gelatin cryogels. Biomaterials. 2014;35 (8) :2477-87.Abstract
The performance of biomaterials-based therapies can be hindered by complications associated with surgical implant, motivating the development of materials systems that allow minimally invasive introduction into the host. In this study, we created cell-adhesive and degradable gelatin scaffolds that could be injected through a conventional needle while maintaining a predefined geometry and architecture. These scaffolds supported attachment, proliferation, and survival of cells in vitro and could be degraded by recombinant matrix metalloproteinase-2 and -9. Prefabricated gelatin cryogels rapidly resumed their original shape when injected subcutaneously into mice and elicited only a minor host response following injection. Controlled release of granulocyte-macrophage colony-stimulating factor from gelatin cryogels resulted in complete infiltration of the scaffold by immune cells and promoted matrix metalloproteinase production leading to cell-mediated degradation of the cryogel matrix. These findings suggest that gelatin cryogels could serve as a cell-responsive platform for biomaterial-based therapy.
Madl CM, Mehta M, Duda GN, Heilshorn SC, Mooney DJ. Presentation of BMP-2 mimicking peptides in 3D hydrogels directs cell fate commitment in osteoblasts and mesenchymal stem cells. Biomacromolecules. 2014;15 (2) :445-55.Abstract
Many strategies for controlling the fate of transplanted stem cells rely on the concurrent delivery of soluble growth factors that have the potential to produce undesirable secondary effects in surrounding tissue. Such off target effects could be eliminated by locally presenting growth factor peptide mimics from biomaterial scaffolds to control stem cell fate. Peptide mimics of bone morphogenetic protein 2 (BMP-2) were synthesized by solid phase Fmoc-peptide synthesis and covalently bound to alginate hydrogels via either carbodiimide or sulfhydryl-based coupling strategies. Successful peptide conjugation was confirmed by (1)H NMR spectroscopy and quantified by fluorescently labeling the peptides. Peptides derived from the knuckle epitope of BMP-2, presented from both 2D surfaces and 3D alginate hydrogels, were shown to increase alkaline phosphatase activity in clonally derived murine osteoblasts. Furthermore, when presented in 3D hydrogels, these peptides were shown to initiate Smad signaling, upregulate osteopontin production, and increase mineral deposition with clonally derived murine mesenchymal stem cells. These data suggest that these peptide-conjugated hydrogels may be effective alternatives to local BMP-2 release in directly and spatially eliciting osteogenesis from transplanted or host osteoprogenitors in the future.
Cezar CA, Kennedy SM, Mehta M, Weaver JC, Gu L, Vandenburgh H, Mooney DJ. Biphasic ferrogels for triggered drug and cell delivery. Adv Healthc Mater. 2014;3 (11) :1869-76.Abstract
Ferrogels are an attractive material for many biomedical applications due to their ability to deliver a wide variety of therapeutic drugs on-demand. However, typical ferrogels have yet to be optimized for use in cell-based therapies, as they possess limited ability to harbor and release viable cells. Previously, an active porous scaffold that exhibits large deformations and enhanced biological agent release under moderate magnetic fields has been demonstrated. Unfortunately, at small device sizes optimal for implantation (e.g., 2 mm thickness), these monophasic ferrogels no longer achieve significant deformation due to a reduced body force. A new biphasic ferrogel, containing an iron oxide gradient, capable of large deformations and triggered release even at small gel dimensions, is presented in this study. Biphasic ferrogels demonstrate increased porosity, enhanced mechanical properties, and potentially increased biocompatibility due to their reduced iron oxide content. With their ability to deliver drugs and cells on-demand, it is expected that these ferrogels will have wide utility in the fields of tissue engineering and regenerative medicine.
Lee K, Weir MD, Lippens E, Mehta M, Wang P, Duda GN, Kim WS, Mooney DJ, Xu HHK. Bone regeneration via novel macroporous CPC scaffolds in critical-sized cranial defects in rats. Dent Mater. 2014;30 (7) :e199-207.Abstract
OBJECTIVES: Calcium phosphate cement (CPC) is promising for dental and craniofacial applications due to its ability to be injected or filled into complex-shaped bone defects and molded for esthetics, and its resorbability and replacement by new bone. The objective of this study was to investigate bone regeneration via novel macroporous CPC containing absorbable fibers, hydrogel microbeads and growth factors in critical-sized cranial defects in rats. METHODS: Mannitol porogen and alginate hydrogel microbeads were incorporated into CPC. Absorbable fibers were used to provide mechanical reinforcement to CPC scaffolds. Six CPC groups were tested in rats: (1) control CPC without macropores and microbeads; (2) macroporous CPC+large fiber; (3) macroporous CPC+large fiber+nanofiber; (4) same as (3), but with rhBMP2 in CPC matrix; (5) same as (3), but with rhBMP2 in CPC matrix+rhTGF-β1 in microbeads; (6) same as (3), but with rhBMP2 in CPC matrix+VEGF in microbeads. Rats were sacrificed at 4 and 24 weeks for histological and micro-CT analyses. RESULTS: The macroporous CPC scaffolds containing porogen, absorbable fibers and hydrogel microbeads had mechanical properties similar to cancellous bone. At 4 weeks, the new bone area fraction (mean±sd; n=5) in CPC control group was the lowest at (14.8±3.3)%, and that of group 6 (rhBMP2+VEGF) was (31.0±13.8)% (p<0.05). At 24 weeks, group 4 (rhBMP2) had the most new bone of (38.8±15.6)%, higher than (12.7±5.3)% of CPC control (p<0.05). Micro-CT revealed nearly complete bridging of the critical-sized defects with new bone for several macroporous CPC groups, compared to much less new bone formation for CPC control. SIGNIFICANCE: Macroporous CPC scaffolds containing porogen, fibers and microbeads with growth factors were investigated in rat cranial defects for the first time. Macroporous CPCs had new bone up to 2-fold that of traditional CPC control at 4 weeks, and 3-fold that of traditional CPC at 24 weeks, and hence may be useful for dental, craniofacial and orthopedic applications.
Roche ET, Hastings CL, Lewin SA, Shvartsman D, Brudno Y, Vasilyev NV, O'Brien FJ, Walsh CJ, Duffy GP, Mooney DJ. Comparison of biomaterial delivery vehicles for improving acute retention of stem cells in the infarcted heart. Biomaterials. 2014;35 (25) :6850-6858.Abstract
Cell delivery to the infarcted heart has emerged as a promising therapy, but is limited by very low acute retention and engraftment of cells. The objective of this study was to compare a panel of biomaterials to evaluate if acute retention can be improved with a biomaterial carrier. Cells were quantified post-implantation in a rat myocardial infarct model in five groups (n = 7-8); saline injection (current clinical standard), two injectable hydrogels (alginate, chitosan/β-glycerophosphate (chitosan/ß-GP)) and two epicardial patches (alginate, collagen). Human mesenchymal stem cells (hMSCs) were delivered to the infarct border zone with each biomaterial. At 24 h, retained cells were quantified by fluorescence. All biomaterials produced superior fluorescence to saline control, with approximately 8- and 14-fold increases with alginate and chitosan/β-GP injectables, and 47 and 59-fold increases achieved with collagen and alginate patches, respectively. Immunohistochemical analysis qualitatively confirmed these findings. All four biomaterials retained 50-60% of cells that were present immediately following transplantation, compared to 10% for the saline control. In conclusion, all four biomaterials were demonstrated to more efficiently deliver and retain cells when compared to a saline control. Biomaterial-based delivery approaches show promise for future development of efficient in vivo delivery techniques.
Kim J, Li WA, Sands W, Mooney DJ. Effect of pore structure of macroporous poly(lactide-co-glycolide) scaffolds on the in vivo enrichment of dendritic cells. ACS Appl Mater Interfaces. 2014;6 (11) :8505-12.Abstract
The in vivo enrichment of dendritic cells (DCs) in implanted macroporous scaffolds is an emerging strategy to modulate the adaptive immune system. The pore architecture is potentially one of the key factors in controlling enrichment of DCs. However, there have been few studies examining the effects of scaffold pore structure on in vivo DC enrichment. Here we present the effects of surface porosity, pore size, and pore volume of macroporous poly(lactide-co-glycolide) (PLG) scaffolds encapsulating granulocyte macrophage colony-stimulating factor (GM-CSF), an inflammatory chemoattractant, on the in vivo enrichment of DCs. Although in vitro cell seeding studies using PLG scaffolds without GM-CSF showed higher cell infiltration in scaffolds with higher surface porosity, in vivo results revealed higher DC enrichment in GM-CSF loaded PLG scaffolds with lower surface porosity despite a similar level of GM-CSF released. The diminished compressive modulus of high surface porosity scaffolds compared to low surface porosity scaffolds lead to the significant shrinkage of these scaffolds in vivo, suggesting that the mechanical strength of scaffolds was critical to maintain a porous structure in vivo for accumulating DCs. The pore volume was also found to be important in total number of recruited cells and DCs in vivo. Varying the pore size significantly impacted the total number of cells, but similar numbers of DCs were found as long as the pore size was above 10-32 μm. Collectively, these results suggested that one can modulate in vivo enrichment of DCs by altering the pore architecture and mechanical properties of PLG scaffolds.