Potential chemotherapeutic agents are subjected to many levels of preclinical screening which can fail at any time and, unfortunately, often do [...].

Technologies and biomaterials for 3D bioprinting have been developing extremely quickly in the past decade as they hold great potential in tissue engineering. This, together with the possibility to differentiate stem cells of different origin into any cell type, raises the hopes in regenerative medicine once again after the initial breakthrough with stem cells in the 1980s. Nevertheless, three decades of 3D bioprinting experiments have shown that the production of functional tissues would take a longer time than anticipated. Cartilage, one of the simplest tissues in the body, consists of only one cell type. It is not vascularised and innervated and does not have lymphatic vessels either, which makes it a perfect target tissue for successful implantation. The tremendous amount of work since the beginning of this century, combining the efforts of bioengineers, material scientists, biologists, and physicians, has culminated in multiple proof-of-concept constructs that have been implanted in animals. However, there is no single reproducible, standardised, widely accessible and accepted strategy that can be readily applied in the clinic. In this review, we focus on the current progress in the field of the 3D biofabrication of articular cartilage and critically assess failures and future challenges.

Cold atmospheric plasma (CAP) is a promising complement to tissue repair and regenerative medicine approaches. CAP has therapeutic potential in infected cutaneous wounds by mechanisms which remain enigmatic. Here, CAP is shown to activate phagocyte NADPH oxidase complex NOX2. CAP induced increased intracellular reactive oxygen species, alleviated by NOX2 inhibitors. Genetic and pharmacological inhibitions of NOX2 in macrophages and bioengineered skin infected with Staphylococcus aureus and treated with CAP reduced intracellular oxidants and increased bacterial survival. CAP triggered Rac activation and phosphorylation of p40phox and p47phox required for NOX2 assembly and activity. Furthermore, CAP induced collagen I expression by fibroblasts. Infection and healing kinetics showed that murine skin wounds infected with S. aureus and treated with CAP are characterized by decreased bacterial burden, increased length of neoepidermis and extracellular matrix formation. Collectively, our findings identify mechanisms triggered by CAP that subdue infection and result in enhanced repair following skin injury.

Oncolytic viral-delivered chemotherapeutics have exciting potential for metastatic cancer therapies, including colorectal cancer, but require advanced screening systems for better patient prediction. We optimized primary metastatic colorectal tumor processing and 3D (3-dimensional) bioprinted tumors to prove efficacy as long-term screening systems. Normally, this time period would use animals, but we show it is possible to gain useful data in vitro before preclinical stages, to reduce animal modeling and give better clinical trial predictions. Liver tumors were collected from 12 colorectal cancer patients, evaluated for expansion, 3D bioprinted, and tested for ability to create long-term organoid models with screening of oncolytic viral-loaded FCU1 enzyme conversion of 5-fluorocytosine (5-FC) into the highly toxic 5-fluorouracil (5-FU). Donated tumor size was the limiting factor. 75% of patients could be used for screening of viral delivery. Response between patients was overall positive, with good secondary tumor development, outer active cellular content and inner necrotic core. Oncolytic challenge shows good screening potential and cellular targeting, demonstrating an added bystander effect, optimizing the low-dose. Stable long-term metastatic organoid models were made, lasting many months, with potential for retesting rather than one-off analysis. Oncolytic virus-delivered chemotherapy is promising and warrants further investigation for metastatic colorectal cancers.

The tailoring of the skin microbiome is challenging and is a research hotspot in the pathogenesis of immune-mediated inflammatory skin diseases such as acne. Commonly encountered preservatives used as functional ingredients have an impact on the skin microbiota and are known to inhibit the survival of skin commensal bacteria. The selected species is Lactiplantibacillus plantarum, formulated with natural enhancers for topical use (SkinDuoTM). Ex vivo human skin models were used as a test system to assess the strain viability which was then validated on healthy volunteers. SkinDuoTM showed increased viability over time for in vitro skin models and a stable viability of over 50% on healthy skin. The strain was tested on human primary sebocytes obtained from sebaceous gland rich areas of facial skin and inoculated with the most abundant bacteria from the skin microbiota. Results on human ex vivo sebaceous gland models with the virulent phylotype of Cutibacterium acnes and Staphylococcus epidermidis present a significant reduction in viability, lipid production, and anti-inflammatory markers. We have developed an innovative anti-acne serum with L. plantarum that mimics the over-production of lipids, anti-inflammatory properties, and improves acne-disease skin models. Based on these results, we suggest that SkinDuoTM may be introduced as an acne-mitigating agent.

Acne-prone skin is associated with dysbiosis involving Cutibacterium acnes (C. acnes) and Staphylococcus epidermidis (S. epidermidis) causing increased seborrhea in sebaceous glands (SG) and inflammation. Human primary sebocytes were cultivated using 1.106 UFC/mL C. acnes Type IA (facial acne, ATCC6919) and/or 1.105 UFC/mL S. epidermidis (unknown origin, ATCC12228) for 48 h in our SEB4GLN-optimized media without antibiotics. Bacteria and sebocytes were enumerated and assessed to determine their viability. Lipid production was imaged and quantified via Nile Red staining. SG with hair follicles were microdissected from healthy skin and cultured using 1.105 UFC/mL C. acnes Type 1A and/or 1.104 UFC/mL S. epidermidis (wild-type facial skin strain) through prior fixation and immunostaining for MC5R, C. acnes and nuclei (DAPI) via Z-stack confocal microscopy bioimaging (Leica SP5X & FIJI software, Version 2.9.0). C. acnes growth was not impacted when co-cultivated with sebocytes (2D) or SG (3D) models. Phylotype IA stimulated sebocyte lipid production, which had no impact on viability. The S. epidermidis reference strain overproliferated, inducing sebocyte mortality. For 3D SG model, culture conditions were optimized using a wild-type facial skin strain at a lower concentration, 1:10 ratio to C. acnes, reduced contact time, sequential inoculation and rinsing step. Bioimaging revealed strong C. acnes labeling in the active areas of the pilosebaceous unit. S. epidermidis formed biofilm, which was distributed across the SG via non-specific fluorescence imaging. We developed an innovative model of a sebaceous gland that mimics acne-prone skin with lipid overproduction and virulent phylotype IA C. acnes inoculation.

Long-term modelization of cancer as it changes in the human body is a difficult goal, particularly when designing and testing new therapeutic strategies. This becomes even more difficult with metastasis modeling to show chemotherapeutic molecule delivery directly to tumoral cells. Advanced therapeutics, including oncolytic viruses, antibody-based and cell-based therapies are increasing. The question is, are screening tests also evolving? Next-generation therapeutics need equally advanced screening tests, which whilst difficult to achieve, are the goal of our work here, creating models of micro- and macrotumors using 3D bioprinting. We developed advanced colorectal cancer tumor processing techniques to provide options for cellular expansion, microtumor printing, and long-term models, which allow for the evaluation of the kinetics of penetration testing, therapeutic success, targeted therapies, and personalized medicine. We describe how we tested tumors from a primary colorectal patient and, applying 3D bioprinting, matured long-term models for oncolytic metastatic screening. Three-dimensional microtumors were kept alive for the longest time ever recorded in vitro, allowing longitudinal studies, screening of oncolytic viruses and realistic modelization of colorectal cancer. These 3D bioprinted models were maintained for around 6 months and were able to demonstrate the effective delivery of a product to the tumoral environment and represent a step forward in therapeutic screening.

Comedo, a clogged hair follicle, is one of the predisposing factors of acne. Comedo formation has been known to result from obstruction of the follicular orifice by hyperkeratosis, followed by sebum coagulation with corneocytes in the follicle [ [1] Goh C. Cheng C. Agak G. Zaenglein A.L. Graber E.M. Thiboutot D.M. et al. Acne vulgaris. in: Fitzpatrick’s Dermatology. McGraw-Hill Inc., US2019: 1391-1418 Google Scholar ]. However, since this process cannot sufficiently explain the formation of open comedo and microcomedo, where the follicular orifice is open, the detailed mechanism of comedo formation remains to be elucidated. In this study, we performed immunological and histological analyses using the follicular plug of the human nose and excised human skin, including clogged hair follicles, to investigate the mechanism of comedo formation.

Two-photon polymerization has recently emerged as a promising technique to fabricate scaffolds for three-dimensional (3D) cell culture and tissue engineering. Here, we combined 3D-printed microscale scaffolds fabricated using two-photon polymerization with a bioactive layer-by-layer film coating. This bioactive coating consists of hyaluronic acid and poly(l-lysine) of controlled stiffness, loaded with fibronectin and bone morphogenic proteins 2 and 4 (BMP2 and BMP4) as matrix-bound proteins. Planar films were prepared using a liquid handling robot directly in 96-well plates to perform high-content studies of cellular processes, especially cell adhesion, proliferation, and BMP-induced signaling. The behaviors of two human pancreatic cell lines PANC1 (immortalized) and PAN092 (patient-derived cell line) were systematically compared and revealed important context-specific cell responses, notably in response to film stiffness and matrix-bound BMPs (bBMPs). Fibronectin significantly increased cell adhesion, spreading, and proliferation for both cell types on soft and stiff films; BMP2 increased cell adhesion and inhibited proliferation of PANC1 cells and PAN092 on soft films. BMP4 enhanced cell adhesion and proliferation of PANC1 and showed a bipolar effect on PAN092. Importantly, PANC1 exhibited a strong dose-dependent BMP response, notably for bBMP2, while PAN092 was insensitive to BMPs. Finally, we proved that it is possible to combine a microscale 3D Ormocomp scaffold fabricated using the two-photon polymerization technique with the bioactive film coating to form a microscale tumor tissue and mimic the early stages of metastatic cancer.

Lack of skin vascularization or in contrast its hypervascularization are aggravating factors of some medical pathologies (ulcers and cancers) and dermo-cosmetics troubles (rosacea and dark circles). Thus, developing a suitable in vitro model to screen pharmaceutical and cosmetics ingredients able to stimulate or mitigate the angiogenesis process without changing the normal skin physiology are not easy and hampered by the existence of unreliable in vitro models. Traditional models of skin angiogenesis concentrate on analyzing the co-culture growth of endothelial cells with or without added fibroblasts or keratinocytes. However, these models do not work for topical applications and top-down layering analysis required for complex studies and do not translate well to clinical analysis. Here we describe the creation of a 3D bioprinted vascularized skin model, designed for screening those type of molecules. Human Dermal Microvascular Endothelial Cells, dermal fibroblasts and epidermal keratinocytes were harvested and expanded from juvenile foreskins. Cells were selected for optimal growth and mixed with a bioink into which adhesion proteins were added and cartridged into a CELLINK pneumatic 3D bioprinting system allowing the generation of 3D vascularized printed full thickness skins. Resulting skin models had a vascularization bed created in the lower quadrant of the dermal structure, which was confocal microscopy imaged with anti-CD31 fluorescent labelling. Reduction of epidermal growth factor and pituitary supplement resulted in the sequential reduction and cell death of the vascular bed over 14 days, whilst continual supplementation maintains the model and cellular interconnections. With 3D Bioprinting we can produce hundreds of models in one afternoon giving the potential to screen many combinations of molecules before moving to more expensive clinical experimentations.

Purpose: Compare pancreatic ductal adenocarcinoma (PDAC), preclinical models, by their transcriptome and drug response landscapes to evaluate their complementarity. Experimental Design: Three paired PDAC preclinical models—patient-derived xenografts (PDX), xenograft-derived pancreatic organoids (XDPO) and xenograft-derived primary cell cultures (XDPCC)—were derived from 20 patients and analyzed at the transcriptomic and chemosensitivity level. Transcriptomic characterization was performed using the basal-like/classical subtyping and the PDAC molecular gradient (PAMG). Chemosensitivity for gemcitabine, irinotecan, 5-fluorouracil and oxaliplatin was established and the associated biological pathways were determined using independent component analysis (ICA) on the transcriptome of each model. The selection criteria used to identify the different components was the chemosensitivity score (CSS) found for each drug in each model. Results: PDX was the most dispersed model whereas XDPO and XDPCC were mainly classical and basal-like, respectively. Chemosensitivity scoring determines that PDX and XDPO display a positive correlation for three out of four drugs tested, whereas PDX and XDPCC did not correlate. No match was observed for each tumor chemosensitivity in the different models. Finally, pathway analysis shows a significant association between PDX and XDPO for the chemosensitivity-associated pathways and PDX and XDPCC for the chemoresistance-associated pathways. Conclusions: Each PDAC preclinical model possesses a unique basal-like/classical transcriptomic phenotype that strongly influences their global chemosensitivity. Each preclinical model is imperfect but complementary, suggesting that a more representative approach of the clinical reality could be obtained by combining them. Translational Relevance: The identification of molecular signatures that underpin drug sensitivity to chemotherapy in PDAC remains clinically challenging. Importantly, the vast majority of studies using preclinical in vivo and in vitro models fail when transferred to patients in a clinical setting despite initially promising results. This study presents for the first time a comparison between three preclinical models directly derived from the same patients. We show that their applicability to preclinical studies should be considered with a complementary focus, avoiding tumor-based direct extrapolations, which might generate misleading conclusions and consequently the overlook of clinically relevant features.

Colorectal cancer (CRC) is the third most common malignancy and has recently moved up to the second leading cause of death among carcinomas. Prognosis, especially for advanced diseases or certain molecular subtypes of CRC, remains poor, which highlights the urgent need for better therapeutic strategies. However, currently, as little as 0.1% of all drugs make it from bench to bedside because of the inherently high false-positive and false-negative rates of current preclinical and clinical drug testing data. Therefore, the success of developing novel treatment agents lies in the introduction of improved preclinical disease models which resemble in vivo carcinomas closer, possess higher predictive properties, and offer opportunities for individualized therapies. Aiming to address these needs, we have established an affordable, flexible, and highly reproducible 3D bioprinted CRC model. The histological assessment of Caco-2 cells in 3D bioprints revealed the formation of glandular-like structures which show greater pathomorphological resemblance to tumors than monolayer cultures do. RNA expression profiles in 3D bioprinted cells were marked by upregulation of genes involved in cell adhesion, hypoxia, EGFR/KRAS signaling, and downregulation of cell cycle programs. Testing this 3D experimental platform with three of the most commonly used chemotherapeutics in CRC (5-fluoruracil, oxaliplatin, and irinotecan) revealed overall increased resistance compared to 2D cell cultures. Last, we demonstrate that our workflow can be successfully extended to primary CRC samples. Thereby, we describe a novel accessible platform for disease modeling and drug testing, which may present an innovative opportunity for personalized therapeutic screening.

Mesenchymal stem cells (MSCs) represent alternative candidates to chondrocytes for cartilage engineering. However, it remains difficult to identify the ideal source of MSCs for cartilage repair since conditions supporting chondrogenic induction are diverse among published works. In this study, we characterized and evaluated the chondrogenic potential of MSCs from bone marrow (BM), Wharton's jelly (WJ), dental pulp (DP), and adipose tissue (AT) isolated and cultivated under serum-free conditions. BM-, WJ-, DP-, and AT-MSCs did not differ in terms of viability, clonogenicity, and proliferation. By an extensive polychromatic flow cytometry analysis, we found notable differences in markers of the osteochondrogenic lineage between the 4 MSC sources. We then evaluated their chondrogenic potential in a micromass culture model, and only BM-MSCs showed chondrogenic conversion. This chondrogenic differentiation was specifically ascertained by the production of procollagen IIB, the only type II collagen isoform synthesized by well-differentiated chondrocytes. As a pilot study toward cartilage engineering, we encapsulated BM-MSCs in hydrogel and developed an original method to evaluate their chondrogenic conversion by flow cytometry analysis, after release of the cells from the hydrogel. This allowed the simultaneous quantification of procollagen IIB and α10, a subunit of a type II collagen receptor crucial for proper cartilage development. This work represents the first comparison of detailed immunophenotypic analysis and chondrogenic differentiation potential of human BM-, WJ-, DP-, and AT-MSCs performed under the same serum-free conditions, from their isolation to their induction. Our study, achieved in conditions compliant with clinical applications, highlights that BM-MSCs are good candidates for cartilage engineering.

We investigated for the first time the correlation between the maturation of biomechanical properties of the skin and the evolution of skin topography and micromorphology from infancy to early adulthood. 70 subjects in 7 age groups: 1-15 days, 5 weeks, 5-7 months, 2 years, 4-5 years, 7-8 years, and 20-35 years were included. Skin properties were examined by cutometry and reflectance confocal microscopy (RCM) in vivo, and by immunohistochemistry (IHC) in a limited number of foreskin biopsy samples. Cutometry showed that skin elasticity increased from infancy to 2 years. The viscoelastic component decreased from infancy to adulthood. Total recovery was slightly higher at older ages and total deformation did not vary between age groups. None of the parameters were correlated with stratum corneum (SC) hydration. RCM showed that thickness of the SC and supra papillary epidermis increased with age. The homogeneity and furrow architecture of SC changed dramatically between infants and older children. Dermal papillae increased in number with age, whereas rete ridge thickness remained stable. Circular cuffing of the follicle by collagen fibers was observed only in newborns, age at which collagen fibers were fibrillar and showed a parallel orientation. IHC showed that both fibrillin and elastin fibers increased in length and intensity with age, especially at the dermal-epidermal junction. These data demonstrate the biochemical and structural evolution of the dermis during postnatal development. These changes in these skin biomechanical properties are related to structural maturation rather than hydration. Our data support a contribution of mechanical forces to dermal maturation postnatally.

OBJECTIVES:Sebaceous glands maintain skin homeostasis by producing sebum. Low production can induce hair loss and fragile skin. Overproduction provokes seborrhoea and may lead to acne and inflammatory events. To better study sebaceous gland maintenance, sebocyte maturation, lipid production and ageing or inflammatory processes, we developed innovative 3D ex vivo models for human sebaceous glands.MATERIALS AND METHODS:Culture conditions and analytical methods optimized on sebocyte monolayers were validated on extracted sebaceous glands and allowed the development of two 3D models: (a) "air-liquid" interface and (b) human fibronectin-coated "sandwich" method. Lipid production was assessed with microscopy, fluorometry or flow cytometry analysis after Nile Red staining. Specific lipids (particularly squalene and peroxidized squalene) were measured by Gas or liquid Chromatography and Mass spectrometry.RESULTS:This study allowed us to select appropriate conditions and design Seb4Gln culture medium inducing sebocyte proliferation and neutral lipid production. The "air-liquid" model was appropriate to induce sebocyte isolation. The "sandwich" model enabled sebaceous gland maintenance up to 42 days. A treatment with Insulin Growth Factor-1 allowed validation of the model as we succeeded in mimicking dynamic lipid overproduction.CONCLUSION:Functional sebocyte maturation and physiological maintenance were preserved up to 6 weeks in our models. Associated with functional assays, they provide a powerful platform to mimic physiological skin lipid metabolism and to screen for active ingredients modulating sebum production.

Transplantation of mesenchymal stem/stromalcells (MSCs) has emerged as an effectivemethod to treat diseased or damagedorgans and tissues, and hundreds of clinicaltrials using MSCs are currently under way todemonstrate the validity of such a therapeuticapproach. However, most MSCs used for clinicaltrials are prepared in research laboratorieswith insufficient manufacturing quality control.In particular, laboratories lack standardizedprocedures for in vitro isolation of MSCs fromtissue samples, resulting in heterogeneouspopulations of cells and variable experimentaland clinical results.MSCs are now referred to as Human CellularTissue-based Products or Advanced TherapyMedicinal Products, and guidelines fromthe American Code of Federal Regulation ofthe Food and Drug Administration (21 CFRPart 1271) and from the European MedicinesAgency (European Directive 1394/2007) definerequirements for appropriate production ofthese cells. These guidelines, commonly called"Good Manufacturing Practices" (GMP),include recommendations about laboratorycell culture procedures to ensure optimal reproducibility,efficacy and safety of the finalmedicinal product. In particular, the Food andDrug Administration divides ex vivo culturedcells into "minimally" and "more than minimally"manipulated samples, in function of theuse or not of procedures "that might alter thebiological features of the cells". Today, minimalmanipulation conditions have not beendefined for the collection and isolation ofMSCs (Torre et al. 2015)(Ducret et al. 2015).Most if not all culture protocols that have beenreported so far are unsatisfactory, becauseof the use of xeno- or allogeneic cell culturemedia, enzymatic treatment and long-termcell amplification that are known to alter thequality of MSCs.The aim of this study was to describe a standardizedprocedure for recovering MSCs withminimal handling from two promising sources,the dental pulp (DP) and the Wharton's jelly(WJ) of the umbilical cord. The quality and homogeneityof the expanded cell populationswere assessed by using flow cytometry withcriteria that go beyond the International Societyof Cellular Therapy (ISCT) guidelines forMSC characterization.

Mesenchymal stromal/stem cells (MSCs) from human dental pulp (DP) can be expanded in vitro for cell-based and regenerative dentistry therapeutic purposes. However, their heterogeneity may be a hurdle to the achievement of reproducible and predictable therapeutic outcomes. To get a better knowledge about this heterogeneity, we designed a flow cytometric strategy to analyze the phenotype of DP cells in vivo and upon in vitro expansion with stem cell markers. We focused on the CD31- cell population to exclude endothelial and leukocytic cells. Results showed that the in vivo CD31- DP cell population contained 1.4% of CD56+, 1.5% of CD146+, 2.4% of CD271+ and 6.3% of MSCA-1+ cells but very few Stro-1+ cells (≤ 1%). CD56+, CD146+, CD271+, and MSCA-1+ cell subpopulations expressed various levels of these markers. CD146+MSCA-1+, CD271+MSCA-1+, and CD146+CD271+ cells were the most abundant DP-MSC populations. Analysis of DP-MSCs expanded in vitro with a medicinal manufacturing approach showed that CD146 was expressed by about 50% of CD56+, CD271+, MSCA-1+, and Stro-1+ cells, and MSCA-1 by 15-30% of CD56+, CD146+, CD271+, and Stro-1+ cells. These ratios remained stable with passages. CD271 and Stro-1 were expressed by <1% of the expanded cell populations. Interestingly, the percentage of CD56+ cells strongly increased from P1 (25%) to P4 (80%) both in all sub-populations studied. CD146+CD56+, MSCA-1+CD56+, and CD146+MSCA-1+ cells were the most abundant DP-MSCs at the end of P4. These results established that DP-MSCs constitute a heterogeneous mixture of cells in pulp tissue in vivo and in culture, and that their phenotype is modified upon in vitro expansion. Further studies are needed to determine whether co-expression of specific MSC markers confers DP cells specific properties that could be used for the regeneration of human tissues, including the dental pulp, with standardized cell-based medicinal products.