Pancreatic ductal adenocarcinoma: tumor microenvironment and problems in the development of novel therapeutic strategies.

Diagnosis and treatment of carcinoma of the exocrine part of the pancreas is a serious problem for modern medicine. Despite the identification of a large number of aberrant mutations in pancreatic ductal adenocarcinoma (PDAC), attempts to create effective therapeutic agents based on identified genetic or epigenetic variations have not been succesful. The role of the tumor microenvironment (TME) in tumor progression is currently a popular topic. Cancer-associated fibroblasts (CAFs) and extracellular matrix (ECM) are the main components of the tumor stroma and play an important role in the proliferation, invasiveness and metastasis of cancer. However, the mechanisms underlying the effect of CAFs and ECM on cancer progression are still unclear. Recent studies on stromal components and blockage of signaling pathways have brought some optimism to this area. New information on the role of TME will lead to the development of targeted therapies or combinations with modern chemotherapy for PDAC.

Local Delivery of Pirfenidone by PLA Implants Modifies Foreign Body Reaction and Prevents Fibrosis.

Peri-implant fibrosis (PIF) increases the postsurgical risks after implantation and limits the efficacy of the implantable drug delivery systems (IDDS). Pirfenidone (PF) is an oral anti-fibrotic drug with a short (<3 h) circulation half-life and strong adverse side effects. In the current study, disk-shaped IDDS prototype combining polylactic acid (PLA) and PF, PLA@PF, with prolonged (~3 days) PF release (in vitro) was prepared. The effects of the PLA@PF implants on PIF were examined in the rabbit ear skin pocket model on postoperative days (POD) 30 and 60. Matching blank PLA implants (PLA0) and PLA0 with an equivalent single-dose PF injection performed on POD0 (PLA0+injPF) served as control. On POD30, the intergroup differences were observed in α-SMA, iNOS and arginase-1 expressions in PLA@PF and PLA0+injPF groups vs. PLA0. On POD60, PIF was significantly reduced in PLA@PF group. The peri-implant tissue thickness decreased (532 ± 98 µm vs. >1100 µm in control groups) approaching the intact derma thickness value (302 ± 15 µm). In PLA@PF group, the implant biodegradation developed faster, while arginase-1 expression was suppressed in comparison with other groups. This study proves the feasibility of the local control of fibrotic response on implants via modulation of foreign body reaction with slowly biodegradable PF-loaded IDDS.

Co-growth of Stem Cells With Target Tissue Culture as an Easy and Effective Method of Directed Differentiation.

The long-term co-culture of mouse embryonic stem cells (mESC) with rat endothelial cells (EC) was tested for contact differentiation into the endothelial lineage. Serial passaging of rat ECs mixed with mESC in ratio 10:1 resulted in the emergence of a homogeneous cell population expressing mouse endothelial surface markers CD102, CD29, CD31. Rat endothelial surface marker RECA-1 completely disappeared from the co-cultured population after 2 months of weekly passaging. Co-incubation of mESC with rat ECs without cell-to-cell contact did not result in the conversion of mESC into ECs. After co-cultivation of adult mesenchymal stem cells from human endometrium (eMSC) with pre-hepatocyte-like cells of human hepatocarcinoma Huh7 the resulting co-culture expressed mature liver markers (oval cell antigen and cytokeratin 7), none of which were expressed by any of co-cultivated cultures, thus proving that even an immature (proliferating) pre-hepatocyte-like line can induce hepatic differentiation of stem cells. In conclusion, we have developed conditions where long-term co-proliferation of embryonic or adult SC with fully or partially differentiated cells results in stem cell progeny expressing markers of target tissue. In the case of endothelial differentiation, the template population quickly disappeared from the resulted culture and the pure endothelial population of stem cell progeny emerged. This approach demonstrates the expected fate of stem cells during various in vivo SC-therapies and also might be used as an effective in vitro differentiation method to develop the pure endothelium and, potentially, other tissue types of desirable genetic background.

Modeling of Old Scars: Histopathological, Biochemical and Thermal Analysis of the Scar Tissue Maturation.

Mature hypertrophic scars (HSs) remain a challenging clinical problem, particularly due to the absence of biologically relevant experimental models as a standard rabbit ear HS model only reflects an early stage of scarring. The current study aims to adapt this animal model for simulation of mature HS by validating the time of the scar stabilization using qualitative and quantitative criteria. The full-thickness skin and perichondrium excision wounds were created on the ventral side of the rabbit ears. The tissue samples were studied on post-operation days (PODs) 30, 60, 90 and 120. The histopathological examination and morphometry were applied in parallel with biochemical analysis of protein and glycosaminoglycans (GAGs) content and amino acid composition. The supramolecular organization of collagen was explored by differential scanning calorimetry. Four stages of the rabbit ear HS maturation were delineated and attributed with the histolomorphometrical and physicochemical parameters of the tissue. The experimental scars formed in 30 days but stabilized structurally and biochemically only on POD 90-120. This evidence-based model can be used for the studies and testing of new treatments of the mature HSs.

Extension of Maximal Lifespan and High Bone Marrow Chimerism After Nonmyeloablative Syngeneic Transplantation of Bone Marrow From Young to Old Mice.

The goal of this work was to determine the effect of nonablative syngeneic transplantation of young bone marrow (BM) to laboratory animals (mice) of advanced age upon maximum duration of their lifespan. To do this, transplantation of 100 million nucleated cells from BM of young syngeneic donors to an old nonablated animal was performed at the time when half of the population had already died. As a result, the maximum lifespan (MLS) increased by 28 ± 5%, and the survival time from the beginning of the experiment increased 2.8 ± 0.3-fold. The chimerism of the BM 6 months after the transplantation was 28%.