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Fetal Immunomodulatory Environment Following Cartilage Injury-The Key to CARTILAGE Regeneration?

ABSTRACT: Fetal cartilage fully regenerates following injury, while in adult mammals cartilage injury leads to osteoarthritis (OA). Thus, in this study, we compared the in vivo injury response of fetal and adult ovine articular cartilage histologically and proteomically to identify key factors of fetal regeneration. In addition, we compared the secretome of fetal ovine mesenchymal stem cells (MSCs) in vitro with injured fetal cartilage to identify potential MSC-derived therapeutic factors. Cartilage injury caused massive cellular changes in the synovial membrane, with macrophages dominating the fetal, and neutrophils the adult, synovial cellular infiltrate. Correspondingly, proteomics revealed differential regulation of pro- and anti-inflammatory mediators and growth-factors between adult and fetal joints. Neutrophil-related proteins and acute phase proteins were the two major upregulated protein groups in adult compared to fetal cartilage following injury. In contrast, several immunomodulating proteins and growth factors were expressed significantly higher in the fetus than the adult. Comparison of the in vitro MSCs proteome with the in vivo fetal regenerative signature revealed shared upregulation of 17 proteins, suggesting their therapeutic potential. Biomimicry of the fetal paracrine signature to reprogram macrophages and modulate inflammation could be an important future research direction for developing novel therapeutics.

SUBMITTER: Ribitsch I

PROVIDER: S-EPMC8657887 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Fetal cartilage fully regenerates following injury while in adult mammals cartilage injury leads to osteoarthritis (OA). OA is characterized by cartilage breakdown and joint inflammation and associated with significant pain and socioeconomic costs. As no clinically satisfactory treatment is available to date, disease-modifying therapies aimed to achieve cartilage regeneration are urgently required. The inherent regeneration potential of fetal individuals may hold answers to this unmet need. Therefore, to characterize the differences in fetal and adult response to cartilage injury, we carried out histology and comprehensive proteome analyses on fetal (day 80/150-day gestation) and adult cartilage samples one (fetal samples) and three (adult and fetal samples) days after surgical induction of a full-thickness cartilage lesion. In addition, proteins secreted by inflamed fetal MSCs in vitro were compared with the in vivo response to injury to evaluate their therapeutic potential. Histology of synovial samples revealed the presence of neutrophils one day post injury (p.i.) and an influx of macrophages into the subsynovial tissue on day 3 p.i. in fetal samples. In contrast, adult synovial samples showed invasion of neutrophils on day 3 p.i. Activation and migration of Iba1+- macrophages of the synovial lining was observed both in fetal and adult animals. Comparative mass spectrometry revealed 57 proteins significantly up-regulated (> 2FC, FDR<0.05), and 67 proteins significantly down-regulated (<-2 FC) upon injury in adults. Neutrophil-related proteins and acute phase proteins were the two major upregulated protein groups in adult cartilage following injury compared to fetal sheep. In contrast, several immunomodulating proteins and growth factors were significantly higher expressed in the fetus than the adult. Comparison of the in vitro MSCs with the in vivo fetal proteome revealed shared upregulation of 17 proteins, which were considered to be of potential therapeutic interest. The results of this study support our molecular understanding of successful fetal cartilage healing and new therapeutic strategies to induce regeneration in adult articular cartilage by modulating the inflammatory environment. The shared protein upregulation in fetal cartilage in vivo and in fetal MSCS during in vitro inflammation supports the possible therapeutic potential of these factors in specific and fetal MSCs in general.

Project description:Directing the organization of cells into a tissue with defined architectures is one use of biomaterials for regenerative medicine. To this end, hydrogels are widely investigated as they have mechanical properties similar to native soft tissues and can be formed in situ to conform to a defect. Herein, we describe the development of porous hydrogel tubes fabricated through a two-step polymerization process with an intermediate microsphere phase that provides macroscale porosity (66.5%) for cell infiltration. These tubes were investigated in a spinal cord injury model, with the tubes assembled to conform to the injury and to provide an orientation that guides axons through the injury. Implanted tubes had good apposition and were integrated with the host tissue due to cell infiltration, with a transient increase in immune cell infiltration at 1?week that resolved by 2?weeks post injury compared to a gelfoam control. The glial scar was significantly reduced relative to control, which enabled robust axon growth along the inner and outer surface of the tubes. Axon density within the hydrogel tubes (1744 axons/mm2) was significantly increased more than 3-fold compared to the control (456 axons/mm2), with approximately 30% of axons within the tube myelinated. Furthermore, implantation of hydrogel tubes enhanced functional recovery relative to control. This modular assembly of porous tubes to fill a defect and directionally orient tissue growth could be extended beyond spinal cord injury to other tissues, such as vascular or musculoskeletal tissue. STATEMENT OF SIGNIFICANCE: Tissue engineering approaches that mimic the native architecture of healthy tissue are needed following injury. Traditionally, pre-molded scaffolds have been implemented but require a priori knowledge of wound geometries. Conversely, hydrogels can conform to any injury, but do not guide bi-directional regeneration. In this work, we investigate the feasibility of a system of modular hydrogel tubes to promote bi-directional regeneration after spinal cord injury. This system allows for tubes to be cut to size during surgery and implanted one-by-one to fill any injury, while providing bi-directional guidance. Moreover, this system of tubes can be broadly applied to tissue engineering approaches that require a modular guidance system, such as repair to vascular or musculoskeletal tissues.

Project description:Normal tissue architecture is disrupted following injury, as resident tissue cells become damaged and immune cells are recruited to the site of injury. While injury and inflammation are critical to tissue remodeling, the inability to resolve this response can lead to the destructive complications of chronic inflammation. In the pancreas, acinar cells of the exocrine compartment respond to injury by transiently adopting characteristics of progenitor cells present during embryonic development. This process of de-differentiation creates a window where a mature and stable cell gains flexibility and is potentially permissive to changes in cellular fate. How de-differentiation can turn an acinar cell into another cell type (such as a pancreatic β-cell), or a cell with cancerous potential (as in cases of deregulated Kras activity) is of interest to both the regenerative medicine and cancer communities. While it is known that inflammation and acinar de-differentiation increase following pancreatic injury, it remains unclear which immune cells are involved in this process. We used a combination of genetically modified mice, immunological blockade and cellular characterization to identify the immune cells that impact pancreatic regeneration in an in vivo model of pancreatitis. We identified the innate inflammatory response of macrophages and neutrophils as regulators of pancreatic regeneration. Under normal conditions, mild innate inflammation prompts a transient de-differentiation of acinar cells that readily dissipates to allow normal regeneration. However, non-resolving inflammation developed when elevated pancreatic levels of neutrophils producing interferon-γ increased iNOS levels and the pro-inflammatory response of macrophages. Pancreatic injury improved following in vivo macrophage depletion, iNOS inhibition as well as suppression of iNOS levels in macrophages via interferon-γ blockade, supporting the impairment in regeneration and the development of chronic inflammation arises from aberrant activation of the innate inflammatory response. Collectively these studies identify targetable inflammatory factors that can be used to influence the development of non-resolving inflammation and pancreatic regeneration following injury.

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Fetal Immunomodulatory Environment Following Cartilage Injury-The Key to CARTILAGE Regeneration?

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