Long-Term Recruitment of Endogenous M2 Macrophages by Platelet Lysate-Rich Plasma Macroporous Hydrogel Scaffold for Articular Cartilage Defect Repair

Enhanced osteochondral repair by leukocyte-depleted platelet-rich plasma in combination with adipose-derived mesenchymal stromal cells encapsulated in a three-dimensional photocrosslinked injectable hydrogel in a rabbit model

INTRODUCTION

Intra-articular injection of adipose-derived mesenchymal stromal cells (ASCs) and/or platelet-rich plasma (PRP) have been reported to independently and synergistically improve healing of osteochondral lesions in animal models. However, their independent and combined effects when localized to an osteochondral lesion by encapsulation within a photocrosslinkable methacrylated gelatin hydrogel (GelMA) have not been explored. Herein we investigated a unique combination of allogeneic ASCs and PRP embedded in GelMA as a single-stage treatment for osteochondral regeneration in a rabbit model.

METHODS

Thirty mature rabbits were divided into six experimental groups: (1) Sham; (2) Defect; (3) GelMA; (4) GelMA + ASCs; (5) GelMA + PRP; and (6) GelMA + ASCs + PRP.At 12 weeks following surgical repair, osteochondral regeneration was assessed on the basis of gross appearance, biomechanical properties, histological and immunohistochemical characteristics, and subchondral bone volume.

RESULTS

In terms of mechanical property reflecting the ability of neotissue to bear stress, PRP only group were significantly lower than the Sham group (p = 0.0098). On the other hand, ASCs only and ASCs combined with PRP groups did not exhibit significantly difference, which suggesting that incorporation of ASCs assists in restoring the ability of the neotissue to bear stresses similarly to native tissue (p = 0.346, p = 0.40, respectively). Safranin O in ASCs combined with PRP group was significantly higher than the Defect and GelMA only groups (p = 0.0009, p = 0.0017, respectively). Additionally, ASCs only and ASCs combined with PRP groups presented especially strong staining for collagen type II. Surprisingly, PRP only and PRP + ASCs groups tended to exhibit higher collagen type I and collagen type X staining compared to ASCs only group, suggesting a potential PRP-mediated hypertrophic effect.

CONCLUSION

Regeneration of a focal osteochondral defect in a rabbit model was improved by a single-stage treatment of a photocrosslinked hydrogel containing allogenic ASCs and autologous PRP, with the combination of ASCs and PRP producing superior benefit than either alone. No experimental construct fully restored all properties of the native, healthy osteochondral unit, which may require longer follow-up or further modification of PRP and/or ASCs characteristics.

A cross-linked macropore hydrogel based on M1 macrophage lysate and alginate regulates tumor-associated macrophages for the treatment of melanoma

Pro-inflammatory M1 macrophages possess the ability to change the immunosuppressive tumor microenvironment by releasing various inflammatory factors simultaneously, which can effectively inhibit tumor progression and relapse. Promoting macrophage polarization towards M1 may be an effective way to treat Melanoma. However, the risk of cytokine storm caused by the proliferation and excessive activation of M1 macrophages greatly limits it as a biosafety therapeutic strategy in anti-tumor immunotherapy. Therefore, how to engineer natural M1 macrophage to a biocompatible biomaterial that maintains the duration time of tumor suppressive property duration time still remains a huge challenge. To achieve this goal, we developed an injectable macroporous hydrogel (M1LMHA) using natural M1 macrophage lysates and alginate as raw materials. M1LMHA had excellent biocompatibility, adjustable degradation rate and could sustainably release varieties of natural inflammatory factors, such as tumor necrosis factor-α (TNF-α), interferon-gamma (IFN-γ), and interleukin-12 (IL-12), etc. M1LMHA could repolarize anti-inflammatory M2 macrophages to M1 macrophages by the synergistic effect of released tiny inflammatory factors via the NF-κB pathway. This study supported that M1LMHA might be an effective and safe tool to activate tumor-associated immune cells, improving the efficiency of anti-tumor immunotherapy.

Human Adipose Tissue Lysate-Based Hydrogel for Lasting Immunomodulation to Effectively Improve Spinal Cord Injury Repair

The long-term inflammatory microenvironment is one of the main obstacles to inhibit acute spinal cord injury (SCI) repair. The natural adipose tissue-derived extracellular matrix hydrogel shows effective anti-inflammatory regulation because of its unique protein components. However, the rapid degradation rate and removal of functional proteins during the decellularization process impair the lasting anti-inflammation function of the adipose tissue-derived hydrogel. To address this problem, adipose tissue lysate provides an effective way for SCI repair due to its abundance of anti-inflammatory and nerve regeneration-related proteins. Thereby, human adipose tissue lysate-based hydrogel (HATLH) with an appropriate degradation rate is developed, which aims to in situ long-term recruit and induce anti-inflammatory M2 macrophages through sustainedly released proteins. HATLH can recruit and polarize M2 macrophages while inhibiting pro-inflammatory M1 macrophages regardless of human or mouse-originated. The axonal growth of neuronal cells also can be effectively improved by HATLH and HATLH-induced M2 macrophages. In vivo experiments reveal that HATLH promotes endogenous M2 macrophages infiltration in large numbers (3.5 × 105/100 µL hydrogel) and maintains a long duration for over a month. In a mouse SCI model, HATLH significantly inhibits local inflammatory response, improves neuron and oligodendrocyte differentiation, enhances axonal growth and remyelination, as well as accelerates neurological function restoration.

Biomimetic mineralization of platelet lysate/oxidized dextran cryogel as a macroporous 3D composite scaffold for bone repair

Scaffold development approaches using autologous sources for tissue repair are of great importance in obtaining bio-active/-compatible constructs. Platelet-rich plasma (PRP) containing various growth factors and platelet lysate (PL) derived from PRP are autologous products that have the potential to accelerate the tissue repair response by inducing a transient inflammatory event. Considering the regenerative capacity of PRP and PL, PRP/PL-based scaffolds are thought to hold great promise for tissue engineering as a natural source of autologous growth factors and a provider of mechanical support for cells. Here, a bio-mineralized PRP-based scaffold was developed using oxidized dextran (OD) and evaluated for future application in bone tissue engineering. Prepared PL/OD scaffolds were incubated in simulated body fluid (SBF) for 7, 14 and 21 d periods. Mineralized PL/OD scaffolds were characterized using Fourier transform infrared spectroscopy, x-ray diffraction spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis, porosity and compression tests. SEM and energy-dispersive x-ray spectroscopy analyses revealed mineral accumulation on the PL/OD scaffold as a result of SBF incubation.In vitrocytotoxicity andin vitrohemolysis tests revealed that the scaffolds were non-toxic and hemocompatible. Additionally, human osteoblasts (hOBs) exhibited good attachment and spreading behavior on the scaffolds and maintained their viability throughout the culture period. The alkaline phosphatase activity assay and calcium release results revealed that PL/OD scaffolds preserved the osteogenic properties of hOBs. Overall, findings suggest that mineralized PL/OD scaffold may be a promising scaffold for bone tissue engineering.

Assessing the advantages of 3D bioprinting and 3D spheroids in deciphering the osteoarthritis healing mechanism using human chondrocytes and polarized macrophages

The molecular niche of an osteoarthritic microenvironment comprises the native chondrocytes, the circulatory immune cells, and their respective inflammatory mediators. Although M2 macrophages infiltrate the joint tissue during osteoarthritis (OA) to initiate cartilage repair, the mechanistic crosstalk that dwells underneath is still unknown. Our study established a co-culture system of human OA chondrocytes and M2 macrophages in 3D spheroids and 3D bioprinted silk-gelatin constructs. It is already well established that Silk fibroin-gelatin bioink supports chondrogenic differentiation due to upregulation of the Wnt/β-catenin pathway. Additionally, the presence of anti-inflammatory M2 macrophages significantly upregulated the expression of chondrogenic biomarkers (COL-II, ACAN) with an attenuated expression of the chondrocyte hypertrophy (COL-X), chondrocyte dedifferentiation (COL-I) and matrix catabolism (MMP-1 and MMP-13) genes even in the absence of the interleukins. Furthermore, the 3D bioprinted co-culture model displayed an upper hand in stimulating cartilage regeneration and OA inhibition than the spheroid model, underlining the role of silk fibroin-gelatin in encouraging chondrogenesis. Additionally, the 3D bioprinted silk-gelatin constructs further supported the maintenance of stable anti-inflammatory phenotype of M2 macrophage. Thus, the direct interaction between the primary OAC and M2 macrophages in the 3D context, along with the release of the soluble anti-inflammatory factors by the M2 cells, significantly contributed to a better understanding of the molecular mechanisms responsible for immune cell-mediated OA healing.

Components and physical properties of hydrogels modulate inflammatory response and cartilage repair

Collagen and hyaluronic acid are commonly applied in cartilage tissue engineering, yet there has been limited investigation into their inflammatory response, a crucial factor in articular cartilage repair. This study aimed to evaluate the impact of components and physical properties of hydrogels on inflammatory response and cartilage repair. Three kinds of hydrogels with comparable storage moduli at low frequencies were designed and fabricated, namely, methacrylic anhydride-modified hyaluronic acid hydrogel (HAMA), methacrylic anhydride-modified type I collagen hydrogel (CMA) and unmodified type I collagen hydrogel (Col). HAMA hydrogel was unfavorable for adhesion and spreading of BMSCs. Furthermore, HAMA hydrogel stimulated rapid migration and pro-inflammatory M1 polarization of macrophages, leading to persistent and intense inflammation, which was unfavorable for cartilage repair. CMA and Col hydrogels possessed the same component and facilitated the adhesion, spreading and proliferation of BMSCs. Compared with CMA hydrogel, Col hydrogel induced rapid migration and moderate M1 polarization of macrophages at the early stage of injury, which was mainly influenced by its fast dissolution rate, small pore size fiber network structure and rapid stress relaxation. In addition, the phenotype of macrophages timely transformed into anti-inflammatory M2 due to the properties of the collagen component, which shortened the duration of inflammation and enhanced cartilage repair. The results indicated that moderate macrophage activation adjusted by hydrogel components and physical properties was critical in modulating inflammation and cartilage regeneration.

An Injectable and Antifouling Supramolecular Polymer Hydrogel with Microenvironment-Regulatory Function to Prevent Peritendinous Adhesion and Promote Tendon Repair

The imbalance of extrinsic and intrinsic healing of tendon is thought to be the main cause of peritendinous adhesions. In this work, an injectable supramolecular poly(N-(2-hydroxypropyl) acrylamide) (PHPAm) hydrogel is prepared merely via side chain hydrogen-bonding crosslinks. This PHPAm exhibits good antifouling and self-healing properties. The supramolecular hydrogel simultaneously loaded with Prussian blue (PB) nanoparticles and platelet lysate (PL) is explored as a functional physical barrier, which can significantly resist the adhesion of fibrin and fibroblasts, attenuate the local inflammatory response, and enhance the tenocytes activity, thus balancing extrinsic and intrinsic healing. The PHPAm hydrogel is shown to prevent peritendinous adhesions considerably by inhibiting NF-κB inflammatory pathway and TGF-β1/Smad3-mediated fibrosis pathway, thereby significantly improving tendon repair by releasing bioactive factors to regulate the tenocytes behavior. This work provides a new strategy for developing physical barriers to prevent peritendinous adhesions and promote tissue repair effectively.

An injectable bioactive dressing based on platelet-rich plasma and nanoclay: Sustained release of deferoxamine to accelerate chronic wound healing

Delayed diabetic wound healing has placed an enormous burden on society. The key factors limiting wound healing include unresolved inflammation and impaired angiogenesis. Platelet-rich plasma (PRP) gel, a popular biomaterial in the field of regeneration, has limited applications due to its non-injectable properties and rapid release and degradation of growth factors. Here, we prepared an injectable hydrogel (DPLG) based on PRP and laponite by a simple one-step mixing method. Taking advantages of the non-covalent interactions, DPLG could overcome the limitations of PRP gels, which is injectable to fill irregular injures and could serve as a local drug reservoir to achieve the sustained release of growth factors in PRP and deferoxamine (an angiogenesis promoter). DPLG has an excellent ability in accelerating wound healing by promoting macrophage polarization and angiogenesis in a full-thickness skin defect model in type I diabetic rats and normal rats. Taken together, this study may provide the ingenious and simple bioactive wound dressing with a superior ability to promote wound healing.

Engineered biochemical cues of regenerative biomaterials to enhance endogenous stem/progenitor cells (ESPCs)-mediated articular cartilage repair

As a highly specialized shock-absorbing connective tissue, articular cartilage (AC) has very limited self-repair capacity after traumatic injuries, posing a heavy socioeconomic burden. Common clinical therapies for small- to medium-size focal AC defects are well-developed endogenous repair and cell-based strategies, including microfracture, mosaicplasty, autologous chondrocyte implantation (ACI), and matrix-induced ACI (MACI). However, these treatments frequently result in mechanically inferior fibrocartilage, low cost-effectiveness, donor site morbidity, and short-term durability. It prompts an urgent need for innovative approaches to pattern a pro-regenerative microenvironment and yield hyaline-like cartilage with similar biomechanical and biochemical properties as healthy native AC. Acellular regenerative biomaterials can create a favorable local environment for AC repair without causing relevant regulatory and scientific concerns from cell-based treatments. A deeper understanding of the mechanism of endogenous cartilage healing is furthering the (bio)design and application of these scaffolds. Currently, the utilization of regenerative biomaterials to magnify the repairing effect of joint-resident endogenous stem/progenitor cells (ESPCs) presents an evolving improvement for cartilage repair. This review starts by briefly summarizing the current understanding of endogenous AC repair and the vital roles of ESPCs and chemoattractants for cartilage regeneration. Then several intrinsic hurdles for regenerative biomaterials-based AC repair are discussed. The recent advances in novel (bio)design and application regarding regenerative biomaterials with favorable biochemical cues to provide an instructive extracellular microenvironment and to guide the ESPCs (e.g. adhesion, migration, proliferation, differentiation, matrix production, and remodeling) for cartilage repair are summarized. Finally, this review outlines the future directions of engineering the next-generation regenerative biomaterials toward ultimate clinical translation.

Advances in the Treatment of Partial-Thickness Cartilage Defect

Partial-thickness cartilage defects (PTCDs) of the articular surface is the most common problem in cartilage degeneration, and also one of the main pathogenesis of osteoarthritis (OA). Due to the lack of a clear diagnosis, the symptoms are often more severe when full-thickness cartilage defect (FTCDs) is present. In contrast to FTCDs and osteochondral defects (OCDs), PTCDs does not injure the subchondral bone, there is no blood supply and bone marrow exudation, and the nearby microenvironment is unsuitable for stem cells adhesion, which completely loses the ability of self-repair. Some clinical studies have shown that partial-thickness cartilage defects is as harmful as full-thickness cartilage defects. Due to the poor effect of conservative treatment, the destructive surgical treatment is not suitable for the treatment of partial-thickness cartilage defects, and the current tissue engineering strategies are not effective, so it is urgent to develop novel strategies or treatment methods to repair PTCDs. In recent years, with the interdisciplinary development of bioscience, mechanics, material science and engineering, many discoveries have been made in the repair of PTCDs. This article reviews the current status and research progress in the treatment of PTCDs from the aspects of diagnosis and modeling of PTCDs, drug therapy, tissue transplantation repair technology and tissue engineering ("bottom-up").

Platelet Rich Plasma in the Repair of Articular Cartilage Injury: A Narrative Review

OBJECTIVE

This paper reviews the research of platelet-rich plasma (PRP) in articular cartilage injury repair, to assess the mechanism, utilization, and efficacy of PRP in the treatment of articular cartilage injury, hoping to provide a theoretical basis for the clinical application of PRP in the future.

MATERIALS AND METHODS

A comprehensive database search on PRP applications in cartilage repair was performed. Among them, the retrieval time range of PRP in clinical trials of repairing knee cartilage injury was from January 1, 2021 to January 1, 2022. Non-clinical trials and studies unrelated to cartilage injury were excluded.

RESULT

PRP can affect inflammation, angiogenesis, cartilage protection, and cellular proliferation and differentiation after articular cartilage injury through different pathways. In all, 13 clinical trials were included in the analysis.

CONCLUSION

PRP is an emergent therapeutic approach in tissue engineering. Most studies reported that PRP has a positive effect on cartilage injury, improving the joint function, meanwhile there is a lack of standardized standards. The technology of PRP in the repair and treatment of articular cartilage injury is worthy of further research.

Biomaterial-Based Therapeutic Approaches to Osteoarthritis and Cartilage Repair Through Macrophage Polarization

There is an ever-increasing clinical and socioeconomic burden associated with cartilage lesions & osteoarthritis (OA). Its progression, chondrocyte death & hypertrophy are all facilitated by inflamed synovium & joint environment. Due to their capacity to switch between pro- & anti-inflammatory phenotypes, macrophages are increasingly being recognized as a key player in the healing process, which has been largely overlooked in the past. A biomaterial's inertness has traditionally been a goal while developing them in order to reduce the likelihood of adverse reactions from the host organism. A better knowledge of how macrophages respond to implanted materials has made it feasible to determine the biomaterial architectural parameters that control the host response & aid in effective tissue integration. Thus, this review summarizes novel therapeutic techniques for avoiding OA or increasing cartilage repair & regeneration that might be developed using new technologies tuning macrophages into desirable functional phenotypes.