Quantitative Study of Tissue-Engineered Cartilage With Human Bone Marrow Mesenchymal Stem Cells

Influence of hepatocyte growth factor-transfected bone marrow-derived mesenchymal stem cells towards renal fibrosis in rats

Background & objectives:

Hepatocyte growth factor (HGF) produced by endothelial cells, fibroblasts, fat cells and other interstitial cells, can promote angiogenesis, repair damaged tissues and resist fibrosis. Mesenchymal stem cells (MSCs) are located in bone marrow and secrete a variety of cytokines and are often used in the repair and regeneration of damaged tissues. This study was aimed to investigate the influence of HGF-transfected bone marrow-derived MSCs towards renal fibrosis in rats.

Methods:

The HGF gene-carrying adenoviral vector (Ad-HGF) was transfected into MSCs, and the Ad-HGF-modified MSCs were transplanted into rats with unilateral ureteral obstruction (UUO). The localization of renal transplanted cells in the frozen section was observed with fluorescence microscope. The Masson's trichrome staining was performed to observe the renal collagen deposition, and the immunohistochemistry was performed to detect the expressions of α-smooth muscle actin (α-SMA) and HGF in renal tissues. Reverse transcription (RT)-PCR was used to detect the mRNA expressions of α-SMA, HGF and fibronectin (FN).

Results:

Ad-HGF-modified MSCs could highly express HGF in vitro. On the post-transplantation 3^rd, 7^th and 14^th day, the 4',6-diamidino-2-phenylindole (DAP)-labelled transplanted cells were seen inside renal tissues. Compared with UUO group, the renal collagen deposition in transplantation group was significantly reduced, and the expressions of α-SMA mRNA and protein were significantly decreased, while the expressions of HGF mRNA and protein were significantly increased, and the expression of FN mRNA was significantly decreased (P<0.001).

Interpretation & conclusions:

Trans-renal artery injection of HGF-modified MSCs can effectively reduce the renal interstitial fibrosis in UUO rat model.

Orthopedic tissue regeneration: cells, scaffolds, and small molecules

Orthopedic tissue regeneration would benefit the aging population or patients with degenerative bone and cartilage diseases, especially osteoporosis and osteoarthritis. Despite progress in surgical and pharmacological interventions, new regenerative approaches are needed to meet the challenge of creating bone and articular cartilage tissues that are not only structurally sound but also functional, primarily to maintain mechanical integrity in their high load-bearing environments. In this review, we discuss new advances made in exploiting the three classes of materials in bone and cartilage regenerative medicine--cells, biomaterial-based scaffolds, and small molecules--and their successes and challenges reported in the clinic. In particular, the focus will be on the development of tissue-engineered bone and cartilage ex vivo by combining stem cells with biomaterials, providing appropriate structural, compositional, and mechanical cues to restore damaged tissue function. In addition, using small molecules to locally promote regeneration will be discussed, with potential approaches that combine bone and cartilage targeted therapeutics for the orthopedic-related disease, especially osteoporosis and osteoarthritis.

Analyzing Structure and Function of Vascularization in Engineered Bone Tissue by Video-Rate Intravital Microscopy and 3D Image Processing

Vascularization is a key challenge in tissue engineering. Three-dimensional structure and microcirculation are two fundamental parameters for evaluating vascularization. Microscopic techniques with cellular level resolution, fast continuous observation, and robust 3D postimage processing are essential for evaluation, but have not been applied previously because of technical difficulties. In this study, we report novel video-rate confocal microscopy and 3D postimage processing techniques to accomplish this goal. In an immune-deficient mouse model, vascularized bone tissue was successfully engineered using human bone marrow mesenchymal stem cells (hMSCs) and human umbilical vein endothelial cells (HUVECs) in a poly (D,L-lactide-co-glycolide) (PLGA) scaffold. Video-rate (30 FPS) intravital confocal microscopy was applied in vitro and in vivo to visualize the vascular structure in the engineered bone and the microcirculation of the blood cells. Postimage processing was applied to perform 3D image reconstruction, by analyzing microvascular networks and calculating blood cell viscosity. The 3D volume reconstructed images show that the hMSCs served as pericytes stabilizing the microvascular network formed by HUVECs. Using orthogonal imaging reconstruction and transparency adjustment, both the vessel structure and blood cells within the vessel lumen were visualized. Network length, network intersections, and intersection densities were successfully computed using our custom-developed software. Viscosity analysis of the blood cells provided functional evaluation of the microcirculation. These results show that by 8 weeks, the blood vessels in peripheral areas function quite similarly to the host vessels. However, the viscosity drops about fourfold where it is only 0.8 mm away from the host. In summary, we developed novel techniques combining intravital microscopy and 3D image processing to analyze the vascularization in engineered bone. These techniques have broad applicability for evaluating vascularization in other engineered tissues as well.

Repair of ear cartilage defects with allogenic bone marrow mesenchymal stem cells in rabbits

The study aims to investigate the feasibility of repairing cartilaginous defects with chondrocytes induced from allogenic bone marrow mesenchymal stem cells (BMMSC) in rabbits' ear. BMMSCs were isolated and purified from New Zealand rabbits, in vitro amplified, and cultured in chondrocyte induction medium in order to acquire chondrocytes. After 3 weeks of induction, their phenotypes were confirmed as chondrocytes, then they were implanted onto novel polymeric scaffolds made from Poly (dl-lactide-co-glycolide) (PLGA) embedded with chitosan nonwoven cloth. The experimental group was transplanted with tissue engineering cartilaginous grafts composed of chondrogenetic BMMSC/scaffolds; the scaffold group was treated with scaffolds without cells, while in the control group, nothing was implanted. Specimens were taken at 6, 12, and 18 weeks after implantation, and the healing condition was observed by hematoxylin-eosin staining and toluidine blue staining. The right and left ears with cartilage defects of eighteen rabbits were randomly divided into three groups. In the experimental group, after 18 weeks of transplantation, the gross observation indicated that the cartilaginous defects were completely repaired by chondrocytes with smooth surface and similar color with the surrounding tissue. Hematoxylin-eosin staining and toluidine blue staining suggested that the defective area was filled with mature cartilage cells with obvious lacunae but without obvious boundaries with the normal cartilage tissue, and that the new cartilage cells were evenly distributed with homogeneously dyed cytoplasm and smaller in size. The chondrocyte induced from allogenic BMMSC can be used to repair cartilage defects in rabbit's ear.

Tissue-engineered cartilage: the crossroads of biomaterials, cells and stimulating factors

Damage to cartilage represents one of the most challenging tasks of musculoskeletal therapeutics due to its limited propensity for healing and regenerative capabilities. Lack of current treatments to restore cartilage tissue function has prompted research in this rapidly emerging field of tissue regeneration of functional cartilage tissue substitutes. The development of cartilaginous tissue largely depends on the combination of appropriate biomaterials, cell source, and stimulating factors. Over the years, various biomaterials have been utilized for cartilage repair, but outcomes are far from achieving native cartilage architecture and function. This highlights the need for exploration of suitable biomaterials and stimulating factors for cartilage regeneration. With these perspectives, we aim to present an overview of cartilage tissue engineering with recent progress, development, and major steps taken toward the generation of functional cartilage tissue. In this review, we have discussed the advances and problems in tissue engineering of cartilage with strong emphasis on the utilization of natural polymeric biomaterials, various cell sources, and stimulating factors such as biophysical stimuli, mechanical stimuli, dynamic culture, and growth factors used so far in cartilage regeneration. Finally, we have focused on clinical trials, recent innovations, and future prospects related to cartilage engineering.

Differentiation potential of multipotent progenitor cells derived from war-traumatized muscle tissue

BACKGROUND

Recent military conflicts have resulted in numerous extremity injuries requiring complex orthopaedic reconstructive procedures, which begin with a thorough débridement of all contaminated and necrotic tissue in the zone of injury. The site of injury is also the site of healing, and we propose that débrided muscle tissue contains cells with robust reparative and regenerative potential.

METHODS

Débrided muscle from soldiers who had sustained traumatic open extremity injuries was collected during surgical débridement procedures at Walter Reed Army Medical Center. With modifications to a previously described stem-cell-isolation protocol, mesenchymal progenitor cells were harvested from traumatized muscle, enriched, expanded in culture, and exposed to induction media for osteogenesis, adipogenesis, and chondrogenesis.

RESULTS

The isolated mesenchymal progenitor cells stained positive for cell-surface markers (CD73, CD90, CD105), which are characteristic of adult human mesenchymal stem cells. Histological identification of lineage-specific markers demonstrated the potential of these cells to differentiate into multiple mesenchymal lineages. Reverse transcription-polymerase chain reaction analysis confirmed multilineage mesenchymal differentiation at the gene-expression level.

CONCLUSIONS

To our knowledge, the present report provides the first description of mesenchymal progenitor cell isolation from traumatized human muscle. These cells may play an integral role in tissue repair and regeneration and merit additional investigation as they could be useful in future cell-based tissue-engineering strategies.

Engineering cartilage tissue

Cartilage tissue engineering is emerging as a technique for the regeneration of cartilage tissue damaged due to disease or trauma. Since cartilage lacks regenerative capabilities, it is essential to develop approaches that deliver the appropriate cells, biomaterials, and signaling factors to the defect site. The objective of this review is to discuss the approaches that have been taken in this area, with an emphasis on various cell sources, including chondrocytes, fibroblasts, and stem cells. Additionally, biomaterials and their interaction with cells and the importance of signaling factors on cellular behavior and cartilage formation will be addressed. Ultimately, the goal of investigators working on cartilage regeneration is to develop a system that promotes the production of cartilage tissue that mimics native tissue properties, accelerates restoration of tissue function, and is clinically translatable. Although this is an ambitious goal, significant progress and important advances have been made in recent years.

Immune response to stem cells and strategies to induce tolerance

Although recent progress in cardiovascular tissue engineering has generated great expectations for the exploitation of stem cells to restore cardiac form and function, the prospects of a common mass-produced cell resource for clinically viable engineered tissues and organs remain problematic. The refinement of stem cell culture protocols to increase induction of the cardiomyocyte phenotype and the assembly of transplantable vascularized tissue are areas of intense current research, but the problem of immune rejection of heterologous cell type poses perhaps the most significant hurdle to overcome. This article focuses on the potential advantages and problems encountered with various stem cell sources for reconstruction of the damaged or failing myocardium or heart valves and also discusses the need for integrating advances in developmental and stem cell biology, immunology and tissue engineering to achieve the full potential of cardiac tissue engineering. The ultimate goal is to produce 'off-the-shelf' cells and tissues capable of inducing specific immune tolerance.

Meniscal Repair With Fibrocartilage Engineering

Injuries to the knee meniscus, particularly those in the avascular region, pose a complex problem and a possible solution is tissue engineering of a replacement tissue. Tissue engineering of the meniscus involves scaffold selection, addition of cells, and stimulation of the construct to synthesize, maintain, or enhance matrix production. An acellular collagen implant is currently in clinical trials and there are promising results with other scaffolds, composed of both polymeric and natural materials. The addition of cells to these constructs may promote good matrix production in vitro, but has been studied in a limited manner in animal studies. Cell sources ranging from fibroblasts to stem cells could be used to overcome challenges in cell procurement, expansion, and synthetic capacity currently encountered in studies with fibrochondrocytes. Manipulation of construct culture with exogenous growth factors and mechanical stimulation will also likely play a role in these strategies.

Identification of cartilage progenitor cells in the adult ear perichondrium: utilization for cartilage reconstruction

For cartilage reconstruction, it is still difficult to obtain a sufficient volume of cartilage and to maintain its functional phenotype for a long period. Utilizing tissue stem cells is one approach to overcome such difficulties. We show here the presence of cartilage progenitor cells in the ear perichondrium of adult rabbits by 5-bromo-2'-deoxyuridine labeling, clonogenicity, and differentiation analyses. Long-term label-retaining cells were demonstrated in the perichondrium. Cells from the perichondrium, that is, perichondrocytes were mechanically isolated using a raspatory and maintained in D-MEM/F-12 medium with 10% FCS. They proliferated more vigorously than chondrocytes from the cartilage. Perichondrocytes could differentiate into adipocytes as well as osteocytes in differentiation induction medium. For cartilage reconstruction in vivo, perichondrocytes were seeded on collagen sponge scaffolds and implanted in nude mice. After 4 weeks, the composites with perichondrocytes generated the same weight of cartilaginous tissue as those with chondrocytes. They produced glycosaminoglycan and type II collagen as shown by RT-PCR and immunohistochemical examination. On the contrary, rabbit bone marrow mesenchymal stem cells used as control could regenerate significantly smaller cartilage than perichondrocytes in the implant study. Based on these findings, we propose that the perichondrium containing tissue progenitor cells is one of the potential candidates for use in reconstructing cartilage and new therapeutic modalities.