Refine
Document Type
- Doctoral Thesis (3)
Language
- English (3) (remove)
Has Fulltext
- yes (3)
Is part of the Bibliography
- no (3)
Keywords
- Collagen-based biomaterial (1)
- Macrophages (1)
- Platelet-rich fibrin (1)
- Regeneration (1)
- Wound healing (1)
Institute
- Medizin (2)
- Biowissenschaften (1)
Mesenchymal stem cells (MSC), also referred to as marrow stromal cells, maintain the capacity to differentiate into multiple mesenchymal lineages such as osteoblasts, chondrocytes, adipocytes, myoblasts, stromal, neural and endothelial cells. The use of autologous MSC has generated widespread interest due to their developing application in regenerative medicine and tissue engineering in orthopedic surgery. They have become an indispensable cell source for successful implementation in many bone reconstruction procedures. In addition to their multipotency and selfrenewal capacity, they are easily harvested, have demonstrated a homing mechanism and can be efficiently expanded in vitro, thus providing a safe and costefficient tissue replacement for patients with skeletal injury or disease. Little information is currently available concerning donor characteristics for tissue engineering growth of osseous tissue. This study examines the influences of such donor characteristics, including injury pattern, gender, age, and site of harvest on the quantity, quality and osteogenic differentiation of MSC. The goal is to evaluate whether certain patient groups are practically suitable for an ex vivo expansion and therapeutic reimplantation of MSC. The effect of injury pattern on the reservoir and proliferative capacity of MSC in human bone marrow is clearly demonstrated in this analysis. Age and gender were also shown to influence MSC number and proliferation, as in previous studies. A total of 53 participants (46 patients and 7 healthy volunteers ranging from 18 to 64 years of age), who were scheduled to undergo operative procedures on the pelvis, vertebrae, tibia or hip as well as cancellous bone autografts for reconstruction of various bone defects, were included in the study. Participants were divided into 4 groups for each gender: single fracture, multiple trauma, atrophic nonunion and healthy volunteers. A minimum of 6 ml bone marrow samples were aspirated intraoperatively and processed immediately according to protocol. Following cultivation and expansion for 14 days, the cells were then stained for the colony forming unit-fibroblast (CFU-F) assay and each culture flask was photographed, digitized and converted to an 8 bit grey level TIF-format. Using the digitized CFU-F assay, the mean colony number, mean colony area and mean cell number per microscopic field of view (cell density) could be determined. In addition, confirmation of MSC phenotype was established using fluorescent activated cell sorting (FACS). MSC potential for osteogenic differentiation was quantified by von Kossa, alkaline phosphatase and alizarin staining. Furthermore, serum from a total of 39 randomly chosen participants was collected and tested for hormone levels of 17β-estradiol, testosterone and prolactin as well as the cytokine interleukin-6. These analyses demonstrate several significant trauma-related modifications in MSC reservoir and proliferation, in both male and female patients. In multiple trauma patients, the highest MSC frequency was found, independent of gender and age. Proliferative capacity was also highest in male multiple trauma patients. In the case of atrophic nonunion, the lowest MSC reservoir was detected, independent of gender. Furthermore, MSC frequency in male patients was significantly higher than in female, although analyses of hormone and interleukin-6 levels provided no correlation. Agerelated changes in MSC reservoir could also be observed, whereas the proliferative capacity produced only a tendency toward decreasing values with increasing age. Concerning the site of cell harvest, MSC isolated from the proximal extremity of the tibia, greater trochanter and vertebral body did not proliferate sufficiently enough to be included in statistical analysis, supporting the use of the iliac crest for efficient expansion of MSC. This data suggests the interaction of yet to be identified processes in bone marrow in multiple trauma situations which stimulate the activation and mobilization of MSC. Moreover, in the case of atrophic nonunion, the concentration in bone marrow is depleted and the absence of systemic stimulation present in multiple trauma results in reduced activation of proliferative capacity. Such patients, with severe injury or atrophic nonunion, represent a group of patients with an especially acute necessity for effective and successful bone reconstruction. This data can be used to determine the applicability of MSC from various patient groups for osseous tissue replacement procedures. Especially in such medically challenging situations, further research is essential not only to delineate the factors involved in MSC regulation but also to develop methods to stimulate MSC expansion and proliferation.
Therapy of hemorrhagic shock with following resuscitation-induced liver injury : in vivo study
(2010)
Shock resulting from life-threatening blood-loss (hemorrhagic shock) represents the most frequent injury pattern after a traumatic insult. Hemorrhagic shock induces inflammatory changes, characterized by highly complex pathophysiological pathways often resulting in death. In this study, we establish an experimental in vivo model of H/R in rats and study the mechanisms which determine the hepatic injury after H/R. Furthermore, we show that hemorrhagic shock with following resuscitation is accompanied with release of systemic and local pro-inflammatory mediators, increased infiltration of hepatic neutrophils in the liver, increased oxidative and nitrosative stress, enhanced cell death of both types, apoptosis and necrosis, conspicuous cytoskeletal rearrangements, loss of hepatic integrity and finally high general mortality rates, up to 80%. In addition, the effects of two potential therapeutic interventions to prevent the H/R induced liver injury are explored in a model of H/R in rats. First, the role of JNK and its inhibition by D-JNKI-1 in preservation of hepatic integrity following H/R was analyzed. Second, we investigated the potential of simvastatin to prevent the disturbed inflammatory response and hepatic injury after H/R. The effects of both therapeutic interventions were studied by looking at several inflammatory parameters, markers of oxidative and nitrosative stress, cytoskeleton integrity, microcirculatory parameters, underlying signaling cascades, liver damage and mortality. Highly specific blockade of JNK with the potent, inhibitory peptide D-JNKI-1 revealed the crucial role of the JNK signaling pathway in the H/R induced pathophysiology and strong protective effects of DJNKI- 1 in H/R induced liver injury, when the peptide was applied before and even after hemorrhagic shock. The other therapeutic intervention tested in this study was the use of simvastatin which also revealed protective effects after H/R and even a remarkable improvement in survival after H/R. We show that H/R induced release of pro-inflammatory cytokines, hepatic PMNL infiltration, increased oxidative and nitrosative stress, apoptosis and necrosis can be diminished by treatment with D-JNKI-1 but also with simvastatin in vivo. Furthermore, simvastatin reduces H/R induced cytoskelatal rearrangements, loss of liver integrity and the mortality rate after H/R. The key pathway which underlies these beneficial effects of simvastatin is the Rho kinase pathway. Identification of both mechanisms as well as the effectiveness of both substances provide new insights in the close interaction between hypoxia and the immune system and present a promising basis for the anti-inflammatory, hepatoprotective treatment after H/R.
Current research on medical biomaterials have shown that the physical and chemical characteristics of biomaterials determine the body inflammatory cellular reaction after their implantation. The aim of this study was to evaluate the individual effects of the physical characteristics over the initial biomaterial-cellular interaction and the inflammatory cellular reaction. For this purpose, an equine-derived collagen hemostatic sponge (E-CHS) was modified by pressing and evaluated using ex vivo, in vitro and in vivo methods.
The E-CHS was pressed by applying constant pressure (6.47± 0.85 N) for 2 min using a sterile stainless-steel cylinder and cut in segments of 1cm2. Subsequently, E-CHS and the pressed equine-derived collagen hemostatic sponge (P-E-CHS) were studied as two independent biomaterials and compared to a control group (CG).
A blood concentrate containing inflammatory cells known as platelet rich fibrin (PRF) was used to mimic the initial biomaterial-cell interaction and to measure the absorption coefficient of the biomaterials to liquid PRF (iPAC). Additionally, the biomaterials were cultivated together with PRF for 3 and 6 days to measure the induction of pro-inflammatory cytokines (TNF-α and IL-8). The results were obtained through enzyme-linked immunosorbent assay (ELISA) and histological methods. PRF cultivated without biomaterials served as the CG. Additionally, the biomaterials were evaluated in vivo using a subcutaneous model in Wistar rats and compared to sham operated animals (CG) representing physiologic wound healing. After 3, 15 and 30 days, the explanted samples were evaluated using histochemical and immunohistochemical (IHC) staining using the following markers: CD68 (pan macrophages), CCR7 (pro-inflammatory macrophages, M1), CD206 (pro-wound healing macrophages, M2) and α-Smooth Muscle Actin (α-SMA; vessel identification).
After the mixture of liquid PRF with both biomaterials for 15 minutes, the ex vivo results showed that E-CHS was penetrated by cells, whereas P-E-CHS was cell-occlusive. Additionally, P-E-CHS induced a higher release of pro-inflammatory cytokines compared to liquid PRF alone (CG) and E-CHS after 3 days (P< 0.05). Although the biomaterial was pressed, the difference of the iPAC value did not show statistical differences. In vivo, the CG induced at day 3 a higher inflammatory response compared to the experimental groups (EG) (P< 0.05). The intergroup comparison showed that P-E-CHS induced a higher presence of macrophages (CD68+/CC7+) compared to E-CHS at day 3 (P< 0.05). Only CD68+/CCR7+ mononuclear cells (MNCs) were observed without multinucleated giant cells (MNGCs). After 15 days, the presence of macrophages (CD68+ P<0.01 /CCR7+ P<0.001 /CD206+ P<0.05) reduced considerably in the CG. On the contrary, the inflammatory response increased in the EGs (CD68+/CCR7+). The intergroup comparison showed that this increment was statistically significant when comparing E-CHS and P-E-CHS to the CG at day 15 (P<0.01 and P< 0.05 respectively). At this time point, a reduced number of MNGCs were observed in the EGs. In the CG no MNGCs were observed. Furthermore, E-CHS showed a faster degradation rate and was fully invaded by cells and vessels formed in its interior region. On the other hand, P-E-CHS remained occlusive to cell penetration and vessels were formed only in the periphery. After 30 days, the cellular reaction shifted to a higher number of M2 macrophages (CD260+) in all groups and a reduced presence of CD68+ and CCR7+ MNCs. Both biomaterials degraded and only small fragments were found in the implantation bed surrounded by MNGCs (CCR7+).
These results are of high clinical relevance and show that changes in biomaterial properties have a significant impact on their interaction with the body. They also serve as insight into the possibility to develop versatile biomaterials with different applications. For example, E-CHs can be applied to support hemostasis in a bleeding alveolar socket and P-E-CHs by being cell occlusive and having a delayed degradation rate can be applied for guided bone and tissue regeneration.