Deleterious effects of plasma-derived cellular debris in a porcine model of hemorrhagic shock

BACKGROUND

Recent studies identify large quantities of inflammatory cellular debris within Fresh Frozen Plasma (FFP). As FFP is a mainstay of hemorrhagic shock resuscitation, we used a porcine model of hemorrhagic shock and ischemia/reperfusion to investigate the inflammatory potential of plasma-derived cellular debris administered during resuscitation.

METHODS

The porcine model of hemorrhagic shock included laparotomy with 35 % hemorrhage (Hem), 45 min of ischemia from supraceliac aortic occlusion with subsequent clamp release (IR), followed by protocolized resuscitation for 6 h. Cellular debris (Debris) was added to the resuscitation phase in three groups. The four groups consisted of Hem + IR (n = 4), Hem + IR + Debris (n = 3), Hem + Debris (n = 3), and IR + Debris (n = 3). A battery of laboratory, physiologic, cytokine, and outcome data were compared between groups.

RESULTS

As expected, the Hem + IR group showed severe time dependent decrements in organ function and physiologic parameters. All animals that included both IR and Debris (Hem + IR + Debris or IR + Debris) died prior to the six-hour end point, while all animals in the Hem + IR and Hem + Debris survived. Cytokines measured at 30-60 min after initiation of resuscitation revealed significant differences in IL-18 and IL-1β between all groups.

CONCLUSIONS

Ischemia and reperfusion appear to prime the immune system to the deleterious effects of plasma-derived cellular debris. In the presence of ischemia and reperfusion, this model showed the equivalency of 100 % lethality when resuscitation included quantities of cellular debris at levels routinely administered to trauma patients during transfusion of FFP. A deeper understanding of the immunobiology of FFP-derived cellular debris is critical to optimize resuscitation for hemorrhagic shock.

Cryoablation for Chest Wall Trauma: A Brief Report

Respiratory failure secondary to rib fractures is a major source of morbidity and mortality in trauma patients, particularly in older populations. Management of pain in these patients is complex due to the nature of the injuries. We present 3 patients who underwent a video-assisted thoracoscopic cryoablation of intercostal nerves for pain control after chest trauma. None of the patients developed post-operative complications related to poor respiratory status such as pneumonia or atelectasis. At one-month clinic follow-up, all patients reported no chest pain and were not using opiate analgesics. In patients for whom there is a contraindication to rib fixation in the setting of unstable rib fractures, cryoablation may be a method by which to improve respiratory status and decrease ventilator dependency due to pain. Cryoablation of intercostal nerves may provide a more durable and clinically feasible solution to aid in the healing process of these patients.

The Relationship between Serum Sodium, Serum Osmolality, and Intracranial Pressure in Patients with Traumatic Brain Injury Treated with Hyperosmolar Therapy

BACKGROUND

Treatment of elevated intracranial pressure (ICP) in traumatic brain injury (TBI) is controversial. Hyperosmolar therapy is used to prevent cerebral edema in these patients. Many intensivists measure direct correlates of these agents-serum sodium and osmolality. We seek to provide context on the utility of using these measures to estimate ICP in TBI patients.

MATERIALS AND METHODS

Patients admitted with TBI who required ICP monitoring from 2008 to 2012 were included. Intracranial pressure, serum sodium, and serum osmolality were assessed prior to hyperosmotic therapy then at 6, 12, 18, 24, 48, and 72 hours after admission. A linear regression was performed on sodium, osmolality, and ICP at baseline and serum sodium and osmolality that corresponded with ICP for 6-72-hour time points.

RESULTS

136 patients were identified. Patients with initial measures were included in the baseline analysis (n = 29). Patients who underwent a craniectomy were excluded from the 6-72-hour analysis (n = 53). Initial ICP and serum sodium were not significantly correlated (R2 .00367, P = .696). Initial ICP and serum osmolality were not significantly correlated (R2 .00734, P = .665). Intracranial pressure and serum sodium 6-72 hours after presentation were poorly correlated (R2 .104, P < .0001), as were ICP and serum osmolality at 6-72 hours after presentation (R2 .116, P < .0001).

DISCUSSION

Our results indicate initial ICP is not correlated with serum sodium or osmolality suggesting these are not useful initial clinical markers for ICP estimation. The association between ICP and serum sodium and osmolality after hyperosmolar therapy was poor, thus may not be useful as surrogates for direct ICP measurements.

Priming as a strategy to overcome detrimental pH effects on cells for intervertebral disc regeneration

Disc disease is characterised by degeneration of the nucleus pulposus (NP), the central gelatinous tissue of the intervertebral disc (IVD). As degeneration progresses, the microenvironment of the IVD becomes more hostile (i.e. decrease in oxygen, glucose and pH), providing a significant challenge for regeneration using cell-based therapies. Tissue engineering strategies such as priming cells or micro tissues with growth factors prior to implantation may overcome some of these issues by providing a pre-formed protective niche composed of extracellular matrix. The present study investigated the effect of priming on bone-marrow-derived stem cells (BMSCs) and articular chondrocytes (ACs) using transforming growth factor β3 (TGF-β3), cultured at different pH levels (pH 7.1, 6.8 and 6.5) representative of the in vivo disc microenvironment. Low pH was found to have a detrimental effect on both cell viability and matrix accumulation, which could be mitigated by priming cells using TGF-β3. Investigating the activation of the transmembrane acid-sensing ion channels (ASIC-1 and -3) showed an increased expression of ASIC-1 in BMSCs and ASIC-3 in ACs at lower pH levels post-priming. Metabolic activity in terms of lactic acid production was also found to be affected significantly by priming, whereas oxygen and glucose consumptions did not change considerably. Overall, the study demonstrated that cells could be equipped to sustain the harsh environment of the IVD and promote accumulation of NP-like matrix through priming. Such an approach may open new avenues to engineer tissues capable of sustaining challenging microenvironments such as those found in the IVD.

In vitro co-culture and ex vivo organ culture assessment of primed and cryopreserved stromal cell microcapsules for intervertebral disc regeneration

Priming towards a discogenic phenotype and subsequent cryopreservation of microencapsulated bone marrow stromal cells (BMSCs) may offer an attractive therapeutic approach for disc repair. It potentially obviates the need for in vivo administration of exogenous growth factors, otherwise required to promote matrix synthesis, in addition to providing 'off-the-shelf' availability. Cryopreserved and primed BMSC microcapsules were evaluated in an in vitro surrogate co-culture model system with nucleus pulposus (NP) cells under intervertebral disc (IVD)-like culture conditions and in an ex vivo bovine organ culture disc model. BMSCs were microencapsulated in alginate microcapsules and primed for 14 d with transforming growth factor beta-3 (TGF-β3) under low oxygen conditions prior to cryopreservation. For the in vitro phase, BMSC microcapsules (unprimed or primed) were cultured for 28 d in a surrogate co-culture model system mimicking that of the IVD. For the ex vivo phase, microcapsules (unprimed or primed) were injected into the NP of bovine discs that underwent nucleotomy. In vitro results revealed that although NP cells produced significantly more matrix components in co-culture with BMSC microcapsules regardless of the differentiation state, unprimed microcapsules were inadequate at synthesising matrix as compared to primed microcapsules. However, this difference was diminished when evaluated in the ex vivo organ culture model,withboth unprimed and primed BMSC microcapsules accumulating large amounts of sulphated glycosaminoglycan (sGAG) and collagen and filling the defect cavity. Both models demonstrated that cryopreservation of BMSC microcapsules may offer a feasible strategy for predesigned delivery through cryobanking for on-demand regeneration of the IVD.

In vitro extracellular matrix accumulation of nasal and articular chondrocytes for intervertebral disc repair

Chondrocyte based regenerative therapies for intervertebral disc repair such as Autologous Disc Cell Transplantation (ADCT, CODON) and allogeneic juvenile chondrocyte implantation (NuQu^®, ISTO Technologies) have demonstrated good outcomes in clinical trials. However concerns remain with the supply demand reconciliation and issues surrounding immunoreactivity which exist for allogeneic-type technologies. The use of stem cells is challenging due to high growth factor requirements, regulatory barriers and differentiation towards a stable phenotype. Therefore, there is a need to identify alternative non-disc cell sources for the development and clinical translation of next generation therapies for IVD regeneration. In this study, we compared Nasal Chondrocytes (NC) as a non-disc alternative chondrocyte source with Articular Chondrocytes (AC) in terms of cell yield, morphology, proliferation kinetics and ability to produce key extracellular matrix components under 5% and 20% oxygen conditions, with and without exogenous TGF-β supplementation. Results indicated that NC maintained proliferative capacity with high amounts of sGAG and lower collagen accumulation in the absence of TGF-β supplementation under 5% oxygen conditions. Importantly, osteogenesis and calcification was inhibited for NC when cultured in IVD-like microenvironmental conditions. The present study provides a rationale for the exploration of nasal chondrocytes as a promising, potent and clinically feasible autologous cell source for putative IVD repair strategies.

Tissue engineering scaled-up, anatomically shaped osteochondral constructs for joint resurfacing

Arthroplasty is currently the only surgical procedure available to restore joint function following articular cartilage and bone degeneration associated with diseases such as osteoarthritis (OA). A potential alternative to this procedure would be to tissue-engineer a biological implant and use it to replace the entire diseased joint. The objective of this study was therefore to tissue-engineer a scaled-up, anatomically shaped, osteochondral construct suitable for partial or total resurfacing of a diseased joint. To this end it was first demonstrated that a bone marrow derived mesenchymal stem cell seeded alginate hydrogel could support endochondral bone formation in vivo within the osseous component of an osteochondral construct, and furthermore, that a phenotypically stable layer of articular cartilage could be engineered over this bony tissue using a co-culture of chondrocytes and mesenchymal stem cells. Co-culture was found to enhance the in vitro development of the chondral phase of the engineered graft and to dramatically reduce its mineralisation in vivo. In the final part of the study, tissue-engineered grafts (~ 2 cm diameter) mimicking the geometry of medial femorotibial joint prostheses were generated using laser scanning and rapid prototyped moulds. After 8 weeks in vivo, a layer of cartilage remained on the surface of these scaled-up engineered implants, with evidence of mineralisation and bone development in the underlying osseous region of the graft. These findings open up the possibility of a tissue-engineered treatment option for diseases such as OA.

Cyclic hydrostatic pressure promotes a stable cartilage phenotype and enhances the functional development of cartilaginous grafts engineered using multipotent stromal cells isolated from bone marrow and infrapatellar fat pad

The objective of this study was to investigate how joint specific biomechanical loading influences the functional development and phenotypic stability of cartilage grafts engineered in vitro using stem/progenitor cells isolated from different source tissues. Porcine bone marrow derived multipotent stromal cells (BMSCs) and infrapatellar fat pad derived multipotent stromal cells (FPSCs) were seeded in agarose hydrogels and cultured in chondrogenic medium, while simultaneously subjected to 10MPa of cyclic hydrostatic pressure (HP). To mimic the endochondral phenotype observed in vivo with cartilaginous tissues engineered using BMSCs, the culture media was additionally supplemented with hypertrophic factors, while the loss of phenotype observed in vivo with FPSCs was induced by withdrawing transforming growth factor (TGF)-β3 from the media. The application of HP was found to enhance the functional development of cartilaginous tissues engineered using both BMSCs and FPSCs. In addition, HP was found to suppress calcification of tissues engineered using BMSCs cultured in chondrogenic conditions and acted to maintain a chondrogenic phenotype in cartilaginous grafts engineered using FPSCs. The results of this study point to the importance of in vivo specific mechanical cues for determining the terminal phenotype of chondrogenically primed multipotent stromal cells. Furthermore, demonstrating that stem or progenitor cells will appropriately differentiate in response to such biophysical cues might also be considered as an additional functional assay for evaluating their therapeutic potential.

The use of the reamer-irrigator-aspirator to harvest mesenchymal stem cells

The scarcity of mesenchymal stem cells (MSCs) in iliac crest bone marrow aspirate (ICBMA), and the expense and time in culturing cells, has led to the search for alternative harvest sites. The reamer-irrigation-aspirator (RIA) provides continuous irrigation and suction during reaming of long bones. The aspirated contents pass via a filter, trapping bony fragments, before moving into a 'waste' bag from which MSCs have been previously isolated. We examined the liquid and solid phases, performed a novel digestion of the solid phase, and made a comparative assessment in terms of number, phenotype and differentiation capacity with matched ICBMA. The solid fraction from the filtrate was digested for 60 minutes at 37° C with collagenase. Enumeration was performed via the colony-forming unit fibroblast (CFU-F) assay. Passage (P2) cells were differentiated towards osteogenic, adipogenic and chondrogenic lineages, and their phenotypes assessed using flow cytometry (CD33, CD34, CD45, CD73, CD90, and CD105). MSCs from the RIA phases were able to differentiate at least as well as those from ICBMA, and all fractions had phenotypes consistent with other established sources. The median number of colonies for the three groups was: ICBMA = 8.5 (2 to 86), RIA-liquid = 19.5 (4 to 90), RIA-solid = 109 (67 to 200) per 200 μl. The mean total yield of cells for the three groups was: ICBMA = 920 (0 to 4275), RIA-liquid = 114,983 (16,500 to 477,750), RIA-solid = 12,785 (7210 to 28 475). The RIA filtrate contains large numbers of MSCs that could potentially be extracted without enzymatic digestion and used for bone repair without prior cell expansion.

Oxygen tension differentially regulates the functional properties of cartilaginous tissues engineered from infrapatellar fat pad derived MSCs and articular chondrocytes

BACKGROUND

For current tissue engineering or regenerative medicine strategies, chondrocyte (CC)- or mesenchymal stem cell (MSC)-seeded constructs are typically cultured in normoxic conditions (20% oxygen). However, within the knee joint capsule a lower oxygen tension exists.

OBJECTIVE

The objective of this study was to investigate how CCs and infrapatellar fad pad derived MSCs will respond to a low oxygen (5%) environment in 3D agarose culture. Our hypothesis was that culture in a low oxygen environment (5%) will enhance the functional properties of cartilaginous tissues engineered using both cell sources.

EXPERIMENTAL DESIGN

Cell-encapsulated agarose hydrogel constructs (seeded with CCs or infrapatellar fat pad (IFP) derived MSCs) were prepared and cultured in a chemically defined serum-free medium in the presence (CCs and MSCs) or absence (CCs only) of transforming growth factor-beta3 (TGF-β3) in normoxic (20%) or low oxygen (5%) conditions for 42 days. Constructs were assessed at days 0, 21 and 42 in terms of mechanical properties, biochemical content and histologically.

RESULTS

Low oxygen tension (5%) was observed to promote extracellular matrix (ECM) production by CCs cultured in the absence of TGF-β3, but was inhibitory in the presence of TGF-β3. In contrast, a low oxygen tension enhanced chondrogenesis of IFP constructs in the presence of TGF-β3, leading to superior mechanical functionality compared to CCs cultured in identical conditions.

CONCLUSIONS

Extrapolating the results of this study to the in vivo setting, it would appear that joint fat pad derived MSCs may possess a superior potential to generate a functional repair tissue in low oxygen tensions. However, in the context of in vitro cartilage tissue engineering, CCs maintained in normoxic conditions in the presence of TGF-β3 generate the most mechanically functional tissue.

Identification of mitogen-activated protein kinase docking sites in enzymes that metabolize phosphatidylinositols and inositol phosphates

BACKGROUND

Reversible interactions between the components of cellular signaling pathways allow for the formation and dissociation of multimolecular complexes with spatial and temporal resolution and, thus, are an important means of integrating multiple signals into a coordinated cellular response. Several mechanisms that underlie these interactions have been identified, including the recognition of specific docking sites, termed a D-domain and FXFP motif, on proteins that bind mitogen-activated protein kinases (MAPKs). We recently found that phosphatidylinositol-specific phospholipase C-gamma1 (PLC-gamma1) directly binds to extracellular signal-regulated kinase 2 (ERK2), a MAPK, via a D-domain-dependent mechanism. In addition, we identified D-domain sequences in several other PLC isozymes. In the present studies we sought to determine whether MAPK docking sequences could be recognized in other enzymes that metabolize phosphatidylinositols (PIs), as well as in enzymes that metabolize inositol phosphates (IPs).

RESULTS

We found that several, but not all, of these enzymes contain identifiable D-domain sequences. Further, we found a high degree of conservation of these sequences and their location in human and mouse proteins; notable exceptions were PI 3-kinase C2-gamma, PI 4-kinase type IIbeta, and inositol polyphosphate 1-phosphatase.

CONCLUSION

The results indicate that there may be extensive crosstalk between MAPK signaling and signaling pathways that are regulated by cellular levels of PIs or IPs.

Fear conditioning is associated with altered integration of PLC and ERK signaling in the hippocampus

The extracellular signal-regulated protein kinases (ERKs) are proline-directed, serine/threonine kinases that regulate a variety of cellular functions, including proliferation, differentiation, and plasticity. In the present report, we provide evidence that ERK2 and phosphatidylinositol-specific phospholipase C (PLC)-beta and -gamma isozymes interact in the rat hippocampal formation. We found that anti-PLC-beta1a, -beta2, -beta4, -gamma1 and -gamma2, but not -beta3, immune complexes isolated from rat hippocampal formation postnuclear fractions contain anti-ERK2 immunoreactivity. Further, we show that PLC catalytic activity is associated with anti-ERK2 immunoprecipitates isolated from the hippocampal formation, and that the amount of enzyme activity is significantly increased following fear-conditioned learning. The observed interactions may be mediated by consensus sequences conforming to an ERK2 docking site, termed a D-domain, that we identified in PLC-beta1a, -beta2, -beta4 -gamma1 and -gamma2. Based on these results, we propose that PLC-beta and PLC-gamma isozymes form signaling complexes with ERK2 in rat brain, and these complexes play critical roles in learning and memory, as well as a variety of other neuronal functions.

Identification of Phospholipase C-γ1 as a Mitogen-activated Protein Kinase Substrate

The discovery of sequence motifs that mediate protein-protein interactions, coupled with the availability of protein amino acid sequence data, allows for the identification of putative protein binding pairs. The present studies were based on our identification of an amino acid sequence in phosphatidylinositol-specific phospholipase C-gamma1 (PLC-gamma1) that fits the consensus sequence for a mitogen-activated protein kinase (MAPK) binding site, termed the D-domain. Extracellular signal-regulated kinase 2 (ERK2), an MAPK, and phospho-ERK2 were bound by an immobilized peptide sequence containing the identified PLC-gamma1 D-domain. Furthermore, a peptide containing the PLC-gamma1 D-domain was able to competitively inhibit the in vitro phosphorylation of recombinant PLC-gamma1 by recombinant phospho-ERK2, whereas a control peptide derived from a distant region of PLC-gamma1 was ineffective. Similarly, the peptide containing the PLC-gamma1 D-domain, but not the control peptide, competitively inhibited the in vitro phosphorylation of Elk-1 and c-Jun catalyzed by recombinant phospho-ERK2 and phospho-c-Jun N-terminal kinase 3 (phospho-JNK3), another type of MAPK, respectively. Incubation of anti-PLC-gamma1 immunocomplexes isolated from rat brain with recombinant phospho-ERK2 opposed the increase in PLC-gamma1-catalyzed hydrolysis of phosphatidylinositol 4,5-P(2) (PtdIns(4,5)P(2)), which was produced by a tyrosine kinase associated with the immunocomplexes, whereas in vitro phosphorylation of recombinant PLC-gamma1 by recombinant phospho-ERK2 did not alter PLC-gamma1-catalyzed PtdIns(4,5)P(2) hydrolysis. These studies have uncovered a previously unidentified mechanism for the integration of PLC-gamma1- and ERK2-dependent signaling.

Two-layer antibody capture of enzymes on the surface of microtiter plates: application to the study of the regulation of phospholipase C-gamma1 catalytic activity

In vitro quantification of the catalytic activity of an enzyme isoform requires the availability of selective agents that allow for either measurements in the presence of the other enzyme isoforms or purification of the isoform and subsequent performance of these measurements on the purified enzyme. Isozyme-specific antibodies are useful tools for these types of analyses. In the present report, we detail a method for the measurement of phospholipase C-gamma1 enzyme activity employing native enzyme that is immobilized on microtiter plates. The method uses biotinylated antiglobulin bound to streptavidin-coated microtiter plates to immobilize antiphospholipase C-gamma1 antibody and subsequently capture phospholipase C-gamma1 from brain tissue lysates. This method avoids biotinylation of the primary (antiphospholipase C-gamma1) antibody, making it less labor intensive than previously described methods for using streptavidin-coated plates; in addition, it is highly reproducible and sensitive and allows for quantification of enzyme activity. We employ the technique to show that one or more tyrosine kinases copurify with rat brain phospholipase C-gamma1. The method is applicable to the study of any enzyme isoform for which antibodies that capture the native form of the enzyme are available and could easily be employed in high-throughput procedures.