Mycoplasma Genitalium And Streptococcus Agalactiae Colonization In Pregnant Women: An Emerging Relationship

Introduction/Objective

Mycoplasma genitalium has been identified as an emerging sexually transmitted infection (STI) causing cervicitis, pelvic inflammatory disease and other gynecologic pathology. The prevalence of M. genitalium in pregnant women has not been determined, nor has frequency of co-infection with Streptococcus agalactiae (GBS). Neonatal sepsis caused by GBS is associated with black race and young maternal age with approximately 10%-30% of pregnant women colonized. The aim of this retrospective study was to investigate the possible association between M. genitalium infection and colonization with GBS in a large cohort of pregnant women from a tertiary care center in Houston, Texas.

Methods

Remnant endocervical samples collected from pregnant women attending clinics at the Baylor College of Medicine between September 2019 and December 2019 were screened for M. genitalium by transcription mediated amplification (Hologic, Inc. Marlborough, MA). Demographic, STI co-infection [Human papillomavirus (types 16,18), Trichomonas vaginalis, Chlamydia trachomatis, Neisseria gonorrhoeae, Treponema pallidum, and Herpes simplex virus], and GBS status data were recorded. Fisher’s exact test was performed for statistical analysis.

Results

719 total samples were collected and tested for M. genitalium. Of these, 41 (5.7%) were positive. The mean age of infected women was younger than noninfected women (24.9 vs. 28.1 years respectively p = 0.0004). More black women (34.2%) were infected with M. genitalium compared to white (14.6%) or other (51.2%) (p = 0.0003).

Rates of GBS colonization was significantly higher among women infected with M. genitalium compared to women who tested negative (58.3% vs. 16.1% respectively p = 0.002) and increased compared to national reported rates of GBS colonization. M. genitalium also showed a significant association with T. vaginalis (p=0.03), but no other STI co- infections studied.

Conclusion

Our data demonstrates that infection with M. genitalium may be associated with persistent GBS colonization. Further prospective studies are needed to further elucidate this relationship.

Cryopreservation of intact human articular cartilage

Damaged articular cartilage (AC) impairs joint function and many treatment techniques are being investigated to determine their long term results. Successful cryopreservation of AC can provide a reliable source of intact matrix with viable chondrocytes to maintain the cartilage over long periods of time. This study investigated the application of an established cryopreservation protocol to determine the recovery of intact chondrocytes from human AC. Ten millimeter diameter osteochondral dowels were harvested from two human donors. The cryopreservation protocol was performed and the samples were rapidly warmed from varying experimental holding temperatures (-10, -20, -30, -40 degrees C), with and without plunging into liquid nitrogen, using 1 M dimethyl sulfoxide as cryoprotectant. The cartilage was stained with membrane integrity dyes and viewed under fluorescence microscopy. The percent of intact chondrocytes was compared to fresh controls. Low recovery of intact chondrocytes was recorded from all temperature levels with and without cryoprotectant. The results of this experiment demonstrated that the cryopreservation procedure used to achieve moderate success with intact sheep AC was not successful with intact human AC and further investigation is required.

Transplantation of articular cartilage following a step-cooling cryopreservation protocol

Using a step-cooling cryopreservation protocol that held the tissue 60 min at -4 degrees C, 30 min at -8 degrees C, and 10 min at -40 degrees C before plunging into liquid nitrogen, we were able to get a substantial improvement in the magnitude and pattern of chondrocyte recovery following cryopreservation, achieving postthaw recoveries of 62 +/- 13%. These results are consistent with the hypothesis that ice growth within articular cartilage is planar, but they provide no direct support for that hypothesis. Transplanting (step-cooled) cryopreserved osteochondral allografts into adult Suffolk/Romanoff crossbred sheep for periods of 3 months and 1 year further tested the efficacy of the cryopreservation protocol. Unfortunately, the cryoinjury sustained by the chondrocytes during cryopreservation, although apparently nonlethal immediately after thawing in many cases, was not innocuous in the long term. The presence of large clusters of chondrocytes at 1 year after transplantation illustrates that cryoinjury not detectable with a membrane integrity assay can still have far-reaching effects on transplanted tissue.

Kinetics of osmotic water movement from rabbit patellar tendon and medial collateral ligament fibroblasts

The present study is part of a program to optimize the cryopreservation ligament and tendon allografts for the biological remodeling that occurs following transplantation. The osmotic behavior of fibroblasts from the medial collateral ligament (MCL) and the patellar tendon (PT) of new zealand white rabbits was measured to obtain the hydraulic conductivity (and its temperature dependence) as well as the osmotically inactive volume. MCL fibroblasts were found to have an isotonic cell volume of 3800 (m(3), an osmotically inactive volume of 1300 (microm(3), and a hydraulic conductivity of 0.56 (microm/min/atm at 20 degrees C with an activation energy of 10.9 kcal/mol. PT fibroblasts were found to have an isotonic cell volume of 6300 (microm(3), an osmotically inactive volume of 2000 (microm(3), and a hydraulic conductivity of 0.71 (m/min/atm at 20 degrees C with an activation energy of 10.1 kcal/mol.

Simultaneous optimization of cryoprobe placement and thermal protocol for cryosurgery

We demonstrate that it is possible to simultaneously optimize multiple cryoprobe placements and their thermal protocol for one freeze-thaw cycle. A numerical optimization algorithm is used and three different forms of objective function are examined in terms of algorithm convergence rate, minimum value of the chosen objective function, temperature-volume histograms and isotherm distributions. The optimization results depend on the initial values of the variables, the form of the objective function, optimization goals and the mathematical method adopted for gradient calculation. The proposed optimization model offers significant advantages over the previously reported semi-empirical approach to conformal cryotherapy, such as the ability to handle an unlimited number of variables and eliminating the need for the user input between iterations, thereby reducing, if not removing, the subjectivity of cryosurgery treatment planning.

Evidence of chondrocyte repopulation in adult ovine articular cartilage following cryoinjury and long-term transplantation

OBJECTIVE

To characterize the response of articular chondrocytes to a specific cryoinjury that leads to cluster formation following long-term transplantation.

DESIGN

Osteochondral dowels from 20 adult sheep were cryopreserved to optimize the recovery of chondrocytes immediately after thawing. The dowels were transplanted as allografts and observed at 3 and 12 months. Chondrocyte distribution and viability was assessed using paravital dyes after transplantation. Chondrocyte phenotype was assessed by in situ hybridization and immunohistochemistry to detect type II collagen. An anticentrosome antibody was used to identify cells undergoing cell cycle progression towards mitosis.

RESULTS

All cryopreserved grafts showed the presence of spheroidal clusters of chondrocytes 1 year after transplantation while the host cartilage adjacent to the graft appeared morphologically normal. The average size of the clusters increased from four cells at 3 months to 12 cells at 1 year. The chondrocytes in the clusters displayed newly formed type II collagen protein and mRNA. Some cells within clusters were observed with two centrosomes, indicative of cells progressing through the S phase of the cell cycle.

CONCLUSION

Adult articular chondrocytes retain the ability to repopulate the matrix, an ability which is demonstrated with this specific cryoinjury. This may be an initial stage of cartilage regeneration.

A model for the time dependent three-dimensional thermal distribution within iceballs surrounding multiple cryoprobes

A time dependent three-dimensional finite difference model of iceball formation about multiple cryoprobes has been developed and compared to experimental data. Realistic three-dimensional probe geometry is specified and the number of cryoprobes, the cryoprobe cooling rates, and the locations of the probes are arbitrary inputs by the user. The simulation accounts for observed longitudinal thermal gradients along the cryoprobe tips. Thermal histories for several points around commercially available cryoprobes have been predicted within experimental error for one, three, and five probe configurations. The simulation can be used to generate isotherms within the iceball at arbitrary times. Volumes enclosed by the iceball and any isotherms may also be computed to give the ablative ratio, a measure of the iceball's killing efficiency. This ratio was calculated as the volume enclosed by a critical isotherm divided by the total volume of the iceball for assumed critical temperatures of -20 and -40 degrees C. The ablative ratio for a single probe is a continuously decreasing function of time but when multiple probe configurations are used the ablative ratio increases to a maximum and then essentially plateaus. Maximum values of 0.44 and 0.55 were observed for three and five probe configurations, respectively, with an assumed critical temperature of -20 degrees C. Assuming a critical temperature of -40 degrees C, maximum ablative ratios of 0.21 and 0.3 for three and five probe configurations, respectively, were observed.

Flounder antifreeze peptides increase the efficacy of cryosurgery

Type I antifreeze protein (AFP) from the winter flounder (Pseudopleuronectes americanus) was used as an adjuvant to cryosurgery of subcutaneous tumors of Dunning AT-1 rat prostate cells grown in Copenhagen rats. The cryosurgical procedure was performed with a commercially available cryosurgery device (CRYO-HIT, Galil Medical) with clinically relevant single- and double-freeze protocols. Injury was assessed with the alamar blue indicator of metabolic activity. The assay gave anomalous results when used to assess the extent of injury immediately following the procedure, underestimating the extent of injury. However, a double-freeze procedure with antifreeze protein present was found to give significantly better ablation than a double-freeze without AFP or a single-freeze with or without AFP.

Suppression of high-density artefacts in x-ray CT images using temporal digital subtraction with application to cryotherapy

Image guidance in cryotherapy is usually performed using ultrasound. Although not currently in routine clinical use, x-ray CT imaging is an alternative means of guidance that can display the full 3D structure of the iceball, including frozen and unfrozen regions. However, the quality of x-ray CT images is compromised by the presence of high-density streak artefacts. To suppress these artefacts we applied temporal digital subtraction (TDS). This TDS method has the added advantage of improving the grey scale contrast between frozen and unfrozen tissue in the CT images. Two sets of CT images were taken of a phantom material, cryoprobes and a urethral warmer (UW) before and during the cryoprobe freeze cycle. The high density artefacts persisted in both image sets. TDS was performed on these two image sets using the corresponding mask image of unfrozen material and the same geometrical configuration of the cryoprobes and the UW. The resultant difference image had a significantly reduced artefact content. Thus TDS can be used to significantly suppress or eliminate high-density CT streak artefacts without reducing the metallic content of the cryoprobes. In vivo study needs to be conducted to establish the utility of this TDS procedure for CT assisted prostate or liver cryotherapy. Applying TDS in x-ray CT guided cryotherapy will facilitate estimation of the number and location of all frozen and unfrozen regions, potentially making cryotherapy safer and less operator dependent.

A semi-empirical treatment planning model for optimization of multiprobe cryosurgery

A model is presented for treatment planning of multiprobe cryosurgery. In this model a thermal simulation algorithm is used to generate temperature distribution from cryoprobes, visualize isotherms in the anatomical region of interest (ROI) and provide tools to assist estimation of the amount of freezing damage to the target and surrounding normal structures. Calculations may be performed for any given freezing time for the selected set of operation parameters. The thermal simulation is based on solving the transient heat conduction equation using finite element methods for a multiprobe geometry. As an example, a semi-empirical optimization of 2D placement of six cryoprobes and their thermal protocol for the first freeze cycle is presented. The effectiveness of the optimized treatment protocol was estimated by generating temperature-volume histograms and calculating the objective function for the anatomy of interest. Two phantom experiments were performed to verify isotherm locations predicted by calculations. A comparison of the predicted 0 degrees C isotherm with the actual iceball boundary imaged by x-ray CT demonstrated a spatial agreement within +/-2 mm.

Articular cartilage joint surface reconstruction techniques

There is renewed interest in joint surface reconstruction using a variety of new and evolving techniques for articular cartilage resurfacing. Neochondrogenesis and articular cartilage transplantation are gaining a prominent place in orthopaedic basic science research. The authors have published a reliable, repeatable, stable, and sensitive model utilizing osteochondral dowel core transplantation in an ovine model to assess various treatment and follow-up evaluation techniques for articular cartilage transplantation. As well, our laboratory has developed a handheld articular cartilage indentor for clinical assessment of biomechanical performance of joint surfaces. This article presents and reviews that model as well as a semiquantitative visual analog scale for documenting articular cartilage gross morphology. The results of magnetic resonance imaging of the osteochondral dowel transplants and the gross morphology grading are compared to the histological and histochemical grading and biochemical and biomechanical assessments to form the foundation for future work in this critical and important study area for clinical application.

Cryobiology of articular cartilage: ice morphology and recovery of chondrocytes

The cryopreservation of articular cartilage chondrocytes has been achieved with cells isolated from the cartilage matrix but has found only limited success when the tissue is left intact. Previous work with ovine cartilage has shown that cryopreservation of the chondrocytes of the superficial and deep zones is possible, but the cells of the intermediate zone have not been successfully cryopreserved. This finding led to the suggestion that there might be biological differences between chondrocytes of the different morphological zones that were responsible for this differential recovery. This study investigates the hypothesis that the cells of the intermediate zone are more sensitive to cryoinjury by introducing cuts in the cartilage so that cells of the intermediate zone have the same proximity to the outer surface of the tissue as the cells of the superficial zone. When this was done, it was found that cells of the intermediate zone could survive cryopreservation as well as the cells of the superficial zone when they were near a surface, but not when they were embedded deep within the tissue. Thus the hypothesis of a biological difference between the cells of the two zones being responsible for the differential recovery is disproved. It is further hypothesized that physical proximity to a surface leads to higher recovery as a result of planar ice growth into the cartilage.

Transplantation of cryopreserved osteochondral Dowel allografts for repair of focal articular defects in an ovine model

The purpose of this study was to test whether successful cryopreservation of osteochondral tissue is possible and whether, with the appropriate surgical procedure, it can be used for the successful repair of focal articular defects within joints. Fresh (nonfrozen) and snap-frozen (plunged in liquid nitrogen and thawed in a water bath at 37 degrees C, repeated three times) autografts were used as positive and negative controls, respectively. Snap-frozen, frozen (fresh tissue placed in a freezer at -80 degrees C), and cryopreserved (immersed in 10% dimethyl sulfoxide for 30 minutes and then frozen at 1 degrees C/min to -80 degrees C) allografts were transplanted into the knees of adult sheep. Outcomes were evaluated 3, 6, and 12 months after transplantation. The morphological, histological, biochemical, and biomechanical behaviors and characteristics of the graft cartilage, the host cartilage adjacent to the grafts, and the opposing tibial cartilage were assessed. Freezing protocols that yielded poor chondrocyte recovery after thawing (frozen and snap-frozen) resulted in poor overall graft outcome. The cryopreservation protocol, however, resulted in intermediate recovery (50%) of chondrocytes and in intermediate overall graft outcome compared with fresh autografts. The membrane integrity of the allograft chondrocytes immediately following cryopreservation was identified as the most reliable predictor of long-term outcome of the graft. Further improvements in cryopreservation technique may lead to an effective method of banking osteochondral tissue for successful transplantation for the repair of focal defects and larger joint reconstructions.

Localization of freezing injury in articular cartilage

In order to improve techniques for cryopreservation of articular cartilage, a study has been carried out to assess localization of cryoinjury in intact articular cartilage. Osteochondral dowels taken from the femoral condyles of sheep were subjected to graded freezing in the presence and absence of a cryoprotectant (10% DMSO). The graded freezing technique involves slow cooling (1 degree C/min) to various subzero temperatures before either rapid warming or rapid cooling by plunging in liquid nitrogen. This protocol allows assessment of the separate effects of rapid and slow freezing which damage cells in different ways, and the effects of cryoprotectants on the different types of damage. To assay damage, thin slices of cartilage were cut with a vibratome, which allows viable cells within the matrix to be observed microscopically. Injury was assessed by staining with fluorescent dyes to indicate damage to the plasma membrane. In general, tissue response was similar to that of cell suspensions, showing at least two mechanisms of injury acting on the cells: one at slow cooling rates and another at rapid cooling rates. The primary effect of DMSO was to reduce injury due to slow cooling. When the location of injury within the tissue was examined, it was found that chondrocytes of the intermediate layer were injured more extensively than those of either the deep or superficial layers.

The osmotic rupture hypothesis of intracellular freezing injury

A hypothesis of the nature of intracellular ice formation is proposed in which the osmotically driven water efflux that occurs in cells during freezing (caused by the increased osmotic pressure of the extracellular solution in the presence of ice) is viewed as the agent responsible for producing a rupture of the plasma membrane, thus allowing extracellular ice to propagate into the cytoplasm. This hypothesis is developed into a mathematical framework and the forces that are present during freezing are compared to the forces which are required to rupture membranes in circumstances unrelated to low temperatures. The theory is then applied to systems which have been previously studied to test implications of the theory on the nature of intracellular ice formation. The pressure that develops during freezing due to water flux is found to be sufficient to cause a rupture of the plasma membrane and the theory gives an accurate description of the phenomenology of intracellular ice formation.

Mechanisms of intracellular ice formation

The phenomenon of intracellular freezing in cells was investigated by designing experiments with cultured mouse fibroblasts on a cryomicroscope to critically assess the current hypotheses describing the genesis of intracellular ice: (a) intracellular freezing is a result of critical undercooling; (b) the cytoplasm is nucleated through aqueous pores in the plasma membrane; and (c) intracellular freezing is a result of membrane damage caused by electrical transients at the ice interface. The experimental data did not support any of these theories, but was consistent with the hypothesis that the plasma membrane is damaged at a critical gradient in osmotic pressure across the membrane, and intracellular freezing occurs as a result of this damage. An implication of this hypothesis is that mathematical models can be used to design protocols to avoid damaging gradients in osmotic pressure, allowing new approaches to the preservation of cells, tissues, and organs by rapid cooling.

Kinetics of osmotic water movement in chondrocytes isolated from articular cartilage and applications to cryopreservation

The ability of chondrocytes to survive conditions encountered during cryopreservation depends on the responses of the cells to the physiochemical changes that result when water is removed from the environment of the cells in the form of ice. Cellular responses are therefore closely related to the osmotic permeability properties of the plasma membrane. In order to optimize the conditions for cryopreservation of chondrocytes, osmotic properties of the chondrocyte membrane were determined from the kinetics of volume change in hypertonic solutions at different temperatures. The hydraulic conductivity of the plasma membrane was 0.305 +/- 0.025 micron3/micron2/min/atmosphere at 24 degrees C, with an Arrhenius activation energy of 8.06 kcal/mol. These values are similar to those reported for other cell types, but the osmotically inactive volume of the chondrocytes (0.41 +/- 0.04) was significantly higher than for other cells, implying that chondrocytes have a higher dry weight ratio or that they contain a higher proportion of osmotically inactive or bound water. These results were used to calculate the osmotic responses of chondrocytes at low temperatures and to predict that the least damaging cooling rate for isolated chondrocytes in the absence of cryoprotective compounds is 10 degrees C/min. The ultimate goal of this study is the development of an analytical model applicable to the optimization of techniques for cryopreservation of intact cartilage and other tissues.

A semiquantitative probe for radiation-induced normal tissue damage at the molecular level

Sheep antibodies to bovine type I collagen were employed in the immunohistochemical detection of type I collagen in lung tissue sections of irradiated LAF1 mice. A video image digitizing system was developed to estimate collagen levels, by assigning a numerical value (0-63) to each of approximately 53,800 picture elements (pixels) in the microscope field, according to the collagen-dependent fluorescence intensity at each locus. For lungs harvested 52 weeks subsequent to graded doses of 60Co gamma radiation between 0 and 10 Gy, a dose-dependent increase in type I collagen was observed in the alveolar walls. A reproducible increase was evident for doses as low as 5 Gy: doses of 7 to 10 Gy elicited type I collagen levels significantly elevated with respect to those of age-matched controls. These results are consistent with a role for type I collagen in the development of radiation-induced pulmonary fibrosis. The assay system developed here will be used to explore the role of connective tissue macromolecules in the development of radiation pneumonitis and fibrosis.