Hospital spending and length of stay attributable to perioperative adverse events for inpatient hip, knee, and spine surgery: a retrospective cohort study

BACKGROUND

The incremental hospital cost and length of stay (LOS) associated with adverse events (AEs) has not been well characterized for planned and unplanned inpatient spine, hip, and knee surgeries.

METHODS

Retrospective cohort study of hip, knee, and spine surgeries at an academic hospital in 2011-2012. Adverse events were prospectively collected for 3,063 inpatient cases using the Orthopaedic Surgical AdVerse Event Severity (OrthoSAVES) reporting tool. Case costs were retrospectively obtained and inflated to equivalent 2021 CAD values. Propensity score methodology was used to assess the cost and LOS attributable to AEs, controlling for a variety of patient and procedure factors.

RESULTS

The sample was 55% female and average age was 64; 79% of admissions were planned. 30% of cases had one or more AEs (82% had low-severity AEs at worst). The incremental cost and LOS attributable to AEs were $8,500 (95% confidence interval [CI]: 5100-11,800) and 4.7 days (95% CI: 3.4-5.9) per admission. This corresponded to a cumulative $7.8 M (14% of total cohort cost) and 4,290 bed-days (19% of cohort bed-days) attributable to AEs. Incremental estimates varied substantially by (1) admission type (planned: $4,700/2.4 days; unplanned: $20,700/11.5 days), (2) AE severity (low: $4,000/3.1 days; high: $29,500/11.9 days), and (3) anatomical region (spine: $19,800/9 days; hip: $4,900/3.8 days; knee: $1,900/1.5 days). Despite only 21% of admissions being unplanned, adverse events in these admissions cumulatively accounted for 59% of costs and 62% of bed-days attributable to AEs.

CONCLUSIONS

This study comprehensively demonstrates the considerable cost and LOS attributable to AEs in orthopaedic and spine admissions. In particular, the incremental cost and LOS attributable to AEs per admission were almost five times as high among unplanned admissions compared to planned admissions. Mitigation strategies focused on unplanned surgeries may result in significant quality improvement and cost savings in the healthcare system.

Utility of the spinal instability neoplastic score to identify patients with Gorham-Stout disease requiring spine surgery

Background:

Gorham-Stout disease (GSD) is a rare syndrome presenting with progressive osteolysis which in the spine can lead to cord injury, instability, and deformity. Here, the early spine surgery may prevent catastrophic outcomes.

Case Description:

A 25-year-old male with GSD involving the T2 to T6 levels presented with acute traumatic kyphoscoliosis at T3 and T4 and left lower extremity paraparesis. The CT scan 4 weeks before this showed progressing osteolysis versus the CT 5 years ago. Unfortunately, the patient underwent delayed treatment resulting in permanent neurological sequelae. Surgery included a laminectomy and vertebrectomy of T3/T4 with instrumented fusion from T1-10. The use of the spinal instability neoplastic score (SINS) is a useful tool to prompt early referral to spine surgeons.

Conclusion:

We recommend using the SINS score in GSD patients who develop spinal lesions to prompt early referral for consideration of surgery.

Characteristics of Upper Limb Impairment Related to Degenerative Cervical Myelopathy: Development of a Sensitive Hand Assessment (Graded Redefined Assessment of Strength, Sensibility, and Prehension Version Myelopathy)

BACKGROUND

Degenerative cervical myelopathy (DCM) involves spinal cord compression, which causes neurological decline. Neurological impairment in DCM is variable and can involve complex upper limb dysfunction including loss of manual dexterity, hyperreflexia, focal weakness, and sensory impairment. The modified Japanese Orthopaedic Association (mJOA) score relies on the patients’ subjective perceptions, whereas existing objective measures such as strength and sensory testing do not capture subtle changes in dexterity and function.

OBJECTIVE

1) To characterize arm and hand function in DCM; and 2) To develop and validate Graded Redefined Assessment of Strength, Sensibility, and Prehension Version-Myelopathy (GRASSP-M), a clinical assessment that quantifies upper limb impairment.

METHODS

A total of 148 DCM patients (categorized into mild, moderate, and severe based on mJOA grade) and 21 healthy subjects were enrolled. A complete neurological exam, the mJOA, the QuickDASH, grip dynamometry, and the GRASSP-M were administered.

RESULTS

Strength, sensation, and manual dexterity significantly declined with increasing DCM severity (P ≤ .05). Impairment in hand dexterity showed better discrimination between mild, moderate, and severe DCM categories than strength or sensation. The GRASSP-M was found to be both a reliable (intraclass correlation coefficient >0.75 for intra- and inter-rater reliability) and valid (with both concurrent and construct validity) tool.

CONCLUSION

These results demonstrate that patients’ subjective reporting of functional status, especially in the mild DCM category, may underrepresent the extent of functional impairment. The GRASSP-M is an objective tool designed to characterize patients’ functional impairment related to the upper limb, which proves useful to diagnose and quantify mild dysfunction, monitor patients for deterioration, and help determine when patients should be treated surgically.

Metastatic Spine Tumor Epidemiology: Comparison of Trends in Surgery Across Two Decades and Three Continents

BACKGROUND

Indications for surgery for symptomatic spinal metastases have become better defined in recent years, and suitable outcome measures have been established against a changing backdrop of patient characteristics, tumor behavior, and oncologic treatments. Nonetheless, variations still exist in the local management of patients with spinal metastases. In this study, we aimed to review global trends and habits in the surgical treatment of symptomatic spinal metastases, and to examine how these have changed over the last 25 years.

METHODS

In this cohort study of consecutive patients undergoing surgery for symptomatic spinal metastases, data were collected using a secure Internet database from 22 centers across 3 continents. All patients were invited to participate in the study, except those unable or unwilling to give consent.

RESULTS

There was a higher incidence of colonic, liver, and lung carcinoma metastases in Asian countries, and more frequent presentation of breast, prostate, melanoma metastases in the West. Trends in surgical technique were broadly similar across the centers. Overall survival rates after surgery were 53% at 1 year, 31% at 2 years, and 10% at 5 years after surgery (standard error 0.013 for all). Survival improved over successive time periods, with longer survival in patients who underwent surgery in 2011-2016 compared with those who underwent surgery in earlier time periods.

CONCLUSIONS

Surgical habits have been fairly consistent among countries worldwide and over time. However, patient survival has improved in later years, perhaps due to medical advances in the treatment of cancer, improved patient selection, and operating earlier in the course of disease.

A Clinical Practice Guideline for the Management of Patients With Acute Spinal Cord Injury and Central Cord Syndrome: Recommendations on the Timing (≤24 Hours Versus >24 Hours) of Decompressive Surgery

OBJECTIVE

To develop recommendations on the timing of surgical decompression in patients with traumatic spinal cord injury (SCI) and central cord syndrome.

METHODS

A systematic review of the literature was conducted to address key relevant questions. A multidisciplinary guideline development group used this information, along with their clinical expertise, to develop recommendations for the timing of surgical decompression in patients with SCI and central cord syndrome. Based on GRADE, a strong recommendation is worded as "we recommend," whereas a weak recommendation is presented as "we suggest."

RESULTS

Conclusions from the systematic review included (1) isolated studies reported statistically significant and clinically important improvements following early decompression at 6 months and following discharge from inpatient rehabilitation; (2) in one study on acute central cord syndrome without instability, a marginally significant improvement in total motor scores was reported at 6 and 12 months in patients managed with early versus late surgery; and (3) there were no significant differences in length of acute care/rehabilitation stay or in rates of complications between treatment groups. Our recommendations were: "We suggest that early surgery be considered as a treatment option in adult patients with traumatic central cord syndrome" and "We suggest that early surgery be offered as an option for adult acute SCI patients regardless of level." Quality of evidence for both recommendations was considered low.

CONCLUSIONS

These guidelines should be implemented into clinical practice to improve outcomes in patients with acute SCI and central cord syndrome by promoting standardization of care, decreasing the heterogeneity of management strategies, and encouraging clinicians to make evidence-informed decisions.

A Clinical Practice Guideline for the Management of Patients With Acute Spinal Cord Injury: Recommendations on the Type and Timing of Anticoagulant Thromboprophylaxis

INTRODUCTION

The objective of this study is to develop evidence-based guidelines that recommend effective, safe and cost-effective thromboprophylaxis strategies in patients with spinal cord injury (SCI).

METHODS

A systematic review of the literature was conducted to address key questions relating to thromboprophylaxis in SCI. Based on GRADE (Grading of Recommendation, Assessment, Development and Evaluation), a strong recommendation is worded as "we recommend," whereas a weaker recommendation is indicated by "we suggest."

RESULTS

Based on conclusions from the systematic review and expert panel opinion, the following recommendations were developed: (1) "We suggest that anticoagulant thromboprophylaxis be offered routinely to reduce the risk of thromboembolic events in the acute period after SCI;" (2) "We suggest that anticoagulant thromboprophylaxis, consisting of either subcutaneous low-molecular-weight heparin or fixed, low-dose unfractionated heparin (UFH) be offered to reduce the risk of thromboembolic events in the acute period after SCI. Given the potential for increased bleeding events with the use of adjusted-dose UFH, we suggest against this option;" (3) "We suggest commencing anticoagulant thromboprophylaxis within the first 72 hours after injury, if possible, in order to minimize the risk of venous thromboembolic complications during the period of acute hospitalization."

CONCLUSIONS

These guidelines should be implemented into clinical practice in patients with SCI to promote standardization of care, decrease heterogeneity of management strategies and encourage clinicians to make evidence-informed decisions.

A Clinical Practice Guideline for the Management of Patients With Acute Spinal Cord Injury: Recommendations on the Type and Timing of Rehabilitation

INTRODUCTION

The objective of this study is to develop guidelines that outline the appropriate type and timing of rehabilitation in patients with acute spinal cord injury (SCI).

METHODS

A systematic review of the literature was conducted to address key questions related to rehabilitation in patients with acute SCI. A multidisciplinary guideline development group used this information, and their clinical expertise, to develop recommendations for the type and timing of rehabilitation. Based on GRADE (Grading of Recommendation, Assessment, Development and Evaluation), a strong recommendation is worded as "we recommend," whereas a weaker recommendation is indicated by "we suggest.

RESULTS

Based on the findings from the systematic review, our recommendations were: (1) We suggest rehabilitation be offered to patients with acute spinal cord injury when they are medically stable and can tolerate required rehabilitation intensity (no included studies; expert opinion); (2) We suggest body weight-supported treadmill training as an option for ambulation training in addition to conventional overground walking, dependent on resource availability, context, and local expertise (low evidence); (3) We suggest that individuals with acute and subacute cervical SCI be offered functional electrical stimulation as an option to improve hand and upper extremity function (low evidence); and (4) Based on the absence of any clear benefit, we suggest not offering additional training in unsupported sitting beyond what is currently incorporated in standard rehabilitation (low evidence).

CONCLUSIONS

These guidelines should be implemented into clinical practice to improve outcomes and reduce morbidity in patients with SCI by promoting standardization of care, decreasing the heterogeneity of management strategies and encouraging clinicians to make evidence-informed decisions.

A Clinical Practice Guideline for the Management of Patients With Acute Spinal Cord Injury: Recommendations on the Use of Methylprednisolone Sodium Succinate

INTRODUCTION

The objective of this guideline is to outline the appropriate use of methylprednisolone sodium succinate (MPSS) in patients with acute spinal cord injury (SCI).

METHODS

A systematic review of the literature was conducted to address key questions related to the use of MPSS in acute SCI. A multidisciplinary Guideline Development Group used this information, in combination with their clinical expertise, to develop recommendations for the use of MPSS. Based on GRADE (Grading of Recommendation, Assessment, Development and Evaluation), a strong recommendation is worded as "we recommend," whereas a weaker recommendation is indicated by "we suggest."

RESULTS

The main conclusions from the systematic review included the following: (1) there were no differences in motor score change at any time point in patients treated with MPSS compared to those not receiving steroids; (2) when MPSS was administered within 8 hours of injury, pooled results at 6- and 12-months indicated modest improvements in mean motor scores in the MPSS group compared with the control group; and (3) there was no statistical difference between treatment groups in the risk of complications. Our recommendations were: (1) "We suggest not offering a 24-hour infusion of high-dose MPSS to adult patients who present after 8 hours with acute SCI"; (2) "We suggest a 24-hour infusion of high-dose MPSS be offered to adult patients within 8 hours of acute SCI as a treatment option"; and (3) "We suggest not offering a 48-hour infusion of high-dose MPSS to adult patients with acute SCI."

CONCLUSIONS

These guidelines should be implemented into clinical practice to improve outcomes and reduce morbidity in SCI patients.

A Clinical Practice Guideline for the Management of Patients With Acute Spinal Cord Injury: Recommendations on the Role of Baseline Magnetic Resonance Imaging in Clinical Decision Making and Outcome Prediction

INTRODUCTION

The objective of this guideline is to outline the role of magnetic resonance imaging (MRI) in clinical decision making and outcome prediction in patients with traumatic spinal cord injury (SCI).

METHODS

A systematic review of the literature was conducted to address key questions related to the use of MRI in patients with traumatic SCI. This review focused on longitudinal studies that controlled for baseline neurologic status. A multidisciplinary Guideline Development Group (GDG) used this information, their clinical expertise, and patient input to develop recommendations on the use of MRI for SCI patients. Based on GRADE (Grading of Recommendation, Assessment, Development and Evaluation), a strong recommendation is worded as "we recommend," whereas a weaker recommendation is indicated by "we suggest."

RESULTS

Based on the limited available evidence and the clinical expertise of the GDG, our recommendations were: (1) "We suggest that MRI be performed in adult patients with acute SCI prior to surgical intervention, when feasible, to facilitate improved clinical decision-making" (quality of evidence, very low) and (2) "We suggest that MRI should be performed in adult patients in the acute period following SCI, before or after surgical intervention, to improve prediction of neurologic outcome" (quality of evidence, low).

CONCLUSIONS

These guidelines should be implemented into clinical practice to improve outcomes and prognostication for patients with SCI.

* In Vitro Generated Intervertebral Discs: Toward Engineering Tissue Integration

The intervertebral disc (IVD) is composed of nucleus pulposus (NP) surrounded by multilamellated annulus fibrosus (AF), and is located between the vertebral bodies. Current treatments for chronic neck or low back pain do not completely restore the functionality of degenerated IVDs. Thus, developing biological disc replacements is an approach of great interest. Given the complex structure of the IVD, tissue engineering of the individual IVD components and then combining them together may be the only way to achieve this. The engineered disc must then be able to integrate into the host spine to ensure mechanical stability. The goal of this study was to generate an integrated model of an IVD in vitro. Multilamellated AF tissues were generated in vitro using aligned nanofibrous polycarbonate urethane scaffolds and AF cells. After 3 weeks in culture, it was placed around NP tissue formed on and integrated with a porous bone substitute material (calcium polyphosphate). The two tissues were cocultured to fabricate the IVD model. The AF tissue composed of six lamellae containing type I collagen-rich extracellular matrix (ECM) and the NP tissue had type II collagen- and aggrecan-rich ECM. Immunofluorescence studies showed both type I and II collagen at the AF-NP interface. There was evidence of integration of the tissues. The peel test for AF lamellae showed an interlamellar shear stress of 0.03 N/mm. The AF and NP were integrated as the pushout test demonstrated that the AF-NP interface had significantly increased mechanical stability by 2 weeks of coculture. To evaluate if these tissues remained integrated, allogeneic IVD model constructs were implanted into defects freshly made in the NP-inner AF and bone of the bovine coccygeal spine. One month postimplantation, the interfaces between the AF lamellae remained intact and there was integration with the host AF tissue. No inflammatory reaction was noted at this time period. In summary, an engineered IVD implant with mechanically stable integration between AF lamellae and AF-NP can be generated in vitro. Further study is required to scale up the size of this construct and evaluate its ability to serve as a biological disc replacement.

Survival and Clinical Outcomes in Surgically Treated Patients With Metastatic Epidural Spinal Cord Compression: Results of the Prospective Multicenter AOSpine Study

PURPOSE

Although surgery is used increasingly as a strategy to complement treatment with radiation and chemotherapy in patients with metastatic epidural spinal cord compression (MESCC), the impact of surgery on health-related quality of life (HRQoL) is not well established. We aimed to prospectively evaluate survival, neurologic, functional, and HRQoL outcomes in patients with MESCC who underwent surgical management.

PATIENTS AND METHODS

One hundred forty-two patients with a single symptomatic MESCC lesion who were treated surgically were enrolled onto a prospective North American multicenter study and were observed at least up to 12 months. Clinical data, including Brief Pain Inventory, ASIA (American Spinal Injury Association) impairment scale, SF-36 Short Form Health Survey, Oswestry Disability Index, and EuroQol 5 dimensions (EQ-5D) scores, were obtained preoperatively, and at 6 weeks and 3, 6, 9, and 12 months postoperatively.

RESULTS

Median survival time was 7.7 months. The 30-day and 12-month mortality rates were 9% and 62%, respectively. There was improvement at 6 months postoperatively for ambulatory status (McNemar test, P < .001), lower extremity and total motor scores (Wilcoxon signed rank test, P < .001), and at 6 weeks and 3, 6, and 12 months for Oswestry Disability Index, EQ-5D, and pain interference (paired t test, P < .013). Moreover, at 3 months after surgery, the ASIA impairment scale grade was improved (Stuart-Maxwell test P = .004). SF-36 scores improved postoperatively in six of eight scales. The incidence of wound complications was 10% and 2 patients required a second surgery (screw malposition and epidural hematoma).

CONCLUSION

Surgical intervention, as an adjunct to radiation and chemotherapy, provides immediate and sustained improvement in pain, neurologic, functional, and HRQoL outcomes, with acceptable risks in patients with a focal symptomatic MESCC lesion who have at least a 3 month survival prognosis.

Surgical resection of epidural disease improves local control following postoperative spine stereotactic body radiotherapy

BACKGROUND

Spine stereotactic body radiotherapy (SBRT) is increasingly being applied to the postoperative spine metastases patient. Our aim was to identify clinical and dosimetric predictors of local control (LC) and survival.

METHODS

Eighty patients treated between October 2008 and February 2012 with postoperative SBRT were identified from our prospective database and retrospectively reviewed.

RESULTS

The median follow-up was 8.3 months. Thirty-five patients (44%) were treated with 18-26 Gy in 1 or 2 fractions, and 45 patients (56%) with 18-40 Gy in 3-5 fractions. Twenty-one local failures (26%) were observed, and the 1-year LC and overall survival (OS) rates were 84% and 64%, respectively. The most common site of failure was within the epidural space (15/21, 71%). Multivariate proportional hazards analysis identified systemic therapy post-SBRT as the only significant predictor of OS (P = .02) and treatment with 18-26 Gy/1 or 2 fractions (P = .02) and a postoperative epidural disease grade of 0 or 1 (0, no epidural disease; 1, epidural disease that compresses dura only, P = .003) as significant predictors of LC. Subset analysis for only those patients (n = 48/80) with high-grade preoperative epidural disease (cord deformed) indicated significantly greater LC rates when surgically downgraded to 0/1 vs 2 (P = .0009).

CONCLUSIONS

Postoperative SBRT with high total doses ranging from 18 to 26 Gy delivered in 1-2 fractions predicted superior LC, as did postoperative epidural grade.

The role of minimally invasive techniques in the management of spinal neoplastic disease: a review

This review article provides a general overview of the role of minimal access spine surgery (MASS) in the context of spinal neoplastic disease. Illustrative cases included outline advances in new techniques with a focus on improved patient outcome. The article challenges the traditional indication for surgical decompression by considering the objective of better local control of tumor. MASS can be used to improve focused environments in which the delivery of a higher and safer dose of radiation can be accomplished. This combination of treatment has the purpose of better overall survival for some cancer patients by positively influencing local control. The role of surgical intervention in the context of managing cancer patients is continuously being redefined for this challenging population. The modern surgeon must stay abreast of all advances in their field in order to provide the best care for their patients.

Minimal Access Spine Surgery (MASS) for Decompression and Stabilization Performed as an Out-Patient Procedure for Metastatic Spinal Tumours Followed by Spine Stereotactic Body Radiotherapy (SBRT): First Report of Technique and Preliminary Outcomes

We report a novel approach in the treatment of spinal metastases with epidural disease and mechanical instability using a combined minimal access spine surgery (MASS) technique followed by spine stereotactic body radiotherapy (SBRT). This study was performed as a retrospective review of the first ten consecutive patients treated with this combined approach. The MASS technique was based on a tubular retraction system to gain access for decompression and mechanical stabilization achieved using methyl-methacrylate (MMA) applied under direct visualization. SBRT consisted of one to five image-guided high dose per fraction treatments. Eight patients were symptomatic at baseline. Pain, disability, and quality of life (QOL) were prospectively determined using the visual analogue score (VAS), Oswestry Disability Index (ODI), and Short-Form-36 version 2, respectively. The median follow-up was 13 months (range, 3–18). MASS successfully decompressed each patient. The median blood loss was 335 ml. Following MASS, the median time to SBRT treatment planning was 6.5 days and subsequent median time to treatment was 7 days. Local control was observed in 7 of the 10 patients. Improvements in VAS, ODI and QOL were observed post-SBRT. We report preliminary efficacy for our MASS-SBRT combined approach for patients with spinal metastases, mechanical pain and epidural disease.

Technique for stereotactic body radiotherapy for spinal metastases

Stereotactic body radiotherapy (SBRT) is an emerging technique for spinal tumours that is a natural succession to brain radiosurgery. The spine is an ideal site for SBRT due to its relative immobility and the potential clinical benefits of high dose delivery, particularly to optimise local control and avoid disease progression that can result in spinal cord compression. However, the proximity of the tumour to the spinal cord, with the potential for radiation myelopathy if the dose is delivered inaccurately or if the spinal cord dose limit is set too high, demands technical accuracy with radiation myelopathy a feared complication. Spine SBRT has been delivered with either a robotic-based linac system such as the Cyberknife, or with linac-based systems equipped with a multileaf collimator and image guidance system. Regardless of the technology, spine SBRT demands sophisticated treatment planning and delivery. This case-based technical review outlines the SBRT apparatus, planning and treatment delivery in use at the University of Toronto, Toronto, Canada.

Adoptive transfer of CD4+CD25+ regulatory cells combined with low-dose sirolimus and anti-thymocyte globulin delays acute rejection of renal allografts in Cynomolgus monkeys

Although donor alloantigen specific Treg cells play an important role in transplant tolerance, therapeutic applications are limited by their low frequency. In this study, isolated Tregs from Cynomolgus monkeys were efficiently expanded by a co-culture system, and maintained suppressive function on the proliferation of CD4(+) effector cells in vitro. Adoptive transfer of expanded donor alloantigen specific Tregs without any immunosuppressants could prolong survival of MHC-mismatched allografts in Cynomolgus monkeys. To reach the feasibility of clinical transplantation, our objectives focused on whether exposure of monkey Tregs to immunosuppressants could preserve suppressive function in vitro and in vivo. The results showed that low-dose sirolimus selectively expanded Tregs, increased the expression of CD25(bright) and Foxp3 markers, and suppressed TCR- or allo-antigens induced CD4(+) T cell proliferation in vitro. In vivo, after pre-treated with anti-thymocyte globulin (ATG) for consecutive 3days, a 14-day therapy of adoptive infusion of donor alloantigen-specific Tregs combined with low-dose sirolimus delayed acute rejection of renal allografts in Cynomolgus monkeys, showing an MST of 48.5days as compared with those of untreated and sirolimus-treated monkeys (7days and 22days). The frequencies of CD4(+)CD25(bright) T cells were significantly elevated in mesenteric lymph nodes vs. those in inguino lymph nodes and peripheral blood. In summary, expanded donor alloantigen specific Tregs exposed to sirolimus can preserve inhibition in vitro and in vivo. Tregs are more resistant to sirolimus than other T cells. Expanded donor alloantigen specific Tregs combined with sirolimus and ATG prolongs renal allograft survival in monkeys, suggesting that sirolimus might be one of the best synergists for Tregs therapy.

Sensitivity to methylmercury-induced autoimmune disease in mice correlates with resistance to apoptosis of activated CD4+ lymphocytes

The sensitivity of splenic lymphoid cells to apoptosis induced by low concentrations of methylmercury (MeHgCl) has been examined in C57BL/6 and SJL mice, which are, respectively, resistant and sensitive to a genetically determined autoimmune disease induced by subtoxic doses of MeHgCl. To determine the implications of subtoxic doses of MeHgCl in the susceptibility of SJL mice to autoimmune disease, Concanavalin A (ConA) stimulated spleen cells from both mouse strains were treated in vitro with MeHgCl concentrations varying between 0.001 and 1.0 microM for 48h. Results have shown that ConA-activated splenic lymphoid cells from SJL mice increased in the presence of low concentrations of MeHgCl while the number of lymphoid cells from C57BL/6 mice rather decreased. Flow cytometric analysis of the cells showing a typical lymphoid forward scatter (FSC)/side scatter (SSC) pattern (region R1), and those characterized by a lower FSC and a higher SSC parameters (region R2), morphologically corresponding to apoptotic cells, revealed that lymphoid cells from C57BL/6 mice suffered a dose-dependent shift from region R1 toward region R2 when treated with concentrations ranging between 0.01 and 1 microM of MeHgCl. However, SJL splenic lymphoid cells cultured in the presence of low concentrations of MeHgCl proved more resistant to apoptosis. The level of apoptosis induced by MeHgCl in both regions was verified by AnnexinV-propidium iodide (PI) and TdT-mediated dUTP nick end labeling (TUNEL) immunolabelings. Phenotyping of lymphoid cells from both mouse strains cultured in the presence of low concentrations of MeHgCl and stimulated with ConA, indicated that CD4+ T cells from SJL mice increased while the corresponding cell subset from C57BL/6 mice became apoptotic. The resistance to apoptosis of ConA-activated lymphoid cells from SJL mice seemed related to an increase of CD4+ cells induced by the lower concentrations of MeHgCl (0.001 and 0.01 microM). However, these SJL cells were sensitive to anti-Fas-mediated apoptosis while residual anti-Fas-resistant cells from C57BL/6 mice were, themselves, sensitive to MeHgCl-induced apoptosis. The in vivo significance of these results has been confirmed by an observed increase in splenic cellularity and in the percentage of activated CD4+ cells from SJL mice. These increases were not observed in C57BL/6 mice.

Intrahepatic alpha beta-TcRintermediate LFA-1high T cells are stimulated during mouse hepatitis viral infection

Mouse hepatitis virus type 3 (MHV3), a coronavirus, is an excellent animal model for the study of thymic and extrathymic T cell subpopulation disorders induced during the viral hepatitis. To understand local hepatic immune responses, the phenotypes of resident hepatic lymphocytes were determined and compared that of splenic and thymic T cell subpopulations during the acute viral hepatitis induced by MHV3 in susceptible C57BL/6 mice. Single positive (SP) CD4+ or CD8+ cells strongly increased in the liver. A specific cell population, the double positive (CD4+ C8+) cells, normally present in liver and thymic cell preparations, decreased in C57BL/6 mice following the viral infection. alpha beta-TcRintermediate T cells shifted toward alpha beta-TcRhigh T cells in the liver and thymus of infected mice, but not in their spleen. The specific alpha beta-TcRint or high lymphocytes occurring in the liver of MHV3-infected mice expressed higher levels of leukocyte function antigen-1 (LFA-1) and Pgp-1 (CD44) activation markers, suggesting that they were either activated or antigen-experienced during the viral infection. No significant changes in T cell subpopulations were detected in the spleen. These observations suggest that MHV3 infection could induce an early in situ stimulation of resident hepatic T cells, despite a peripheral immunodeficiency in the thymus and spleen.

Mouse hepatitis viral infection induces an extrathymic differentiation of the specific intrahepatic alpha beta-TCRintermediate LFA-1high T-cell population

Mouse hepatitis virus type 3 (MHV3), a coronavirus, is an excellent model for the study of thymic and extrathymic T-cell subpopulation disorders induced during viral hepatitis. It was recently reported that, in addition to the intrathymic T-cell differentiation pathway, an extrathymic differentiation pathway of alpha beta-T-cell receptor (TCR) T lymphocytes exists in the liver, and becomes important under pathological situations such as autoimmune diseases, malignancies or hepatic bacterial infections. In the present study, we compared the phenotypes of resident hepatic, splenic or thymic T-cell subpopulations during the acute viral hepatitis induced by HMV3 in susceptible C57BL/6 mice. The number of liver-resident mononuclear cells (MNC) increased during the viral infection, while cellularity decreased. Single positive (SP) CD4+ cells strongly increased in both the liver and thymus, while double positive (DP) (CD4+ CD8+) cells, present in the liver and thymus of mock-infected mice, decreased in C57BL/6 mice during the viral infection. A shift of alpha beta-TCRintermediate T cells toward alpha beta-TCRhigh was evidenced in the liver and thymus of infected mice, but not in the spleen. The few alpha beta-TCRint double negative (DN) (CD4-CD8-) cells also decreased following viral infection. alpha beta-TCRint or high lymphocytes expressing high levels of leucocyte function antigen-1 (LFA-1) increased in the liver of MHV3-infected mice. In addition, liver-resident T cells expressed strongly the CD44 (Pgp-1) activation marker, suggesting that they were either activated or antigen experienced during the viral infection. No significant change in T-cell subpopulations was detected in the spleen, suggesting that MHV3 infection could induce an early in situ differentiation of resident hepatic T cells rather than a recruitment of lymphocytes from peripheral lymphoid organs.