Human cytokine expression profile in various conditioned media for in vitro expansion bone marrow and umbilical cord blood immunophenotyped mesenchymal stem cells

Introduction

Bone marrow (BM) represents the major source of mesenchymal stem cells (MSCs); however, umbilical cord blood (UCB) MSCs have some advantages over BM, such as a higher differentiation capability and noninvasive collection methods.

Objectives

We compared antigen expression and cytokine-secretion by MSC from BM and UCB expanded with media supplemented with fetal bovine serum (FBS) or human platelet lysate (HPL).

Materials and Methods

We compared protocols for the expansion of hMSC starting from samples of BM or UCB by morphological analysis, calculation of population doubling numbers, and cytometry techniques using monoclonal antibodies (BD Biosciences). Using the last technique, cytokines were detected in brain homogenate supernatant fluids of MSC cultured in various media, using the Bio-Plex cytokine assay system (BD Biosciences).

Results

Calculating the number population doubling (PD) and colony-forming unit-¹fibroblast (CFU-F) assays showed significantly better expansion with HPL compared with a selected batch of FBS and within fewer days: PD about 5 for 10%HPL versus 25 for fibroblast growth factor2 (FGF2) medium. By flow cytometry, we observed a greater number of BM MSCs compared with UCB MSCs, as well as differences in the expression of some MSC antigens, particularly CD105, CD90, and CD31. Analysis of cytokines: FGFb, RANTES, VEGF, IL-6, IL-8, G-CSF, and GM-CSF showed only some of them to be expressed: namely, IL-6, IL-8, and VEGF. MSCs derived from UCB showed low concentrations of these cytokines compared with MSCs derived from BM.     

Effects of mechanical strain on oxygen free radical system in bone marrow mesenchymal stem cells from children

Background

Physiological loading is widely believed to be beneficial in maintaining skeletal integrity by stimulating new bone formation through increases in osteoblastic activity and concomitant decreases in osteoclastic activity. However, excessive or nonphysiological loading is associated with bone injuries, including stress fractures and osteoporotic fractures, thereby leading to a decreased functional capacity of bone. It is known that the excessive generation of reactive oxygen species (ROS) is a significant factor underlying tissue injury observed in many disease states. The aim of this study was to study the effects of mechanical strain on oxygen free radical system [ROS, superoxide dismutase (SOD) and malondialdehyde (MDA)] in bone marrow mesenchymal stem cells (MSCs) from children.

Methods

To determine whether extreme levels of mechanical strain enhance ROS synthesis, we loaded cyclic tensile stretch of varying magnitude on MSCs. After MSCs were stimulated by mechanical strain, ROS labelled with 2,7-dichlorodihydrofluorescein (DCFH) fluorescent probe in cells were detected by flow cytometry (FCM) whilst SOD activity and MDA level were detected by xanthine oxidase method and thiobarbituric acid method, respectively.

Results

Extreme levels (>12%) of mechanical strain applied to children's MSCs enhanced ROS synthesis, decreased the activity of SOD and increased the level of MDA, in a time- and magnitude-dependent fashion.

Conclusions

These data suggest that excessive magnitude of cyclic tensile strain (>12%) could induce oxygen free radical disequilibrium, resulting in cytotoxicity. The findings may have clinical implications for orthopaedic practice.     

The expression and distribution of xenogeneic targeted antigens on porcine bone tissue

Objective

The objective of this study was to investigate the distribution of α-galactosyl (α-Gal), major histocompatibility complex (MHC)-I, and MHC-II antigens on adult porcine bone tissue.

Methods

Distribution of α-Gal, MHC-I, and MHC-II antigens on porcine bone tissue were observed using immunohistochemistry.

Results

α-Gal, MHC-I xenogeneic antigens were extensively observed on the surface of bone marrow cells, osteocytes, osteoblasts, and Harversian canals; MHC-II antigens were mainly expressed on bone marrow cells.

Conclusion

α-Gal, MHC-I, and MHC-II are the main xenogeneic antigens that must be deleted to avoid xenogeneic immune reactions against bone xenografts.     

Biologics and donor bone marrow cells for targeted immunomodulation in vascularized composite allotransplantation: a translational trial in swine

Introduction

Bone marrow (BM) infusion following organ transplantation is a prerequisite for potential donor-antigen-specific tolerance induction. We developed a preclinical swine model to determine the optimal dose of BM cells to achieve microchimerism. Furthermore, induction therapy was optimized by augmenting the BM infusion with biologics in the form of costimulatory blockade: cytotoxic T-lymphocyte antigen 4 immunoglobulin (CTLA4-Ig).

Materials and Methods

Yucatan miniature swine (n = 12) underwent total body and thymic irradiation for cytodepletion. Animal groups received 15, 30, or 60 million cells per kilogram of whole unmodified BM. The optimal dose of BM cell infusion (BMT) was then applied to subsequent experiments evaluating the addition of CTLA4lg. Group 1 (control) received no treatment. Group 2 received FK506 only; group 3 received irradiation, BMT, and FK506; group 4 received FK506 and CTLA4-lg.

Results

Microchimerism was established in all animals after BM cell infusion; at postoperative day 9, it was significantly increased for 60 million cells per kilogram (P = .0001). Transplanted animals in group 1 rejected the allograft 5 to 8 days after transplantation. Group 2 rejected the allograft (skin and muscle) 30 to 32 days after transplantation (2 days after cessation of immunosuppression). Group 3 rejected the skin portion of the allograft at 50, 52, and 53 days posttransplant. Remaining allograft components (muscle, bone, nerve, vessel) survived indefinitely. Group 4 animals demonstrated significantly prolonged muscle survival beyond 150 days posttransplant; the skin component survived past 150 days in two of three animals. Skin and muscle histology in all long-term surviving animals were normal.

Conclusions

BM cell infusion with 60 million cells per kilogram results in stable levels of microchimerism. The addition of costimulatory blockade (CTLA4lg) prolonged allograft skin survival and overall graft survival. Such targeted immunomodulatory protocols might facilitate immune tolerance and eliminate the need for multidrug immunosuppression to maintain graft survival after vascularized composite allotransplantation.     

Expression of Pancreatic Endocrine Markers by Prolactin-Treated Rat Bone Marrow Mesenchymal Stem Cells

Background

Mesenchymal stem cells (MSCs) are an attractive source for generation of cells with β-cell properties. Previous studies have demonstrated the ability of prolactin to induce an increase in β-cell mass and maturation, which suggests beneficial effects of its use in MSC differentiation protocols.

Objective

To evaluate the expression of endocrine differentiation markers in rat MSCs treated in vitro with prolactin.

Methods

Mesenchymal stem cells from bone marrow of Wistar rats were isolated, expanded, and characterized. Differentiation of MSCs was induced in medium containing 23 mmol/L of glucose, and nicotinamide, 2-mercaptoethanol, and exendin-4, in the presence or absence of 500 ng/mL of rat recombinant prolactin. Expression of endocrine markers and prolactin receptor genes was evaluated using real-time polymerase chain reaction, and compared between culture stages and presence vs absence of prolactin in the culture medium. Expression of insulin, somatostatin, glucagon, and pancreatic and duodenal homeobox 1 was also evaluated at immunofluorescence microscopy.

Results

Isolated cells were mostly MSCs, as confirmed at fluorescent-activated cell sorting and cytochemistry. Pax6, Ngn-3, Isl1, NeuroD1, Nkx2.2, and Nkx6.1 exhibited varied expression during culture stages. The long form of the prolactin receptor messenger RNA was induced in prolactin-treated cultures (P < .05). The somatostatin gene was induced in early stages of differentiation (P < .05), and its expression was induced by prolactin, as confirmed using immunofluorescence.

Conclusion

Culture of rat bone marrow MSCs in differentiation medium induces expression of pancreatic endocrine-specific genes, and somatostatin and prolactin receptor expression was also induced by prolactin.     

Bone Marrow Transplantation Induces Normoglycemia in a Type 2 Diabetes Mellitus Murine Model

Objective

To study the cellular mechanisms involved in the regression of diabetic nephropathy, bone marrow-derived cells must be identified. The aim of this study was to obtain a diabetic chimeric model with bone marrow cells expressing enhanced green fluorecence protein (EGFP), without modifying the course of diabetic nephropathy.

Materials and Methods

Bone marrow transplantation (BMT) was performed in an obese type 2 diabetic murine model (db/db) owing to a mutation in the leptin receptor gene. Whole bone marrow from female donor C57BL/6 EGFP+ mice was transplanted into 8-week-old C57BL/6 mice and into 8- and 24-week-old female C57BLKS (db/db) EGFP− mice. Recipient mice received total body irradiation (TBI) followed by bone marrow (BM) cell infusion. We tested various irradiation doses (Gy) and numbers of BM cells.

Results

When a low TBI dose and a small number of BM cells were administered, only syngeneic C57BL/6 mice became chimeric, whereas allogeneic db/db mice showed rejection. When Gy dose and BM cells were increased, db/db mice became chimeric. However, 8-week-old db/db mice lost the obese phenotype and became normoglycemic, probably due to peripheral BM cell infiltration. Conversely, 24-week-old db/db mice remained obese showing similar blood glucose values, body weights, albuminuria, and glomerular lesions at nontransplanted db/db mice.

Conclusions

Recipient age greatly influenced the peripheral repopulation after BMT in db/db mice. Only the adult chimeric db/db mice seemed to be a good model to study the cellular mechanisms involved in the regression of diabetic nephropathy.     

Expression of Pancreatic Endocrine Markers by Mesenchymal Stem Cells From Human Umbilical Cord Vein

Background

Mesenchymal stem cells (MSCs) from human umbilical cord vein have great potential for use in cell therapy because of their ease of isolation, expansion, and differentiation, in addition to their relative acceptance from the ethical point of view. Obtaining the umbilical cord at birth does not present any risk to either mother or child.

Objective

To isolate and promote in vitro expansion and differentiation of MSCs from human umbilical cord vein into cells with a pancreatic endocrine phenotype.

Methods

Mesenchymal stem cells obtained from human umbilical cord vein via collagenase digestion were characterized at cytochemistry and fluorescent-activated cell sorting, and expanded in vitro. Differentiation of MSCs into an endocrine phenotype was induced using high-glucose (23 mmol/L) medium containing nicotinamide, exendin-4, and 2-mercaptoethanol. Expression of insulin, somatostatin, glucagon, and pancreatic and duodenal homeobox 1 was analyzed using immunofluorescence.

Results

Cells isolated from the umbilical cord vein were MSCs as confirmed at cytochemistry and fluorescent-activated cell sorting. Expression of somatostatin, glucagon, and pancreatic and duodenal homeobox 1 by differentiated cells was demonstrated using immunofluorescence. Insulin was not expressed.

Conclusions

The MSC differentiation protocol used in the present study induced expression of some endocrine markers. Insulin was not produced by these cells, probably because of incomplete induction of differentiation.     

Blockade of inducible costimulator pathway to prevent acute rejection in rat liver transplantation

Background

The role of inducible costimulator (ICOS) in transplantation immunity remains unclear.

Methods

A Lewis-to-Brown-Norway (BN) rat liver transplant model was used to explore the effect of ICOS blockade by small interference RNA. Recipient survival rate, number of CD25/ICOS-positive cells, ICOS mRNA and protein levels, and interferon-γ and tumor-necrosis factor-α levels were determined.

Results

Recipient survival was significantly prolonged in rats treated with RNA interference. On day 7 after transplantation, there was a diminished frequency of CD25/ICOS-positive cells and an increased frequency of apoptotic T cells. Furthermore, we found that ICOS blockade could inhibit mRNA and protein expression of ICOS, decrease plasma levels of interferon-γ and tumor-necrosis factor-α, suppress cell infiltration into grafts, and promote tolerance in the interference group.

Conclusions

Our data demonstrate that RNA interference is a potent tool to down-modulate ICOS expression and protect allografts from acute rejection.     

Mesenchymal Stem Cells Treated With Rat Pancreatic Extract Secrete Cytokines That Improve the Glycometabolism of Diabetic Rats

Background

Mesenchymal stem cells (MSCs) under favorable conditions secrete a spectrum of cytokines that promote the survival of surrounding cells via paracrine mechanisms. We explored the impact of rat pancreatic extract (RPE) on cytokine secretion by MSCs and examined the influence of administration of conditioned media of MSCs treated with RPE on blood glucose levels in diabetic rats.

Methods

Cytokine levels (IGF-1, VEGF, bFGF) in conditioned media of MSCs treated with RPE were measured using enzyme-linked immunosorbent assays. We estimated blood glucose levels of STZ-induced diabetic rats following intraperitoneal injection of conditioned media from RPE-treated MSCs. We analyzed histopathology of pancreatic islets by insulin immunostaining and apoptosis through a TUNEL assay.

Results

Levels of IGF-1, VEGF, and bFGF were significantly increased in RPE-CM compared with control media. Administration of conditioned media of RPE-treated MSCs significantly lowered the blood glucose levels of diabetic rats. After RPE treatment the insulin-positive area was increased and apoptosis of pancreatic beta cells decreased.

Conclusion

RPE enhanced the secretion of cytokines by MSCs. MSCs in the pancreatic microenvironment may exert indirect salutary effects via paracrine mediators on injured pancreatic cells in an STZ-induced diabetic animal model. The secreted factors may exert their therapeutic benefits by preventing apoptosis of pancreatic beta cells.     

Therapeutic implications of mesenchymal stem cells transfected with hepatocyte growth factor transplanted in rat kidney with unilateral ureteral obstruction

Purpose

The purpose of the study was to establish whether bone marrow mesenchymal stem cells (MSCs) transfected with hepatocyte growth factor (HGF) can migrate and localize in the rat's kidney with unilateral ureteral obstruction (UUO) and contribute to repair of renal fibrosis.

Methods

We separated and cultured bone marrow-derived MSCs of male rats in vitro and transfected them with adenovirus-mediated HGF (Ad-HGF). The expression of HGF was measured with enzyme-linked immunosorbent assay. Sixty female rats were sham operated (n = 24) or subjected to left UUO: Ad-HGF-transfected MSCs, uninfected MSCs, or saline was injected into the rat's tail vein. Kidney tissue was collected at the end of the seventh or 14th day after operation. The distribution of Y chromosome in the kidney after Ad-HGF-transfected MSCs transplantation was determined by an in situ hybridization method. As the hallmark of myofibroblasts, α-smooth muscle actin (expression of which significantly increases in the presence of renal fibrosis) was detected by immunohistochemistry in all UUO rats' left kidney tissue.

Results

Y chromosome-positive cells were found only in the obstructed kidney of the transplantation group. The positive cells were mainly distributed in the tubular cells. The average intensity of immunolabeling for α-smooth muscle actin in the transplanted group significantly decreased compared with sham-transplanted group (P < .05), and the expression in the rats injected with uninfected MSCs was higher than that in the rats with MSCs transfected with HGF (P < .05).

Conclusions

Mesenchymal stem cells transfected with HGF can migrate to the rat kidney with UUO and are mainly distributed in the region of renal tubular epithelial cells. The data indicate that MSCs transfected with HGF contribute to a reduction of renal fibrosis after ureteral obstruction and suggest that this may be exploited therapeutically.     

Rapid noninvasive optical imaging of tissue composition in breast tumor margins

Background

In women undergoing breast conserving surgery (BCS), up to 60% can require re-excision. Our objective is to develop an optically based technology which can differentiate benign from malignant breast tissues intraoperatively through differences in tissue composition factors.

Methods

A prospective study of optical imaging of BCS margins is being performed. Optical images are transformed into tissue composition maps with parameters of total hemoglobin concentration, b-carotene concentration and scattering. The predicted outcome is then compared to the margin-level pathology.

Results

Fifty-five margins from 48 patients have undergone assessment. Within 34 specimens with pathologically confirmed positive margins, the ratio map of b-carotene/scattering showed the most significant difference reflecting a decrease in adipose and an increase in cell density within malignant margins (p=.002). These differences were notable in both in-situ and invasive disease.

Conclusions

We present a novel optical spectral imaging device that provides a rapid, non-destructive assay of the tissue composition of breast tumor margins.     

Clinical use of allogeneic bone granulates to reconstruct maxillary and mandibular alveolar processes

Introduction

Lack of adequate mass of a patient's own bone is still a clinical problem in dental implantology; it precludes dental embedment. Surgical widening of an atrophied alveolar process with the use of an allogeneic bone granulate to fill the bone defect constitutes a first-line method to prepare for implant-prosthetic treatment. Transplantation of allogeneic material allows reconstruction of optimal height, thickness, and width of the alveolar process facilitating a procedure with a good long-term outcome. The study assessed outcomes following augmentation of atrophied alveolar processes before intraosseous implantation.

Materials and Methods

Filling bone defects in the maxilla and mandible as an introductory measure for implant-prosthetic treatment was performed in 59 patients (24 females and 35 males of age range 22-65 years). Bone granulate was used for maxillary sinus floor elevation (n = 29), augmentation of the postextraction alveoli (n = 12), and filling of defects in the outer table of the compact bone formed following inflammatory conditions (n = 18). The bone grafts were covered with plasma-rich fibrin (PRF) obtained from the patient's blood to accelerate the formation of synostoses and prevent epithelial penetration between the patients' own bone and the bone graft.

Results

In all of the patients normal union was observed, as confirmed by radiological images as well as intraprocedural assessment. Sufficient height and width as well as thickness of the alveolar process was obtained, which allowed embedment.

Conclusions

Allogeneic bone granulate constitutes a good material to reconstruct maxillary and mandibular alveolar processes in out-patient care.     

Neuroblastoma-derived secretory protein messenger RNA levels correlate with high-risk neuroblastoma

Background/Purpose

In advanced-stage neuroblastoma, bulky disease and systemic dissemination can be controlled with intense surgical and medical therapies; however, recurrence rates are very high in this group indicating that residual disease is rarely eradicated. The need to detect residual disease and predict prognosis is critical to planning appropriate treatment regimens for these patients. Recently, neuroblastoma-derived secretory protein (NDSP) was identified and cloned from neuroblastoma.

Methods

Using quantitative real-time PCR, we tested NDSP messenger RNA (mRNA) expression in 45 neuroblastoma tumor samples and 5 bone marrow samples. Correlation between NDSP expression and age at diagnosis, International Neuroblastoma Staging System, MYCN amplification, and Children's Oncology Group risk stratification was analyzed using Spearman nonparametric correlation.

Results

Neuroblastoma tissue samples show much higher NDSP mRNA levels above control in 43 of 45 samples (96%); moreover, these levels correlate with the Children's Oncology Group neuroblastoma risk group assignment. We also found that bone marrow samples with known tumor infiltration had much higher NDSP mRNA levels than bone marrow from patients without metastasis.

Conclusion

From these data, we conclude that NDSP mRNA levels in neuroblastoma tumor tissue correlate with risk group assignment and may serve as a marker for metastasis in bone marrow.     

Absence of the p53 tumor suppressor gene promotes osteogenesis in mesenchymal stem cells

Objective

Osteosarcoma arises predominantly in the metaphyseal growth plate of children during the growth spurt years. These tumors develop during physiological growth from an expanding cell population, suggesting that the transformed cell is a bone-forming progenitor. An absence of the p53 oncogene has been implicated in the origin and progression of osteosarcoma, and because mesenchymal stem cells (MSCs) are the physiological osteogenic progenitor cell population, we hypothesized that a p53^−/− mutation would enhance bone differentiation of MSC in a mouse model of in vitro osteogenesis.

Methods

Clonal MSC populations were derived from p53^−/− mice. P53^−/− and wild-type cells were placed in osteogenic culture and assessed via Alizarin Red quantification and alkaline phosphatase staining. The osteogenic marker genes Cbfa1, osteopontin, and osteocalcin were assessed by quantitative real time polymerase chain reaction during differentiation.

Results

Bone nodule formation and alkaline phosphatase staining was accelerated and enhanced in the p53^−/− cells. The early and intermediate osteogenic markers, Cbfa1 and osteopontin, were upregulated in p53^−/− MSCs compared with wild-type cells during osteogenesis. The terminal osteogenic marker gene osteocalcin was paradoxically lower in p53^−/− MSCs indicating impaired terminal differentiation.

Conclusion

The p53^−/− mutation enhances and accelerates early osteogenesis in MSCs, but prevents terminal differentiation toward a mature osteocyte phenotype. These findings may have important implications for the regulation of the MSC compartment during the derivation of osteosarcoma in children.     

Treatment of AVN using the induction chamber technique and a biological-based approach: Indications and clinical results

Objective

To determine the efficacy of core decompression (CD) technique combined with recombinant morphogenetic proteins, autologous mesenchymal stem cells (MSCs) and xenograft bone substitute into the necrotic lesion of the femoral head on clinical symptoms and on the progression of osteonecrosis of the femoral head.

Patients and methods

A total of 38 patients (40 hips) with early stage osteonecrosis of the femoral head were studied over a 4-year period.

Results

CD technique combined with recombinant morphogenetic proteins, autologous MSCs and xenograft bone substitute was associated with a significant reduction in both pain and joint symptoms and reduced the incidence of fractural stages. At 36 months, 33 patients achieved clinical and radiographic healing.

Conclusion

This long-term follow-up study confirmed that CD technique combined with recombinant morphogenetic proteins, autologous MSCs and xenograft bone substitute may be an effective treatment for patients with early stage osteonecrosis of the femoral head.     

Pain on injection of propofol: a comparison of methylene blue and lidocaine

Study Objective

To investigate whether methylene blue, given before injection of propofol, was effective in reducing the frequency and severity of pain associated with propofol injection.

Design

Prospective, randomized, double-blinded clinical study.

Setting

Operating room of a university hospital.

Patients

90 adult, ASA physical status 1 and 2 patients undergoing elective surgery.

Interventions

Patients were randomly allocated to one of three groups of 30 patients each. Group I received 50 mg of methylene blue, Group II received 40 mg of lidocaine, and Group III, the control group, was given normal saline. All drugs were given as a 2.0 mL bolus 45 seconds before propofol administration.

Measurements

Injection pain using vocal responses, facial grimacing, arm withdrawal, tears, and questioning of the patient were noted. A 4-point scale was used for documenting pain.

Main Results

Pain frequency was 90% in the saline group, whereas the frequencies were significantly lower in the lidocaine and methylene blue groups (26.7% and 40%, respectively).

Conclusions

Intravenous pretreatment with methylene blue appears to be effective in reducing the pain during propofol injection.     

Imaging of granulomatous and chronic invasive fungal sinusitis: Comparison with allergic fungal sinusitis

Objective

To study the radiological features of chronic/granulomatous invasive fungal sinusitis (IFS) and identify differentiating characteristics, if any, from allergic fungal sinusitis (AFS).

Study design

Prospective radiological study.

Setting

Tertiary hospital in northern India.

Subjects and methods

Subjects were nonacute fungal sinusitis patients with orbital involvement presenting between January 1999 and December 2003. Seventeen IFS and 12 AFS patients with mean age 27 years (range 7-59 years) underwent computed tomographic scan (CT) and magnetic resonance imaging (MRI) of paranasal sinuses with contrast. These were operated within one month of doing the scans and had histologically confirmed fungal sinusitis. Outcome measures were characteristics of opacity produced by the diseased tissue on CT and MRI, side and number of sinuses involved, expansion of sinuses, areas of bone erosion, and extra-sinus extension.

Results

IFS showed homogenous opacity (isodense or hyperdense to muscle tissue) on CT and isointense and hypointense signal on T1- and T2-weighted MR images respectively. IFS showed involvement of one or two sinuses only, homogenous contrast enhancement, lack of expansion of sinuses, and bone erosion localized to the area of extra-sinus extension, and the extra-sinus component of the disease was more than the intra-sinus component. AFS showed heterogenous opacities with hyperattenuation areas on CT, isointense/hypointense to signal void on T1- and T2-weighted MR images. Expansion of sinuses, extensive bone erosion, lack of contrast enhancement, multiple sinus involvement, and major bulk of disease being intra-sinus rather than extra-sinus were other characteristics of AFS.

Conclusion

Radiological features of IFS are described that are different from AFS.     

Intraoperative myocardial acidosis as a risk for hospital readmission after cardiac surgery

Background

This study elucidates the relationship between intraoperative myocardial acidosis/ischemia and the risk of unplanned hospital readmissions within 30 days and 6 months after cardiac surgery.

Methods

Myocardial tissue pH (corrected to 37°C: pH_37C) was monitored in 221 patients during cardiac surgery. Regional myocardial acidosis was defined in terms of specific pH thresholds.

Results

Fourteen percent and 27% of the patients were readmitted within 30 days and 6 months postoperatively, respectively. The mean number of readmissions was 1.67 ± 1.24; pH_37C <6.85 at the end of cardiopulmonary bypass (CPB) was identified as the threshold most significantly associated with readmission. This threshold was associated with a 6-fold increased risk of readmission within 30 days and a 5-fold increased risk within 6 months.

Conclusions

Persistent regional myocardial acidosis after weaning from CPB independently determines unplanned readmission rates up to 6 months postoperatively. This study underscores the importance of avoiding myocardial tissue acidosis during cardiac surgery.