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Iron has been emerging as a key contributor to aging-associated, chronic disorders due to the propensity for generating reactive oxygen species. To date, there are a limited number of publications exploring the role of iron in the pathogenesis of primary/age-related osteoarthritis (OA). The objective of this study was to determine whether reduced iron via pharmacologic iron chelation with deferoxamine (DFO) affected the development and/or severity of cartilage lesions in a primary OA model. At 12-weeks-of-age, 15 male Dunkin-Hartley guinea pigs received either 46 mg/kg DFO (n = 8) or vehicle control (n = 7) injected subcutaneously twice daily for five days each week. Movement changes, captured via overhead enclosure monitoring, were also determined. Termination occurred at 30-weeks-of-age. Iron was quantified in serum, urine, liver, and femoral head articular cartilage. Left knees were evaluated for: structural changes using histopathology guidelines; and immunohistochemistry. Gene expression analysis was conducted on right knee articular cartilage. DFO reduced iron levels in femoral head articular cartilage (p = 0.0006) and liver (p = 0.02), and increased iron within urine (p = 0.04) and serum (p = 0.0009). Mobility of control animals declined, while the DFO group maintained activity levels similar to the first month of treatment (p = 0.05). OA-associated cartilage lesions were reduced in knees of DFO animals (p = 0.0001), with chondrocyte hypocellularity a key histologic difference between groups (p 0.0001). DFO-receiving animals had increased immunostaining for phosphorylated adenosine monophosphate activated protein kinase alpha within knee articular cartilage; lower transcript counts of several proapoptotic genes (p = 0.04-0.0004) and matrix-degrading enzymes (p = 0.02-0.0001), and increased expression of the anti-apoptotic gene Bcl-2 (p 0.0001) and a tissue inhibitor of matrix-metalloproteinases (p = 0.03) were also observed. These results suggest that iron chelation delayed the progression of primary OA in an animal model and could hold potential as a translational intervention. These findings provide expanded insight into factors that may contribute to the pathogenesis of primary OA.

Background: The infrapatellar fat pad (IFP) is the largest adipose deposit in the knee; however, its contributions to the homeostasis of this organ remain undefined. To determine the influence of IFP on joint health, this study evaluated the progression of osteoarthritis (OA) following excision of the IFP in a rodent model of naturally-occurring disease. Methods: Male Dunkin-Hartley guinea pigs (n=18) received surgical removal of the IFP in one knee at 3 months of age; contralateral knees received sham surgery as matched internal controls. Mobility and gait assessments were performed prior to IFP removal and monthly thereafter. Animals were harvested at 7 months of age. Ten set of these knees were processed for microcomputed tomography (microCT), histopathology, transcript expression analyses, and immunohistochemistry (IHC); 8 sets of knees were dedicated to microCT and biomechanical testing (material properties of knee joints tissues and anterior drawer laxity). Results: Fibrous connective tissue (FCT) developed in place of the native adipose depot. Gait demonstrated no significant differences between IFP removal and contralateral hindlimbs. MicroCT OA scores were improved in knees containing the FCT. Quantitatively, IFP-containing knees had more osteophyte development and increased trabecular volume bone mineral density (vBMD) in femora and tibiae. Histopathology confirmed maintenance of articular cartilage structure, proteoglycan content, and chondrocyte cellularity in FCT-containing knees. Transcript analyses revealed decreased expression of adipose-related molecules and select inflammatory mediators in FCTs compared to IFPs. This was verified via IHC for inflammatory mediators. The medial articular cartilage in knees with native IFPs showed an increase in equilibrium modulus, which correlated with increased amounts of magnesium and phosphorus. Discussion/Conclusion: Formation of the FCT resulted in reduced OA-associated changes in both bone and cartilage. This benefit may be associated with: a decrease in inflammatory mediators at transcript and protein levels; and/or improved biomechanical properties. Thus, the IFP may play a role in the pathogenesis of knee OA in this strain, with removal prior to disease onset appearing to have short-term benefits.

Summary Objective Iron is emerging as a key player in aging-associated diseases due to its propensity for driving free radical formation. Studies examining the role of iron in the pathogenesis of primary osteoarthritis (OA) are limited. Our objective was to establish a direct relationship between excess iron and OA by administering iron dextran to a guinea pig strain with decreased propensity for developing this disease. Design Twenty, 12-week-old Strain 13 guinea pigs received either iron dextran or dextran control intraperitoneally once weekly for 4 weeks; termination occurred at 16 weeks of age. Iron levels were determined systemically (serum and liver) and within diarthrodial joints [femoral head articular cartilage and infrapatellar fat pads (IFPs) of knee joints]. One knee was collected to score structural changes associated with OA via microcomputed tomography (microCT) and histology using published grading schemes. Articular cartilage and IFPs were harvested from contralateral knees for gene expression analyses. Results Iron overload was confirmed systemically via increased serum iron and liver iron concentration. Articular cartilage and IFPs in the iron dextran group also had higher levels of iron. Excess iron worsened knee OA using both microCT and histologic scoring systems. Gene analyses revealed that exogenous iron altered the expression of iron trafficking proteins, select cytokines, and structural components of cartilage. Conclusion These results demonstrate that systemic iron overload caused cellular iron accumulation in the knee joint. This excess iron is associated with increased expression of local inflammatory mediators and early onset and progression of knee joint OA in Strain 13 animals.

BackgroundThe infrapatellar fat pad (IFP) is the largest adipose deposit in the knee; however, its contributions to the homeostasis of this organ remain unknown. To determine the influence of this depot on joint health, this study determined the progression of osteoarthritis (OA) following excision of the IFP in a rodent model of naturally-occurring disease.MethodsMale Dunkin-Hartley guinea pigs (n=10) received surgical removal of the IFP in one knee at 3 months of age; contralateral knees received sham surgery as matched internal controls. Treadmill-based gait analysis was performed prior to IFP removal and monthly thereafter. Animals were harvested at 7 months of age. Both knees were processed for microcomputed tomography (microCT), histopathology, transcript expression analyses, and immunohistochemistry (IHC).ResultsFibrous connective tissue (FCT) developed in place of the native fat pad. Gait demonstrated no significant differences between IFP removal and contralateral limbs. MicroCT OA scores were improved in knees with the FCT. Histopathology confirmed maintenance of articular cartilage structure, proteoglycan content, and chondrocyte cellularity in FCT-containing knees. Transcript analyses revealed decreased expression of adipose-related molecules and inflammatory mediators in FCTs compared to IFPs. This was corroborated via IHC for select inflammatory mediators.Discussion/ConclusionFormation of the FCT resulted in reduced OA-associated changes in both bone and cartilage. A decrease in inflammatory mediators at transcript and protein levels may be associated with these improvements. The IFP may therefore play a role in the pathogenesis of knee OA in this strain, with removal prior to disease onset appearing to have short-term benefits.

There is potential discrepancy between human and laboratory animal studies of osteoarthritis (OA), as radiographic assessment is the hallmark of the former and histopathology the standard for the latter. This suggests a need to evaluate OA in animal models in a manner similar to that utilized in people. Our study aimed to develop a whole joint grading scheme for microcomputed tomography (microCT) images in Hartley guinea pigs, a strain that recapitulates joint changes highlighted in human spontaneous OA.Knees from animals aged 2, 3, 5, 9, and 15 months were evaluated via whole joint microCT and standard histologic scoring. Quantitative microCT parameters, such as bone volume/total volume were also collected.Both whole joint microCT and histologic scores increased with advancing age and showed strong correlation (r = 0.89. p 0.0001). Histologic scores, which focus on cartilage changes, increased progressively with age. Whole joint microCT scores, which characterize bony changes, followed a stepwise pattern: scores increased between 3 and 5 months of age, stayed consistent between 5 and 9 months, and worsened again between 9 and 15 months.This work provides data that advocates the use of a whole joint microCT scoring system in guinea pig studies of OA, as it provides important information regarding bony changes that occur at a different rate than articular cartilage changes. This grading scheme, in conjunction with histology and quantitative microCT measurements, may enhance the translational value of this animal model as it pertains to human work.

Iron, particularly hemosiderin, is a commonly observed pigment in cytology. Many pigments appear green to blue to black, making differentiation of pigment types difficult. While cytologic clues such as erythrophagia can help determine whether pigment is iron, Perl's Prussian Blue stain is used to highlight iron when these clues are not present. Other special stains can identify similar pigments such as copper. Identification of pigments is important as it directs cytologic interpretation, thus directly influencing patient diagnosis. This paper also presents basic iron metabolism, iron disorders in small animals, and laboratory assessment of iron disorders.

Background True and functional iron deficiency can result in anemia. Current tests to assess iron status often do not allow differentiation between these entities, which can affect optimal treatment. Previous work suggested low reticulocyte hemoglobin content (CHr) may be an early indicator of iron deficiency. Objective This study aimed to correlate several inflammation markers with CHr values in dogs. We hypothesize that dogs with low CHr values have hematologic and biochemical evidence of inflammation. Methods Animals with CHr values below the reference interval were included in the low CHr group, while dogs with normal or increased CHr were included in the control group. HCT, MCV, CHr, reticulocyte mean cell volume (MCVr), concentrations of serum iron, C-reactive protein (CRP), ferritin, and ceruloplasmin, and total iron-binding capacity (TIBC), percent transferrin saturation (% sat), and total WBC, neutrophil, and monocyte counts were determined. Nonparametric tests were performed; median values and percentage of abnormalities between each group were compared. Results Relative to control dogs, animals in the low CHr group had higher median values for CRP, ferritin, ceruloplasmin, and WBC concentration (P ≤ .05), and lower median values for HCT and MCV (P ≤ .0001). Higher frequencies of abnormalities for CRP, ferritin, WBC, neutrophil, and monocyte concentrations (P ≤ .02) were present in the low CHr group. Conclusions Dogs with low CHr values often have evidence of inflammation, but low CHr did not reliably predict Fe deficiency. Additional diagnostic tests are needed to differentiate true and functional iron deficiency.

Background Obesity is a global disease, affecting nearly half a billion people. Unfortunately, this trend is mirrored in our canine population. Objectives As obesity is a complex inflammatory disease, there is a need to determine whether routine medical screening tests may indicate, or be influenced by, its presence. The objective of the current study was to determine if significant differences exist between CBC and biochemical profile values from control vs overweight/obese, client-owned dogs considered clinically healthy. Methods Dogs presented for routine health examinations, including minor dental or elective surgical procedures, were retrospectively identified from a hospital population. Animals were allocated to 2 categories based on body condition score (BCS), and data were analyzed by Mann–Whitney nonparametric analysis with statistical significance at a P ≤ .05. Results After exclusions, 116 dogs were assigned to the overweight/obese group (BCS ≥ 7) and 240 dogs to the control group (BCS = 4–6). Overweight/obese dogs had higher total leukocyte counts and higher plasma protein and globulin concentrations. Other differences were attributed to decreased serum water fraction (increased sodium, albumin, calcium, and anion gap) in the overweight/obese group. Interestingly, chloride concentration was decreased (in the face of increased sodium) in the obese group. Conclusions There is CBC and biochemical evidence to support the concern that obesity influences laboratory values, even in dogs considered clinically healthy. Prospective studies aimed at characterizing these changes are needed to provide insight into the connection between obesity and its comorbidities.

Background Effects of aging on hematologic and biochemical variables are well described in people. Anemia of the elderly is attributed to iron deficiency, anemia of chronic disease, chronic kidney disease, myelodysplasia, or idiopathic causes. Limited studies have examined these variables in aging dogs, but they have typically examined single breeds in research settings. Objective The objective of this study was to identify differences in CBC and biochemistry values between adult and aged dogs of many breeds. Methods Dogs presenting for wellness examinations and minor dental/elective surgeries that were otherwise clinically healthy were retrospectively identified. Dogs were categorized by age: adult (1–7.9 years), senior (8–11.9 years), and geriatric (12+ years). Standard CBC and biochemistry data were collated. Asian breeds, Greyhounds, and dogs with data indicating overt underlying disease were excluded. The Kruskal–Wallis test was used to compare groups with statistical significance set at P ≤ .05. Results Hematocrit, MCV, and serum iron decreased with age, indicating possible iron-restricted erythropoiesis (IRE), due to iron deficiency or low-grade chronic inflammation. Total proteins, globulins, and platelet counts increased with age while albumin decreased, suggesting low-grade inflammation. Urea was increased in older dogs without a concurrent increase in creatinine, which points toward gastrointestinal bleeding or dehydration. Conclusion Clinically healthy, aging dogs have changes in laboratory variables that indicate altered physiologies compared to younger adult animals, including evidence of IRE, inflammation, and potential gastrointestinal bleeding, suggesting a similar trend to that of elderly human beings. Future studies will examine markers of iron metabolism and inflammation in aging dogs.

Iron, particularly hemosiderin, is a commonly observed pigment in cytology. Many pigments appear green to blue to black, making differentiation of pigment types difficult. While cytologic clues such as erythrophagia can help determine whether pigment is iron, Perl's Prussian Blue stain is used to highlight iron when these clues are not present. Other special stains can identify similar pigments such as copper. Identification of pigments is important as it directs cytologic interpretation, thus directly influencing patient diagnosis. This paper also presents basic iron metabolism, iron disorders in small animals, and laboratory assessment of iron disorders.

Osteoarthritis (OA) is a debilitating condition characterized by inflammation, breakdown, and consequent loss of cartilage of the joints. Epidemiological studies indicate obesity is an important risk factor involved in OA initiation and progression. Traditional views propose OA to be a biomechanical consequence of excess weight on weight-bearing joints; however, emerging data demonstrates that systemic and local factors released from white adipose depots play a role. Hence, current views characterize OA as a condition exacerbated by a metabolic link related to adipose tissue, and not solely related to redistributed/altered weight load. Factors demonstrated to influence cartilage and bone homeostasis include adipocyte-derived hormones (“adipokines”) and adipose depot released cytokines. Epidemiological studies demonstrate a positive relation between systemic circulating cytokines, leptin, and resistin with OA types, while the association with adiponectin is controversial. Local factors in joints have also been shown to play a role in OA. In particular, this includes the knee, a weight-bearing joint that encloses a relatively large adipose depot, the infrapatellar fat pad (IFP), which serves as a source of local inflammatory factors. This review summarizes the relation of obesity and OA as it specifically relates to the IFP and other integral supporting structures. Overall, studies support the concept that metabolic effects associated with systemic obesity also extend to the IFP, which promotes inflammation, pain, and cartilage destruction within the local knee joint environment, thus contributing to development and progression of OA.