Natural genetic variation in Stim1 creates stroke in the spontaneously hypertensive rat.

Similar to humans, the risk of cerebrovascular disease in stroke-prone spontaneously hypertensive rats (SHR-A3/SHRSP) arises from naturally occurring genetic variation. In the present study, we show the involvement of genetic variation affecting the store-operated calcium signaling gene, Stim1, in the pathogenesis of stroke in SHR. Stim1 is a key lymphocyte activation signaling molecule and contains functional variation in SHR-A3 that diverges from stroke-resistant SHR-B2. We created a SHR-A3 congenic line in which Stim1 was substituted with the corresponding genomic segment from SHR-B2. Compared with SHR-A3 rats, Stim1 congenic SHR-A3 (SHR-A3(Stim1-B2)) have reduced cerebrovascular disease in response to salt loading including lower neurological deficit scores and cerebral edema. Microbleeds and major hemorrhages occurred in over half of SHR-A3 rats. These lesions were absent in SHR-A3(Stim1-B2) rats. Loss of Stim1 function in mice and humans is associated with antibody-mediated autoimmunity due to defects in T lymphocyte helper function to B cells. We investigated autoantibody formation using a high-density protein array to detect the presence of IgG and IgM autoantibodies in SHR-A3. Autoantibodies to key cerebrovascular stress proteins were detected that were reduced in the congenic line.

Germ-line genetic variation in the immunoglobulin heavy chain creates stroke susceptibility in the spontaneously hypertensive rat.

The risk of cerebrovascular disease in stroke-prone spontaneously hypertensive rats (SHR-A3/SHRSP) arises from naturally occurring genetic variation. In the present study we show the involvement of SHR genetic variation that affects antibody formation and function in the pathogenesis of stroke. We have tested the involvement in susceptibility to stroke of genetic variation in IgH, the gene encoding the immunoglobulin heavy chain by congenic substitution. This gene contains functional natural variation in SHR-A3 that diverges from stroke-resistant SHR-B2. We created a SHR-A3 congenic line in which the IgH gene was substituted with the corresponding haplotype from SHR-B2. Compared with SHR-A3 rats, congenic substitution of the IgH locus [SHR-A3(IgH-B2)] markedly reduced cerebrovascular disease. Given the role in antibody formation of the IgH gene, we investigated the presence of IgG and IgM autoantibodies and their targets using a high-density protein array containing ~20,000 recombinant proteins. High titers of autoantibodies to key cerebrovascular stress proteins were detected, including FABP4, HSP70, and Wnt signaling proteins. Serum levels of these autoantibodies were reduced in the SHR-A3(IgH-B2) congenic line.

Renal inflammation and injury are associated with lymphangiogenesis in hypertension.

Lymphatic vessels are vital for the trafficking of immune cells from the interstitium to draining lymph nodes during inflammation. Hypertension is associated with renal infiltration of activated immune cells and inflammation; however, it is unknown how renal lymphatic vessels change in hypertension. We hypothesized that renal macrophage infiltration and inflammation would cause increased lymphatic vessel density in hypertensive rats. Spontaneously hypertensive rats (SHR) that exhibit hypertension and renal injury (SHR-A3 strain) had significantly increased renal lymphatic vessel density and macrophages at 40 wk of age compared with Wistar-Kyoto (WKY) controls. SHR rats that exhibit hypertension but minimal renal injury (SHR-B2 strain) had significantly less renal lymphatic vessel density compared with WKY rats. The signals for lymphangiogenesis, VEGF-C and its receptor VEGF-R3, and proinflammatory cytokine genes increased significantly in the kidneys of SHR-A3 rats but not in SHR-B2 rats. Fischer 344 rats exhibit normal blood pressure but develop renal injury as they age. Kidneys from 24-mo- and/or 20-mo-old Fischer rats had significantly increased lymphatic vessel density, macrophage infiltration, VEGF-C and VEGF-R3 expression, and proinflammatory cytokine gene expression compared with 4-mo-old controls. These data together demonstrate that renal immune cell infiltration and inflammation cause lymphangiogenesis in hypertension- and aging-associated renal injury.

Return to play and performance after patellar fracture in American professional sports: a case-control cohort analysis.

OBJECTIVES: This study describes the effects of patellar fracture on return to play (RTP) and functional outcomes among athletes in American professional sports. METHODS: Professional athletes from the National Football League (NFL), National Basketball Association (NBA), Major League Baseball (MLB), and National Hockey League (NHL) who suffered a patellar fracture between January 1965 and December 2021 were identified through injury reports and public archives. Performance scores, play time, and games played were collected for the season preceding patellar fracture and 2 seasons after RTP, and differences in recorded metrics compared to pre-injury levels and matched controls were analyzed. RESULTS: Twenty-nine of 41 (71%) injured athletes returned to play at an average of 217 days. Among all players, play volume decreased in year 1 compared to baseline but recovered to pre-injury levels in year 2. Athletes treated operatively experienced an initial decline in performance (p < 0.01) but recovered to pre-injury performance level in year 2. Nonoperative management resulted in a decline in performance in year 2 of RTP (p = 0.02). Athletes treated operatively performed significantly worse than matched controls in year 1 of RTP (64% vs. 99%; p = 0.04) but recovered to a similar level of performance as controls in year 2 (87% vs. 91%; p = 0.90). CONCLUSION: A 71% rate of RTP was demonstrated among this limited cohort of 29 athletes in American professional sports after isolated patellar fracture. Although details regarding fracture characteristics and operative reports were not available for analysis, operative management was not associated with longer absence from play compared to nonoperative treatment. Despite the limitations of this study, the findings suggesting operative management may improve prospects of maintaining elite performance following RTP warrant further investigation. LEVEL OF EVIDENCE: Case-control cohort analysis; Level of evidence, 3.

Stim1 Polymorphism Disrupts Immune Signaling and Creates Renal Injury in Hypertension.

Background Spontaneously hypertensive rats of the stroke-prone line (SHR-A3) develop hypertensive renal disease as a result of naturally occurring genetic variation. Our prior work identified a single-nucleotide polymorphism unique to SHR-A3 that results in truncation of the carboxy terminus of STIM1. The SHR-B2 line, which is also hypertensive but resists hypertensive renal injury, expresses the wild-type STIM1. STIM1 plays a central role in lymphocyte calcium signaling that directs immune effector responses. Here we show that major defects in lymphocyte function affecting calcium signaling, nuclear factor of activated T cells activation, cytokine production, proliferation, apoptosis, and regulatory T-cell development are present in SHR-A3 and attributable to STIM1. Methods and Results To assess the role of Stim1 variation in susceptibility to hypertensive renal injury, we created a Stim1 congenic line, SHR-A3(Stim1-B2), and STIM1 function was rescued in SHR-A3. We found that Stim1 gene rescue restores disturbed lymphocyte function in SHR-A3. Hypertensive renal injury was compared in SHR-A3 and the SHR-A3(Stim1-B2) congenic line. Histologically assessed renal injury was markedly reduced in SHR-A3(Stim1-B2), as were renal injury biomarker levels measured in urine. Stim1 deficiency has been linked to the emergence of antibody-mediated autoimmunity. Renal glomerular immunoglobulin deposition was greater in SHR-A3 than SHR-B2 and was reduced by Stim1 congenic substitution. Serum anti-double-stranded DNA antibody titers in SHR-A3 were elevated compared with SHR-B2 and were reduced in SHR-A3(Stim1-B2). Conclusions Stim1 deficiency in lymphocyte function originating from Stim1 truncation in SHR-A3 combines with hypertension to create end organ disease and may do so as a result of antibody formation.

Susceptibility to Hypertensive Renal Disease in the Spontaneously Hypertensive Rat Is Influenced by 2 Loci Affecting Blood Pressure and Immunoglobulin Repertoire.

High blood pressure exerts its deleterious effects on health largely through acceleration of end-organ diseases. Among these, progressive loss of renal function is particularly important, not only for the direct consequences of kidney damage but also because loss of renal function is associated with amplification of other adverse cardiovascular outcomes. Genetic susceptibility to hypertension and associated end-organ disease is non-Mendelian in both humans and in a rodent model, the spontaneously hypertensive rat (SHR). Here, we report that hypertensive end-organ disease in the inbred SHR-A3 line is attributable to genetic variation in the immunoglobulin heavy chain on chromosome 6. This variation coexists with variation in a 10 Mb block on chromosome 17 that contains genetic variation in 2 genes involved in immunoglobulin Fc receptor signaling. Substitution of these genomic regions into the SHR-A3 genome from the closely related, but injury-resistant, SHR-B2 line normalizes both biomarker and histological measures of renal injury. Our findings indicate that genetic variation leads to a contribution by immune mechanisms hypertensive end-organ injury and that, in this rat model, disease is influenced by differences in germ line antibody repertoire.