Genetic background variation impacts microglial heterogeneity and disease progression in amyotrophic lateral sclerosis model mice.

Recent single-cell analyses have revealed the complexity of microglial heterogeneity in brain development, aging, and neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). Disease-associated microglia (DAMs) have been identified in ALS mice model, but their role in ALS pathology remains unclear. The effect of genetic background variations on microglial heterogeneity and functions remains unknown. Herein, we established and analyzed two mice models of ALS with distinct genetic backgrounds of C57BL/6 and BALB/c. We observed that the change in genetic background from C57BL/6 to BALB/c affected microglial heterogeneity and ALS pathology and its progression, likely due to the defective induction of neurotrophic factor-secreting DAMs and impaired microglial survival. Single-cell analyses of ALS mice revealed new markers for each microglial subtype and a possible association between microglial heterogeneity and systemic immune environments. Thus, we highlighted the role of microglia in ALS pathology and importance of genetic background variations in modulating microglial functions.

Dimethyl fumarate improves cognitive impairment and neuroinflammation in mice with Alzheimer's disease.

BACKGROUND: Neuroinflammation substantially contributes to the pathology of Alzheimer's disease (AD), the most common form of dementia. Studies have reported that nuclear factor erythroid 2-related factor 2 (Nrf2) attenuates neuroinflammation in the mouse models of neurodegenerative diseases, however, the detailed mechanism remains unclear. METHODS: The effects of dimethyl fumarate (DMF), a clinically used drug to activate the Nrf2 pathway, on neuroinflammation were analyzed in primary astrocytes and AppNL-G-F (App-KI) mice. The cognitive function and behavior of DMF-administrated App-KI mice were evaluated. For the gene expression analysis, microglia and astrocytes were directly isolated from the mouse cerebral cortex by magnetic-activated cell sorting, followed by quantitative PCR. RESULTS: DMF treatment activated some Nrf2 target genes and inhibited the expression of proinflammatory markers in primary astrocytes. Moreover, chronic oral administration of DMF attenuated neuroinflammation, particularly in astrocytes, and reversed cognitive dysfunction presumably by activating the Nrf2-dependent pathway in App-KI mice. Furthermore, DMF administration inhibited the expression of STAT3/C3 and C3 receptor in astrocytes and microglia isolated from App-KI mice, respectively, suggesting that the astrocyte-microglia crosstalk is involved in neuroinflammation in mice with AD. CONCLUSION: The activation of astrocytic Nrf2 signaling confers neuroprotection in mice with AD by controlling neuroinflammation, particularly by regulating astrocytic C3-STAT3 signaling. Furthermore, our study has implications for the repositioning of DMF as a drug for AD treatment.

Mitochondria-associated membrane collapse impairs TBK1-mediated proteostatic stress response in ALS.

The organelle contact site of the endoplasmic reticulum and mitochondria, known as the mitochondria-associated membrane (MAM), is a multifunctional microdomain in cellular homeostasis. We previously reported that MAM disruption is a common pathological feature in amyotrophic lateral sclerosis (ALS); however, the precise role of MAM in ALS was uncovered. Here, we show that the MAM is essential for TANK-binding kinase 1 (TBK1) activation under proteostatic stress conditions. A MAM-specific E3 ubiquitin ligase, autocrine motility factor receptor, ubiquitinated nascent proteins to activate TBK1 at the MAM, which results in ribosomal protein degradation. MAM or TBK1 deficiency under proteostatic stress conditions resulted in increased cellular vulnerability in vitro and motor impairment in vivo. Thus, MAM disruption exacerbates proteostatic stress via TBK1 inactivation in ALS. Our study has revealed a proteostatic mechanism mediated by the MAM-TBK1 axis, highlighting the physiological importance of the organelle contact sites.

Monomerization of TDP-43 is a key determinant for inducing TDP-43 pathology in amyotrophic lateral sclerosis.

The cytoplasmic aggregation of TAR DNA binding protein-43 (TDP-43), also known as TDP-43 pathology, is the pathological hallmark of amyotrophic lateral sclerosis (ALS). However, the mechanism underlying TDP-43 cytoplasmic mislocalization and subsequent aggregation remains unclear. Here, we show that TDP-43 dimerization/multimerization is impaired in the postmortem brains and spinal cords of patients with sporadic ALS and that N-terminal dimerization-deficient TDP-43 consists of pathological inclusion bodies in ALS motor neurons. Expression of N-terminal dimerization-deficient mutant TDP-43 in Neuro2a cells and induced pluripotent stem cell-derived motor neurons recapitulates TDP-43 pathology, such as Nxf1-dependent cytoplasmic mislocalization and aggregate formation, which induces seeding effects. Furthermore, TDP-DiLuc, a bimolecular luminescence complementation reporter assay, could detect decreased N-terminal dimerization of TDP-43 before TDP-43 pathological changes caused by the transcription inhibition linked to aberrant RNA metabolism in ALS. These findings identified TDP-43 monomerization as a critical determinant inducing TDP-43 pathology in ALS.

A Surgical Technique for Anterior Cruciate Ligament Reconstruction Using Semitendinosus Graft: An All-Inside Transfemoral Approach.

Given the paucity of reports on all-inside reconstruction procedures via the transfemoral approach, we describe a minimally invasive, all-inside transfemoral technique that enables creating femoral and tibial sockets from the intra-articular cavity. Our transfemoral approach makes it possible to sequentially create femoral and tibial sockets using the same reamer bit, while a single drilling guide is set in place. Our custom socket drilling guide was designed to integrate with a tibial tunnel guide, which helped locate the tunnel exit at an anatomically acceptable location. The advantages of this method include easy and precise positioning of the femoral tunnel, narrow tibial tunnel, minimal damage to the intramedullary trabecular bone integrity, and low postoperative risks of pain, bleeding, and infections.

Excellent short-term results of dome-shaped high tibial osteotomy combined with all-inside anterior cruciate ligament reconstruction.

PURPOSE: This study aimed to evaluate short-term outcomes at least 2 years after dome-shaped high tibial osteotomy (HTO) combined with all-inside anterior cruciate ligament reconstruction (ACL) in patients with persistent ACL insufficiency accompanied by pain due to varus deformity. METHODS: The study enrolled 19 knees of 18 patients. The mean age was 58.4 ± 13.4 years and the mean postoperative follow-up period was 31.4 ± 6.6 months (24-49 months). JOA(Japanese Orthopaedic Association)-OA(osteoarthritis) score, Lysholm score, radiographic outcomes such as femoro-tibia angle (FTA) in a standing position, side-to-side difference in KT-1000 measurements were evaluated at pre op. and post operative final follow up. And arthroscopic evaluation was evaluated at the time of the HTO plate-removal procedure. RESULTS: Before surgery, the mean JOA-OA score was 65.0 ± 13.5, the mean Lysholm score was 47.2 ± 16.2, the mean femoro-tibia angle (FTA) in a standing position was 183.8 ± 3.4° (range;180-190°), and the mean side-to-side difference in KT-1000 measurements was 4.1 ± 1.3 mm. After surgery, the mean JOA-OA score, Lysholm score, and side-to-side difference in KT-1000 measurements improved to 93.1 ± 6.0 (P < 0.00001), 94.2 ± 5.9 (P < 0.00001), and -0.2 ± 0.8 mm (P < 0.00001), respectively. The mean FTA decreased to 168.0 ± 3.3 (P < 0.00001), and the mean posterior tibial slope angle decreased to 5.0 ± 3.6° from 6.9 ± 2.6° preoperatively (P = 0.024). Arthroscopic evaluation during the HTO plate-removal procedure of 17 knees were performed at a mean of 16 months after the surgery. The reconstructed ACL graft in 13 knees were successful, a cyclops lesion in one knee, and looseness of the graft in three knees. CONCLUSIONS: Dome-shaped HTO allows for a relatively high degree of varus correction and decreases the steep posterior tibial slope that causes excessive load on the ACL. Therefore, its use in combination with ACL reconstruction seems to be effective.

Intrinsic structural vulnerability in the hydrophobic core induces species-specific aggregation of canine SOD1 with degenerative myelopathy-linked E40K mutation.

Canine degenerative myelopathy (DM), a fatal neurodegenerative disease in dogs, shares clinical and genetic features with amyotrophic lateral sclerosis, a human motor neuron disease. Mutations in the SOD1 gene encoding Cu/Zn superoxide dismutase (SOD1) cause canine DM and a subset of inherited human amyotrophic lateral sclerosis. The most frequent DM causative mutation is homozygous E40K mutation, which induces the aggregation of canine SOD1 but not of human SOD1. However, the mechanism through which canine E40K mutation induces species-specific aggregation of SOD1 remains unknown. By screening human/canine chimeric SOD1s, we identified that the humanized mutation of the 117th residue (M117L), encoded by exon 4, significantly reduced aggregation propensity of canine SOD1E40K. Conversely, introducing a mutation of leucine 117 to methionine, a residue homologous to canine, promoted E40K-dependent aggregation in human SOD1. M117L mutation improved protein stability and reduced cytotoxicity of canine SOD1E40K. Furthermore, crystal structural analysis of canine SOD1 proteins revealed that M117L increased the packing within the hydrophobic core of the ß-barrel structure, contributing to the increased protein stability. Our findings indicate that the structural vulnerability derived intrinsically from Met 117 in the hydrophobic core of the ß-barrel structure induces E40K-dependent species-specific aggregation in canine SOD1.

Microanatomical organization of hepatic venous lymphatic system in humans.

Lymphatic fluid drains from the liver via the periportal lymphatic, hepatic venous lymphatic, and superficial lymphatic systems. We performed a postmortem study to clarify the three-dimensional structure and flow dynamics of the human hepatic venous lymphatic system, as it still remains unclear. Livers were excised whole from three human cadavers, injected with India ink, and sliced into 1-cm sections from which veins were harvested. The distribution of lymphatic vessels was observed in 5 µm sections immunostained for lymphatic and vascular markers (podoplanin and CD31, respectively) using light microscopy. Continuity and density of lymphatic vessel distribution were assessed in en-face whole-mount preparations of veins using stereomicroscopy. The structure of the external hepatic vein wall was assessed with scanning electron microscopy (SEM). The lymphatic dynamics study suggested that lymphatic fluid flows through an extravascular pathway around the central and sublobular veins. A lymphatic vessel network originates in the wall of sublobular veins, with a diameter greater than 110 µm, and the peripheral portions of hepatic veins and continues to the inferior vena cava. The density distribution of lymphatic vessels is smallest in the peripheral portion of the hepatic vein (0.03%) and increases to the proximal portion (0.22%, p = 0.012) and the main trunk (1.01%, p < 0.001), correlating positively with increasing hepatic vein diameter (Rs = 0.67, p < 0.001). We revealed the three-dimensional structure of the human hepatic venous lymphatic system. The results could improve the understanding of lymphatic physiology and liver pathology.

Sigma-1 receptor maintains ATAD3A as a monomer to inhibit mitochondrial fragmentation at the mitochondria-associated membrane in amyotrophic lateral sclerosis.

Organelle contact sites are multifunctional platforms for maintaining cellular homeostasis. Alternations of the mitochondria-associated membranes (MAM), one of the organelle contact sites where the endoplasmic reticulum (ER) is tethered to the mitochondria, have been involved in the pathogenesis of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). However, the detailed mechanisms through which MAM integrity is disrupted in ALS have not been fully elucidated. Here, we examined whether AAA ATPase domain-containing protein 3A (ATAD3A), a mitochondrial membrane AAA ATPase accumulating at the MAM, is involved in ALS. We found that sigma-1 receptor (σ1R), an ER-resident MAM protein causative for inherited juvenile ALS, required ATAD3A to maintain the MAM. In addition, σ1R retained ATAD3A as a monomer, which is associated with an inhibition of mitochondrial fragmentation. ATAD3A dimerization and mitochondrial fragmentation were significantly induced in σ1R-deficient or SOD1-linked ALS mouse spinal cords. Overall, these observations indicate that MAM induction by σ1R depends on ATAD3A and that σ1R maintains ATAD3A as a monomer to inhibit mitochondrial fragmentation. Our findings suggest that targeting σ1R-ATAD3A axis would be promising for a novel therapeutic strategy to treat mitochondrial dysfunction in neurological disorders, including ALS.

How to improve the clinical outcome of round spermatid injection (ROSI) into the oocyte: Correction of epigenetic abnormalities.

Background: First successful human round spermatid injection (ROSI) was conducted by Tesarik et al. in 1996 for the sole treatment of nonobstructive azoospermic men whose most advanced spermatogenic cells were elongating round spermatids. Nine offsprings from ROSI were reported between 1996 and 2000. No successful deliveries were reported for 15 years after that. Tanaka et al. reported 90 babies born after ROSI and their follow-up studies in 2015 and 2018 showed no significant differences in comparison with those born after natural conception in terms of physical and cognitive abilities. However, clinical outcomes remain low. Method: Clinical and laboratory data of successful cases in the precursor ROSI groups and those of Tanaka et al. were reviewed. Results: Differences were found between the two groups in terms of identification of characteristics of round spermatid and oocyte activation. Additionally, epigenetic abnormalities were identified as underlying causes for poor ROSI results, besides correct identification of round spermatid and adequate oocyte activation. Correction of epigenetic errors could lead to optimal embryonic development. Conclusion: Correction of epigenetic abnormalities has a probability to improve the clinical outcome of ROSI.

The clinical advantage of nasal high-flow in respiratory management during procedural sedation: A scoping review on the application of nasal high-flow during dental procedures with sedation.

Structured summary: Rationale: Nasal high-flow (NHF), a new method for respiratory management during procedural sedation, has greater advantages than conventional nasal therapy with oxygen. However, its clinical relevance for patients undergoing oral maxillofacial surgery and/or dental treatment remains uncertain and controversial, due to a paucity of studies. This scoping review compared and evaluated NHF and conventional nasal therapy with oxygen in patients undergoing oral maxillofacial surgery and/or dental treatment. Materials and methods: A literature search of two public electronic databases was conducted, and English writing randomized controlled trials (RCTs) of nasal high flow during dental procedure with sedation reviewed. The primary and secondary outcomes of interest were the incidence of hypoxemia and hypercapnia during sedation and the need for intervention to relieve upper airway obstruction, respectively. Results: The search strategy yielded 7 studies, of which three RCTs met our eligibility criteria, with a total of 78 patients. Compared with conventional nasal therapy with oxygen, NHF significantly reduced the incidence of hypoxemia and hypercapnia during procedural sedation. Conclusion: NHF can maintain oxygenation and possibly prevent hypercapnia in patients undergoing dental treatment. Additional RCTs are needed to clarify and confirm these findings.

DNA damage in human sperm: The sperm chromosome assay.

Background: Sperm DNA damage is a major cause of pre- and post-implantation embryonic loss in humans. However, the factors that control how and when such DNA damage occurs in human sperm are poorly understood. Methods: Here, I review information relating to sperm DNA damage that can be obtained from the sperm chromosome assays described in the existing literature. Main findings: The sperm chromosome assays, which consist of interspecific in vitro fertilization or intracytoplasmic sperm injection using murine oocytes and subsequent chromosome analysis, indicate that the proportion of sperm showing DNA damage is initially low and there are larger numbers of sperm with potential membrane and DNA damage that are induced after ejaculation and separation from the seminal plasma. Other assays that directly detect sperm DNA (e.g., TUNEL assays, Comet assays, and acridine orange test) are not able to distinguish and detect the initial and potential DNA damage. Furthermore, the positive values in these direct assays are influenced by the frequency of immotile sperm and amorphous sperm populations. Conclusion: The findings in the sperm chromosome assays show that further improvements in sperm preparation protocols may result in the reduction of sperm DNA damage, followed by more successful outcomes in infertility treatment.

De novo heterozygous variants in KIF5B cause kyphomelic dysplasia.

Kyphomelic dysplasia is a heterogeneous group of skeletal dysplasias characterized by severe bowing of the limbs associated with other variable findings, such as narrow thorax and abnormal facies. We searched for the genetic etiology of this disorder. Four individuals diagnosed with kyphomelic dysplasia were enrolled. We performed whole-exome sequencing and evaluated the pathogenicity of the identified variants. All individuals had de novo heterozygous variants in KIF5B encoding kinesin-1 heavy chain: two with c.272A>G:p.(Lys91Arg), one with c.584C>A:p.(Thr195Lys), and the other with c.701G>T:p.(Gly234Val). All variants involved conserved amino acids in or close to the ATPase activity-related motifs in the catalytic motor domain of the KIF5B protein. All individuals had sharp angulation of the femora and humeri, distinctive facial features, and neonatal respiratory distress. Short stature was observed in three individuals. Three developed postnatal osteoporosis with subsequent fractures, two showed brachycephaly, and two were diagnosed with optic atrophy. Our findings suggest that heterozygous KIF5B deleterious variants cause a specific form of kyphomelic dysplasia. Furthermore, alterations in kinesins cause various symptoms known as kinesinopathies, and our findings also extend the phenotypic spectrum of kinesinopathies.

Novel reporters of mitochondria-associated membranes (MAM), MAMtrackers, demonstrate MAM disruption as a common pathological feature in amyotrophic lateral sclerosis.

The mitochondria-associated membrane (MAM) is a functional subdomain of the endoplasmic reticulum membrane that tethers to the mitochondrial outer membrane and is essential for cellular homeostasis. A defect in MAM is involved in various neurological diseases, including amyotrophic lateral sclerosis (ALS). Recently, we and others reported that MAM was disrupted in the models expressing several ALS-linked genes, including SOD1, SIGMAR1, VAPB, TARDBP, and FUS, suggesting that MAM disruption is deeply involved in the pathomechanism of ALS. However, it is still uncertain whether MAM disruption is a common pathology in ALS, mainly due to the absence of a simple, quantitative tool for monitoring the status of MAM. In this study, to examine the effects of various ALS-causative genes on MAM, we created the following two novel MAM reporters: MAMtracker-Luc and MAMtracker-Green. The MAMtrackers could detect MAM disruption caused by suppression of SIGMAR1 or the overexpression of ALS-linked mutant SOD1 in living cells. Moreover, the MAMtrackers have an advantage in their ability to monitor reversible changes in the MAM status induced by nutritional conditions. We used the MAMtrackers with an expression plasmid library of ALS-causative genes and noted that 76% (16/21) of the genes altered MAM integrity. Our results suggest that MAM disruption is a common pathological feature in ALS. Furthermore, we anticipate our MAMtrackers, which are suitable for high-throughput assays, to be valuable tools to understand MAM dynamics.

Involvement of an FNR-like oxygen sensor in Komagataeibacter medellinensis for survival under oxygen depletion.

During acetic acid fermentation, acetic acid bacteria face oxygen depletion stress caused by the vigorous oxidation of ethanol to acetic acid. However, the molecular mechanisms underlying the response to oxygen depletion stress remain largely unknown. Here, we focused on an oxygen-sensing FNR homolog, FnrG, in Komagataeibacter medellinensis. Comparative transcriptomic analysis between the wild-type and fnrG-disrupted strains revealed that FnrG upregulated 8 genes (fold change >3). Recombinant FnrG bound to a specific DNA sequence only when FnrG was reconstituted anaerobically. An operon consisting of acetate kinase and xylulose-5-phosphate/fructose-6-phosphate phosphoketolase genes was found to be an FnrG regulon involved in cell survival under oxygen-limiting conditions. Moreover, a strain that overexpressed these 2 genes accumulated more acetic acid than the wild-type strain harboring an empty vector. Thus, these 2 genes could be new targets for the molecular breeding of acetic acid bacteria with high acetic acid productivity.

Osteocalcin promotes proliferation, differentiation, and survival of PC12 cells.

Involvement of the bone matrix protein osteocalcin (OC) in the development of learning and memory, and the prevention of anxiety-like behaviors in mice. However, the direct effects of OC on neurons are still unknown comparing to the mechanism how OC affects systemic energy expenditure and glucose homeostasis. In this study, we investigated the effect of OC on proliferation, differentiation, and survival of neurons using the rat pheochromocytoma cell line PC12. RT-PCR analysis for OC receptor candidates revealed that Gpr158, but not Gprc6a, mRNA was expressed in PC12 cells. The growth of PC12 cells cultured in the presence of 5-50 ng/mL of either uncarboxylated (GluOC) or carboxylated (GlaOC) OC was increased compared to cells cultured in the absence of OC. In addition, NGF-induced neurite outgrowth was enhanced by OC, and H2O2-induced cell death was suppressed by pretreatment with OC. All of these results were observed for both GluOC and GlaOC at comparable levels, suggesting that OC may directly affect cell proliferation, differentiation, and survival by binding to its candidate receptor, GPR158.

Widespread anorectal lymphovascular networks and tissue drainage: analyses from submucosal India ink injection and indocyanine green fluorescence imaging.

AIM: Abdominoperineal resection is associated with poor prognosis in patients with advanced lower rectal cancer. This study aimed to analyse the functional lymphovascular network and tissue drainage in the anorectal region. METHODS: In this descriptive study, we performed microanatomical evaluations and intra-operative imaging analysis in a cadaver and patients with rectal cancer. Specimens with India ink injection were collected from a cadaver and from six patients who underwent abdominoperineal resection. Intra-operative indocyanine green fluorescence imaging was performed on four patients who underwent surgery for lower rectal cancer. India ink was injected into the submucosa at the dentate line of specimens. Tissue sections were examined by immunohistochemistry for D2-40 and CD31. Intra-operative indocyanine green was injected into the submucosa at the dentate line. Lymph flow was traced using a near-infrared camera system. RESULTS: Fascia branching from the rectal longitudinal muscle layer extended to the posterior hiatal ligament and lateral endopelvic fascia connective tissue lamina on the surface of the levator ani muscle. The fascia contained veins labelled with ink in their lumina and initial lymphatics. Intra-operative indocyanine green fluorescence imaging revealed extensive lymph flow from the muscle layer of the anal canal to the hiatal ligament and endopelvic fascia along the longitudinal muscle layer fibres. CONCLUSIONS: The anorectal region contained widespread venous and lymphatic networks in proportion to its specific connective tissue framework around the longitudinal-muscle-layer-extending muscle bundles, which provides extensive networks for tissue fluid and cells.

Microglial gene signature reveals loss of homeostatic microglia associated with neurodegeneration of Alzheimer's disease.

Microglia-mediated neuroinflammation has been implicated in the pathogenesis of Alzheimer's disease (AD). Although microglia in aging and neurodegenerative disease model mice show a loss of homeostatic phenotype and activation of disease-associated microglia (DAM), a correlation between those phenotypes and the degree of neuronal cell loss has not been clarified. In this study, we performed RNA sequencing of microglia isolated from three representative neurodegenerative mouse models, AppNL-G-F/NL-G-F with amyloid pathology, rTg4510 with tauopathy, and SOD1G93A with motor neuron disease by magnetic activated cell sorting. In parallel, gene expression patterns of the human precuneus with early Alzheimer's change (n = 11) and control brain (n = 14) were also analyzed by RNA sequencing. We found that a substantial reduction of homeostatic microglial genes in rTg4510 and SOD1G93A microglia, whereas DAM genes were uniformly upregulated in all mouse models. The reduction of homeostatic microglial genes was correlated with the degree of neuronal cell loss. In human precuneus with early AD pathology, reduced expression of genes related to microglia- and oligodendrocyte-specific markers was observed, although the expression of DAM genes was not upregulated. Our results implicate a loss of homeostatic microglial function in the progression of AD and other neurodegenerative diseases. Moreover, analyses of human precuneus also suggest loss of microglia and oligodendrocyte functions induced by early amyloid pathology in human.

[Qualitative analysis of provided information and advice from occupational physicians to attending clinical physicians in supporting an employee's work-treatment balance].

OBJECTIVES: In Japan, the population is aging and there is a declining birth rate. It is an important occupational health issue to support the balance between illness treatment (including nursing care, childcare, etc.) and work. Many patients require mental and financial support to help them with their work-treatment balance. In 2016, the Ministry of Health, Labor and Welfare provided guidelines for supporting employee's work-treatment balance, and in 2018, "Consulting Fee" was approved as an insured medical treatment when clinic doctors supported their patients for continuing to work. The request for the consulting fee requires that the clinician and the occupational physician exchange information on the support necessary for the patient to continue working. Generally, occupational physicians obtain medical information from clinicians to give advice on a worker's employment considerations. However, we do not know what kind of workplace information clinicians hope to know when treating their patients. Therefore, we conducted this survey to clarify how occupational physicians could provide useful information to clinicians. METHODS: We asked approximately 1,500 occupational physicians from the Occupational Health Subcommittee of the Japan Society for Occupational Health to provide us with a letter sent to their clinician to assist workers. From the collected letters, the structural parts of the letters (titles, greetings, acknowledgments, etc.) were removed. We defined a section as a contextual unit that does not impair the meaning. The prepared sections underwent qualitative inductive analysis using the content analysis method of "Berelson, B." RESULTS: A total of 103 cases and 178 documents from 42 people were included in the analysis. Extracting descriptions that could be interpreted as providing information, including descriptions related to treatment, employment, and living environment, and opinions and suggestions from occupational physicians resulted in 596 sections. As a result of the qualitative and inductive classification, the information was classified into three large categories that consisted of information provision, opinions of occupational physicians, and information handling, five middle and eighteen small classifications. In addition, some good practices that were considered significant to clinicians were illustrated. CONCLUSIONS: We analyzed and categorized the information present in the letters sent by occupational physicians to clinicians. The letter does not need to contain all the information in the category table. However, it is important that it should have the necessary and sufficient information considering the case in question. We believe that this category table will aid occupational physicians in writing letters to clinicians.