Ultrastructural Pathology, 2014; 38(4): 256–260 ! Informa Healthcare USA, Inc. ISSN: 0191-3123 print / 1521-0758 online DOI: 10.3109/01913123.2014.888116
ORIGINAL ARTICLE
Activation of Monocyte-Derived Cells in the Bone Marrow of Myelodysplastic Syndrome Yongxin Ru, MD1, Shuxu Dong, BSc1, Huamei Zhang, BSc1, Shixuan Zhao, BSc1, Kun Ru, 1 1 1 2 MD , Guoguang Zheng, PhD , Zhijie Xiao, MD , and Brian Eyden, PhD 1
State Key Laboratory of Experimental Haematology, Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin, China and 2Department of Histopathology, Christie Hospital NHS Trust, Manchester, UK
ABSTRACT Object: To study the relationship between monocyte/histiocyte activation and myelodysplastic syndrome (MDS). Methods: Analyzing ultrastructure and myeloperoxidase reaction of nucleated cells in bone marrow from 59 cases of MDS by transmission electron microscopy. Four groups of MDS were subdivided on the basis of their content of activated inflammatory cells – morbid hematopoiesis with minimal inflammatory cell activation (MH-MICA); MDS with monocytic system activation (MSA); MDS with lymphocyte activation (LCA); and MDS with granulocyte activation (GCA). Results: About 20, 22, 7, and 10 cases were classified as MH-MICA (34%), MSA (37%), LCA (12%), and GCA sub-types (17%), respectively. About 3, 5, 0, and 3 cases from MH-MICA, MSA, LCA, and GCA, respectively, underwent leukemic transformation within 2 years. Conclusion: The findings suggest that activation of inflammatory cells in bone marrow is an important feature of MDS, and that monocytes/histocytes are perhaps the most prominent cellular participants in the pathogenesis of MDS. Keywords: Bone marrow, inflammatory cell, monocyte, myelodysplastic syndrome
macrophages, dendritic cells, hemophagocytes, and variant histiocytes have been described recently in the bone marrow of patients with certain hematological diseases [3,4]. Myelodysplastic syndrome (MDS), known as a clonal malignant hematological disease, was characterized by a decrease in blood cell numbers and potential leukemic transformation, but its causative factors and pathogenesis remain to be clarified. This study details the cellular characteristics using transmission electron microscopy (TEM) of the monocytes, macrophages, dendritic cells, reticular cells, and atypical histocytes in the bone marrow of a large cohort of MDS patients, with the objective of furthering our knowledge and understanding of the roles of these cells in the pathogenesis of MDS.
Cells of the monocytic lineage, including monocytes and the various macrophages with distinctive functions and morphology, are conservative in biological origin and evolution. All of them are derived from monocytic progenitors and collectively known as the ‘‘monocytic system’’ and ‘‘mononuclear phagocyte system’’ (MPS) because of their property of phagocytosis. From the 1960s, different macrophages, such as Langerhans cells and Kupffer’s cells, were identified in skin, liver, spleen, lung, intestine, and other connective tissues, while dendritic macrophages were identified in spleen, lymph node and thymus. These macrophages were also referred to as resident macrophages or histocytes because of their location in tissues and their association with specific diseases [1,2]. Activated monocytes,
Received 17 January 2014; Accepted 23 January 2014; Published online 28 February 2014 Correspondence: Dr. Yongxin Ru, Department of Pathology, Institute of Hematology & Blood Diseases Hospital, Peking Union College, 288 Nanjing Road, Tianjin 300020, China. Tel: +86 22 27309061. E-mail: [email protected]
256
Monocyte-Derived Cells in Myelodysplastic Syndrome
CLINICAL DATA
257
ultrastructural characteristics (Table 1). Four groups of patients with MDS were categorized on the basis of the following criteria. Morbid Hematopoiesis with Minimal Inflammatory Cell Activation (MH-MICA): here, more than 10% of NCs have abnormal structures, but there is no increase in the number of monocyte-derived cells, lymphocytes, or granulocytes. Monocytic system activation (MSA): the number of monocyte-derived cells is more than 8% of NCs, and any sub-type of monocyte-derived cell (macrophage, hemophagocyte, dendritic cell, reticular cell, or atypical histiocyte) accounts for more than 5% of NCs. Lymphocyte activation (LCA): lymphocytes account for more than 40% of NCs. Granulocyte activation (GCA): the number of activated granulocytes (i.e., eosinophils, basophils, and neutrophils with large and coarse granules referred as ‘‘toxic’’ granules) is more than 40% of NCs, in the absence of LCA.
About 59 patients, 43 males and 16 females, aged from 1 to 85 years, were diagnosed as MDS on the basis of morphology, cytochemistry, flow cytometry, molecular biology, and TEM in bone marrow biopsy. The clinical presentations included cytopenia, anemia, hemorrhage, and infectious symptoms. Of the 59 cases, in addition to disease within the bone marrow, four had hepatosplenomegaly, five had lymphadenopathy, 18 had chromosome abnormalities, and nine were positive for the marker, multidrug resistance-1 (MDR-1). About 11 of 59 cases underwent a complete transformation to leukemia within 2 years – five cases into acute monocytic leukemia (M5), two cases into acute erythroid leukemia (M6), and one case each into acute myelomonocytic leukemia (M4), chronic myelogenous leukemia (CML), acute promyelocytic leukemia (M3), and acute myeloid leukemia with maturation (M2).
RESULTS METHODS Qualitative Observations Electron Microscopy Ample Preparation Monocytes, macrophages, hemophagocytes, dendritic cells, reticular cells, and atypical histocytes in the bone marrow of MDS patients exhibited distinctive ultrastructural characteristics (Table 1). Monocytes were often smaller than other monocyte-derived cells, showing more processes, vesicles, and regularly shaped lysosomes; in terms of nuclear features, they showed a twisted nucleus with moderately clumped heterochromatin and inconspicuous nucleoli (Figure 1A). Macrophages had large protrusions harboring ingested cellular debris, large irregular lysosomes, and plenty of vacuoles in the cytoplasm (Figure 1B). Hemophagocytes were the largest of the monocyte-derived cells, containing more whole red blood cells in the cytoplasm (Figure 1C), some of them presumably recently phagocytosed. Dendritic cells had slender processes and contained small secretory vesicles, dense granules, and unexpanded profiles of
Nucleated cells (NCs) were isolated from bone marrow aspirates, half of them processed for ultrastructural observation and half incubated for myeloperoxidase (MPO) activity [5]. The TEM procedure of fixation, dehydration, embedding, sectioning, and staining was as previously described [6].
Observational and Grouping Criteria About 200 NCs in ‘‘morphological’’ ultrathin sections and 200 in ‘‘MPO’’ ultrathin sections, respectively, were observed. Cells of monocyte lineage, such as monocytes themselves, macrophages, hemophagocytes, dendritic cells, reticular cells, and atypical histiocytes, as well as lymphocytes and granulocytes, were identified and enumerated based on their TABLE 1. Ultrastructure of cells of the monocyte lineage in MDS. Characteristics
MC
MP
HPC
DC
Diameter (mm) Nucleus
9–12 Single indented
15–50 Single irregular
15–50 Single irregular
15–40 Single irregular
NCR Granules Golgi body Vesicles Processes Phagocytosis Engulfed cell
51/2 Small Large, more Small, many More microvilli Little Seldom
51/2 Coarse Large, few Coarse Long protrusions Prominent Debris
51/4 Coarse Large, few Coarse, more Short protrusions Prominent Entire cell
51/2 Small, fewer Large, more Small, less Long protrusions Little Seldom
RC
AHC
20–100 One or more irregular 51/3 Small, fewer Large, few More Long network Encircling cells Entire cell
12–20 One or more round 1/1 1/2 Large, few Small, few Coarse, few Few Occasional Entire cell
MC, monocyte; MP, macrophage; HPC, hemophagocyte; DC, dendritic cell; RC, reticular histiocyte; AHC, atypical histocyte; NCR, nucleo-cytoplasmic ratio. !
2014 Informa Healthcare USA, Inc.
258 Y. Ru et al.
FIGURE 1. (A) An active monocyte with irregular nucleus, small lysosomes, vacuoles in the cytoplasm and cell-surface processes, 6000. (B) Two macrophages (arrow) containing secondary lysosomes and cellular debris, 5000. (C) A hemophagocyte having engulfed red blood cells (RC) and naked nuclei (NN), 4000. (D) Dendritic cell with mitochondria (arrowhead) and rough endoplasmic reticulum (arrows) (insert), 5000.
rough endoplasmic reticulum (rER) in the peripheral cytoplasm (Figure 1D). Reticular histiocytes-containing small, round lysosomes, formed a cellular network and entrapped various kinds of blood cells (Figure 2A and B). Some reticular histiocytes were in contact with each other, forming an extensive meshwork. Atypical histiocytes exhibited immature features, including rounded nuclei with lesser amounts of heterochromatin and prominent nucleoli, and plenty of cytoplasm with few surface processes (Figure 2C and D). Most granulocytes and erythroid cells exhibited abnormal characteristics, usually megaloblastic changes, nuclear abnormalities, nuclear/cytoplasm asynchrony, and apoptotic features. Additionally, erythroblasts showed the features of cytoplasmic
fragmentation and mitochondrial iron deposition. Granulocytes illustrated abnormalities of primary and secondary granules and a deviation from normal numbers. The granule deficiencies were usually associated with a dilation of rER in granulocytes. Small megakaryocytes with mature structures and abnormal platelets were occasionally found [7].
Quantitative Observations According to the grouping criteria already stated and the numbers of cells identified by a range of qualitative features described above, all the 59 cases of MDS distributed themselves into 20, 22, 7, and 10 cases of MH-MICA, MSA, LCA, and GCA, Ultrastructural Pathology
Monocyte-Derived Cells in Myelodysplastic Syndrome
259
FIGURE 2. (A) A reticular histiocyte (RC) capturing a lymphocyte (Lc) and a erythroblast (Eb), 3000. (B) Reticular histiocyte (RC) encircling a lymphocyte (Lc) and a plasma cell (Pc) (MP, macrophage), 3000. (C) An atypical histiocyte showing an irregular nucleus with prominent nucleolus (arrow) vacuoles in cytoplasm, 5000. (D) A large atypical histiocyte with multiple nuclear profiles and prominent nucleoli (arrows), 4000.
respectively. Table 2 illustrates cellular compositions of a single representative case of each of the four MDS sub-groups. The occurrence of infection, hepatosplenomegaly, lymphadenopathy, chromosomal abnormalities, MDR-1, and leukemic transformation was not significantly different among the four groups (Table 3).
DISCUSSION AND CONCLUSION Monocyte-derived cells are a heterogeneous group which includes macrophages, dendritic cells, hemophagocytes, and reticular histiocytes, and their presence and numbers characterize different diseases. These cells are also referred to as ‘‘mononuclear !
2014 Informa Healthcare USA, Inc.
phagocytes and immunoregulatory effectors’’ (M-PIRE), on account of their immunological regulation and oncological surveillance by phagocytosis and antigen presentation [8]. Monocytes and macrophages usually amount to less than 8% in bone marrow and peripheral blood under physiological conditions, but hemophagocytes, dendritic cells, reticular, and atypical histiocytes are often found in increased numbers in hemophagocytic syndrome [9], aplastic anemia [3], and connective tissue disease involving bone marrow [10]. Therefore, these cells are to be regarded as reactive and pathogenic cells in various hematological conditions. In the present study, the 59 cases of MDS had varying degrees of abnormal characteristics of hematopoiesis, and the presence of apoptotic figures; 39 of
260 Y. Ru et al. TABLE 2. A representative case from each of the MDS sub-groups illustrating cellular composition (% of 200 NCs). Cell-type MDS sub-group MC MP HPC DC RC AHC AG LC MH-MICA MSA LCA GCA
4 6 3 2
2 3 1 2
0 4 0 0
0 3 1 1
0 5 1 0
0 2 0 0
10 13 8 50
24 10 45 15
MC, monocyte; MP, macrophage; HPC, hemophagocyte; DC, dendritic cell; RC, reticular histiocyte; AHC, atypical histocyte; AG, activated granulocyte; LC, lymphocyte; MH-MICA, morbid hematopoiesis with minimal inflammatory cell activation; MSA, monocytic system activation; LCA, lymphocyte activation; GCA, granulocyte activation.
Cases Infection Hepatomegaly Splenomegaly Lymphadenopathy CA MDR positive LT
DECLARATION OF INTEREST This work was supported by Grants 81370634 from the National Natural Science Foundation of China (NSFC).
REFERENCES
TABLE 3. Sub-types of the 59 cases of MDS with clinical presentations. Groups
significant feature of bone marrow inflammation in patients with MDS. In conclusion, the study has provided evidence that about two-thirds of MDS patients were complicated with activation of inflammatory cells in bone marrow, and it is proposed that activated monocyte-derived cells play a significant role in the pathogenesis of MDS.
MH-MICA*
MSA
LCA
GCA
Total
20 9/20 2/20 2/20 3/20 6/13 2/20 3/20
22 4/22 2/22 2/22 3/22 6/18 4/20 5/22
7 3/7 0/7 0/7 1/7 4/7 0/7 0/7
10 2/10 0/10 0/10 2/10 2/9 3/10 3/10
59 18/59 4/59 4/59 8/59 18/48 9/57 11/59
*MH-MICA, morbid hematopoiesis with minimal inflammatory cell activation; MSA, monocytic system activation; LCA, lymphocyte activation; GCA, granulocyte activation; CA, chromosomal abnormality; LT, leukemic transformation.
them were complicated by increased numbers of monocyte-derived cells, lymphocytes, or granulocytes (66%) in bone marrow. The result was consistent with previous clinical reports suggesting that MDS is associated at least partially with inflammation of bone marrow [11,12]. There are two reasonable explanations and presumptions. First: chronic inflammation could exist previously, and lead to MDS as a late stage of development of the disease. This would be consistent with Niller‘s case report on MDS developing from a Leptospira infection [13]. Second: the inflammation may result from massive apoptosis and the death of blood cells in the bone marrow of MDS. The finding that 56% of MDS had increased numbers of monocyte-derived cells, that 18% had increased numbers of lymphocytes, that 26% had increased numbers of granulocytes, and that 11 of the 59 cases of MDS transformed into leukemia and five of these (45%) were of the MSA type – the more preponderant of all the other subtypes – all suggest that activation of monocyte-derived cells is a
1. Wiseman BK. The origin of the white blood cell. J Am Med Assoc 1934;103: 1523. 2. Cline MJ. The white cell. Cambridge, MA: Harvard University, 1975:459. 3. Ru YX, Zhu XF, Gao JT, et al. Ultrastructural characteristics of nucleated cells in bone marrow of patients with acquired aplastic anemia. Ultrastruct Pathol 2008;32: 81–8. 4. Ru YX, Bao ST, Dong SX, et al. Analysis of monocyte and histiocytic cell populations in bone marrow of patients with confirmed and suspected cases of reactive histocytosis. Ultrastruct Pathol 2013;37: 93–101. 5. Roels F, Wisse E, Brest BDE, Meulen J. Cytochemical discrimination between catalases and peroxidases using diaminobenzidine. Histochemistry 1975;41: 281–312. 6. Ru YX, Wang HJ, Yang BX, et al. The ultrastructure of hybrid acute leukemia: A study of 15 cases. Ultrastruct Pathol 2005;29: 341–7. 7. Zhang HM, Liu JH, Zhao SX, et al. Correlation between ultrastructural abnormality of bone marrow cells and anemia and neutropenia in myelodysplastic syndrome. Zhongguo Shi Yan Xue Ye Xue Za Zhi 2011;19: 81–4. 8. Foucar K, Foucar E. The mononuclear phagocyte and immunoregulatory effector (M-PIRE) system: Evolving concepts. Semin Diagn Pathol 1990;7: 4–18. 9. Janka GE, Schenider EM. Modern management of children with haemophagocytic lymphohistiocytosis. Br J Haematol 2004;124: 4–14. 10. Henter JI, Elinder G, Soder O, et al. Incidence in Sweden and clinical features of familial hemophagocytic lymphohistiocytosis. Acta Paediatr Scand 1991;80: 428–35. 11. Imashuku S, Kitazawa K, Ishii M, et al. Bone marrow changes mimicking myelodysplasia in patients with hemophagocytic lymphohistiocytosis. Int J Hematol 2000; 72: 353–7. 12. Toma A, Fenaux P, Dreyfus F, Cordonnier C. Infections in myelodysplastic syndromes. Haematologica 2012;97: 1459–70. 13. Niller HH. Myelodysplastic syndrome (MDS) as a late stage of subclinical hemophagocytic lymphohistiocytosis (HLH): A putative role for Leptospira infection. A hypothesis. Acta Microbiol Immunol Hung 2010;57: 181–9.
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ORIGINAL ARTICLE
Activation of Monocyte-Derived Cells in the Bone Marrow of Myelodysplastic Syndrome Yongxin Ru, MD1, Shuxu Dong, BSc1, Huamei Zhang, BSc1, Shixuan Zhao, BSc1, Kun Ru, 1 1 1 2 MD , Guoguang Zheng, PhD , Zhijie Xiao, MD , and Brian Eyden, PhD 1
State Key Laboratory of Experimental Haematology, Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin, China and 2Department of Histopathology, Christie Hospital NHS Trust, Manchester, UK
ABSTRACT Object: To study the relationship between monocyte/histiocyte activation and myelodysplastic syndrome (MDS). Methods: Analyzing ultrastructure and myeloperoxidase reaction of nucleated cells in bone marrow from 59 cases of MDS by transmission electron microscopy. Four groups of MDS were subdivided on the basis of their content of activated inflammatory cells – morbid hematopoiesis with minimal inflammatory cell activation (MH-MICA); MDS with monocytic system activation (MSA); MDS with lymphocyte activation (LCA); and MDS with granulocyte activation (GCA). Results: About 20, 22, 7, and 10 cases were classified as MH-MICA (34%), MSA (37%), LCA (12%), and GCA sub-types (17%), respectively. About 3, 5, 0, and 3 cases from MH-MICA, MSA, LCA, and GCA, respectively, underwent leukemic transformation within 2 years. Conclusion: The findings suggest that activation of inflammatory cells in bone marrow is an important feature of MDS, and that monocytes/histocytes are perhaps the most prominent cellular participants in the pathogenesis of MDS. Keywords: Bone marrow, inflammatory cell, monocyte, myelodysplastic syndrome
macrophages, dendritic cells, hemophagocytes, and variant histiocytes have been described recently in the bone marrow of patients with certain hematological diseases [3,4]. Myelodysplastic syndrome (MDS), known as a clonal malignant hematological disease, was characterized by a decrease in blood cell numbers and potential leukemic transformation, but its causative factors and pathogenesis remain to be clarified. This study details the cellular characteristics using transmission electron microscopy (TEM) of the monocytes, macrophages, dendritic cells, reticular cells, and atypical histocytes in the bone marrow of a large cohort of MDS patients, with the objective of furthering our knowledge and understanding of the roles of these cells in the pathogenesis of MDS.
Cells of the monocytic lineage, including monocytes and the various macrophages with distinctive functions and morphology, are conservative in biological origin and evolution. All of them are derived from monocytic progenitors and collectively known as the ‘‘monocytic system’’ and ‘‘mononuclear phagocyte system’’ (MPS) because of their property of phagocytosis. From the 1960s, different macrophages, such as Langerhans cells and Kupffer’s cells, were identified in skin, liver, spleen, lung, intestine, and other connective tissues, while dendritic macrophages were identified in spleen, lymph node and thymus. These macrophages were also referred to as resident macrophages or histocytes because of their location in tissues and their association with specific diseases [1,2]. Activated monocytes,
Received 17 January 2014; Accepted 23 January 2014; Published online 28 February 2014 Correspondence: Dr. Yongxin Ru, Department of Pathology, Institute of Hematology & Blood Diseases Hospital, Peking Union College, 288 Nanjing Road, Tianjin 300020, China. Tel: +86 22 27309061. E-mail: [email protected]
256
Monocyte-Derived Cells in Myelodysplastic Syndrome
CLINICAL DATA
257
ultrastructural characteristics (Table 1). Four groups of patients with MDS were categorized on the basis of the following criteria. Morbid Hematopoiesis with Minimal Inflammatory Cell Activation (MH-MICA): here, more than 10% of NCs have abnormal structures, but there is no increase in the number of monocyte-derived cells, lymphocytes, or granulocytes. Monocytic system activation (MSA): the number of monocyte-derived cells is more than 8% of NCs, and any sub-type of monocyte-derived cell (macrophage, hemophagocyte, dendritic cell, reticular cell, or atypical histiocyte) accounts for more than 5% of NCs. Lymphocyte activation (LCA): lymphocytes account for more than 40% of NCs. Granulocyte activation (GCA): the number of activated granulocytes (i.e., eosinophils, basophils, and neutrophils with large and coarse granules referred as ‘‘toxic’’ granules) is more than 40% of NCs, in the absence of LCA.
About 59 patients, 43 males and 16 females, aged from 1 to 85 years, were diagnosed as MDS on the basis of morphology, cytochemistry, flow cytometry, molecular biology, and TEM in bone marrow biopsy. The clinical presentations included cytopenia, anemia, hemorrhage, and infectious symptoms. Of the 59 cases, in addition to disease within the bone marrow, four had hepatosplenomegaly, five had lymphadenopathy, 18 had chromosome abnormalities, and nine were positive for the marker, multidrug resistance-1 (MDR-1). About 11 of 59 cases underwent a complete transformation to leukemia within 2 years – five cases into acute monocytic leukemia (M5), two cases into acute erythroid leukemia (M6), and one case each into acute myelomonocytic leukemia (M4), chronic myelogenous leukemia (CML), acute promyelocytic leukemia (M3), and acute myeloid leukemia with maturation (M2).
RESULTS METHODS Qualitative Observations Electron Microscopy Ample Preparation Monocytes, macrophages, hemophagocytes, dendritic cells, reticular cells, and atypical histocytes in the bone marrow of MDS patients exhibited distinctive ultrastructural characteristics (Table 1). Monocytes were often smaller than other monocyte-derived cells, showing more processes, vesicles, and regularly shaped lysosomes; in terms of nuclear features, they showed a twisted nucleus with moderately clumped heterochromatin and inconspicuous nucleoli (Figure 1A). Macrophages had large protrusions harboring ingested cellular debris, large irregular lysosomes, and plenty of vacuoles in the cytoplasm (Figure 1B). Hemophagocytes were the largest of the monocyte-derived cells, containing more whole red blood cells in the cytoplasm (Figure 1C), some of them presumably recently phagocytosed. Dendritic cells had slender processes and contained small secretory vesicles, dense granules, and unexpanded profiles of
Nucleated cells (NCs) were isolated from bone marrow aspirates, half of them processed for ultrastructural observation and half incubated for myeloperoxidase (MPO) activity [5]. The TEM procedure of fixation, dehydration, embedding, sectioning, and staining was as previously described [6].
Observational and Grouping Criteria About 200 NCs in ‘‘morphological’’ ultrathin sections and 200 in ‘‘MPO’’ ultrathin sections, respectively, were observed. Cells of monocyte lineage, such as monocytes themselves, macrophages, hemophagocytes, dendritic cells, reticular cells, and atypical histiocytes, as well as lymphocytes and granulocytes, were identified and enumerated based on their TABLE 1. Ultrastructure of cells of the monocyte lineage in MDS. Characteristics
MC
MP
HPC
DC
Diameter (mm) Nucleus
9–12 Single indented
15–50 Single irregular
15–50 Single irregular
15–40 Single irregular
NCR Granules Golgi body Vesicles Processes Phagocytosis Engulfed cell
51/2 Small Large, more Small, many More microvilli Little Seldom
51/2 Coarse Large, few Coarse Long protrusions Prominent Debris
51/4 Coarse Large, few Coarse, more Short protrusions Prominent Entire cell
51/2 Small, fewer Large, more Small, less Long protrusions Little Seldom
RC
AHC
20–100 One or more irregular 51/3 Small, fewer Large, few More Long network Encircling cells Entire cell
12–20 One or more round 1/1 1/2 Large, few Small, few Coarse, few Few Occasional Entire cell
MC, monocyte; MP, macrophage; HPC, hemophagocyte; DC, dendritic cell; RC, reticular histiocyte; AHC, atypical histocyte; NCR, nucleo-cytoplasmic ratio. !
2014 Informa Healthcare USA, Inc.
258 Y. Ru et al.
FIGURE 1. (A) An active monocyte with irregular nucleus, small lysosomes, vacuoles in the cytoplasm and cell-surface processes, 6000. (B) Two macrophages (arrow) containing secondary lysosomes and cellular debris, 5000. (C) A hemophagocyte having engulfed red blood cells (RC) and naked nuclei (NN), 4000. (D) Dendritic cell with mitochondria (arrowhead) and rough endoplasmic reticulum (arrows) (insert), 5000.
rough endoplasmic reticulum (rER) in the peripheral cytoplasm (Figure 1D). Reticular histiocytes-containing small, round lysosomes, formed a cellular network and entrapped various kinds of blood cells (Figure 2A and B). Some reticular histiocytes were in contact with each other, forming an extensive meshwork. Atypical histiocytes exhibited immature features, including rounded nuclei with lesser amounts of heterochromatin and prominent nucleoli, and plenty of cytoplasm with few surface processes (Figure 2C and D). Most granulocytes and erythroid cells exhibited abnormal characteristics, usually megaloblastic changes, nuclear abnormalities, nuclear/cytoplasm asynchrony, and apoptotic features. Additionally, erythroblasts showed the features of cytoplasmic
fragmentation and mitochondrial iron deposition. Granulocytes illustrated abnormalities of primary and secondary granules and a deviation from normal numbers. The granule deficiencies were usually associated with a dilation of rER in granulocytes. Small megakaryocytes with mature structures and abnormal platelets were occasionally found [7].
Quantitative Observations According to the grouping criteria already stated and the numbers of cells identified by a range of qualitative features described above, all the 59 cases of MDS distributed themselves into 20, 22, 7, and 10 cases of MH-MICA, MSA, LCA, and GCA, Ultrastructural Pathology
Monocyte-Derived Cells in Myelodysplastic Syndrome
259
FIGURE 2. (A) A reticular histiocyte (RC) capturing a lymphocyte (Lc) and a erythroblast (Eb), 3000. (B) Reticular histiocyte (RC) encircling a lymphocyte (Lc) and a plasma cell (Pc) (MP, macrophage), 3000. (C) An atypical histiocyte showing an irregular nucleus with prominent nucleolus (arrow) vacuoles in cytoplasm, 5000. (D) A large atypical histiocyte with multiple nuclear profiles and prominent nucleoli (arrows), 4000.
respectively. Table 2 illustrates cellular compositions of a single representative case of each of the four MDS sub-groups. The occurrence of infection, hepatosplenomegaly, lymphadenopathy, chromosomal abnormalities, MDR-1, and leukemic transformation was not significantly different among the four groups (Table 3).
DISCUSSION AND CONCLUSION Monocyte-derived cells are a heterogeneous group which includes macrophages, dendritic cells, hemophagocytes, and reticular histiocytes, and their presence and numbers characterize different diseases. These cells are also referred to as ‘‘mononuclear !
2014 Informa Healthcare USA, Inc.
phagocytes and immunoregulatory effectors’’ (M-PIRE), on account of their immunological regulation and oncological surveillance by phagocytosis and antigen presentation [8]. Monocytes and macrophages usually amount to less than 8% in bone marrow and peripheral blood under physiological conditions, but hemophagocytes, dendritic cells, reticular, and atypical histiocytes are often found in increased numbers in hemophagocytic syndrome [9], aplastic anemia [3], and connective tissue disease involving bone marrow [10]. Therefore, these cells are to be regarded as reactive and pathogenic cells in various hematological conditions. In the present study, the 59 cases of MDS had varying degrees of abnormal characteristics of hematopoiesis, and the presence of apoptotic figures; 39 of
260 Y. Ru et al. TABLE 2. A representative case from each of the MDS sub-groups illustrating cellular composition (% of 200 NCs). Cell-type MDS sub-group MC MP HPC DC RC AHC AG LC MH-MICA MSA LCA GCA
4 6 3 2
2 3 1 2
0 4 0 0
0 3 1 1
0 5 1 0
0 2 0 0
10 13 8 50
24 10 45 15
MC, monocyte; MP, macrophage; HPC, hemophagocyte; DC, dendritic cell; RC, reticular histiocyte; AHC, atypical histocyte; AG, activated granulocyte; LC, lymphocyte; MH-MICA, morbid hematopoiesis with minimal inflammatory cell activation; MSA, monocytic system activation; LCA, lymphocyte activation; GCA, granulocyte activation.
Cases Infection Hepatomegaly Splenomegaly Lymphadenopathy CA MDR positive LT
DECLARATION OF INTEREST This work was supported by Grants 81370634 from the National Natural Science Foundation of China (NSFC).
REFERENCES
TABLE 3. Sub-types of the 59 cases of MDS with clinical presentations. Groups
significant feature of bone marrow inflammation in patients with MDS. In conclusion, the study has provided evidence that about two-thirds of MDS patients were complicated with activation of inflammatory cells in bone marrow, and it is proposed that activated monocyte-derived cells play a significant role in the pathogenesis of MDS.
MH-MICA*
MSA
LCA
GCA
Total
20 9/20 2/20 2/20 3/20 6/13 2/20 3/20
22 4/22 2/22 2/22 3/22 6/18 4/20 5/22
7 3/7 0/7 0/7 1/7 4/7 0/7 0/7
10 2/10 0/10 0/10 2/10 2/9 3/10 3/10
59 18/59 4/59 4/59 8/59 18/48 9/57 11/59
*MH-MICA, morbid hematopoiesis with minimal inflammatory cell activation; MSA, monocytic system activation; LCA, lymphocyte activation; GCA, granulocyte activation; CA, chromosomal abnormality; LT, leukemic transformation.
them were complicated by increased numbers of monocyte-derived cells, lymphocytes, or granulocytes (66%) in bone marrow. The result was consistent with previous clinical reports suggesting that MDS is associated at least partially with inflammation of bone marrow [11,12]. There are two reasonable explanations and presumptions. First: chronic inflammation could exist previously, and lead to MDS as a late stage of development of the disease. This would be consistent with Niller‘s case report on MDS developing from a Leptospira infection [13]. Second: the inflammation may result from massive apoptosis and the death of blood cells in the bone marrow of MDS. The finding that 56% of MDS had increased numbers of monocyte-derived cells, that 18% had increased numbers of lymphocytes, that 26% had increased numbers of granulocytes, and that 11 of the 59 cases of MDS transformed into leukemia and five of these (45%) were of the MSA type – the more preponderant of all the other subtypes – all suggest that activation of monocyte-derived cells is a
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