Aging decreases bone marrow cellularity and alters the frequencies of stem cells.
This is not surprising since we modeled our score after the assessment of bone marrow cellularity, which is a practice that is widely-accepted clinically and highly reproducible between pathologists5.
In the group of myeloproliferative neoplasm, unclassifiable patients with a primary myelofibrosis-like morphology, the overall bone marrow cellularity resulted increased in most of the cases (85%), without a significant hyperplasia of the granulopoietic series.
The score was intended to be relatively straightforward, and similar to the estimation of bone marrow cellularity on core biopsies, which has high inter-observer reproducibility5 and is a familiar task to many pathologists.
In the human hematopoietic system, aging is associated with decreased bone marrow cellularity, decreased adaptive immune system function, and increased incidence of anemia and other hematological disorders and malignancies.
However, some morphological features such as increased bone marrow cellularity, alteration in the myeloid to erythroid ratio, increased number of megakaryocytes with abnormal nuclear features and clustering, together with the presence in more than half of the cases of a significant increase in bone marrow fibrosis, confirmed a diagnosis of myeloproliferative neoplasm in all the patients.
The abnormal lymphocytes comprised ∼ 30% of the bone marrow cellularity with interstitial infiltrates/aggregates.
In vivo leukemia cell kill (LCK) was calculated by comparing bone marrow cellularity and percent leukemic blasts in marrow obtained before and 5 days after treatment with a single dose of asparaginase.
Blood and lymphoid tissues were evaluated for morphologic, cellular, and molecular responses.Irradiated animals developed symptoms of acute hematopoietic syndrome, and reductions in thymus weight, thymopoiesis, and bone marrow cellularity.
Seventeen patients had isolated thrombocytopenia (< 100 x 109 platelets/L): the marrow cellularity was normal in five patients and slightly reduced in 12, and there was no discrepancy between thrombopoiesis and myeloerythropoiesis.
