Degenerative musculoskeletal disorders are one of the top causes of pain and disability in the adult population. Current available alternatives to mitigate symptoms include conservative treatments such as the administration of pharmacological agents and an educative approach towards lifestyle modification. The use of certain analgesics, such as opiates and corticosteroids, delivers short term results but do not address the etiological source of pain and disability. Also, prolonged use of such medications may cause additional complications. Therefore, the demand for musculoskeletal tissue regeneration has led to an alternative approach referred to as "orthobiologics". This alternative is based on cellular and molecular components capable of inducing and promoting tissue repair. Bone marrow (BM) aspirate (BMA) and concentrate are well-known orthobiologics used to treat musculoskeletal conditions. Orthobiologics derived from the BM have been discussed in the literature; however, the lack of standardization regarding collection and processing protocols presents a challenge for generalization of study outcomes and determination of efficacy. Since BM-derived orthobiologics have not yet been classified, to our knowledge, this manuscript proposes the ACH classification system, which speaks to BMA (A), BMA and concentrate (C) and hybrid (H), which combines A and C. This classification proposes and describes 8 parameters that are relevant for the quality of biological products. The more parameters used would imply greater characterization and complexity of the evaluation of the biological product used. The ACH classification envisages a necessary contribution to the comprehension of both clinical procedures and research outcomes, ultimately ushering in a standardization of best practice.

In recent years the therapeutic application of extracted adipose tissue for autologous fat grafting and the application of adipose tissue-derived mesenchymal stem cells (adMSC) isolated thereof has progressed. Water-jet assisted liposuction (WAL) is 1 procedure for harvesting adipose tissue and provides a favorable aesthetic outcome combined with high tissue protection. Tissue aspirated by WAL has been successfully applied in grafting procedures.

The aims of this study were to confirm the tissue viability and to understand the abundance and mesenchymal differentiation capacity of stem cells within the tissue.

We analyzed tissue integrity of WAL tissue particles via fluorescence microscopy. The adMSC content was determined by isolating the cells from the tissue. The mesenchymal differentiation capacity was confirmed with cytochemical staining methods.

The stromal vascular fraction of WAL tissue showed high viability and contained an average of 2.6 × 105 CD34-positive cells per milliliter of tissue. Thus WAL tissue contains a high number of stem cells. Furthermore adMSC isolated from WAL tissue showed typical mesenchymal differentiation potential.

WAL of adipose tissue is well suited for autologous fat grafting because it retains tissue viability. Furthermore it is a valid source for the subsequent isolation of adMSC with multipotent differentiation potential.

3 Therapeutic.

The in vitro radiation sensitivity of CFU-Meg isolated from human placental and umbilical cord blood was evaluated in plasma clot cultures stimulated by recombinant human cytokines, including thrombopoietin, the FLT3 ligand (FLT3LG), interleukin-3, interleukin-11 and stem cell factor. The CD34(+) cells were irradiated with X rays at a dose rate of 73 cGy/ min. The megakaryocyte colonies were identified by using an FITC-conjugated antibody to glycoprotein IIbIIIa and were classified into two groups based on colony size: large colonies (immature CFU-Meg) and small colonies (mature CFU-Meg). Treatment with thrombopoietin alone or in combination with FLT3LG and/or interleukin-11 gave exponential radiation survival curves (D(0) for immature CFU-Meg = 56-77 cGy, D(0) for mature CFU-Meg = 86 cGy-1.12 Gy), while marked shoulders were observed on the survival curves for colonies supported by the combination of thrombopoietin, interleukin-3 and stem cell factor (D(0) for immature CFU-Meg = 89- 98 cGy; D(0) for mature CFU-Meg = 1. 25-1.31 Gy). Our results showed that the immature CFU-Meg were more radiosensitive than the mature CFU-Meg and that the combination of cytokines, including thrombopoietin, interleukin-3 and stem cell factor, affected the radiation sensitivity of CFU-Meg to the same extent as with thrombopoietin alone or in combination with FLT3LG and/or interleukin-11.