Application of Stem Cell Therapy for ACL Graft Regeneration

Graft regeneration after anterior cruciate ligament (ACL) reconstruction surgery is a complex three-stage process, which usually takes a long duration and often results in fibrous scar tissue formation that exerts a detrimental impact on the patients’ prognosis. Hence, as a regeneration technique, stem cell transplantation has attracted increasing attention. Several different stem cell types have been utilized in animal experiments, and almost all of these have shown good capacity in improving tendon-bone regeneration. Various differentiation inducers have been widely applied together with stem cells to enhance specific lineage differentiation, such as recombinant gene transfection, growth factors, and biomaterials. Among the various different types of stem cells, bone marrow-derived mesenchymal stem cells (BMSCs) have been investigated the most, while ligament stem progenitor cells (LDSCs) have demonstrated the best potential in generating tendon/ligament lineage cells. In the clinic, 4 relevant completed trials have been reported, but only one trial with BMSCs showed improved outcomes, while 5 relevant trials are still in progress. This review describes the process of ACL graft regeneration after implantation and summarizes the current application of stem cells from bench to bedside, as well as discusses future perspectives in this field.

Current Understandings of Myeloid Differentiation Inducers in Leukemia Therapy

Differentiation therapy using all-trans retinoic acid for acute promyelocytic leukemia (APL) is well established. Several attempts have been made to treat non-APL, AML patients by employing differentiation inducers, such as hypomethylating agents (HMAs), and low-dose cytarabine (Ara-C) (LDAC), with encouraging results. Other than HMAs and LDAC, various inducers of myeloid cell differentiation have been identified. This review describes and categorizes these inducers, which include glycosylation modifiers, epigenetic modifiers, vitamin derivatives, cytokines, and chemotherapeutic agents. Some of these inducers are currently being used in clinical trials. I highlight the potential applications of glycosylation modifiers and epigenetic modifiers, which are attracting increasing attention in their use as differentiation therapy against AML. Among the agents described in this review, epigenomic modifiers seem particularly promising, and particular attention should also be paid to glycosylation modifiers. These drugs may signal a new era for AML differentiation therapy.

In Pursuance of Differentiation Inducers to Combat Cancer via Targeting of Abnormal Methylation Enzymes

Cell differentiation agent-2 (CDA-2) was a promising hypomethylating agent approved by the Chinese FDA for the therapy of MDS in China. The active components of CDA-2 are differentiation inducers (DIs) and differentiation helper inducers (DHIs). DIs are chemicals capable of eliminating telomerase from abnormal MEs commonly found in human cancers. The major DI of CDA-2 is an organic acid without UV absorption. Without UV absorption as a guide, it was difficult to purify the DI of CDA-2 for identification. Thus, we pursued possible candidates to function as DIs in this study. Cancer MEs become abnormal due to association with telomerase. Naturally we sought telomerase inhibitors as possible candidates of DIs. Prostaglandin E2 (PGE2) attracted our attention because it was implicated to involve in wound healing, which is a major biological mission of progenitor stem cells (PSCs) and cancer stem cells (CSCs). Eradication of CSCs has been a major focus of our studies. Besides, PGE2 fits the description of the major DI of CDA-2. Induction of terminal differentiation (TD) of HL-60 cells by NBT assay was employed to evaluate the activity of chemicals as DIs. Cell growth was based on cell numbers. All-trans retinoic acid (ATRA) and 12-O-tetradecanoylphorbol-13-acetate (TPA) are two well known DIs. ATRA displayed a wide active dosage range from 0.2 to 4.5 µM with a maximum of inducing 89% NBT+ cells at 3 µM. TPA displayed a narrow active dosage range from 0.2 to 0.6 nM with a maximum of inducing 84% NBT+ cells at 0.4 nM. BIBR1532 and bodine were the two telomerase inhibitors studied. Both were found active as DIs. BIBR1532 was active in the dosage range from 30 to 75 µM with a maximum of inducing 86% at 63 µM. Bodine was active in the dosage range from 60 to 98 µM with a maximum of inducing 80% at 98 µM. PGE2 was active in the dosage range from 20 to 70 µM with a maximum of inducing 80% at 56 µM. DIs at dosages not active as DIs could function as effective DHIs to other DIs. RI0.5 of BIBR1532, boldine and PGE2 as DHIs were 2.02 µM, 3.11 µM, and 0.92 µM, respectively. DIs alone, no matter how effective, could not induce NBT+ cells to reach 100%. 95% (89% plus 6% of blank) was the highest value achieved by ATRA. Incomplete induction of TD was the reason for frequent recurrence when ATRA was used alone in the therapy of acute promyelocytic leukemia (APL). A combination of ATRA and a DHI could induce NBT+ cells to reach 100% to avoid recurrence.